SYNTHESES AND CHARACTERIZATION OF
ARYL XANTHATES OF GROUP 12TH
ELEMENTS
THESIS
SUBMITTED TO THE UNIVERSITY OF JAMMU
FOR THE DEGREE OF
DOCTRATE OF PHILOSOPHY
IN
CHEMISTRY
BY
NIDHI KALGOTRA
UNDER SUPERVISION OF
Prof. SUSHIL K. PANDEY
DEPARTMENT OF CHEMISTRY
UNIVERSITY OF JAMMU
JAMMU- 180 006 (J&K)
JULY-2014
P. G. DEPARTMENT OF CHEMISTRY
UNIVERSITY OF JAMMU,
JAMMU, 180 006
CERTIFICATE
This is to certify that Ms. Nidhi Kalgotra, a registered candidate in the P. G.
Department of Chemistry, University of Jammu, Jammu, for the award of Degree
of Doctor of Philosophy under my supervision, has completed her thesis entitled
“SYNTHESES AND CHARACTERIZATION OF ARYL XANTHATES OF
GROUP 12TH ELEMENTS”. The work is worthy of consideration for the award of
Degree of Doctor of Philosophy in Chemistry and has not been submitted in part
or in full for any other degree or diploma in this or any other university.
I further certified that:
i)
the thesis embodies the work of the candidate herself;
ii) the candidate worked under my supervision for the period required under
statutes of the university;
iii) the candidate has put in the required attendance in the department and
remained good during this period of research and
iv) the candidate has fulfilled the statutory conditions as laid down in Section
18.
Dated:
Prof. Sushil K. Pandey
Supervisor
Dedicated to my son
“Siddhanth”
ACKNOWLEDGEMENTS
The present achievement of my academic career would not have been possible
without the blessings of Almighty God and my Family. I dedicate this
accomplishment to them. In completing this piece of work, apart from my own labour,
there is enormous contribution from many people without whom this work would not
have taken the present form.
First of all, I would like to genuinely acknowledge my advisor, Prof. S. K.
Pandey, for his enlightening guidance and support, who has been a tremendous
mentor for me. I would like to thank him for encouraging my research and for
allowing me to grow as a research scientist. His advice on both research as well as
on my career have been priceless.
I am extremely grateful to Prof. Renu Sachar, Head, Department of
Chemistry, University of Jammu, Jammu, for ensuring cordial atmosphere in the
Department and providing me all sorts of facilities during my research work.
I would like to express my deepest appreciation to all those who provided me
the possibility to complete this report. A special gratitude I give to Mrs. Bhawana,
whose contribution in stimulating suggestions and encouragement, helped me to
coordinate my project especially in writing this thesis. I am also thankful to all my
seniors research colleagues, friends and fellow colleagues, Dr. Deepak Kumar,
Dr. Mohita, Mrs. Atiya, Ms. Ruchi, Ms. Mehak, Mrs. Gurpreet, Mrs. Mandeep and
Mr. Sandeep for their cooperation, affection and moral support throughout my
research work.
I acknowledge my sincere thanks to Mrs. Savit Andotra, (Research Assistant
NMR lab), University of Jammu, for providing spectral studies and also help in
biological Study. I acknowledge my thanks to Indian Institute of Integrative Medicine,
Jammu and owe my special thanks to Mr. Avtar Singh, SAIF (Sophisticated and
Analytical Instrumentation Facility), University of Panjab, Chandigarh for providing
spectral studies and other facilities without which task would have not been
accomplished.
i
Words fail me to express my appreciation to my husband Dr. Anil Khokhar
whose dedication, love, inspiration, moral support and persistent confidence in me
has been a source of motivation for my accomplishments.
A special thanks to my family. Words cannot express how grateful I am to my
mother-in law Smt. Kailash and father-in-law Sh. J. N. Khokhar, for their sincere
encouragement and inspiration throughout my research work and lifting me uphill
this phase of life.
Last but not least, I would like to pay high regards to my mother Mrs. Sunita
and father Mr. G. L. Kalgotra for all of the sacrifices they have made on my behalf. I
am extremely beholden with deepest sense of gratitude towards them who showed me
the right path of life and light me the good things that really matter in my life. The
work couldn’t have been possible without blessings, love, affection, inspiration,
encouragement and moral support rendered to me from them. It is due to the
blessings of my parents that I am able to fulfil this work in time. This thesis is simply
impossible without them.
I have no words to express my deepest appreciation to my beloved son
Siddhanth and sister Megha.
I also considerable thanks to my sister Mrs. Meenu and my brother-in-law
Mr. Naresh
for their friendliness, moral support and encouragement during my
work.
Finally, I would like to thank everybody who was important to the successful
realization of this thesis, as well as expressing my apology that I could not mention
personally one by one. To all of them I say “THANKS” from the core of my heart.
Dated:
Nidhi Kalgotra
ii
TABLE OF CONTENTS
CONTENTS
CHAPTER I~INTRODUCTION
1.1:
PAGE No.
1-48
PREFACE
1-4
RELEVANT CHEMISTRY OF SULFUR BONDED
5-7
COMPOUNDS
1.1.1:
Thiolates and Dithiolates
7-14
1.1.2:
Thiocarboxylates
14-19
1.1.3:
Dithiocarbamates
20-29
1.1.4:
Dithiophosphates
29-38
1.1.5:
Dithiocarbonates
38-46
1.2:
SCOPE AND OBJECTIVE
47-48
CHAPTER II~EXPERIMENTAL
2.1:
GENERAL PROCEDURES AND EXPERIMENTAL
49-78
49
TECHNIQUES
2.1.1:
Apparatus
49
2.1.2:
Materials
49
2.1.3:
Analytical Methods
53-55
2.1.4:
Instrumental Methods
56-57
2.2:
SYNTHESES OF LIGANDS
58-60
2.2.1:
Synthesis of o-CH3C6H5OCS2Na
58
2.2.2:
Synthesis of neopentylenedithiophosphate ligand
58
2.3:
SYNTHESES OF NEW COMPOUNDS
61-66
2.3.1:
Synthesis of [(o-CH3C6H4OCS2)2]
61
2.3.2:
Synthesis of [(o-CH3C6H4OCS2)2Zn]
61
2.3.3:
Synthesis of
62
2.3.4:
[(o-CH3C6H4OCS2) Zn(S2POCH2C(CH3)2CH2O)]
Synthesis of Adducts
67-73
2.3.4.1: Synthesis of [(o-CH3C6H4OCS2)2Zn.2NC5H5]
67
2.3.4.2: Synthesis of [(o-CH3C6H4OCS2)2Cd.2P(C6H5)3]
67
2.3.4.3: Synthesis of [(o-CH3C6H4OCS2)2Hg.N2C12H8]
68
2.4:
BIOLOGICAL ACTIVITY
74-78
2.4.1:
Antifungal activity
74-75
2.4.2:
Antibacterial activity
75-77
2.4.3:
Cytotoxicity
77-78
CHAPTER III~RESULTS AND DISCUSSION
3.0:
(ortho-, meta- and para-TOLYL)/BENZYL
79-221
79
DITHIOCARBONATES OF ZINC(II),
CADMIUM(II) AND MERCURY(II)
SECTION~I
3.1:
GENERAL
80
3.2:
(ortho–, meta– and para–tolyl)/benzyl dithiocarbonate
81
ligands (1-4)
3.3:
Sodium O,O’-neopentylenephosphorodithioate ligand
84
(5)
3.4:
3.5:
Disulfides of (ortho–, meta– and para–tolyl)/benzyl
dithiocarbonates
(6-9)
Dithiocarbonate derivatives of zinc(II), cadmium(II)
92-102
103
and mercury(II)
3.5.1:
Bis[(ortho-, meta and para-tolyl)/benzyl dithiocarbonates]
of zinc(II), cadmium(II) and mercury(II) (10-21)
104-126
3.5.2:
Mixed dithiocarbonato–dithiophosphato complexes of
zinc(II), cadmium(II) and mercury(II) (22-33)
127-151
3.6:
Adducts of bis-[(ortho–, meta– and para–tolyl)/benzyl
dithiocarbonates] of zinc(II), cadmium(II) and
mercury(II) with nitrogen and phosphorus donors (34-81)
152-198
SECTION~II
3.7:
BIOLOGICAL ACTIVITY
199-227
3.7.1:
Antifungal activity
202-215
3.7.2:
Antibacterial activity
215-225
3.7.3:
Cytotoxicity analysis
226-227
CHAPTER IV~SUMMARY AND REFERNCES
228-265
SUMMARY
228-246
REFERENCES
247-265
List of Publications
ABBREVIATIONS
Bdmppy
2,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)pyridine
Bdt
Benzenedithioate
Bipy
2,2’-bipyridine
Bix
1,4-bis(imidazole-1-ylmethyl)-benzene
Bppy
2,6-bis(pyrazd-3-yl)pyridine
Bpyrm
2,2'-bipyrimidine
Bu
Butyl
Bz-
Benzyl
C.N.
Coordination number
CDCl3
Deuterated chloroform
cm-1
Wave number
Cp
Cyclopentadienyl
CV
Cyclic voltammetry
DFT
Density functional theory
Dec.
Decompose
DMF
Dimethylforaamide
Dmid
2-oxo-1,3-dithiole-4,5-dithiolate
Dmit
Dithiolene
DMSO
Dimethylsulfoxide
Dpyam
2,2’-dipyridylamine
Dtp
Dithiophosphate
EPR
Electron paramagnetic resonance
Et
Ethyl
i
FAB
Fast electron bombardment
FT-IR
Fourior Transform infrared spectroscopy
gm
gram
H2dmit
4,5-dimercapto-l,3-dithiol-2-thione
Hdmpz
3,5-dimethylpyrazole
pz
Pyrazole
hrs
hours
i-Pr-
iso-propyl
IR
Infrared
K
Kelvin
kj
Kilojoule
Lut
3,5-dimethylpyridine (lutidine)
m/z
Mass to charge ratio
MHz
Mega hertz
mm
Millimetre
mnt
Maleonitriledithiolate
MOCVD
Metal organic chemical vapour deposition
Mol
Mole
neo-Pent-
neo-pentane
NMR
Nuclear magnetic resonance
Ph
Phenyl
Phen
1,10-phenanthroline
phpyam
Phenyl 2-pyridylamine
pic
2-methylpyridine
pm
Picometer, 10-12m
ii
ppm
Parts per million
PPh3
Triphenylphosphine
Py
Pyridine
pyam
2-pyridylamine
pyr
1,4-pyrazine
SRB
sulforhodamine B
tabH
4-(trimethylammonio)benzenethiol
TDDFT
Time dependent density functional theory
th
Thiophene
tmdp
4,4-trimethylenebipyridine
TGA
Thermogravimetric analysis
TMS
Trimethylsilane
TOPO
tri-n-octylphosphine oxide
UV-vis
Ultraviolet visible
v
Frequency
MLCT
Metal-to-ligand charge-transfer
[M+]
Molecular ion
mins.
minutes
2,9-dmphen
2,9-dimethyl-1,10-phenanthroline
2-mpipdtc
2-methylpiperidinecarbodithioate
4,4’-bpe
trans-1,2-bis(4-pyridyl)ethane
4,4’-bpy
4,4’-bipyridine
XRD
X-ray diffraction
EDS
Electronic Data System
NBO
Natural bond orbital
iii
LIST OF TABLES
PAGE
NO.
Table
No.
2.1:
Synthetic and analytical data of sodium salt of (ortho-, meta- and
para-tolyl)/benzyldithiocarbonates (1-4) and neopentylene dithiophosphate (5)
59
2.2:
Synthetic and analytical data of disulfides of (ortho–, meta– and
para–tolyl)/benzylthiocarbonate ligands (6-9)
60
2.3:
Synthetic and analytical data of (ortho-, meta- and para-tolyl)/
benzyldithiocarbonates of zinc(II), cadmium(II)
and mercury(II) (10-21)
63-64
2.4:
Synthetic and analytical data of mixed dithiocarbonate and
dithiophosphate complexes of zinc(II), cadmium(II) and
mercury(II) (22-33)
65-66
2.5:
Synthetic and analytical data of adducts of (ortho–, meta– and para
tolyl)/benzyldithiocarbonates of zinc(II), cadmium(II) and
mercury(II) with nitrogen and phosphorus donor ligands (34-81)
69-73
3.1:
IR spectral data of (ortho, meta– and para–tolyl)/benzyl
dithiocarbonate ligands (1–4) and neopentylene ligand (5) in
cm–1
88
3.2:
1
H and 31P NMR spectral data of (ortho–, meta– and para–
tolyl)/benzyl dithiocarbonate ligands (1–4) and neopentylene
ligand (5) in DMSO (in ppm)
89
3.3:
13
C NMR spectral data of (ortho–, meta– and para–tolyl)/benzyl
dithiocarbonate ligands (1–4) and neopentylene ligand (5) in
DMSO (in ppm)
90
Mass spectroscopic data of (ortho–, meta– and para–
tolyl)/benzyl dithiocarbonate ligands (1–4)
91
3.4:
3.5:
IR spectral data of disulfides of (ortho–, meta– and para–
tolyl)/benzyl dithiocarbonate ligands (6-9) in cm–1
98
3.6:
1
99
3.7:
13
C NMR spectral data of disulfides of (ortho–, meta– and para–
tolyl)/benzyl dithiocarbonate ligands (6-9) in CDCl3 (in ppm)
100
3.8:
Mass spectral data of disulfides of (ortho–tolyl)/benzyl
dithiocarbonate ligands (6-9)
101
3.9:
IR spectral data of (ortho–, meta– and para–tolyl)/benzyl
dithiocarbonates of zinc(II), cadmium(II) and mercury(II) (10–
21) (in cm–1)
116
3.10:
1
117
3.11:
13
C NMR spectral data of (ortho–, meta– and para–tolyl)/benzyl
dithiocarbonates of zinc(II), cadmium(II) and mercury(II) (10–
21) in CDCl3 (in ppm)
118
3.12:
Mass spectral data of (ortho–, meta– and para–tolyl)/benzyl
dithiocarbonates of zinc(II), cadmium(II) and mercury(II) (10–
21)
119
3.13:
IR spectral data of mixed dithiocarbonato–dithiophosphato 136-137
derivatives of zinc(II), cadmium(II) and mercury(II) (22-33) (in
cm-1)
3.14:
1
H NMR spectral data of disulfides of (ortho–, meta– and para–
tolyl)/benzyl dithiocarbonate ligands (6-9) in CDCl3 (in ppm)
H NMR spectral data of (ortho–, meta– and para–tolyl)/benzyl
dithiocarbonates of zinc(II), cadmium(II) and mercury(II) (10–
21) in CDCl3 (in ppm)
H NMR and 31P NMR spectral data of mixed dithiocarbonato– 138-139
dithiophosphato derivatives of zinc(II), cadmium(II) and
mercury(II) (22-33) CDCl3 (in ppm)
13
3.15:
C NMR spectral data of mixed dithiocarbonato–
dithiophosphato derivatives of zinc(II), cadmium(II) and
mercury(II) (22-33) in CDCl3 (in ppm)
140
3.16:
Mass spectral data of some mixed dithiocarbonato–
dithiophosphato derivatives of zinc(II), cadmium(II) and
mercury(II) (22-33)
141
3.17:
IR spectral data of (ortho–, meta– and para–tolyl)/benzyl 165-167
dithiocarbonates of zinc(II), cadmium(II) and mercury(II) with
nitrogen and phosphorus donor ligands (34-81) (in cm–1)
3.18:
1
H and 31P NMR spectral data of of (ortho–, meta– and para– 168-174
tolyl)/benzyl dithiocarbonates of zinc(II), cadmium(II) and
mercury(II) with nitrogen and phosphorus donor ligands (34-81)
in CDCl3 (in ppm)
3.19:
13
3.20:
Mass spectral data of some of (ortho–, meta– and para–
tolyl)/benzyl dithiocarbonates of zinc(II), cadmium(II) and
mercury(II) with nitrogen and phosphorus donor ligands
180-183
3.21:
In vitro evaluation of sodium salt of tolyl/benzyl
dithiocarbonates, their disulfides and zinc complexes against the
fungus Fusarium oxysporum f. Sp. Capsici.
208
3.22:
In vitro evaluation of cadmium, mercury salts and their
complexes with dithiocarbonates against fungus Fusarium
oxysporum f. Sp. Capsici.
209
3.23:
Morphological and medicinal characteristics of the microbial
isolates
217
3.24:
In vitro evaluation of zinc(II) complexes for antibacterial activity
218
3.25:
In vitro evaluation of dithiocarbonate ligand and its zinc(II)
complexes for Cytotoxicity activity
227
C NMR spectral data of of (ortho–, meta– and para– 175-179
tolyl)/benzyl dithiocarbonates of zinc(II), cadmium(II) and
mercury(II) with nitrogen and phosphorus donor ligands (34-81)
in CDCl3 (in ppm)
INTRODUCTION
PREFACE
The present thesis deals with the synthesis and characterization of new (ortho-, metaand para-tolyl)/benzyl dithiocarbonate ligands and probing efficient method for the
synthesis of these new ligands. During the present course of investigations, eightyone new compounds have been synthesized and characterized. The biological activitiy
(antibacterial and antifungal) of twenty eight and cytotoxicity of few compounds have
been tested. The new complexes synthesized during the present course of
investigations are corresponding to the general formula [(ArOCS2)2M] (Ar = o–, m–,
p–CH3C6H4– and C6H5CH2–; and M = Zn, Cd and Hg). The thesis also describes the
synthesis and characterization of the disulfides [ArOCS2]2 of these ligands. Adducts
of the metal complexes with nitrogen and phosphorus donor ligands corresponded to
[(ArOCS2)2M.nL] (n = 1, L = C12H8N2, C10H8N2; n = 2, L = P(C6H5)3 and C5H5N) are
also been reported herein. All these compounds have been characterized by using
various
physico–chemical
techniques
like
elemental
analysis,
mass,
thermogravimetric analysis, infra red, cyclic voltammetry, SEM and heteronuclear
NMR (1H,
13
C and
31
P) spectroscopic studies. In general, these compounds may be
described to possess C–S–M linkages. The newly synthesized complexes during the
present course of investigations provide help to understand the different structural and
biological properties of group 12th metals with sulfur donor ligands.
Group 12, by modern IUPAC numbering,1 is a group of chemical element in
the periodic table. It includes zinc (Zn), cadmium (Cd) and mercury (Hg). Group 12 is
also known as the volatile metals, although this can also more generally refer to any
metal that has high volatility. Formerly this group was named IIB (pronounced as
"group two B", as the "II" is a Roman numeral) by CAS and old IUPAC system. The
valence shell electronic configuration of these elements is (n-1)d10ns2.
The electronic configuration of these elements is as:
Element
Atomic no.
Electronic configuration
Zn
30
[Ar] 3d104s2
Cd
48
[Kr] 4d105s2
Hg
80
[Xe] 4f145d106s2
1
INTRODUCTION
Some important physical properties of these elements are given below in the table:
Table 1: Some important physical properties of the elements
Properties
Zinc
Cadmium
Mercury
Atomic Number
30
48
80
Atomic Weight
65.38
112.41
200.5
Atomic radii (pm)
125
141
144
Ionic radii (pm)
74
95
102
Co-ordination Number
4
4
4
Electro negativity
1.6
1.7
1.9
Density at 20 C
7.1
8.6
13.5
Oxidation State
+2, +1, 0
+2, +1
+4, +2, +1
The three group 12 elements that occur naturally are zinc, cadmium and
mercury. They are all widely used in electric and electronic applications, as well as in
various alloys.2 The first two members of the group share similar properties as they
are solid metals under standard conditions. Mercury is the only metal that is a liquid at
room temperature. While zinc is very important in the biochemistry of living
organisms, cadmium and mercury are both highly toxic. Like in most other d-block
groups, the abundance in Earth's crust of group 12 elements decreases with higher
atomic number. Zinc is with 65 parts per million (ppm), the most abundant in the
group, while cadmium with 0.1 ppm and mercury with 0.08 ppm are orders of
magnitude less abundant.3 Zinc is the twenty fourth most abundant elements in the
earth’s crust and is an essential element in the life processes.4 The adult human body
contains about 2-3 g of zinc which is generally in the form of enzymes.
Group 12 metals are chalcophiles, meaning the elements have low affinities
for oxides and prefer to bond with sulfides. Chalcophiles formed as the crust
solidified under the reducing conditions of the early Earth's atmosphere.5 The
commercially most important minerals of group 12th elements are sulfide
minerals. Sphalerite, which is a form of zinc sulfide, is the most heavily mined zinccontaining ore because its concentrate contains 60–62% zinc.6 No significant deposits
2
INTRODUCTION
of
cadmium-containing
ores
are
known
Greenockite (CdS),
the
only
cadmium mineral of importance, is nearly always associated with sphalerite
(ZnS). Although mercury is an extremely rare element in the Earth's crust.7
The common oxidation state of these elements is +2 but there have also been
the theoretical arguments that mercury in +4 oxidation state might exist e.g. in HgF4.8
The only deviation from the strict divalence are the M22+ ions, of which only Hg22+ is
stable under normal conditions. Although the formation of complexes with ammonia,
amines, halides and pseudo halide ions are reminiscent of transition metal ion
behaviour, the ability of the group 12th elements to serve as d donors is so low that
they form none of the other typical sorts of transition metal complexes such as
carbonyls, nitrosyls or -complexes with olefins. Although the preferred coordination
environment around zinc, cadmium and mercury complexes is 4 and 6, yet their
complexes also exhibit interesting structural variations. The display of variety of
coordination numbers and geometries is due to interplay of electrostatic forces,
covalence and the size factor. In addition to common coordination numbers 4 and 6, a
linear 2-coordination number has also been observed which is attributed to relativistic
effect on 6s orbital.9
Zinc is available in the human body in the form of enzymes and
metallothionine proteins. Biochemists were somewhat slow to appreciate the presence
and importance of zinc because it is colorless, non-magnetic and generally not easily
detectable. However, today there are effective methods available for measuring zinc
at levels as low as 10-14 gram.10 In 1940’s carbonic anhydrase was shown to be a zinc
enzyme and in 1955’s carboxy-peptidase become the second recognized enzyme.
Since then more than 300 other enzymes of zinc are known including alcohol
dehydrogenase, aldolases, peptidases, carboxy peptidases, protease, phosphates,
transphosphorylases, DNA and RNA– polymerases.11 In order to understand the role
of zinc enzymes in the biological process, a large number of model compounds have
been reported in the literature,10-12 Zinc complexes also find applications as catalysts13
in rubber industry, as oil additives14 and fungicides.15-16
Most of the complexes of these elements in +2 oxidation state exhibit
tetrahedral or distorted tetrahedral geometry while a few complexes shows 3, 5 and 6
coordination17-24 in the same oxidation states. Zinc, however, is one of the important
3
INTRODUCTION
metal in life processes and is of great biological importance but cadmium and
mercury have demonstrated toxicity as their only biochemical function. It is
remarkably in contrast that where zinc is biologically active metal, cadmium and
mercury are biologically inactive and cadmium is extremely toxic25 and accumulates
in human body mainly in kidneys and liver prolonged intake, even of very small
amounts, leads to dysfunction of the kidneys. It acts by binding to the –SH group of
the cysteine residues in proteins and so inhibits –SH enzymes. It can also inhibit the
action of zinc enzymes by displacing the zinc. Organomercury compounds were used
in late 19th century in medicine and continue to be used to a certain extent. The toxic
effects of organomercury compounds led to their early use in medicine e.g.
merurochrome and merthiolate are used as skin antiseptic agents. Various
preparations containing aryl derivatives of heavy metals in soaps, creams, liquids,
mouthwashes etc. can be used for the treatment of skin or mouth infections.26 Such
compounds, typified by phenylmercuric borate, are used exclusively for external
application and can be quite poisonous if taken internally. Organo derivatives of
heavy metals can deactivate enzymes by binding to their active sites. The reverse is
also occasionally true; certain organomercurials are known to activate enzymes.27
The enormous concern arising from Minamata disease (1972) stimulated
considerable research into the biological activity of methyl mercuric compounds.
This, in turn, has resulted in the use of CH3HgCl as an investigative tool. Numerous
reports are available on cytotoxicological studies, methylmercuric chloride being most
commonly employed. Organomercurials have been used for the investigation of cell
division.28 An unusual organomercurial is tetrakis-(acetoxymercury)methane binds
readily to coat proteins of bacteriophages and makes an excellent imaging agent for
electron microscopy.29
Despite exciting applications in synthetic and polymer chemistry, the
chemistry of the Group 12th elements remained poorly understood with the sulfur
bonded tolyl/benzyl dithiocarbonate ligands within the scientific community. The
small number of well characterized target compounds prevents a detailed structure
function analysis. Further, progress critically depends on the development of reliable
and facile synthetic regimen and the introduction of novel ligand systems to achieve
improved understanding and utility of the many applications.
4
INTRODUCTION
1.1: RELEVANT CHEMISTRY OF SULFUR BONDED COMPLEXES
Metallic derivatives of ROCS2- ligands have been known since 1815 when these were
first prepared by W.C. Zeise, 30 who also termed them xanthates, a name derived from
the Greek xanthos (yellow), owing to the yellow color of lead xanthates.31 Xanthates
of alkali metals, sodium and potassium in particular, are very widely employed as
reagents in the selective separation of sulfide minerals by the method of froth
floatation and have been used in industries as flotation agents for thiophilic minerals
of the transition metals such as copper, zinc, cobalt, gold and nickel.32-35 The
potassium amyl xanthates are also used as mineral collectors.36 The literature on
mineral dressing contains many references37-39 to the use of xanthates for flotation.
Zinc-isopropyl and -butylxanthates have been used as an accelerator in the
vulcanization of rubber.40-43 It is also used in the protection of rubber against
atmospheric gases, especially oxygen and ozone.44-45 Dixanthogens have been used
for regulation of the molecular weight of styrene-butadiene rubber. The regulating
efficiency of a series of dixanthogens has been studied by Vaclavek.46 Heavy metal
xanthates are used as catalysts in the polymerization of olefins e.g. zinc
isopropylxanthate.47-48 Diisopropyl dixanthogen has also been used as a catalyst in the
polymerization of xanthates.49 Xanthates and xanthic acid esters have been used as
weed killers. Mixtures of sodium or potassium and ammonium xanthates mixed with
manganese, zinc or iron salts are effective pesticides. The methyl ester of
propylxanthic acid has been described as an effective insecticide.50 Xanthate
complexes of tin have demonstrated potential activity as anti-tumor agents.51 Some
phosphine-gold(I)dithiocarbonate complexes have proved to possess anti-arthritic
activity.52 N-alkyl pyridinium xanthates have been found to be efficient as corrosion
inhibitors for steel in acid solutions.53 Xanthates have been extensively employed as
reagents in chemical analysis for the separation and quantitative determination of
transition metals and for the analysis of alcohols and carbon disulfide by their
quantitative conversion to xanthates.50 Alkali metal xanthates could be used as
reagents for group separation in quantitative analysis and several advantages were
claimed for xanthates over hydrogen sulfide.54 Xanthates have -CS2 group which
makes them more reactive towards various metals. Malik et al. developed a direct
method for the spectrophotometric determination of microamounts of Co(II), Ni(II),
5
INTRODUCTION
Cu(II), Pd(II), Ru(III) and Mo(VI) using sodium isoamylxanthate as a reagent in the
presence of surfactant as solubilising agent in various alloys and in environmental
samples (fly ash).55
Cellulose xanthates find extensive application in the textile industry in the
production of rayon.56 Cuprous xanthate and cellulose dixanthate exhibits
bacteriostatic and bactericidal properties.57 However, copper or iron salts of cellulose
xanthic acid are used for germination and initial growth of the plants.58 Dibutyl
dixanthogen is used as a constituent of a fire proofing agent for self-extinguishing
resins.50 Isopropyl, butyl, amyl and nonyl dixanthogens possess good antiseize
properties and are used as additives in lubricating oil.59 Insoluble cellulose xanthate
and O-alkyldithiocarbonate of cellulose was used for the removal of heavy metal ions
from aqueous solutions.60 Xanthic acids have been known to act as reducing agents.
Recently, D609, a tricyclodecanol derivative of xanthic acid, has been reported to
have anti-poptotic and anti–inflammatory properties that are attributed to specific
inhibition of phosphatidyl choline phospholipase C (PC-PLC).61 Various DNA and
RNA species are inhibited by xanthate compounds at concentrations that leave the
mitotic activity of uninfected cells unimpaired.62 Alkali xanthates are widely used in
the extraction and separation of mercury, silver etc.63 Sodium and potassium ethyl
xanthate have antidotal effects in acute mercurial poisoning.63b The transition metal
xanthate complexes have been investigated for nonlinear optical applications.63a
Extensive studies have been carried out for a long time on Oalkyldithiocarbonate (alkylxanthates) as ligands with several transition metals64-70 and
main group elements.71-72 Various bonding modes of these ligands with several metals
have been established in which these behaved as monodenate,73-74 bidentate75 and
chelating ligands.76-77 These are known to form chelate complexes with virtually all
the transition elements and have proved to be a versatile chelating agents for the
separation and extraction of metals in the analytical chemistry and mineral floating.7879
The synthesis of arylxanthates of nickel [Ni(S2COC6H4-4-t-Bu)2]
and cobalt
[Co(S2COC6H2-2,4,6-Me3)3] have recently been reported.80 Most of the early
investigation of these systems, performed several decades ago, were centered around
the use of sulfur ligands as an analytical reagents but interest in the synthesis and
characterization of these ligands has increased because of their potential biological
activity81-82 and practical applications in the field as diverse as rubber technology, 83-84
6
INTRODUCTION
agriculture85-86 or electronics.87-88 Divalent transition metals 1,1-dithiolates are partly
unsaturated and can therefore form 1:1 adduct with electron donors such as neutral
nitrogen, oxygen, phosphorus or sulfur donor ligands in which the coordination
geometry ranges from square pyramidal to trigonal bipyramidal.89
The present thesis deals mainly with the complexes of zinc, cadmium and
mercury with sulfur containing ligands, therefore, it is relevant to present a brief
coverage of the literature background with emphasis on the synthetic and structural
aspect of the above mentioned subject. This introductory part has been divided into
the following subsections:
1.1.1: THIOLATES AND DITHIOLATES
1.1.2: THIOCARBOXYLATES
1.1.3: DITHIOCARBAMATES
1.1.4: DITHIOPHOSPHATES
1.1.5: DITHIOCARBONATES (XANTHATES)
1.1.1: THIOLATES AND DITHIOLATES
The chemistry of group 12 metal thiolate coordination is vital to an understanding of
the interactions of these metals in biological systems. Zinc and cadmium thiolate
complexes90 have been used as models for thiolate metalloproteins such as
metallothione, which are located in the kidney and liver in a wide variety of animals,
including man. These proteins bind various metallic cations such as zinc, cadmium,
mercury, and copper through thiolate ligands and regulate the levels of these heavy
metals in the organism.91
Mononuclear and tetranuclear zinc benzenethiolate complexes are studied by
both spectroscopic and electrochemical methods. Zn(SPh)42-
and Zn4(SPh)102-
represent tetrahedral fragments of the cubic zinc sulfide lattice. The mononuclear
complex does not emit, while the tetranuclear compound displays a short-lived metalto-ligand charge-transfer (MLCT) emission.91
Zinc and cadmium bis(alkyl) thiolate compounds are available readily by
the reaction of the appropriate metal acetate with the desired thiol in ethanol.
7
INTRODUCTION
M(OOCCH3)2.nH2O + 2RSH
M = Zn, Cd;
M(SR)2 + 2CH3COOH
R = iPr, tBu, Bz
These compounds decompose when heated to a temperature of about 200 C.
The weight loss determined by thermo-gravimetric analysis corresponds to the
formation of metal sulfide.
Mercury chlorothiolate compound can be obtained by the reaction of
mercury dichloride and the appropriate thiol in ethanol.
HgCl2
+ RSH
ClHgSR + HCl
R = iPr, nPent, Bz, -CPh3
i
Pr-, nPent- and Bz- derivatives have been isolated and characterized by single
crystal X-ray diffraction while the triphenylmethyl derivative is not stable and
decomposes in a period of minutes to form a black precipitate.92
As d10 metals, Zn2+ and Cd2+ form flexible coordination environments and
their coordination geometry varies from tetrahedral to octahedral geometry.93 Using
4-methylbenzenethiolates of Zn or Cd as precursors and 4,4’-bipyridyl as bridges,
three
new
Zn(II)
and
Cd(II)
coordination
polymers,
{[Cd(4,4’-
bipy)2(NCS)2]2(SC6H4CH3-4)2}n (1), {[Zn(4,4’-bipy)(SC6H4CH3-4)2].DMF}n (2) and
{[Zn(4,4’-bipy)(SC6H4CH3-4)2].H2O.0.5CH3OH}n (3). Different coordination mode
and packing scheme (Figure 1.1) shows that the guest molecule has a critical
influence on formation of polymers.94 The above complexes have been synthesized by
following reaction as in Scheme1.1.
M(SPhMe-4) + NH2CSNH2
+ 4,4'-bipy + L
150 oC,
{Cd(4,4'-bipy)2(NCS)2(SPhMe-4)2}n
4 days
CH3OH
{[Zn(4,4'-bipy)(SPhMe-4)2].DMF}n
4-6 weeks
4-6 weeks
M = Cd, Zn;
{[Zn(4,4'-bipy)(SPhMe-4)2].H2O.0.5CH3OH}n
L = CH3CN (1), DMF (2), DMF/CS2 (3)
Scheme 1.1: Synthetic procedure of Zn(II) and Cd(II) coordination polymer
8
INTRODUCTION
Figure 1.1: Coordination environment of Cd in {[Cd(4,4’-bipy)2(NCS)2]2
(SC6H4CH3-4)2}n
Kuzuya et al.95 has reported the synthesis of zinc sulfide nanocrystals (NCs)
via formation of polymetallic thiolate cages. Nearly monodisperse ZnS NCs with size
ranging from 2.2 to 7.0 nm were obtained by thermolysis of S-Zn-dodecanethiol
precursors. TEM observation and UV-vis spectra reveal that the growth rate of ZnS
NCs considerably depends on the annealing temperature.95
The Cd(II)-thiolates are generally synthesized by combination of the metal salt
and ligand in common organic solvents. An electrochemical synthetic methodology is
often used for heterocyclic thiones, as well as mixed compounds such as bipyridyl,
phenanthroline and pyridine. In the case of simple thiols, salt metathesis is generally
used.96
Cadmium thiolates, Cd(SCH2CH(OH)CH2OH)2 were prepared by using
Cd(ClO4)2.6H2O and thioglycerol were dissolved in deionized water. The solution
was adjusted to pH 11.2 using 1 M NaOH and dialyzed two times against
deionized, the pH value of the solution slowly decreased and colorless crystals grow
in the dialysis tubings as flat tetragonal bipyramids.97 The crystal structure is best
described as a framework built up of covalently linked Cd8(SR)16 units which belong
to the pointgroup S4 (Figure 1.2). The temperature dependency of the
113
Cd-NMR
spectrum of a 1 M solution of Cd(SCH2CH(OH)CH2OH)2 in DMSO displayed a
broad signal between 400 and 600 ppm (2200 Hz) at room temperature while with
increasing temperature this signal changed into a sharp peak at 515 ppm (260 Hz at T
= 383 K).
9
INTRODUCTION
Figure 1.2: Structure of the Cd8(SR)I6 units
Reactions
of
Cd(NO3)2·4H2O
with
TabHPF6
(TabH
=
4-
(trimethylammonio)benzenethiol) and Et3N in the presence of NH4SCN and five other
N-donor ligands such as 2,2’-bipyridyl (2,2’-bipy), 1,10-phenanthroline (phen), 2,9dimethyl-1,10-phenanthroline (2,9-dmphen), 2,6-bis(pyrazd-3-yl)pyridine (bppy) and
2,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)pyridine (bdmppy) gave rise to a family of
Cd(II)thiolate complexes of N-donor ligands, {[Cd2(m-Tab)4(NCS)2](NO3)2·MeOH}n
(1), [Cd2(m-Tab)2(L)4](PF6)4 (2, L = 2,2’-bipy; 3, L = phen), [Cd(Tab)2(L)](PF6)2 (4,
L = 2,9-dmphen; 5, L=bppy)
and [Cd2(m-Tab)2(Tab)2(bdmppy)]2(PF6)8·H2O (6).
These compounds were characterized by elemental analysis, IR spectra, UV-vis
spectra, 1H NMR, electrospray ionization (ESI) mass spectra and single-crystal X-ray
crystals98 are given in Figure 1.3.
Figure 1.3: (a) Crystal structure of the [Cd2(m-Tab)2(2,2,-bipy)4](PF6)4 (b)
[Cd2(m-Tab)2(phen)4](PF6)4
10
INTRODUCTION
Hydrothermal reactions of Cd(SAr)2 with 4,4-trimethylenebipyridine (tmdp) in
1:1.5 molar ratio at 145 C yielded new complexes, [Cd(SAr)2(tmdp)2]n [Ar = Ph (1),
C6H4Me-4, (2)], which are one-dimensional wave like coordination polymers with
distorted tetrahedral CdN2S2 coordination environments. The IR absorption bands
with variable intensity in the range of 1400–1610 cm−1 for these complexes
correspond to vibrations of the pyridyl rings of the tmdp ligands. The strong peaks in
the range of 500–900 cm−1 for ν(C–S) indicate the presence of thiolates in complexes.
The 1H NMR spectra of the DMSO solution of complexes display two distinct
resonance signals assigned to the different protons of the pyridyl group of the tmdp
ligands. The thermal stability of the two complexes was studied by thermal
gravimetric (TG) and differential thermal analyses (DTA).99
145 oC
Cd(SAr)2
[Cd(SAr)2(tmdp)2]n
+ tmdp
72 hrs
Ar = Ph, C6H4Me-4
Figure 1.4: ORTEP drawing of a structural unit of [Cd(SPh)2(tmdp)2]n
Mercury complexes containing simple saturated bifunctional 1,2-dithiolates
have not been structurally characterized,
dimercaptopropanol and some of
although related ligands such as
its derivatives are used
2,3-
in the treatment of
inorganic mercury poisoning. On varying the reaction conditions, treatment of HgCI2
with
ethane-1,2-dithiolate
[Ph4P]2[Hg3(SCH2CH2S)4]
and
Ph4PBr
containing
in
isolated
methanol
trinuclear
yields
anions
either
or
11
INTRODUCTION
[Ph4P]2[Hg2(SCH2CH2S)3]
with polymeric anions composed of quasi-isolated
binuclear subunits; both mercury thiolates may reflect characteristic structural
features of biologically active species.100
Figure 1.5: Structure of the trinuclear [Hg3(SCH2CH2S)4]2Isomorphous complexes [Zn(dmid)(phen)2] (1) and [Cd(dmid)(phen)2] (2)
where dmid = 2-oxo-1,3-dithiole-4,5-dithiolate, have been synthesized through a
ligand substitute reaction. Their structures and properties have been characterized by
elemental analysis, IR, UV–vis, fluorescence and single-crystal X-ray analysis. The
octahedral N4S2 coordination geometry, bonding, electronic structure and IR spectra
of the Zn(dmid)(phen)2 molecule were studied in detail using DFT and INDO/S
methods. In the crystal packing, there exists a strong - interaction between two
parallel 1,10-phenanthrolines of adjacent molecules.101
Figure 1.6: Molecular structure of Zn(dmid)(phen)2
Three zinc(II) complexes, [Zn(bipy)(dmit)]2 (l), [Zn(phen)(dmit)2] (2) and
[Zn(py)(mnt)] (3) where bipy = 2,2'-bipyridine, phen = 1,l0-phenanthroline, py =
pyridine,
H2dmit
=
4,5-dimercapto-l,3-dithiol-2-thione,
mnt
=
maleonitriledithiolate, have been synthesized and characterized by IR and electronic
12
INTRODUCTION
absorbtion spectra.102 The Zn-S bands are found in the far–IR region where as the
intense bands in the range 282-272 nm are assigned to the -* transition of the bipy,
phen and py groups attached to zinc metal.
(NBu4)2Zn(dmit)2 + L
CH2Cl2/CHCl3
Zn(NO3)2.6H2O + Na2mnt + Py
CH3OH
[Zn(L)(dmit)2]2
[Zn(Py)(mnt)] + 2NaNO3
2 hrs
L = bipy, phen
The species {Zn(dmit)} coordinates with 4,4’-bipyridyl, trans-1,2-bis(4pyridyl)ethene and 1,4-bis(imidazole-1-ylmethyl)-benzene as linkers giving rise to the
formation of coordination polymers [Zn(dmit)(4,4’-bipy)]n (1), [Zn(dmit)(4,4’-bpe)]n
(2) and [Zn(dmit)(bix)]n (3) respectively.103 In these syntheses, copper ion plays
important role by dragging a dmit ligand from [Zn(dmit)2]2-, resulting in the formation
of neutral Zn(dmit) species. The copper species, formed in these syntheses, could not
be isolated; the copper species, once formed, remain soluble in the present synthesis
conditions. The electronic absorption spectroscopy of compounds support these
intermolecular - interactions.103
[Bu4N]2[Zn(dmit)2] +
L
Cu(BF4)2.xH2O
CH3CN
[Zn(dmit).2L]n
L = 4,4'-bipy, 4,4'-bpe, bix
The
mixed-ligand
Zn(II)
complex
bis(-l,2-benzenedithiolato)-1
S,
1:22S'; 2S, 1:22S'-bis[(2,2'-bipyrimidine-2Nl,Nl')zinc], [Zn2(C6H4S2)2(C8H6N4)2],
containing benzenedithiolate (bdt)
and 2,2'-bipyrimidine (bpyrm)
has been
synthesized and found to have the dinuclear formulation [Zn(bdt)(bpyrm)]2. Since
only bis-monothiolate and dithiosquarate complexes, which have been shown to
be mononuclear, are luminescent, it appears that the luminescent properties of
these complexes are closely associated with the chemical environment within
which the whole molecule finds itself and that certain dithiolate ligands tend to
form multinuclear systems which do not exhibit emissive behavior.104
13
INTRODUCTION
C6H4S2 + Zn(CH3COO)2.2H2O + C8H6N4
C2H5OH
[Zn2(C6H4 S2)2 (C8H6N4)2]
Dianionic
mercury
[NMe4]2[Hg(R2C6S8)2]
bis(tetrathiafulva1ene
dithiolate)
complexes
(R = Et or Bu) and the corresponding oxidized neutral
complex [Hg(R2C6S8)2]
(R = Et) have been prepared. The crystal structure of
[NMe4]2[Hg(R2C6S8)2]
(R = Et) has been determined and shows that the
tetrathiafulvalene dithiolate units are tetrahedrally coordinated around the central Hg
atom. Cyclic voltammetry and ESR studies indicated that there is very little
interaction between two ligands. A compressed pellet of the powdered neutral
complex exhibited an electrical conductivity of l0-5 Scm-1 at room temperature.105
Figure 1.7: An ORTEP representation of the dianion [NMe4]2[Hg(R2C6S8)2]
1.1.2: THIOCARBOXYLATES
Thiocarboxylates are an interesting class of ligands that exhibit a large variety of
coordination modes due to the presence of both soft sulfur and hard oxygen donor
sites106-108 (Figure 1.8). Thus, with group 12th metals, as they are relatively soft ions,
the sulfur atom is typically joined in a monodentate fashion to the metal center.
Despite the zinc(II) ion being a borderline case and possessing an intermediate
hardness, given its small size it generally binds through the bulkier sulfur atom.109-115
14
INTRODUCTION
(a)
(b)
(c)
(d)
(e)
Figure 1.8: Various coordination modes of thiocarboxylates
Six new compounds with the formula [Zn(SCOR)2(N–N)] [R = –CH3 , –
C6H5; N–N = 2,2’-bipyridyl, 1,10-phenanthroline, 1,2-bis(4-pyridyl)ethylene,
neocuproine] have been obtained by the reaction of zinc acetate with the
corresponding pyridine derivative and thiocarboxylate in methanol in the ratio 1:2:1.
In all compounds, the metal atom is bonded to sulfur atoms of two thiocarboxylato
ligands and two nitrogen atoms from one bipyridyl derivative imposing a distortedtetrahedral geometry. The use of chelating bipyridyl ligands leads to discrete
monomeric entities in all the compounds. The presence of direct zinc–sulfur bonds is
a key factor to use these compounds as single-source precursors for the synthesis of
nanometric chalcogenide particles.116
Vitall and coworkers109 have reported [{M(SCOR)2(N2C10H8)}n ] [R = CH3, M
=
Zn
(1)
and
Cd
(2);
R=
C6H5,
M=
Zn
(3)
and
Cd
(4)]
and
[{Cd2(SCOC6H5)4(N2C10H8)}n] (5) The structures of 1, 3, 4 and 5 have been
determined by X-ray crystallography (Figure 1.9).
M(SCOR)2
+ N2C10H8
M= Zn, Cd;
2Cd(SCOC6H5)2 +
N2C10H8
[M(SCOR)2(N2C10H8)]n
R = CH3, C6H5
[{Cd2(SCOC6H5)4(N2C10H8)}n
All these compounds have one-dimensional zigzag polymeric structures. The
bridging nature of the thiobenzoate anion observed in [{Cd2(SCOC6H5)4(N2C10H8)}n]
is till now is unknown for Group 12th metal compounds. All the compounds
decompose to the corresponding metal sulfides in nitrogen atmosphere, according to
weight loss observed in TGA. Compounds provided cubic phases of the metal sulfides
while (4) and (5) gave hexagonal CdS from pyrolysis as confirmed by XRD.109
15
INTRODUCTION
Figure 1.9: Structure of [{Cd2(SCOC6H5)4(N2C10H8)}n]
Here in, Vittal et al.111 have utilized the possibility of altering the ratio of reactants to
result in tetrahedral anions, [M(SCOCH3)nCl4-n]; (n = 3, 4) and [Cd2Cl2(SCOCH3)4]2-.
Complexes of the formula [Ph4P]2[M(SCOCH3)4] [M = Zn(II) (1), Cd(II) (2) or Hg(II)
(3)] were synthesized by the reaction of thioacetate ligand with the metal salts and
Ph4PCl in 4:1:2 molar ratio in suitable solvents.
The tendency of monoanionic complexes [Ph4P][M(SCOCH3)3] to react with
1
mol
equivalent
of
Ph4PCl
resulted
in
complexes
of
the
type
[Ph4P]2[M(SCOCH3)3Cl] [M = Cd(II) (4) or Hg(II) (5)], in these complexes three
sulfur atoms and one chloride atom occupy the corners of the tetrahedron around the
metal centers. However, in 4:2:2 or 2:1:2 molar reaction of (CH3OCS) with CdCl2 and
Ph4PCl in aqueous medium resulted in a chloro bridged dimer [Ph4P]2[Cd2(Cl)2(SCOCH3)4] (6) as determined by X-ray crystallography.111 (Figure 1.10)
4CH3COS- +
M2+ + 2Ph4PCl
(Ph4P)2[M(SCOCH3)4] + Cl-
M = Zn(1), Cd(2) and Hg(3)
(Ph4P)2[(MSCOCH3)3Cl] + 2Ph4PCl
(Ph4P)2[(MSCOCH3)3Cl]
M = Cd(4) and Hg(5)
4CH3COS-
+ 2CdCl2 + 2Ph4PCl
(Ph4P)2[Cd2(Cl)2(SCOCH3)4] + 4Cl-
16
INTRODUCTION
Figure 1.10: ORTEP diagram of the anion in [Ph4P]2[Cd2(-Cl)2(SCOMe)4]
A series of group 12 metal thiocarboxylate species, M(SOCR)2Lut2 [M = Cd,
Zn; R = CH3, C(CH3)3; Lut = 3,5-dimethylpyridine (lutidine)], were synthesized to
investigate their potential to act as precursors for the formation of metal sulfide
materials. These species were expected to undergo thiocarboxylic anhydride
elimination to give stoichiometric metal sulfides and remove the organic supporting
ligands cleanly. These species were characterized by 1H,
13
C, and
113
Cd NMR
spectroscopies, TGA, elemental analysis, and single-crystal X-ray diffraction.
Cadmium-113 NMR chemical shifts were in the region of 350 ppm for these
compounds and the analogous TMEDA compounds, which is typical for cadmium in
a tetrahedral CdS4N4 environment. No Cd-H coupling was observed for these
compounds since the nearest hydrogen was 4 bonds away from the cadmium. The
infrared spectra for crystalline samples showed the presence of bands mainly above
1620 cm-1 which were assigned to uncoordinated v(Cd=O) in thiocarboxylate
carbonyls and the v(C-S) bands were found around 960 cm-1 consistent with
coordinated v(C-S). In the solid state the compounds are monomeric with approximate
tetrahedral metal coordination environments and monodentate S-bond thiocarboxylate
ligands.113
Zn(II), Cd(II) and Hg(II) -caprolactam-3-dithiocarboxylic acid complexes
were synthesized by reacting the -caprolactam-3-carbothioic sodium salt with the
respective metal salt as shown in Scheme 1.2. Samples were characterized by X-ray
powder diffraction, Elemental analysis, UV-visible, FT-IR, 1H NMR and EPR
spectroscopy. Thermal properties were determined using thermo-gravimetric and
differential scanning calorimetric analysis. Complexes showed intense electronic
17
INTRODUCTION
delocalization due to the charge transfer (420 nm) induced from the metal to the
dithiolate group reaching different stages into the V unit (350 nm) of the
dithiocarboxylate ring with a ‘‘n→” (310 nm) transition. This transition was also
observed by EPR which showed 3 parallel and 3 perpendicular signals. The
complexes are stabilized by the electro-attraction of the amidic and carbonyl groups;
the stability trend is Zn > Cd > Hg. Thermal decomposition shows a multi-step
fragmentation process that suggests lactamic chain rupture.117
O
H
O
S
H
SNa
N
S
M
S
N
+
+ MCl2
NaCl
+
HCl
Scheme 1.2: General scheme for the formation of complex where M= Zn, Cd and
Hg
The synthesis of N-methylcaprolactam-3-dithiocarboxylic acid complexes
with the non transition metals Zn(II), Cd(II) and Hg(II) were carried out and the
complexes characterized using FT–IR, Raman, XRD, SEM, EDS and elemental
analyses. The IR results confirm the link between the caprolactam and the
dithiocarboxylate through the C–S bond, whereas Raman spectroscopy gave
information about the S–M stretch for each complex. X-ray diffraction analysis shows
that the complexes adopt tetrahedral coordination geometry.118
O
H3C
N
S M
S
General scheme of the complexes where M = Zn, Cd and Hg
Anionic
zinc(II)
complexes,
[Zn(SCOR)3]-
[R
=
Th
(1)]
tris(thiophen-2-thiocarboxylato)zincate(II) (1) have been used for the synthesis of
heterobimetallic complexes, [(PPh3)Cu(-SCOR)3Zn(PPh3)] [R = Ph (2) and th (3)].
All the three complexes have been characterized by FTIR, 1H and
13
C NMR
spectroscopy. The synthetic reactions involved phosphine migration from Cu(I) to
Zn(II) in the cases of (2) and (3). Molecular structures of the complexes have been
determined by single crystal X-ray diffraction and the structural features have been
18
INTRODUCTION
explained on the basis of NBO calculations. The Cu–Zn distance in these molecules
are shorter than the sum of their covalent radii indicating the existence of a bond
between the metals. Electronic spectral behaviors of the complexes have been
explained by TDDFT calculations.119
Zn(NO3)2.6H2O + 3RCOSH
+ 3NaOCH3
CH3OH
(Ph3P)Cu(uSCOR)3Zn(PPh3)
(Ph3P)2Cu(NO3)
Na[Zn(SCOR)3]
Ph4PBr
[Ph4P][Zn(SCOth)3]
(1)
R = Ph (2), th (3)
Figure 1.11: Thermal ellipsoid plot of [(PPh3)Cu(-SCOPh)3Zn(PPh3)]
A simple preparation of metal sulfide nanoparticles via the decomposition of
thiobenzoate precursors at room temperature. Long chain alkylamines were found to
mediate the breakdown of metal thiobenzoates, [Cd(SCOC6H5)]. These precursors are
air-stable and could be readily prepared from thiobenzoic acid and the corresponding
metal salts following the known literature method.120 CdS is one of the most studied
metal sulfides, due to its various applications. When CdTB precursor was mixed with
oleylamine, spherical CdS nanoparticles with an average diameter of 5.3 ± 0.7 nm
were produced as shown in Scheme 1.3.121
R'
R
N
O
H
C
M
S
C6H5
O
M
R
H
N
C
R'
MS
S
C6H5
Scheme 1.3: A generalized reaction scheme for the initial attack of alkylamine
onto metal thiobenzoate
19
INTRODUCTION
1.1.3: DITHIOCARBAMATES
A large class of sulfur donor ligands comprise the dithiocarbamates [R2NCS2]2ligand, function either as unidentate or bidentate (chelating) mode of linkages.
Dithiocarbamates of zinc and cadmium have continued to attract attention in recent
years on account of their industrial applications122 and biological profiles.123-124
Dialkyl dithiocarbamato complexes of zinc and cadmium have been used as singlesource precursors to prepare nanoparticles and to deposit ZnS or CdS thin films by
MOCVD.125 The affinity of 1,1-dithiolate ligands for metals such as zinc and
cadmium was indicated by the fact that the ligands can be employed as scavengers for
these elements in biological media. Besides that, nitrogen donor adducts of
dithiocarbamate complexes are also widely used in the preparation of thin
semiconductor126-127 and electroluminescent.128
Zn(II), Cd(II) and Hg(II) complexes of N-ethyl-N-phenyl dithiocarbamate and
N-butyl-N-phenyl dithiocarbamate were prepared as by general method and
characterized by elemental analyses, NMR and IR spectroscopy.
MCl2 + 2(S2CNRR')NH4
H2O
M( S2CNRR')2
M =Zn, Cd, Hg; R = C6H5; R' = C2H5, C4H9
Four coordinate geometry is proposed for the Cd(II) and Hg(II) complexes. Xray crystal structures of the two zinc complexes revealed that one of the complexes
has distorted trigonal bipyramidal geometry and the other is tetrahedrally coordinated.
The potential of the complexes as single source precursors for semiconductor
nanoparticles is being investigated.129
Figure 1.12: Crystal structure of [Zn2(C9H10NS2)4]
20
INTRODUCTION
Bis(dimethyldithiocarbamato)zinc(II) complexes can be readily obtained by the
reaction of zinc(II)chloride
with sodium dimethyldithiocarbamate in ethanolic
medium. The coordination sphere of the zinc atoms in both the gas phase and solid
phase is pseudotetrahedral.130
ZnCl2 + [S2CN(CH3)2]2
C2H5OH
[S2CN(CH3)2]2Zn
Decken et al.132 have reported colorless crystals of Zn[S2CN(CH2C6H5)2]2
grown by solvent evaporation from a dichloromethane solution layered with
diethylether (Figure 1.13). The molecular structure of Zn[S2CN(CH2C6H5)2]2,
features a pair of chelating dithiocarbamate ligands, each of which forms significantly
different Zn–S bond lengths the two ligands are related via two-fold axis. The
coordination geometry around the zinc atom is best described as a very highly
distorted tetrahedral arrangement of the four sulfur atoms. This complex represents a
rare example of a monomeric structure within the zinc-triad of 1,1-dithiolates. Thus,
the overall solid-state structure is similar to the only other known examples of
monomeric
binary
zinc
dicylohexyldithiocarbamato]zinc(II)131
dithiocarbamates,
and
viz.
bis[N,N-
bis[N-n-butyl-N-(3,5-di-tert-butyl-2-
hydroxybenzyl)dithiocarbamato]zinc(II).132
Figure 1.13: Molecular structure of Zn[S2CN(CH2C6H5)2]2
The compound, [Zn2(C9H18NS2)4], contains two unique Zn(II) metal centres,
showing almost identical slightly distorted tetrahedral coordination environments and
forming a dinuclear complex with two skew-bridging syn-N,N-dibutyldithiocarbamate
ligands. Two other dithiocarbamate ligands are connected to the Zn(II) centers in a
syn, syn-chelate coordination mode. The above compound was synthesized by the
following method.133
21
INTRODUCTION
CS2
+ 2[(C4H9)2NH] + Zn(OH)2
H2O
Zn[S2CN(C4H9)2]
The mononuclear structure of Zn[S2CN(CH3)C6H5]2 features a tetrahedral zinc
center defined by two chelating dithiocarbamate ligands as shown in Figure 1.14.
This complex represents an example of a monomeric structure for the zinc
dithiocarbamates, which are usually dimeric.134 Supramolecular association leading to
a dimer is found in the structure of [Zn(S2CN(CH3)2]2,135 but the presence of bulky
substituents, such as cyclohexyl and benzyl, prevent aggregation.136
Figure 1.14: Molecular structure of Zn[S2CN(CH3)C6H5)]2
Ghafar et al. reported the complex [Zn(C4H8NS2)2(C10H8N2)], prepared by the
reaction shown below as white solid and recrystallized from ethanol to yield colorless
blocks. This complex shows (Figure 1.15) that divalent zinc tetrahedral complexes
expand their coordination number by adding neutral nitrogenous ligands.137
ZnCl2 + (C2H5)(CH3)NH + CS2 + N2C10H8
C2H5OH
[Zn(C4H8NS2)2(C10H8N2)]
Figure 1.15: Molecular structure of [Zn(C4H8NS2)2(C10H8N2)]
22
INTRODUCTION
Similarly, addition of 2,2-bipyridyl to the monomeric structure of
Zn[S2CN(CH2C6H5)2]2 leads to a distorted trigonal prismatic coordination geometry
for zinc defined by an N2S4 donor set. Owing to variations in the mode of
coordination of the dithiocarbamate ligands and the steric demands of the diimine
ligands operating in these adducts, coordination geometries range from tetrahedral,130
to the more common distorted octahedral geometry e.g. {Zn[S2CN(CH2)4]2(2,9(CH3)2-1,10-phen)} as shown in Figure 1.16.138
Figure 1.16: Molecular structure of {Zn[S2CN(CH2Ph)2]2(2,2-bipy)}
Poppel
and
coworkers139
have
reported
three
bis(N-
alkyldithiocarbamato)cadmium(II) complexes [Cd(S2CNHR)2] (R= C3H7; R = C5H11;
R = C12H25) (Figure 1.17) prepared by metathetical reaction of the following and then
recrystallized from THF/toluene.
2Li[S2CNHR]
+
CdCl2
H2O
- 2LiCl
Cd[S2CNHR]2
R = C3H7,C5H11,C12H25)
Figure 1.17: Structure of [Cd(S2CNHC5H11)2]
23
INTRODUCTION
In the solid state, thermal gravimetric analyses show that all three complexes
decompose smoothly as shown in Scheme 1.4 via a heterolytic C−S bond cleavage
reaction to give the corresponding alkyl isothiocyanate and cadmium sulfide as the
primary products, with the formation of primary amine and CS2 as coproducts.139
R
S
Cd
S
S
H
S
N
H
N
R
Et3N
N
R
S
Cd
S
S
S
H
[Et3NH+]
NR
CdS + RNCS + [RHNCS2-][Et3NH+]
(Scheme 1.4)
Tan
al.140
et
have
prepared
needles
like
crystals
of
[{Cd[S2CN(iPr)CH2CH2OH]2}3·CH3CN]∞ (a) and Cd[S2CN(iPr)-CH2CH2OH]2 (b) by
general reaction given below. These are characterized by spectroscopic methods like
1
H, 13C, and
113
Cd NMR and UV-vis.
113
Cd NMR chemical shifts are dependent on a
number of factors, including the electronegativity of the coordinated atoms and the
coordination number of the metal. In this regard, chemical shifts move upfield (more
negative) with increasing coordination number.140
2Na[S2CN(iPr)CH2CH2OH] + CdCl2.21/2H2O
H2O
Cd[S2CN(iPr)CH2CH2OH]2
The simple dialkyldithiocarbamates of zinc and cadmium have dimeric
structures in the solid state, but are monomeric in the vapour phase. The dimers can
be broken by adduct formation as illustrated by recent studies of the 2,2'- bipyridyl
and 1,l0-phenanthroline adducts of Cd[S2CN(C2H6)2]2 by Airoldi and coworkers.141
The
mixed-ligand
compounds
have
higher
volatility
than
their
parent
dithiocarbamates. Dimeric solid-state structures are characterized by coordination
numbers of four.142- 143
Bis(dithiocarbamates) of zinc and cadmium with N,N,N'-trimethylpropanel,3-diamine have been prepared by extension of methods142 previously used to
synthesize simple bis(dialky1dithiocarbamates). The present derivatives are of
interest as single-molecule precursors for the growth of Group(II)-Group(VI)
semiconductor
films
by
MOCVD.
X-Ray crystallographic investigations of
24
INTRODUCTION
compounds
{Zn[S2CN(CH3)CH2CH2CH2N(CH3)2]2}n
{Cd[S2CN(CH3)CH2CH2CH2N(CH3)2]2}2 (b) revealed
(a)
and
fundamentally
different
structure types. Polymeric in case of (a) but dimeric in case of (b). Dimethylamino
groups are involved in bonding to metal centers in all structures. Unsurprisingly in
view of its polymeric nature in the solid state (a) undergoes partial decomposition on
volatilization. However, MOCVD an experiment in which (a) was vaporized at
150 C resulted in the deposition of ZnS films.143a-b
The unit cell of the Cd(II) compound comprises two centrosymmetric isomeric
binuclear molecules [Cd2{S2CN(CH2)5}4], which display structural inequivalence in
both
15
N and
113
Cd NMR and XRD data. There are pairs of the dithiocarbamate
ligands exhibiting different structural functions in both isomeric molecules. Each of
the terminal ligands is bidentately coordinated to the cadmium atom and forms a
planar four-member chelate ring [CdS2C]; where pairs of the tridentate bridging
ligands combine two neighbouring cadmium atoms forming an extended eightmember tricyclic moeties [Cd2S4C2], whose geometry can be approximated by a
‘chair’ conformation.144
Konarev
et
al.145
reported
the
ionic
crystal
(DMI+)2·(C60•−)·{Cd(Et2NCS2)2I−}, containing fullerene radical anions. The anions
of cadmium diethyldithiocarbamate iodide and N,N′-dimethylimidazolium cations
was obtained and it has been found that fullerenes are monomeric at 250 K and form
three-dimensional packing in which each fullerene has nearly tetrahedral surroundings
from neighboring fullerenes. The composition of the salt was determined by the X-ray
diffraction study of a single crystal.145 (Figure 1.18)
Figure 1.18: Crystallographically independent unit in the monomeric
phase (DMI+)2·(C60•−)·{Cd(Et2NCS2)2I−}
25
INTRODUCTION
Four new cadmium dithiocarbamate complexes [Cd(2-mpipdtc)2(1,10-phen)],
[Cd(2-mpipdtc)2(bipy)], [Cd(4-mpipdtc)2(1,10-phen)], [Cd(4-mpipdtc)2(bipy)] (where
2-mpipdtc
=
2-methylpiperidinecarbodithioate
anion,
4-mpipdtc
=
4-
methylpiperidinecarbodithioate anion) have been reported. IR spectra of the
complexes show the contribution of the thioureide form to the structures. Reduction in
vC–N (thioureide) for the mixed ligand complexes is attributed to the change in
coordination number from four to six and the steric effect exerted by 1,10phenanthroline or 2,2’-bipyridyl. Single crystal X-ray structural analysis (Figure
1.19) of [Cd(4-mpipdtc)2(1,10-phen)] showed that the cadmium is in a distorted
octahedral environment with a CdS4N2 chromophore.146
Figure 1.19: ORTEP diagram of [Cd(4-mpipdtc)2(1,10-phen)]
Normah and coworkers reported {Cd[S2CN(iC4H9)(C3H7)]2(L)} (L = C12H8N2
or C10H8N2) dithiocarbamate compounds which have been successfully synthesized
by the reaction of bis(N-sec-butyl-N-propyldithiocarbamato)cadmium(II) with 2,2’bipyridyl or 1,10-phenanthroline. These adducts were characterized by spectroscopic
studies.
The
crystal
structure
of
propyldithiocarbamato)cadmium(II)(1,10-phenanthroline)
bis(sec-butyl-Nwas
successfully
determined which showed the compound monomeric with hexacoordination of the
cadmium atom in a highly distorted octahedral geometry.147
26
INTRODUCTION
Figure 1.20: Crystal Structure of {Cd[S2CN(iC4H9)(C3H7)]2(N2C12H8)}
Polycrystalline
adduct
bis(N,N-di-iso-butyldithiocarbamato-
S,S’)(pyridine)cadmium(II) was prepared by the following procedure.148
[Cd2{S2CN(iC4H9)2}4] + C5H5N
Zn(II),
Cd(II)
and
C6H5CH3
Hg(II)
[Cd(C5H5N){S2CN(iC4H9)2}2]
complexes
of
N-methyl-N-phenyl
dithiocarbamate149a and N-ethyl-N-phenyl and N-butyl-N-phenyl dithiocarbamates149b
have been synthesized and characterized by elemental analysis and spectral studies
(IR, 1H and 13C-NMR).
H3C
H3C
2
N CS2Na
+
MCl2
H2O
-2NaCl
S
S
M
N
S
N
S
CH3
M = Zn, Cd and Hg
The structure of the mercury complex revealed that each Hg atom is
coordinated to four S atoms from the dithiocarbamate moiety. One dithiocarbamate
ligand acts as chelating ligand while the other acts as chelating bridging ligand
between two Hg atoms, resulting in a dinuclear eight-member ring. Thermogravimetric analysis of the complexes show a single weight loss to give MS (M = Zn,
Cd, Hg) indicating that they might be useful as single source precursors for the
synthesis of MS nanoparticles and thin films.149a However in case of N-ethyl-Nphenyl and
N-butyl-N-phenyl dithiocarbamates results show that the zinc and
27
INTRODUCTION
cadmium complexes undergo decomposition to form metal sulfides and further
undergo oxidation forming metal oxides as final products while the mercury
complexes gave unstable volatiles as the final product.149b
Mercury(II) dithiocarbamate complexes have been known for many year and
have been widely used as fungicides.150a A number of their chemical, physical and
spectroscopic properties have been examined. Usually, they are isolated as complexes
with the empirical formula Hg(RR’dtc), where RR’dtc represents the dithiocarbamate
ligand, Structurally, these complexes can be monomeric or dimeric in the solid
state.150a
The
salts
ammonium
chloride
(R2NH2Cl)
and
dialkylammonium
dialkyldithiocarbamate (R2NH2S2CNR2) R = CH3 and iC3H7 were synthesized.
Complexes
of
dialkyldithiocarbamates
of
mercury(II)
[Hg(S2CNR2)2]
were
synthesized from the direct reaction of HgCl2 with the corresponding amine and
carbon disulfide in acetone under a dry gaseous nitrogen atmosphere.150b
2R2NH2S2CNR2 + HgCl2
(CH3)2CO
N2 atm.
[Hg(S2CNR2)2]
R = CH3, iC3H7
Colorless crystals of Hg[S2CN(CH2C6H5)2]2 were obtained from the slow
evaporation of a chloroform solution of the compound.151 The mercury atom in this
compound lies on a twofold axis and exists in a grossly distorted tetrahedral geometry
as the result of two unsymmetrically coordinating dithiocarbamate ligands. This
structure, along with the isomorphous zinc analogue, is consistent with ‘steric control
over molecular aggregation’ for zinc-triad 1,1-dithiolate structures. As such, the
mercury (and zinc) structure is a member of the least common, i.e. monomeric, motif
owing to the steric bulk of the N-bound groups.152
Five distinct structural motifs are known for mercury(II)bis-dithiocarbamates,
ranging from isolated mononuclear entities to dinuclear oligomers and two
dimensional array.151 The
[Hg(S2CN(CH2)4)2] was prepared by the reaction of
ammonium pyrrolidinedithiocarbamate with mercury(II) salt as anticipated resulted in
the formation of insoluble precipitates and there crystal were isolated from an
acetonitrile/chloroform
(1:1)
solution
containing
equimolar
amount
of
[Hg(S2CNEt2)2] and [Zn(S2CN(CH2)4)2] via ligand exchange method.153 The mercury
28
INTRODUCTION
atom in this complex is coordinated by two dithiocarbamate ligands leading to
distorted tetrahedral geometry.154
Figure 1.21: Molecular structure of [Hg(S2CN(CH2)4)2]
The procedure for the synthesis of [Hg{(C2H5)2NCS2}2Phen] is described by
Larionov and coworkers.155 The coordination polyhedron of the Hg atom is a distorted
octahedron formed by four S atoms of the two cyclic bidentate dithiocarbamate
156
ligands and two N atoms of the cyclic bidentate Phenanthroline ligand.
C6H5CH3
{Hg[(C2H5)2NCS2]2} + C12H10N2
[Hg(C12H10N2){(C2H5)2NCS2}2]
1.1.4: DITHIOPHOSPHATES
The chemistry of metal-sulfur bond has been reviewed by several researchers during
last four decade157a-c highlighting various aspects of the bonding modes in relevance
to biochemical, industrial, agricultural and analytical applications. On the basis of 31P
NMR chemical shift for a number of metal dithiophosphates, Glidewell157d has
beautifully correlated the bonding modes as ionic, monodentate, bidentate or chelating
(Figure 1.22).
S
S
S
P
P
S
P
S
M
M
S
Monodentate
Ionic
M
Chelate
P
S
S
M
P
S
M
M
P
S
P
M
S
S
S
S
S
S
S
P
M
S
P
Anisobidentate
Bidentate bridging
Bidentate tri-connective
Figure 1.22: Various possible bonding modes of dithiophosphate ligands
29
INTRODUCTION
Zinc(II) dithiophosphates have got considerable attention because these have
been key additives to motor vehicle lubricants158a owing to their high antioxidant
activity and antiwear properities. O,O′-alkylenedithiophosphates of zinc and cadmium
158b
are easily accessible by the following reaction:
MX2
+
2NH4[S2POGO]
M[S2POGO] + 2NH4X
(M = Zn, Cd; X = Cl, CH3COO; G = -CH2CMe2CH2-,-CMe2CMe2-,
-CHMeCHMe-, -CMe2CH2CHMe-, or -CH2CEt2CH2-)
Zn4[S2P(OR)2]6O has been isolated by the hydrolysis of Zn[S2P(OR)2]2 with
H2O in presence of a base (i.e. NEt3, NHEt2) as follow:
Y
Zn[S2P(OR)2]2 + H2O
Zn4[S2P(OR)2]6O +
2YH[S2P(OR)2]
(R = C2H5, iC3H7; Y = NEt3, NHEt2)
Harrison and coworkers reported the crystal and molecular structure of
Zn4[S2P(OC3H7)2]6S, byproduct in the synthesis of Zn4[S2P(OC3H7)2]6O, which
revealed that each molecule possesses a threefold axis which is collinear with the
unique zinc sulfide bond of the central Zn4S unit. Nevertheless, the unit exhibit almost
perfect tetrahedral symmetry.159a
(a)
(b)
Figure 1.23: Molecular structure of (a) Zn4[S2P(OC2H4)2]6S and
(b) Zn[S2P(OiC3H7)2]2.Py
Zn[S2P(OiC3H7)2]2.L have been synthesized by the reaction Zn[S2P(OiC3H7)2]2
with nitrogen donor ligands [i.e. pyridine (py), ethylenediamine (en), 1,1030
INTRODUCTION
phenanthroline (phen) etc.], which depicts both mono- and bidentate mode of bonding
of dithiophosphate ligand. Polymeric species like [Zn(C8H17O2PS2]2(C12H12N2)]n or
[Zn{S2P(OiC4H11)2}2{NC5H4C(H)=C(H)C5H4N}]n, are known160a where Zn atom depicted
distorted octahedral (N2S4) geometry. The polymers topology is a straight chain in
which the Zn atom is located on a centre of inversion and the bridging bipyridine is
situated about another centre of inversion (Figure 1.24).
N
N
O
S
O
P
Zn
P
O
S
S
S
O
n
Figure 1.24: Distorted octahedral N2S4 geometry of
[Zn(C8H17O2PS2]2(C12H12N2)]nor[Zn{S2P(OiC4H11)2}2{NC5H4C(H)=C(H)C5H4N}n
The combination of steric influences exerted by both the Lewis acid i.e.
Zn(S2P(OR)2)2 and Lewis base (4,4’-bipyridyl) allows the control of polymer
formation and topology. In the case of adduct formation with Zn[S2P(OiC3H7)2]2, the
product formed is determined by the ratio of Zn[S2P(OiC3H7)2]2 to bipyridine ligand.
Thus, stoichiometric control of polymer formation is evident. The stoichiometry of
reaction was not the factor that determined the degree of aggregation in the solid state
but this is ascribed to steric effects associated with the Zn[S2P(OC6H11)2]2 molecule as
a
polymeric
structure
is
known
for
the
analogous
species
[Zn{S2P(OiC3H7)2}2(NC5H4C5H4N)]n.160b
O,O’-Ditolyldithiophosphato
complexes
of
zinc(II),
cadmium(II)
and
mercury(II) corresponded to [(CreO)2PS2]2M (CreO = o-, m- and p-CH3C6H4 and M =
Zn, Cd and Hg) have been synthesized by the reaction as per scheme in 1:2 molar
stoichiometry under anhydrous conditions. These complexes were characterized by
elemental analyses, molecular weight determination, IR and NMR (1H,
13
C and
31
P)
spectral studies, which revealed monomeric nature of these complexes and the metal
atom being four coordinative bonded to two bidentate dithiophosphate ligands,
leading to a square plannar geometry around the metal atom.161
31
INTRODUCTION
MCl2
+ 2(CreO)2PS2HNEt3
toluene
[{(CreO)2PS2}2M]
Reflux 4-7 hours
-Et3NHCl
M = Zn, Cd and Hg; Cre = o-, m- or p-C6H4CH3
Zinc O,O’-diisopropylphosphorodithioate [Zn2(dtp)4] and cadmiumO,O’diisopropylphosphorodithioate,
[Cd2(dtp)4], where dtp
=
(iC3H7O)2PS2, were
isolated. Molecules of zinc and cadmium diisopropylphosphorodithioates in the
crystalline state exist as dimers with symmetry and may be represented by the
formula M2[(iC2H7O)2PS2]4, M = Zn or Cd. The species, illustrated in Figure
1.25, are isomorphous in both geometry and molecular packing.162
Figure 1.25: Stereographic drawings of the zinc and cadmium O,Odiisopropylphospliorodithioate dimers
Bis(alkylene dithiophosphates) of the type M[S2 POGO]2 (where M = Zn,
Cd;
G
=
—CH2C(CH3)2CH2—,
—C(CH3)2CMe2—,
—CHCH3CHMe—,
—C(CH3)2CH2CHMe—, —CH2C(C2H4)2CH2—) obtained by the reaction of MX2
where X = Cl, CH3COO, S2P(OR)2 (R = C2H4, C3H7) with alkylene dithiophosphoric
acids or their ammonium salts as white or yellow coloured solid. These are insoluble
in common organic solvents but are soluble in DMSO, DMF and pyridine. These have
been characterized on the basis of elemental analyses, molar conductivity, IR and
NMR (1H and 31P) spectral studies which revealed the bidentate behaviour of the
dithiophosphate moiety.163
Cadmium O,O′-diethyl- and O,O′-di(sec-butyl)phosphorodithioato complexes
have been synthesized and characterized in detail by 13C, 31P and 113Cd NMR spectral
studies.164 X-ray crystallography shows that complex has a binuclear molecular
32
INTRODUCTION
structure [Cd2{S2P(OC4H9)2}4]. The dithiophosphate ligands are bidentately S,S'coordinated to the metal to yield flat four-membered chelate rings [CdS2P]. The
geometry of these rings deviates somewhat from planar geometry (Figure 1.26).
.
Figure 1.26: Molecular structure of [Cd2{S2P(OC4H9)2}4]
2,2΄-bipyridyl
New
adduct
of
bis(O,O΄-di(2-
phenylethyl)dithiophosphato)cadmium(II), [Cd{S2P(OCH2CH2Ph)2}2·bipy] (bipy =
2,2΄-bipyridyl) was synthesized and characterized by elemental analyses, IR, UV-vis,
1
H NMR, fluorescence spectroscopy, thermo-gravimetric analysis and X-ray single-
crystal diffraction (Figure 1.27). The result shows that the Cd(I) centre is fivecoordinated by two N and three S atoms in a highly distorted square pyramidal
configuration.165
[Cd{S2P(OCH2CH2Ph)2}2]
+
N2C10H8 (CH3)2CO
[Cd{S2P(OCH2CH2Ph)2}2.N2C10H8]
2h
Figure 1.27: Molecular structure of [Cd{S2P(OCH2CH2Ph)2}2·bipy]
Casas
and
coworkers166
reported
cadmium(II) by reacting cadmium(II)
bis(dicyclohexyldithiophosphato)
perchlorate and
sodium salt of
dicyclohexyldithiophosphoric acid in ethanol.
33
INTRODUCTION
Cd(ClO4)2.6H2O
+ 2(CyO)2PS2Na
C2H5OH
[Cd{S2P(OCy)2}2]2
The structure consists of dimers in which each metal centre is coordinated
by a chelating ligand and two bridging ligands, giving a coordination number of
4. The two bridging ligands and the two cadmium atoms form an eightmembered ring with a twisted chair conformation. This complex is characterized
by elemental analysis, IR, 1H, 31P, 13C, 113Cd NMR spectroscopic techniques.166
The Cd(S2P(OR)2)2, R = iC3H7 and C6H11, precursors were prepared in high
yield from the reaction of CdSO4.H2O and the respective ammonium dithiophosphate
in aqueous solution and their adducts were obtained from refluxing the parent
cadmium compound with a stoichiometric amount of the respective bipyridine in
chloroform solution.167
O,O-Dipropyldithiophosphate
and
O,O-dibutyldithiophosphate
(Dtph)
cadmium(II) complexes were prepared and studied by means of heteronuclear
31
P,113Cd,
13
C CP/MAS NMR spectroscopy and single-crystal X-ray diffraction.
Linear-chain polynuclear structures have been established for both cadmium(II)
complexes, in which each pair of equivalent dithiophosphate groups, playing the same
bridging structural function, asymmetrically links the neighboring cadmium atoms.
One remarkable structural feature of the synthesized cadmium(II) compounds is
defined by the alternation of two types of conformationally different (chair–saddle)
eight-membered rings [Cd2S4P2] in the polymeric chains. Therefore, in both 31P NMR
and XRD data, the bridging dithiophosphate ligands exhibit structural inequivalence
in pairs. All experimental
31
P resonances were assigned to the phosphorus structural
sites in both resolved structures.168 Polynuclear dialkyldithiophosphate cadmium(II)
complexes were prepared as :
2K{S2P(OR)2} + Cd(ClO4)2.6H2O
[Cd{S2P(OR)2}2]n
R = C3H7, C4H9
The Cd(S2P(OiC3H7)2)2 compound was prepared in a high yield from the
reaction of Cd(SO4).H2O and the ammonium dithiophosphate in aqueous solution.
34
INTRODUCTION
Adducts were obtained from refluxing the parent cadmium compound with a 1:1
stoichiometric amount of the n-pyridinealdazine ligand, n = 2, 3 and 4, in CHCl3
solution.169 The structure of these complexes has been deduce by single crystal X-ray
analysis.
Cd(SO4).H2O + 2 NH4{S2P(OR)2
Cd[S2P(OiPr)2]2
+
n-N4C12H10
H2O
CHCl3
Cd[S2P(OiPr)2]2
{Cd[S2P(OiPr)2]2.n-N4C12H10}
n = 2, 3, 4
The
polymeric
compounds
{Cd(bix)[(CH3O)2PS2]2}n
and
{Cd(bix)[(C2H5O)2PS2]2}n (bix = 1,4-bis(imidazole-l-ylmethyl)benzene) have been
synthesized and characterized by single-crystal structure determinations, elemental
analyses and IR spectra. X-ray diffraction studies revealed that they exhibit onedimensional polymeric structures with a zigzag chain and a linear chain, connected by
stacking interactions to form 2D networks.170 (Figure 1.28)
Figure 1.28: Section of the crystal structure {Cd(bix)[(C2H5O)2PS2]2}n
The
adduct
[Cd{S2P(OC6H11)2}2(3-NC5H4C(H)=NN=C(H)C5H4N-
3).(CHCl3)2]α was obtained from refluxing the parent cadmium compound with a 1:1
stoichiometric amount of the 3-pyridinealdazine ligand in CHCl3 and then
recrystallised by slow evaporation from chloroform/acetonitrile (3:1) solution of the
compound to yield crystals suitable for the X-ray study. The compound was isolated
as its di-chloroform solvate.171
35
INTRODUCTION
Cd(S2P(OCy)2)2
+ 3-NC5H4C(H)=NN=C(H)C5H4N-3
CHCl3
Cd(S2P(OCy)2)2(3-NC5H4C(H)=NN=C(H)C5H4N-3)
The dialkyldithiophosphates of the type ML2 [M = Cd or Hg; L = (RO)2PS2]
and their adducts like CdL2(py)2, CdL2(pic)2, (pic = 2-methylpyridine) have also been
reported.
Binuclear
diisopropyl-
and
dicyclohexyldithiophosphato
cadmium
complexes namely [Cd2{S2P(OR)2}4] were studied by high resolution heteronuclear
spectroscopy in the solid state. Organomercury derivatives of sulfur ligands show the
tendency to self-assemble in the solid state through secondary bonds and to form
supramolecular structures, which can be either cyclic (or quasi-cyclic)
dimers or
polymeric arrays.172-174 Phenylmercury(II)-O,O′-dithiophophates, PhHg[S(S)POGO],
have depicted less common monodentate mode of bonding by dithio ligand.175
S O
Hg S P
G
O
(G = -CH2C(H)CH3, -CH2(CH2)3CH2-, C(CH3)2C(CH3)2-)
The compound Hg[S2P(OiC3H7)2]2 is reported to have crystallized in the
centrosymmetric P21/C space group. It is interesting to note that the same compound is
reported to crystallize in the space group C2/C space group as well.176 However in both
the cases (Figure 1.29) one phosphorodithioate moiety acts as a chelating group and
the other as a bridging group between neighboring mercury atom to form infinite
polymers.
36
INTRODUCTION
Figure 1.29: View of Hg[S2P(OiC3H11)2]2 in (a) P21/C space group (b) C2/C space
group
The monomeric unit [Hg(µ-S2P(OCp)2)(S2P(OCp)2)] was synthesized by
reacting aqueous solution of HgCl2 with NH4+ dcpdtp. In this complex one
dithiophosphate ligand acts as a chelating ligand and the other one act as a bridging
ligand by their sulfur atoms. The monomeric units arrange in order to give rise to an
infinite polymeric structure along the direction of the b axis by the two-fold screw
axis.177
The reaction between O,O-diethyl-dithiophosphoric acid and diethyl mercury,
and that between mercuric O,O-diethyl-dithiophosphoric and diethylmercury have
been investigated.178 It is found that they both proceed smoothly according to the
following equation:
(C2H5O)2P SH + (C2H5)2Hg
(C2H5O)2P SHgC2H5 +C2H6
S
S
[(C2H5O)2P S]2Hg + (C2H5)2Hg
2(C2H5O)2P SHgC2H5
S
S
The reaction can be satisfactorically utilized for the synthesis of a series of
ethyl mercuric dithiophosphates:
S
(RO)2P S HgC2H5
R = CH3, C2H5, iC3H7, nC4H9, nC5H11, iC5H11, C6H5
37
INTRODUCTION
The
preliminary biological
evaluation
of
these
organo-phosphorous
178
compounds exhibited mild but some significant auxin properties.
The phenylmercury(II) derivatives PhHgS2P(OR)2 (R = C2H5, C6H11 and
C6H5) have been synthesized and characterized by positive ion FAB and 13C, 31P and
199
Hg
NMR.
In
this
(O,O′-diethyldithiophosphate)
phenylmercury(II),
C10H15HgO2PS2, the mercury atom is coordinated to the phenyl carbon atom and to a
ligand sulfur atom in an almost linear arrangement the ligand is almost monodentate.
The second sulfur atom only being involved in a weak secondary intermolecular
bond.179
1.1.5: DITHIOCARBONATES (XANTHATES)
Dithiocarbonates (xanthates) are one of the interesting member of the 1,1-dithiolate
family. These have been extensively used in classical and organometallic chemistry
for several decades. Xanthates are the reaction products of carbon disulfide, alcohol
and alkali when these reacted in 1:1:1 stoichiometric ratio.50
ROH + CS2 + MOH
-H2O
RO
C
SM
S
(R = Me, Et, Pr, Bu and M = Na and K)
Gomez180 has described a method for the preparation of the potassium isoamyl
xanthate which is essentially similar to the one described above. An interesting
feature of Gomez’s work is his study of the kinetics of the reaction leading to the
formation of xanthate. The value of the reaction velocity constant was found to be
bimolecular reaction rate law.
CS2
+ KOH
HOCS2K + C2H5OH
HOCS2K
C2H5OCS2K + H2O
The preparation of large number of compounds belonging to O-alkyl-S-alkyl
xanthates i.e. xanthic ester has been reviewed by Bulmer and Mann.181 The general
method is to treat sodium or potassium alkylxanthates with an alkyl halide.
38
INTRODUCTION
ROCS2K
+
ROCS2R'
R'I
+
KI
(R and R' = CH3, C2H5 or C3H7)
A series of the compounds called sym-dithiocarbonates having the general
formula O=C(SR’)SR, which are isomeric with xanthic acid ester, are also known.
These are prepared by the action of phosgene on sodium alkyl sulfides or by the acid
hydrolysis of alkyl thiocyanates.50
+
RSNa
R'SNa
+
RSCOSR'
COCl2
+
2NaCl
(R and R' = CH3, C2H5 or C3H7)
A dithiocarbonates with identical alkyl group may also be prepared by the acid
hydrolysis of alkyl thiocyanide such as:
2RSCN
+
(RS)2CO
3H2O
+
CO2
+
2NH3
Among the derivatives of xanthates, dixanthogens, which are formed by the
oxidation of xanthates, are considered to be an important class of compounds.50
Oxidation
2ROCS2K
[ROCS2]2
+
2e
The role of dixanthogens in conjunction with xanthates in the flotation of
sulfide minerals has attracted considerable attention. In view of this, the formation of
dixanthogens under various conditions has been explored.50 Dixanthogens are also
synonymously called as O-alkyl-thiocarbonic acid disulfide, bis-alkyl xanthogen and
O,O-dialkyl ester of bis-thioformic acid. The quantitative reaction between potassium
xanthates and iodine in aqueous solution can be employed to prepare dixanthogen.
2ROCS2K
+
I2
2KI
+
[ROCS2]2
Gurvich and Belora182 have also reported the synthesis of dixanthogens by the
oxidation of xanthate ions using nitrous acid. It has also been found that dixanthogens
are readily reduced to xanthates by nascent hydrogen generated in alkaline medium by
the action of a metal such as zinc.50
39
INTRODUCTION
S
S
S S
C
C
+
OR
OR
SNa
2H + 2NaOH
2S
+
C
2H2O
OR
The first successful synthesis of a variety of metal arylxanthates has been
achieved by oxidation of the metal xanthates to the xanthogen by Fackler et al.184 It is
interesting to note that the reaction of organic disulfides with metal halides can
produce a rupture of the S—S bond to give the mercaptide complex of the oxidized
metal.79, 183-184
Oxidation
2M(S2COR)
[ROC(S)S]2
+
2M+
+
2e
Pyrolysis of some S-methyl xanthate esters involved the formation of
dithiolcarbonates e.g. pyrolysis of the xanthates ester of 1-cyclopropylethanol;
Overberger and Borchert185 have reported that it yields of 45% of olefins and 34% of
dithiolcarbonates, of which the major component was identified as 1-cyclopropylethyl
dithiolcarbonate. A concerted four membered cyclic transition state was suggested
(Scheme 1.5).
H3C
CH3
O
CSCH3
C
Pyrolysis
C
SCSH3
S
H
H
Scheme 1.5: Pyrolysis of the 1-cyclopropylethylxanthate
Laakso186 has reported no olefin formation in the study of the pyrolysis of
some neopentylxanthate esters (Scheme 1.6).
(CH3)3C
CH
C(CH3)3
(CH3)3C
CH
C(CH3)3
Pyrolysis
OCHSCH3
S
OCHSCH3
O
Scheme 1.6: Pyrolysis of neopentylxanthate esters
Metal xanthates are extensively used as pharmaceuticals, fungicides,
pesticides,50 rubber accelerators,85-86 corrosion inhibitiors,53 agricultural reagents87-88
and quite recently in therapy for HIV infections,187-188,79 Their synthetic and structural
chemistry witnessed increased attention through the pioneering work of Hoskins and
40
INTRODUCTION
Winter189 and lately, extensive structural analyses performed by Tiekink and Haiduc,
189b-190
which showed that these can coordinate to metal atoms in a monodentate (A),
isobidentate (B) or anisobidentate (C). Bimetallic bridging also occurs through sulfur
atoms (D) and (E), but occasionally the oxygen atom may become involved (F). In
rare cases additional metal-oxygen atom may become involved (G).190 (Figure 1.30).
R
R
O
C
S
R
R
O
O
C
S
C
S
M
(A)
R
S
S
C
S
M
M
(B)
(C)
S
M
C
O
C
S
M
M
M
(D)
O
S
S
R
R
O
O
C
M
S
S
S
M
S
M
(E)
(G)
(F)
Figure 1.30: Various possible coordination patterns of xanthate ligands
The following resonating structures (I-IV) have been suggested by Haiduc et
al. based on the infrared absorption spectra of the xanthates (Figure 1.31).
S
R
C
S
S
O
R
C
O
S
I
S
R
C
O
S
II
S
R
C
O
S
III
IV
Figure 1.31: Resonating structures of xanthate ligand
Monoalkyl xanthates (I) are rapidly hydrolyzed in dilute acid and the ratelimiting step is a spontaneous heterolysis of the undissociated acid (II). The zwitterion
(III) may be an intermediate formed in low concentration or a proton transfer from
sulfur to oxygen could be concerted with C—O bond breaking. The protonated ester
(IV) is formed at low pH which is unreactive, unless the group R could be eliminated
readily as a carbocation.191 (Scheme 1.7)
41
INTRODUCTION
RO CS2- +
I
H+
ROCS2H
II
R
+
O
III
H
CS2-
slow
[ROCS2H2]+
IV
Scheme 1.7
ROH
+
CS2
The use of monoalkyl xanthates in ore flotation and cellulose processing
stimulated work on their hydrolysis under homogeneous condition. In addition alkyl
hydrolysis is often an undesired reaction which wastes material, so that its micellar
inhibition could be useful.
Zn(II) and Cd(II) chelates with alkylxanthate ions (ROCS2)- are known to be
precursors of metal sulfides. The chelates derive from ROCS2- ions incorporating
branched alkyl groups are most attractive.192-198
M(nL)(S2COR)2
ROCS2K + nL + MCl2
(M = Zn or Cd; L = 2,2'- bipyridyl for n = 1, pyridine for n = 2 and R = Et, iPr or iBu)
[Zn(S2COEt)2] + nL
[Zn(S2COEt)2].nL
(n = 1, L = PPh3, P(O-tolyl)3 or P(OH2Ph)3; n = 2, L = dppe)
(b)
(a)
n
Figure 1.32: Molecular structure of Cd[S2CO( C4H9)]2.C10H8N2 (a) and
[Cd(C5H5N)2(S2COnC4H9)2] (b)
The xanthates of zinc like Zn(S2COR)2 (R = C2H5, nC3H7, iC3H7) were
prepared in high yield from the reaction of Zn(NO3)2.6H2O with potassium xanthates.
Zn(NO3)2.6H2O + 2 KS2COR
Zn(S2COR)2 + 2KNO3
(R = C2H5, iC3H7, nC3H7)
42
INTRODUCTION
The structure of Zn(S2COnC3H7)2 features [–Zn–S–C–S–]4 16-membered rings
that share two corners with adjacent rings leading to the formation of a chain. This
contrasts the situation in closely related Zn(S2COiC3H7)2 which displays isolated 16membered rings.199
Zn(II) complexes of general formula [Zn(S2COC2H5)2.L] [L =
(Hpz),
3,5-dimethylpyrazole
(Hdmpz),
2-pyridylamine(pyam),
pyrazole
phenyl
2-
pyridylamine (phpyam), 2,2’-dipyridylamine (dpyam), 1,4-pyrazine (pyr)] have also
been reported.200
ZnPhen(S2COC2H5)
(1) and Zn(2,2’-bipy)(S2COC4H11)
(2) mixed-ligand
complexes have been synthesized by the following procedure.201
2C2H5OCS2K + Zn(CH3COO)2.4H2O + L
H2O
[Zn (C2H5OCS2)2.L]
-2CH3COOK
L = Phen or 2,2'-bipy
Mixed-ligand compounds ZnL(ROCS2)2 [R =
i
C3H7,
i
C4H9; L = 2,2’-
bipyridyl (2,2'-bipy), 1,10-phenanthroline (Phen)].202 The volatile complex Zn(2,2'bipy)(iC3H7OCS2)2 was used as a precursor to obtain electroluminescent ZnS:Mn
films.192 According to XRD data, the compound Zn(Phen)(iC4H9OCS2)2 is
monomeric and coordination number of zinc is six. It was found that the behavior
of alkylxanthate ligands in mixed-ligand complexes of zinc(II) is more complex.203
Mixed-ligand complex ZnPhen(iC3H7OCS2)2 have been isolated and prepared
by the above procedure.204
Figure 1.33: Molecular structure of ZnPhen(iC3H7OCS2)2
43
INTRODUCTION
The structure determination for a series of compounds ZnPhen(ROCS2)2,
where R = Et, iPr, iBu the coordination number of the Zn2+ ion is 5 (R = Et) and 6 (R
= iPr and iBu). The structure of the Et, iPr, and iBu alkyl groups changing along with
the number of carbon atoms. Comparison of the data obtained for ZnPhen(nBuOCS2)2
and ZnPhen(ROCS2)2 (R = Et, iPr, iBu) permits one to conclude that the coordination
number is related to the nature of R. Evidently, when the complex has unbranched Et
and nBu groups, the coordination number is 5 (ZnN2S3 unit) and when R = iBu, the
compound has coordination number 6 with an N2S4 coordination polyhedron shaped
like a distorted octahedron.205
Monomeric, five-coordinated bis(ethylxanthato)Zn(phosphine) complexes
[phosphine = PPh3, P(o-tolyl)3, P(CH2Ph)3] have been synthesized by addition of the
phosphine ligand (1:1 molar ratio) to CH2Cl2 solutions of [Zn(S2COEt)2]. Bidentate
ligands Ph2PCH2CH2PPh2 (dppe) and Ph2P(CH2)4PPh2 (dppb) reacted in a 1:2 molar
ratio to form dinuclear phosphine-bridged complexes. The Zn-P bonds are very labile
and are probably broken in solution. The characterization of all the compounds has
been carried out by elemental analyses and spectroscopic methods. The structure of
binuclear
[(S2COEt)2Zn(l-dppb)Zn(S2COEt)2]
was
determined
by
X-ray
crystallography which shows a distorted trigonal bipyramidal environment for the Zn
atoms, formed by two chelating xanthate and a bridging dppb ligand.76
Figure 1.34: Structure of [{(S2COEt)2Zn}2(-dppb)]
Steric control over supramolecular aggregation is demonstrated for a series of
adducts formed between Zn(S2COR)2 (R = Et, nBu or Cy) and L (L = trans-1,2-bis(4pyridyl)ethylene). The adducts were obtained from refluxing the zinc xanthate with
either 1 or 2 stoichiometric amount of trans-1,2-bis(4-pyridyl)ethylene in CHCl3
solution. Recently structures of these have been determined. Supramolecular zigzag
44
INTRODUCTION
polymers are found when R = Et or nBu, but only bimetallic aggregates could be
formed when R = Cy.206
Mixed ligand complexes of Zn(II) and Cd(II) with alkyl xanthates and primary
ligands and 2,2’-bipyridyl as secondary ligands have also been synthesized and
characterized.207
Cadmium ethylxanthates corresponding to [Cd(S2COEt)2] have been
synthesized and used as precursor for the synthesis of CdS nanoparticles capped with
tri-n-octylphosphine oxide (TOPO). This precursor is easy to synthesize, air stable
and pyrolyses cleanly to give good yields.208-209
The
structure
of
bis(O-isopropyldithiocarbonato)cadmium(II),
[Cd(C4H7OCS2)2], comprises an interconnected network of 16-membered [–Cd–S–C–
S–]4 rings that arises from the presence of bidentate bridging ligands.210
The insertion of CS2 into the M-OH bond of [((TPA)M)2(l-OH)2](ClO4)2 (M =
Zn, Cd) in alcoholic media results in O-alkyl dithiocarbonate zinc and cadmium
complexes as shown in Scheme 1.8. These complexes were characterized by
spectroscopic methods and by X-ray crystallography.211
.
Scheme 1.8: Zn(II) and Cd(II) alkyl dithiocarbonate and thiocarbonate
complexes where M = Zn(II) and Cd(II); X = ClO4, E = S
Mercury xanthates corresponding to [Hg(S2COR)2] (R = Me, Et and iPr) have
been synthesized and structurally established.212 The remarkable structural diversity
for these compounds is fascinating and defies conventional explanation i.e. change in
structure. One is bidentate bridging; linking neighbouring mercury atom into a helical
chain and the other is monodentate as the pendant sulfur atom is not involved in
coordination to mercury. The coordination geometry is one based on a T-shape. The
16-membered
–[Hg-S-CS-]4 rings of Hg(S2COEt)2 persist in the structure of
45
INTRODUCTION
Hg(S2COiPr)2. In this structure there is both chelating and bidentate bridging xanthate
ligands.213
The cross-polarization magic angle
13
C NMR spectra of a
series of
bis(xanthato) complexes of mercury(II) [Hg(S2COR)2], R = Me, Et, nPr and iPr are
reported. The spectra correlate well with the known crystal structures of the R =
Me, Et and iPr compounds and with that of the R = nPr derivative for which a
single-crystal X-ray diffraction study is also reported. The X-ray analysis of
[Hg(S2COnPr)2]n, shows that this compound adopts a two-dimensional structure
comprised of connected 16-membered rings which arise as a result of bridging npropylxanthate ligands.214
Figure 1.35: Molecular structure of [Hg(S2COnPr)2]n
Methylmercury(II) xanthates, MeHgS(S)COR, with R = Et, iPr and CH2Ph,
form unidimensional, supramolecular self-assemled, tape-like arrays in the solid state,
based upon Hg···S intermolecular secondary interactions. In the compounds with R =
Et and iPr the individual molecules form double chains (tapes) weakly interacting
with neighbouring arrays.215
46
INTRODUCTION
1.2: SCOPE AND OBJECTIVES
The present work is supposed to have great relevance in the development of chemistry
of compounds with metal-sulfur linkages i.e. M—S—C linkages. The exploration of
simpler pathways of synthesis can enhance the utility of the technique for the
preparation compounds. The development of chemistry regarding the bonding
patterns may provide a thorough understanding of the bonding patterns in this subject.
In addition, these compounds may also find their utility in various fields like material
development, nanoparticles, medicine, floating agents, analytical application etc.
Literature survey revealed that a lot of work has been done on O-alkyl
dithiocarbonate ligands (alkylxanthates)64-72 but only a few reports are available in
which the synthesis and characterization of O-aryldithiocarbonate has been
reported.80,
216
In particular, very scanty information are available pertaining to the
cresyl(tolyl)/benzyl dithiocarbonates and their complexes. Moreover, no work has
been reported with elements of 12th group tolyl/benzyl dithiocarbonate so far. Hence,
no general information and systematic reports are available regarding the synthesis
and characterization of (o-, m- and p-tolyl)/benzyl dithiocarbonates. It is evident that
the metallo-organic chemistry using dithiocarbonate ligands appear to be a promising
area of research work owing to the versatile applications of these compounds. As
indicated in the preceding section about the versatile utility in various fields and in
academia makes this area of research still very potential. In view of expanding
theoretical knowledge and utilities, the paucity of research work in this field is one of
the motifs to make the explorations during the present course of investigations. In
view of this, it was thought worthy to investigate the synthesis and characterization of
(o-, m- and p-tolyl)/benzyl dithiocarbonate ligands and their complexes with the last
group of transition metal series i.e., particularly, zinc(II), cadmium(II) and
mercury(II) along with their biological activity.
The present research work is interplay between oriented synthesis of the
molecules, utility and a thorough understanding of chemical bonding in
dithiocarbonate derivatives. It is also proposed to investigate the biological activity of
the ligands and some of the newly synthesized complexes since cresols and the
compounds containing C-S linkage are well known to possess potential bio-activity.
47
INTRODUCTION
The following type of complexes of tolyl/benzyl dithiocarbonates of Zn(II),
Cd(II) and Hg(II) have been synthesized, characterized and their biological activity
(antifungal, antibacterial and cytotoxicity) have been investigated during the present
course of investigations.
1. New (ortho–, meta– and para–tolyl)/benzyl dithiocarbonate ligands
2. Sodium O,O’-neopentylenephosphorodithioate ligand
3. Disulfides
of
(ortho–,
meta–
and
para–tolyl)/benzyl
dithiocarbonates
4. Dithiocarbonate
derivatives
of
zinc(II),
cadmium(II)
and
mercury(II)
5. Adducts
of
bis-[(ortho–,
tolyl)/benzyldithiocarbonates]
of
meta–
zinc(II),
and
cadmium(II)
para–
and
mercury(II) with nitrogen and phosphorus donors
6. Biological activity
48
EXPERIMENTAL
2.1: GENERAL PROCEDURES AND EXPERIMENTAL TECHNIQUES
2.1.1: Apparatus
Some of the reactants as well as products described in this thesis are susceptible to
hydrolysis. So in view of the hydrolysable nature of the complexes and precursors,
stringent precautions were taken to exclude moisture from all chemicals and
glassware by applying standard Schlenk techniques. The glass apparatus used were
fitted with standard quit-fit joints. The required glassware were well washed with
alkali or acid followed by water then rinsed with alcohol/acetone and finally dried in
an electric oven at 120-160 C for 3-6 hours prior to each experiment. The glassware
was then cooled either in desiccators or by using guard tubes filled with fused
anhydrous calcium chloride. Towers filled with fused anhydrous calcium chloride
were used wherever required. Special weighing tubes, weighing pipettes and transfer
tubes were got fabricated with standard joints and were used for handling all reactants
as well as products. Syringes (Aldrich) of various capacities were used for
transferring liquid chemicals.
Fractionations were carried out on columns of varying lengths packed with
rasching rings and fitted with ratio head. Usually, the solvent was removed under
reduced pressure; cold traps of conventional design were used to trap the solvents and
also to prevent either back diffusion or passage of solvent vapours into oil pump. All
manipulations were carried out strictly under dry nitrogen atmosphere. Melting points
of compounds were determined in a sealed tube on melting point apparatus.
2.1.2: Materials
Toluene (Thomas Baker and Glaxo, b.p. 110 C) and n-hexane (Thomas Baker, b.p.
68-69 C) were dried over sodium wire for a couple of days then refluxed for 8-10
hours in presence of benzophenone indicator and distilled after an appearance of deep
blue color. Cresols (ortho-, meta- and para-) and benzylalcohal were purified by
distillation whereas all other chemicals were used as such. Chloroform (Thomas
Baker, b.p. 61 C) and methylene chloride (Spectrochem, b.p. 56 C) were dried by
refluxing and fractionating over CaCl2 and Al(OiPr)3 and finally over P2O5. Ethanol
(commercial, b.p. 78 C) was refluxed over freshly ignited calcium oxide for 24 hours
and distilled. Distillate was then fractioned over sodium ethoxide and magnesium
49
EXPERIMENTAL
ethoxide, successively. Finally, traces of moisture were removed by fractionation in
presence of small amount of benzene. Carbon tetrachloride (Thomas Baker, b.p. 77
C) was dried by fractionating over fused CaCl2 and finally over P2O5. Ether (Thomas
Baker, b.p. 34.6 C) was dried over sodium wire and distilled. The details of
chemicals procured during the present work are given below:
S. No.
Chemical
1.
Zinc Chloride
b. p. / m. p. (C)
Make
293
Merck
568
Merck
277
Merck
48
Spectrochem
79
Spectrochem
289
Spectrochem
80.1
Himedia
110.6
Qualigen
97
Sigma Aldrich
40
Rankem
65-67
Thomas Baker
64
Thomas baker
(ZnCl2)
2.
Cadmium Chloride
(CdCl2)
3.
Mercury Chloride
(HgCl2)
4.
Benzophenone
(C6H5COC6H5)
5.
Thionyl Chloride
(SOCl2)
6.
Phosphorus Pentasulfide
(P2S5)
7.
Benzene
(C6H6)
8.
Toluene
(C6H5CH3)
9.
Sodium metal
(Na)
10.
Dichloro methane
(CH2Cl2)
11.
Tetrahydrofuran
(C4H8O)
12.
Ethanol
(CH3OH)
50
EXPERIMENTAL
13.
Benzene
79.1
Qualigen
68-70
Qualigen
113
Thomas Baker
60
Thomas Baker
191
Thomas Baker
203
Thomas Baker
202
Thomas Baker
205.3
Alfa Ascer
200
Merck
79-81
Thomas Baker
115-116
Thomas Baker
70-73
Merck
420
Himedia
249
Himedia
124-130
Thomas Baker
70-75
Thomas Baker
(C6H6)
14.
n-hexane
(CH3(CH2)4CH3)
15.
Iodine
(I2)
16.
Chloroform
(CHCl3)
17.
o-Cresol
(o-CH3C6H4OH)
18.
m-Cresol
(m-CH3C6H4OH)
19.
p-Cresol
(p-CH3C6H4OH)
20.
Benzyl alcohol
(C6H5CH2OH)
21.
Pyridine
(C5H5N)
22.
Triphenylphosphine
P (C6H5)3
23.
1,10-Phenanthroline
(N2C12H8)
24.
2,2’-bipyridyl
(N2C10H8)
25.
Potassium hydroxide (GR)
(KOH)
26.
Potassium permanganate (GR)
(KMnO4)
27.
Neopentylene glycol
[HOCH2C(CH3)2CH2OH]
28.
Sodium isopropoxide
(CH3)2CONa
51
EXPERIMENTAL
29.
Acetone
56
Himedia
444
Merck
170
Himedia
85-110
Himedia
179-180
Sigma Aldrich
155
Himedia
109
Merck
118
Merck
[(CH3)2CO]
30.
Silver Nitrate
(AgNO3)
31.
Ammonium thiocyanate
(NH4SCN)
32.
Hydrochloric acid
(HCl)
33.
Methyl red
(C15H15N3O2)
34.
Diammonium phosphate
(NH4)2HPO4
35.
Thionalide
(C12H11NOS)
36.
Acetic acid
(CH3COOH)
Note: Due to the poisonous nature of CdCl2 and HgCl2 all precautions were taken
such as fuming hood, laboratory spectacle, hand gloves etc. were the integral
component during experimental manipulations.
52
EXPERIMENTAL
2.1.3: Analytical Methods
Analyses of some of the elements present in the compounds were carried out by the
methods217 as mentioned below.
 Sulfur
Sulfur was estimated by Messenger’s method in which weighed amount of the
compound (0.10-0.30 g) was taken in a 250 ml round bottom flask. Into this
potassium hydroxide pellets, KOH, (1.00 g) and potassium permanganate, KMnO4,
(2.50 g) were added along with ~100 ml of distilled water. The contents were refluxed
for about 6 hours to ensure the complete oxidation of sulfur. It was then cooled and
followed by an addition of ~ 25 ml concentrated hydrochloric acid (A.R.) to dissolve
brown color mass. The contents were heated for half an hour to get a clear colourless
solution. The hot solution was filtered off and the filtrate was diluted up to 250 ml
with distilled water. Now 5% barium chloride solution was added slowly under hot
conditions with stirring till white precipitate of barium sulfate was obtained. The
precipitate of BaSO4 was allowed to settle down and then filtered through an ashless
filter paper (Whatman No. 42). The precipitate was washed repeatedly with water to
remove chloride ions and then dried. It was then finally ignited in weighed silica
crucible to weigh it as barium sulfate; the percentage of sulfur in the compound was
calculated using the following formula.
32.06 X Weight of precipitate
% age of Sulfur =
X 100
233.5
X Weight of compound
53
EXPERIMENTAL
 Zinc
Zinc was estimated as zinc ammonium phosphate. To the solution containing about 0.1
g of zinc compound and 1 ml of concentrated hydrochloric acid, add a few drops of
methyl red indicator and neutralize by the addition of dilute ammonia solution (1:1).
Dilute to 150 ml, heat nearly to boiling and treat with 25 ml of 10% of diammonium
phosphate solution added slowly from a pipette, flocculent precipitate of zinc phosphate
form first. Heat on a water bath for 30-60 minutes, until the solution is at room
temperature, filter through a weighed sintered glass crucible, wash with 1%
diammonium hydrogen phosphate solution until the precipitates are free from chlorides.
Finally, wash with neutral 50% ethanol to remove the phosphate solution. Dry to
constant weight at 100-105 C for about 1 hour and then weigh it as ZnNH4PO4.
65.40 X Weight of precipitate
% age of Zinc =
X 100
178.41
X Weight of compound
 Cadmium
Cadmium was estimated by the pyridine method. The solution contained about 0.1 g
of cadmium compound and should be feebly acid. Add 0.5-1.0 g A.R. ammonium
thiocyanate, stir, and heat to boil and then treat the solution with 1 ml of pure pyridine
drop wise with constant stirring. The complex slowly separates out as the solution
cools. Filter the cold solution through a weighed sintered glass crucible. Wash the
precipitates four-five times with water containing 0.3 g of NH4SCN and 0.5 g of
pyridine. Dry the precipitates in a vacuum desiccator for 10-15 minutes and weigh.
Repeat the drying until constant weight was obtained. And weigh it as
[Cd(C5H5N)2(SCN)2].
112.41 X Weight of precipitate
% age of Cadmium =
X 100
321.68
X Weight of compound
54
EXPERIMENTAL
 Mercury
Mercury was estimated as mercury(II)thionalide. The solution cointainined about 0.1
g of mercury compound and is slightly acidic in nature. Heat the solution to about 8085 C and then added with constant stirring, a threefold excess of a 1% solution of
thionalide in acetic acid. The precipitate coagulates upon stirring. Filter the hot
solution through a sintered glass crucible which has been preheated by pouring hot
water through it (The use of warm crucible is essential; the separation of thionalide in
the pores of the sintered plate of the crucible, which would render filtration difficult,
is thus avoided.) wash with hot water until free from acid and dry to attain constant
weight at 105 C. Weigh it as Hg(C12H10ONS)2.
200.59 X Weight of precipitate
% age of Mercury =
X 100
633.14
X Weight of compound
55
EXPERIMENTAL
2.1.4: Instrumental Methods
 Infrared Spectra
Infrared spectra were recorded in the range of 4000-200 cm-1 on a Perkin ElmerSpectrum 400-IFTIR spectrophotometer. The IR spectra were recorded in KBr
pallets. The IR spectral analyses were recorded at Sophisticated and Analytical
Instrumentation Facility (SAIF), Punjab University, Chandigarh.
 Elemental Analyses (C, H, N and S)
Elemental analyses (C, H, N and S) were carried out on Vario EL III and CHNS932 Leco Elemental Analyzer in Indian Institute of Integrative Medicine (IIIM),
Jammu.
 Nuclear Magnetic Resonance Spectra
(a) 1H NMR Spectra
Proton magnetic resonance spectra was recorded in CDCl3 on a Bruker Avance II
and III 400 (400 MHz) using TMS as internal reference and measured in ppm.
(b)
13
C NMR Spectra
13
C spectral studies have also been carried out on a Bruker Avance II and III 400
(400 MHz) spectrometer using TMS as internal reference and measured in ppm.
(c)
31
P NMR Spectra
31
P NMR spectra of the compounds were recorded in CDCl3 using H3PO4 (85%) as
external reference on Bruker Avance II and III 400 (400 MHz) spectrometer and
measured in ppm.
All the NMR studies (1H,
13
C and
31
P) have been done at Sophisticated and
Analytical Instrumentation Facility (SAIF), Punjab University, Chandigarh and
Department of Chemistry, University of Jammu, Jammu (PURSE program).
56
EXPERIMENTAL
 Mass Spectra
Mass spectra of the compounds were recorded on ESQUIRE3000_00037
spectrophotometer from Indian Institute of Integrative Medicine (IIIM), Jammu.
 Thermogravimetrical Analysis (TGA)
The thermogram was analyzed by using Perkin Elmer, diamond TG/DTA
instrument. The thermogram was recorded in the temperature range from 30 C to
1000 C under nitrogen atmosphere from National Chemical Lab (NCL), Pune.
 Scanning Electron Microscopy (SEM)
SEM studies were performed with a Zeiss EVO 50 instrument having magnification
range 5x to 1,000,000x and at an accelerating voltage of 0.2 to 30 kV at the Indian
Institute of Technology (IIT), Delhi.
 Cyclic voltammetry (CV)
The cyclic voltammograms were recorded on Autolab (Metrohm). The potential is
applied between the reference electrode (Ag/AgCl) and the working electrode (Gold
electrode) and the current is measured between the working electrode and the counter
electrode (Platinum wire). 0.1 M Phosphate buffer solution (pH = 7.0) was used.
Department of Chemistry, University of Jammu, Jammu.
57
EXPERIMENTAL
2.2: SYNTHESES OF LIGANDS
2.2.1: Synthesis of o-CH3C6H4OCS2Na (1)
To a toluene solution (∼40 ml) of freshly distilled o-cresol (2.00 g, 18.50 mmol) was
added sodium metal (0.43 g, 18.50 mmol). The contents were refluxed for 3 hours
until white precipitates started appearing and the refluxing was continued until
sodium metal was completely dissolved. The contents were cooled using an ice bath
at 0 – 5 C. Subsequently, CS2 was added to the reaction mixture dropwise over a
period of 30 minutes with constant stirring. The contents were further stirred for 3
hours during which the color changed from white to yellow. Compound 1 was
isolated by filtration using a funnel fitted with a G-4 sintered disc. The salt so
obtained was washed with n-hexane and finally dried under reduced pressure that
resulted in the formation of o-CH3C6H4OCS2Na (1) as pale yellow solid in 65% yield.
The same procedure was followed to prepare m- and p-CH3C6H4OCS2Na (2-3)
and C6H5CH2OCS2Na (4). The synthetic and analytical data for these ligands (1-4) are
given in Table 2.1.
2.2.2: Synthesis of neopentylenedithiophosphate ligand (5)
Phosphorus pentasulfide, P2S5 (5.33 g, 23.68 mmol) was added in several installments
to a benzene solution (~50 ml) of neopentyl glycol, (CH3)2C(CH2OH)2 (5.00 g, 48.08
mmol) with constant stirring. All P2S5 was dissolved in about 4 hours while stirring at
~50C. Now, this was added to benzene suspension (~20 ml) of sodium isopropoxide
(3.94 g, 48.05 mmol), which was freshly prepared. Now the contents were stirred
overnight, which resulted in the formation of white precipitate of sodium
neopentylenephosphorodithioate. The compound OCH2C(CH3)2CH2OPS2Na (5) was
isolated by filtration using alkoxy funnel fitted with G-4 sintered disc and on
subsequent drying under reduced pressure. The resultant compound 5 was obtained in
80% yield.
The synthetic and analytical data of ligand 5 are given in the Table 2.1.
58
Table 2.1: Synthetic and analytical data of sodium salt of (ortho-, meta- and para-tolyl)/benzyldithiocarbonates (1-4) and
neopentylenedithiophosphate (5)
S.
No.
Reactants
A*
g (mmol)
A**
Molar
Ratio
Product
(physical state)
Yield
(%)
M.P.
Analysis %
found (Calcd.)
C
M
C
1.
2.
3.
4.
5.
1.42
0.43
(18.50)
(18.50)
(18.50)
2.00
1.42
0.43
(18.50)
(18.50)
(18.50)
2.00
1.42
0.43
(18.50)
(18.50)
(18.50)
2.00
1.42
0.43
(18.50)
(18.50)
(18.50)
5.00
5.33
(48.08)
(23.68)
3.94
1:1:1
(o-CH3C6H4OCS2)Na
65
Pale yellow solid
1:1:1
(m-CH3C6H4OCS2)Na
67
Pale yellow solid
1:1:1
(p-CH3C6H4OCS2)Na
70
Pale yellow solid
1:1:1
(C6H5CH2OCS2)Na
72
Pale yellow solid
2:1:2
(48.05)
197
197
196
186
80
(OCH2C(CH3)2CH2OPS2)Na
192
S
45.96
3.31
30.80
(46.42)
(3.38)
(30.90)
45.98
3.29
30.79
(46.42)
(3.38)
(30.90)
45.90
3.21
30.74
(46.42)
(3.38)
(30.90)
45.91
3.30
30.63
(46.42)
(3.38)
(30.90)
27.01
4.34
29.00
(27.27)
(4.58)
(29.12)
White solid
A* = o-CH3C6H4OH, (1), m-CH3C6H4OH, (2), p-CH3C6H4OH, (3), C6H5CH2OH (4), (HOCH2)(CH3)2C(CH2OH) (5); A** = CS2 (1-4)
59
and P2S5 (5); M = Na, (1-4) and iPrONa, (5)
EXPERIMENTAL
2.00
H
Table 2.2: Synthetic and analytical data of disulfides of (ortho–, meta– and para–tolyl)/benzylthiocarbonate ligands (6-9)
S. No.
Reactants
Ligand
g (mmol)
6.
7.
8.
9.
I2
Molar
Product
Yield
Analyses (%)
Ratio
(Physical State)
(%)
Found (Calcd.)
g (mmol)
(o-CH3C6H4OCS2)Na
0.38
1.00 (3.0)
(1.5)
(m-CH3C6H4OCS2)Na
0.38
1.00 (3.0)
(1.5)
(p-CH3C6H4OCS2)Na
0.38
1.00 (3.0)
(1.5)
(C6H5CH2OCS2)Na
0.38
1.00 (3.0)
(1.5)
2:1
[(o-CH3C6H4OCS2)2]
80
Yellow viscous
2:1
[(m-CH3C6H4OCS2)2]
[(p-CH3C6H4OCS2)2]
78
[(C6H5CH2OCS2)2]
Yellow viscous
S
52.30
3.61
34.70
52.28
3.59
34.68
(52.43) (3.85) (34.99)
77
Yellow viscous
2:1
H
(52.43) (3.85) (34.99)
Yellow viscous
2:1
C
52.30
3.52
34.70
(52.43) (3.85) (34.99)
78
52.36
3.56
34.65
(52.43) (3.85) (34.99)
EXPERIMENTAL
60
EXPERIMENTAL
2.3: SYNTHESIS OF NEW COMPOUNDS
2.3.1: Synthesis of [(o-CH3C6H4OCS2)2] (6)
To a chloroform suspension (~30 ml) of sodium salt of o-tolyldithiocarbonate, oCH3C6H4OCS2Na, (1.00 g, 3.00 mmol) was added dropwise a chloroform solution of
iodine with constant stirring at room temperature. As soon as the iodine solution was
added the dark pink color of the iodine disappeared due to the oxidation of sodium salt of
o-tolyldithiocarbonate. The iodine solution was added continuously till a light pink colour
appeared in the reaction. The reaction mixture was then stirred for 4-5 hours at room
temperature for the sake of completion of the reaction. The precipitates of sodium iodide
were filtered off using alkoxy funnel fitted with G-4 sintered disc and volatiles were
removed from the filtrate under reduced pressure and the desired product [(oCH3C6H4OCS2)2] (6) was obtained from the filtrate as yellow viscous compound in 80%
yield.
Similar methodology was followed for the synthesis of analogous compounds (69). The synthetic and analytical data for these compounds 6-9 are given in Table 2.2.
2.3.2: Synthesis of [(o-CH3C6H4OCS2)2Zn] (10)
To a solution of sodium salt of o-tolyldithiocarbonate (1.00 g, 4.82 mmol) in ~20 ml
distilled water was added dropwise solution of zinc(II)chloride (0.33 g, 2.42 mmol)
dissolved in 20 ml distilled water with constant stirring at room temperature. White
precipitates were formed immediately and the mixture was stirred for further 45 minutes.
The precipitated white complex was filtered off by G-4 sintered funnel. The precipitates
were washed first with water followed by petroleum ether three times followed by drying
under in vacuo over P2O5, which yielded the complex (10) as white solid in 75% yield.
This methodology was applied to synthesize all other complexes (10-21) using
stoichiometric weights. The relevant synthetic and analytical data for all the complexes
are given in Table 2.3.
61
EXPERIMENTAL
2.3.3: Synthesis of [(o-CH3C6H4OCS2)Zn{S2POCH2C(CH3)2CH2O}]
(22)
To an aqueous solution (~ 20 ml) of sodium salt of o-tolyldithiocarbonate (1.00 g, 4.84
mmol) was added aqueous solution of neopentylene ligand (1.06 g, 4.84 mmol). Now an
aqueous solution of zinc chloride (0.66 g, 4.84 mmol) was added to this mixture with
constant at room temperature. Formation of white precipitates was observed immediately.
The precipitated white complex was filtered off by G-4 sintered funnel. The precipitates
were washed first with water followed by petroleum ether three times followed by drying
under
in
vacuo
over
P2O5,
which
yielded
the
desired
product
[(o-
CH3C6H4OCS2)Zn{S2POCH2C(CH3)2CH2O}] (22) as white solid in 72% yield.
The same procedure and stoichiometry was followed for the synthesis of the
analogous compounds (22-25). The synthetic and analytical data for these compounds
(22-33) are given in Table 2.4.
62
Table 2.3: Synthetic and analytical data of (ortho-, meta- and para-tolyl)/benzyldithiocarbonates of zinc(II), cadmium(II)
and mercury(II) (10-21)
S. No.
10.
11.
12.
13.
14.
15.
Molar
*ArOCS2Na MCl2
ratio
1.00
0.33
(4.82)
(2.42)
1.00
0.33
(4.82)
(2.42)
1.00
0.33
(4.82)
(2.42)
1.00
0.33
(4.82)
(2.42)
1.00
0.44
(4.84)
(2.42)
1.00
0.44
(4.84)
(2.42)
1.00
0.44
(4.84)
(2.42)
2:1
Product
(Physical State)
[(o-CH3C6H4OCS2)2Zn]
M.P. (C)
(dec.)
203
Yield
[(m-CH3C6H4OCS2)2Zn]
201
75
78
(White solid)
2:1
[(p-CH3C6H4OCS2)2Zn]
204
74
(White solid)
2:1
[(C6H5CH2OCS2)2Zn]
199
77
(White solid)
2:1
[(o-CH3C6H4OCS2)2Cd]
180
82
(White solid)
2:1
[(m-CH3C6H4OCS2)2Cd]
182
76
(White solid)
2:1
[(p-CH3C6H4OCS2)2Cd]
(White solid)
179
Found (Calcd.)
(%)
(White solid)
2:1
Analyses (%)
79
C
H
M
S
44.16
3.21
15.01
29.59
(44.49)
(3.27)
(15.14)
(29.69)
44.13
3.23
15.11
29.51
(44.49)
(3.27)
(15.14)
(29.69)
44.36
3.25
15.07
29.54
(44.49)
(3.27)
(15.14)
(29.69)
44.14
3.22
15.09
29.57
(44.49)
(3.27)
(15.14)
(29.69)
40.11
2.56
23.30
26.55
(40.12)
(2.95)
(23.47)
(26.78)
40.09
2.36
23.37
26.46
(40.12)
(2.95)
(23.47)
(26.78)
40.06
2.62
23.39
26.56
(40.12)
(2.95)
(23.47)
(26.78)
63
EXPERIMENTAL
16.
Reactants g(mmol)
17.
18.
19.
20.
21.
1.00
0.44
(4.84)
(2.42)
1.00
0.65
(4.84)
(2.42)
1.00
0.65
(4.84)
(2.42)
1.00
0.65
(4.84)
(2.42)
1.00
0.65
(4.84)
(2.42)
2:1
[(C6H5CH2OCS2)2Cd]
182
84
(White solid)
2:1
[(o-CH3C6H4OCS2)2Hg]
134
76
(Pale yellow solid)
2:1
[(m-CH3C6H4OCS2)2Hg]
136
79
( Pale yellow solid)
2:1
[(p-CH3C6H4OCS2)2Hg]
132
72
( Pale yellow solid)
2:1
[(C6H5CH2OCS2)2Hg]
120
76
( Pale yellow solid)
40.01
2.46
23.45
26.65
(40.12)
(2.95)
(23.47)
(26.78)
33.60
2.39
35.30
22.52
(33.88)
(2.49)
(35.37)
(22.62)
33.67
2.27
35.32
22.45
(33.88)
(2.49)
(35.37)
(22.62)
33.56
2.32
35.34
22.56
(33.88)
(2.49)
(35.37)
(22.62)
33.63
2.35
35.29
22.33
(33.88)
(2.49)
(35.37)
(22.62)
*Ar = (o-, m- and p-CH3C6H4–) and C6H5CH2–; M = Zn (10-13), Cd (14-17) and Hg (18-21)
EXPERIMENTAL
64
Table 2.4: Synthetic and analytical data of mixed dithiocarbonate and dithiophosphate complexes of zinc(II), cadmium(II) and
mercury(II) (22-33)
S. No.
Reactants g (mmol)
Ligand
MCl2
A
Molar
Ratio
Product
(Physical state)
M.P.
(C)
(dec.)
Yield
%
M
Analysis%
Found (Calcd.)
C
H
S
o-ArOCS2Na
1.00(4.84 )
0.66
(4.84)
1.06
(4.84)
1:1:1
[(o-ArOCS2)Zn(S2POGO)]
(white solid)
190
72
14.50
(14.67)
35.02
(35.02)
3.77
(3.84)
28.55
(28.76)
23.
m-ArOCS2Na
1.00(4.84 )
0.66
(4.84)
1.06
(4.84)
1:1:1
[(m-ArOCS2)Zn(S2POGO)]
(white solid)
183
74
14.51
(14.67)
35.00
(35.02)
3.76
(3.84)
28.65
(28.76)
24.
p-ArOCS2Na
1.00(4.84 )
0.66
(4.84)
1.06
(4.84)
1:1:1
[(p-ArOCS2)Zn(S2POGO)]
(white solid)
186
76
14.50
(14.67)
35.02
(35.02)
3.72
(3.84)
28.58
(28.76)
25.
ArOCS2Na
1.00(4.84 )
0.66
(4.84)
1.06
(4.84)
1:1:1
[(ArOCS2)Zn(S2POGO)]
(white solid)
191
79
14.55
(14.67)
35.01
(35.02)
3.73
(3.84)
28.58
(28.76)
26.
o-ArOCS2Na
1.00(4.84 )
0.88
(4.84)
1.06
(4.84)
1:1:1
[(o-ArOCS2)Cd(S2POGO)]
(pale yellow solid)
179
69
22.67
(22.81)
31.62
(31.68)
3.35
(3.48)
25.99
(26.02)
27.
m-ArOCS2Na
1.00(4.84 )
0.88
(4.84)
1.06
(4.84)
1:1:1
[(m-ArOCS2)Cd(S2POGO)]
177
71
22.77
(22.81)
31.60
(31.68)
3.45
(3.48)
25.94
(26.02)
(pale yellow solid)
65
EXPERIMENTAL
22.
28.
p-ArOCS2Na
1.00(4.84 )
0.88
(4.84)
1.06
(4.84)
1:1:1
[(p-ArOCS2)Cd(S2POGO)]
(pale yellow solid)
179
70
22.67
(22.81)
31.62
(31.68)
3.35
(3.48)
25.99
(26.02)
29.
ArOCS2Na
1.00(4.84 )
0.88
(4.84)
1.06
(4.84)
1:1:1
[(ArOCS2)Cd(S2POGO)]
(pale yellow solid)
174
72
22.70
(22.81)
31.65
(31.68)
3.45
(3.48)
25.90
(26.02)
30.
o-ArOCS2Na
1.00(4.84 )
1.31
(4.84)
1.06
(4.84)
1:1:1
[(o-ArOCS2)Hg(S2POGO)]
(yellow solid)
163
73
34.51
(34.52)
26.57
(26.87)
2.66
(2.95)
21.97
(22.07)
31.
m-ArOCS2Na
1.00(4.84 )
1.31
(4.84)
1.06
(4.84)
1:1:1
[(m-ArOCS2)Hg(S2POGO)]
(yellow solid)
168
70
34.49
(34.52)
26.77
(26.87)
2.62
(2.95)
21.98
(22.07)
32.
p-ArOCS2Na
1.00(4.84 )
1.31
(4.84)
1.06
(4.84)
1:1:1
[(p-ArOCS2)Hg(S2POGO)]
(yellow solid)
167
74
34.50
(34.52)
26.67
(26.87)
2.67
(2.95)
21.91
(22.07)
33.
ArOCS2Na
1.00(4.84 )
1.31
(4.84)
1.06
(4.84)
1:1:1
[(ArOCS2)Hg(S2POGO)]
(yellow solid)
169
73
34.50
(34.52)
26.67
(26.87)
2.61
(2.95)
21.90
(22.07)
Where, Ar = CH3C6H4/C6H5CH2; G = CH2C(CH3)2CH2; MCl2= ZnCl2 (22-25), CdCl2 (26-29) and HgCl2 (30-33)
A = OGOPS2Na
EXPERIMENTAL
66
EXPERIMENTAL
2.3.4: Synthesis of Adducts (34-81)
2.3.4.1: Synthesis of [(o-CH3C6H4OCS2)2Zn.2NC5H5] (34)
For
the
synthesis
of
the
compound
[(o-CH3C6H4OCS2)2Zn.2NC5H5]
(34)
approximately ~ 20 ml colloidal solution of bis(o-tolyldithiocarbonate)zinc(II) (10)
(0.50 g, 1.15 mmol) in dichloromethane was taken in a 100 ml of round bottom flask.
To this solution was added pyridine (0.18 g, 2.29 mmol) dropwise with constant
stirring at room temperature. The reaction mixture becomes clear immediately after
addition of pyridine. Evaporation of excess of solvent and final drying in vacuo
results the product as off white solid in 85% yield.
Similar methodology was followed for the synthesis of analogous complexes
[(o-CH3C6H4OCS2)2Zn.2P(C6H5)3] (46), [(o-CH3C6H4OCS2)2Zn.N2C12H8] (58) and
[(o-CH3C6H4OCS2)2Zn.N2C10H8] (70). The synthetic and analytical data for these
complexes (34-37, 46-49, 58-61 and 70-73) are given in Table 2.5.
2.3.4.2: Synthesis of [(o-CH3C6H4OCS2)2Cd.2P(C6H5)3] (50)
To a chloroform solution (~ 20 ml) of [(o-CH3C6H4OCS2)2Cd] (14) (0.50 g, 1.04
mmol) was added triphenylphosphine (0.55 g, 2.08 mmol) with constant stirring at
room temperature. Colorless solution changes to pale yellow within 15 minutes. The
contents were stirred for further 30 minutes at room temperature. The solvent was
then evaporated under vacuum, which results the compound (50) as pale yellow solid
in 87% yield.
Similar methodology was followed for the synthesis of analogous complexes
[(o-CH3C6H4OCS2)2Cd.2NC5H5] (38), [(o-CH3C6H4OCS2)2Cd.N2C12H8] (62) and [(oCH3C6H4OCS2)2Cd.N2C10H8] (74). The synthetic and analytical data for these
complexes (38-41, 50-53, 62-65 and 74-77) are given in Table 2.5.
67
EXPERIMENTAL
2.3.4.3: Synthesis of [(o-CH3C6H4OCS2)2Hg.N2C12H8] (66)
To a chloroform solution (~ 20 ml) of [(o-CH3C6H4OCS2)2Hg] (17) (0.50 g, 0.87
mmol) was added chloroform solution of 1,10-phenanthroline (0.16 g, 0.87 mmol)
dropwise with constant stirring at room temperature. Pale yellow solution changes to
yellow within 5 minutes. The contents were stirred for further 30 minutes at room
temperature. The solvent was then evaporated under vacuum, which results the
compound (66) as yellow solid in 85% yield.
Similar methodology was followed for the synthesis of analogous complexes
[(o-CH3C6H4OCS2)2Hg.2NC5H5] (42), [(o-CH3C6H4OCS2)2Hg.2P(C6H5)3] (54) and
[(o-CH3C6H4OCS2)2Hg.N2C10H8] (78). The synthetic and analytical data for these
complexes (42-45, 54-57, 66-69 and 78-81) are given in Table 2.5.
68
Table 2.5: Synthetic and analytical data of adducts of (ortho–, meta– and para tolyl)/benzyldithiocarbonates of zinc(II), cadmium(II) and
mercury(II) with nitrogen and phosphorus donor ligands (34-81)
S.
Reactants g(mmol)
Molar
No.
[ArOCS2]2#M L’
ratio
34.
35.
36.
37.
38.
40.
0.18
(1.15)
(2.29)
0.50
0.18
(1.15)
(2.29)
0.50
0.18
(1.15)
(2.29)
0.50
0.18
(1.15)
(2.29)
0.50
0.16
(1.04)
(2.08)
0.50
0.16
(1.04)
(2.08)
0.50
0.16
(1.04)
(2.08)
1:2
Yield
(Physical State)
(%)
[(o-CH3C6H4OCS2)2Zn.2Py]
85
M.P. (C)
Analyses (%)
(dec.)
Found (Calcd.)
209
(off white solid)
1:2
[(m-CH3C6H4OCS2)2Zn.2Py]
[(p-CH3C6H4OCS2)2Zn.2Py]
86
210
[(C6H5CH2OCS2)2Zn.2Py]
78
209
[(o-CH3C6H4OCS2)2Cd.2Py]
80
220
[(m-CH3C6H4OCS2)2Cd.2Py]
82
180
[(p-CH3C6H4OCS2)2Cd.2Py]
(yellow solid)
52.83
52.78
46.75
(46.95)
87
179
(yellow solid)
1:2
52.80
(52.92)
(yellow solid)
1:2
4.03
(52.92)
(off white solid)
1:2
52.80
(52.92)
(off white solid)
1:2
H
(52.92)
(off white solid)
1:2
C
46.65
(46.95)
80
167
46.69
(46.95)
N
S
M
4.69
21.59
11.01
(21.73)
(11.08)
21.59
11.02
(21.73)
(11.08)
21.69
11.04
(21.73)
(11.08)
21.59
11.01
(21.73)
(11.08)
19.20
16.59
(19.28)
(16.90)
19.10
16.62
(19.28)
(16.90)
19.25
16.69
(19.28)
(16.90)
(4.10) (4.75)
4.02
4.59
(4.10) (4.75)
4.05
4.61
(4.10) (4.75)
4.03
4.69
(4.10) (4.75)
3.61
8.40
(3.64) (8.42)
3.60
8.30
(3.64) (8.42)
3.59
8.39
(3.64) (8.42)
69
EXPERIMENTAL
39.
0.50
Product
41.
42.
43.
44.
45.
46.
47.
48.
49.
51.
70
0.16
(1.04)
(2.08)
0.50
0.13
(0.88)
(1.76)
0.50
0.13
(0.88)
(1.76)
0.50
0.13
(0.88)
(1.76)
0.50
0.13
(0.88)
(1.76)
0.50
0.59
(1.15)
(3.00)
0.50
0.59
(1.15)
(3.00)
0.50
0.59
(1.15)
(3.00)
0.50
0.59
(1.15)
(3.00)
0.50
0.55
(1.04)
(2.08)
0.50
0.55
(1.04)
(2.08)
1:2
[(C6H5CH2OCS2)2Cd.2Py]
82
178
(yellow solid)
1:2
[(o-CH3C6H4OCS2)2Hg.2Py]
(46.95)
80
162
(yellow solid)
1:2
[(m-CH3C6H4OCS2)2Hg.2Py]
[(p-CH3C6H4OCS2)2Hg.2Py]
83
165
[(C6H5CH2OCS2)2Hg.2Py]
81
164
[(o-CH3C6H4OCS2)2Zn.2PPh3]
79
165
[(m-CH3C6H4OCS2)2Zn.2PPh3]
84
210
80
210
(white solid)
1:2
[(p-CH3C6H4OCS2)2Zn.2PPh3]
81
211
(white solid)
1:2
[(C6H5CH2OCS2)2Zn.2PPh3]
80
208
(white solid)
1:2
[(o-CH3C6H4OCS2)2Cd.2PPh3]
87
189
(white solid)
1:2
[(m-CH3C6H4OCS2)2Cd.2PPh3]
(white solid)
48.92
(48.94)
(white solid)
1:2
48.89
(48.94)
(yellow solid)
1:2
48.91
(48.94)
(yellow solid)
1:2
48.90
(48.94)
(yellow solid))
1:2
46.70
89
190
3.58
8.39
(3.64) (8.42)
3.76
6.20
(3.88) (6.34)
3.81
6.21
(3.88) (6.34)
3.80
6.22
(3.88) (6.34)
3.78
6.29
(3.88) (6.34)
65.16
4.56
(65.29)
(4.64)
65.16
4.56
(65.29)
(4.64)
65.16
4.56
(65.29)
(4.64)
65.14
4.53
(65.29)
(4.64)
61.82
4.70
(61.86)
(4.99)
61.82
4.71
(61.86)
(4.99)
---
---
---
---
---
19.19
16.58
(19.28)
(16.90)
14.41
(14.52)
14.47
(14.52)
14.49
(14.52)
14.50
(22.70)
22.59
(22.70)
22.61
(22.70)
22.64
(14.52)
(22.70)
13.34
6.64
(13.41)
(6.84)
13.34
6.64
(13.41)
(6.84)
13.34
6.64
(13.41)
(6.84)
13.30
6.78
(13.41)
(6.84)
12.40
(12.70)
---
22.60
12.41
(12.70)
11.09
(11.13)
11.11
(11.13)
EXPERIMENTAL
50.
0.50
52.
53.
54.
55.
56.
57.
58.
59.
60.
0.55
(1.04)
(2.08)
0.50
0.55
(1.04)
(2.08)
0.50
0.46
(0.88)
(1.76)
0.50
0.46
(0.88)
(1.76)
0.50
0.46
(0.88)
(1.76)
0.50
0.46
(0.88)
(1.76)
0.50
0.22
(1.15)
(1.15)
0.50
0.22
(1.15)
(1.15)
0.50
0.22
(1.15)
(1.15)
0.50
0.22
(1.15)
(1.15)
1:2
[(p-CH3C6H4OCS2)2Cd.2PPh3]
82
191
(white solid)
1:2
[(C6H5CH2OCS2)2Cd.2PPh3]
86
192
(white solid)
1:2
[(o-CH3C6H4OCS2)2Hg.2PPh3]
87
165
(white solid)
1:2
[(m-CH3C6H4OCS2)2Hg.2PPh3]
86
164
(white solid)
1:2
[(p-CH3C6H4OCS2)2Hg.2PPh3]
84
163
(white solid)
1:2
[(C6H5CH2OCS2)2Hg.2PPh3]
89
163
(white solid)
1:1
[(o-CH3C6H4OCS2)2Zn.Phen]
84
230
(Yellow Solid)
1:1
[(m-CH3C6H4OCS2)2Zn.Phen]
[(p-CH3C6H4OCS2)2Zn.Phen]
82
229
[(C6H5CH2OCS2)2Zn.Phen]
(Yellow Solid)
(61.86)
(4.99)
61.80
4.71
(61.86)
(4.99)
56.82
4.50
(56.89)
(4.59)
56.85
4.45
(56.89)
(4.59)
56.87
4.55
(56.89)
(4.59)
56.79
4.51
(56.89)
(4.59)
54.90
3.62
54.90
(54.94)
82
229
(Yellow Solid)
1:1
4.69
(54.94)
(Yellow Solid)
1:1
61.81
54.90
(54.94)
80
220
54.81
(54.94)
---
(12.70)
---
---
---
11.49
(11.68)
---
11.52
(11.68)
---
4.49
4.49
4.49
(3.68) (4.58)
3.58
11.40
(11.68)
(3.68) (4.58)
3.62
12.46
(12.70)
(3.68) (4.58)
3.62
12.48
4.46
(3.68) (4.58)
11.60
11.08
(11.13)
11.10
(11.13)
18.09
(18.27)
18.10
(18.27)
18.19
(18.27)
18.18
(11.68)
(18.27)
20.81
10.60
(20.95)
(10.69)
20.81
10.60
(20.95)
(10.69)
20.81
10.60
(20.95)
(10.69)
20.79
10.59
(20.95)
(10.69)
71
EXPERIMENTAL
61.
0.50
62.
63.
64.
65.
66.
67.
68.
69.
70.
72.
0.22
(1.15)
(1.15)
0.50
0.22
(1.15)
(1.15)
0.50
0.22
(1.15)
(1.15)
0.50
0.22
(1.15)
(1.15)
0.50
0.16
(0.87)
(0.87)
0.50
0.16
(0.87)
(0.87)
0.50
0.16
(0.87)
(0.87)
0.50
0.16
(0.87)
(0.87)
0.50
0.18
(1.15)
(1.15)
0.50
0.18
(1.15)
(1.15)
0.50
0.18
(1.15)
(1.15)
1:1
[(o-CH3C6H4OCS2)2Cd.Phen]
85
184
(Yellow Solid)
1:1
[(m-CH3C6H4OCS2)2Cd.Phen]
(50.86)
80
179
(Yellow Solid)
1:1
[(p-CH3C6H4OCS2)2Cd.Phen]
[(C6H5CH2OCS2)2Cd.Phen]
81
180
[(o-CH3C6H4OCS2)2Hg.Phen]
86
181
[(m-CH3C6H4OCS2)2Hg.Phen]
85
176
[(p-CH3C6H4OCS2)2Hg.Phen]
81
170
[(C6H5CH2OCS2)2Hg.Phen]
82
169
[(o-CH3C6H4OCS2)2Zn.Bipy]
86
168
[(m-CH3C6H4OCS2)2Zn.Bipy]
80
223
[(p-CH3C6H4OCS2)2Zn.Bipy]
(Yellow Solid)
53.02
(53.10)
78
219
(Yellow Solid)
1:1
44.82
(44.88)
(Yellow Solid)
1:1
44.81
(44.88)
(Yellow Solid)
1:1
44.80
(44.88)
(Yellow Solid)
1:1
44.80
(44.88)
(Yellow Solid)
1:1
50.85
(50.86)
(Yellow Solid)
1:1
50.80
(50.86)
(Yellow Solid)
1:1
50.82
(50.86)
(Yellow Solid)
1:1
50.80
53.02
(53.10)
79
219
53.02
(53.10)
3.62
4.20
(3.66) (4.24)
3.61
4.21
(3.66) (4.24)
3.62
4.19
(3.66) (4.24)
3.62
4.21
(3.66) (4.24)
3.22
3.70
(3.23) (3.74)
3.20
3.69
(3.23) (3.74)
3.21
3.71
(3.23) (3.74)
3.21
3.72
(3.23) (3.74)
3.72
4.69
(3.77) (4.76)
3.70
4.67
(3.77) (4.76)
3.70
4.67
(3.77) (4.76)
19.31
16.99
(19.40)
(17.00)
19.32
16.98
(19.40)
(17.00)
19.29
16.95
(19.40)
(17.00)
19.30
16.99
(19.40)
(17.00)
17.10
26.70
(17.12)
(26.77)
17.08
26.71
(17.12)
(26.77)
17.10
26.72
(17.12)
(26.77)
17.09
26.73
(17.12)
(26.77)
21.61
11.10
(21.81)
(11.12)
21.61
11.10
(21.81)
(11.12)
21.61
11.10
(21.81)
(11.12)
72
EXPERIMENTAL
71.
0.50
73.
74.
75.
76.
77.
78.
79.
80.
81.
0.18
(1.15)
(1.15)
0.50
0.16
(1.02)
(1.02)
0.50
0.16
(1.02)
(1.02)
0.50
0.16
(1.02)
(1.02)
0.50
0.16
(1.02)
(1.02)
0.50
0.13
(0.86)
(0.86)
0.50
0.13
(0.86)
(0.86)
0.50
0.13
(0.86)
(0.86)
0.50
0.13
(0.86)
(0.86)
1:1
[(C6H5CH2OCS2)2Zn.Bipy]
81
220
(Yellow Solid)
1:1
[(o-CH3C6H4OCS2)2Cd.Bipy]
[(m-CH3C6H4OCS2)2Cd.Bipy]
79
189
[(p-CH3C6H4OCS2)2Cd.Bipy]
77
186
[(C6H5CH2OCS2)2Cd.Bipy]
80
187
[(o-CH3C6H4OCS2)2Hg.Bipy]
78
188
[(m-CH3C6H4OCS2)2Hg.Bipy]
82
168
[(p-CH3C6H4OCS2)2Hg.Bipy]
80
168
[(C6H5CH2OCS2)2Hg.Bipy]
43.09
81
163
79
165
(Yellow Solid)
43.12
3.83
(3.07) (3.87)
3.01
(43.17)
3.80
(3.07) (3.87)
3.05
(43.17)
3.81
(3.07) (3.87)
3.06
43.12
4.40
(3.49) (4.41)
3.02
(43.17)
(Yellow Solid )
1:1
43.10
4.36
(3.49) (4.41)
3.42
(43.17)
(Yellow Solid)
1:1
49.12
4.37
(3.49) (4.41)
3.44
(49.17)
(Yellow Solid)
1:1
49.11
4.39
(3.49) (4.41)
3.40
(49.17)
(Yellow Solid)
1:1
49.10
4.46
(3.77) (4.76)
3.40
(49.17)
(Yellow Solid)
1:1
49.10
(49.17)
(Yellow Solid)
1:1
3.58
(53.10)
(Yellow Solid)
1:1
53.01
3.82
(3.07) (3.87)
21.79
10.99
(21.81)
(11.12)
20.17
17.69
(20.19)
(17.70)
20.12
17.66
(20.19)
(17.70)
20.16
17.68
(20.19)
(17.70)
20.15
17.62
(20.19)
(17.70)
17.71
27.70
(17.73)
(27.73)
17.69
27.68
(17.73)
(27.73)
17.67
27.71
(17.73)
(27.73)
17.72
27.69
(17.73)
(27.73)
Ar = o-, m- or p-CH3C6H4– and C6H5CH2–, #M = Zn (34-37, 46-49, 58-61 and 70-73), Cd (38-41, 50-53, 62-65 and 74-77) and Hg (42-45, 5473
57,
66-69
and
78-81),
L’
=
Py
(34-45),
PPh3
(46-57),
Phen
(58-69)
and
Bipy
(70-81).
EXPERIMENTAL
0.50
EXPERIMENTAL
2.4: BIOLOGICAL ACTIVITY
2.4.1: Antifungal activity
Antifungal activity of the compounds has been studied to test their efficacy as
antimicrobial agents. The antifungal activity of the complex was tested by Poisoned
food technique against the pathogenic fungus Fusarium oxysporium. The pure
culture of Fusarium oxysporium was obtained from Division of Plant Pathology,
Sher-e-Kashmir University of Agriculture Sciences and Technology (SKUAST-J),
Jammu (J&K). However, the antifungal activity was performed in the Bioassay Lab,
Department of Chemistry, University of Jammu, Jammu (J&K). The stock culture was
maintained on petriplates containing 50 ml of potato dextrose agar medium. Care was
taken to ensure a regular supply of uncontaminated seven days old culture until all the
antifungal studies were over. The cultures were maintained at 28±1 C in a BOD
incubator.
Potato Dextrose Agar (PDA) Medium
Potato Dextrose Agar (PDA) Medium was prepared with the following composition:
Peeled Potato
200 g
Dextrose
20 g
Agar
20 g
Distilled water
1000 ml
Ph
6
The ingredients were taken in one litre Erlenmeyer's conical flask, plugged
with non- absorbent cotton and the mouth of flask was wrapped with aluminium foil.
The contents of the flask were sterilized at 20 lb/square inch pressure for 30 minutes
and cooled to about 40 C. 10 mg of the antibiotic streptomycin was added to this
cooled medium and mixed thoroughly for prevention of bacterial activity.
Poisoned Food Technique
The test solutions were prepared by dissolving the compounds in chloroform. The test
solutions were mixed in the PDA and poured in the petriplates in sterilized conditions
inside the Laminar flow. After solidification, the plates were inoculated with seven
74
EXPERIMENTAL
days old culture of pathogen Fusarium oxysporium by placing 2 mm bit in the centre
of the plates. The inoculated plates were incubated at 27 C for 4 days. The linear
growth of fungus in control and treatment were recorded at different concentrations of
the complexes. The growth inhibition of Fusarium oxysporium over control was
calculated as:
C-T
% Inhibition (I) =
X 100
C
Where I = percent inhibition
C = mean growth of fungus in (mm) in control, and
T = mean growth of fungus in (mm) in treatment.
2.4.2: Antibacterial activity
Methodology
 Source of bacteria
The clinical isolates of following bacterial strains were obtained from Department of
Biotechnology, University of Jammu, Jammu (J & K). The antibacterial sensitivity
assays were performed at Bioassay Lab, in Department of Chemistry, University of
Jammu, Jammu (J & K).
Gram Negative Bacteria
Gram Positive Bacteria
Klebsiella pneumonia
Bacillus cereus
 Culture and preservation of bacterial strains
The cultures of bacteria were grown on nutrient broth (Hi Media, Mumbai) at 37 C
for 12-14 hours and the pure culture were isolated in case of clinical isolates by serial
dilution method. The cultures were maintained on nutrient agar slant (Hi Media,
Mumbai) at 4 C. Glycerol stock of the bacteria were prepared and stored at -80 C for
75
EXPERIMENTAL
long-term storage. For the preparation of nutrient broth the following ingredients were
used.
Beef extract……………………………………….
1.0 g
Yeast extract………………………………………. 2.0 g
Peptone……………………………………………....5.0 g
NaCl………………………………………………… 5.0 g
Triple distilled water………………………………...1000 ml
The nutrient broth was prepared by dissolving the desired ingredients in the
1000 ml of triple distilled water as required with appropriate percentage of different
constituents. The fraction of the nutrient broth so obtained was used to culture the
bacterial strains and other fraction was used to prepare nutrient agar by adding
appropriate amount of solid agar.
 Glycerol stock preparation for long-term storage
The organisms were grown in nutrient broth. To the phase culture, glycerol was added
to a final concentration of 20% in a cryo-vial. The organism is stored at -80 C. The
glycerol functions as cryo-protectant and organism is live for more than one year in
these conditions.
 Evaluation of antibacterial activity of compounds by Agar
spot test and diffusion technique
Agar spot test and diffusion technique was used for studying the antimicrobial activity
of the isolates against pathogens of human importance. Minimal inhibitory
concentration (MIC) and the minimal lethal concentration (MLC) would also be
analyzed.
 Preparation of agar plates
The nutrient agar (200 ml) was prepared by mixing the ingredients given for nutrient
broth and adding 1% agar agar in 200 ml of triple distilled water, autoclaved at 121
76
EXPERIMENTAL

C, 15 lbs, 15 minutes and allowed to cool up to 45-50 C. The nutrient agar was
poured in sterile petriplates aseptically until the bottom was covered to a depth of 5
mm. The plates were left undisturbed in Laminar flow for solidification of nutrient
agar and were used for further inoculation.
 Inoculation of plates
The plates were inoculated with bacteria using a micropipette with sterile autoclaved
micro tips. 100 l of inoculums was poured on each Petri plate. The inoculums was
spread using a sterile glass spreader to make a uniform lawn. The plates were kept in
Laminar airflow. Now wells are made in petriplates with a well in the centre which
will serve as a control contains solvent in which sample is dissolved. Wells are filled
with 100 l of sample with the help of micro-pipettes. The inoculated plates were
incubated at 37 C for 48 hours in BOD incubator.
 Preparation of test samples
Test samples were prepared in different concentrations (250, 500, 1000 ppm) in
DMSO. Agar medium (20 ml) was poured into each petriplate. The plates were
swabbed with broth cultures of the respective microorganisms Klebsiella pneumonia
and Bacillus cereus and kept for 15 minutes for adsorption to take place. About 6 mm
diameter wells were bored in the seeded agar plates using a punch and 100 l of the
DMSO solution of each test compound was poured into the wells. DMSO was used as
the control for all the test compounds. After holding the plates at room temperature
for 2 hours to allow diffusion of the compounds into the agar then the plates were
incubated at 37 C for 24 hours. The antibacterial activity was determined by
measuring the diameter of the inhibition zone. The entire tests were made in triplicates
and the mean of the diameter of inhibition was calculated.
2.4.3: Cytotoxicity
The cytotoxicity was measured in vitro at IIIM Jammu (J & K), using the cultivated
human cell lines: lung adeno carcinoma cell line A-549, leukemia cell line THP-1,
lung cervical node cell line NCI-H322 and colorectal cancer cell line HCT-116. The
inhibition capacity was assessed using the sulforhodamine B (SRB) protein staining
77
EXPERIMENTAL
assay by 96-well technique. The seeded 96-well plates are incubated for 48 hours after
addition of test samples. Then the cells were fixed in 30% TCA (trichloroacetic acid)
and placed for 1 hour at 4 C followed by washing with distilled water. After airdrying, the fixed cells were stained with 0.4% SRB (prepared in 1% acetic acid), left
at room temperature for 30 minutes, washed with 1% acetic acid and dried.
Solublization is carried out with 10 mM Tris buffer followed by recording the optical
density (OD) with ELISA reader at 540 nm wave-length. The calculation was as
follows:
Percent cell viability =
(OD of test)
X 100
(OD of control)
Percentage inhibition = 100 - Percentage viability
78
“(ortho-, meta- and para-TOLYL)/BENZYL
DITHIOCARBONATES OF ZINC(II), CADMIUM(II)
AND MERCURY(II)”
RESULTS AND DISCUSSION
3.0:
(ortho-,
DITHIOCARBONATES
metaOF
and
ZINC(II),
para-TOLYL)/BENZYL
CADMIUM(II)
AND
MERCURY(II)
This part of thesis deals with the method of synthesis, properties, analytical and
spectroscopic studies of (o-, m- and p-tolyl)/benzyl dithiocarbonate ligands, their
disulfides followed by synthesis and characterization of new complexes of zinc(II),
cadmium(II) and mercury(II) with these ligands as well as their biological activity.
This chapter is divided into following sections for convenience of description of the
present investigations:
Section-I
3.1: General
3.2: New (ortho–, meta– and para–tolyl)/benzyl dithiocarbonate ligands
3.3: Sodium O,O’-neopentylenephosphorodithioate ligand
3.4: Disulfides of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonates
3.5: Dithiocarbonate derivatives of zinc(II), cadmium(II) and mercury(II)
3.6: Adducts of bis-[(ortho–, meta– and para–tolyl)/benzyldithiocarbonates] of
zinc(II), cadmium(II) and mercury(II) with nitrogen and phosphorus donors
Section–II
3.7: Biological activity
3.7.1: Antifungal activity
3.7.2: Antibacterial activity
3.7.3: Cytotoxic Analysis
79
RESULTS AND DISCUSSION
3.1: GENERAL
As highlighted in the preceding introduction section that the alkyldithiocarbonate
chemistry has experienced a rapid, almost explosive, growth during the last decades.
However, literature survey revealed paucity of information especially about (o-, mand p- tolyl)/benzyl dithiocarbonate ligands and their derivatives. There are several
reports available regarding the synthesis of alkyl xanthate ligands and their
derivatives.64-72 The synthesis of aryl xanthates of nickel [Ni(S2COC6H4-4tBu)2] and
cobalt [Co(S2COC6H2-2,4,6-Me3)3] have recently been reported.80 Most of the early
investigations of these systems, performed several decades ago, were centered on the
use of sulfur ligands as an analytical reagents but interest in the synthesis and
characterization of these ligands has increased because of their potential biological
activity81-82 and practical applications in the fields as diverse as rubber technology,8384
agriculture 85-86 to electronics. 87-88
Metal xanthates are extensively used as pharmaceuticals, fungicidies,
agricultural reagents and quite recently in therapy for HIV infections.97-98,
79
Zinc
isopropyl and butyl xanthates have been used as an accelerator in the vulcanization of
rubber40-44 and catalysts in the polymerization of olefins,47-48 respectively. Owing to
these good antiseize properties of dixanthogens, the isopropyl-, butyl-, amyl- and
nonyl-dixanthogens find their potential application as an oil additives.53,
59, 218
However, copper or iron salts of cellulose xanthic acid are used for germination and
in the initial growth of plants.58 Dibutyl dixanthogen is used as a constituent of a fire
proofing agents for self-extinguishing resins.50 Insoluble cellulose xanthate, Oalkyldithiocarbonate of cellulose, was used for the removal of heavy metal ions from
aqueous solutions.63 Sodium and potassium ethyl xanthate have antidotal effects in
acute mercurial poisoning.60 The transition metal xanthate complexes have been
investigated for nonlinear optical applications.60 However, literature survey revealed
scant information especially about (o–, m– and p–tolyl)/benzyl dithiocarbonate
ligands and their derivatives.219-220
The structural data on aryl xanthates of nickel(II), palladium(II) and
cobalt(III) complexes have been reported for the first time by Chen et al.79 The
80
RESULTS AND DISCUSSION
properties of aryl xanthates are similar to those of 1,1–dithiolates. These ligands and
their metal derivatives are somewhat more susceptible to thermal and atmospheric
decomposition than the analogous alkyl derivatives.94
In view of the above and an interesting chemistry of Group 12th complexes,
we have initiated the investigations on tolyl/benzyl dithiocarbonates and their metal
complexes. We have found some promising results. Recently, the synthesis and
characterization of (o-, m- and p-tolyl)/benzyl dithiocarbonate ligands, [(o–, m– and
p–CH3C6H4O)CS2]–Na+ and C6H5CH2OCS2–Na+ has been achieved in our
laboratory.219
3.2: New (ortho–, meta– and para–tolyl)/benzyl dithiocarbonate
ligands (1–4)
Alkyl xanthates are usually synthesized by mixing KOH/NaOH with alcohols (excess)
to produce ROK/RONa followed by insertion of CS2.221 However, we have
synthesized tolyl/benzyl xanthates by using sodium metal and toluene as solvent
instead of KOH/NaOH and the parent alcohol as solvent.
Reaction of sodium metal with ortho–, meta–, para–cresols (o–, m–, p–
CH3C6H4OH) and benzyl alcohol (C6H5CH2OH) in 1:1 stoichiometric ratio in
refluxing toluene resulted in the formation of sodium methylphenolates (o–, m–, p–
CH3C6H4ONa) and sodium phenylmethanolate (C6H5CH2ONa) as creamish viscous
pasty mass. Addition of an equimolar amount of CS2 to these at 0 – 5 °C forms the
corresponding sodium salt of (o–, m– and p–cresyl)/benzyl dithiocarbonates as a pale
yellow solid in 65-72% yield (Scheme 3.1).
ArOH +
Na
Toluene
Reflux
ArONa
CS2
0-5oC
ArOCS2Na
[Ar = o-, m-, p-CH3C6H4 (1-3) and C6H5CH2 (4)]
Scheme 3.1: Synthesis of (o–, m–, p–CH3C6H4OCS2)Na and C6H5CH2OCS2Na
81
RESULTS AND DISCUSSION
These sodium salts appear to be hygroscopic in nature, soluble in methanol,
ethanol, dichloromethane and tetrahydrofuron, insoluble in most of the hydrocarbon
solvents and sparingly soluble in chloroform. The elemental analysis (C, H and S) of
these ligands were found consistent with their composition. These ligands were
further characterised by various spectral studies like mass, IR and 1H and 13C NMR.
Infrared
IR spectral data (4000–400 cm–1) were interpret on the comparison basis with the
literature reports.79,
94, 99
The IR spectra show the characteristic sharp band for
v(C─O─C) and broad band for v(C
C) (tolyl and benzyl ring stretching) in the
region 1231–1224 cm–1 and 1610–1590 cm–1, respectively. The strong intensity bands
for v(C═S) and v(C─S) were appeared in the range 1145–1140 cm–1 and 1008–1002
cm–1. The v(C─H) vibrations (due to the tolyl and benzyl ring) were observed in the
region 3023–2991 cm–1. The relevant IR spectral data of the ligands (1–4) have been
summarized in Table 3.1. The IR spectrum of a representative ligand i.e. m–
CH3C6H4OCS2Na (2) is shown in Figure 3.1.
1
H NMR
1
H NMR spectra of these ligands in DMSO show chemical shifts for the –CH3 (1–3)
and for –CH2 (4) protons as singlet at 2.26–2.36 ppm and 4.52 ppm, respectively. The
chemical shifts for tolyl and benzyl ring protons were observed in the downfield region
with their usual splitting pattern. There were two resonances for the ring protons of
para derivative (3) (6.85–6.95 ppm) whereas four resonances were observed for ortho
derivative (1) (6.60–6.92 ppm) and meta derivative (2) (6.85–7.45 ppm). The protons
of benzyl ring proton of ligand (4) depicted their chemical shift in the region 7.10–
7.22 ppm. The resonance for individual protons and the chemical shift values of 1H
NMR spectral data of ligands (1–4) are given in Table 3.2. The 1H NMR spectrum of a
representative ligand i.e. m–CH3C6H4OCS2Na (2) is shown in Figure 3.2.
13
C NMR
Evidence for the formation of these ligands is clearly exhibited in the
13
C NMR
spectra which showed a sharp singlet in the downfield region in the range 195.12–
82
RESULTS AND DISCUSSION
220.70 ppm. This signal is assigned to the carbon nucleus of –(O)CS2 group.
Chemical shift of ortho–, meta– and para– carbons were found in the region 114.20–
123.12 ppm, 127.42–130.41 ppm and 120.43–126.21 ppm, respectively.The shift for
carbon nucleus attached to –CH3 and –CH2 groups were found in the region 123.45–
135.51 ppm and 140.21 ppm. Moreover, in the upfield region of 13C NMR spectra of
these ligands, show the signals due to –CH3 and –CH2 carbons in the range 20.12–
22.92 ppm and 75.21 ppm, respectively. Generally, the
13
C NMR spectra of these
ligands were found to exhibit no additional resonances and thus reflect the purity of
these ligands. The
13
C NMR spectral data of these ligands (1–4) have been
summarized in Table 3.3. The
13
C NMR spectrum of a representative ligand i.e. m–
CH3C6H4OCS2Na (2) is shown in Figure 3.3.
Mass
Mass spectra of these ligands (1–4) exhibited the molecular ion peak [M+] at 206
(m/z), suggested the monomeric nature of these ligands. Other important peaks
observed are given in the Table 3.4, which are corresponded to the fragmented
species after successive removal of different groups. The mass fragmentation pattern
of these ligands (1–3) is given below (Scheme 3.2).
[o-, m- and p-CH3C6H4OCS2Na]
[M+] 206 (26)
[o-, m- and p-CH3C6H4]
+
[M ] 91 (21)
[o-, m- and p-CH3C6H4OCS2]
[M+] 183 (8)
[o-, m- and p-CH3C6H4O]
[M+] 107 (40)
+
CS2
[M+] 76 (52)
Scheme 3.2: Mass fragmentation pattern of (o–, m– and p–CH3C6H4OCS2)Na,
bracket = m/z, parentheses = intensities.
83
RESULTS AND DISCUSSION
Based on the above studies and literature reports79,94,99, following type of
general structure may be deduced for sodium salt of (o–, m– and p–tolyl)/benzyl
dithiocarbonate ligands (Figure 3.4).
CH3
S
O
C
S
CH2 O C
Na
S
Na
S
(b)
(a)
Figure 3.4: Structure of (o-, m-, p-CH3C6H4OCS2)Na (a) and
C6H5CH2OCS2Na (b)
3.3: Sodium O,O’-neopentylenephosphorodithioate ligand
The
reaction
of
2,2′-dimethyl-1,3-dihydroxypropane
(neopentyl
glycol),
C(CH3)2(CH2OH)2, with phosphoruspentasufide, P2S5, in the stoichiometric ratio of
2:1
in
benzene
yielded
the
neopentylene
dithiophosphoric
acid,
OCH2C(CH3)2CH2OPS2H as solid white solid in 80% yield. This is subsequently
converted into sodium salt by its direct reaction with sodium isopropoxide in benzene
strictly under anhydrous condition.
2(HOCH2)C(CH3)2(CH2OH) + P2S5
C6H6
-H2S
2(OCH2)C(CH3)2(CH2O)PS2H
PriONa
(OCH2)C(CH3)2(CH2O)PS2H
Benzene
(OCH2)C(CH3)2(CH2O)PS2Na
Scheme 3.3: Synthesis of sodium salt of neopentylenedithiophosphoric acid
Sodium salts are soluble in DMSO and methanol or ethanol, sparingly soluble
in chloroform and insoluble in most of the hydrocarbon solvents. This ligand appears
84
RESULTS AND DISCUSSION
to be moisture sensitive but sufficiently stable to handle if they are not directly
exposed to moisture. The micro–elemental analyses of the compounds (5) were found
consistent to the molecular formula of the compounds.
Infrared
IR spectral data (4000–400 cm-1) were interpreted on the comparison basis with the
literature reports.222-225 The absorption bands of strong intensity present in the region
992 cm-1 and 773 cm-1 are assigned for v(P)—O—C and vP—O—(C) stretching
vibrations. The band present in the 551 and 482 cm-1 region may be ascribed to
v(PS)asym and v(PS)sym stretching modes. The relevant IR spectral data of the ligand
(5) are tabulated in Table 3.1.
1
1
H NMR
H NMR spectral data (in DMSO) of the ligand (5) shows the characteristic chemical
shift with their unusual resonance pattern. The chemical shifts for the protons of the CH3 attached to the neopentylene moiety was observed at 1.11 ppm as singlet and
protons of –OCH2 appear at 3.12 ppm as singet. The 1H NMR spectral data of the
ligand (5) have been summarized in Table 3.2.
31
P NMR
31
P NMR (proton-decoupled) spectra show the chemical shift as singlet in the region
91.30 ppm for the ligand 5 indicating that the phosphorus nucleus is equivalent and
only one type of phosphorus is present in this case in solution as well as the
symmetric nature of the species. The 31P NMR chemical shift is given in Table 3.2.
13
C NMR
13
C NMR spectra of the ligand (5) have shown the appearance of the chemical shift
for all the carbon nuclei in their characteristic region. The –CO, –C– and –CH3 carbon
nuclei of the neopentylene moiety have shown their chemical shifts at 73.31, 31.52
and 19.81 ppm, respectively. The 13C NMR spectral data of the ligand (5) have been
summarized in Table 3.3.
85
RESULTS AND DISCUSSION
H3C
OCS2Na
vC=S
vC-O-C
vC-S
Figure 3.1: The IR Spectrum of (m–CH3C6H4OCS2Na) (2)
Figure 3.2: The 1H NMR Spectrum of (m–CH3C6H4OCS2Na) (2)
86
RESULTS AND DISCUSSION
Figure 3.3: The 13C NMR Spectrum of (m–CH3C6H4OCS2Na) (2)
87
Table 3.1: IR spectral data of (ortho, meta– and para–tolyl)/benzyl dithiocarbonate ligands (1–4) and neopentylene ligand (5) in cm–1
v(C–H) v(C C)
(Aromatic
stretching)
v(P)–O–C
vP–O–(C)
v(P=S)
v(P-S)
1590, b
--
--
--
--
3023, b
1596, b
--
--
--
--
1228, vs
2996, b
1599, b
--
--
--
--
1007, s
1225, vs
2991, b
1610, b
--
--
--
--
--
--
--
--
992, s
773, s
551, s
482, m
S. No.
Ligands
v(C=S)
v(C–S)
v(C–O–C)
1.
o–CH3C6H4OCS2Na
1142, s
1004, s
1231, vs
3022, b
2.
m–CH3C6H4OCS2Na
1140, s
1002, s
1224, vs
3.
p–CH3C6H4OCS2Na
1142, s
1008, s
4.
C6H5CH2OCS2Na
1145, s
--
5.
OCH2C(CH3)2CH2OPS2Na
88
RESULTS AND DISCUSSION
s = sharp, b = broad, m = medium, vs = very sharp
Table 3.2: 1H and 31P NMR spectral data of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonate ligands (1–4) and neopentylene ligand
(5) in DMSO (in ppm)
Neopentylene moiety
Tolyl/Benzyl moiety
#
S. No.
–CH3/–CH2
H3C
4
5
4'
O
3
2
1
CH2
5'
OR
2'
1'
-CH3
-CH2
2.36, s, 3H
6.70, d, [H(2)]; 6.71, t, [H(3)]; 6.92, t, [H(4)]; 6.60, d, [H(5)]
--
--
--
2.
2.26, s, 3H
7.03, s, [H(1)]; 6.85, d, [H(3)]; 7.45, t, [H(4)]; 7.05, d, [H(5)]
--
--
--
3.
2.36, s, 3H
6.85, d, [H(1,5)]; 6.95, d, [H(2,4)]
--
--
--
4.
4.52, s, 2H
7.10–7.22, m, [H(1’–5’)]
--
--
--
5.
--
---
1.11, s, 6H
3.12, s, 4H
91.30, s
S. No. of the ligands is according to Table 3.1.
89
RESULTS AND DISCUSSION
1.
s = singlet, d = doublet, t = triplet and m = multiplet
#
P
CH2
CH2
3'
31
(CH3)2C
Table 3.3: 13C NMR spectral data of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonate ligands (1–4) and neopentylene ligand (5) in
DMSO (in ppm)
#
#
S.No
CHn
C(CHn)
–C–O
CH3C6H4O/C6H5CH2O
Cmeta
Cpara
(O)–C–S
-OCH2C(CH3)2CH2O-CO-
-C-
-CH3-
197.04
--
--
--
127.32
195.12
--
--
--
129.62
--
195.61
--
--
--
123.12
130.41
126.21
220.70
--
--
--
--
--
--
--
73.31
31.52
19.81
Cortho
(n=2 or 3)
(n=2 or 3)
1.
22.92
123.45
167.13
114.41
127.42–130.07
120.43
2.
20.12
135.51
166.71
114.20–120.21
128.92
3.
22.01
128.72
166.02
117.01
4.
75.21
140.21
--
5.
--
--
--
S. No. of the ligands is according to Table 3.1.
RESULTS AND DISCUSSION
90
Table 3.4: Mass spectroscopic data of (ortho–, meta– and para– tolyl)/benzyl dithiocarbonate ligands (1–4)
#
S. No.
M. W.
m/z, relative intensities of the ions and assignment
1.
206.08
[M+] 206 (26) [o–CH3C6H4OCS2Na]; [M+] 183 (8) [o–CH3C6H4OCS2]; [M+] 107 (40) [o–CH3C6H4O];
[M+] 76 (52) [CS2].
2.
206.08
[M+] 206 (30) [m–CH3C6H4OCS2Na]; [M+] 183 (10) [m–CH3C6H4OCS2]; [M+] 107 (38) [m–
CH3C6H4O]; [M+] 76 (42) [CS2].
4.
206.08
[M+] 206 (18) [C6H5CH2OCS2Na]; [M+] 183 (8) [C6H5CH2OCS2]; [M+] 107 (54) [C6H5CH2O]; [M+]
[M+] 76 (40) [CS2].
bracket = m/z; parentheses = intensities;
#
S. No. of the ligands is according to Table 3.1.
RESULTS AND DISCUSSION
91
RESULTS AND DISCUSSION
3.4:
Disulfides
(ortho–,
of
meta–
para–tolyl)/benzyl
and
dithiocarbonates (6–9)
Dixanthogens are also considered to be quite important in view to produce metal and
metalloid derivatives. The role of dixanthogens in conjuction with xanthates in the
flotation of sulfide minerals has already attracted considerable attention.226-227 There are a
variety of ways to synthesize bis(thiocarbonyl)–disulfanes, among those, the most
common method used for the preparation is based upon the oxidation of alkali metal salts
of dithiocarbonic acids with iodine in aqueous solution.228-229 Considering the versatile
chemistry of alkyl xanthates and their derivatives as well as non availability of research
work pertaining to tolyl/benzyl xanthates, it is thought worthy to explore the chemistry on
the synthesis and characterization of the oxidative products of newly synthesized ligands
i.e. sodium salt of (o–, m– and p–tolyl)/benzyl dithiocarbonates with iodine in chloroform,
which might produce rather interesting results, particularly, on bonding aspects with
metals and metalloids and thus would provide a thorough understanding.
Oxidation of the sodium salt of tolyl/benzyl dithiocarbonates, ArOCS2Na (Ar =
o–, m– or p–CH3C6H4– and C6H5CH2–), with iodine in chloroform under inert and
anhydrous conditions resulted in the formation of dixanthogens corresponding to
ArOC(S)SSC(S)OAr in fairly good yield as yellow viscous compounds as shown in
Scheme 3.4.
-NaI
S
Ar O
S
I I
S Na
S
Ar O
I
S
Ar O
S Na
-NaI
S
S
Ar O
O
S
Ar
S
92
RESULTS AND DISCUSSION
S
S
ArOCS2Na + I2
CHCl3
-2NaI
Ar O C S S C O Ar
(6-9)
Scheme 3.4: Synthesis of (ArOCS2)2 (6–9) where Ar = o–, m–, p–CH3C6H4– (6–8)
and C6H5CH2– (9)
The presence of two free sulfur donor atoms in these disulfides provides an extra
opportunity to synthesize a variety of new and interesting compounds of inorganic ring
system containing C–S–M linkages.
The pure disulfides were obtained after the isolation of sodium iodide thus formed
during the course of reaction under anhydrous conditions. These reactions appear to be
quite facile and resulted corresponding disulfides in 77–80% yield. These disulfides are
soluble in common organic solvents viz. benzene, toluene, chloroform, acetone,
dichloromethane etc., but are insoluble in n–hexane and carbon tetrachloride. These
compounds are non–volatile even under reduced pressure and tends to decompose on
heating and forming dark brown product having very pungent odour, which, however,
could not be characterized. These disulfides were obtained in sufficient purity as revealed
by spectral studies.
The elemental analyses, particularly of sulfur, of all the disulfides (6–9) were found
consistent to their molecular formula. The monomeric nature of these disulfides was also
confirmed by mass spectral data. These compounds were further characterized by various
spectral studies including IR and NMR (1H and 13C).
Infrared
The tentative assignments of IR spectral data (4000–400 cm–1) were interpreted on the
comparison basis with the literature reports.79,
94, 99, 228-229
The IR spectra show the
characteristic sharp band for v(C─O─C) and broad band for v(C
C) (tolyl and benzyl
93
RESULTS AND DISCUSSION
ring stretching) in the range 1218–1210 cm–1 and 1600–1594 cm–1, respectively. The
v(C=S) frequency in dixanthogens is raised to 1186–1180 cm–1 and while that of v(C─S)
is lowered to 912–900 cm–1, as compared to the representative frequencies of the sodium
xanthates at 1145–1140 cm–1 and 1008–1002 cm–1. The appearance of new band of
medium intensity for (S–S) in the region 510–507 cm–1 is indicating formation of new
bond between sulfur atoms of the two ligands in the compounds. The v(C─H) vibrations
(due to the tolyl and benzyl ring) were observed in the region 3031–3020 cm–1. The
relevant IR spectral data of the compounds (6–9) have been summarized in Table 3.5.
The IR spectrum of the para-tolyldithiocarbonato disulfide (8) is given in Figure 3.5.
1
H NMR
In the 1H NMR spectra (in CDCl3), the chemical shifts for the CH3 and CH2 (benzyl
ring) protons were observed in the region 2.29–2.31 and 4.01 ppm as singlet whereas the
protons of the C6H4 (tolyl ring) and C6H5 (benzyl ring) gave the chemical shift in the
range 6.51–6.90 ppm and 7.10–7.51 ppm, respectively with their usual splitting pattern.
There were two resonances for the ring protons of para derivative (8) (6.55–6.74 ppm)
whereas four resonances were observed for ortho derivative (6) (6.81–6.90 ppm) and
meta derivative (7) (6.51–6.90 ppm). The splitting pattern of the individual ring protons
of the compounds (6-9) are given in Table 3.6. The 1H NMR spectrum of the paratolyldithiocarbonato disulfide (8) is given in Figure 3.6.
13C
NMR
The 13C NMR spectra of these ligands (6-9) have shown the appearance of the chemical
shift for all the carbon nuclei in their characteristic region. The chemical shift for methyl
(–CH3) and methylene (–CH2) carbon occurred in the range 22.52–22.71 and 52.81 ppm,
respectively. The carbon nuclei of phenyl groups (–C6H5 and –C6H4) have displayed their
resonance in the region 114.60–148.75 ppm. The carbon attached to the methyl and
methylene group in the respective compounds was appeared at 122.90–139.11 ppm and
148.75 ppm, respectively. The peak in the region 155.01–158.02 was due to the carbon
attached to the oxygen in the tolyl derivatives (6–8). In
13
C NMR spectra, signal for the
94
RESULTS AND DISCUSSION
carbon nucleus of –(O)CS2 group has been observed in the region 165.01–188.15 ppm,
supporting the authenticity of these compounds. The
13
C NMR spectral data of these
compounds (6–9) have been summarized in Table 3.7. The
13
C NMR spectrum of the
para-tolyldithiocarbonato disulfide (8) is given in Figure 3.7.
Mass
Mass spectra of disulfides of benzyl and tolyl dithiocarbonate ligands (6, 9) show their
characteristic ion peak [M+] at m/z = 366. In addition to molecular ion peak several
other peaks were also observed which are corresponding to the fragmented species m/z
=76 (CS2), m/z = 94 (HCS2OH), m/z = 366 (C8H7OS2)2 after the consecutive removal of
different groups (Table 3.8). The occurrence of molecular ion peak in the compound
supported its monomeric nature. The systematic mass fragmentation pattern of the bis–
[(benzyl)thiocarbonyl]disulfide (9) is interpreted schematically on the basis of mass
spectrum as given in Scheme 3.5.
(C6H5CH2OCS2)2
[M+] 366 (32)
C6H5CH2OCS2
C2H2S2
+
[M ] 154 (25)
CS2
+
[M ] 76 (40)
[M+] 183 (70)
+
CS2
[M+] 76 (40)
(C6H5CH2O)
[M+] 107 (100)
Scheme 3.5: Probable mass fragmentation pattern of (C6H5CH2OCS2)2 (9); [bracket
= m/z; parenthesis = intensities in %]
95
RESULTS AND DISCUSSION
Figure 3.5: The IR spectrum of the para-tolyldithiocarbonato disulfide (8)
Figure 3.6: The 1H NMR spectrum of the para-tolyldithiocarbonato disulfide (8)
96
RESULTS AND DISCUSSION
Figure 3.7: The
13
C NMR spectrum of the para-tolyldithiocarbonato disulfide (8)
97
Table 3.5: IR spectral data of disulfides of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonate ligands (6-9) in cm–1
S. No.
Compound
v(C=S)
v(C–S)
v(C–O–C)
v(C–H)
v(C
C)
v(S–S)
(Aromatic stretching)
6.
(o– CH3C6H4OCS2)2
1186, s
900, s
1212, vs
3031, b
1597, b
507, m
7.
(m– CH3C6H4OCS2)2
1184, s
912, s
1210, vs
3027, b
1595, b
510, m
8.
(p– CH3C6H4OCS2)2
1185, s
900, s
1211, vs
3031, b
1594, b
510, m
9.
(C6H5CH2OCS2)2
1180, s
910, s
1218, vs
3020, b
1600, b
510, m
s = sharp, b = broad, m = medium, vs = very sharp
RESULTS AND DISCUSSION
98
Table 3.6: 1H NMR spectral data of disulfides of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonate ligands (6-9) in CDCl3
(in ppm)
Tolyl/Benzyl moiety
#
S. No.
–CH3/–CH2
H3C
4
5
S
4'
7
CH3
O
3
C
C
S
O
8
3'
5'
S
H2
C
C
C
S
S
6'
S
7.
2.30, s, 6H
6.51, s, [H(1,6)]; 6.62, d, [H(3,8)]; 6.90, t, [H(4,9)]; 6.53, d, [H(5,10)]
8.
2.29, s, 6H
6.65, d, [H(1,5,6,10)]; 6.94, d, [H(2,4,7,9)]
9.
4.51, s, 4H
7.10–7.21, m, [H(1–5,1’–5’)]
s = singlet, d= doublet, m = multiplet
S. No. of the complexes is according to Table 3.5
9
10'
9'
99
RESULTS AND DISCUSSION
2.31, s, 6H
10
8'
S
6.
1
7'
H2
C
1'
2'
OR
6.81, d, [H(2,7)]; 6.72, t, [H(3,8)]; 6.90, t, [H(4,9)]; 6.61, d, [H(5,10)]
2
#
6
S
Table 3.7: 13C NMR spectral data of disulfides of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonate ligands (6-9) in CDCl3
(in ppm)
#
C(CHn)
(n=2 or 3)
(n=2 or 3)
–C–O
6.
22.71
122.90
157.01
114.60
127.11–128.52
121.40
165.01
7.
22.52
139.11
158.02
115.41–119.21
130.72
127.20
167.91
8.
22.60
129.32
155.01
116.21–117.92
130.20–131.81
––
165.52
9.
52.81
148.85
––
120.30
131.31
128.9
188.15
S. No.
S. No. of the complexes is according to Table 3.5
CH3C6H4O/C6H5CH2O
(O)–C–S
Cortho
Cmeta
Cpara
100
RESULTS AND DISCUSSION
#
CHn
Table 3.8: Mass spectral data of disulfides of (ortho–tolyl)/benzyl dithiocarbonate ligands (6-9)
#
S. No.
M. W.
6.
366.0
m/z, Relative intensities of the ions and assignment
[M+] 366 (13) [o–CH3C6H4OCS2]2; [M+] 76 (20) [CS2]; [M+] 336 (13) [C6H4OCS2]2;
[M+] 276 (30) [o–CH3C6H4O2C2S4H]; [M+] 108 (10) [o–CH3C6H4OH].
9.
366.0
[M+] 366 (32) [C6H5CH2OCS2]2; [M+] 260 (45) [C6H5CH2OC2S4H] ;[M+] 154 (25) [C2H2S4];
[M+] 289 (10) [C6H4CH2O2C2S4CH3]; [M+] 76 (40) [CS2].
bracket = m/z, parentheses = intensities in %;
S. No. of the complexes is according to Table 3.5.
101
RESULTS AND DISCUSSION
#
RESULTS AND DISCUSSION
Structural Features
On the basis of analytical studies like elemental analyses, mass, IR and multinuclear
NMR (1H and
13
C), a probable geometry may be assigned to these disulfides. In the IR
spectra the appearance of new bands for S─S vibration supported the formation of these
compounds. It is interesting to note that in the IR spectra of the disulphides (6-9) the
v(C=S) frequency is raised to 1186–1180 cm–1 and while that the v(C─S) is lowered to
912–900 cm–1, as compared to the representative frequencies of the sodium xanthates at
1145–1140 cm–1 and 1008–1002 cm–1. This might be due to linkage between only one
sulfur atom of each dithio moiety. Hence, only one sulfur atom of the
tolyl/benzyldithiocarbonate ligand is involved in bonding with the sulfur of the other
dithiocarbonate ligand, leaving another sulfur atom non–bonded. In conjunction with the
literature reports60, 79, 94, 228-229 the following structure is predicted for these disulfides in
which carbon atoms of both dithio moieties are three fold coordinated (Figure 3.8).
H3 C
O
S
S
C
C
CH3
O
S
S
(6-8)
H2
C O
S
S
C
C
S
O
H2
C
S
(9)
Figure 3.8: Structure of (o-, m-, p-CH3C6H4OCS2)2 (6-8) and (C6H5CH2OCS2)2 (9)
102
RESULTS AND DISCUSSION
3.5: Dithiocarbonate derivatives of zinc(II), cadmium(II) and
mercury(II)
Group 12 metal i.e. Zn, Cd and Hg complexes of dithiocarbonates continue to attract
attention because of various industrial and biological applications.232-235 These classes of
inorganic compounds are large and some of their studies were carried out to understand
the interactions which exist between the metal ions and the ligands. The dithiocarbonate
chemistry of the group 12 elements is well developed and as expected their chemistry is
constrained to the +2 oxidation state. The ease and stability of the complexation reaction
is on the fact that group 12 metals act as strong Lewis acids and hence readily complex to
electron-rich sulfur containing ligands in the principle of Hard Soft [Lewis] Acid Base,
HSAB.236 These complexes have been found to be good air-stable precursors for sulfides
of Zn, Cd and Hg and in the construction of new supramolecular structural motifs.237-238
Among the zinc triad, zinc being an essential element and plays an important role in
biochemical process.239 However cadmium and mercury being toxic in nature has
numerous applications. The development of the efficient antidotes for cadmium and
mercury intoxication has proven to be a task of considerable difficulty. In recent years it
has become apparent that two types of chelating agents can affect antidotes for cadmium
intoxication; uncharged vicinal dithiols240 and dithiocarbamates.241-242 The affinity of 1,1dithiolate ligands for cadmium and mercury was indicated by the fact that the ligands can
be employed as scavengers for these toxic elements in biological media. Mercury is one
of the most toxic heavy metal found in solid and liquid waste from chloro-alkali, paint,
paper/pulp,
battery,
pharmaceutical,
oil
refinery
and
mining
industries.243
Dithiocarbonates are among the most common extractants used for removal of mercury
from aqueous solution.243 Recent publications established that cadmium dithiocarbonates
are useful precursors to CdS nanowires.244 The affinity of Zn, Cd and Hg toward sulfurcontaining ligands leads to many compounds.246-247 In recent years, the preparation and
investigation of well-defined nanocrystal of MS semiconductors, where M = Zn, Cd and
Hg, have been the focus of considerable attention because of the ability to fine-tune their
electronic and optical properties for possible applications.247-248 Compared to the well
103
RESULTS AND DISCUSSION
developed chemistry of alkyl dithiocarbonate derivatives of the main group and transition
metals, much less attention has been paid to aryl derivatives of group 12 elements. A
literature survey revealed wide range of literature pertaining to alkyl dithiocarbonates but
no such report or patent is available on tolyl/benzyl-dithiocarbonates derivatives with
group 12th metals.
3.5.1: Bis[(ortho-, meta and para-tolyl)/benzyldithiocarbonates] of
zinc(II), cadmium(II) and mercury(II) (10-21)
Keeping in view of the above facts, it was considered of interest to investigate the
chemistry of Zn(II), Cd(II) and Hg(II) complexes of tolyl/benzyl dithiocarbonates.
Herein, we report the synthesis and characterization of tolyl/benzyldithiocarbonates of
group 12th metals corresponding to [(ArOCS2)2M] (Ar = o–, m–, p–CH3C6H4– and
C6H5CH2–, M = Zn, Cd and Hg).
Reactions of sodium salts of (o–, m– and p–tolyl)/benzyl dithiocarbonates,
ArOCS2Na (Ar = o–, m–, p–CH3C6H4– and –CH2C6H5), with MCl2 (M = Zn, Cd and Hg)
in 2:1 stoichiometric ratio was carried out in aqueous media. The reaction was stirred for
15 to 45 minutes at room temperature to ensure completion of reaction. The tolyl/benzyl
dithiocarbonates of Zn, Cd and Hg corresponding to [(ArOCS2)2M] were formed as white
(10-17) and yellow solid in 72-84 % yield (18-21) (Scheme 3.6).
2ArOCS2Na + ZnCl2
H2O
[(ArOCS2)2Zn] + 2NaCl
stirring ~ 45 min.
(10-13)
2ArOCS2Na + CdCl2
H2O
[(ArOCS2)2Cd] + 2NaCl
stirring ~ 20 min.
(14-17)
2ArOCS2Na + HgCl2
H2O
stirring ~ 15 min.
[(ArOCS2)2Hg] + 2NaCl
(18-21)
Scheme 3.6: Synthesis of [(ArOCS2)2Zn] (10–13); [(ArOCS2)2Cd] (14–17) and
[(ArOCS2)2Hg] (18–21) [where Ar = o–, m–, p–CH3C6H4– (10–12, 14–16, 18-20) and
C6H5CH2– (13, 17, 21)]
104
RESULTS AND DISCUSSION
These are soluble in common organic solvents like benzene, toluene, chloroform,
acetone and also in coordinating solvents like DMSO and DMF but sparingly soluble in
the non–polar organic solvents viz. carbon tetrachloride and n-hexane. The compounds
obtained were sufficiently pure but these were further washed with distilled water
followed by petroleum ether three times for the sake of extra purity. The micro elemental
analyses, particularly C, H, S, Zn, Cd and Hg, of all the complexes were found reliable to
the molecular formula of the complexes. All these complexes were characterized by
various physico–chemical techniques viz. elemental analyses and spectral studies
including mass, TGA, IR, NMR (1H and 13C). The monomeric nature of these complexes
was also confirmed by mass spectroscopic studies.
Infrared
The IR spectra (4000–200 cm-1) of the complexes and the ligand were compared and
tentative assignments have been made on the basis of comparison with the earlier
reports.219-220, 249-254 Three main regions are of interest in dithiocarbonate compounds: the
1250–1200 cm−1 region primarily associated with the stretching of the COC of
ROCS2; the 1050–950 cm−1 region associated with ν(CS2) and the 420–250 cm−1 region
which is associated with ν(MS). The 1050-950 cm-1 region has been shown to be
reliable for determining whether the ligand is bidentate or unidentate. According to
Bonati and Ugo,249 presence of only one strong bond in the 1040-1005 cm-1 region, which
is associated with v(C
S) stretching vibrations, indicates complete symmetric bidentate
bonding by dithiocarbonate ligand. Thus in complexes (10-21), the sharp bands were
observed in the range 1040–1015 cm-1 indicates the bidentate mode of bonding by the
dithiocarbonate ligand to the respective metal centre. The strong bands of the v(COC)
asymmetric stretching for bidentate coordinated dithiocarbonate ligands appear at 1250–
1230 cm-1. The broad band for v(C
C) (tolyl and benzyl ring stretching) were presented
in the range 1618–1571 cm–1. In the far region, an additional band of weak to medium
intensity (absent in the spectra of ligands) was observed in the region 370–280 cm-1 for
dithiocarbonate complexes (10-21) which is ascribed to v(MS) stretching vibration
where M = Zn, Cd and Hg. The appearance of new band for v(MS) indicates the
105
RESULTS AND DISCUSSION
coordination of the dithiocarbonate ligand with the metal as expected. For complexes
(10-21) we do not have the crystal structure, but the IR spectra suggest the
dithiocarbonate to be present as chelates. All the relevant IR spectral data are given in
the Table 3.9. The IR spectra of few of the representative complexes (10, 17 and 20) are
given in Figures 3.9, 3.10 and 3.11.
1
H NMR
The 1H NMR (CDCl3) spectra of these derivatives show a marginal shift for all
characteristic resonance signals compared to the parent dithiocarbonate moieties. The 1H
NMR spectra of these complexes show the characteristic proton resonances of the
corresponding tolyl and benzyl protons. The chemical shift for the methyl protons of the
tolyldithiocarbonate moiety in the complexes 10–12, 14–16 and 18–20 appeared as
singlet at 2.10–2.37 ppm where as the methylene protons of the benzyldithiocarbonato
moiety in the complexes 13, 17 and 21 resonated at 4.29–4.47 ppm as singlet. The
protons of the C6H4 (tolyl ring) and C6H5 (benzyl ring) gave signals in the range 6.73–
7.14 and 7.01–7.25 ppm with their usual splitting pattern. There is a negligible upfield
shift of ca. 0.03–0.20 ppm as compared with their position in the free ligand, presumably,
as a consequence of coordination. There were two resonances for the ring protons of para
complexes whereas four resonances were observed for ortho and meta derivatives. The
splitting pattern and intensities of peaks in the spectra of all these complexes are found to
be consistent with their structures. The resonances for individual protons are specified in
the Table 3.10. The 1H NMR spectra of few of the representative complexes (10, 17 and
20) are given in Figures 3.12, 3.13 and 3.14.
13
C NMR
Evidence for the formation of the complexes is clearly exhibited in the 13C NMR spectra
recorded in CDCl3 by occurrence of a sharp peak for CS2 carbon with the upfield shift.
The other carbon nuclei did not show any appreciable deviation in the chemical shift
106
RESULTS AND DISCUSSION
value compared to the parent dithiocarbonate moeity. The signals for methyl (–CH3) and
methylene (–CH2) carbon occurred in the range 19.92–21.63 ppm (10–12, 14–16 and 18–
20) and 70.09–71.40 ppm (13, 17 and 21), respectively. The carbon nuclei of phenyl
groups (–C6H5 and –C6H4) displayed their resonance in the region 112.01–131.81 and
125.98-131.01 ppm, respectively. The carbon attached to the methyl and methylene
group appeared at 124.80–134.32 and 135.61–136.01 ppm, respectively. The signal in the
region 150.38–153.83 ppm was due to the carbon attached to the oxygen in the tolyl
derivatives. The chemical shift for the dithiocarbonate carbon (–CS2) was appeared at
166.94–185.27 ppm with a upfield shift (28-34 ppm) compared to the parent ligands.
Presumably, this reflects the fact that environment around the CS2 carbon is the one most
affected by the formation of the M–S bond. All the chemical shift values are given in the
Table 3.11. The 13C NMR spectra of few of the representative complexes (10, 17 and 20)
are given in Figures 3.15, 3.16 and 3.17.
Mass
Mass spectrometry is one of the most important methods to determine molecular weight
of the complexes and to identify the fragments formed during bombardment. This
reveals composition and properties of the particular moiety of the complexes. Two
important peaks were observed in the mass spectrum: the molecular ion peak and the
base peak. The molecular ion peak indicates the molecular mass of the complex, which
is very weak in the case of the complexes investigated and the base peak is the strongest
peak. The electron impact mass data show the presence of molecular ion peaks
[M(S2COAr)2] [M = Zn, Cd and Hg; Ar = tolyl/benzyl] centered at m/z 431 (10), 478
(15, 16) and 567 (18, 21) in the isotopic cluster of respective metal atom, in addition to
some other peaks of different fragments, which were formed after consecutive dismissal
of different groups. The occurrence of molecular ion peak in the complexes is also
supporting the monomeric nature of the complexes. The systematic mass fragmentation
pattern of the complex (10) is given in Scheme 3.7. Many cracking fragments were
identified with the major species being a free xanthate ligand (S2COAr), a one-ligand
107
RESULTS AND DISCUSSION
complex Zn(S2COAr) and a three coordinate complex Zn(S2COAr)S. The presence of
the ligand and a three coordinate species support the feasibility of processes A and B.
which is consistent with the electron ionization mass data. The major fragments such as
sulfur, cresols, CS2 and ZnS are the expected products of the various pathways. Based
on the presence of the peaks in the mass spectra of some of the representative
complexes, the various fragments have been given in Table 3.12. The mass spectrum of
the representative complex (10) is given in Figures 3.18.
[(ArOCS2)2Zn]
(ArOCS2)
[M+] 183 (30)
ArO +
[M+] 107 (100)
CS2
+
[(ArOCS2)Zn]
[M+] 248 (14)
+ ZnS
B
[M+] 431 (14)
A
+ COS
+
[M ] 60
ArOCS +
[M+] 151 (4)
COS
+
[(ArOCS2)SZn]
[M+] 280 (10)
CS2
+
ArO +
[M+] 76 (50)
ZnS
+
[M ] 97 (20)
Scheme 3.7: Mass fragmentation pattern for the complex [(ArOCS2)2Zn] (10); Ar =
o-CH3C6H4 brackets = m/z; parenthesis = intensities in %.
108
RESULTS AND DISCUSSION
Figure 3.18: Mass spectrum of [Zn(L)2] (10) where L = o-CH3C6H4OCS2
Thermogravimetric Analysis
Now a–day thermal methods of analysis have attracted the interest of researchers because
the technique provides rapid information concerning the thermal stability, composition of
intermediates and final product besides the other physical and chemical properties like
weight, density, structure, magnetic properties which are a function of temperature or
time. The widest application of thermo-gravimetric analysis has been observed in the
investigation of analytical procedures. TGA is regularly used for drying range of
precipitates that involves the change in weight of a system under investigation as the
temperature increased at predetermined rate. The thermal behaviors of the complexes
were studied under inert atmosphere in the range of 30–1000 C and displays weight
losses in steps with different time intervals and at different temperatures. These losses
indicate decomposition and evaporation of the volatile part of the sample. The curved
portion indicates weight loss during process of heating. Thermal methods allow us to
measure changes in physical and chemical properties of a substance as functions of
temperature or time, the shape and size of the peaks can give a large amount of
information about the nature of the sample.255
109
RESULTS AND DISCUSSION
The thermal properties of the complexes were studied by TGA in the temperature
ranging from 30–1000 °C under nitrogen atmosphere. The content of a particular
component in a complex changes with its composition and structure. These can be
determined based on mass losses of these components in the thermo-gravimetric plots of
the complexes. The results are in good agreement with the composition of the complexes.
The calculated mass change agrees favorably with experimental values. The thermogram
from thermal studies performed on the complex [(p-CH3C6H4OCS2)2Zn] (12) is shown in
Figure 3.19. The results show a loss of weight 7.3% (obs.) 6.9% (calc.) due to the
removal of methyl group at approximately 43.9 C. Further heating up to 294.3 °C shows
a gradual weight loss of 42.3% (theoretical weight loss 42.0%) attributable to the
formation of [(OCS2)2Zn]. The weight loss continues beyond this temperature and finally
attains a constant mass corresponding to ZnS (observed 77.3%, calcd. 77.8%) at 450 C.
Figure 3.19: TGA curve for complex [(p-CH3C6H4OCS2)2Zn] (12)
The thermal behavior of bis(o-tolyldithiocarbonato)cadmium(II) complex (14) has
also been followed up to 1000 C (Figure 3.20). In our study, the first thermolytic
cleavage (endothermic) starts at 145 C with 6.5 % loss of weight, corresponding to
methyl group (obs. 6.5 %). The second stage ranges between 150 and 685 C,
110
RESULTS AND DISCUSSION
corresponding to the formation of intermediate [(OCS2)2Cd] having 38.1 % weight loss
(38.9 % obs.), which decomposes at higher temperatures to give CdS at 930 C (69.9%
calc., 69.7 % obs.), after which a straight line is observed, indicating no change above
this temperature range. The experimental mass losses of the compounds are in very good
agreement with the calculated values.
Thermo-gravimetric analysis was performed on the solid mercury xanthate (20)
and the trace can be seen in Figure 3.21. The first derivative of the curve suggests
decomposition occurs in a single step. The elimination begins at a temperature of 100 °C
and is virtually completed by 900 °C. The observed weight loss (32.4 %) at 308 °C is
slightly higher than the loss calculated (32.2 %) for the formation of an intermediate
product [Hg(OCS2)2]. This weight loss continues up to 600 °C and leads to the formation
of mercury sulfide with observed weight loss of 59.5 % (59.1 % calc.). However, the
small discrepancy between observed and calculated weight loss can be explained by the
presence of sulfate and possibly other xanthate decomposition products on the surface.
Figure 3.20: TGA curve for complex [(o-CH2C6H5OCS2)2Cd] (14)
111
RESULTS AND DISCUSSION
Figure 3.21: TGA curve for complex [(p-CH3C6H4OCS2)2Hg] (20)
Cyclic voltammetry
The redox behaviour of a complex of zinc, cadmium and mercury has been studied with
respect to metal centre and shown in Figure 3.22-3.24. The potential is applied between
the reference electrode (Ag/AgCl) and the working electrode (Gold electrode). The
current is measured between the working electrode and the counter electrode (Platinum
wire). 0.1 M Phosphate buffer solution (pH = 7.0) was used. The cyclic voltagramm of
[(p-CH3C6H4OCS2)2Zn] (12) (Figure 3.23) of the complex recorded in the potential
range of +1.0 to –1.0 V, which exhibited the cathodic peak, Epc = 0.60455 V corresponds
to the Zn(II)/Zn(I) redox couple and anodic peak, Epc = -0.52338 V corresponds to
Zn(I)/Zn(II) redox couple. The cathodic peak current is ic= -1.31x10-6 A and anodic peak
current is ia= 1.66x10-6 A. The value of ratio ic/ia is close to unity which corresponds to
simple one electron process and the couple is found to be quasi-reversible. All the metal
complexes (10-13) have almost same redox behaviour because of Zn(II) metal centre.
112
RESULTS AND DISCUSSION
Figure 3.22: Cyclic voltammetric curve of [(p-CH3C6H4OCS2)2Zn] (12)
For the complex [m-CH3C6H4OCS2)2Cd] (15) the cathodic peak is found to be Epc
= -0.26V for Cd(II)/Cd(I) couple and anodic peak is Epa = 0.62V for Cd(I)/Cd(II). The
corresponding anodic and cathodic currents are ic = -8.4 x 10-7 and ia = 1.0 x 10-6 A. The
ratio to anodic and cathodic current is found to be ic/ia = 0.8 which is close to unity
corresponding to simple one-electron process as shown in Figure 3.23.
Figure 3.23: Cyclic voltammetric curve of [(m-CH3C6H4OCS2)2Cd] (15)
The complex [(p-CH3C6H4OCS2)2Hg] (20) is electroactive with respect to the
metal centre. The cyclic voltammogram (Figure 3.24) of the complex in the potential
113
RESULTS AND DISCUSSION
range of +2.5 to -1.5V at a scan rate of 100mV/s exhibited two redox processes; each
reduction is associated with a single-electron transfer process. Two well-defined oneelectron cyclic responses were observed. First reduction peak was observed at Epc =
1.878V with the cathodic peak current, ic = 5.56 x 10-5 A and a corresponding oxidation
peak at Epa = -0.465V with the anodic peak current, ic = -2.27 x 10-5 A. The second redox
process was related with the reduction peak at Epc = -1.127V with the cathodic peak
current, ic = -3.19 x 10-5 A, with a corresponding oxidation peak at Epa = 0.733V with the
anodic peak current, ic = -1.2 x 10-5 A.
Figure 3.24: Cyclic voltammetric curve of [(p-CH3C6H4OCS2)2Hg] (20)
Scanning Electron Microscopy (SEM)
Scanning electron microscopy is used to evaluate morphology and particle size of the [(oCH3C6H4OCS2)2Zn] (10) and has been carried out at a low and high magnification
Figure 3.25(a-b). The information revealed from the signals included external
morphology, topography, structure and orientation of materials making up the sample.
The images show the round shape of particles with rough texture. The particles are
present in the form of clusters. In general, the SEM photograph shows single phase
formation with well-defined shape.
114
RESULTS AND DISCUSSION
Figure 3.25: SEM image of [(o-CH3C6H4OCS2)2Zn] (10) complex (a) low
magnification; (b) high magnification
115
Table 3.9: IR spectral data of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonates of zinc(II), cadmium(II) and mercury(II)
(10–21) (in cm–1)
S. No.
Compound
v(C
S)
v(C–O–C)
v(C
C)
v(Zn–S)
v(Cd–S)
v(Hg–S)
[(o-CH3C6H4OCS2)2Zn]
1032, s
1238, s
1581, b
370, m
-
-
11.
[(m-CH3C6H4OCS2)2Zn]
1034, s
1236, s
1579, b
365, m
-
-
12.
[(p-CH3C6H4OCS2)2Zn]
1030, s
1235, s
1574, b
364, m
-
-
13.
[(C6H5CH2OCS2)2Zn]
1034, s
1230, s
1571, b
360, m
-
-
14.
[(o-CH3C6H4OCS2)2Cd]
1032, s
1238, s
1597, b
-
351, m
-
15.
[(m-CH3C6H4OCS2)2Cd]
1040, s
1239, s
1594, b
-
347, m
-
16.
[(p-CH3C6H4OCS2)2Cd]
1038, s
1247, s
1613, b
-
356, m
-
17.
[(C6H5CH2OCS2)2Cd]
1022, s
1250, s
1596, b
-
340, m
-
18.
[(o-CH3C6H4OCS2)2Hg]
1020, s
1242, s
1612, b
-
-
289, m
19.
[(m-CH3C6H4OCS2)2Hg]
1029, s
1248, s
1607, b
-
-
280, m
20.
[(p-CH3C6H4OCS2)2Hg]
1021, s
1233, s
1615, b
-
-
290, m
21.
[(C6H5CH2OCS2)2Hg]
1015, s
1236, s
1618, b
-
-
286, m
s = strong, b = broad, m = medium and w = weak
116
RESULTS AND DISCUSSION
10.
Table 3.10: 1H NMR spectral data of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonates of zinc(II), cadmium(II) and
mercury(II) (10–21) in CDCl3 (in ppm)
1
#
S. No.
–CH3/–CH2
H NMR
Tolyl/Benzyl moiety
H3C
4
5
4'
O
3
2
1
5'
CH2
3'
OR
2'
1'
2.21, s, 6H
7.00, d, 2H [H(2)]; 6.77, t, 2H [H(3)]; 6.97, t, 2H [H(4)]; 6.74, d, 2H [H(5)]
11.
2.23, s, 6H
6.84, s, 2H [H(1)]; 6.94, d, 2H [H(3)]; 7.04, t, 2H [H(4)]; 6.70, d, 2H [H(5)]
12.
2.10, s, 6H
6.75, d, 4H [H(1,5)]; 7.03, d, 4H [H(2,4)]
13.
4.29, s, 4H
7.01–7.21, m, 10H [H(1’–5’)]
14.
2.28, s, 6H
7.06, d, 2H [H(2)]; 6.74, t, 2H [H(3)]; 6.99, t, 2H [H(4)]; 6.78, d, 2H [H(5)]
15.
2.32, s, 6H
6.89, s, 2H [H(1)]; 6.97, d, 2H [H(3)]; 7.14, t, 2H [H(4)]; 6.73, d, 2H [H(5)]
16.
2.18, s, 6H
6.78, d, 4H [H(1,5)]; 7.13, d, 4H [H(2,4)]
17.
4.47, s, 4H
7.12–7.24, m, 10H [H(1’–5’)]
18.
2.26, s, 6H
7.10, d, 2H [H(2)]; 6.73, t, 2H [H(3)]; 6.95, t, 2H [H(4)]; 6.76, d, 2H [H(5)]
19.
2.32, s, 6H
6.74, s, 2H [H(1)]; 6.84, d, 2H [H(3)]; 7.09, t, 2H [H(4)]; 6.77, d, 2H [H(5)]
20.
2.37, s, 6H
6.74, d, 4H [H(1,5)]; 7.03, d, 4H [H(2,4)]
4.35, s, 4H
7.09–7.25, m, 10H [H(1’–5’)]
21.
#
s = singlet, d = doublet, t = triplet; S. No. of the complexes is according to Table 3.9.
117
RESULTS AND DISCUSSION
10.
Table 3.11: 13C NMR spectral data of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonates of zinc(II), cadmium(II) and
mercury(II) (10–21) in CDCl3 (in ppm)
#
–C–O
CHn
C(CHn)
(n=2 or 3)
(n=2 or 3)
10.
19.92
124.80
152.88
114.20
129.47,129.88
120.61
168.64
11.
20.31
134.32
150.38
112.01,115.10
131.81
120.01
166.94
12.
20.24
129.47
150.81
115.20
129.88
––
169.02
13.
71.40
135.96
––
126.51
127.30
128.61
180.96
14.
20.80
125.93
153.77
115.51
127.61, 129.86
119.25
169.29
15.
21.32
134.01
153.14
113.91, 117.32
130.32
122.33
168.56
16.
21.13
134.11
151.63
120.83
128.33
––
167.87
17.
71.29
135.61
––
126.61
127.40
128.96
182.90
18.
20.72
124.93
153.83
119.71
125.72, 128.73
120.28
167.87
19.
21.63
129.87
150.89
119.42, 121.89
124.64
120.47
168.23
20.
21.10
130.41
150.81
120.15
129.85
––
169.47
21.
70.09
136.01
––
125.98
126.84
131.01
185.27
Cortho
S. No. of the complexes is according to Table 3.9.
CH3C6H4O/C6H5CH2O
Cmeta
(O)–C–S
Cpara
118
RESULTS AND DISCUSSION
#
S.No
Table 3.12: Mass spectral data of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonates of zinc(II), cadmium(II) and mercury(II)
(10–21)
#
S. No.
M.W.
m/z, relative intensities of the ions and assignment
431.9
[M+] 431 (14) [(o-CH3C6H4OCS2)2Zn]; [M+] 280 (10) [(o-CH3C6H4OCS2)ZnS];
[M+] 248 (14) [(o-CH3C6H4OCS2)Zn]; [M+] 151 (4) [o-CH3C6H4OCS2];
[M+] 183 (30) [o-CH3C6H4OCS2]; [M+] 107 (100) [o-CH3C6H4O]; [M+] 97 (20) [ZnS];
[M+] 76 (50) [CS2].
15.
478.9
[M+] 478 (21) [(m-CH3C6H4OCS2)2Cd]; [M+] 448 (15) [(C6H4OCS2)2Cd];
[M+] 328 (14) [(m-CH3C6H4OCS2)CdS]; [M+] 183 (30) [o-CH3C6H4OCS2];
[M+] 107 (100) [o-CH3C6H4O]; [M+] 144 (21) [CdS]; [M+] 76 (46) [CS2].
16.
478.9
[M+] 478 (21) [(C6H5CH2OCS2)2Cd]; [M+] 328 (14) [(C6H5CH2OCS2)CdS];
[M+] 183 (30) [C6H5CH2OCS2]; [M+] 107 (100) [C6H5CH2O]; [M+] 144(20) [CdS];
[M+] 76 (70) [CS2].
18.
567.1
[M+] 567 (12) [(o-CH3C6H4OCS2)2Hg]; [M+] 416 (19) [(o-CH3C6H4OCS2)HgS];
[M+] 183 (17) [o-CH3C6H4OCS2]; [M+] 107 (100) [o-CH3C6H4O]; [M+] 76 (50) [CS2];
[M+] 232 (23) [HgS].
[M+] 567 (11) [(C6H5CH2OCS2)2Hg]; [M+] 416 (18) [(C6H5CH2OCS2)HgS];
[M+] 183 (17) [C6H5CH2OCS2]; [M+] 107 (100) [C6H5CH2O]; [M+] 76 (52) [CS2];
[M+] 232 (22) [HgS].
#
S. No. of the complexes is according to Table 3.9
21.
567.1
119
RESULTS AND DISCUSSION
10.
RESULTS AND DISCUSSION
Figure 3.9: The IR Spectrum of [(o-CH3C6H4OCS2)2Zn] (10)
Figure 3.10: The IR Spectrum of [(C6H5CH2OCS2)2Cd] (17)
120
RESULTS AND DISCUSSION
Figure 3.11: The IR Spectrum of [(p-CH3C6H4OCS2)2Hg] (20)
Figure 3.12: The 1H Spectrum of [(o-CH3C6H4OCS2)2Zn] (10)
121
RESULTS AND DISCUSSION
Figure 3.13: The 1H Spectrum of [(C6H5CH2OCS2)2Cd] (17)
Figure 3.14: The 1H NMR Spectrum of [(p-CH3C6H4OCS2)2Hg] (20)
122
RESULTS AND DISCUSSION
Figure 3.15: The 13C NMR Spectrum of [(o-CH3C6H4OCS2)2Zn] (10)
Figure 3.16: The 13 C NMR Spectrum of [(C6H5CH2OCS2)2Cd] (17)
123
RESULTS AND DISCUSSION
Figure 3.17: The 13 C NMR Spectrum of [(p-CH3C6H4OCS2)2Hg] (20)
124
RESULTS AND DISCUSSION
Structural Features
It would not be possible to predict a concise and precise structure of these compounds
without X-ray crystal. Number of attempts have been made to form crystals but
unable to get a crystal of desirable diffraction. However, on the basis of elemental
analyses and spectral studies like mass, TGA, CV, IR and multinuclear NMR have
supported the formation of these compound and monomeric nature as well. Moreover,
dithiocarbonates are expected to resemble dithiocarbamates in their bonding mode.208
The normal mode of attachment of dithiocarbonate ligand with the metal is bidentate
chelating.219-220,
249-254
The IR, 1H and 13C NMR data as discussed above indicated
that both the dithiocarbonate moieties in these complexes are equivalent and are
attached to the metal atom in bidentate manner. The occurrence of upfield shift in the
range of 28–34 ppm in the
13
C NMR spectra provides an indication of bidentate
linkage in these complexes. In addition, appearance of M–S bond in the far IR
spectra also indicates the complexation between the metal and dithio ligand. Thermogravimetric analysis of the complexes showed weight loss to give metal sulfide (MS)
indicating that the complexes will be good single source precursors for MS
semiconductor nanoparticles. The potential of the complexes as single source
precursors for semiconductor nanoparticles is being investigated. Hence, on the basis
of above studies and in conjunction with the literature reports,141,
148, 166, 256-258, 274
mononuclear species with two chelating dithiocarbonate ligands that form a distorted
tetrahedral array around the metal centre. Thus coordination geometry around the
metal atom is best described as a distorted tetrahedral arrangement of the four sulfur
atoms [MS4] i.e. two sulphur atoms from each dithiocarbonate moiety as described in
Figure 3.26 (a) and 3.26 (b).
125
RESULTS AND DISCUSSION
CH3
CH3
S
S
C O
M
O C
S
S
(a)
H2
C O
S
S
C
M
H2
C O C
S
S
(b)
Figure 3.26: Proposed distorted tetrahedral geometry for (a) [(o-, m- and pCH3C6H4OCS2)2M] (10-12, 14-16and 18-20); (b) [(C6H5CH2OCS2)2M] (13, 17
and 21); M = Zn, Cd and Hg.
126
RESULTS AND DISCUSSION
3.5.2: Mixed dithiocarbonato–dithiophosphato complexes of
zinc(II), cadmium(II) and mercury(II) (22-33)
In recent years, there has been renewed interest in the synthesis and study of mixed
ligand transition metal complexes. 259-264 The utility aspects of these complexes have
received their share of attention as these have found applications in diverse fields.261,
262
Chiral metal complexes are well known for their use as catalysts, especially in
asymmetric synthesis, asymmetric epoxidations or Sharpless epoxidations and
resolution of racemic compounds.262a The binary and ternary mixed ligand complexes
of transition metal complexes have shown potential biological activity.262b It is well
known that mixed ligand ternary complexes of some metals play an important role in
the activation of enzymes and are used for storage as well as as for transport of active
materials. It is studied that these complexes are biologically active against pathogenic
microorganisms. Mixed ligand complexes have been receiving considerable attention
largely due to their considerable importance in the field of the metalloenzymes and
other biological activities.262b Literature survey revealed several reports on the mixed
ligand complexes of various metal and metalloids.259-264 It is rather interesting that
though several mixed ligand complexes of dithiophosphates with dithiocarbamates260
are known but no report available on mixed dithiophosphate–dithiocarbonate ligand.
So, it was thought interesting to investigate mixed dithiophosphate–dithiocarbonate
ligand complexes of zinc triad in order to create a variety of complexes within the
dithiocarbonate periphery and also to find its biological activity.
Dithiocarbonate derivatives of Zn(II), Cd(II) and Hg(II) corresponding to [(o-,
m- and p-CH3C6H4)/C6H5CH2OCS2)M{S2POCH2C(CH3)2CH2O}] were synthesized
by the
reaction of
sodium
CH3C6H4O)/C6H5CH2OCS2)Na
tolyl/benzyldithiocarbonates,
and
sodium
neopentylene
(o-,
m- and
p-
phosphorodithioate
OCH2C(CH3)2CH2OPS2Na with metal chloride in in 1:1:1 molar ratio in aqueous
medium. The complexes 22-33 were isolated as white to yellow solid in 69-79 %
yield (Scheme 3.8).
127
RESULTS AND DISCUSSION
H2O
(ArOCS2)Na + OGOPS2Na + ZnCl2
stirring
(5)
(1-4)
~30 min
[(ArOCS2)Zn(S2POGO)] + 2NaCl
H2O
(ArOCS2)Na + OGOPS2Na + CdCl2
stirring
(5)
(1-4)
~30 min
[(ArOCS2)Cd(S2POGO)] + 2NaCl
H2O
(ArOCS2)Na + OGOPS2Na + HgCl2
stirring
(5)
(1-4)
~30 min
[(ArOCS2)Hg(S2POGO)] + 2NaCl
(22-25)
(26-29)
(30-33)
Scheme 3.8: Synthesis of [(ArOCS2)Zn(S2POGO)] (22-25);
[(ArOCS2)Cd(S2POGO)] (26-29); [(ArOCS2)Hg(S2POGO)] (30-33) [ G =
{OCH2C(CH3)2CH2O}; Ar = o–, m– or p–CH3C6H4– (22-24, 26–28, 30-32) and
C6H5CH2– (25, 29, 33)]
These complexes are soluble in common organic solvents viz. toluene,
acetonitrile, methanol, chloroform etc but are insoluble in solvents like n–hexane and
carbon tetrachloride. The elemental analyses, particularly C, H, S, Zn, Cd and Hg
were found consistent with the molecular formula of these complexes.
The complexes were further characterized by mass, TGA, IR and multinuclear
NMR (1H, 13C, 31P) spectroscopy. These studies showed that the coordination mode of
both ligand types is bidentate.
Infrared
IR spectral assignment of the complexes (22–33) is done on the basis of relevant
literature reports.219-220, 249-254, 265-269 The comparison of IR spectra of these complexes
with starting materials has also shown seminal information. The absorption band
v(C─O─C) vibrations was found in the region 1245–1203 cm-1 which is characteristic
for the bidentate mode of bonding by the dithiocarbonate ligand.249 The v(C
H)
vibrations (due to the tolyl/benzyl ring) were observed in the region 3039–3018 cm-1.
A band in the region 1597–1592 cm-1 may be attributed to the v(C
C) ring
128
RESULTS AND DISCUSSION
vibrations. The appearance of only one strong band for v(C
S) vibrations in the
-1
range 1044–1024 cm without a shoulder indicates the bidentate behavior of the
dithiocarbonate ligand. The v(P–S)asym and v(P–S)sym mode may be characterized by
the presence of a band in the region 629–618 and 555–540 cm-1, respectively
indicating the bidentate nature of dithiophosphate ligands. Two strong intensity bands
were observed in the region 949–935 and 849–834 cm–1, which may be ascribed to
the ν(P)−O−C and νP−O−(C) vibrations of the alkylene dithiophosphate moiety,
respectively. Thus the latter reduces the electron releasing ability of the xanthate
group. The shift of νP−S and νC
S vibrations compared to the parent ligands is due
to the bidentate mode of bonding by the dithio ligands with metal. The presence of a
new band for ν(M−S); where M = Zn, Cd and Hg was observed in the region 371–
364, 356–341 and 289–280 cm–1, respectively. The occurrence of band for ν(M−S) is
an indicative of the formation of metal–sulfur bond i.e. complexation of metal atom
with dithiocarbonate and dithiophosphate moieties. In contrast, the absence of M—Cl
band in these complexes 22-33 is again give an indication for the formation of new
M—S bonds. The relevant IR spectral data of these complexes are given in Table
3.13. The IR spectra of few of the representative complexes (22, 27, 32 and 33) are
given in Figures 3.27, 3.28, 3.29 and 3.30.
1
H NMR
The 1H NMR chemical shifts of the mixed ligand complexes of zinc, cadmium and
mercury with dithio ligands are given in Table 3.14. The 1H NMR spectra (CDCl3) of
the complexes (22-33) exhibited the characteristic resonance for methyl and aryl
protons. The chemical shifts for the methyl protons of the tolyldithiocarbonate moiety
in the complexes 22-24, 26-28, 30-32 were appeared as singlet at 2.10–2.37 ppm
whereas the methylene protons of the benzyldithiocarbonate moiety in the complexes
25, 29, 33 were resonated at 4.41–4.43 ppm as singlet. The protons of the tolyl and
benzyl ring in the complexes gave signals in the range 6.62–7.13 ppm for the
complexes 22-24, 26-28, 30-32 and 7.01–7.25 ppm for the 25, 29, 33, respectively.
There were two resonances for the ring protons of para complexes whereas four
129
RESULTS AND DISCUSSION
resonances were observed for ortho and meta derivatives. The resonance for
individual protons is specified in the Table 3.14. The chemical shift for the protons
of the –CH3 attached to the neopentylene moiety was observed at 0.90–1.12 ppm as a
singlet and protons of –OCH2 appear at 3.20-3.45 ppm as a singlet. The values of the
chemical shifts are found to be in similar range to those of the ligands from which
these were prepared. Hence, there is no significant changes were observed as a result
of being linked to different metals. The 1H NMR spectra of few of the representative
complexes (22, 27, 32 and 33) are given in Figures 3.31, 3.32, 3.33 and 3.34.
31
P NMR
The phosphorus atom of the dithiophosphate moiety in these complexes (22-33)
appears as a singlet in the region 77.32–86.01 ppm with the upfield shift compared to
corresponding free ligand in the
31
P NMR spectra. The occurrence of singlet is
indicating its equivalent nature in the molecule. It has been proposed that the
difference in the phosphorus chemical shift values between the corresponding ligand
(5) and the complex is a strong indicator of bidentate mode of bonding of Zn, Cd and
Hg with the dithiophosphate ligand. This singlet also signifies the symmetric nature of
the phosphorus atom. The range observed for 31P nucleus present in these complexes
is consistent with bidentate behavior of dithiophosphate moiety according to
Glidewell.169d The
31
P spectral data of all these complexes are summarized in Table
3.14. The 31P NMR spectra of few of the representative complexes (22, 27, 32 and
33) are given in Figures 3.35, 3.36, 3.37 and 3.38.
13C
The
NMR
13
C NMR spectra of the complexes (22-33) show the chemical shifts due to the
carbons of aryl rings with a marginal shift in their values compared to the parent
ligand. The chemical shifts for the methyl carbon (–CH3) and methylene carbon (–
CH2) attached to tolyl and benzyl ring were found in the region 19.80–21.62 and
61.52–64.01 ppm, respectively. The carbon nuclei of the aryl groups (tolyl and benzyl
130
RESULTS AND DISCUSSION
groups) have displayed their resonance in the region 119.41–142.81 ppm. The
chemical shifts for C−O carbon of the dithiocarbonate and dithiophosphate moieties
were found in the region 149.14–151.90 ppm and 72.01–73.09 ppm, respectively. The
chemical shift for the dithiocarbonate carbon (–OCS2) was appeared at 168.02–185.27
ppm with an upfield shift (25–30 ppm) compared to the parent ligands, which may be
correlated with the coordination of the dithiocarbonate ligand with the respective
metal atom i.e. Zn, Cd and Hg. The –C– and –CH3 carbon nuclei of the neopentylene
moiety have shown their chemical shifts at 30.90–31.18 and 21.11–21.92 ppm,
respectively. The
13
C NMR spectral data of these compounds are summarized in
Table 3.15. The 13C NMR spectra of few of the representative complexes (22, 27, 32
and 33) are given in Figures 3.39, 3.40, 3.41 and 3.42.
Mass
The result of ionization, ion separation and detection is a mass spectrum that can
provide molecular weight or even structural information. The mass spectra of few
representative complexes 22, 25, 27 and 32 have been summarized in Table 3.16.
This data provide evidence for its discrete monomeric nature as there is no fragment
of mass higher than the monomeric species 445 (22, 25), 493 (27) and 581 (32) was
observed. Two important peaks were observed in the mass spectrum: First is the
molecular ion peak which is indicating the molecular mass of the complex, this is
very weak in the case of the complexes investigated. The second one is the base peak
corresponding to the fragment having high intensity. In general, mixed sulfur donor
ligand complexes do not show a very strong molecular ion peak, which may be due to
a pyrolytic decomposition because of the relatively high temperature or due to the
fragmentation of molecular ion in the ionization chamber. Also the relative intensity
of the molecular ion peak decreases as the degree of branching increases in the
complex. We observe weak molecular ion peaks surrounded by isotopic cluster of
their respective metal for the representative complexes. In the mass spectrum of the
[(m-CH3C6H4OCS2)Cd(S2POCH2C(CH3)2CH2O)] (27), molecular ion peak was observed
at
m/z 493 (17), which is surrounded by isotopic cluster and a peak for
131
RESULTS AND DISCUSSION
dithiocarbonate moiety [(m-CH3C6H4OCS2)Cd)] at 296 (40). From this scheme we
conclude that a dithiophosphate ligand is lost and its peaks are observed at m/z 197
(32). The base peak, which was observed at m/z 107 in the complexes due to [mCH3C6H4O], indicates the relative abundance of the respective group. The presence of
the dithiocarbonate moiety in the fragmentation pattern shows that dithiocarbonates
are stronger chelating agents as compared to alkylenedithiophosphate ligand. The
mass spectrum of the representative complex (27) is as shown in Figure
3.43.
[(m-CH3C6H4OCS2)Cd(S2POCH2C(CH3)2CH2O]
[M+] 493 (17)
[(S2POCH2C(CH3)2CH2O]
[(m-CH3C6H4OCS2)Cd]
[M+] 197 (32)
[M+] 296 (40)
(m-CH3C6H4O) +
[M+] 107 (100)
CS2
[M+] 76 (60)
+
CdS
+
[M+] 144 (40)
[SPOCH2C(CH3)2CH2O]
[M+] 164 (10)
Scheme 3.9: Mass fragmentation pattern of
[(m-CH3C6H4OCS2) Cd (S2POCH2C(CH3)2 CH2O)] (27) brackets = m/z; parenthesis =
intensities in %
132
RESULTS AND DISCUSSION
Figure 3.43: Mass fragmentation pattern of complex (27) CdLL’ where L = (mCH3C6H4OCS2); L’ = ((S2POCH2C(CH3)2CH2O)]
Thermogravimetrical Analysis
The
thermal
behavior
of
CH3C6H4OCS2)Cd{S2POC(CH3)2C(CH3)2O}]
the
(26)
was
complex
studied
under
[(pinert
atmosphere in the range of 25–1000 C (Figure 3.44) that displays weight losses in
three steps with different time intervals and at different temperatures. In thermal
analysis of the complex there are different temperature ranges visible, in which
decomposition of the sample occurs. In the first decomposition step, there is a weight
loss of 32.9 % (calc.) 32.8 % (obs.) which lead to the formation of fragment
[(OCS2)Cd(S2PO2)] at 222 C. In the second step of decomposition, there is a weight
loss of 58.6 % at 622.7 C, leading to the formation intermediate product [Cd(OCS2)].
In the final decomposition step, the total weight loss of 70.8 % calc. (70.6 % obs.)
strongly supports CdS as the final product after complete decomposition. The above
observations indicate the formation of the cadmium sulfide as the final decomposition
product of the complex 26. Similar path way is followed for rest of the derivatives of
mixed complex of dithiocarbonates and dithiophosphate of group 12th elements and
lead to the formation of metal sulfides as the end product of this thermolytic pathway.
133
RESULTS AND DISCUSSION
Figure 3.44: TGA curve for
[(p-CH3C6H4OCS2)Cd{S2POC(CH3)2C(CH3)2O}] (26)
Scanning Electron Microscopy (SEM)
Scanning electron microscopy study of one of the synthesized complex (26) has been
carried out at different magnification. SEM uses a focused beam of high-energy
electrons to generate a variety of signals from the surface of a solid specimen. The
signals reveal information about the sample, including external morphology,
topography, chemical composition, crystalline structure and orientation of materials
making up the sample. We recorded different images of this complex at different
magnifications as described above. Complex has a different topography and
morphology at the two different magnifications. In the images, rough texture appears
with grooves and ridges on the surface. The particles exhibit different sizes and
shapes and are present in the form of clusters (Figures 3.45 (a)-(b)). SEM studies
show microstructures of the complexes, which mainly include surface morphology.
134
RESULTS AND DISCUSSION
(a)
(b)
Figure 3.45: SEM image of [(p-CH3C6H4OCS2)Cd{S2POCH2C(CH3)2CH2O}]
(26) complex (a) low magnification; (b) high magnification
135
Table 3.13: IR spectral data of mixed dithiocarbonato–dithiophosphato derivatives of zinc(II), cadmium(II) and mercury(II) (22-33) (in
cm-1)
S.
v(C-O-C)
v(C
S)
v(C-H)
v(C
C)
v(P)-O-C
vP-O-(C)
v(P-S)asym
v(P-S)sym
v(M-S)
1597, s
944, s
844, s
626, s
534, m
371, m
3033, b
1596, s
947, s
843, s
623, s
542, m
364, m
1037, s
3022, b
1593, s
946, s
838, s
627, s
552, m
367, m
1213, s
1043, s
3022, b
1593, s
940, s
842, s
622, s
544, m
364, m
[(o-ArOCS2)Cd(S2POGO)]
1238, s
1038, s
3020, b
1596, s
935, s
834, s
621, s
549, m
27.
[(m-ArOCS2)Cd(S2POGO)]
1224, s
1044, s
3018, b
1594, s
937, s
837, s
629, s
551, m
356, m
28.
[(p-ArOCS2)Cd(S2POGO)]
1218, s
1042, s
3030, b
1595, s
946, s
839, s
624, s
545, m
344, m
[(ArOCS2)Cd(S2POGO)]
1241, s
1038, s
3037, b
1592, s
949, s
841, s
623, s
540, m
341, m
Compound
22.
[(o-ArOCS2)Zn(S2POGO)]
1203, s
1044, s
3018, b
23.
[(m-ArOCS2)Zn(S2POGO)]
1215, s
1037, s
24.
[(p-ArOCS2)Zn(S2POGO)]
1232, s
25.
[(ArOCS2)Zn(S2POGO)]
26.
29.
(aromatic stretching)
349, m
136
RESULTS AND DISCUSSION
No.
30.
[(o-ArOCS2)Hg(S2POGO)]
1245, s
1042, s
3035, b
1594, s
939, s
846, s
627, s
555, m
289, m
31.
[(m-ArOCS2)Hg(S2POGO)]
1237, s
1034, s
3031, b
1593, s
945, s
844, s
620, s
547, m
285, m
32.
[(p-ArOCS2)Hg(S2POGO)]
1238, s
1029, s
3039, b
1596, s
947, s
847, s
618, s
544, m
280, m
33.
[(ArOCS2)Hg(S2POGO)]
1232, s
1038, s
3020, b
1594, s
942, s
849, s
621, s
550, m
287, m
Where, Ar = CH3C6H4/C6H5CH2; G = CH2C(CH3)2CH2; Zn (22-25), Cd (26-29) and Hg (30-33)
s = sharp, b = broad, m = medium
RESULTS AND DISCUSSION
137
Table 3.14: 1H NMR and
31
P NMR spectral data of mixed dithiocarbonato–dithiophosphato derivatives of zinc(II), cadmium(II) and
mercury(II) (22-33) CDCl3 (in ppm)
Neopentylene moiety
Tolyl / Benzyl moiety
H3C
4
5
O
3
#
S. No.
-CHn
4'
2
1
or
(CH3)2C
CH2
CH2
2'
P
NMR
CH2
5'
3'
31
1'
-CH3
-CH2
2.10, s, 3H
7.01, d, H, [H(2)]; 6.71, t, H, [H(3)]; 6.92, t, H, [H(4)]; 6.69, d, H, [H(5)]
1.11, s, 6H
3.45, s, 4H
23.
2.32, s, 3H
6.81, s, H, [H(1)]; 6.62, d, H, [H(3)]; 7.04, t, H, [H(4)]; 6.82, d, H, [H(5)]
1.10, s, 6H
3.42, s, 4H
78.21, s
24.
2.25, s, 3H
6.91, d, 2H, [H(1,5)]; 7.03, d, 2H, [H(2,4)]
1.12, s, 6H
3.23, s, 4H
77.90, s
25.
4.41, s, 2H
7.11–7.24, m, 5H [H(1’–5’)]
1.11, s, 6H
3.45, s, 4H
78.01, s
26.
2.34, s, 3H
1.10, s, 6H
3.42, s, 4H
85.43, s
7.10, d, H [H(2)]; 6.73, t, H [H(3)]; 6.95, t, H [H(4)]; 6.76, d, H [H(5)]
77.32, s
138
RESULTS AND DISCUSSION
22.
27.
2.25, s, 3H
6.74, s, H [H(1)]; 6.84, d, H [H(3)]; 7.09, t, H [H(4)]; 6.77, d, H [H(5)]
1.12, s, 6H
28.
2.31, s, 3H
6.75, d, 2H [H(1,5)]; 7.03, d, 2H [H(2,4)]
29.
4.41, s, 2H
30.
85.03, s
0.90, s, 6H
3.21, s, 4H
85.45, s
7.09–7.25, m, 5H [H(1’–5’)]
1.11, s, 6H
3.45, s, 4H
86.01, s
2.34, s, 3H
7.00, d, H [H(2)]; 6.77, t, H [H(3)]; 6.97, t, H [H(4)]; 6.74, d, H [H(5)]
1.10, s, 6H
3.40, s, 4H
79.28, s
31.
2.37, s, 3H
6.84, s, H [H(1)]; 6.94, d, H [H(3)]; 7.04, t, H [H(4)]; 6.70, d, H [H(5)]
1.12, s, 6H
3.20, s, 4H
79.90, s
32.
2.10, s, 3H
6.77, d, 2H [H(1,5)]; 7.13, d, 2H [H(2,4)]
1.11, s, 6H
3.43, s, 4H
79.92, s
33.
4.43, s, 2H
7.01–7.21, m, 5H [H(1’–5’)]
1.12, s, 6H
3.20, s, 4H
Where, s = singlet, d = doublet, t = triplet;
#
S. No. of the complexes is according to Table 3.13.
81.01, s
139
RESULTS AND DISCUSSION
3.23, s, 4H
Table 3.15: 13C NMR spectral data of mixed dithiocarbonato–dithiophosphato derivatives of zinc(II), cadmium(II) and mercury(II) (2233) in CDCl3 (in ppm)
#
C(CHn)
(n=2 or 3)
–C–O
22.
19.80
129.92
149.14
120.11
127.61, 128.11
126.61
169.64
72.01
31.13
21.84
23.
19.92
124.02
149.62
119.41, 124.61
126.81
123.80
168.94
72.09
31.18
21.81
24.
19.91
122.61
150.61
121.10
130.41
––
168.02
72.17
30.90
21.72
25.
61.62
142.72
––
125.80
131.01
126.71
182.96
73.09
31.16
21.79
26.
20.81
121.90
150.41
121.51
125.61, 126.81
122.22
168.29
72.90
31.10
21.12
27.
20.22
136.82
150.81
120.61, 124.23
134.64
131.88
168.56
72.91
31.18
21.17
28.
19.52
130.12
150.61
120.81
128.30
––
169.87
72.78
30.98
21.23
29.
64.01
142.81
––
125.31
130.41
126.21
183.62
73.01
31.01
21.11
30.
20.72
122.91
152.82
119.71
125.72, 128.71
120.22
168.87
72.67
31.00
21.92
31.
21.62
126.81
150.81
119.41, 121.82
124.62
120.41
169.23
72.98
31.09
21.23
32.
21.11
130.42
151.90
120.11
129.82
––
169.45
72.56
31.13
21.39
33.
61.52
141.02
––
125.91
119.41-131.01
126.81
185.27
73.01
30.99
21.22
Tolyl/Benzyl moiety
Cortho
S. No. of the complexes is according to Table 3.13.
Cmeta
(O)–C–S
Neopentylene moiety
–CO–
Cpara
–C–
–CH3
RESULTS AND DISCUSSION
140
#
CHn
(n=2 or 3)
S.No
Table 3.16: Mass spectral data of some mixed dithiocarbonato–dithiophosphato derivatives of zinc(II), cadmium(II) and mercury(II)
(22-33)
#
S. No.
M.W.
22.
445.9
m/z, relative intensities of the ions and assignment
[M+] 445 (17) [(o-CH3C6H4OCS2)Zn(S2POCH2C(CH3)2CH2O)]; [M+] 248 (9) [(o-CH3C6H4OCS2)Zn];
[M+] 197 (27) [S2POCH2C(CH3)2CH2O];[M+] 165 (11) [SPOCH2C(CH3)2CH2O];
[M+] 107 (100) [o-CH3C6H4O]; [M+] 76 (59) [CS2]; [M+] 97(27) [ZnS].
25.
445.9
[M+] 445 (13) [(C6H5CH2OCS2)Zn(S2POCH2C(CH3)2CH2O)]; [M+] 248 (11) [(C6H5CH2OCS2)Zn];
[M+] 197 (20) [(S2POCH2C(CH3)2CH2O]; [M+] 165 (17) [SPOCH2C(CH3)2CH2O];
[M+] 107 (100) [C6H5CH2O]; [M+] 76 (60) [CS2]; [M+] 97 (27) [ZnS].
27.
493.8
[M+] 493 (17) [(m-CH3C6H4OCS2)Cd(S2POCH2C(CH3)2CH2O)]; [M+] 197 (32) [(S2POCH2C(CH3)2CH2O)];
[M+] 144 (40) [CdS]; [M+] 107 (100) [m-CH3C6H4O]; [M+] 76 (60) [CS2].
32.
581.0
[M+] 581(17) [(p-CH3C6H4OCS2)Hg(S2POCH2C(CH3)2CH2O)]; [M+] 383 (12) [(p-CH3C6H4OCS2)Hg];
[M+] 232 (37) [HgS]; [M+] 197 (28) [(S2POCH2C(CH3)2CH2O)]; [M+] 164 (11) [SPOCH2C(CH3)2CH2O];
[M+] 107 (100) [p-CH3C6H4O]; [M+] 76 (84) [CS2].
#
141
S. No. of the complexes is according to Table 3.13.
RESULTS AND DISCUSSION
[M+] 296 (40) [(m-CH3C6H4OCS2)Cd]; [M+] 165 (11) [SPOCH2C(CH3)2CH2O];
RESULTS AND DISCUSSION
Figure 3.27: The IR Spectrum of [(o-CH3C6H4OCS2)Zn(S2POCH2C(CH3)2CH2O)]
(22)
Figure 3.28: The IR Spectrum of [(m-CH3C6H4OCS2)Cd(S2POCH2C(CH3)2CH2O)]
(27)
142
RESULTS AND DISCUSSION
Figure 3.29: The IR Spectrum of [(p-CH3C6H4OCS2)Hg(S2POCH2C(CH3)2CH2O)]
(32)
Figure 3.30: The IR Spectrum of [(C6H5CH2OCS2)Hg(S2POCH2C(CH3)2CH2O)]
(33)
143
RESULTS AND DISCUSSION
Figure 3.31: The 1H Spectrum of [(o-CH3C 6H4OCS2)Zn(S2POCH2C(CH3)2CH2O)]
(22)
Figure 3.32: The 1H Spectrum of [(m-CH3C6H4OCS2)Cd(S2POCH2C(CH3)2CH2O)]
(27)
144
RESULTS AND DISCUSSION
Figure 3.33: The 1H Spectrum of [(p-CH3C6H4OCS2))Hg(S2POCH2C(CH3)2CH2O)]
(32)
Figure 3.34: The 1H Spectrum of [(C6H5CH2OCS2)Hg(S2POCH2C(CH3)2CH2O)]
(33)
145
RESULTS AND DISCUSSION
Figure 3.35: The 31P Spectrum of [(o-CH3C6H4OCS2)Zn(S2POCH2C(CH3)2CH2O)]
(22)
Figure 3.36: The 31P Spectrum of [(m-CH3C6H4OCS2)Cd(S2POCH2C(CH3)2CH2O)]
(27)
146
RESULTS AND DISCUSSION
Figure 3.37: The 31P Spectrum of [(p-CH2C6H5OCS2)Hg(S2POCH2C(CH3)2CH2O)]
(32)
Figure 3.38: The 31P Spectrum of [(C6H5CH2OCS2)Hg(S2POCH2C(CH3)2CH2O)]
(33)
147
RESULTS AND DISCUSSION
Figure 3.39: The 13C Spectrum of [(o-CH3C6H4OCS2)Zn(S2POCH2C(CH3)2CH2O)]
(22)
Figure 3.40: The 13C Spectrum of [(m-CH3C6H4OCS2)Cd(S2POCH2C(CH3)2CH2O)]
(27)
148
RESULTS AND DISCUSSION
Figure 3.41: The 13C Spectrum of [(p-CH3C6H4OCS2)Hg(S2POCH2C(CH3)2CH2O)]
(32)
Figure 3.42: The 13C Spectrum of [(C6H5CH2OCS2)Hg(S2POCH2C(CH3)2CH2O)]
(33)
149
RESULTS AND DISCUSSION
Structural Features
Literature survey indicated that the dithio ligands generally act as bidentate moieties
to most metals and metalloids.169d, 173, 261-265 It would not be appropriate to predict a
precise structure for these complexes without single crystal X–ray analysis. Efforts
have been made to get suitable crystals for x-ray diffraction analysis but would not get
the crystals of quality required. However, in conjunction with the literature reports219220, 249-254, 265-269
NMR (1H,
13
and observations based on elemental analysis, TGA, mass, IR and
C and
31
P) studies, a probable structure can be assigned to these
complexes. The observation of bands arising from (CS2) and (PS2) vibrations is
entirely typical for bidentate chelating dithio units. Further, for bidentate
dithiocarbonate ligand presence of sharp peak without a shoulder favors this mode of
bonding. The shifting of bands for (C=S) towards the lower wave number is
supporting the complexation between the metal and dithio ligand. Also, the
occurrence of a singlet (77.32–86.01 ppm) for phosphorus nucleus with upfiled shift
of 5 – 14 ppm, which is different for each metal of zinc triad, confirms the bidentate
chelating nature of the dithiophosphate moiety. A singlet observed for the phosphorus
atom of the dithiophosphate moiety in the
of the dithiocarbonate moiety in the
13
31
PNMR spectra and carbon atom (OCS2)
C NMR spectra in all the complexes indicate
the formation of the mixed dithiocarbonato-dithiophosphato metal complexes. It is
further confirmed by the appearance of a new band for v(M−S) (371 – 280 cm–1). In
the mass spectra, the base peak indicates a strong chelating tendency of
dithiocarbonates as compared to the alkylene dithiophosphates, while the weak
molecular ion peak indicates pyrrolytic decomposition of the complex. Thermal
studies indicate the formation of metal sulfide as a final decomposition product.
Consequently, on the basis of above conclusions and in conjunction with the
literature reports 141, 173, 257-258, 279, an overall four folded coordination must be existing
around the zinc, cadmium and mercury atom leading to distorted tetrahedral geometry
due to bidentate mode of chelation by dithio ligands in which each metal atom is
surrounded by four sulfur atoms i.e. two sulfur from one dithiocarbonate and two
sulfur from one dithiophosphate moiety respectively, forming to MS4 configuration as
described in Figures 3.46 (a–b).
150
RESULTS AND DISCUSSION
H3C
S
S
O
C
O
P
M
CH3
C
O
S
S
CH2
CH3
CH2
Figure 3.46 (a): Proposed distorted tetrahedral geometry for
[(o-, m- and p-CH3C6H4OCS2)M(S2POCH2C(CH3)2CH2O)]; M = Zn (22-24), Cd
(26-28) and Hg (30-32)
S
C O C
H2
S
CH2
CH3
C
P
M
S
O
S
O
CH2
CH3
Figure 3.46 (b): Proposed distorted tetrahedral geometry for
[(C6H5CH2OCS2)M(S2POCH2C(CH3)2CH2O)]; M =Zn (25), Cd (29) and Hg (33)
151
RESULTS AND DISCUSSION
3.6: Adducts of bis-[(ortho–, meta– and para–tolyl)/benzyl
dithiocarbonates] of zinc(II), cadmium(II) and mercury(II) with
nitrogen and phosphorus donors (34-81)
This section describes the synthesis and characterization of new adducts of
bis(tolyl/benzyldithiocarbonates) of Zn(II), Cd(II) and Hg(II) having N─M─S and
P─M─S linkages. Metal chelates in which the metal ion is coordinately unsaturated
can act as an electron acceptor and yield adducts with neutral molecules being
electron donors. Metal xanthate complexes and their reaction products with a variety
of Lewis bases have been extensively studied.270-271 The soluble alkali metal xanthates
are widely used in extraction and separation of Hg, Cd etc.
272-273
Sodium and
potassium ethyl xanthate have antidotal effects in acute mercurial poisoning.
Transition metal xanthate complexes have been investigated for nonlinear optical
(NLO) applications.274 Cadmium xanthate was also demonstrated to have nonlinear
optical properties and generated a very strong 2nd harmonic signal. To the best of our
knowledge, the reaction products of group 12th xanthate with Lewis bases have been
much less extensively studied than other similar compounds.275 Additionally, adducts
and their formation reactions have also been found useful in a variety of ways such as
in biological and industrial applications. Metal compounds of dithiocarbonates serve
as highly efficient precursors for nano-metal sulfides and some materials synthesized
from metal dithiocarbonates are molecular rectifiers.276 Thus it is of interest to
investigate the interactions between metal dithiocarbonates with the nitrogen and
phosphorus bases. The adducts have been formed by occupying the vacant
coordinating sites of the metal in the complexes, [(o–, m– and p–CH3C6H4OCS2)2M]
and [(C6H5CH2OCS2)2M] (M = Zn, Cd and Hg) by the donor ligand pyridine,
triphenylphosphine 1,10–phenanthroline and 2,2’-bipyridyl.
Adducts of mononuclear tolyl/benzyl dithiocarbonates of Zn, Cd and Hg
with heterocyclic amines and phosphines corresponding to [(ArOCS2)2M.nL] (Ar =
o–, m– and p–CH3C6H4– and C6H5CH2–; M = Zn, Cd and Hg; n = 2 for L = Py or
PPh3 and n = 1 for L = 1,10–Phen or 2,2’-bipy) have been synthesized conveniently
by the addition reaction of donor ligand with the metal(II) dithiocarbonates in
dichloromethane/chloroform in the required stoichiometry under normal condition.
152
RESULTS AND DISCUSSION
The reactions with pyridine and triphenylphosphine were conducted in 1:2 molar ratio
while in 1:1 molar ratio reaction was executed in case of 1,10–phenanthroline and
2,2’-bipyridyl (Scheme 3.10).
[(ArOCS2)2Zn] + nL
(10-13)
[(ArOCS2)2Cd] + nL
(14-17)
[(ArOCS2)2Hg] + nL
(18-21)
CH2Cl2
stirring
~ 30 min.
CHCl3
stirring
~ 30 min.
CHCl3
stirring
~ 30 min.
[(ArOCS2)2Zn.nL]
(34-37, 46-49, 58-61, 70-73)
[(ArOCS2)2Cd.nL]
(38-41, 50-53, 62-65, 74-77)
[(ArOCS2)2Hg.nL]
(42-45, 54-57, 66-69, 78-81)
Scheme 3.10: Synthesis of [(ArOCS2)M.nL]; where M = Zn, Cd and Hg; Ar = o–,
m–, p–CH3C6H4– and C6H5CH2– and L = NC5H5, P(C6H5)3 (n = 2) or N2C12H8,
N2C10H8 (n = 1)]
These compounds (34-81) were isolated as white to yellow solids in 77-89 %
yield. These compounds are soluble in common organic solvents like toluene,
benzene, dichloromethane and chloroform and insoluble in n–hexane. All the mixed
ligand (adducts) complexes are stable in air, though were stored in calcium chloride
desiccators. These compounds are non–volatile even under the reduced pressure.
Mass spectral studies of these compounds were found in agreement with the
monomeric nature of these compounds. The elemental analyses, particularly C, H, N,
S, Zn, Cd and Hg were found consistent with the molecular formula of these
compounds. These compounds were further characterized by various spectral studies
viz. Mass, TGA, IR, 1H, 31P and 13C NMR. The results of the elemental analyses were
in good agreement with those required by the proposed formulae.
153
RESULTS AND DISCUSSION
Infrared
The relevant assignments of the IR bands were made on the basis of comparisons with
the spectra of bis(o–, m– and p–tolyl)/benzyldithiocarbonate metal(II) and the
analogous adduts of the metal complexes. The comparison of IR data of the
complexes and donor stabilised complexes with starting materials has shown some
significant and characteristic changes like shifting of bands i.e. M–S vibrations are
shift towards higher frequency, a small shift to lower frequency of C–S vibrations and
surprisingly comparatively large shift to lower frequency of the C–O–C vibrations.
All these changes resulted because of change of coordination number from four to
six277, 280 and due to decrease in electron flow in consonance with increase in electron
charge donated by donor ligands like pyridine, triphenylphosphine, 1,10phenanthroline and 2,2’-bipyridyl. The IR spectra of these compounds showed all the
bands observed in the parent metal(II)-bis(dithiocarbonate) moiety (10-21) and bands
characteristic of the donor ligands like pyridine (34-45), triphenylphosphine (46-57),
1,10–phenanthroline (58-69) and 2,2’-bipyridyl (70-81). Infra red spectrum of free
pyridine, 1,10-phenanthroline and 2,2’-bipyridyl have shown bands at 1620–1510,
1595–1500 cm-1and at 1615–1502 cm-1 due to interactions between v(C
v(C
C) and
N) symmetric ring stretching and inplane antisymmetric ring vibrations. These
bands are found to be separated about 100 cm-1 apart.249-250 The characteristic
v(C
C) aromatic stretching bands were observed in the range 1612–1570 cm-1 for
the complexes (34-81). The band for (C
N) in the range 1456–1447 cm–1 for
complexes (34-45), 1452–1440 cm-1 for complexes (58-69) and 1457–1441 cm-1 for
complexes (70-81) due to the coordinated donor ligands like pyridine, 1,10–
phenanthroline and 2,2’-bipyridyl, depict a shift toward lower frequencies. Similar is
the case observed for triphenylphosphine moiety where assignment of strong band
due to (P–C) stretching vibrations in the region 1435–1415 cm–1 in the derivatives
(46-57) thus indicates the presence of triphenylphosphine as the coordinated ligand.
These observations and kinds of negative shifts are suggestive of binding of donor
ligands like pyridine, phenanthroline, bipyridyl and triphenylphosphine to the central
metal ion. This shift occurs due to maintenance of a ring current arising out of π–
electron delocalization in the chelate formation i.e. upon coordination. This confirms
154
RESULTS AND DISCUSSION
the involvement of nitrogen and phosphorous atom of donor ligands in the metal
centre.249-251 The presence of direct bond of donor ligands to metal via the nitrogen
atom in complexes (34-45 and 58-81) and phosphorous atom in complexes (46-57)
can be supported by the existence of band at 754–740 cm-1 and 555–525 cm-1 which
may be assigned to ν(M−N) and ν(M−P) vibrations (M = Zn, Cd and Hg),
respectively220,
269
. The medium intensity bands in the range of 368–280 cm–1 are
typically assigned to the (M–S) vibrations (M = Zn, Cd and Hg) in all the
complexes. The strong intensity bands that were present in the region 1238–1220 cm–
were assigned to (C–O–C) stretching vibrations. Bands due to (C
1
S) in the
range 1044–1019 cm–1 without any shoulder confirms the bidentate chelation of
dithiocarbonate ligands with the zinc, cadmium and mercury atoms in complexes (3481). The ν(CS2) stretching vibrations appeared at 1145–1140 cm−1 and 1008–1002
cm−1 in the parent dithiocarbonate ligand is replaced by a strong intensity band which
remains unsplited in all the cases. This shifting and arising of single sharp band due to
ν(CS2) vibrations in the complexes are quite diagnostic to propose isobidentate mode
of bonding of the dithio moiety with zinc, cadmium and mercury, as the appearance of
only one band without any splitting in the same region is attributed to the bidentate
mode of binding of the dithiocarbonate ligand.219 The C–H vibrations (due to tolyl
and benzyl ring) were observed in their characteristic region. The relevant IR spectral
data of the compounds (34-81) are given in the Table 3.17. The IR spectrum of some
of the representative complexes (34, 39, 44, 50, 56, 63, 60 and 75) are given in
Figure 3.47, 3.48, 3.49, 3.50, 3.51, 3.52, 3.53 and 3.54.
1
1
H NMR
H NMR spectra (in CDCl3) of these complexes (34-81) have shown the chemical
shifts for the protons of the –CH3 and –CH2 attached to the tolyl and benzyl ring in
the region 2.20–2.36 ppm and 4.28–4.47 ppm as singlet, respectively. The chemical
shifts for the tolyl and benzyl ring protons in these complexes were observed in the
region 6.52–7.14 and 7.09–7.34 ppm, respectively with their usual splitting pattern.
There were two resonances for the ring protons of para complexes (36, 40, 44, 48, 52,
155
RESULTS AND DISCUSSION
56, 60, 64, 68, 72, 76 and 80) in the region 6.60–7.13 ppm, whereas four resonances
were observed for ortho complexes (34, 38, 42, 46, 50, 54, 58, 62, 66, 70, 74 and 78)
in the region 6.70–7.10 ppm and for the meta complexes (35, 39, 43, 47, 51, 55, 59,
63, 67, 71, 75 and 79) in the region 6.52–7.14 ppm, respectively. The aryl protons of
the free heteroaromatic nitrogen and phosphorous donor bases viz. pyridine,
triphenylphosphine, 1,10–phenanthroline and 2,2’-bipyridyl exhibited signals with
different multiplicities because of the aromatic methyne –CH= protons. For pyridine,
three signals were observed at 8.59, 7.38 and 7.75 ppm as doublet, triplet and triplet
for proton at position (2’,6’), (3’,5’)
and (4’), respectivelly and for
triphenylphosphine moiety multiplet was observed in the region 7.19-7.34 ppm for
protons (2’– 6’) of the aromatic ring. Similar, case was observed for 1,10phenanthroline and 2,2’-bipyridyl moieties. Where four signals were observed for
1,10-phenanthroline at 8.81 ppm (2’, 9’ proton, doublet), 7.26 ppm (3’,8’ proton,
triplet), 8.00 ppm (4’,7’ proton, doublet) and 7.52 ppm (5’,6’ proton, triplet). For 2,2’bipyridyl these signals were indicative of 6,6’ proton as doublet at 8.59 ppm, 3,3’
proton as doublet at 8.14 ppm, 4,4’ proton as triplet at 7.66 ppm and 5,5’ proton as
triplet at 7.12 ppm.
2'
2'
3'
N
4'
6'
5'
Pyridine
2'
3'
P
5'
N
9'
3'
4'
6'
N
triphenylphosphine
6'
8'
5'
7'
4'
3
N
5'
6'
1,10-phenanthroline
3'
4'
2
2,2'-bipyridyl
The mixed ligand complexes of zinc, cadmium and mercury of present
investigation show very little downfield shift of signals due to the diamagnetic
character of these metal ions. The protons 2’ and 6’ of pyridine and
triphenylphosphine, 2’ and 9’ of 1,10-phenanthroline and 6 and 6’ of 2,2’-bipyridyl
exhibit maximum shift (0.30–0.41ppm) to lower field due to deshielding and hence
gave their characteristic chemical shift in the range 7.09–8.99 ppm, 7.20–7.64 ppm,
7.25–9.20 and 7.09–9.00 ppm. This
deshielding of protons thus indicates the
coordination of the base to the metal centre which is similar to the shift found in the
analogous adducts.269, 281 The 1H NMR spectral data of these complexes (34-81) have
156
RESULTS AND DISCUSSION
been summarized in Table 3.18. The 1H NMR spectra of few of the representative
complexes (44, 50, 60 and 75) are given in Figure 3.55, 3.56, 3.57 and 3.58.
31
P NMR
The
31
P NMR spectra of the complexes (46-57) were recorded in CDCl3. The
appearance of a singlet was observed for each complex may be considered as an
authentication of the formation of the compounds. A phosphorus signal in the range –
3.70 to –5.11 ppm was observed in the complexes for the triphenylphosphine i.e.
deshielded with respect to uncoordinated triphenylphosphine moiety (–5.71 ppm).
This shift is in good agreement with the shift found in the complexes of thorium and
platinum with triphenylphosphine in the region –2.21 to –3.92 ppm.76, 269, 282-284 The
31
P NMR spectral data of these complexes (46-57) have been summarized in Table
3.18. The 31P NMR spectrum of few of the representative complexes (46, 51 and 57)
are given in Figure 3.59, 3.60 and 3.61.
13
C NMR
The
13
C NMR studies in non–coordinated solvent make it possible to assign the
magnetically non–equivalent carbon atoms. The position of –CS2 carbon moved to a
higher field (2-3 ppm) as compared to the parent metal-dithiocarbonate (10-21)
moiety and was at 170.23–188.23 ppm, indicating the participation of the donor
groups in coordination with the metal. The signal of the substituent on the phenyl ring
of the ligand is absorbed at the value that is expected, according to the nature of the
substituent. The chemical shift for methyl carbon (–CH3) attached to the tolyl ring
was observed in the region 19.28–21.62 ppm in the complexes (34-36, 38-40, 42-44,
46-48, 50-52, 54-56, 58-60, 62-64, 66-68, 70-72, 74-76 and 78-80) while the chemical
shift for methylene (–CH2) carbon of the benzyl moiety was observed in the region
68.52–72.21 ppm in the complexes (37, 41, 45, 49, 53, 61, 65, 73, 77 and 81). The
carbon nuclei of the phenyl groups (−C6H4 and −C6H5) have displayed their
resonances in the region 112.10–152.94 ppm. The 13C NMR spectra of the complexes
(34-81) have also exhibited the chemical shifts of the carbon nuclei of the donor
157
RESULTS AND DISCUSSION
moieties. There were three resonances for the aryl carbon nuclei of the pyridine in the
region 124.12–149.89 ppm, four for the triphenylphosphine in the region 124.70–
141.88 ppm, four for 2,2’-bipyridyl in the region 120.01–149.68 ppm and six for
1,10-phenanthroline moiety in the region 124.04–149.63 ppm, respectively. The
13
C
NMR spectral data of these complexes have been summarized in Table 3.19. The 13C
NMR spectra of few of the representative complexes 44, 50, 60 and 75 are given in
Figure 3.62, 3.63, 3.64 and 3.65.
Mass
The mass spectra of the zinc, cadmium and mercury mixed-ligand complexes with
pyridine, triphenylphosphine, 2,2’-bipyridyl and 1,10-phenanthroline shows weak
molecular ion peak in all the cases centered at m/z 590, 665, 883, 946, 1009, 1097,
612, 661, 749, 588, 635 and 723 which is surrounded by isotopic envelop of their
representative metal, in complexes (36, 38, 42, 46, 51, 55, 61, 64, 68, 75, 77 and 81).
The peaks at m/z 431, 478 and 567 in complexes (36, 46, 61, 75), (38, 51, 64, 77) and
(42, 55, 68, 81) formed by the loss of the donor ligands from complexes. Peaks
corresponding to higher m/z values can be regarded as direct fragmentation of the
molecular ion, while peaks corresponding to lower m/z values can be considered as
daughter fragments. The mass spectra studies follow a similar fragmentation pattern
as in the case of complexes reported earlier in case of complexes (10-22). The mass
fragmentation pattern of one of the complex [(o-CH3C6H4OCS2)2Hg.2Py] (42) gave
m/z at 568 (12) due to [(o-CH3C6H4OCS2)2Hg], in addition to a signal for molecular
ion peak at m/z 883 (17). A signal at m/z 384 (19) for [(o-CH3C6H4OCS2)Hg], a
strong intensity peak corresponding to ArO at m/z at 107 (100) and another strong
intensity peak at m/z 76 (50) due to [CS2] is formed by loss of one ligand, metal and
cresyl group from the species. The occurrence of molecular ion peak in the complexes
is supporting the monomeric nature of the complexes. The complexes show extensive
fragmentation and only the most abundant fragment ions along with their m/z (percent
abundance) values are given in Table 3.20. The systematic mass fragmentation
pattern of the complex 42 is given in Scheme 3.11. The mass spectrum of the
representative complex (42) is given in Figure 3.66.
158
RESULTS AND DISCUSSION
(ArOCS2)2Hg.2Py
(ArOCS2)2Hg
+
[M+] 568 (12)
[M ] 883 (17)
Py
(ArOCS2)Hg
+
[M ] 79 (20)
ArCOS+
[M ] 151 (15)
+
+
(ArOCS2)
[M+] 183 (17)
[M+] 384 (19)
HgS
+
ArO
[M ] 232 (30)
+
[M ] 107 (100)
+
CS2
+
[M ] 76 (50)
Scheme 3.11: Mass fragmentation pattern of [(ArOCS2)2Hg.2Py] where Ar = o-CH3C6H4
and Py =NC5H5 (42) brackets = m/z; parenthesis = intensities in %.
Figure 3.66: The mass spectrum of complex HgL2.2Py (42); where L = o-CH3C6H4OCS2
and Py = NC5H5
159
RESULTS AND DISCUSSION
Thermogravimetrical Analysis
The thermal behavior of adducts was studied under inert atmosphere in the range of
25–1000 C which displays weight losses in three steps with different time intervals
and at different temperatures. In the thermogravimetric analysis of [(pCH3C6H4OCS2)2Zn.2NC5H5] (36), an initial weight loss was 26.8% calc. (26.4%
obs.) occurred at 206.5 °C which corresponds to [(p-CH3C6H4OCS2)2Zn] as a result
of loss of pyridine. Another fragment was formed due to the loss of different groups
as [(C6H4OCS2)2Zn], weight loss 31.9% calc. (32.0% obs.) at 276.5 °C and
[(OCS2)2Zn], weight loss 57.7% calc. (58.1% obs.) at 486.5 °C. The TGA curve
shows the maximum weight loss 83.5% calc. (83.6% obs.) at 571.6 °C leading to the
formation of stable metal sulfide (Figure 3.67).
The
thermogravimetric
CH3C6H4OCS2)2Hg.2P(C6H5)3]
analysis
of
the
complex
[(p-
(56), displayed a thermolysis step that covers a
temperature range from 25 to 1000 C. The thermogram (Figure 3.68) exhibited the
decline curve characteristic for dithiocarbonate complexes. The diagnostic weight loss
of initial weight occurs in the steeply descending segment of the TGA curve. This
weight loss i.e., 48.5 % at 406 C is due to the formation of the dithiocarbonate
corresponding to [(p-CH3C6H4OCS2)2Hg], (the calculated weight loss is 48.4 %). The
intermediate product [(OCS2)2Hg] formed at 771 C due to 73.9 % (obs.) weight loss,
which agrees with thermogravimetric data for dithiocarbonate. The weight loss
leading to the formation of the final residue is 79.9 % corresponds to HgS;
contaminated with other thermolysis products (the calculated weight loss is 80.1%) at
822 C.
The TG curve reflects a multistage process caused by thermolysis of
cadmium(II) adduct (65). The first stage in the TG curve shows (Figure 3.69) the
most intense weight loss in the range of 100-270 °С, the weight loss (27.6 % obs.,
27.3 % calc.) leads to thermolysis of compound and approximately corresponds to the
removal of phenanthroline group (the calculated mass loss is 27.6 %) and lead to the
formation of parent compound [(C6H5CH2OCS2)2Cd]. The 55.2 % (calc.), 55.4 %
(obs.) weight loss attests the formation of major fragment [(OCS2)2Cd] at 840 °С.
This is confirmed by steep curve after 750 °С. The weight loss continued upto 980 °C
160
RESULTS AND DISCUSSION
with the formation of the final residue with a therotical weight loss 78.2 % (79.3 %
obs.) at 966 °C corresponding to CdS as the end product of thermolysis products.
Similarly, the complex, [(C6H5CH2OCS2)2Zn.N2C10H8] (77) displayed a
thermolysis step that covers a temperature range from 25 to 1000 °C. The thermogram
(Figure 3.70) exhibited the decline curve characteristic for dithiocarbonate
complexes. The diagnostic weight loss of initial weight occurs in the steeply
descending segment of the TGA curve. The weight loss i.e. 26.4% (obs.), 25.1%
(calc.) at 206.5 C is due to the formation of the dithiocarbonate corresponding to
[(C6H4CH2OCS2)2Zn], weight loss 26.6% (calc.) as an intermediate product, which
agrees with thermogravimetric data for dithiocarbonates. Another important weight
loss 56.8% (obs.) occur at 481.5 °C temperature corresponding to the formation of
[(OCS2)2Zn] 57.3% (calc.). The decomposition continues to about 580 °C at which
most of the organic part of the compound has been lost. This sharp decomposition
period brings about 80-83% weight loss in the zinc complex and led to the complete
formation of ZnS. Hence in all cases the final products are the metal sulfides.
Thus, the thermogravimetric analysis depicts the formation of metal sulfide as
the final stable thermal decomposition product at different temperature ranges for
complexes and adducts. On comparision basis this study reveals that tetrahedral
complexes are less stable under thermal conditions compared to their octahedral
addition complexes having different nitrogen and phosphorus donor ligands, which
mean the formation of metal sulfide (i.e. the thermal decomposition product of
complexes) takes places at lower temperature (less stable towards thermal
dccomposition) in four coordinated complexes than their addition complexes (more
stable towards thermal decomposition).
161
RESULTS AND DISCUSSION
Figure 3.67: TGA curve for [(p-CH3C6H4OCS2)2Zn.2NC5H5] (36)
Figure 3.68: TGA curve for [(p-CH3C6H4OCS2)2Hg.2P(C6H5)3] (56)
162
RESULTS AND DISCUSSION
Figure 3.69: TGA curve for [(C6H5CH2OCS2)2Cd.N2C12H8] (65)
Figure 3.70: TGA curve for [(C6H5CH2OCS2)2Zn.N2C10H8] (77)
163
RESULTS AND DISCUSSION
Scanning Electron Microscopy (SEM)
Typical SEM image of complex reveals morphology and particle size that it consists
of large quantities of rod-shaped structures with dimensions in the range of a
micrometer and has been carried out at a low and high magnification for complex (40)
Figure 3.71 (a-b). The information revealed from the signals included external
morphology, topography, structure, and orientation of materials making up the
sample. The images show the uneven rod like shape of particles with rough texture
and layered. The particles are present in the form of clusters. In general, the SEM
photograph shows single phase formation with well-defined shape. Complex has a
different topography and morphology at the two different magnifications. SEM
studies show microstructures of the complexes, which mainly include surface
morphology.
(a)
(b)
Figure 3.71: SEM image of [(m-CH3C6H4OCS2)2Hg.N2C10H8] (79)
complex (a) low magnification; (b) high magnification
164
Table 3.17: IR spectral data of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonates of zinc(II), cadmium(II) and mercury(II)
with nitrogen and phosphorus donor ligands (34-81) (in cm–1)
S.No.
Complex
v(C–O–C)
34.
[(o-CH3C6H4OCS2)2Zn.2NC5H5]
35.
v(C
S)
v(C–C)
v(M–S)
1230, s
1038, s
1575, b
362, m
[(m-CH3C6H4OCS2)2Zn.2NC5H5]
1230, s
1038, s
1576, b
36.
[(p-CH3C6H4OCS2)2Zn.2NC5H5]
1228, s
1035, s
37.
[(C6H5CH2OCS2)2Zn.2NC5H5]
1226, s
38.
[(o-CH3C6H4OCS2)2Cd.2NC5H5]
39.
v(N–C)
v(M–N)
v(M–P)
1454, s
-
754, m
--
362, m
1451, s
-
754, m
--
1575, b
356, m
1456, s
-
752, m
--
1032, s
1570, b
350, m
1448, s
-
740, m
--
1234, s
1030, s
1592, b
353, m
1447, s
-
750, m
--
[(m-CH3C6H4OCS2)2Cd.2NC5H5]
1232, s
1036, s
1591, b
348, m
1450, s
-
749, m
--
40.
[(p-CH3C6H4OCS2)2Cd.2NC5H5]
1234, s
1033, s
1596, b
352, m
1451, s
-
752, m
--
41.
[(C6H5CH2OCS2)2Cd.2NC5H5]
1230, s
1020, s
1591, b
343, m
1450, s
-
747, m
--
42.
[(o-CH3C6H4OCS2)2Hg.2NC5H5]
1230, s
1042, s
1610, b
290, m
1452, s
-
751, m
--
43.
[(m-CH3C6H4OCS2)2Hg.2NC5H5]
1235, s
1040, s
1602, b
286, m
1451, s
-
756, m
--
44.
[(p-CH3C6H4OCS2)2Hg. 2NC5H5]
1236, s
1041, s
1611, b
292, m
1450, s
-
753, m
--
45.
[(C6H5CH2OCS2)2Hg.2NC5H5]
1229, s
1043, s
1603, b
290, m
1449, s
-
747, m
--
46.
[(o-CH3C6H4OCS2)2Zn.2P(C6H5)3]
1231, s
1039, s
1575, b
359, m
-
1415, s
--
535, m
47.
[(m-CH3C6H4OCS2)2Zn.2P(C6H5)3]
1230, s
1039, s
1575, b
355, m
-
1421, s
--
536, m
48.
[(p-CH3C6H4OCS2)2Zn.2P(C6H5)3]
1230, s
1035, s
1575, b
359, m
-
1431, s
--
535, m
165
RESULTS AND DISCUSSION
v(P–C)
[(C6H5CH2OCS2)2Zn.2P(C6H5)3]
1223, s
1036, s
1570, b
360, m
-
1425, s
--
539, m
50.
[(o-CH3C6H4OCS2)2Cd.2P(C6H5)3]
1230, s
1023, s
1591, b
350, m
-
1415, s
--
555, m
51.
[(m-CH3C6H4OCS2)2Cd.2P(C6H5)3]
1231, s
1030, s
1592, b
347, m
-
1432, s
--
536, m
52.
[(p-CH3C6H4OCS2)2Cd.2P(C6H5)3]
1239, s
1030, s
1595, b
349, m
-
1431, s
--
525, m
53.
[(C6H5CH2OCS2)2Cd.2P(C6H5)3]
1230, s
1019, s
1593, b
335, m
-
1423, s
--
539, m
54.
[(o-CH3C6H4OCS2)2Hg.2P(C6H5)3]
1238, s
1040, s
1610, b
286, m
-
1432, s
--
525, m
55.
[(m-CH3C6H4OCS2)2Hg.2P(C6H5)3]
1232, s
1043, s
1608, b
280, m
-
1428, s
--
528, m
56.
[(p-CH3C6H4OCS2)2Hg.2P(C6H5)3]
1230, s
1044 s
1611, b
284, m
-
1435, s
--
529, m
57.
[(C6H5CH2OCS2)2Hg.2P(C6H5)3]
1235, s
1040 s
1607, b
282, m
-
1428, s
--
528, m
58.
[(o-CH3C6H4OCS2)2Zn.N2C12H8]
1227, s
1036, s
1572, b
358, m
1452, s
-
753, m
--
59.
[(m-CH3C6H4OCS2)2Zn.N2C12H8]
1227, s
1036, s
1571, b
358, m
1451, s
-
752, m
--
60.
[(p-CH3C6H4OCS2)2Zn.N2C12H8]
1233, s
1040, s
1574, b
352, m
1449, s
-
750, m
--
61.
[(C6H5CH2OCS2)2Zn.N2C12H8]
1230, s
1038, s
1572, b
359, m
1447, s
-
747, m
--
62.
[(o-CH3C6H4OCS2)2Cd.N2C12H8]
1236, s
1031, s
1593, b
350, m
1442, s
-
750, m
--
63.
[(m-CH3C6H4OCS2)2Cd.N2C12H8]
1233, s
1035, s
1597, b
345, m
1452, s
-
749, m
--
64.
[(p-CH3C6H4OCS2)2Cd.N2C12H8]
1236, s
1034, s
1592, b
350, m
1440, s
-
750, m
--
65.
[(C6H5CH2OCS2)2Cd.N2C12H8]
1238, s
1021, s
1594, b
340, m
1451, s
-
748, m
--
66.
[(o-CH3C6H4OCS2)2Hg.N2C12H8]
1230, s
1040, s
1610, b
292, m
1449, s
-
751, m
--
67.
[(m-CH3C6H4OCS2)2Hg.N2C12H8]
1220, s
1042, s
1607, b
282, m
1452, s
-
751, m
--
68.
[(p-CH3C6H4OCS2)2Hg.N2C12H8]
1230, s
1039, s
1611, b
287, m
1450, s
-
752, m
--
69.
[(C6H5CH2OCS2)2Hg.N2C12H8]
1231, s
1041, s
1603, b
283, m
1451, s
-
748, m
--
RESULTS AND DISCUSSION
166
49.
70.
[(o-CH3C6H4OCS2)2Zn.N2C10H8]
1230, s
1039, s
1573, b
356, m
1450, s
-
751, m
--
71.
[(m-CH3C6H4OCS2)2Zn.N2C10H8]
1220, s
1038, s
1579, b
360, m
1457, s
-
750, m
--
72.
[(p-CH3C6H4OCS2)2Zn.N2C10H8]
1220, s
1038, s
1579, b
360, m
1451, s
-
751, m
--
73.
[(C6H5CH2OCS2)2Zn.N2C10H8]
1230, s
1034, s
1572, b
359, m
1447, s
-
749, m
--
74.
[(o-CH3C6H4OCS2)2Cd.N2C10H8]
1231, s
1031, s
1593, b
352, m
1449, s
-
740, m
--
75.
[(m-CH3C6H4OCS2)2Cd.N2C10H8]
1229, s
1021, s
1591, b
340, m
1450, s
-
741, m
--
76.
[(p-CH3C6H4OCS2)2Cd.N2C10H8]
1230, s
1034, s
1595, b
349, m
1452, s
-
749, m
--
77.
[(C6H5CH2OCS2)2Cd.N2C10H8]
1232, s
1035, s
1594, b
350, m
1441, s
-
742, m
--
78.
[(o-CH3C6H4OCS2)2Hg.N2C10H8]
1229, s
1043, s
1610, b
292, m
1451, s
-
742, m
--
79.
[(m-CH3C6H4OCS2)2Hg.N2C10H8]
1228, s
1042, s
1608, b
280, m
1453, s
-
749, m
--
80.
[(p-CH3C6H4OCS2)2Hg.N2C10H8]
1225, s
1040, s
1612, b
284, m
1454, s
-
747, m
--
81.
[(C6H5CH2OCS2)2Hg.N2C10H8]
1220, s
1041, s
1604, b
286, m
1450, s
-
741, m
--
167
RESULTS AND DISCUSSION
Where, s = sharp, b = broad, m = medium, w = weak
Table 3.18: 1H and 31P NMR spectral data of of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonates of zinc(II), cadmium(II)
and mercury(II) with nitrogen and phosphorus donor ligands (34-81) in CDCl3 (in ppm)
Tolyl OR Benzylmoiety
#
S. No.
–CH3/–CH2
H3C
4
5
4'
O
3
2
1
5'
2'
CH2
3'
or
2'
Donor moiety
3'
N
31
P
4'
1'
6'
5'
2.27, s, 6H
7.01, d, 2H, [H(2)]; 6.83, t, 2H, [H(3)];
6.92, t, 2H, [H(4)]; 6.72, d, 2H, [H(5)]
7.09, d, 4H, [H(2’,6’)]; 7.38, t, 4H, [H(3’,5’)];
8.51, t, 2H, [H(4’)]
--
35.
2.30, s, 6H
6.80, s, 2H, [H(1)]; 6.62, d, 2H, [H(3)];
7.01, t, 2H, [H(4)]; 6.82, d, 2H, [H(5)]
7.54, d, 4H, [H(2’,6’)]; 8.00, t, 4H, [H(3’,5’)];
8.43, t, 2H, [H(4’)]
--
36.
2.22, s, 6H
6.73, d, 4H, [H(1,5)];
7.04, d, 4H, [H(2,4)]
7.54, d, 4H, [H(2’,6’)]; 8.02, t, 4H, [H(3’,5’)];
8.43, t, 2H, [H(4’)]
--
37.
4.29, s, 4H
7.27–7.32, m, 10H [H(1’–5’)]
7.34, d, 4H, [H(2’,6’)]; 8.30, t, 4H, [H(3’,5’)];
8.99, t, 2H, [H(4’)]
--
38.
2.24, s, 6H
7.00, d, 2H, [H(2)]; 6.80, t, 2H, [H(3)];
6.95, t, 2H, [H(4)]; 6.70, d, 2H, [H(5)]
7.18, d, 4H, [H(2’,6’)]; 7.94, t, 4H, [H(3’,5’)];
8.50, t, 2H, [H(4’)]
--
39.
2.27, s, 6H
6.74, s, 2H, [H(1)]; 6.60, d, 2H, [H(3)];
7.11, t, 2H, [H(4)]; 6.52, d, 2H, [H(5)]
7.44, d, 4H, [H(2’,6’)]; 8.00, t, 4H, [H(3’,5’)];
8.40, t, 2H, [H(4’)]
--
2.20, s, 6H
6.60, d, 4H, [H(1,5)];
7.00, d, 4H, [H(2,4)]
7.50, d, 4H, [H(2’,6’)]; 8.01, t, 4H, [H(3’,5’)];
8.43, t, 2H, [H(4’)]
--
40.
168
RESULTS AND DISCUSSION
34.
41.
4.31, s, 4H
7.20–7.30, m, 10H [H(1’–5’)]
7.30, d, 4H, [H(2’,6’)]; 8.20, t, 4H, [H(3’,5’)];
8.90, t, 2H, [H(4’)]
--
42.
2.27, s, 6H
7.01, d, 2H, [H(2)]; 6.83, t, 2H, [H(3)];
6.92, t, 2H, [H(4)]; 6.72, d, 2H, [H(5)]
7.40, d, 4H, [H(2’,6’)]; 8.01, t, 4H, [H(3’,5’)];
8.56, t, 2H, [H(4’)]
--
43.
2.30, s, 6H
6.80, s, 2H, [H(1)]; 6.62, d, 2H, [H(3)];
7.01, t, 2H, [H(4)]; 6.82, d, 2H, [H(5)]
7.44, d, 4H, [H(2’,6’)]; 8.20, t, 4H, [H(3’,5’)];
8.83, t, 2H, [H(4’)]
--
44.
2.22, s, 6H
6.73, d, 4H, [H(1,5)];
7.04, d, 4H, [H(2,4)]
7.55, d, 4H, [H(2’,6’)]; 7.82, t, 4H, [H(3’,5’)];
8.83, t, 2H, [H(4’)]
--
45.
4.29, s, 4H
7.27–7.32, m, 10H [H(1’–5’)]
7.34, d, 4H, [H(2’,6’)]; 8.34, t, 4H, [H(3’,5’)];
8.99, t, 2H, [H(4’)]
--
2'
3'
P
4'
6'
5'
3
2.21, s, 6H
7.09, d, 2H, [H(2)]; 6.86, t, 2H, [H(3)];
6.93, t, 2H, [H(4)]; 6.86, d, 2H, [H(5)]
7.24-7.63, m, 30H, [H(2’-6’)]
-5.05
47.
2.21, s, 6H
6.80, s, 2H, [H(1)]; 6.91, d, 2H, [H(3)];
7.09, t, 2H, [H(4)]; 6.81, d, 2H, [H(5)]
7.24-7.64, m, 30H, [H(2’-6’)]
-5.01
48.
2.12, s, 6H
6.78, d, 4H, [H(1,5)];
7.04, d, 4H, [H(2,4)]
7.20-7.64, m, 30H, [H(2’-6’)]
-4.99
49.
4.28, s, 4H
7.27–7.34, m, 10H [H(1’–5’)]
7.34-7.64, m, 30H, [H(2’-6’)]
-5.11
169
RESULTS AND DISCUSSION
46.
50.
2.28, s, 6H
7.06, d, 2H [H(2)]; 6.74, t, 2H [H(3)];
6.99, t, 2H [H(4)]; 6.78, d, 2H [H(5)]
7.20-7.38, m, 30H, [H(2’-6’)]
-4.61
51.
2.32, s, 6H
6.89, s, 2H [H(1)]; 6.97, d, 2H [H(3)];
7.14, t, 2H [H(4)]; 6.73, d, 2H [H(5)]
7.24-7.64, m, 30H, [H(2’-6’)]
-4.22
52.
2.18, s, 6H
6.78, d, 4H [H(1,5)];
7.13, d, 4H [H(2,4)]
7.21-7.64, m, 30H, [H(2’-6’)]
-3.91
53.
4.47, s, 4H
7.12–7.23, m, 10H [H(1’–5’)]
7.38-7.64, m, 30H, [H(2’-6’)]
-3.80
54.
2.26, s, 6H
7.10, d, 2H [H(2)]; 6.73, t, 2H [H(3)];
6.95, t, 2H [H(4)]; 6.76, d, 2H [H(5)]
7.20-7.30, m, 30H, [H(2’-6’)]
-4.20
55.
2.32, s, 6H
6.74, s, 2H [H(1)]; 6.84, d, 2H [H(3)];
7.09, t, 2H [H(4)]; 6.77, d, 2H [H(5)]
7.24-7.34, m, 30H, [H(2’-6’)]
-4.31
56.
2.36, s, 6H
6.75, d, 4H [H(1,5)];
7.03, d, 4H [H(2,4)]
7.21-7.34, m, 30H, [H(2’-6’)]
57.
4.34, s, 4H
7.09–7.25, m, 10H [H(1’–5’)]
7.38-7.44, m, 30H, [H(2’-6’)]
N
N
9'
3'
8'
7'
4'
5'
58.
2.10, s, 6H
7.00, d, 2H, [H(2)]; 6.77, t, 2H, [H(3)];
7.00, t, 2H, [H(4)]; 6.98, d, 2H, [H(5)]
-3.70
6'
7.25, d, 2H, [H(2’,9’)]; 7.55, t, 2H, [H(3’,8’)];
7.99, d, 2H, [H(4’,7’)]; 8.90, d, 2H, [H(5’,6’)]
--
170
RESULTS AND DISCUSSION
2'
-3.91
59.
60.
61.
2.30, s, 6H
2.22, s, 6H
6.80, s, 2H, [H(1)]; 6.90, d, 2H, [H(3)];
7.01, t, 2H, [H(4)]; 6.82, d, 2H, [H(5)]
6.75, d, 4H, [H(1,5)];
7.03, d, 4H, [H(2,4)]
7.25, d, 2H, [H(2’,9’)]; 7.56, t, 2H, [H(3’,8’)];
8.01, d, 2H, [H(4’,7’)]; 8.90, d, 2H, [H(5’,6’)]
7.25, d, 2H, [H(2’,9’)]; 7.55, t, 2H, [H(3’,8’)];
7.99, d, 2H, [H(4’,7’)]; 8.90, d, 2H, [H(5’,6’)]
--
--
4.29, s, 4H
7.27–7.32, m, 10H [H(1’–5’)]
7.34, d, 2H, [H(2’,9’)]; 7.56, t, 2H, [H(3’,8’)];
8.50, d, 2H, [H(4’,7’)]; 8.99, d, 2H, [H(5’,6’)]
2.24, s, 6H
7.00, d, 2H, [H(2)]; 6.80, t, 2H, [H(3)];
6.95, t, 2H, [H(4)]; 6.70, d, 2H, [H(5)]
7.41, d, 2H, [H(2’,9’)]; 7.84, t, 2H, [H(3’,8’)];
8.63, d, 2H, [H(4’,7’)]; 9.20, d, 2H, [H(5’,6’)]
6.74, s, 2H, [H(1)]; 6.90, d, 2H, [H(3)];
7.01, t, 2H, [H(4)]; 6.52, d, 2H, [H(5)]
7.65, d, 2H, [H(2’,9’)]; 7.85, t, 2H, [H(3’,8’)];
8.01, d, 2H, [H(4’,7’)]; 8.97, d, 2H, [H(5’,6’)]
--
2.27, s, 6H
6.60, d, 4H, [H(1,5)];
7.00, d, 4H, [H(2,4)]
7.52, d, 2H, [H(2’,9’)];7.93, t, 2H, [H(3’,8’)];
8.43, d, 2H, [H(4’,7’)]; 9.10, d, 2H, [H(5’,6’)]
--
2.20, s, 6H
7.20–7.30, m, 10H [H(1’–5’)]
7.54, d, 2H, [H(2’,9’)]; 7.92, t, 2H, [H(3’,8’)];
8.50, d, 2H, [H(4’,7’)]; 8.99, d, 2H, [H(5’,6’)]
-62.
64.
65.
-4.31, s, 4H
171
RESULTS AND DISCUSSION
63.
-66.
67.
68.
69.
2.27, s, 6H
7.01, d, 2H, [H(2)]; 6.83, t, 2H, [H(3)];
6.92, t, 2H, [H(4)]; 6.72, d, 2H, [H(5)]
7.40, d, 2H, [H(2’,9’)]; 7.52, t, 2H, [H(3’,8’)];
8.46, d, 2H, [H(4’,7’)]; 9.00, d, 2H, [H(5’,6’)]
7.61, d, 2H, [H(2’,9’)]; 7.85, t, 2H, [H(3’,8’)];
8.32, d, 2H, [H(4’,7’)]; 8.90, d, 2H, [H(5’,6’)]
--
2.30, s, 6H
6.80, s, 2H, [H(1)]; 6.62, d, 2H, [H(3)];
7.01, t, 2H, [H(4)]; 6.82, d, 2H, [H(5)]
6.73, d, 4H, [H(1,5)];
7.04, d, 4H, [H(2,4)]
7.50, d, 2H, [H(2’,9’)]; 7.82, t, 2H, [H(3’,8’)];
8.52, d, 2H, [H(4’,7’)]; 9.13, d, 2H, [H(5’,6’)]
--
2.22, s, 6H
7.27–7.32, m, 10H [H(1’–5’)]
7.50, d, 2H, [H(2’,9’)]; 7.83, t, 2H, [H(3’,8’)];
8.54, d, 2H, [H(4’,7’)]; 9.00, d, 2H, [H(5’,6’)]
4.29, s, 4H
N
--
6'
3'
4'
2
-70.
71.
2.27, s, 6H
7.01, d, 2H, [H(2)]; 6.83, t, 2H, [H(3)];
6.92, t, 2H, [H(4)]; 6.72, d, 2H, [H(5)]
7.09, d, 2H, [H(6’,6’)]; 7.64, t, 2H, [H(5’,5’)];
8.01, t, 2H, [H(4’,4’)]; 8.53, d, 2H, [H(3’,3’)]
2.21, s, 6H
6.81, s, 2H, [H(1)]; 6.91, d, 2H, [H(3)];
7.09, t, 2H, [H(4)]; 6.82, d, 2H, [H(5)]
7.09, d, 2H, [H(6’,6’)]; 7.64, t, 2H, [H(5’,5’)];
8.01, t, 2H, [H(4’,4’)]; 8.53, d, 2H, [H(3’,3’)]
--
172
RESULTS AND DISCUSSION
5'
72.
73.
74.
75.
76.
78.
79.
7.12, d, 2H, [H(6’,6’)]; 7.66, t, 2H, [H(5’,5’)];
8.36, t, 2H, [H(4’,4’)]; 8.59, d, 2H, [H(3’,3’)]
--
--
7.27–7.32, m, 10H [H(1’–5’)]
7.12, d, 2H, [H(6’,6’)]; 7.60, t, 2H, [H(5’,5’)];
8.01, t, 2H, [H(4’,4’)]; 8.49, d, 2H, [H(3’,3’)]
2.24, s, 6H
7.00, d, 2H, [H(2)]; 6.80, t, 2H, [H(3)];
6.95, t, 2H, [H(4)]; 6.70, d, 2H, [H(5)]
7.19, d, 2H, [H(6’,6’)]; 7.50, t, 2H, [H(5’,5’)];
8.20, t, 2H, [H(4’,4’)]; 8.50, d, 2H, [H(3’,3’)]
2.27, s, 6H
6.74, s, 2H, [H(1)]; 6.60, d, 2H, [H(3)];
7.11, t, 2H, [H(4)]; 6.52, d, 2H, [H(5)]
7.20, d, 2H, [H(6’,6’)]; 7.56, t, 2H, [H(5’,5’)];
8.50, t, 2H, [H(4’,4’)]; 8.59, d, 2H, [H(3’,3’)]
2.20, s, 6H
6.60, d, 4H, [H(1,5)];
7.00, d, 4H, [H(2,4)]
7.14, d, 2H, [H(6’,6’)]; 7.46, t, 2H, [H(5’,5’)];
8.32, t, 2H, [H(4’,4’)]; 8.57, d, 2H, [H(3’,3’)]
4.29, s, 4H
4.31, s, 4H
7.20–7.30, m, 10H [H(1’–5’)]
7.36, d, 2H, [H(6’,6’)]; 7.63, t, 2H, [H(5’,5’)];
8.21, t, 2H, [H(4’,4’)]; 8.48, d, 2H, [H(3’,3’)]
--
--
--
--
7.01, d, 2H, [H(2)]; 6.83, t, 2H, [H(3)];
6.92, t, 2H, [H(4)]; 6.72, d, 2H, [H(5)]
7.19, d, 2H, [H(6’,6’)]; 7.24, t, 2H, [H(5’,5’)];
8.01, t, 2H, [H(4’,4’)]; 8.50, d, 2H, [H(3’,3’)]
--
2.27, s, 6H
6.80, s, 2H, [H(1)]; 6.62, d, 2H, [H(3)];
7.01, t, 2H, [H(4)]; 6.82, d, 2H, [H(5)]
7.12, d, 2H, [H(6’,6’)]; 7.32, t, 2H, [H(5’,5’)];
8.42, t, 2H, [H(4’,4’)]; 8.60, d, 2H, [H(3’,3’)]
--
2.30, s, 6H
173
RESULTS AND DISCUSSION
77.
6.74, d, 4H, [H(1,5)];
7.03, d, 4H, [H(2,4)]
2.14, s, 6H
80.
81.
2.22, s, 6H
4.29, s, 4H
6.73, d, 4H, [H(1,5)];
7.04, d, 4H, [H(2,4)]
7.10, d, 2H, [H(6’,6’)]; 7.42, t, 2H, [H(5’,5’)];
8.38, t, 2H, [H(4’,4’)]; 8.57, d, 2H, [H(3’,3’)]
7.27–7.32, m, 10H [H(1’–5’)]
7.17, d, 2H, [H(6’,6’)]; 7.48, t, 2H, [H(5’,5’)];
8.20, t, 2H, [H(4’,4’)]; 8.48, d, 2H, [H(3’,3’)]
--
--
Where, s = singlet, d = doublet, m = multiplet, t = triplet;
#
S. No. of the complexes is according to Table No. 3.17.
RESULTS AND DISCUSSION
174
Table 3.19:
13
C NMR spectral data of of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonates of zinc(II), cadmium(II) and
mercury(II) with nitrogen and phosphorus donor ligands (34-81) in CDCl3 (in ppm)
#
CHn
(n=2 or 3)
C(CHn)
(n=2 or 3)
–C–O
34.
19.28
125.70
152.94
113.02
130.75, 130.78
124.70
172.94
124.23, 131.88, 149.63
35.
20.05
134.61
150.81
112.20, 115.04
120.61
131.88
171.63
124.23, 131.86, 149.36
36.
20.05
129.47
150.61
114.20
124.70
––
174.63
129.47, 136.82, 149.63
37.
71.41
135.99
––
126.71
127.01
128.69
184.62
129.88, 136.57, 149.64
38.
20.81
121.90
150.41
121.51
125.61, 126.81
122.22
174.29
125.20, 131.80, 148.60
39.
20.32
123.02
150.10
119.91, 126.31
130.30
123.32
171.96
124.20, 131.06, 149.38
40.
19.52
130.12
150.61
120.81
128.30
––
171.87
129.45, 136.02, 149.89
41.
69.98
142.81
––
125.31
130.41
126.21
187.62
129.81, 136.27, 149.05
42.
20.72
122.91
152.82
119.71
125.72, 128.71
120.22
170.87
124.12, 131.13, 148.63
43.
21.62
126.81
150.81
119.41, 121.82
124.62
120.41
170.23
124.20, 131.36, 143.36
44.
20.95
129.47
150.81
114.70
124.70
––
170.63
129.88, 136.87, 149.63
45.
69.52
141.02
––
125.91
131.01
126.81
188.23
129.81, 136.07, 149.04
S.No
Tolyl/Benzyl moiety
Cortho
Cmeta
(O)–C–S
Cpara
Donor moiety
Py
RESULTS AND DISCUSSION
175
PPh3
20.05
124.80
152.02
114.20
129.47, 129.83
120.21
172.49
125.38,127.01,136.64,
141.68
47.
20.04
133.44
150.81
112.20, 115.84
131.80
120.61
171.81
125.12, 127.01, 136.64,
141.68
48.
20.00
129.64
150.81
115.84
130.81
-
175.02
126.21, 127.01, 136.64,
141.41
49.
71.40
136.45
---
126.14
127.14
128.69
184.61
126.38, 129.92, 134.14,
139.14
50.
20.05
127.01
152.02
114.20
122.23, 124.40
120.21
174.29
124.70,129.47,136.62,
141.88
51.
20.32
123.02
150.10
119.91, 126.31
130.30
123.32
171.96
125.12, 127.01, 135.64,
141.08
52.
19.52
130.12
150.61
120.81
128.30
––
171.87
126.21, 127.91, 136.64,
140.41
53.
69.01
142.81
––
125.31
130.41
126.21
187.62
126.30, 129.92, 134.14,
139.54
54.
20.72
122.91
152.82
119.71
125.72, 128.71
120.22
170.87
125.30,127.01,136.64,
141.60
55.
21.62
126.81
150.81
119.41, 121.82
124.62
120.41
170.23
125.12, 127.01, 136.64,
140.68
176
RESULTS AND DISCUSSION
46.
21.11
130.42
151.90
120.11
129.82
––
170.47
126.21, 127.01, 136.64,
140.41
57.
68.52
141.02
––
125.91
131.01
126.81
188.23
126.38, 129.92, 134.14,
139.14
1,10-Phen
58.
20.04
127.89
150.81
114.20
129.47, 129.88
120.61
172.63
120.61,124.23,136.64,138.6
4, 142.88, 149.63
59.
20.01
134.64
150.80
112.20, 115.84
131.88
120.61
171.45
120.61,124.23,136.64,138.6
4, 142.88, 149.63
60.
20.04
129.88
150.81
114.20
127.01
---
174.23
120.61,124.23,136.64,138.6
4, 142.88, 149.63
61.
71.41
136.45
---
126.71
127.11
128.69
184.72
120.11,127.41,127.76,129.9
2, 134.71, 149.14
62.
20.62
127.89
150.81
114.70
129.97, 129.98
122.61
172.63
120.61,124.23,136.64,138.6
4, 142.88, 149.63
63.
20.01
134.65
150.82
112.20, 115.84
131.86
120.62
171.45
121.61,124.23,136.60,138.6
4, 142.88, 149.68
64.
20.21
129.80
151.01
114.32
127.91
---
174.54
120.53,124.13,136.10,139.9
4, 142.43, 149.60
65.
72.21
138.40
---
127.79
127.01
128.60
186.12
120.01,127.40,127.06,129.0
2, 134.71, 139.15
177
RESULTS AND DISCUSSION
56.
66.
21.08
127.06
150.81
114.20
129.47, 129.80
120.61
172.63
120.53,124.28,136.64,138.6
4, 142.88, 149.63
67.
20.61
134.53
150.89
112.20, 115.04
131.67
120.78
174.45
120.60,124.23,136.04,138.6
4, 142.67, 149.63
68.
20.84
129.86
151.09
114.22
127.01
---
174.29
120.53,124.03,136.60,138.9
4, 142.43, 149.60
69.
70.21
138.40
---
127.79
127.01
128.60
186.12
120.01,127.40,127.06,129.0
2, 134.71, 139.15
Bipy
19.28
124.70
152.94
113.02
130.75, 130.78
119.10
172.33
124.81, 128.95, 136.85,
147.44
71.
20.05
134.14
151.83
112.10,115.04
131.81
120.60
171.42
124.04, 136.52, 140.08,
141.60
72.
20.25
129.88
150.81
115.84
127.02
----
175.84
136.82,142.88,143.59
148.89
73.
71.14
136.71
--
126.61
127.00
128.69
184.62
128.45, 130.85, 147.68,
147.98
74.
21.08
124.79
152.90
113.32
132.75, 132.98
120.11
172.98
125.01, 126.05, 135.05,
147.09
75.
20.05
134.64
150.81
112.20,115.84
131.04
120.61
173.81
124.40, 136.82, 142.88,
149.63
RESULTS AND DISCUSSION
178
70.
76.
20.43
130.09
150.11
115.64
127.12
----
175.04
136.12,142.32,143.09
148.54
77.
71.09
136.70
--
126.61
127.00
128.69
188.02
130.08, 130.83, 147.61,
147.90
78.
19.28
124.70
152.94
113.02
130.75, 130.78
119.10
172.33
124.81, 128.95, 136.85,
147.44
79.
20.05
134.14
150.81
112.20,115.84
131.81
120.61
171.42
124.70, 136.83, 142.88,
149.04
80.
20.25
129.88
150.81
115.84
127.02
----
175.84
136.80,142.18,143.52
148.57
81.
71.09
136.71
--
126.60
127.09
128.69
184.62
128.45, 130.80, 147.60,
147.91
#
S. No. of the complexes is according to Table No. 3.17.
RESULTS AND DISCUSSION
179
Table 3.20: Mass spectral data of some of (ortho–, meta– and para–tolyl)/benzyl dithiocarbonates of zinc(II), cadmium(II) and
mercury(II) with nitrogen and phosphorus donor ligands
S. No.
M.W.
m/z, relative intensities of the ions and assignment
36.
590.1
[M+] 590 (10) [(p-CH3C6H4OCS2)2Zn.2NC5H5]; [M+] 431 (12) [(p-CH3C6H4OCS2)2Zn];
[M+] 280 (10) [(p-CH3C6H4OCS2)ZnS]; [M+] 183 (8) [p-CH3C6H4OCS2];
[M+] 79 (30) [NC5H5]; [M+] 107 (100) [p-CH3C6H4O]; [M+] 97 (30) [ZnS];
[M+] 76 (50) [CS2].
38.
665.1
[M+]665(17)[(o-CH3C6H4OCS2)2Cd.2NC5H5]; [M+] 478 (8) [(o-CH3C6H4OCS2)2Cd];
[M+] 328 (9) [(o-CH3C6H4OCS2)CdS]; [M+] 183 (9) [o-CH3C6H4OCS2];
[M+] 107(100) [o-CH3C6H4O]; [M+] 79 (16) [NC5H5];
42.
883.5
[M+] 883 (17) [(o-CH3C6H4OCS2)2Hg.2NC5H5]; [M+] 568 (19) [(o-CH3C6H4OCS2)2Hg];
[M+] 416 (19) [(o-CH3C6H4OCS2)HgS];
[M+] 183 (17) [o-CH3C6H4OCS2]; [M+] 79 (20) [NC5H5];
[M+] 107 (100) [o-CH3C6H4O]; [M+] 76 (50) [CS2];
[M+] 232 (30) [HgS].
RESULTS AND DISCUSSION
[M+] 144 (27) [CdS]; [M+] 76 (46) [CS2].
180
46.
946.4
[M+] 946 (15) [(o-CH3C6H4OCS2)2Zn.2P(C6H5)3]; [M+] 431 (6) [(o-CH3C6H4OCS2)2Zn];
[M+] 280 (14) [(o-CH3C6H4OCS2)ZnS]; [M+] 183 (7) [o-CH3C6H4OCS2];
[M-] 107 (100) [o-CH3C6H4O]; [M+] 76 (40) [CS2]; [M+] 97 (58) [ZnS].
51.
1009.5
+
+
[M ]1009 (9)[(m-CH3C6H4OCS2)2Cd.2P(C6H5)3]; [M ] 478 (8) [(m-CH3C6H4OCS2)2Cd];
[M+] 328 (8) [(m-CH3C6H4OCS2CdS];[M+] 183 (10) [m-CH3C6H4OCS2];
[M+] 265(29) [P(C6H5)3];[M+] 107 (100) [m-CH3C6H4O];
[M+] 76 (50) [CS2]; [M+] 144 (40) [CdS].
55.
1097.5
[M+]1097 (18)[(m-CH3C6H4OCS2)2Hg.2P(C6H5)3]; [M+] 567 (10) [(m-CH3C6H4OCS2)2Hg];
[M+] 416 (10) [(m-CH3C6H4OCS2HgS]; [M+] 183 (9) [m-CH3C6H4OCS2];
[M+] 232 (38) [HgS].
61.
612.1
[M+] 612 (17) [(C6H5CH2OCS2)2Zn.N2C12H8]; [M+] 431 (8) [(C6H5CH2OCS2)2Zn];
[M+] 183 (9) [C6H5CH2OCS2]; [M+] 107 (100) [C6H5CH2O]; [M+] 76 (66) [CS2];
[M+] 280 (10) [(C6H5CH2OCS2)ZnS]; [M+] 97 (27) [ZnS].
181
RESULTS AND DISCUSSION
[M+] 265(19) [P(C6H5)3];[M+] 107 (100) [m-CH3C6H4O]; [M+] 76 (56) [CS2];
[M+] 661 (11) [(p-CH3C6H4OCS2)2Cd.N2C12H8]; [M+] 478 (8) [(p-CH3C6H4OCS2)2Cd];
64.
661.1
[M+] 328 (8) [(p-CH3C6H4OCS2CdS]; [M+] 183 (9) [p-CH3C6H4OCS2];
[M+] 182(19) [N2C12H8];[M+] 107 (100) [p-CH3C6H4O];
[M+] 76 (39) [CS2]; [M+] 144(48) [CdS].
68.
749.5
[M+] 749 (11) [(p-CH3C6H4OCS2)2Hg.N2C12H8]; [M+] 567 (8) [(p-CH3C6H4OCS2)2Hg];
[M+] 416 (8) [(p-CH3C6H4OCS2)HgS]; [M+] 183 (9) [p-CH3C6H4OCS2];
[M+] 182(15) [N2C12H8];[M+] 107 (100) [p-CH3C6H4O];
[M+] 76 (36) [CS2]; [M+] 232 (48) [HgS].
75.
588.1
[M+] 588 (6) [(m-CH3C6H4OCS2)2Zn.N2C10H8]; [M+] 431 (8) [(m-CH3C6H4OCS2)2Zn];
[M+] 183 (5) [m-CH3C6H4OCS2]; [M+] 107 (100) [m-CH3C6H4O];
[M+] 97 (35) [ZnS]; [M+] 76 (80) [CS2].
77.
635.1
[M+] 635 (13) [(C6H5CH2OCS2)2Cd.N2C10H8]; [M+] 478 (8) [(C6H5CH2OCS2)2Cd];
[M+] 328 (10) [(C6H5CH2OCS2)CdS]; [M+] 183 (12) [C6H5CH2OCS2];
[M+] 156 (21) [N2C10H8]; [M+] 107 (100) [C6H5CH2O]; [M+] 76 (49) [CS2];
[M+] 144 (40) [CdS].
182
RESULTS AND DISCUSSION
[M+] 280 (10) [(m-CH3C6H4OCS2)ZnS];[M+] 248 (10) [(m-CH3C6H4OCS2)Zn];
81.
723.3
[M+] 723 (17) [(C6H5CH2OCS2)2Hg.N2C10H8]; [M+] 567 (8) [(C6H5CH2OCS2)2Hg];
[M+] 416 (8) [(C6H5CH2OCS2)HgS]; [M+] 183 (9) [C6H5CH2OCS2];
[M+] 156 (15) [N2C10H8]; [M+] 107 (100) [C6H5CH2O];
[M+] 76 (43) [CS2]; [M+] 232 (49) [HgS].
#
S.No. of the complexes is according to Table No. 3.17
RESULTS AND DISCUSSION
183
RESULTS AND DISCUSSION
Figure 3.47: The IR Spectrum of [(o-CH3C6H4OCS2)2Zn.2NC5H5] (34)
Figure 3.48: The IR Spectrum of [(m-CH3C6H4OCS2)2Cd.2NC5H5] (39)
184
RESULTS AND DISCUSSION
Figure 3.49: The IR Spectrum of [(p-CH3C6H4OCS2)2Hg.2NC5H5] (44)
Figure 3.50: The IR Spectrum of [(o-CH3C6H4OCS2)2Cd.2P(C6H5)3] (50)
185
RESULTS AND DISCUSSION
Hg-P
C-C
H3C
C=S
OCS2 Hg.2PPh
3
2
Hg-S
C-O-C
P-C
Figure 3.51: The IR Spectrum of [(p-CH3C6H4OCS2)2Hg.2P(C6H5)3] (56)
Figure 3.52: The IR Spectrum of [(p-CH3C6H4OCS2)2Zn.N2C12H8] (60)
186
RESULTS AND DISCUSSION
Figure 3.53: The IR Spectrum of [(m-CH3C6H4OCS2)2Cd.N2C12H8] (63)
Figure 3.54: The IR Spectrum of [(m-CH3C6H4OCS2)2Cd.N2C10H8] (75)
187
RESULTS AND DISCUSSION
Figure 3.55: The 1H Spectrum of [(p-CH3C6H4OCS2)2Hg.2NC5H5] (44)
Figure 3.56: The 1H Spectrum of [(m-CH3C6H4OCS2)2Cd.2P(C6H5)3] (50)
188
RESULTS AND DISCUSSION
Figure 3.57: The 1H Spectrum of [(p-CH3C6H4OCS2)2Zn.N2C12H8] (60)
Figure 3.58: The 1H Spectrum of [(m-CH3C6H4OCS2)2Cd.N2C10H8] (75)
189
RESULTS AND DISCUSSION
Figure 3.59: The 31P Spectrum of [(o-CH3C6H4OCS2)2Zn.2P(C6H5)3] (46)
Figure 3.60: The 31P Spectrum of [(m-CH3C6H4OCS2)2Cd.2P(C6H5)3] (51)
190
RESULTS AND DISCUSSION
Figure 3.61: The 31P Spectrum of [(C6H5CH2OCS2)2Hg.2P(C6H5)3] (57)
Figure 3.62: The 13C Spectrum of [(p-CH3C6H4OCS2)2Hg.2NC5H5] (44)
191
RESULTS AND DISCUSSION
Figure 3.63: The 13C Spectrum of [(o-CH3C6H4OCS2)2Cd.2P(C6H5)3] (50)
Figure 3.64: The 13C Spectrum of [(p-CH3C6H4OCS2)2Zn.N2C12H8] (60)
192
RESULTS AND DISCUSSION
Figure 3.65: The 13C Spectrum of [(m-CH3C6H4OCS2)2Cd.N2C10H8] (75)
193
RESULTS AND DISCUSSION
Structural Features
As already described, it would not be appropriate to predict a precise structure for
these complexes since no suitable crystals could be obtained for X-ray diffraction
analysis. However, on the basis of above analytical data, particularly, elemental
analyses, TGA, mass, IR, and NMR (1H,
13
C and
31
P) spectroscopic studies, a
probable geometry may be assigned to these complexes. The mass spectral data of
these complexes exhibited the monomeric nature. No deviations were found in the
elemental analyses (C, H, S, N and M). The IR spectra have shown all bands observed
in the parent metal(II)bis-dithiocarbonato moiety and bands characteristic of donor
ligands, which supports the formation of M─N and M─P bonds in these complexes.
The observations based on the IR spectral data are in consistent with the symmetrical
chelation of the dithiocarbonate ligand to the metal atom in these complexes. Besides
IR data, the chemical shift at 170.23–188.23 ppm for carbon nucleus of CS2 with
upfield shift (2–3 ppm) in 13C NMR spectra substantiates M–N and M–P bonding in
addition to M–S bonding in the complexes. In the 13C NMR spectra the occurrence of
signals due to donor base moiety in the aromatic region in addition to the bands of the
dithiocarbonate moiety in IR also supported the formation of these adducts. The
observations based on the IR spectral data are consistent with octahedral geometry of
these complexes. However, a signal in the region –5.05 to –3.70 ppm in the
complexes 53–64 in 31P NMR revealed the presence of triphenylphosphine moiety in
these complexes. TGA data also shows that these adducts can also form good
precursors for the synthesis of corresponding metal sulfides.
In view of above data and along with the literature reports,149-150, 168, 204, 206, 258
275, 280, 285-287
owing to variations in the mode of coordination of the dithiocarbonate
ligands and the steric demands of the donor ligands operating in these adducts,
distorted octahedral geometry may tentatively be proposed for these complexes as a
consequence of the bidentate behavior of the dithiocarbonate ligands in case of zinc,
cadmium and mercury adducts. The metal atom is coordinated by four sulfur atoms of
the two dithiocarbonate moiety and two nitrogen atoms of two pyridine molecules in
the compounds (34-45), leading to six coordination around the metal atom (Figure
3.72). In the compounds (46-57) metal atom is coordinated with the two phosphorus
atoms of the two triphenylphosphine molecules and four sulfur atoms of the two
194
RESULTS AND DISCUSSION
dithiocarbonate moieties (Figure 3.73). The hexacoordination around the metal atom
in the compounds (58-69) is achieved by coordination with four sulfur atoms of the
two dithiocarbonate ligands and two nitrogen atoms of the 1,10–phenanthroline
molecule as described in Figure 3.74 and same is the case observed for compounds
70-81 in which central metal exists in a distorted octahedral having N2S4 donor set
defined by four sulfur atoms from two chelating dithiocarbonate anions as well as two
nitrogen from a 2,2’-bipyridyl ligand (Figure 3.75). Each of the ligands coordinates
in a symmetric mode.
N
O C
H3C
CH3
S
S
C O
M
S
S
N
Figure 3.72 (a): Proposed octahedral geometry for [(o–, m– and p–
CH3C6H4OCS2)2M.2NC5H5]; M= Zn (34-36) , Cd (38-40) and Hg (42-44)
N
S
H2
C O C
S
S
M
H2
C O C
S
N
Figure 3.72 (b): Proposed octahedral geometry for
[(C6H5CH2OCS2)2M.2NC5H5]; M= Zn (37) , Cd (41) and Hg (45)
195
RESULTS AND DISCUSSION
H3C
S
O C
P
S
C O
M
S
S
CH3
P
Figure 3.73 (a): Proposed octahedral geometry for [(o–, m– and p–
CH3C6H4OCS2)2M.2P(C6H5)3]; M= Zn (46-48) , Cd (50-52) and Hg (54-56)
P
S
H2
C O C
S
S
M
H2
C O C
S
P
Figure 3.73 (b): Proposed octahedral geometry for
[(C6H5CH2OCS2)2M.2P(C6H5)3]; M= Zn (49) , Cd (53) and Hg (57)
196
RESULTS AND DISCUSSION
CH3
O
C
S
H 3C
S
S
O
C
M
S
N
N
Figure 3.74 (a): Proposed octahedral geometry for [(o–, m– and p–
CH3C6H4OCS2)2M.N2C12H8]; M= Zn (58-60) , Cd (62-64) and Hg (66-68)
CH2
O
S
S
S
C O
H2
C
C
M
S
N
N
Figure 3.74 (b): Proposed octahedral geometry for
[(C6H5CH2OCS2)2M.N2C12H8]; M= Zn (61) , Cd (65) and Hg (69)
197
RESULTS AND DISCUSSION
CH3
O
S
H3 C
S
S
O
C
C
M
S
N
N
Figure 3.75 (a): Proposed octahedral geometry for [(o–, m– and p–
CH3C6H4OCS2)2M.N2C10H8]; M= Zn (70-72) , Cd (74-76) and Hg (78-80)
S
H2
C O
S
S
C
H2C
O
C
M
S
N
N
Figure 3.75 (b): Proposed octahedral geometry for
[(C6H5CH2OCS2)2M.N2C10H8]; M= Zn (73) , Cd (77) and Hg (81)
198
“BIOLOGICAL ACTIVITY”
RESULTS AND DISCUSSION
SECTION-II
3.7: Biological Activity
General
The growing interest in the chemistry of sulfur donor ligands such as dithiocarbonates
is due to their biological activities as well as their widespread industrial application.8182, 85-86
These are widely used as acaricides, herbicides, fungicides in agriculture.
Concerning about the biological activities of xanthate derivatives, activities of the
xanthogen disulfides with lice, chiggers and ticks and their antifungal activity is
reported by Wakamori.287 Benzyl ester of alkylxanthic acid is found to have an
acaricidal and herbicidal activities. Most of these chemicals are alkyl-substituted
xanthates and not benzyl-substituted compounds. Although biological activities of
certain carbonates are sometimes found in the literature but no systematic study on
dithiocarbonates has been reported.287 Moreover a perusal of literature indicates that
the xanthate complexes have demonstrated potential activity as anti-tumor agents288
and also been used in agriculture as very good pesticides.288 The effects of pesticides
on the environment as a whole are complex and versatile processes. Due to this, there
is increasing interest in the synthesis of new compounds with antimicrobial properties.
In general the microbiological assay is based upon a comparison of inhibition of
growth of microorganisms by measured concentrations of test compounds with that
produced by known concentration of a standard antibiotic. Most of the early
investigations of these systems, performed several decades ago, were centred around
the use of sulfur ligands as an analytical reagents but interest in the synthesis and
characterization of these ligands has increased because of their potential biological
activity81-82 and agriculture.85-86 However, metal xanthates are extensively used as
pharmaceuticals, fungicides, pesticides50 agricultural reagents87-88 and quite recently
in therapy for HIV infections.79, 97, 290
Drug resistance has become a growing problem in the treatment of infectious
diseases caused by bacteria, fungi, parasite and virus. Infectious diseases like
diarrhoea, dysentery, tuberculosis, acute respiratory tract infections, AIDS and
recently SARS are global threat and their incidences are increasing significantly day
by day. In order to treat fungal infections, certain agents are known called antifungal.
199
RESULTS AND DISCUSSION
Antifungal is a substance that kills or inhibits the growth of fungi. An antifungal
medication is a medication used to treat fungal infection such as athlete's foot,
ringworm, candidiasis (thrush), serious infections such as cryptococcal meningitis and
others.290 Antifungal works by exploiting differences between mammalian and fungal
cells to kill off the fungal organism without dangerous effects on the host. Unlike
bacteria, both fungi and humans are eukaryotes. Thus fungal and human cells are
similar at the molecular level. This makes it more difficult to find or design drugs that
target fungi without affecting human cells. As a consequence, many antifungal drugs
cause side-effects. Some of these side-effects can be life-threatening if the drugs are
not used properly.290
Metals have an esteemed place within medical biochemistry, although until
recently this has been restricted predominantly to organic drugs. Recently however,
more research has been done in the area of inorganic chemistry, which has led to
developments in cancer care, infection control, diabetes, ulcers and neurological,
cardiovascular and anti-inflammatory drugs. Metal coordination complexes have been
widely studied for their antimicrobial and anticancer properties.291
The chemistry of zinc, cadmium and mercury dithiolate has been studied to
great extent. Zinc thiolate complexes plays an important role in the biological
chemistry and have stimulated numerous studies on zinc coordination compounds
with sulfur ligation.281 Zinc is an essential element for a great number of proteins,
including enzymes involved in signalling processes and transcription factors needed
in the regulation of gene expression. Through these actions, zinc plays an important
role in cell proliferation, differentiation and death.292 Besides its universal roles, zinc
may also exert its actions in an organspecific manner. Zinc is abundantly presented in
pancreatic -cells.293 It is co-secreted with insulin. Zinc is widely distributed in brain.
During synaptic activity, vesicular zinc is released into synaptic clefts, but recycled
into the synapses via a transporter mechanism.294 However, zinc may be released in
excessive amount, as much as several hundred micromolar, from excited presynaptic
neurons into synaptic clefts in stroke, trauma and seizure, to be cytotoxic to
neighbouring neurons.294-295 In patients with Alzheimer‟s disease, the zinc content is
abnormally elevated in various brain regions.296-297
200
RESULTS AND DISCUSSION
There is intense research interest on the adverse effects of the heavy metals
cadmium and mercury on human health.298 Cadmium in particular, has been
implicated in renal dysfunction, bone and liver disease and several types of cancer
including prostate and lung cancer.299 Cadmium increasingly persists in the
environment as a result of agriculture, smoking, industry and electronic waste
(including associated Ni-Cad batteries).300 A recent report concerning human
exposure to environmental chemicals determined that approximately 5% of the U.S.
population aged 20 years and older have concentrations of urinary cadmium that
heighten the risk of developing kidney dysfunction and low bone mineral density
(CDC 2005). These findings demonstrate the need for more research that addresses
the role of cadmium in human health. Other sulfur containing molecules such as
dithiocarbamates and alkylxanthates are also known to form stable complexes with
cadmium.198,
301
Attaining the appropriate balance between lipophilicity and
hydrophilicity of cadmium chelating agents and the corresponding complexes is
critical to the efficiency of mobility and excretion of cadmium in biological systems.
Lipophilicity has been shown to be key in the mobilization of intracellular
cadmium.302
Mercury, a worldwide pollutant from natural or anthropogenic sources,
can be globally transported and released to the environment. Mercury is present
in the environment as inorganic (mainly Hg0 and Hg2+) and organic (mainly
forms.303
MeHg)
Due to
their lipophilic characteristics and possibility of
bioaccumulation, organic species of Hg are more toxic than the inorganic
specie of
the
element.
Methylmercury is a well known toxic compound, a
neurotoxin that can be biomagnified across the trophic chain.304
Keeping in view of the above facts it was thought worthy to investigate the
biological potentiality of newly synthesised tolyl/benzyl dithiocarbonate ligands and
their metal complexes during the present course of investigations. In this study, these
compounds were screened for their antimicrobial activity against various microbes in
the hope of finding a new antimicrobial agent. Four different dithiocarbonate ligands
(as sodium salts), their disulfides and their Zn(II), Cd(II) and Hg(II) complexes have
been synthesized and these compounds were evaluated for their in vitro antimicrobial
activities against pathogens (one fungal strain and two bacterial) by Classical poison
201
RESULTS AND DISCUSSION
food method and Agar well diffusion method and also cytotoxicity of some of the
zinc complexes has been done by SRB method.
3.7.1: Antifungal Activity
The in vitro biological screening effects of the investigated ligands and their group 12
metal derivatives were tested against the pathogen „„Fusarium oxysporium‟‟ f. sp.
Capsici causing vascular wilt of chilli (Capsicum annum L. is unevocially an
important condiment throughout the world and are an important source of vitamin C)
by the poisoned food method using Potato Dextrose Agar (PDA) nutrient as the
medium. The linear growth of fungus in control and treatment were recorded at
different concentrations of the ligands, disulfides and their complexes with elements
of zinc triad.
Antifungal activities of sodium salt of (o-, m- and p-tolyl)/benzyl
dithiocarbonate ligand (1, 3), disulfides (6, 8) and derivatives of zinc (10, 23, 36, 46,
61, 71), cadmium (15, 27, 40, 53, 77) and mercury (19, 32, 45, 55, 67)
dithiocarbonate ligand have been measured and summarized in Table 3.21. Our
results show that parent compounds and the corresponding adducts of the parent
compounds both exhibit potent antifungal activities against Fusarium. The impact of
the metal was found in the antimicrobial activity against the tested fungal species. The
results obtained by the poison food method indicated that the coordination compounds
have enhanced activity compared with the ligands. The values obtained suggest that
aryl dithiocarbonate derivatives of cadmium and mercury are more fungitoxic than
their parent ligands, as well as derivatives of zinc. This shows that metal derivatives
are more fungitoxic than the chelating agent (Ligand) itself. The dithiocarbonates,
represented by the general structure -O-C(=S)-S-Ar, have no hydrophilic group. On
the contrary, these compounds are considered to be lipophilic. The enhanced activity
of the metal derivatives may be ascribed to the increased lipophilic nature of these
derivatives arising due to the chelation and toxicity of the metal chelates increases
with increasing concentration of the complexes, the inhibitory effect on the mycelial
growth of the fungus also increases, which can be explained on the basis of
Overtone‟s concept305 and Tweedy‟s Chelation theory.306 Metal ions are adsorbed on
202
RESULTS AND DISCUSSION
the cell walls of the microorganisms, disturbing the respiration processes of the cells
and thus blocking the protein synthesis that is required for further growth of the
organisms. Hence, metal ions are essential for the growth-inhibitory effects.307
According to Overtone‟s concept of cell permeability, the lipid membrane that
surrounds the cell favors the passage of only lipid-soluble materials, so lipophilicity is
an important factor controlling the antifungal activity. Upon chelation, the polarity of
the metal ion will be reduced due to the overlap of the ligand orbitals and partial
sharing of the positive charge of the metal ion with donor groups. In addition,
chelation allows for the delocalization of π-electrons over the entire chelate ring and
enhances the lipophilicity of the complexes. This increased lipophilicity facilitates the
penetration of the complexes into lipid membranes, further restricting proliferation of
the microorganisms. The variation in the effectiveness of different compounds against
different organisms depends either on the impermeability of the microbial cells or on
differences in the ribosomes of the cells.308 All of the metal complexes possess higher
antifungal activity than the ligand.309-310 Although the exact biochemical mechanism
is not completely understood, the mode of action of anti microbials may involve
various targets in the microorganisms. These targets include the following:

The higher activity of the metal complexes may be due to the different
properties of the metal ions upon chelation. The polarity of the metal ions will
be reduced due to the overlap of the ligand orbitals and partial sharing of the
positive charge of the metal ion with donor groups. Thus, chelation enhances
the penetration of the complexes into lipid membranes and the blockage of
metal binding sites in the enzymes of the microorganisms.311

Tweedy‟s chelation theory predicts that chelation reduces the polarity of the
metal atom mainly because of partial sharing of its positive charge with donor
groups and possible electron delocalization over the entire ring. This
consequently increases the lipophilic character of the chelates, favoring their
permeation through the lipid layers of the bacterial and fungal membrane.312

Interference with the synthesis of cellular walls, causing damage that can lead
to altered cell permeability characteristics or disorganized lipoprotein
arrangements, ultimately resulting in cell death.
203
RESULTS AND DISCUSSION

Deactivation of various cellular enzymes that play a vital role in the
metabolic pathways of these microorganisms.

Denaturation of one or more cellular proteins, causing the normal cellular
processes to be impaired.313
Also literature survey revealed that dithiocarbonates are well known as heavy-
metal chelating agents with a strong affinity for many divalent cations, as well as the
heavier elements and possess various biological activities. For example, their
chelating abilities can cause the inhibition of numerous metal-containing enzymes,
such as copper-containing dopamine-13-hydroxylase, superoxide dismutase (SOD),
glutathione peroxidase and cytochrome oxidase.314 All the complexes showed
promising result in inhibiting the mycelial growth of the fungus at a concentration of
250 ppm. The different inhibitory effect of the complexes can be correlated by their
different structures. The comparison of antifungal activity of the ligand and some of
the complexes is described diagrammatically in Figure 3.76-3.78. However the
complex of zinc triad was more efficient in suppressing the growth of pathogen than
the ligand. This indicates that the coordinated metal atom increases the antifungal
effects mainly in higher concentrations. The results were obtained by the poison food
method and are shown in Figures 3.79-3.81 and their comparison with the biocidal
activities of free ligands and newly formed complexes are summarized as follows:
1. All the aryl dithiocarbonate ligands (1, 3) possess a pronounced antifungal
effect against the fungus at higher concentration and less activity at low
concentration.
2. The disulfides (6, 8) of dithiocarbonates posses a little bit more activity than
the corresponding sodium salt of dithiocarbonates.
3. All the metal complexes have higher or equal activity against all microorganisms as compared with the free ligands.
4. Mixed dithiophosphato-dithiocarbonato complexes are proved to be more
potent antifungal agents as compared to simple bis-dithiocarbonato complexes.
5. As compared with zinc-dithiocarbonate (10, 23, 36, 46, 61, 71) complexes, the
inhibition zones of cadmium (15, 27, 40, 53, 77) and mercury (19, 32, 45, 55,
67) dithiocarbonates are more distinct and larger in size.
204
RESULTS AND DISCUSSION
6. In some cases complexes with diverse concentrations also showed equal
activities against fungal species. By comparison of antifungal behavior of these
synthesized complexes with their corresponding free ligands, we found that
these complexes exhibited greater antifungal effects over free ligands used due
to increase in lipophilic character of the metal complexes.
7. Due to the known effects (poisonous nature) of cadmium and mercury salts we
herein compare the antifungal activity of metal salts (cadmium chloride and
mercury chloride) with that of newly synthesized complexes of cadmium and
mercury.
8. The results shows that cadmium and mercury chloride has higher antifungal
effects when it is used individually compared to ligand (1, 3) itself and
complexes (15, 17, 27, 32, 55). This is due to the presence of chloride ion
which enhanced microbial activity due to the formation of hypochlorous acid
when free chloride upon oxidation resulting into chlorine (most plausibly, in
the cells of microorganism the oxidized form of NAD+ or NADP+ can acquire
two electron and get reduced to and as a result of this two chloride as counter
ion get oxidized) that react with water.301
9. However the cadmium complex show high or equal antifungal activity against
fungus compared to cadmium chloride and free ligand. So it can be concluded
that even though cadmium chloride has higher antifungal effects and this
combination reduce its activity, the complexes still show significant activity
that may in part be associated with the presence of cadmium, ligand and
specially anions.304
10. Akin to the above observation the complexes of mercury (19, 32, 55) also
shows increased or equal fungicidal activity than their corresponding mercury
salt.
11. However, adducts of cadmium and mercury show pronounced antifungal
activity as compared to the parent cadmium and mercury dithiocarbonate
complexes. Due to the presence of anions (strong donors) like pyridine,
triphenylphosphine, 1,10-phenanthroline and 2,2‟-bipyridyl.
205
RESULTS AND DISCUSSION
12. Maximum inhibition is seen at higher concentration i.e. at 250 ppm in case
representative complexes of zinc (23, 36, 46, 61, 71), cadmium (27, 40, 53, 77)
and mercury (19, 32, 45, 55).
13. Mixed ligand complexes of dithiocarbonates with alkylene dithiophosphate of
zinc, cadmium and mercury are found to show distinct activity against the
fungus Fusarium oxysporium.
14. As it is evident from the antifungal screening data, adducts of nitrogen and
phosphorous donor ligands are more potent than the parent complex which are
in turn more potent than the dithiocarbonate ligands.
15. Adducts by means of nitrogen donor bases are prove to be more fungicidal as
compared to phosphorous donor bases.
16. The inhibitor effect of the metal complexes are found in the order
Hg > Cd > Zn.
Figure 3.76: Comparison of anti-fungal activity of ligands and the complexes of
zinc(II)
206
RESULTS AND DISCUSSION
Figure: 3.77: Comparison of anti-fungal activity of cadmium chloride and
complexes of cadmium(II) with dithiocarbonates
Figure: 3.78: Comparison of anti-fungal activity of mercury chloride and
complexes of mercury(II) with dithiocarbonates
207
Table 3.21: In vitro evaluation of sodium salt of tolyl/benzyl dithiocarbonates, their disulfides and zinc complexes against the fungus
Fusarium oxysporum f. Sp. Capsici.
#
S.No.
Conc.
Colony
Inhibition
Conc.
Colony
Inhibition
Conc.
Colony
Inhibition
Conc.
Colony
Inhibition
Conc.
Colony
Inhibition
(ppm)
Diameter
Over
(ppm)
Diameter
Over
(ppm)
Diameter
Over
(ppm)
Diameter
Over
(ppm)
Diameter
Over
(cm)
control
(cm)
control
(cm)
control
(cm)
control
(cm)
control
(%)
(%)
(%)
(%)
1.
50
4.3
4.0
100
3.8
15.5
150
3.4
24.0
200
3.0
33.3
250
2.6
42.0
3.
50
4.4
2.2
100
3.5
22.2
150
3.2
28.8
200
3.0
33.3
250
2.9
35.5
6.
50
4.0
11.1
100
3.4
24.4
150
3.0
33.3
200
2.9
35.5
250
2.5
44.4
8.
50
3.9
13.3
100
3.5
22.2
150
3.2
28.8
200
2.7
40.0
250
2.4
48.8
10.
50
3.0
33.0
100
2.5
44.0
150
2.3
48.0
200
2.1
53.0
250
2.0
56.0
23.
50
3.0
44.4
100
2.7
46.0
150
2.3
54.0
200
2.0
60.0
250
1.7
66.0
36.
50
2.9
36.0
100
2.4
47.0
150
2.0
56.0
200
1.6
67.0
250
0.7
85.0
46.
50
2.9
36.0
100
2.4
47.0
150
2.4
47.0
200
2.0
56.0
250
1.5
67.0
61.
50
1.8
60.0
100
1.5
67.0
150
1.0
78.0
200
0.9
80.0
250
0.5
89.0
71.
50
3.2
29.0
100
2.7
40.0
150
2.4
47.0
200
2.2
51.0
250
1.9
58.0
S.No, according to Table No. 3.1, 3.5, 3.9, 3.13, 3.17; Control = 4.5cm
208
RESULTS AND DISCUSSION
#
(%)
Table 3.22: In vitro evaluation of cadmium, mercury salts and their complexes with dithiocarbonates against fungus Fusarium
oxysporum f. Sp. Capsici.
#
S.No.
Conc.
Colony
Inhibition
Conc.
Colony
Inhibition
Conc.
Colony
Inhibition
Conc.
Colony
Inhibition
Conc.
Colony
Inhibition
(ppm)
Diameter
Over
(ppm)
Diameter
Over
(ppm)
Diameter
Over
(ppm)
Diameter
Over
(ppm)
Diameter
Over
(cm)
control
(cm)
control
(cm)
control
(cm)
control
(cm)
control
(%)
(%)
(%)
(%)
CdCl2
50
1.5
66.6
100
1.0
77.7
150
0.8
82.2
200
0.6
86.6
250
0.5
89.0
15.
50
4.0
11.1
100
3.5
22.2
150
2.0
55.5
200
1.5
66.6
250
1.2
73.3
27.
50
2.5
44.4
100
2.0
55.5
150
1.5
66.6
200
0.7
84.4
250
0.6
86.6
40.
50
1.0
77.7
100
0.8
82.2
150
0.5
89.0
200
0.5
89.0
250
0.5
89.0
53.
50
2.0
55.5
100
1.5
66.6
150
1.0
77.8
200
0.7
84.4
250
0.5
89.0
77.
50
2.2
51.1
100
2.0
55.5
150
0.7
84.0
200
0.6
86.6
250
0.5
89.0
HgCl2
50
0.7
80.0
100
0.5
86.0
150
0.5
86.0
200
0.5
86.0
250
0.5
86.0
19.
50
1.2
65.7
100
1.0
71.4
150
0.9
74.2
200
0.7
80.0
250
0.5
86.0
32.
50
1.5
57.1
100
1.0
71.4
150
0.8
77.1
200
0.6
82.8
250
0.5
86.0
45.
50
1.5
57.1
100
1.0
71.4
150
0.7
80.0
200
0.5
86.0
250
0.5
86.0
55.
50
1.8
48.5
100
1.6
54.2
150
1.0
71.4
200
0.7
80.0
250
0.5
86.0
67.
50
1.3
62.8
100
1.0
71.4
150
0.8
77.1
200
0.6
82.8
250
0.5
86.0
S.No, according to Table No. 3.1, 3.5, 3.9, 3.13, 3.17; Control for Cd = 4.5cm; Hg = 3.5cm
RESULTS AND DISCUSSION
209
#
(%)
RESULTS AND DISCUSSION
Figure 3.79(a): Antifungal activity of
(o-CH3C6H4OCS2)Na (1)
Figure 3.79(b): Antifungal activity of
(p-CH3C6H4OCS2)Na (3)
Figure 3.79(c): Antifungal activity of
[o-CH3C6H4OCS2]2 (6)
Figure 3.79(d): Antifungal activity of
[p-CH3C6H4OCS2]2 (8)
210
RESULTS AND DISCUSSION
Figure 3.79(e): Antifungal activity of
[(o-CH3C6H4OCS2)2Zn] (10)
Figure 3.79(f): Antifungal activity of
[(m-CH3C6H4OCS2)Zn(S2POCH2C(CH3)2CH2O)]
(23)
Figure 3.79(g): Antifungal activity of
[(p-CH3C6H4OCS2)2Zn.2Py] (36)
Figure 3.79(g): Antifungal activity of
[(o-CH3C6H4OCS2)2Zn.2PPh3] (46)
211
RESULTS AND DISCUSSION
Figure 3.79(h): Antifungal activity of
[(o-CH3C6H4OCS2)2Zn.Phen] (61)
Figure 3.79(i): Antifungal activity of
[(m-CH3C6H4OCS2)2Zn.Bipy] (71)
Figure 3.80(a): Antifungal activity of
CdCl2
Figure 3.80(b): Antifungal activity of
[(m-CH3C6H4OCS2)2Cd] (15)
212
RESULTS AND DISCUSSION
Figure 3.80(c): Antifungal activity of
[(p-CH3C6H4OCS2)Cd(S2POCH2C(CH3)2CH2O)]
Figure 3.80(d): Antifungal activity of
[(p-CH3C6H4OCS2)2Cd.2Py] (40)
(27)
Figure 3.80(e): Antifungal activity of
[(C6H5CH2OCS2)2Cd.2PPh3] (53)
Figure 3.80(f): Antifungal activity of
[(C6H5CH2OCS2)2Cd.Bipy] (77)
213
RESULTS AND DISCUSSION
Figure 3.81(a): Antifungal activity
of HgCl2
Figure 3.81(c): Antifungal activity of
[(p-CH3C6H4OCS2)Hg(S2POCH2C(CH3)2CH2O)]
Figure 3.81(b): Antifungal activity of
[(m-CH3C6H4OCS2)2Hg] (19)
Figure 3.81(d): Antifungal activity
of [(C6H5CH2OCS2)2Hg.2Py] (45)
(32)
214
RESULTS AND DISCUSSION
Figure 3.81(e): Antifungal activity of
[(m-CH3C6H4OCS2)2Hg.2PPh3] (55)
Figure 3.81(f): Antifungal activity of
[(m-CH3C6H4OCS2)2Hg.Phen] (67)
3.7.2: ANTIBACTERIAL ACTIVITY
It is now widely recognized that the increase in bacterial resistance, the rapid
emergence of new infections and even over prescription of antibiotics have
significantly decreased the efficiency of drugs employed in the treatment of
pathologies instigated by certain microorganisms.316 Infections caused by Grampositive organisms are of major concern due to the increased incidence and the high
level of multidrug resistance. Increasing resistance in both enterococci (lactic acid
bacteria) and staphylococci (skin-colonizing bacteria) has accelerated the need for the
development of new antimicrobial agents to treat these Gram-positive infections.317
To treat the bacterial infections, antimicrobial agents also known as antibiotics are
given. The antibiotics discovered in the 1940s, were incredibly effective in the
treatment of many bacterial infections. Over time many antibiotics have lost their
effectiveness against certain types of bacteria because resistant strains have
developed, mostly through the expression of “resistant genes”. Antimicrobial drug
resistance is a major factor in the emergence and re–emergence of infectious diseases.
“Drugs that once seemed invincible are losing their effectiveness for a wide range of
community–acquired infections, including tuberculosis, gonorrhea, pneumococcal
infections (a leading cause of otitismedia, pneumonia, and meningitis) and for
215
RESULTS AND DISCUSSION
hospital–acquired enterococcal and staphylococcal infections. The development of
bacterial resistance to present day antibiotics has necessitated the search for new
chemical entities as antimicrobial agents. With the onset of the era of Biochemistry,
credence has been observed in screening the biological applications of chemical
compounds. Profound research has been done in this area whereby, microbes are
being screened and classified on the basis of their chemical characteristics.
Pathogens, particularly bacteria and yeast, coexist with harmless microbes on
or in their host. These pathogens must be properly screened for the actual cause of
infection. Typical numbers have been identified by their particular growth patterns
and biochemical characteristics. These characteristics vary depending on the type of
microbe, its habitat and functional diversity. This finds an elaborate application in
health and agriculture sector. This growing interest in the biochemical applications
and an interest in microbicides promoted us to screen our complexes against two
different types of bacteria. These numbers were chosen since these were medically
significant as potential pathogens for human beings. Hence analyzing their chemical
applications might be a step toward their control and eradication. The brief
morphological and chemical characteristics of the chosen microbial isolates are given
in Table 3.23. During the present course of investigations free ligands and their
complexes with zinc were tested in vitro against two bacterial strains involving one
Gram-negative i.e. Klebsiella pneumonia and one Gram-positive i.e. Bacillus cereus
to assess their antimicrobial properties. Table 3.23 shows morphological and
medicinal characteristics of the microbial isolates.
216
RESULTS AND DISCUSSION
Table 3.23: Morphological and medicinal characteristics of the microbial isolates
S.
Class
Morphology
Klebsiella
Gamma
(0.5-1.0 x
pneumonia
Proteobacteria
1.5-5.0) µm
Order
size,
Enterobacteriales
straight rods,
Family
Non-motile.
Scientific
Name
No.
1.
O2
Medical
requirement Significance
Anaerobic
Causes
pneumonia.
Enterobacteriaceae
2.
Bacillus
Bacilli
Straight or
Aerobic or
Causes
cereus
Order
slightly
Facultative
food-borne
Bacillales
curved
illness;
Family
slender
severe
Bacillaceae
bacilli with
nausea,
square ends
vomiting
singly or in
and
short chains.
diarrhoea.
Herein, the specific antimicrobial activity against two bacterial strains i.e.
Gram-positive bacteria Klebsiella pneumonia and Gram-negative bacteria Bacillus
cereus exhibited by a series of compounds is described. The results were obtained by
the well diffusion method, which is revealed in the table below. The comparison of
antibacterial activity of ligands and some of the complexes is described
diagrammatically in Figures 3.82 and 3.83.
217
RESULTS AND DISCUSSION
Table 3.24: In vitro evaluation of zinc(II) complexes for antibacterial activity
#
S. No.
Diameter of inhibition zone (cm) (conc. in ppm)
Klebsiella pneumonia (-)
Bacillus cereus (+)
250 ppm
500 ppm
1000 ppm
250 ppm
500 ppm
1000 ppm
2.
0
0
0
0
0
0
7.
0
0
0.5
0
0
0.3
10.
1.3
1.9
2.2
0.9
1.3
1.4
23.
1.4
2.0
2.5
1.2
1.7
2.1
36.
2.4
3.5
3.6
2.8
3.4
3.6
47.
1.6
2.5
2.7
2.2
2.7
3.2
60.
0.6
2.1
2.3
1.6
2.6
2.9
72.
2.2
2.8
3.2
0.8
1.7
2.2
Penicillin.
2.2
2.6
2.9
2.4
2.8
2.9
#
S.No, according to Table No. 3.1, 3.5, 3.9, 3.13, 3.17
218
RESULTS AND DISCUSSION
Figure 3.82: Comparative bacterial study of zinc(II) complexes against Gram
negative bacteria Klebsiella pneumonia
Figure 3.83: Comparative bacterial study of zinc(II) complexes against Gram
positive bacteria Bacillus cereus
As expected, our newly synthesized complexes showed an interesting
antibacterial activity. As is clear from the above table the free dithiocarbonate ligands
219
RESULTS AND DISCUSSION
have lower or zero activity towards the two tested bacteria than their metal derivatives
and correspondingly lower activity than the disulfides of dithiocarbonates.
Nevertheless, it is difficult to make an exact structure–activity relationship between
microbial activity and the structure of these complexes. It can be concluded that the
chelation increases the activity of these complexes. As chelation increases the
lipophilicity of these metal complexes by reducing polarity of metal centre due to the
overlap of the ligand orbitals and partial sharing of the positive charge of the metal
ion with donor groups. In addition, chelation allows the delocalization of π-electrons
over the entire chelate ring and enhances the lipophilicity of the complexes. This
increased lipophilicity facilitates the penetration of the complexes into lipid
membranes, further restricting proliferation of the microorganisms. The variation in
the effectiveness of different compounds against different organisms depends either on
the impermeability of the microbial cells or on differences in the ribosome of the
cells.308 All of the metal complexes possess higher antibacterial activity than the
ligand. Although the exact biochemical mechanism is not completely understood, the
mode of action of anti microbial may involve various targets in the microorganisms.
The results were obtained by the well diffusion method and are shown in Figures
3.84-3.92. Comparison of the antimicrobial activities of the free ligands and
synthesized complexes with some previously investigated antibiotics show the
following results:
1. The free ligands and their disulfides show a poor antibacterial effect
towards K. pneumonia and B. cereus than the reference drug penicillin.
However, the metal derivatives of dithiocarbonate ligands show a more
or less equal effect towards K. pneumonia and B. cereus compared with
penicillin.
2. The Klebsiella and Cereus both resist the disulfides (7) of
dithiocarbonate at lower concentration but at higher concentration i.e. at
2000 ppm it shows some inhibitor effect.
3.
The metal derivatives of zinc are found to be more effective against the
Gram-negative bacteria at all concentration compared to Gram-positive
bacteria which in turn is compared with penicillin.
220
RESULTS AND DISCUSSION
4.
Mixed
dithiocarbonate/dithiophosphate
complex
(23)
shows
comparatively more activity than the simple bis-dithiocarbonate
complex (10).
5. Some zinc derivatives (36, 47) show an equal antibacterial effect to that
of the antibiotic which is used as reference drug.
6.
The bis(o-tolyldithiocarbonate)zinc(II) show lesser effect towards both
bacterial strains compared with the known antibiotic pencillin.
7. Adducts with nitrogen and phosphorous donor ligands are found to be
more vigorous than their parent zinc derivative.
8. The pyridine adduct of bis(p-tolyldithiocarbonate)zinc(II) shows much
pronounced activity
at all the three concentration against the two
bacterial strains than compared with the reference drug penicillin.
9.
The comparative antibacterial activity of these complexes is
2 < 7 < 10 < 23 < 60 < 47 < 72 < 36.
From all of these results we can conclude that the free ligands shows zero
activity, their zinc derivatives are found to be less active but adduct
of zinc
dithiocarbonate with nitrogen donor ligand especially pyridine are more bactericidal
than the reference drug.
Figure 3.84(a): Antibacterial activity
of (m-CH3C6H4OCS2)Na (2) against
Klebsiella pneumonia
Figure 3.84(b): Antibacterial activity
of (m-CH3C6H4OCS2)Na (2) against
Bacillus cereus
221
RESULTS AND DISCUSSION
Figure 3.85(a): Antibacterial activity
of [m-CH3C6H4OCS2]2 (7) against
Klebsiella pneumonia
Figure 3.85(b): Antibacterial activity
of [m-CH3C6H4OCS2]2 (7)
against Bacillus cereus
Figure 3.86(a): Antibacterial activity of Figure 3.86(b): Antibacterial activity
[(o-CH3C6H4OCS2)2Zn] (10) against
of [(o-CH3C6H4OCS2)2Zn] (10)
Klebsiella pneumonia
against Bacillus cereus
222
RESULTS AND DISCUSSION
Figure 3.87(a): Antibacterial activity
[(m-CH3C6H4OCS2)Zn(S2POCH2C(CH3)2CH2O)]
(23) against Klebsiella pneumonia
Figure 3.88(a): Antibacterial activity of
[(p-CH3C6H4OCS2)2Zn.2Py] (36) against
Klebsiella pneumonia
Figure 3.87(b): Antibacterial activity
[(m-CH3C6H4OCS2)Zn(S2POCH2C(CH3)2CH2O)]
(23) against Bacillus cereus
Figure 3.88(b): Antibacterial activity
of [(p-CH3C6H4OCS2)2Zn.2Py] (36)
against Bacillus cereus
223
RESULTS AND DISCUSSION
Figure 3.89(a): Antibacterial activity
of [(m-CH3C6H4OCS2)2Zn.2PPh3] (47)
against Klebsiella pneumonia
Figure 3.89(b): Antibacterial activity
of [(m-CH3C6H4OCS2)2Zn.2PPh3] (47)
against Bacillus cereus
Figure 3.90(a): Antibacterial activity
of [(p-CH3C6H4OCS2)2Zn.Phen] (60)
against Klebsiella pneumonia
Figure 3.90(b): Antibacterial activity of
[(p-CH3C6H4OCS2)2Zn.Phen] (60) against
Bacillus cereus
224
RESULTS AND DISCUSSION
Figure 3.91(a): Antibacterial activity of
[(p-CH3C6H4OCS2)2Zn.Bipy] (72)
against Klebsiella pneumonia
Figure 3.92(a): Antibacterial activity
of antibiotic against Klebsiella
pneumonia
Figure 3.91(b):Antibacterial activity
of [(p-CH3C6H4OCS2)2Zn.Bipy] (72)
against Bacillus cereus
Figure 3.92(b): Antibacterial activity
of antibiotic against Bacillus cereus
225
RESULTS AND DISCUSSION
3.7.3: Cytotoxicity Analysis
In the present study the comparative evaluation of cytotoxicity of the ligand, (oCH3C6H4OCS2Na) (1) and representative complexes, [(o-CH3C6H4OCS2)2Zn] (10);
[(o-CH3C6H4OCS2)2Zn.2NC5H5] (34) and [(o-CH3C6H4OCS2)2Zn.2P(C6H5)3] (46) has
been done. The cytotoxicity was measured in vitro using the cultivated human cell
lines: lung adeno carcinoma cell line A-549, leukemia cell line THP-1, lung cervical
node cell line NCI-H322 and colorectal cancer cell line HCT-116. The inhibition
capacity was assessed using the sulforhodamine B (SRB) protein staining assay by
96-well technique described previously by Skehan318 et al.
This thesis pioneers the comparative study of cytotoxicity of dithiocarbonate
ligand and its complex. Since some of the dithiocarbonate complexes are known to be
act as good antitumor agents.288 As we have already discussed about zinc and its
bioactive properties under the subheading general in Section-II. All these
observations move us towards finding cytotoxicity of our newly synthesized aryl
dithiocarbonate ligand and its complex with zinc metal.
The cytotoxic properties of the sodium salt of dithiocarbonate ligand (oCH3C6H4OCS2Na) (1) and representative complexes, [(o-CH3C6H4OCS2)2Zn] (10),
[(o-CH3C6H4OCS2)2Zn.2NC5H5] (34) and [(o-CH3C6H4OCS2)2Zn.2P(C6H5)3] (46)
exhibited significant antitumor potency as shown in Table 3.25. The maximum
cytotoxic activity was observed against colon cancer cell line HCT-116. Complexes
of zinc are found to be more active agents as compared to dithiocarbonate ligand
alone. This shows that metal complex is rather more effective than the pure ligand and
it is likely that the zinc serves as a protective carrier for the ligand, ensuring that it
arrives intact at the active site due to its lipophilic nature. Moreover the complexation
of zinc ion with the ligand enhanced the anticancer behavior as is evident from the
values of the complexes compared to that of uncoordinated free ligand. The cytotoxic
activity is directly correlated to the structural properties of the molecules. The
comparative cytotoxicity data is well illustrated in the form of bar graphs in Figure
3.93.
226
RESULTS AND DISCUSSION
Table 3.25: In vitro evaluation of dithiocarbonate ligand and its zinc(II)
complexes for Cytotoxicity activity
Cell Line Type
#
THP-1
HCT-116
NCI-H322
A549
S.No.
Conc
(µM)
1.
100
0
65
24
34
10.
100
52
37
4
30
34.
100
96
96
70
94
46.
100
11
86
29
69
#
% Growth Inhibition
S.No. according to Table No. 3.1, 3.5, 3.9, 3.13, 3.17
Figure 3.93: Comparative Cytotoxic activity of dithiocarbonate ligand and its
zinc(II) complexes against different cell lines
227
SUMMARY
SUMMARY
4.1: General
This part of the thesis summarizes the research work carried out during the present
course of investigations, which has solely been described in the chapter-III. The work
embodied in this thesis deals with the synthesis and characterization of new (o–, m–
and p–tolyl)/benzyl dithiocarbonate complexes of group 12th elements viz. Zn(II),
Cd(II) and Hg(II) and their biological activity including antifungal, antibacterial and
cytotoxicity. The thesis also describes the synthesis and characterization of the
disulfides [(ArOCS2)]2 of these ligands. The adducts of the metal complexes with
nitrogen and phosphorus donor ligands corresponded to [{ArOCS2}2M.nL] (n = 1, L
= N2C12H8 and N2C10H8; n = 2, L = P(C6H5)3 and NC5H5) are also reported herein.
The synthetic routes in non-aqueous media under anhydrous conditions using standard
Schlenk technique have been utilized for the synthesis of new aryl dithiocarbonte
ligands and their corresponding disulfides because of the moisture sensitive nature.
The new complexes have been synthesized by using sodium salts of dithiocarbonates
viz. o-, m-, p-CH3C6H4OCS2Na and C6H5CH2OCS2Na with metal chlorides (ZnCl2,
CdCl2 and HgCl2). The structural elucidation of these complexes has been made on
the basis of elemental analyses, TGA, mass, IR and NMR (1H,
13
C and
31
P) spectral
data. The multinuclear NMR studies (1H and 13C) and Mass spectral data have proved
quite useful. The main results achieved during the present course of investigations are
being summarized under the following headings.
4.1: (ortho–, meta– and para–tolyl)/benzyl dithiocarbonate
ligands (1–4)
Reaction of sodium metal with ortho–, meta–, para–cresols (o–, m–, p–CH3C6H4OH)
and benzyl alcohol (C6H5CH2OH) in 1:1 stoichiometric ratio in refluxing toluene
resulted in the formation of sodium methylphenolates (o–, m–, p–CH3C6H4ONa) and
sodium phenylmethanolate (C6H5CH2ONa) as creamish viscous pasty masses.
Addition of an equimolar amount of CS2 at 0 – 5 °C forms the corresponding sodium
salt of (o–, m– and p–cresyl)/benzyl dithiocarbonates as a pale yellow solid (Scheme
4.1).
228
SUMMARY
ArOH
+
Na
Toluene
Reflux
ArONa
CS2
0-5oC
ArOCS2Na
[Ar = o-, m-, p-CH3C6H4 (1-3) and C6H5CH2 (4)]
Scheme 4.1: Synthesis of (o–, m–, p–CH3C6H4OCS2)Na and C6H5CH2OCS2Na
These sodium salts appear to be hygroscopic in nature, soluble in methanol,
ethanol, dichloromethane and tetrahydrofuran, insoluble in most of the hydrocarbon
solvents and sparingly soluble in chloroform. The elemental analysis (C, H and S) of
these ligands were found consistent with their composition.
The IR spectra show the characteristic sharp band for v(C─O─C) and broad
band for v(C
C) (tolyl and benzyl ring stretching). The strong intensity bands for
v(C═S) and v(C─S) were appeared in the range 1145–1140 cm–1 and 1008–1002 cm–1,
respectively. The v(C─H) vibrations (due to the tolyl and benzyl ring) were observed
in the region 3023–2991 cm–1.
The chemical shifts for the CH3 (tolyl ring) and CH2 (benzyl ring) protons
were observed in the region 2.26-2.36 ppm and 4.52 ppm as singlet. The chemical
shifts for tolyl and benzyl ring protons were observed at 6.60–7.35 ppm and 7.10–7.22
ppm with their usual splitting pattern.
The
13
C NMR spectra of these ligands have shown the appearance of the
chemical shift for all the carbon nuclei in their characteristic region. The –CH3 and –
CH2 carbon nuclei have shown their chemical shift at 22.01–22.92 ppm and 75.21
ppm, respectively. The chemical shifts of the ring carbons of the tolyl and benzyl
moieties displayed their resonances at 112.70–167.01 ppm. The signal for the carbon
nucleus of –(O)CS2 group has been observed in the region 195.14–220.70 ppm.
Mass spectra of these ligands (1–4) exhibited the molecular ion peak [M+] at
206 (m/z), suggested the monomeric nature of these ligands.
229
SUMMARY
Based on the above studies, following type of general structure may be
deduced for sodium salt of (o–, m– and p–tolyl)/benzyl dithiocarbonate ligands
(Figure 4.1).
H3C
S
O
C
S
CH2 O C
Na
S
Na
S
(b)
(a)
Figure 4.1: Structure of (o-, m-, p-CH3C6H4OCS2)Na (a) and
C6H5CH2OCS2Na (b)
4.2:
Disulfides
of
(ortho-,
meta-
and
para-tolyl)/benzyl
dithiocarbonates (6-9)
Oxidation of the sodium salt of tolyl/benzyl dithiocarbonate, ArOCS2Na (Ar = o–, m–
,
p–CH3C6H4– and C6H5CH2–), with iodine in chloroform under anhydrous
conditions resulted in the formation of bis(thiocarbonyl)–disulfanes corresponding to
(ArOCS2)2 in fairly good yield as yellow viscous compounds (Scheme 4.2). These
compounds (6-9) were also moisture sensitive and depicted similar solubility akin to
the compounds (1-4). The monomeric nature of these compounds was confirmed by
their mass spectral study.
ArOCS2Na + I2
CHCl3
-2NaI
S
S
Ar O C S S C O Ar
(6-9)
Scheme 4.2: Synthesis of (ArOCS2)2; Ar = o–, m–, p–CH3C6H4– (6-8) and
C6H5CH2– (9)
These compounds are non–volatile even under reduced pressure and tends to
decompose on heating and forming dark brown product having very pungent odour,
which, however, could not be characterized. These disulfides were obtained in
230
SUMMARY
sufficient purity as revealed by spectral studies. The elemental analyses, particularly
of sulfur, of all the disulfides (6–9) were found consistent to their molecular formula.
These compounds were further characterized by various spectral studies including
mass, IR and NMR (1H and 13C).
The IR spectra exhibited characteristic bands for the tolyl/benzyl
dithiocarbonate moieties along with marked shift toward lower wave number in the
position of (C–S) vibrations (950-899 cm–1) compared to parent dithiocarbonate
moiety, indicating the linkage of two sulfur atoms through covalent bond. These
compounds show appearance of new band of medium intensity for (S–S) in the
region 510–505 cm–1, indicating formation of bond between sulfur atoms of the two
ligands.
The chemical shifts for the CH3 (tolyl ring) and CH2 (benzyl ring) protons
were observed in the region 2.29-2.31 ppm and 4.01 ppm as singlet where as the tolyl
and benzyl ring protons of dithio moiety was appeared in the region 6.55–7.51 ppm
with their usual splitting pattern.
The
13
C NMR spectra of these compounds did not show any appreciable
deviation compared with the parent sodium salt of tolyl/benzyl dithiocarbonate
ligands. In 13C NMR spectra, signal for the carbon nucleus of –(O)CS2 group has been
observed in the region 165.01–188.05 ppm, supporting the authenticity of these
compounds.
Mass spectra of disulfides of benzyl and tolyl dithiocarbonate ligands show
their characteristic ion peak [M+] at m/z = 366. The occurrence of molecular ion peak
in the compound supported its monomeric nature.
In concurrence with the literature reports and based upon various physicochemical techniques viz. elemental analyses, molecular weight determinations and
spectral studies including mass, IR and NMR (1H and
13
C), following geometry is
proposed around each carbon atom in which only one sulfur atom of the tolyl/benzyl
dithiocarbonate ligand is involved in bonding with the sulfur of the other
dithiocarbonate ligand, leaving another sulfur atom non–bonded as shown in the
Figure 4.2.
231
SUMMARY
S
S
C
C
CH3
H3 C
O
O
S
S
(6-8)
S
S
H2
C
O
C
C
S
S
O
C
H2
(9)
Figure 4.2: Structure of (o-, m-, p-CH3C6H4OCS2)2 (6-8) and (C6H5CH2OCS2)2 (9)
4.3: Bis[(ortho-, meta and para-tolyl)/benzyldithiocarbonates]
of zinc(II), cadmium(II) and mercury(II) (10-24)
Reactions of MCl2 (M = Zn, Cd and Hg) with sodium tolyl/benzyl dithiocarbonates,
(ArOCS2)Na (Ar = o-, m-,
p-CH3C6H4– and C6H5CH2–), in 1:2 molar ratio in
hydrous conditions have resulted in the formation of [M(S2COAr)2] as white to
yellow solid in 72-84% yield (Scheme 4.3). These complexes are soluble in organic
solvents and can be kept unchanged in dry and nitrogen atmosphere. The analytical
data of elemental analyses (C, H, S, Zn, Cd and Hg) were found according to the
molecular composition of the complexes. The mass spectral study was found in
agreement with the monomeric nature of these complexes.
2ArOCS2Na + MCl2
H2O
stirring
15-45 min.
[M(ArOCS2)2] + 2NaCl
(10-21)
Scheme 4.3: Synthesis of [Zn(S2COAr)2] (10–13); [Cd(S2COAr)2] (14–17) and
[Hg(S2COAr)2] (18–21) [ Ar = o–, m–, p–CH3C6H4– (10–12, 14–16, 18-20) and
C6H5CH2– (13, 17, 21)]
232
SUMMARY
The comparison of IR spectra of these complexes with starting materials
has shown significant and characteristic changes and shifting of bands. The
presence of only one strong bond in the 1040-1015 cm-1 region, which is
associated with v(C
S) stretching vibrations, indicates complete symmetric
bidentate bonding by dithiocarbonate ligand. An additional band of weak to
medium intensity was observed in the dithiocarbonate complexes in the region
370-280 cm-1 which is ascribed to v(M—S) (M = Zn, Cd and Hg) stretching
vibration. This also indicates the coordination of the dithiocarbonate ligand with
the metal as expected. The strong bands of the v(C—O—C) asymmetric stretching
for bidentate coordinated dithiocarbonate ligands appear at 1250–1230 cm-1.
The 1H NMR (CDCl3) spectra of these derivatives show a mariginal shift
for all characteristic resonance signals compared to the parent dithiocarbonate
moieties. The chemical shift for the methyl protons of the tolyl dithiocarbonate
moiety appeared as singlet at 2.10-2.37 ppm where as the methylene protons of
the benzyl dithiocarbonato moiety resonated at 4.29–4.47 ppm as singlet. The
protons of the C6H4 (tolyl ring) and C6H5 (benzyl ring) in the zinc, cadmium and
mercury complexes gave signals in the region 6.73–7.14 and 7.01–7.25 ppm with
their usual splitting pattern and undergoing a negligible upfield shift as a
consequence of coordination.
The
13
C spectra of the compounds show the chemical shifts of all the
carbon nuclei in their characteristic region without any appreciable change
compared to the parent dithiocarbonate ligand. Evidence for the formation of the
complexes is clearly exhibited in the
13
C NMR spectra by occurrence of a sharp
peak for CS2 carbon with the upfield shift (25-30 ppm) compared to the parent
ligands. Most probably, this reflects the fact that environment around the CS2
carbon is the one most affected by the formation of the M–S bond.
The mass spectral data show the presence of molecular ion peak for
[M(S2COAr)2] [M= Zn, Cd and Hg; Ar = tolyl/benzyl] viz. m/z 431 (10), 478 (15,
16) and 567 (18, 21). Some other peaks of different fragments, which were formed
after consecutive dismissal of different groups, were observed. The occurrence of
molecular ion peak in the complexes is supporting the monomeric nature of the
complexes.
233
SUMMARY
The thermogravimetrical analysis of the representative complexes
conclude to one point that these complexes on thermal treatment lead to the
formation of corresponding metal sulfides. Cyclic voltammetric studies shows that
the metal i.e. Zn and Cd shows one electron redox process where as Hg shows two
electron redox process. The SEM images show the morphology of the complex.
Hence, on the basis of above studies and in conjunction with the literature
reports, mononuclear species with two chelating dithiocarbonate ligands that
forms a distorted tetrahedral array around the metal centre. Thus coordination
geometry around the metal atom is best described as a distorted tetrahedral
arrangement of the four sulfur atoms [MS4], two sulphur atoms from each
dithiocarbonate moiety as described in Figure 4.3 (a) and (b).
CH3
CH3
S
S
C O
M
O C
S
S
(a)
H2
C
S
S
O
C
M
H2
C O C
S
S
(b)
Figure 4.3: Proposed distorted tetrahedral geometry for (a) [(o-, m- and pCH3C6H4OCS2)2M] (10-12, 14-16and 18-20); (b) [(C6H5CH2OCS2)2M] (13, 17
and 21); [M = Zn, Cd and Hg]
4.4:
Mixed
dithiocarbonato–dithiophosphato
complexes
of
zinc(II), cadmium(II) and mercury(II) (22-33)
Mixed dithiocarbonate derivatives of Zn(II), Cd(II) and Hg(II) corresponding to [(o-,
m- and p-CH3C6H4)/C6H5CH2OCS2)M{S2POCH2C(CH3)2CH2O}] were synthesized
by the reaction of sodium tolyl/benzyl dithiocarbonates, (o-, m- and pCH3C6H4O)/C6H5CH2OCS2)Na
and
sodium
neopentylene
phosphorodithioate
OCH2C(CH3)2CH2OPS2Na with metal chloride in (1:1:1) molar ratio in aqueous
234
SUMMARY
medium. The complexes 22-33 were isolated as white to yellow solids in 69-79 %
yield (Scheme 4.4).
(ArOCS2)Na + OGOPS2Na + MCl2
(5)
(1-4)
H2O
stirring
~30 min
+ 2NaCl
[(ArOCS2)M(S2POGO)]
(22-33)
Scheme 4.4: Synthesis of [(ArOCS2)Zn(S2POGO)] (22-25);
[(ArOCS2)Cd(S2POGO)] (26-29); [(ArOCS2)Hg(S2POGO)] (30-33); [G =
{OCH2C(CH3)2CH2O}; Ar = o–, m–, p–CH3C6H4– (22-24, 26–28, 30-32) and
C6H5CH2– (25, 29, 33)]
These complexes are soluble in common organic solvents (toluene,
acetonitrile, methanol, chloroform), however, insoluble in solvents like n–hexane and
carbon tetrachloride. The elemental analyses, particularly C, H, S, Zn, Cd and Hg
were found consistent with the molecular formula of these complexes. The complexes
were further characterized by mass, IR, TGA and multinuclear NMR (1H,
13
C,
31
P)
spectroscopy. These studies showed that the coordination mode of both ligand types is
bidentate.
The comparison of IR spectra of these complexes with starting materials has
also shown seminal information. The absorption bands v(C─O─C) and v(C
H)
vibrations (due to the tolyl/benzyl ring) were observed in their characteristic region.
The appearance of only one strong band for v(C
S) vibrations in the range 1044-
1029 cm-1 without a shoulder indicates the bidentate behavior of the dithiocarbonate
ligand which depicted a shift of 10–30 cm–1 toward the lower frequency region. The
v(P—S)asym and v(P—S)sym mode may be characterized by the presence of a band in
the region 629-618 and 555-540 cm-1, respectively. The shift of ν(P─S) and ν(C
S)
vibrations is due to the bidentate mode of bonding by the dithio ligands with metal.
The presence of a new band for ν(M─S) in the region 371-280 cm–1 in the spectra of
these complexes is also indicative of the formation of metal–sulfur bond.
The 1H NMR data of the complexes (22-33) exhibited the characteristic
resonance for methyl and aryl protons. The values of the chemical shifts are found to
be similar to those of the ligands from which they were prepared so that there are no
significant changes as a result of being linked to different metals.
235
SUMMARY
The phosphorus atom of the dithiophosphate moiety in these complexes 22-33
appears as a singlet in the region 77.32-86.01 ppm in the 31P NMR spectra, indicating
its equivalent nature and is a strong indicator of the bidentate mode of binding by the
dithiophosphate. This singlet signifies the equivalent and symmetric nature of the
phosphorus atom.
The
13
C NMR spectra of these complexes have shown the chemical shifts of
all the carbon nuclei in their characteristic region without any appreciable change
compared to the parent ligand. The chemical shifts for CO carbon of the
dithiocarbonate and dithiophosphate moieties were found in the region 149.14-151.90
ppm and 72.01-73.09 ppm, respectively. The chemical shift for the dithiocarbonate
carbon (–OCS2) was appeared at 168.02-185.27 ppm with a upfield shift compared to
the parent ligands, which may be correlated with the coordination of the
dithiocarbonate ligand with the metal atom. The C– and –CH3 carbon nuclei of the
neopentylene moiety have shown their chemical shifts at 30.90-31.18 and 21.11-21.92
ppm.
The mass spectra of few representative complexes provide evidence for its
discrete monomeric nature as there is no fragment of mass higher than the monomeric
species. In the mass spectrum of [(m-CH3C6H4OCS2)Cd(S2POCH2C(CH3)2CH2O)]
(27), a molecular ion peak was observed at m/z 493 (17), The presence of the
dithiocarbonate moiety in the fragmentation pattern shows that dithiocarbonates are
stronger chelating agents as compared to alkylenedithiophosphate ligand.Thermal
studies (TGA) indicate the formation of metal sulfide as a final decomposition
product. The SEM images of the complexes show different types of topography and
morphology of the complexes. Images obtained at various magnifications show the
different texture of the complexes.
On the basis of above studies and in conjunction with the literature reports, an
overall four folded coordination must be existing around the zinc, cadmium and
mercury atom leading to distorted tetrahedral geometry due to bidentate mode of
chelation by dithio ligands in which each metal atom is surrounded by four sulfur
atoms two from each dithiocarbonate and dithiophosphate moiety respectively,
leading to MS4 configuration as described in Figures 4.5 a–b.
236
SUMMARY
H3C
S
S
O
C
O
P
M
CH3
C
O
S
S
CH2
CH3
CH2
Figure 4.5 (a): Proposed distorted tetrahedral geometry for
[(o-, m- and p-CH3C6H4OCS2)M(S2POCH2C(CH3)2CH2O)]; M =Zn (22-24), Cd
(26-28) and Hg (30-32)
S
C O C
H2
O
S
S
S
CH3
C
P
M
CH2
O
CH2
CH3
Figure 4.5 (b): Proposed distorted tetrahedral geometry for
[(C6H5CH2OCS2)M(S2POCH2C(CH3)2CH2O)]; M =Zn (25), Cd (29) and Hg (33)
4.5: Adducts of bis-[(ortho–, meta– and para–tolyl)/benzyl
dithiocarbonates] of zinc(II), cadmium(II) and mercury(II) with
nitrogen and phosphorus donors (34-81)
Adducts of mononuclear tolyl/benzyl dithiocarbonates of Zn, Cd and Hg with
heterocyclic amines and phosphines corresponding to [(ArOCS2)2M.nL] (Ar = o–, m–,
p–CH3C6H4– and C6H5CH2–; M = Zn, Cd and Hg; n = 2 for L = Py or PPh3 and n = 1
for L = 1,10–Phen or 2,2’-bipy) have been synthesized conveniently by the addition
reaction
of
donor
ligand
with
the
M(II)
dithiocarbonates
in
dichloromethane/chloroform in the required stoichiometry under normal condition.
The reactions with pyridine and triphenylphosphine were conducted in 1:2 molar ratio
while in 1:1 molar ratio was executed in case of 1,10–phenanthroline and 2,2’bipyridyl (Scheme 4.5).
237
SUMMARY
[(ArOCS2)2M] + nL
CH2Cl2/CHCl3
stirring
~ 30 min.
(10-21)
[(ArOCS2)2M.nL]
(34-81)
Scheme 4.5: Synthesis of [(ArOCS2)2M]; [Ar = o–, m–, p–CH3C6H4– and
C6H5CH2–; L = NC5H5, P(C6H5)3 (n = 2) or N2C12H8, N2C10H8 (n = 1)]
These compounds (34-81) were isolated as white to yellow solid in 77-89 %
yield. These compounds are soluble in common organic solvents like toluene,
benzene, dichloromethane and chloroform and insoluble in n–hexane. Mass spectral
studies of these compounds were found in agreement with the monomeric nature of
these compounds. These compounds were further characterized by various spectral
studies viz. IR, Mass, TGA, CV, 1H,
31
P and 13C NMR. The results of the elemental
analyses were in good agreement with those required by the proposed formulae.
The comparison of IR data of the complexes and donor stabilised complexes
with starting materials has shown some significant and characteristic changes like
shifting of bands (i.e. M–S vibrations) towards higher frequency, a small shift to low
frequency of v(C–S) vibrations and surprising comparatively large shift to lower
frequency of the v(C–O–C) vibrations. IR spectra of these complexes showed all the
bands observed in the parent metal(II)bis(dithiocarbonate) moiety (10-21) and bands
peculiar of the donor ligands like pyridine, 1,10-phenanthroline, 2,2’-bipyridyl and
triphenylphosphine in the region 756-740 and 555-525 cm-1, which may be assigned
to ν(M−N) and ν(M−P) vibrations (M = Zn, Cd and Hg), respectively.
The 1H NMR spectra of the addition complexes exhibited the characteristic
proton signals of the bis–(o–, m–, and p–tolyl/benzyldithiocarbonate)metal(II)
complexes. The chemical shifts of aromatic protons of the donor moiety pyridine,
triphenylphosphine, 1,10–phenanthroline and 2,2’-bipyridyl were found in the range
7.09-8.99 ppm, 7.20-7.64 ppm, 7.25-9.20 and 7.09-9.00 ppm. The deshielding of
protons indicates the coordination of the base to the metal centre.
238
SUMMARY
The 31P NMR spectra of the addition complexes with triphenylphosphine as
the donor ligand (46-57) exhibited the signal for the phosphorus atom of the
triphenylphosphine moiety as a singlet in the region –3.70 to –5.05 ppm.
The 13C NMR spectra of the addition complexes exhibited the signals in the
range 124.12-149.89, 124.70-141.88, 120.01-149.68 and 124.04-149.63 ppm for the
carbon nuclei of the donor moieties pyridine, triphenylphosphine, 2,2’-bipyridyl and
1,10-phenanthroline, respectively, in addition to other characteristic signals.
The
mass
spectra
of
few
representative
adducts
of
metal(II)bis(dithiocarbonate) complexes (36, 38, 42, 46, 51, 55, 61, 64, 68, 75, 77 and
81) have shown molecular ion peak [M+] at 590, 665, 883, 946, 1009, 1097, 612,
661, 749, 588, 635 and 723 in complexes, respectively, in addition to some other
peaks of different species which were formed after consecutive dismissal of different
groups. The presence of molecular ion peak [M+] is an indicative of the monomeric
complexes, which has also been revealed by molecular weight determination.
TGA data also shows that these adducts can also form good precursors for
the synthesis of corresponding metal sulfides. However, the thermal decomposition
result shows that octahedral addition complexes are more stable towards thermal
decomposition as compared to tetrahedral parent complexes. SEM studies show the
morphology (uneven rod like shape) of these complexes.
On the basis of the above studies and literature reports, distorted octahedral
geometry around metal atom in these complexes might exist as a consequence of
bidentate behavior of the tolyl/benzyl dithiocarbonate ligands. Two nitrogen atoms of
the two pyridine molecule are coordinated with metal atom in the complexes (34-45),
while two phosphorus atoms of the two triphenylphosphine molecules are coordinated
in the complexes (46-57). In case of the complexes (58-69) both the nitrogen atoms of
1,10-phenanthroline and both the nitrogen of bipyridyl (70-81) are coordinated with
the metal atom in addition to four sulfur atoms from two dithiocarbonate ligands to
achieve hexa-coordination (Figure 4.5 a-b -4.6 a-b).
239
SUMMARY
L'
H3C
S
O
C
S
C
M
S
O
S
CH3
L'
L' = Pyridine
or Triphenylphosphine
N
P
Figure 4.5 (a): Proposed octahedral geometry for [(o–, m– and p–
CH3C6H4OCS2)2M.2L’]; M= Zn (34-36, 46-48) , Cd (38-40, 50-52) and Hg
(42-44, 54-56)
L'
H2
C O C
S
S
M
S
H2
C O C
S
L'
L' = Pyridine
or Triphenylphosphine
N
P
Figure 4.5(b): Proposed octahedral geometry for
[(C6H5CH2OCS2)2M.2L’]; M= Zn (37, 49) , Cd (41, 53) and Hg (45, 57)
240
SUMMARY
CH3
O
C
S
H3 C
S
S
O C
M
S
N
N
N N = 1,10-phenanthroline
or
2,2'-bipyridyl
N
N
N
N
Figure 4.6(a): Proposed octahedral geometry for [(o–, m– and p–
CH3C6H4OCS2)2M.NN]; M= Zn (58-60, 70-72) , Cd (62-64, 74-76) and Hg (66-68,
78-80)
O
S
S
H2
C O C
CH2
C
S
M
S
N
N
N N = 1,10-phenanthroline
or
2,2'-bipyridyl
N
N
N
N
Figure 4.6(b): Proposed octahedral geometry for [(C6H5CH2OCS2)2M.NN]; M=
Zn (61, 73) , Cd (65, 77) and Hg (69, 81)
241
SUMMARY
4.6: Biological Activity
4.6.1: Antifungal Activity
The in vitro biological screening effects of the investigated ligands and their group 12
metal derivatives were tested against the pathogen ‘‘Fusarium oxysporium’’ f. sp.
Capsici causing vascular wilt of chilli by the poisoned food method using Potato
Dextrose Agar (PDA) nutrient as the medium.
Antifungal
activities
of
sodium
salt
of
(o-,
m-
and
p-
tolyl/benzyl)dithiocarbonate ligand (1, 3), disulphides (6, 8) and derivatives of Zinc
(10, 23, 36, 46, 61, 71), Cadmium (15, 27, 40, 53, 77) and Mercury (19, 32, 45, 55,
67) dithiocarbonate ligand have been measured. The ligand salt, disulfides, complexes
and their adducts exhibited potent antifungal activities against Fusarium. The impact
of the metal was found in the antifungal activity against the tested fungal species. The
results obtained by the poison food method indicated that the coordination compounds
have enhanced activity compared with the ligands. The values obtained suggest that
aryl dithiocarbonate derivatives of cadmium and mercury are more fungitoxic than
their parent ligands, as well as derivatives of zinc. The comparison of antifungal
activity of the ligand and some of the complexes is described diagrammatically in
Figure 4.7-4.9. However the complexes of group 12 metals were more efficient in
suppressing the growth of pathogen than the ligand. So, the coordinated metal atom
increases the antifungal effects mainly in higher concentrations. Results obtained by
comparison with the biocidal activities of free ligands and newly formed complexes in
the ascending order are as follows: aryl dithiocarbonate ligands (1, 3)  disulfides of
dithiocarbonates (6, 8)  zinc-dithiocarbonate (10, 23, 36, 46, 61, 71)  cadmium
dithiocarbonates (15, 27, 40, 53, 77)  mercury dithiocarbonates (19, 32, 45, 55, 67)
are more distinct and larger in size. Adducts by means of nitrogen donor bases are
prove to be more fungicidal as compared to phosphorous donor bases. Thus the
inhibitor effect of the metal complexes are found in the order Hg>Cd>Zn.
242
SUMMARY
Figure 4.7: Comparison of anti-fungal activity of ligands and the complexes of
zinc(II)
Figure: 4.8: Comparison of anti-fungal activity of cadmium chloride and
complexes of cadmium(II) with dithiocarbonates
243
SUMMARY
Figure: 4.9: Comparison of anti-fungal activity of mercury chloride and
complexes of mercury(II) with dithiocarbonates
4.6.2: ANTIBACTERIAL ACTIVITY
The growing interest in the biochemical applications and an interest in microbicides
promoted us to screen our complexes against two different types of bacteria. These
numbers were chosen since these were medically significant as potential pathogens
for human beings. Hence analyzing their chemical applications might be a step toward
their control and eradication. During the present course of investigations free ligands
and their complexes with zinc were tested in vitro against two bacterial strains
involving one Gram-negative i.e. Klebsiella pneumonia and one Gram-positive i.e.
Bacillus cereus to assess their antimicrobial properties. The results were obtained by
the well diffusion method revealed in the form of bar graph. As expected, our newly
synthesized compounds showed an interesting antibacterial activity. As is clear from
the graph the free dithiocarbonate ligands have lower or zero activity towards all
tested bacteria than their metal derivatives and lower activity than the disulfides of
dithiocarbonates. Nevertheless, it is difficult to make an exact structure–activity
relationship between microbial activity and the structure of these complexes. It can be
concluded that the chelation increases the activity of these complexes. The adducts of
group 12 metal derivatives of tolyl/benzyl dithiocarbonate with pyridine,
244
SUMMARY
triphenylphosphine, 1,10-phenanthroline
and 2,2’-bipyridyl showed the highest
activity towards all tested bacteria compared to the free dithiocarbonate ligands, the
disulfides of dithiocarbonates and their metal derivatives. The comparison of
antibacterial activity of ligands and some of the complexes is described
diagrammatically in Figures 4.10 and 4.11.
Figure 4.10: Comparative bacterial study of zinc(II) complexes against Gram
negative bacteria Klebsiella pneumonia
Figure 4.11: Comparative bacterial study of zinc(II) complexes against Gram
positive bacteria Bacillus cereus
245
SUMMARY
4.6.3: Cytotoxicity Analysis
In the present study the comparative evaluation of cytotoxicity of the ligand (oCH3C6H4OCS2Na) (1) and representative complexes [(o-CH3C6H4OCS2)2Zn] (10),
[(o-CH3C6H4OCS2)2Zn.2NC5H5] (34) and [(o-CH3C6H4OCS2)2Zn.2P(C6H5)3] (46) has
been done. The cytotoxicity was measured in vitro using the cultivated human cell
lines: lung adeno carcinoma cell line i.e. A-549, leukemia cell line THP-1, lung
cervical node cell line NCI-H322 and colorectal cancer cell line HCT-116.
The maximum cytotoxic activity was observed against colon cancer cell line
HCT-116. Complexes of zinc are found to be more active agents as compared to
dithiocarbonate ligand alone. This shows that metal complex is rather more effective
than the pure ligand, and it is likely that the metal serves as a protective carrier for the
ligand, ensuring that it arrives intact at the active site. The cytotoxic activity is
directly correlated to the structural properties of the molecules. The comparative
cytotoxicity data is well illustrated in the form of bar graphs in Figure 4.12.
Figure 4.12: Comparative Cytotoxic activity of dithiocarbonate ligand and its
zinc(II) complexes against different cell lines
246
REFERENCES
REFERENCES
1.
E. Fluck, “Pure Appl. Chem.”, 60, 431-436 (1988).
2.
G. S. Brady, R. H. Clauser and A. J. Vaccari, “Materials Handbook: An
encyclopaedia for managers, technical professionals, purchasing and
production
managers,
technicians
and
supervisors”,
Mc
Graw-Hill
Professional, 425 (2002).
3.
H. K. Wedepohl, “Geochim Cosmochim Ac.”, 59, 1217-1232 (1995).
4.
F. A. Cotton, G. Wilkinson, C. A. Murilo and M. Boechmann, “Advanced
Inorganic Chemistry”, 6th edition, Wiley-Interscience (1999).
5.
N. N. Greenwood, A. Earnshaw, “Chemistry of Elements”, 2nd edition, Oxford
Butterworth-Heinemann (1997).
6.
R. S. Lehto, “The Encyclopaedia of the Chemical Elements”, Reinhold Book
Corporation, New York, 822–830 (1968).
7.
H. L. Ehrlich, D. K. Newman, “Geomicrobiology”, CRC Press, 265 (2008).
8.
M. Kaupp and H. G. Von Schnering, Inorg. Chem., 33, 4718-4722 (1994).
9.
M. Kaupp and H. G. Von Schnering, Inorg. Chem., 33, 4179-4185 (1994).
10.
B. L. Vallee and K. H. Falchuk, Physiol Rev., 73, 79-118 (1993).
11.
A. S. Prasad, “Biochemistry of Zinc”, Plenum Press, New York, 219-258
(1993).
12.
R. Than, A. A. Feldmann and B. Krebs, Coord. Chem. Rev., 182, 211-241
(1999).
13.
M. Arora, Ph.D. Thesis, Rajasthan University, Jaipur (1966).
14.
J. A. Mc Cleverty, N. Speneer, N. A. Bailey and S. L. Shackleton, J. Chem.
Soc., Dalton Trans., 1939-1944 (1980).
15.
C. C. Ashworth, N. A. Bailey, M. Johnson, J. A. Mc Cleverty, N. Morrison
and B. Tabbiner, J. Chem. Soc., Chem. Commun., 743-744 (1976).
16.
N. Sreehari, B. Varghese and P. T. Manoharan, Inorg. Chem., 29, 4011-4015
(1990).
17.
G. A. Crosby, R. G. Highland and K. A. Truesdell, Coord. Chem. Rev., 64, 4152 (1985).
18.
K. A. Truesdell and G. A. Crosby, J. Am. Chem. Soc., 107, 1787-1788 (1985).
247
REFERENCES
19.
R. G. Highland, J. G. Brummer and G. A. Crosby, J. Phys. Chem., 1593-1598
(1986).
20.
G. S. H. Lee, D. C. Crag, I. Ma, M. L. Scudder, T. D. Bailley and I. G. Dance,
J. Am. Chem. Soc., 110, 4863-4864 (1988).
21.
K. H. Jordan, W. F. Wachaltz and G. A. Crosby, Inorg. Chem., 30, 4588-4593
(1991).
22.
C. Zharg, R. Chadha, H. K. Reddy and G. N. Schrauzer, Inorg. Chem., 30,
3865-3869 (1991).
23.
P. J. Gronlund, W. F. Wacholtz and J. T. Mague, Acta Crystallogr. Sec. C, 51,
1540-1543 (1995).
24.
G. Jorge, G. Raquel, G. Oscar, B. Salvador, G. E. Enrique and P. Fernando,
Chem. Commun., 48, 1994-1996 (2012).
25.
J. H. Mennear, “Cadmium Toxicity,” Dekker, New York, 224 (1979).
26.
J. S. Thayer, “Organometallic Compounds and Living Organisms”, Academic
Press, New York (1984).
27.
J. S. Thayer, “Organometallic Chemistry”, VCH Publishers, New York,
(1988).
28.
J. D. Thrasher, “Drugs and the Cell Cycle,” Academic Press, New York, 25
(1984).
29.
J. J. Lipka, S. J. Lippard and J. S. Wall, Science, 206, 1419-1421 (1979).
30.
W. C. Zeise, Rec. Mem. Acad. R. Sci. Copenhagen, 1, 1 (1815).
31.
R. F. Semeniuc, T. J. Reamer, J. P. Blitz, K. A. Wheeler and M. D. Smith,
Inorg. Chem., 49, 2624-2629 (2010).
32.
W. Ngobeni and G. Hangone, S. Afr. Chem. Eng., 18, 41-50 (2013).
33.
K. N. Han and X. Meng, U. S. Patent 5114687 A, 5 (1992); Chem. Abstr., 43,
2063694 (1994).
34.
R. E. Wing and W. M. Doane, U. S. Patent 695617 A, 37 (1976); Chem.
Abstr., 1063103 (1979).
35.
D. Coucouvanis, Prog. Inorg. Chem., 26, 302 (1979).
36.
K. Lee, D. Archibald, J. McLean and M. A. Reuter, Miner. Eng., 22, 395-401
(2009).
37.
A. F. Taggart, “Handbook of Mineral Dressing”, Wiley, New York (1960).
248
REFERENCES
38.
E. J. Pryor, “Minning processing”, Minning Publication Ltd., London (1960).
39.
A. M. Gaudin, “Flotation”, Mc Graw Hill, New York, 436-446 (1957).
40.
G. Groux and S. Lemarchand, Rev. Gen. Coautchouc, 28, 867-871 (1951);
Chem. Abstr., 46, 2327c (1952).
41.
E. Morita, U. S. Patent 4496683 A (1985); Chem. Abst., 1222343 (1987).
42.
S. Palaty and R. Joseph, Iran Polymer J., 13, 85-91 (2004).
43.
S. Palaty and R. Joseph, Plastics, Rubber and Composites, 30, 270-274
(2001).
44.
P. B. Sulekha, Ph.D Thesis, Cochin University of Science and Technology,
Kochi (2002).
45.
P. Karmitz, Rev. Gen. Caoutchouc, 35, 913 (1958).
46.
V. Vaclavek, J. Appl. Polymer Sci., 11, 1881-1902 (1967).
47.
J. Lal and J. E. McGrath, J. Polymer Sci. Part A: Polymer Chem., 5, 785
(1967).
48.
B. Quiclet-Sire, A. Wilczewska and S. Z. Zard, Tetrahedron Lett., 41, 56735677 (2000).
49.
D. R. May and I. M. Kolthoff, J. Polymer Sci., 4, 735-743 (1949).
50.
S. R. Rao, “Xanthates and Related Compounds”, Marcel Dekker, Inc., New
York (1971).
51.
N. Donoghue, E. R. T. Tiekink and L. Webster, Appl. Organomet. Chem., 7,
109-117 (1993).
52.
M. W. Whitehouse, P. D. Cookson, G. Siasios and E. R. T. Tiekink, MetalBased Drugs, 4, 245-249 (1998).
53.
M. Scendo, Corrosion Science, 47, 1738-1749 (2005).
54.
P. Wenger, R. Duckartand and E. Ankadji, Helv. Chim. Acta, 28, 1992-1609
(1945); Chem. Abstr., 40, 1410 (1946).
55.
A. K. Malik, K. N. Kaul, B. S. Lark, W. Faubel and A. L. J. Rao, Turk. J.
Chem., 25, 99-105 (2001).
56.
C. F. Cross, E. J. Bevan and C. Beadle, J. Chem. Soc., Trans., 67, 433-451
(1895).
57.
K. A. Malyshevskaya, N. A. Mazur, I. P. Dimitrenko, Fibre Chem., 12, 353354 (1980).
249
REFERENCES
58.
J. C. Casagrande, M. R. Soares and E. R. Mouta, Pesq. Agropec. Bras.,
Brasilia, 43, 131-139 (2008).
59.
S. R. Rao, “Surface Chemistry of Froth Flotation”, 2nd edition, Biskhauser
(2004).
60.
H. T. Kim and K. Lee, Korean J. Chem. Engin., 16, 298-302 (1999).
61.
C. M. Lauderback, J. Drake, D. Zhou, J. M. Hackett, A. Castegna, J. Kanski,
M. Tsoras, S. Varadarajan and D. A. Butterfield, Free Radic. Res., 37, 355365 (2003).
62.
G. Sauer, E. Amtmann, K. Melber, A. Knapp, K. Hummel and A. Scherm,
Proc. Natl. Acad. Sci. USA, 81, 3263-3267 (1984).
63.
(a) S. Shahzadi, S. Ali, R. Jabeen and M. K. Khosa, Turk J. Chem., 33, 307312 (2009).
(b) V. Pejchal, J. Holecek, M. Nadvornik and A. Lycka, Collect. Czech.
Chem. Comm., 60, 1492-1501 (1995).
64.
G. Exarchos, S. Robinson and J. Steed, Polyhedron, 20, 2951-2963 (2001).
65.
M. J. Cox and E. R. T. Tiekink, Z. Kristallogr., 211, 111-113 (1996).
66.
S. Vastag, L. Marko and A. L. Rheingold, J. Organomet. Chem., 397, 231238 (1990).
67.
M. Moran, I. Cuadrado, J. R. Masaguer, J. Losada, C. Foces-Foces and F. H.
Cano, Inorg. Chim. Acta, 143, 59-70 (1998).
68.
M. Moran, I. Cuadrado, C. Monozreja, J. R. Masaguer and J. Losada, J.
Chem. Soc., Dalt. Trans., 149-160 (1998).
69.
M. Moran, I. Cuadrado, J. R. Masaguer and J. Losada, J. Organomet. Chem.,
335, 255-266 (1987).
70.
M. F. Hussain, R. K. Bansi, B. K. Puri and M. Satake, Analyst, 109, 11511153 (1984).
71.
J. E. Drake, A. B. Sarkar and M. L. Y. Wong, Inorg. Chem., 29, 785-788
(1990).
72.
S. Ghoshal and V. K. Jain, J. Chem. Sci., 119, 583-591 (2007).
73.
P. F. R. Ewings, P. G. Harrison and T. J. King, J. Chem. Soc., Dalton Trans.,
1399-1403 (1976).
74.
K. Xu, W. Ding, W. Meng and F. Hu, J. Coord. Chem., 56, 797-801 (2003).
250
REFERENCES
75.
J. P. Fackler, D. Coucouvanis, J. A. Fetchin and W. C. Seidel, J. Am. Chem.
Soc., 90, 2784-2788 (1968).
76.
I. Ara and F. E. Bahij, Trans. Met. Chem., 28, 908-912 (2003).
77.
M. C. Gimeno, E. Jambrina, A. Laguna, M. Laguna, H. H. Murray and R.
Terroba, Inorg. Chim. Acta, 249, 69-73 (1996).
78.
F. H. Allen and O. Kennard, Chem. Des. Autom. News, 8, 31-37 (1993).
79.
H. W. Chen and J. P. Fackler, Inorg. Chem., 17, 22-26 (1978).
80.
A. G. Roura, J. Casas and A. Lebaria, Lipids, 37, 401-406 (2002).
81.
J. V. Rao, Y. Venkateswarlu and K. V. Raghavan, U.S. Patent 6583175 B2
(2003).
82.
W. Friebolin, G. Schilling, M. Zoller and E. Amtmann, J. Med. Chem., 48,
7925-7931 (2005).
83.
S. Palaty and R. Joseph, J. App. Polym. Sci., 78, 1769-1775 (2000).
84.
W. J. Orts, R. E. Sojka and G. M. Glenn, Agro Food Industry, 37, 1078-1084
(2002).
85.
J. H. G. Slanger and P. Kerkhoff, Nut. Cycl. Agroecosys., 5, 1-76 (1984).
86.
A. M. Mansour, W. B. Connick, R. J. Lachicotte, H. G. Gysling and R. J.
Eisenberg, J. Am. Chem. Soc., 120, 1329-1330 (1998).
87.
V. W. W. Yam, C. L. Chan, C. K. C. Li and K. M. C. Wong, Coord. Chem.
Rev., 173, 216-217 (2001).
88.
H. Adams, D. Bradshaw and D. A. Fenton, Inorg. Chem .Commun., 5, 12
(2002).
89.
A. V. Ivanov, V. I. Mitrofanova, M. Kritiokos and O. N. Antzutkin,
Polyhedron, 18, 2069-2078 (1999).
90.
(a) D. Swenson, N. C. Baenziger, D. J. Coucouvanis, J. Am. Chem. Soc., 100,
1932-1934 (1978).
(b) I. G. J. Dance, J. Am. Chem. Soc., 102, 3445-3451 (1980).
(c) K. S. Hagen, D. W. Stephan and R. H. Holm, Inorg. Chem., 21, 39283936 (1982).
91.
T. Turk, U. Resch, M. A. Fox and A. Vogler, Inorg. Chem., 31, 1854-1857
(1992).
251
REFERENCES
92.
G. Kriuter, V. L. Goedken, B. Neumuiiler and Jr. W. S. Rees, Mat. Res. Soc.
Proc., (1994).
93.
Y. Y. Niu, H. W. Hou and Y. Zhu, J. Cluster Sci., 14, 483-493 (2003).
94.
X. L. Yang, S. B. Ren, J. Zhang, Y. Z. Li, H. B. Du and X. Z. You, J. Coord.
Chem., 62, 3782-3794 (2009).
95.
T. Kuzuya, Y. Tai, S. Yamamuro, T. Hihara, D. L. Peng and K. Sumiyama,
Mat. Trans., 45, 2650-2652 (2004).
96.
M. S. Bharara, Ph. D Thesis, University of Kentucky, Kentucky (2006).
97.
T. Vossmeyer, G. Reck, L. Katsikas, E. T. K. Haupt, B. Schulz and H.
Weller, lnorg. Chem., 34, 4926-4929 (1995).
98.
A. X. Zheng, H. F. Wang, C. Ning, Z. G. Ren, H. X. Li and J. P. Lang, J.
Chem. Soc., Dalton Trans., 558-566 (2012).
99.
C. Xua, F. H. Wua, T. Duana and Q. F. Zhanga, Z. Naturforsch., 64b, 805 –
808 (2009).
100.
G. Henkel, P. Betz and B. Krebs, J. Chem. Soc., Chem. Commun., 14981499 (1985).
101.
W. Guo, Z. Peng, D. Li and Y. Zhou, Polyhedron, 23, 1701-1707 (2004).
102.
Q. H. Wang, D. L. Long, H. M. Hu, Y. Cui and J. S. Huang, J. Coord.
Chem., 49, 201-209 (2000).
103.
V. Madhu and S. K. Das, J. Chem. Soc., Dalton Trans., 40, 12901-12908
(2011).
104.
P. J. Gronlund and W. F. Wacholtz, Acta Cryst. C, 51, 1540-1543 (1995).
105.
N. L. Narvor, N. Robertson, E. Wallace, J. D. Kilburn, A. E. Underhill, P. N.
Bartlett and M. Webster, J. Chem. Soc., Dalton Trans., 6, 823-828 (1996).
106.
F. Maratini, L. Pandolfo, S. Rizzato, A. Albinati, A. Venzo, E. Tondello and
S. Gross, Eur. J. Inorg. Chem., 22, 3281-3283 (2011).
107.
J. Chaturvedi, S. Singh, S. Bhattacharya and H. North, Inorg. Chem., 50,
10056-10069 (2011).
108.
J. Chaturvedi, S. Bhattacharya and R. Prasad, J. Chem. Soc., Dalton Trans.,
39, 8725-8732 (2010).
109.
J. J. Vittal, J. T. Sampanthar and Z. Lu, Inorg. Chim. Acta, 343, 224-230
(2003).
252
REFERENCES
110.
M. Rombach, H. Brombacher and H. Vahrenkamp, Eur. J. Inorg. Chem., 1,
153-159 (2002).
111.
C. V. Amburose, T. C. Deivaraj, G. X. Lai, J. T. Sampanthar and J. J. Vittal,
Inorg. Chim. Acta, 332, 160-166 (2002).
112.
J. T. Sampanthar, T. C. Deivaraj, J. J. Vittal and P. A. W. Dean, J. Chem.
Soc., Dalton Trans., 4419-4423 (1999).
113.
M. D. Nyman, M. J. Hampden-Smith and E. N. Duesler, Inorg. Chem., 36,
2218-2224 (1997).
114.
M. Ruf and H. Vahrenkamp, Inorg. Chem., 35, 6571-6578 (1996).
115.
M. Hofbauer, M. Mobius, F. Knoch and R. Benedix, Inorg. Chim. Acta, 247,
147-154 (1996).
116.
D. V. Sanchez, G. Beobide, O. Castillo and M. Lanchas, Eur. J. Inorg.
Chem., 32, 5592-5602 (2013).
117.
E. Iniguez, J. Pastor-Medrano, F. Urena-Nunez, J. Flores-Estrada and T. J.
Morales-Juarez, J. Coord. Chem., 60, 327-337 (2007).
118.
J. Cruz-De La Cruz, F. Urena-Nunez, J. Morales-Juarez, J. Pastor-Medrano
and R. M. Gomez-Espinosa, J. Coord. Chem., 61, 3253-3259 (2008).
119.
S. Singh, J. Chaturvedi, A. S. Aditya, N. R. Reddy and S. Bhattacharya,
Inorg. Chim. Acta, 396, 6-9 (2013).
120.
V. V. Savant, J. Gopalakrishnan and C. C. Patel, Inorg. Chem., 9, 748-751
(1970).
121.
Z. Zhang, W. P. Lim, C. T. Wong, H. Xu, F. Yin and W. S. Chin,
Nanomaterials, 2, 113-133 (2012).
122.
J. Nieuwenhuizen, A. W. Ellers, J. G. Haashoot, S. R. Janse, J. Reedijk and
J. Baernads, J. Am. Chem. Soc., 121, 163-168 (1999).
123.
E. E. Casa, A. Sanchez, J. B. Vavo, S. Garcia-Fontan, E. E. Castellano and
M. M. Jones, Inorg. Chim. Acta, 158, 119-126 (1989).
124.
M. M. Jones and S. G. Jones, Inorg. Chim. Acta, 79, 288-289 (1983).
125.
R. D. Pike, H. Cui, R. Kershaw, K. Dwight, A. Wold, T. N. Blanton, A. A.
Wernberg and H. J. Gysling, Thin Solid Films, 224, 221-226 (1993).
126.
N. Srinivasan and S. Thirumaran, Superlattices Micro., 51, 912-920 (2012).
127.
P. O'Brien, D. J. Otway and J. R. Walsh, Thin Solid Films, 315, 57-61 (1998).
253
REFERENCES
128.
V. G. Bessergenev, E. N. Ivanova, Y. A. Kovalevskaya, I. G.Vasilieva, V. L.
Varand, S. M. Zemskova, S. V. Larinov, B. A. Kolesov, B. M. Ayupov and
V. A. Logvinenko, Mater. Res. Bull., 32, 1403-1410 (1997).
129.
D. C. Onwudiwe and P. A. Ajibade, Polyhedron, 29, 1431-1436 (2010).
130.
K. Hagen, C. J. Holwill and D. A. Rice, Inorg. Chem., 28, 3239-3242 (1989).
131.
M. J. Cox and E. R. T. Tiekink, Z. Kristallogr., 214, 184-190 (1999).
132.
A. Decken, R. A. Gossage, M. Y. Chan, C. S. Lai and E. R. T. Tiekink, Appl.
Organometal. Chem., 18, 101-102 (2004).
133.
F. A. A. Paz, M. C. Neves, T. Trindadeb and J. Klinowski, Acta Crystallogr.,
59, 1067-1069 (2003).
134.
E. R. T. Tiekink, Cryst. Eng. Comm., 5, 101-113 (2003).
135.
H. P. Klug, Acta Crystallogr., 21, 536-546 (1966).
136.
M. Y. Chan, C. S. Lai and E. R. T. Tiekink, Appl. Organometal. Chem., 18,
298 (2004).
137.
N. A. A. Ghafar, I. Baba, B. M. Yamina and S. Weng Ng, Acta Crystallogr.
E, 66, 208 (2010).
138.
S. L. Chian and E. R. T. Tiekink, Appl. Organometal. Chem., 18, 197-198
(2004).
139.
L. H. V. Poppel, T. L. Groy and M. T. Caudle, Inorg. Chem., 43, 3180-3188
(2004).
140.
Y. S. Tan, A. L. Sudlow, K. C. Molloy, Y. Morishima, K. Fujisawa, W. J.
Jackson, W. Henderson, S. N. B. A. Halim, S. Weng Ng and E. R. T.
Tiekink, Cryst. Growth Des., 13, 3046-3056 (2013).
141.
C. Airoldi, S. F. de Oliveira, S. G. Ruggiero and J. R. Lechat, Inorg. Chim.
Acta, 174, 103-108 (1990).
142.
M. A. Malik, T. Saeed and P. O'Brien, Polyhedron, 12, 1533-1538 (1993).
143.
(a) P. O'Brien, J. R. Walsh, I. M. Watson, M. Motevalli and L. Henriksen, J.
Chem. Soc., Dalton Trans., 2491-2496 (1996).
(b) K. W. Seo, S. H. Yoon, S. S. Lee and W. Shim, Bull. Korean Chem. Soc.,
26, 1582-1584 (2005).
144.
A. V. Ivanov, A. V. Gerasimenko, A. A. Konzelko, M. A. Ivanov, O. N.
Antzutkin and W. Forsling, Inorg. Chim. Acta, 359, 3855-3864 (2006).
254
REFERENCES
145.
D. V. Konarev, S. S. Khasanov, A. Otsuka, H. Yamochi, G. Saito and R. N.
Lyubovskaya, Inorg. Chem., 51, 3420-3426 (2012).
146.
N. Srinivasan, P. J. Rani and S. Thirumaran, J. Coord. Chem., 62, 1271-1277
(2009).
147.
N. Awang, I. Baba, B. M. Yamin and A. A. Halim, World Appl. Sci. J., 12,
1568-1574 ( 2011).
148.
T. A. Rodina, A. V. Ivanov, A. V. Gerasimenko, M. A. Ivanov, A. S. Zaeva,
T. S. Philippova and O. N. Antzutkin, Inorg. Chim. Acta, 368, 263-270
(2011).
149.
(a) C. O. Damian and A. A. Peter, Int. J. Mol. Sci., 12, 1964-1978 (2011).
(b) ibid, Int. J. Mol. Sci., 13, 9502-9513 (2012).
150.
(a) A. M. Bond, R. Colton, M. L. Dillon, J. E. Moir and D. R. Page, Inorg.
Chem., 23, 2883-2891 (1984).
(b) J. R. Botelho, C. D. Pinheiro, A. D. Gondim, P. O. Dunstan, I. M. G.
Santos and A. G. Souza, J. Chem. Eng. Data, 56, 2743-2745 (2011).
151.
M. J. Cox and E. R. T. Tiekink, Z. Kristallogr., 214, 571-579 (1999).
152.
C. S. Chian and E. R. T. Tiekink, Appl. Organometal. Chem., 18, 104 (2004).
153.
Q. Jie and E. R. T. Tiekink, Main Group Met. Chem., 25, 317-318 (2002).
154.
S. L. Chian and E. R. T. Tiekink, Appl. Organometal. Chem., 17, 143 (2003).
155.
S. V. Larionov, V. N. Kirichenko, S. M. Zemskova and I. M. Oglezneva,
Koordinats Khim., 16, 79-84 (1990).
156.
R. F. Klevtsova, L. A. Glinskaya, S. M. Zemskova, and S. V. Larionov, J.
Structural Chemistry, 43, 322-329, (2002).
157.
(a) R. C. Mehrotra, G. Srivastava and B. P. S. Chauhan, Coord. Chem. Rev.,
55, 207-259 (1984).
(b) U. N. Tripathi, R. Bohra, G. Srivastava and R. C. Mehrotra, Polyhedron,
11, 1187-1194 (1992).
(c) U. N. Tripathi, G. Srivastava and R. C. Mehrotra, Trans. Met. Chem., 19,
564-566 (1994).
(d) C. Glidewell, Inorg. Chim. Acta, 25, 159-163 (1977).
158.
(a) M. Becchi, F. Perret, B. Carraze, J. F. Beziau and J. P. Michel, J.
Chromatogr. A, 905, 207-222 (2001).
255
REFERENCES
(b) O. P. Singh, A. Chaturvedi, R. K. Mehrotra and G. Srivastava,
Phosphorus, Sulfur Silicon Relat. Elem., 82, 31-37 (1993).
159.
(a) P. G. Harrison, M. J. Begley, T. Kikabhai and F. Killer, J. Chem. Soc.,
Dalton. Trans., 5, 925-928 (1986).
(b) ibid, J. Chem. Soc., Dalton. Trans., 5, 929-938 (1986).
160.
(a) W. B. Welte and E. R. T. Tiekink, Acta Crystallogr., 63, 790-792 (2007).
(b) C. S. Lai, S. Liu and E. R. T. Tiekink, Cryst. Eng. Comm., 6, 221-226
(2004).
161.
S. Kour, B. Gupta, R. Chander and S. K. Pandey, Main Group Met. Chem.,
32, 195-202 (2009).
162.
S. L. Lawton and G. T. Kokotxilo, Inorg. Chem., 8, 2410-2421 (1969).
163.
O. P. Singh, A. Chaturvedi, R. K. Mehrotra and G. Srivastava, Phosphorus,
Sulfur Silicon Relat. Elem., 82, 31-37 (1993).
164.
A. V. Ivanov, O. V. Loseva, M. A. Ivanov, V. A. Konfederatov, A. V.
Gerasimenko, O. N. Antzutkin and W. Forsling, Russ. J. Inorg. Chem., 52,
1595-1602 (2007).
165.
X. Bina, W. Yan-Mei, Z. Li-Ke, W. Juna, L. Yu-Longa and L. Xiao, Chinese
J. Struct. Chem., 32, 1457-1464 (2013).
166.
J. S. Casas, A. Castineiras, M. S. Garcia-Tasende, A. Sanchez, J. Sordo and
E. M. Vazquez-Lopez, Polyhedron, 14, 2055-2058 (1995).
167.
S. L. Chian and E. R. T. Tiekink, Cryst. Eng. Comm., 6, 593-605 (2004).
168.
A. V. Ivanov, A. V. Gerasimenko, O. N. Antzutkin and W. Forsling, Inorg.
Chim. Acta, 358, 2585-2594 (2005).
169.
C. S. Lai and E. R. T. Tiekink, Z. Kristallogr., 221, 288-293 (2006).
170.
T. Li, Zhi-Hua Li, Sheng-Min Hu and Shao-Wu Du, J. Coord. Chem., 59,
945-952 (2006).
171.
C. S. Lai and E. R.T. Tiekink, J. Mol. Struct., 796, 114-118 (2006).
172.
I. Haiduc, Coord. Chem. Rev., 158, 325-328 (1997).
173.
I. Haiduc, D. B. Sowerby and S.-F. Lu, Polyhedron, 14, 3389-3472 (1995).
174.
I. Haiduc and D. B. Sowerby, Polyhedron, 15, 2469-2521 (1996).
175.
S. K. Srivastava, S. Jain and S. B. Saxena, Synth. React. Inorg. Met.-Org.
Nano. Met. Chem., 28, 1431-1444 (1998).
256
REFERENCES
176.
J. S. Casas, E. E. Castellano, J. Ellena, I. Haiduc, A. Sanchez and J. Sordo, J.
Chem. Crystallogr., 29, 831-836 (1999).
177.
M. Taş, M. Yagan, H. Batı, B. Batı and O. Buyukgungor, Phosphorus, Sulfur
Silicon Relat. Elem., 185, 242-248, (2010).
178.
H. P. Fang and C. W. Yi, Acta Chim. Sinica, 22, 478-484 (1956), Chem.
Abstr., 6, 661 (1956).
179.
E. M. Vazquez-Lopez, A. Castineiras, A. Sanchez, J. S. Casas and J. Sordo,
J. Cryst. Spectrosc., 22, 403-409, (1992).
180.
I. Gomez, Anales Soc. Espan. Fis. Quim., 14, 91-102 (1916); Chem. Abstr.,
12, 584 (1918).
181.
G. Bulmer and F. G. Mann, J. Chem. Soc., 666-686 (1945).
182.
S. M. Gurvich and R. Y. Belova, Zh. Obshch. Khim., 31, 1631-1635 (1961);
Chem. Abstr., 55, 222129 (1961).
183.
H. W. Chen, Ph.D. Thesis, Case Western Reserve University (1977).
184.
Jr. J. P. Fackler, D. P. Schussler and H. W. Chen, Synth. React. Inorg. Met.Org. Nano. Met. Chem., 8, 27-42 (1978).
185.
C. G. Overberger and A. E. Borchert, J. Am. Chem. Soc., 82, 4896-4899
(1960).
186.
P. V. Laakso, Suomon Kemistilehti, 13 B, 8, (1940); Chem. Abstr., 34, 5059
(1940).
187.
L. I. Victoriano and H. B. Cortes, J. Coord. Chem., 39, 231-231 (1996).
188.
W. Mellert, E. Amtmann, V. Erfle and G. Sauer, AIDS Res. Hum.
Retroviruses, Mary Ann Liebert, Inc., 4, 71-81 (1988).
189.
(a) G. Winter, Rev. Inorg, Chem., 2, 253-342 (1980).
(b) E. R. T. Tiekink and G. Winter, Rev. Inorg, Chem., 12, 183-302 (1992).
(c) B. F. Hoskins and C. D. Pannan, J. Chem. Soc., Chem. Commun., 408409 (1975).
(d) D. Dakternieks, R. D. Giacomo, R. W. Gable and B. F. Hoskins, J. Am.
Chem. Soc., 110, 6753-6762 (1988).
190.
J. S. Casas, A. Castineiras, I. Haiduc, A. Sanchez, R. F. Semeniuc and J.
Sordo, J. Mol. Struct., 656, 225-230 (2003).
257
REFERENCES
191.
C. A. Bunton, J. E. Salame and L. Seulveda, J. Org. Chem., 39, 3128-3132
(1974).
192.
V. G. Bessergenev, V. I. Belyi and A. A. Rastorguev, Thin Solid Films, 279,
135-139 (1996).
193.
V. G. Bessergenev, E. N. Ivanova and Y. A. Kovalevskaya, Mater. Res.
Bull., 30, 1393-1400 (1995).
194.
R. F. Klevtsova, T. G. Leonova, S. V. Larionov and L. A. Glinskaya, J.
Struct. Chem., 43, 132-140 (2002).
195.
S. V. Larionov, L. A. Glinskaya T. G. Leonova and S. V. Larionov, J. Struct.
Chem., 46, 1023-1030 (2005).
196.
X. H. Jiang, W. G. Zhang, Y. Zhong and S. L. Wang, Z. Kristallogr. NCS,
220, 569-570 (2005).
197.
E. R. T. Tiekink, Acta Crystallogr. C, 56, 1176 (2000).
198.
X. H. Jiang, W. G. Zhang, Y. Zhong and S. L. Wang, Molecules, 7, 549-553
(2009).
199.
C. S. Lai, Y. X. Lim, T. C.Yab and E. R. T. Tieknik, Cryst. Eng. Comm., 4,
596-600 (2002).
200.
I. Ara, F. El. Bahij and M. Lachkar, Synth. React. Inorg. Met.-Org. Nano
Met. Chem., 36, 399-406 (2006).
201.
R. F. Klevtsova, T. G. Leonova, L. A. Glinskaya and S. V. Larionov, J.
Struct. Chem., 47, 504-512 (2006).
202.
T. G. Leonova, V. N. Kirichenko and L. A. Glinskaya, Koordinats. Khim.,
23, 590-595 (1997).
203.
L. A. Glinskaya, R. F. Klevtsova, T. G. Leonova and S. V. Larionov, J.
Struct. Chem., 41, 161-165 (2000).
204.
R. F. Klevtsova, L. A. Glinskaya, T. G. Leonova, and S. V. Larionov, J.
Struct. Chem., 42, 244-250 (2001).
205.
R. F. Klevtsova, T. G. Leonova, L. A. Glinskaya and S. V. Larionov, J.
Struct. Chem., 47, 1182-1187 (2006).
206.
J. G. Kang, J. S. Shin, D. H. Cho, Y. K. Jeong, C. Park, S. F. Soh, C. S. Lai
and E. R. T. Tiekink, Crys. Growth Des., 10, 1247-1256 (2010).
207.
K. H. Reddy and P. S. Reddy, Ind. J. Chem., Sect. A, 40, 1118-1120 (2001).
258
REFERENCES
208.
P. S. Nair, T. Radhakrishnan, N. Revaprasadu, G. Kolawole and P. O’Brien,
J. Mater. Chem., 12, 2722-2725 (2002).
209.
J. Rohovec, J. Touskova, J. Tousek, F. Schauer and I. Kuritka, World
Reneweable Congress, 2815-2822 (2011).
210.
E. R. T. Tiekink, Acta Cryst. C, 56, 1176 (2000).
211.
N. G. Spiropulos, E. A. Standley, I. R. Shawa, B. L. Ingalls, B. Diebels, S.
V. Krawczyk, B. F. Gherman, A. M. Arif and E. C. Brown, Inorg. Chim.
Acta, 386, 83-92 (2012).
212.
E. R. T. Tiekink, Acta Chem. Slov., 50, 343-358 (2003).
213.
E. R. T. Tiekink, The Rigaku Journal, 19, 14-24 (2002).
214.
A. M. Hounslow and E. R. T. Tiekink, J. Cryst. Spectrosc., 21, 133-137
(1991).
215.
J. S. Casas, E. E. Castellano, J. Ellena, I. Haiduc, A. Sanchez, R. F.
Semeniuc and J. Sordo, Inorg. Chim. Acta, 329, 71-78 (2002).
216.
(a) A. T. Casey and A. M. Vecchio, J. Coord. Chem., 16, 371-381 (1987).
(b) J. Dyer and L. H. Ehifer; U.S. Patent 3607865, (1971).
217.
A. I. Vogel, “A Text Book of Quantitative Analysis” 4th edition, Longman,
London (1978).
218.
O. L. Harle, U.S. Patent 268131 A, 6 (1954).
219.
B. Gupta, N. Kalgotra, S. Andotra and S. K. Pandey, Monatsh. Chem., 143,
1087-1095 (2012).
220.
(a) N. Kalgotra, B. Gupta, K. Kumar and S. K. Pandey, Phosphorus Sulfur
Silicon Relat. Elem., 187, 364-367 (2012).
(b) S. Andotra, N. Kalgotra, S. K. Pandey, Bioinorg. Chem. and Appl., 2014,
1-12 (2014).
221.
A. A. Mohamed, I. Kani, A. O. Ramirez and Jr. J. P. Fackler, Inorg. Chem.,
43, 3833-3839 (2004).
222.
U. N. Tripathi, A. Chaturvedi, M. S. Singh and R. J. Rao, Phosphorus Sulfur
Silicon Relat. Elem., 122, 167-171 (1997).
223.
U. N. Tripathi and M. S. Singh, Ind. J. Chem. Soc., 760, 360 (1999).
224.
U. N. Tripathi, P. P. Bipin, R. Mirza and A. Chaturvedi, Pol. J. Chem., 73,
1751-1756 (1999).
259
REFERENCES
225.
H. P. S. Chauhan, C. P. Bhasin, G. Srivastava and R. C. Mehrotra,
Phosphorus Sulfur Silicon Relat. Elem., 15, 99-104 (1983).
226.
N. Zohir, B. Mustapha and D. A. Elbaki, J. Min. and Mat. Charac. and Eng.,
8, 469-477 (2009).
227.
A. Walcarius, B. Marouf, A. M. Lamdaouar, K. Chlihi and J. Bessiere,
Langmuir, 22, 1671-1679 (2006).
228.
B. A. Khaskin, Russ. Chem. Rev., 53, 768-782, (1984).
229.
A. N. Shishkov, N. K. Nikolov, A. I. Busev and A. I. Nauch, Tr. Plovdivski,
Univ. Mat. Fiz. Khim. Biol. (Bulgaria), 10, 117, (1972); Chem. Abstr., 78,
83952, (1973).
230.
J. Cheon, H. -K. Kang and J. I. Zink, Coord. Chem. Rev., 200, 1009-1032
(2000).
231.
M. Valli, P. Persson and I. Persson, Acta Chem. Scand., 48, 810-814 (1994).
232.
E. R. Goldman, E. D. Balighian, H. Mattoussi, M. K. Kuno, J. M. Mauro, P.
T. Tran and G. P. Anderson, J. Am. Chem. Soc., 124, 6378-6382 (2002).
233.
H. Mingyong, G. Xiaohu, Z. S. Jack and N. Shuming, Nat. Biotechnol., 19,
631-635 (2001).
234.
J. K. Jaiswal, H. Mattoussi, M. J. Matthew and S. M. Simon, Nat.
Biotechnol., 21, 47-51 (2003).
235.
N. Pradhan, B. Katz and S. Efrima, J. Phys. Chem. B, 107, 13843-13854
(2003).
236.
R. G. Pearson, J. Am. Chem.Soc., 85, 3533-3539 (1963).
237.
X. B. Wang, W. M. Liu, J. C. Hao, X. G. Fu and B. S. Xu, Chem. Lett., 34,
1664-1665 (2005).
238.
M. Gianini, W. R. Caseri, V. Gramlich and U. W. Suter, Inorg. Chim. Acta,
299, 199-208 (2000).
239.
F. A. Cotton and G. Willkinson, “Advance Inorganic Chemistry”, WileyInterscience, New-York, 5th edition (1988).
240.
M. G. Cherian, Environ. Health Perspect., 54, 243-248 (1984).
241.
G. R. Gale, L. M. Atkins, E. M. Walker, A. B. Smith and M. M. Jones, Ann.
Clin. Lab. Sci., 14, 137-145 (1984).
260
REFERENCES
242.
L. A. Shinobu, S. G. Jones and M. M. Jones, Acta Pharmocol. Toxicol., 54,
189-194 (1984).
243.
M. Altaf, H. Stoeckli-Evans, S. S. Batool, A. A. Isab, S. Ahmad, M. Saleem,
S. A. Awan and M. A. Shaheen, J. Coord. Chem., 63, 1176-1185 (2010).
244.
D. Barreca, A. Gasparotto, C. Maragno, R. Seraglia, E. Tondello, A. Venzo1,
V. Krishnan and H. Bertagnolli, Appl. Organometal. Chem., 19, 59-67
(2005).
245.
E. R. T. Tiekink, Cryst. Eng. Commun., 5, 101-113 (2003).
246.
S. P. Huang, K. J. Franz, E. H. Arnold, J. Devenyi and R. H. Fish,
Polyhedron, 15, 4241-4254 (1996).
247.
D. Fan, M. Afzaal, M. A. Malik, C. Q. Nguyen, P. O’Brien and P. J.
Thomas, Coord. Chem. Rev., 251, 1878-1888 (2007).
248.
R. Romano and O. L. Alves, Mater. Res. Bull., 41, 376-386 (2006).
249.
F. Bonati and R. Ugo, J. Organometal. Chem., 10, 257-268 (1967).
250.
K. Nakamoto, “Infrared and Raman Spectra of Inorganic Compounds”,
Wiley-Interscience, New York, USA, 4th edition (1986).
251.
G. Socrates, “Infrared Characteristics Group Frequencies”, John Wiley and
Sons Ltd., Great Britain (1980).
252.
D. C. Onwudiwe and P. A. Ajibade, Int. J. Mol. Sci., 12, 1964-1978 (2011).
253.
M. L. Shankaranaryana and C. C. Patel, Canad. J. Chem., 39, 1633-1637
(1961).
254.
G. Rajput, V. Singh, S. K. Singh, L. B. Prasad, M. G. B. Drew and N. Singh,
Eur. J. Inorg. Chem., 1, 3885-3889 (2012).
255.
J. Mendham, R. C. Denny, J. D. Barness, M. Thomas and B. Sivasankar,
“Vogel’s Textbook of Quantitative Chemical Analysis, 6th edition, Pearson
Education, Ltd., (2009).
256.
M. Ito and H. Iwasak, Acta Cryst. B, 35, 2720-2721(1979).
257.
A. Piquette, PhD. Thesis, Western State College of Colorado, Gunnison,
Colorado, 65-100 (2002).
258.
G. Marimuthu, K. Ramalingam and C. Rizzoli, J. Coord. Chem., 66, 699-711
(2013).
261
REFERENCES
259.
F. M-N. Kheiri, C. A. Tsipis, C. L. Tsiamis and G. E. Manoussakis, Can. J.
Chem., 57, 767-772 (1979).
260.
H. P. S. Chauhan, A. Bakshi and S. Bhatiya, Phosphorus, Sulfur Silicon
Relat. Elem., 186, 345-353 (2011).
261.
(a) B. F. Hoskins, E. R. T. Tiekink and G. Winter, Inorg. Chim. Acta, 105,
171-176 (1985).
(b) V. N. Kirichenko, L. A. Glinskaya, R. F. Klevtsova and T. G. Leonova,
J. Struct. Chem., 35, 242-247 (1994).
262.
(a) R. Noyori, Science, 248, 1194-1199 (1990).
(b) M. N Hughes, Coordination compounds in biology, in Comprehensive
Coordination Chemistry, G. Wilkinson, R. D. Gillard and J.A. McCleverty,
Eds., Pergamon Press, Oxford, UK, 6, 541 (1987).
263.
Z. –H. Li, L. -H Li, L. -M. Wu and S. –W. Du, Eur. J. Inorg. Chem., 2009,
752-759 (2009).
264.
W. Clegg, M. R. J. Elsegood, L. J. Farrugia, F. J. Lawlor, N. C. Norman and
A. J. Scott, J. Chem. Soc., Dalton Trans., 2129-2135 (1995).
265.
T. Mirkovic, M. A. Hines, P. Sreekumari Nair and G. D. Scholes, Chem.
Mater., 17, 3451-3456 (2005).
266.
D. A. Chowdhury, T. Ogata, S. Kamata and K. Ohashi, Anal. Chem., 68,
366-370 (1996).
267.
A. T. Casey and A. M. Vecchio, J. Coord. Chem., 16, 371-381 (1987).
268.
R. Y. Saleh and D. K. Straub, Inorg. Chem., 13, 1559-1562 (1974).
269.
A. Syed and S. K. Pandey, Monatsh. Chem., 144, 1129-1140 (2013).
270.
R. G. Xiong, Zh. Yu, C. M. Liu and X. Z. You, Polyhedron, 16, 2667-2670
(1997).
271.
R.W. Gable, B.F. Hoskins and G. Winter, Inorg. Chim. Acta, 96, 151-159
(1985).
272.
P. Ch. Reddy and B. J. Rangamannar, Radioanal. Nucl. Chem., 213, 9-19
(1996).
273.
P. Ch. Reddy and B. J. Rangamannar, Radioanal. Nucl. Chem., 214, 159-174
(1996).
274.
N. Wolf and D. M. Roundhill, Polyhedron, 13, 2801-2808 (1994).
262
REFERENCES
275.
X. H. Jiang, W. G. Zhang, Y. Zhong and S. L. Wang, Molecules, 7, 549-553
(2002).
276.
J. Rohovec, J. Touskova, J. Tousek, F. Schauer and I. Kuritka, Photovoltaic
Technology, World Renewable Energy Congress, Sweden, 2815-2822
(2011).
277.
M. R. Hunt, A. G. Kruger, L. Smith and G. Winter, Aust. J. Chem., 24, 53-57
(1971).
278.
T. Li, Z. -H. Li, S. -M. Hu and S. -W. Du., J. Coord. Chem., 59, 945-952
(2006).
279.
M. Sonmez, Turk. J. Chem., 25, 181-185 (2001).
280.
D. Chen, C. S. Lai and E. R. T. Tiekink, Appl. Organometal. Chem., 17, 247248 (2003).
281.
S. B. Kalia, G. Kaushal, M. Kumar, S. Kumar and K. L. Khanduja, Ind. J.
Chem., Sect A, 47, 1323-1332 (2008).
282.
J. P. Fackler, L. D. Thompson, I. J. B. Lin, T. A. Stephenson, R. O. Gould, J.
M. C. Alison and A. J. F. Fraser, Inorg. Chem., 21, 2397-2403 (1982).
283.
U. N. Tripathi and M. S. Ahmad, J. Coord. Chem., 59, 1583-1590 (2006).
284.
U. N. Tripathi, R. Bohra, G. Srivastava and R. C. Mehrotra, Polyhedron,
11, 1187-1194 (1992).
285.
N. A. A. Wahab, I. Baba, M. I. M. Tahir and E. R. T. Tiekink, Acta
Crystallogr., Sect. E, 67, 553-554 (2011).
286.
K. Ramalingam, S. Uma, C. Rizzoli and G. Marimuth, J. Coord. Chem., 63,
4123-4135 (2010).
287.
S. Wakamori, T. Tsuchidate and Y. Ishii, Agr. Biol. Chem., 33, 1682-1690
(1969).
288.
N. Donoghue, E. R. T. Tiekink and L. Webster, Appl. Organomet. Chem., 7,
109-117 (1993).
289.
P. R. Modiya and C. N. Patel, Org. Med. Chem. Let., 2, 1-10 (2012).
290.
G. Sauer, E. Amtmann, K. Melber, A. Knapp, K. Muller, K. Hummelt and A.
Schermt, Proc. Natl. Acad. Sci. USA, 81, 3263-3267 (1984).
291.
N. Raman, J. Joseph, A. Sakthivel and R. Jeyamurugan, J. Chil. Chem. Soc.,
54, 354-357 (2009).
263
REFERENCES
292.
D. Beyersmann and H. Haase, BioMetals, 14, 331-341 (2001).
293.
P. D. Zalewski, S. H. Millard, I. J. Forbes, O. Kapaniris, A. Slavotinek, W.
H. Betts, A. D. Ward, S. F. Lincoln and I. Mahadevan, J. Histochem.
Cytochem., 42, 877-884 (1994).
294.
D. W. Choi and J. Y. Koh, Annu. Rev. Neurosci., 21, 347-375 (1998).
295.
J. M. Lee, G. J. Zipfel, K. H. Park, Y. Y. He, C. Y. Hsu and D. W. Choi,
Neuroscience, 115, 871-878 (2002).
296.
G. Danscher, K. B. Jensen, C. J. Frederickson, K. Kemp, A. Andreasen, S.
Juhl, M. Stoltenberg and R. Ravid, J. Neurosci. Methods, 76, 53-59 (1997).
297.
I. Kim, C. H. Kim, J. H. Kim, J. Lee, J. J. Choi, Z. A. Chen, M. G. Lee, K. C.
Chung, C. Y. Hsu and Y. S. Ahna, Exp. Cell Res., 298, 229-238 (2004).
298.
L. Jarup and T. Alfven, BioMetals, 17, 505-509 (2004).
299.
L. Jarup, T. Bellander, C. Hogstedt and G. Spang, Occup. Environ. Med., 55,
755-759 (1998).
300.
M. M. Jones and M. G. Cherian, Toxicology, 62, 1-25 (1990).
301.
H. Cesur, Turk. J. Chem., 27, 307-314 (2003).
302.
M. Zhukalin, M. K. Blanksma, T. D. Silva, S. W. Suyehira, W. A. Harvey, S.
J. Heggland and P. R. Craig, BioMetals, 20, 61-72 (2007).
303.
M. Prodana, A. Murariu, A. Meghea and I. Demetrescu, Mater. Res. Innov.,
13, 409-412 (2009).
304.
V. L. Dresslera, F. G. Antesa, C. M. Moreiraa, D. Pozebonb and F. A.
Duartec, Int. J. Mass Spectrom., 307, 149-162 (2011).
305.
N. Raman, A. Kulandaisamy and K. Jayasubramanian, Polish J. Chem., 76,
1085-1094 (2002).
306.
B. G. Tweedy, Phytopathology, 55, 910-914 (1964).
307.
I. Pal, F. Basuli, and S. Bhattacharya, Proc. Indian Acad. Sci.: Chem. Sci., 4,
255–268 (2002).
308.
Y. Anjaneyula and R. P. Rao, Synth. React. Inorg. Met.-Org. Chem., 16,
257-272 (1986).
309.
Z. H. Chohan, M. Arif, M. A. Akhtar and C. T. Supuran, Bioinorg. Chem.
and Appl., 2006, 1-13 (2006).
264
REFERENCES
310.
Z. H. Chohan, A. Scozzafava and C. T. Supuran, J. Enzym. Inhib. Med.
Chem., 3, 259-263 (2003).
311.
K. S. Prasad, L. S. Kumar, S. C. Shekar, M. Prasad and H. D.
Revanasiddappa, Chem. Sci. J., 12, 1-10 (2011).
312.
T. D. Thangadurai and K. Natarajan, Trans. Met. Chem., 4-5, 500-504
(2001).
313.
N. Dharmaraj, P. Viswanathamurthi and K. Natarajan, Trans. Met. Chem., 12,105-109 (2001).
314.
A. Spath and K. Tempel, Chem. Biol. Interact., 64, 151-166 (1987).
315.
L. Saghatforoush, H. A. Rudbari, F. Nicolo, P. Asgari, F. Chalabian, M.
Hasanzadeh and V. Panahiazar, Acta Chim. Slov., 60, 300-309 (2013).
316.
S. Hemaiswarya, A. K. Kruthiventi and M. Doble, Phytomedicine, 15, 639652 (2008).
317.
C. I. Yeo, J. H. Sim, C. H. Khoo, Z. J. Goh, K. P. Ang, Y. K. Cheah, Z. A.
Fairuz, S. N. B. A. Halim, S. W. Ng, H. L. Seng and E. R. T. Tiekink, Gold
Bull, 46, 145-152 (2013).
318.
P. Skehan, R. Storeng, D. Scudiero, A. Monks, J. McMahon, D. Vistica, J. T.
Warren, H. Bokesch, S. Kenney and M. R. Boyd, J. Natl. Cancer Inst., 82,
1107-1112 (1990).
265
LIST OF PUBLICATIONS
1. N. Kalgotra, B. Gupta, K. Kumar and S. K. Pandey, O-Tolyldithiocarbonate
complexes of iron(II) and iron(III), Phosph. Sulfur and Silicon and the Related
Elements, 187, 364 (2012).
2. B. Gupta, N. Kalgotra,
S. Andotra, S. K. Pandey, O-Tolyl/benzyl
dithiocarbonates of phosphorus(III) and (V): Syntheses and characterization,
Monateshefte Fur Chemie-Chemical Monthly, 143,1087 (2012).
3. N. Kalgotra, B. Gupta, S. Andotra, S. Kumar and S. K. Pandey, Synthesis,
Spectral, Thermal, Electrochemical, and Biocidal Activity of Tolyl/Benzyl
Dithiocarbonates of Zinc(II), International Journal of Inorganic Chemistry,
2013, 1 (2013).
4. S. Andotra, N. Kalgotra and S. K. Pandey, Syntheses, characterization,
thermal
and
antimicrobial
studies
of
lanthanum(III)
tolyl/benzyldithiocarbonates, Bioinorganic Chemistry and its Application,
2014, 1 (2014).
5. B. Gupta, D. Kumar, N. Kalgotra, S. Andotra, G. Kour, V. K. Gupta, R. Kant
and
S.
K.
Pandey,
Dialkyltin(IV)bis(O–tolyl/benzyldithiocarbonate)
complexes: Spectroscopic, thermogravimetric, antifungal studies and crystal
structure of n–Bu2Sn(S2COCH2C6H5), Journal of Coordination Chemistry,
(under communication).