http://www.e-journals.net
ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
2010, 7(S1), S594-S600
Synthesis, Spectral and Magnetic
Studies of Newly Mixed-Ligand Complexes
of 4-Formyl-Acetanilide Thiosemicarbazone and
3,4-Dihydrocinnamic Acid with Some Metal Ions
SHAYMA A. SHAKER
Department of Engineering Sciences and Mathematics
College of Engineering, Universiti Tenaga Nasional
43009 Kajang, Selangor, Malaysia
[email protected]
Received 30 March 2010; Accepted 25 May 2010
Abstract: New complexes with thiosemicarbazone derivative and 3, 4dihydrocinnamic acid were prepared and characterized by elemental analysis,
determination of metal, IR, 1H NMR, electronic spectroscopy and magnetic
measurements. The thiosemicarbazone derivative forms bidentate ligand
complexes of the general formula, [M(Thz)(Caf)] where Thz = 4-formylacetanilide thiosemicarbazone, Caf = 3,4-dihydrocinnamic acid and M=Mn2+,
Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Pb2+. The IR and 1H NMR spectra
indicates that the (Thz) was coordinated with the metal ions through the N and S
atoms and the (Caf) was negatively charged bidentat ligand and was coordinated
with the metal ions through the two O atoms. Electronic spectra and magnetic
susceptibility measurements of the solid complexes indicates the tetrahedral
geometry around the Mn2+, Fe2+, Co2+, Ni2+, Zn2+, Cd2+ and irregular tetrahedral
geometry around Pb2+ ion while the Cu2+ complex has squar planer geometry.
Keywords: 4-Formyl-acetanilide thiosemicarbazone complexes, Mixed-ligand complexes,
3,4-Dihydrocinnamic acid complexes, Caffeic acid complexes.
Introduction
Thiosemicarbazone is an important class of compound containing both hard (N) and soft (S)
donors ligands1,2. The ligand and most of their complexes were found to remarkably exhibit
activity against some plant pathogenic fungi3. Moreover, it shows marked and selective
antitumor, antiviral, antimalarial activities4,5. Thus, thiosemicarbazone derivatives and their
metal complexes have shown significant anticancer activity2,6.
Synthesis, Spectral and Magnetic Studies
S595
Furthermore, there are many examples of biological importance of thiosemicarbazone
derivatives such as thiacetazone which is used in the clinical treatment of tuberculosis7.
This ligand has also potential biological activity and has been shown to display
radiation protective and bacteriostatic activities8. Thiacetazone was shown
magnificently antimicrobial and used for treatment of tuberculosis. This ligand was used
as a drug against mycobacterium tuberculosis and found to be very useful in
combination with isoniazid 9. As part of ongoing study of thiosemicarbazone derivatives,
it is reported herein the synthesis and characterization of some mixed ligand of Mn2+,
Fe2+, Co 2+, Ni2+, Cu2+, Zn2+, Cd 2+ and Pb 2+ complexes with two different donor ligands
and shed some lights on the coordination properties of both of the 4-formyl- acetanilide
thiosemicarbazone and 3,4-dihydrocinnamic acid complexes with metal ions.
Experimental
All chemicals were obtained from commercial sources and were used without further
purifications (MnCl2.2H2O, FeCl2.4H2O, CoCl2.6H2O, NiCl2.6H2O, CuCl2.2H2O, ZnCl2,
CdCl2. H2O, Pb(NO3)2 and KOH) from Merck. 4-Formyl-acetanilide thiosemicarbazone and
3,4-dihydrocinnamic acid were obtained from Sigma. methanol, ethanol, DMSO and
DMSO-d6 were provided by BDH.
UV-Visible spectra were measured in dimethylsulfoxide (DMSO) using a Shimadzu
UV-2450 UV-Vis spectrophotometer. The IR spectra in the range of 4000-200 cm-1
were recorded as CsI disc on a Shimadzu FTIR-8300 Fourier Transform infrared
spectrophotometer. Determinations for metals were carried out using atomic absorption
spectrometer A-Analysis 800 Perkin Elmer. Elemental analysis (C, H, N, S) was
performed on a Perkin Elmer B-240 Elemental Analyzer. 1H NMR spectra were
recorded using the JEOL JNM-ECP 400 Spectrometer in DMSO-d 6, relative to the
internal standard tetramethylsilane (TMS). Conductivity measurements were carried out
at 25 oC in DMSO using a Philips Pw-9526 digital conductivity meter. Melting points
were determined using a Digital Melting Point Apparatus. The magnetic susceptibility
measurements were eventually obtained using a Magnetic Susceptibility Balance, Model
MsB-MK1.
Synthesis of metal complexes
All the complexes were prepared by the same general method, an ethanolic solution 13 mL
of 4-formyl-acetanilide thiosemicarbazone (Thz) (0.178-0.433 g) and an KOH ethanolic
solution 15 mL of 3,4-dihydrocinnamic acid (Caf) (0.135-0.330 g) were added subsequently
to an aqueous solution of metal salts. The mixture was heated on water bath for 15 minutes
with constant stirring and then the formed products were filtered off, washed and
recrystallized with mixture of (1:3) water: ethanol and dried at 60 oC.
Results and Discussion
The reaction of metal salts with the Thz and caf gave complexes of the general formula
[M(Thz)(Caf)] where M = Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd 2+ and Pb 2+, Thz = 4formyl-acetanilide thiosemicarbazone and Caf=3,4-dihydrocinnamic acid. Table 1
shows the colors, elemental analysis and molar conductivity for these complexes. The
complexes have melting point above 215 oC and these complexes are generally soluble
in DMSO. The molar conductance values are very low, therefore all the complexes are
considered to be non-electrolyte except the Cu2+ complex because the molar
conductivity is high1,10.
S596
SHAYMA A. SHAKER
Table 1. Elemental analysis and some physical properties of the prepared complexes
Compound
Color
M.P.
o
C
Elemental analysis calc, (found )%
C
Brown 254- 48.616
yellow 256 (48.02)
Dark
48.522
[Fe(Thz)(Caf)]
>300
green
(47.115)
Green- 253- 48.206
[Co(Thz)(Caf)]
yellow 255 (47.96)
Dark 244- 48.230
[Ni(Thz)(Caf)]
green 245 (48.641)
Dark 215- 47.741
[Cu(Thz)(Caf)]Cl
green 217 (47.60)
250- 47.558
[Zn(Thz)(Caf)] White
252 (46.122)
250- 43.313
[Cd(Thz)(Caf)] White
251 (42.20)
288- 36.708
[Pb(Thz)(Caf)] White
290 (35.60)
[Mn(Thz)(Caf)]
H
N
S
M
Molar
conductivity
Ohm-1cm2mol-1
3.861 11.936 6.831 11.70
(3.251) (10.303) (5.421) (11)
3.4
3.854 11.913 6.818 11.87
(3.953) (11.522) (6.345) (10.9)
3.6
3.829 11.835 6.773 12.44
(3.521) (10.303) (6.391) (11.51)
3.2
3.831 11.841 6.777 12.40
(3.20) (10.641) (5.401) (12.19)
4
3.792 11.721 6.708 13.29
(2.11) (11.261) (5.101) (12.89)
23.2
3.777 11.676 6.682 13.62
(2.641) (10.532) (6.456) (13.40)
3
3.440 10.633 6.086 21.33
(3.313) (9.512) (5.90) (20)
7.4
2.915 9.012 5.158 33.33
(2.10) (8.103) (4.123) (32.91)
5.25
The infrared spectra studies
The infrared spectrum of Thz shows strong band at 3160 cm-1 which is attributed to ν(NH).
The possibility of thion-thiol tautomerism (H-N-C=S) (C=N-SH) in this ligand has been
ruled out because there are no bands around 2500-2700 cm-1. Moreover, the ligand has very
strong bands in 1668 cm-1 and 1606 cm-1 which are due to the ν(C=O) and ν(C=C)
respectively. Furthermore, the ν(C=N) band of thiosemicarbazone was observed at 1583 cm-1
and this band was shifted to lower frequencies by 63-16 cm-1 in the spectra of the complexes,
this is indicating the coordination of the imine N1. Thus, the spectrum of the ligand shows
ν(CS) in 830 cm-1, so this band was shifted to the lower frequencies by 30-5 cm-1 on
coordination of the complexes. Moreover, the spectrum of the complexes showed weak
bands in the region of 418-459 cm-1 and 384-434 cm-1 which are attributed to ν(M-N) and
ν(M-S) respectively and this is supporting the coordination of the ligand as bidentate NS
cleating agents10,11.
The spectrum of the free ligand Caf shows strong band at 1620 cm-1 which is assigned to
ν(COOH), this band appeared in complexes without any shifted. This indicates that the
carboxylate group remains without coordination with the metal ions. Furthermore, the
spectrum also shows very strong band at 3435 cm-1 which is due to ν(OH), this band
disappeared in complexes. Thus, the band at 1218 cm-1 which is attributed to the ν(C-O) was
shifted to the lower frequencies by 98-42 cm-1 in complexation. Moreover, the complexes
exhibited weak bands between 524-585 cm-1 which are due to ν(M-O). This indicates that
the 3,4-dihydrocinnamic acid which is coordinated with the metal ions through the two of
the O atoms12-15. All the characteristic vibrations and assignments of the free ligands and
their complexes are listed in Table 2.
Synthesis, Spectral and Magnetic Studies
S597
Table 2. The IR spectral bands (cm-1) of the free ligands and their complexes
Compound
ν(OH)
Thz
Caf
3435
[Mn(Thz)(Caf)]
[Fe(Thz)(Caf)]
[Co(Thz)(Caf)]
[Ni(Thz)(Caf)]
[Cu(Thz)(Caf)]Cl
[Zn(Thz)(Caf)]
[Cd(Thz)(Caf)]
[Pb(Thz)(Caf)]
-
ν(NH ν(C=O ν(C=N) ν(C-O) ν(CS)
)
)
3160
1668
1583
830
1218
3160
1667
1580 1173 810
3165
1665
1520 1120 817
3161
1666
1523 1174 810
3162
1665
1523 1175 810
3165
1665
1529 1176 800
3160
1668
1542 1173 810
3157
1671
1567 1175 825
3161
1668
1520 1174 810
ν(M-O)
583, 523
525
583,524
583,524
582
583,524
585,520
583,524
ν(M-N) ν (M-S)
453,434
396
450
400
453,418
396
434,452
394
525
418
453
434
459
395,384
453
434
Electronic spectral studies and magnetic measurements
The UV-Vis spectra of the Thz and Caf have shown that the absorption bands occured at
273,277 nm and 315,300 nm which are attributed to π→π* and n→π* respectively. The
spectrum of Mn2+ d 5 complex indicates that it has tetrahedral geometry. The 6A1→4E(D)
and 6A1→4T 2(D) can be seen at 314 and 330 nm respectively. Moreover, the magnetic
moment of the complex was 4.810 BM which was within the expected spin-only
value16,17. The spectrum of the dark green of Fe2+ complex exhibited absorption band in
the visible region at 528 nm due to the electronic transition of 5E(D) →5T2(D). The value
of µ eff Fe2+ d 6 complex was 4.320 BM which was in agreement with the expected spin
value. All these values confirm that the Fe2+ complex has tetrahedral geometry16,18. The
[Co(Thz)(Caf)] complex adopts a distorted tetrahedral structure with the three bands
which were assigned to 4A2(F) →4T 1(P), 4A2(F) →4T1(F) and 4A2(F) →4T 2(F) as it was
observed at 350,462 and 888 nm respectively. Furthermore, the magnetic moment for
the complex Co 2+ d 7 was found to be 3.401 BM16,19,20. The spectrum of the dark green of
the Ni(II) complex exhibited absorption bands at 286,508 and 853 nm which were
attributed to the 3T1(F) →3A2(F), 3T1(F) →3T1(P) and 3T1(F) →3T 2(F) respectively. Thus, the
higher value of the magnetic moment for Ni2+ d 8 complex was 3.4 BM which was
probably due to the orbital contribution. All these values support the tetrahedral
geometry for the Ni(II) complex21,22. The [Cu(Thz)(Caf)]Cl complex exhibited
absorption band at 288 nm which is expected to be the LMCT S→d and the other bands
at 337, 368 and 386 nm which are assigned to 1A1g→1B 1g, 1A1g→1A2g and 1A1g→Eg
respectively. Nevertheless, these bands were hidden by a strong CT transition.
Therefore, all these rules are accepted for Square planer geometry20. Finally, the
diamagnetic of Zn2+, Cd 2+ and Pb 2+ complexes have absorption bands at 335,336 and
345 nm respectively which are due to the charge transfer M→L. This is because of the
electronic configuration of these complexes which confirmed the absence of any d-d
electronic transition16,23,24. All the data and remarks are found in Table 3.
1
H NMR spectra studies
The 1H NMR spectrum of the Thz shows signal protons at 10 and 11.28 ppm which are
attributed to the NH acetamide and NH hydrazine respectively. The chemical shifts due to
those signal protons remained unchanged in the spectra of Zn2+, Cd2+ and Pb2+ complexes.
This indicates both of the nitrogen of NH acetamide and NH hydrazine are not involved to
S598
SHAYMA A. SHAKER
coordinate with the metal ions. Moreover, the NH2 group due to carbothioamide exhibited
signal proton was splitted to the 7.93 and 7.90 ppm. This signal was appeared at 7.96 and 7.97
ppm on the complexes. Furthermore, the ligand Thz showed signal protons at 8.09 and 2.01
ppm which are attributed to CH of methylene group and CH3 of acetamide group. Thus, the
chemical shifts of the CH aromatic were observed at 7.70, 7.66, 7.60 and 7.52 ppm. The absence of
the signal proton of SH group at 12.10 ppm is further supported the presence of the thione
form of the Thz in the complexes instead of thiole form25,26. All the 1H NMR chemical shifts
(δ, ppm) of free ligand Thz and their complexes are listed in Table 4.
Table 3. The UV-Vis spectra and magnetic moment values of the free ligand and their
complexes
Wave
µ eff Calc.(found)
λmax
εmax
Assignment
BM
nm number cm-1 Lmol-1cm-1
273
36630
746
Thz
π→π*
315
31746
4027
n→π*
Caf
277
36101
685
π→π*
300
33333
1904
n→π*
[Mn(Thz)(Caf)]
294
34013
3960
Charge transfer (C.T)
5.916
6
4027
(4.810)
314
31847
A1→4E(D)
6
4327
330
30303
A1→4T2(D)
4.898
[Fe(Thz)(Caf)]
355
28169
4327
C.T
5
(4.320)
528
18939
129
E(D) →5T2(D)
4
[Co(Thz)(Caf)]
350
28571
3960
A2(F) →4T1(P)
3.872
4
(3.401)
462
21645
44
A2(F) →4T1(F)
4
888
11261
13
A2(F) →4T2(F)
3
[Ni(Thz)(Caf)]
286
34965
4106
2.828
T1(F) →3A2(F)
3
(3.4)
508
19685
13
T1(F) →3T1(P)
3
3
853
11723
24
T1(F) → T2(F)
[Cu(Thz)(Caf)]Cl 288
diamagnetic
34722
3960
LMCT S→d
1
337
29673
1236
A1g→1B1g
1
368
27173
3630
A1g→1A2g
1
3852
386
25906
A1g→1Eg
[Zn(Thz)(Caf)]
1269
diamagnetic
335
29850
CT M→L
[Cd(Thz)(Caf)]
1158
336
29761
diamagnetic
CT M→L
[Pb(Thz)(Caf)]
1210
345
28985
diamagnetic
CT M→L
1
Table 4. H NMR signals of the free ligand and its complexes in DMSO-d6
Compound
Compound
Thz
[Zn(Thz)(Caf)]
[Cd(Thz)(Caf)]
[Pb(Thz)(Caf)]
NHace
10.00
10.15
10.12
10.14
NHhyd
11.28
11.31
11.30
11.30
NH2 car
7.93, 7.90
7.96
7.97
7.97
CHme
8.09
8.06
8.04
8.05
CHaro
7.70,7.66,7.60,7.52
7.71,7.69,7.60,7.58
7.68,7.65,7.58,7.56
7.71,7.68,7.60,7.58
CH3 ace
2.01
2.04
2.03
2.03
ace=acetamide, hyd=hydrazine, car=carbothioamide, me=methylene and aro=aromatic
The spectrum of the ligand Caf in DMSO-d6 shows five signal protons of hydrogen at: δ
6.93(H1), 6.87(H2), 6.60(H3), 7.12(H4) and 6.15(H5). When Caf was complexed with Zn2+, Cd2+
and Pb2+ all these signal protons were desheilded downfield for aromatic protons H2, H3 and H4,
which are highly hydrophobic and corresponding to the benzene ring and portion of ethylene27.
Synthesis, Spectral and Magnetic Studies
S599
Furthermore, the spectrum of Caf exhibited two signal protons at 8.40 and 8.19 ppm which are
attributed to two groups of OH. These signal protons were disappeared in complexes which may
indicate that the Caf was coordinated with the Zn2+, Cd2+ and Pb2+ through the two O atoms28. The
1
H NMR chemical shift values of free ligand Caf and their complexes are reported in Table 5.
Table 5. 1H NMR chemical shifts (δ, ppm) of the free ligand and its complexes
Compound
H1
H2
H3
H4
H5
Caf
6.93
6.87
6.60
7.12
6.15
[Zn(Thz)(Caf)]
6.97
6.88
6.73
7.15
6.22
[Cd(Thz)(Caf)]
6.95
6.86
6.71
7.15
6.18
[Pb(Thz)(Caf)]
6.97
6.88
6.73
7.14
6.22
Conclusion
A newly synthesized mixed ligand complexes of 4-formyl-acetanilide thiosemicarbazone and
3,4-dihydrocinnamic acid with some metal ions is presented in this article. All the complexes
were non-electrolyte in DMSO except the Cu2+ complex was electrolyte because of its high
molar conductivity. The Thz and Caf behave as a bidentate ligand with the metal ions. The IR
spectra suggested that the Thz was coordinated with the metal ions through the N and S atoms
and the Caf ligand was coordinated with the metal ions through the two O atoms. The electronic
spectra and magnetic moments have suggested that the Mn2+, Fe2+, Co2+, Ni2+, Zn2+ and Cd2+
complexes have tetrahedral geometry as can be seen in Figure 1. The Cu2+ complex has square
planer geometry. The Pb2+ complex has irregular tetrahedral can be seen in Figure 2.
H
H
C
1
N
N
2
O
CH3
4
3 NH2
C
S
N
M
H
O
O
1
2+
2+
+22+
MM=Mn
= Mn+2
, Fe
Fe+2
Co+22+,,Ni
Ni+22+, ,Zn
Zn+22+and
andCdCd
,, Co
O
3
2
4
HO
5
Figure 1. Suggested structure of [M(Thz)(Caf)] complexes
H
C
H
4
N
1
3
2
N
O
CH3
NH2
C
S
N
Pb
H
O
O
1
2
3
4
O
OH
5
Figure 2. Suggested structure of [Pb(Thz)(Caf)] complex
S600
SHAYMA A. SHAKER
Acknowledgment
The author would sincerely like to thank the Chemistry Department of College of Science,
Al-Mousel University, Iraq for their technical assistance. Additional thanks are also due to
Dr. Hussein A. Mohammed for his kind assistance.
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