Indian Journal of Chemistry
Vol. 50A, August 2011, pp. 1035-1042
Reactivity of tricine in the presence of Cu(ClO4)2.6H2O and 2,2'-bipyridine:
Synthesis, characterization and magnetic property of the complexes
Vinod Kumar Yadav, Niraj Kumari & Lallan Mishra*
Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221 005, India
Email: [email protected]
Received 1 June 2011, revised and accepted 14 July 2011
Three complexes, [Cu(bpy)(µ-OH)]2·2ClO4 (1) [Cu(H4TRI)(bpy)]ClO4 (2) and [Cu3(bpy)5(µ-O)(NO3)]2·6ClO4 (3)
{H4TRI= tricine, bpy= 2,2'-bipyridine} have been synthesized and characterized using their IR, UV-vis and ESR
spectroscopic data , elemental analysis and single crystal X-ray diffraction studies. The π-π interaction along the a-axis in
complex (1) provides a channel- type structure while similar interaction in complex (2) generates a channel with floating
ClO4- anions. Complex (3) comprises a pair of Cu(II) centers connected via (µ2-O) oxo bridges. These are further linked to
Cu3 and Cu3#1 centers via oxygen atoms of the nitrate anion. The assembled structure of this complex along the c- axis
displays a zig-zag chain formation. The variable temperature magnetic measurement of a representative complex (3),
[Cu3(bpy)5(µ-O)(NO3)]2·6ClO4, shows that two of the Cu(II) centers couple ferromagnetically.
Keywords: Coordination chemistry, Polynuclear complexes, Tricine, Copper, Ferromagnetic interactions
Polynuclear copper(II) complexes display interesting
catalytic and magnetic properties as well as serve as
models of active site structures of several
metalloenzymes1-4. A few high-nuclear Cu(II) clusters
i.e., 5Cu5, 6Cu6, 7Cu7, and 8Cu8,9 have also been
reported. Studies show that anions function not only
in balancing the charge in metal-organic hybrid
species, but also play a crucial role in creating
structural diversity10-14. They form bridges, helical
structures and higher dimension networks. For
example, a chloride anion most of the time acts as a
bridging ligand15,16 but sometimes it is also involved
in the development of organized clusters17. On the
other hand, planar [D3h] anions such as NO3- and
CO32- generate two-dimensional (2D) networks
together with cyclic structures18-21. Tetrahedral anions
like BF4- and ClO4- play a key role in generating three
dimensional (3D) networks22-25.
Keeping these reports in view, tricine (H5TRI) was
selected as an interesting chelating agent owing to
incorporation of carboxylate oxygen, imido nitrogen
and alcoholic oxygen atoms26 in its structural frame.
Among polypyridines, 2,2'-bipyridine (bpy), alphadiimine chelating bidentate ligand, plays a key role in
such synthetic studies. It efficiently provides either
intra- or intermolecular π–π stacking interactions
through its aromatic rings. This feature potentially
contributes towards the stability of polynuclear
structures as well as the formation of extended
supramolecular structures with bridging anionic
ligands27-29. The present article reports the synthesis,
crystal structures, and spectroscopic properties of
three complexes, [Cu(bpy)(µ-OH)]2·2ClO4 (1),
[Cu(H4TRI)(bpy)]·ClO4 (2), and a unique hexanuclear
complex [Cu3(bpy)5(µ-O)(NO3)]2·6ClO4 (3). Studies
on magnetic property of a representative complex (3)
are also reported herein.
Materials and Methods
Reagents of AR grade purchased from standard
commercial sources (Sigma-Aldrich, Merck) were
used without further purification. Elemental analysis
was carried out on a Carbo-Erba elemental analyzer
1108, while IR spectra were recorded as KBr pellets
using a Varian 3100 FT-IR spectrometer. The UV-vis
spectra were recorded in the range 200-700 nm using
Shimadzu UV-1701 spectrophotometer. Magnetic
susceptibility was measured at different temperatures
using Quantum Design Squid magnetometer (model
MPMS). Cyclic voltammetric measurements were
made on a CH instrument (USA) CH1620c
electrochemical analyzer. The precursor complexes of
the type, Cu(L)(NO3)2·H2O (L= 2,2'-bipyridyl), was
prepared using reported procedure30.
1036
INDIAN J CHEM, SEC A, AUGUST 2011
One-pot synthesis of [Cu(bpy)(µ-OH)]2·2ClO4 (1)
[Cu(H4TRI)(bpy)]ClO4 (2)
and
To an alkaline aqueous solution of tricine (0.18 g,
1.0 mmol) containing NaOH (0.12 g, 3.0 mmol)
in H2O (15.0 mL), a methanolic solution of
2,2′-bipyridine (10.0 mL) (bpy) (0.47 g, 3.0 mmol)
and Cu(ClO4)2·6H2O (1.11 g, 3.0 mmol) were added
simultaneously with continuous stirring. The reaction
mixture was then stirred further for 1 h. The solid
product thus obtained was filtered, washed with
distilled water and methanol followed by diethyl
ether. It was recrystallized with DMSO/MeOH (1:2)
mixture and finally dried in vacuo. Crystals suitable
for single crystal X-ray crystallography were obtained
after slow evaporation of its solution in DMF and the
complex was identified as [Cu(bpy)(µ-OH)]2·2ClO4 (1).
Elemental analysis (%) Calcd for C20H16Cl2N4O10Cu2:
C, 35.7; H, 2.6; N, 8.3; Found: C, 35.3; H, 2.2; N, 7.9.
IR (KBr pellet, cm-1): 3428, 1603, 1572, 1086, 900.
UV-vis (DMSO, 10-5M): λmax/(nm)(ε ×105 M-1 cm-1) 302
(0.487), 313 (0.455), 630 (0.105).
The filtrate obtained from the above reaction workup was reduced to half its volume and kept for slow
evaporation. After a few days, X-ray quality crystals
of complex [Cu(H4TRI)(bpy)]ClO4 (2) were obtained.
Elemental analysis (%) Calcd for C16H19ClN3O9Cu:
C, 38.6; H, 4.0; N, 8.4; Found: C, 38.8; H, 3.9; N, 7.8.
IR (KBr pellet, cm-1): 3427, 1625, 1602, 1088.
UV-vis (DMSO, 10-5M): λmax/(nm)(ε×105 M-1 cm-1)
287(0.446), 296(0.418), 312(0.334), 650(0.097).
Synthesis of [Cu3(bpy)5(µ-O)(NO3)]2·6ClO4 (3)
A methanolic solution (10.0 mL) of bipyridine
(0.78 g, 5.0 mmol) and Cu(ClO4)2·6H2O (1.11 g,
3.0 mmol) were added together slowly to an alkaline
solution (15.0 mL) of tricine (0.17 g, 1.0 mmol). After
complete addition, a solid compound was
immediately obtained, which was dissolved in few
drops of dil. HNO3 to give a clear solution. The
reaction mixture was then stirred further for 10 h and
then left as such. After three days, the obtained blue
crystals were filtered and dried in vacuo. The crystals
were identified as [Cu3(bpy)5(µ-O)(NO3)]2·6ClO4 (3).
The filtrate was further left for slow evaporation.
After 10 days, a white crystalline solid was obtained,
which was characterized as unreacted tricine. This
observation indicates that under the present experimental
conditions, tricine did not react with Cu(II) ion.
Elemental analysis (%) Calcd for C100H82Cl6N22O32Cu6:
C, 44.52; H, 3.06; N, 11.42; Found: C, 44.6; H, 2.9; N
11.3. IR data (KBr pellet, cm-1): 1602, 1578, 1527,
1333, 1300, 1083, 654, 535. UV-vis (DMSO, 10-5M):
λmax/(nm) (εmax×105 M-1 cm-1) 288 (1.425), 298 (1.289),
312 (0.996), 635 (0.243), 965 (0.130)
X-ray crystallographic studies
X-ray diffraction data were collected by mounting
a single-crystal of the samples on a glass fiber of
Oxford XCALIBUR-EOS diffractometer. Appropriate
empirical absorption corrections using the programs
multi-scan were applied. Monochromated Mo-Kα
radiation (λ = 0.71073 Å) was used. The crystal
structures were solved by direct methods using
SHELXS-97 program31 and refined by full matrix
least squares SHELXL-9732. Drawings were carried
out using MERCURY33, DIAMOND34, whereas
special computations are carried out using
PLATON35.
Results and Discussion
The complexes were found to be thermally stable
and soluble in DMF and DMSO. The IR spectrum of
complex (1) displayed bands at 3428 cm-1 and
900 cm–1, assigned to µ-OH stretching and bending
vibrations respectively36,37. A band observed at
1625 cm-1 in the spectrum of complex (2) and bands
appearing at 1527 and 1333, 1300 cm-1 in the
spectrum of complex (3) were assigned to ν(COO-) of
tricine38 and uncoordinated N—O and coordinated
N—O vibrations of NO3¯ groups respectively39,40.
The UV-visible spectra of the complexes recorded
in DMSO (10-5 M) are displayed in Fig. 1.
The spectra of the complexes displayed bands at
~280-320 nm assigned to intra ligand charge transfer
Fig. 1UV-vis spectra of complexes (1), (2) and (3) in DMSO
solution (10-5 M).
YADAV et al.: REACTIVITY OF TRICINE IN PRESENCE OF Cu(C1O4)2.6H2O & 2,2′-BIPYRIDINE
1037
transitions41. Normally, a typical square pyramidal
complex displays d-d transition band42-43 between
λmax 550–660 nm. It, thus support the geometry of the
complexes observed from X-ray crystallography. The
band observed at λmax 312 nm in the spectrum of
complex (3) has been assigned to O→Cu(II) charge
transfer transition in consonance with earlier report44.
However, additional peak observed at λmax ~965 nm
supports distorted structures (trigonal bipyramidal and
distorted octahedron)45. Therefore, complex (3)
exhibits square pyramidal, distorted square pyramidal
as well as distorted octahedral geometries around
Cu(II) ions.
The ESR spectra of the complexes, recorded in
solution at room temperature as well as at liquid
nitrogen temperature are depicted in Fig. 2. In
solution (DMSO), at liquid N2 temperature, the
analysis of EPR spectrum of complex (1) showed
g║ = 2.14 and g┴ = 2.01 whereas, complex (2) showed
four parallel lines giving g║ = 2.18, A║ = 80 Gauss and
g┴ = 2.02. In solution (DMSO) at liquid
N2 temperature, analysis of complex (3) also gave
g║ = 2.33, A║ = 100 Gauss, g┴ = 2.01. The axial g
tensor values with g║>g┴ suggests that dx2-y2 is ground
state46 while g0 calculated using the relationship46,
g0=(g║+2g┴)/3 are found as 2.05, 2.07 and 2.11 for
complexes (1), (2) and (3) respectively.
Structural description of complexes
Structure refinement parameters of the complexes
are given in Table 1. The selected bond distances (Å)
and angles (deg.) are tabulated in Table 2, whereas
Fig. 2ESR spectra of complexes (1), (2) and (3) in DMSO solution.
Table 1 Crystallographic data for complexes (1), (2) and (3)
Parameters
(1)
Formula
C20H16Cl2N4O10Cu2
Molecular wt
670.35
Crystal system
Monoclinic
Temp. (K)
293(2)
Space group
C 2/m
a (Å )
13.622
b (Å)
15.1826
c (Å)
6.2702
α (°)
90
β (°)
113.826
γ (°)
90
V (Å3)
1186.3
Z
2
Dc (mg m-3)
1.877
Reflns. collect.
2353
Reflns. unique
1394
R(int)
0.0191
Index ranges
-17 ≤ h ≤ 17; -20 ≤ k ≤ 17; -8 ≤ l ≤ 3
Refinement method: Full-matrix, least squares on F2
wR2
0.0800
R1
0.0345
GoF
0.933
(2)
C16H19ClCuN3O9
496.33
Triclinic
293(2)
P-1
7.8231(16)
9.942(2)
13.074(3)
76.22(3)
80.92(3)
72.46(3)
937.6(3)
2
1.758
6512
4945
0.0998
-10 ≤ h ≤ 6; -13 ≤ k ≤ 13; -17 ≤ l ≤ 16
0.2481
0.0897
1.129
(3)
C100H82Cl8Cu6N22O3
2864.72
Triclinic
293(2)
P-1
13.4643(8)
13.8089(6)
18.0753(9)
103.994(4)
96.901(5)
119.161(5)
2733.0(2)
1
1.741
25964
13459
0.0367
-18 ≤ h ≤ 18; -18 ≤ k ≤ 18; -24 ≤ l ≤ 24
0.1792
0.0638
0.93
1038
INDIAN J CHEM, SEC A, AUGUST 2011
Table 2Selected bond lengths (Å) and bond angles (º) for the complexes (1), (2) and (3)
Complex (1)
Cu(1)-O(1)
Cu(1)-O(1)#1
Cu(1)-N(2)
Complex (2)
Cu(1)-O(1)
Cu(1)-N(1)
Cu(1)-O(3)
Complex (3)
Cu(1) – O(3)
Cu(1) – N(2)
Cu(1) – N(12)
Cu(1) – N(13)
Cu(2) – O(4)
Cu(2) – N(4)
Cu(2) – N(16)
Cu(2) – O(3)
Cu(3) – O(4)
N(15) – O(2)
1.907(2)
1.907(2)
1.984(2)
O(1)-Cu(1)-O(1)#1
O(1)-Cu(1)-N(2)#2
O(1)-Cu(1)-N(2)
82.87(14)
176.59(14)
97.94(9)
N(2)#2-Cu(1)-N(2)
Cu(1)-O(1)-Cu(1)#1
O(1)#1-Cu(1)-N(2)
81.43(12)
97.13(14)
176.59(14)
1.951(4)
2.000(6)
2.361(5)
N(1)-Cu(1)-O(1)
N(1)-Cu(1)-N(2)
N(3)-Cu(1)-O(1)
92.6(2)
81.0(2)
84.4(2)
N(3)-Cu(1)-O(3)
79.26(19)
1.952(4)
2.001(5)
2.019(19)
2.195(5)
2.031(4)
2.090(6)
2.038(5)
2.441(8)
2.310(4)
1.251(7)
O(3)-Cu(1)-N(1)
O(3)-Cu(1)-N(13)
O(3)-Cu(1)-N(2)
O(3)-Cu(1)-N(12)
N(13)-Cu(1)-N(1)
N(13)-Cu(1)-N(12)
N(12)-Cu(1)-N(1)
N(1)-Cu(1)-N(2)
O(4)-Cu(2)-N(3)
O(4)-Cu(2)-N(4)
159.36(19)
98.86(18)
94.3(2)
93.14(18)
101.67(19)
78.2(2)
93.2(2)
80.1(2)
92.55(19)
145.54(18)
N(3)-Cu(2)-N(17)
N(3)-Cu(2)-N(16)
N(4)-Cu(2)-N(16)
N(4)-Cu(2)-N(17)
N(16)-Cu(2)-N(17)
O(1)-Cu(3)-O(4)
O(1)-Cu(3)-N(7)
O(1)#1-Cu(3)-N(8)
O(1)#1-Cu(3)-O(4)
N(7)-Cu(3)-O(4)
92.1(2)
169.1(2)
99.2(2)
92.42(19)
77.1(2)
101.19(16)
166.8(2)
170.2(2)
95.33(16)
91.62(18)
selected parameters for weak interactions are listed in
Table 3.
The complex (1) crystallized in the monoclinic
crystal system with C2/m space group. The
asymmetric unit is shown in Fig. 3. It possesses a
distorted square planar coordination geometry with a
CuN2O2 coordination core around Cu(II) ion. Each
Cu(II) center is surrounded by two nitrogen atoms of
2,2'-bipyridine ring and two oxygen atoms from
bridging hydroxide groups. The Cu-N and Cu-O bond
lengths are comparable with the bond lengths reported
for similar binuclear copper(II) complexes47. The
distance between two copper(II) centers is 2.859 Å
and the Cu(1)-O(1)-Cu(1) bridging angle is
97.13(14)º. These data were found to be consistent
with binuclear Cu(II) complexes bearing µ-hydroxo
group48. The N(2)#2–Cu(1)–N(2) angle is 81.43(12)º
and N(2)-Cu(1)-O(1)# angle is 176.59(14)°,
substantially deviating from ideal square planar
geometry. The dihedral angle between the
N(2)-Cu(1)-O(1) and N(2)#-Cu(1)-O(1)# planes is
~79°. Crystal packing view of complex (1) along
a-axis involves π-π interaction in the range of 3.830 Å
(Supplementary data S1).
The molecular structure of the complex (2) is
shown in Fig. 4. It crystallizes in the triclinic crystal
system with P-1 space group. The copper(II) center
adopts CuN3O2 coordination core in a distorted square
pyramidal geometry. Out of three OH groups and one
COOH group present in tricine unit, one COOH group
and one OH group are coordinated with Cu(II) ion in
a monodentate fashion together with its NH group.
The two free OH units of each tricine act as linkers to
another symmetric unit through H-bonds. The
coordination core consists of two nitrogen atoms from
the bpy ligand and one nitrogen atom and two oxygen
atoms from tricine ligand as shown in Fig. 4. The
coordination geometry around Cu(II) center is found
to be distorted square pyramidal with τ = 0.183,
[τ = |β-α|/60°], where β and α are the two largest
angles around the central atom. The perfect square
pyramidal and trigonal bipyramidal geometries
provide τ = 0 and 1 respectively49. The distances for
Cu(1)-O(1) (1.951(18) Å), Cu(1)-O(3) (2.363(2) Å),
Cu(1)-N(1) (2.047(2) Å) and Cu(1)-N(3) (2.027(2) Å)
lie in the reported range50. Crystal packing diagram of
the complex (2) looks like a channel with floating
ClO4- anions (Supplementary data S2).
The complex (3) crystallized in triclinic crystal
system with P-1 space group, and its molecular
structure is shown in Fig. 5(a). The crystal structure of
complex (3) consists of the [di-µ-oxo-bis(2,2'bipyridine)copper(II)] moieties, coordinated transaxially at each copper(II) ion by µ-nitrato-bis(2,2'bipyridine) copper(II) moieties. It incorporates six
ClO4- as counter anions. The Cu(3)–Cu(3)# is
2.850(2) Å whereas the Cu(3)–O(4)–Cu(3)# bridging
angle of 94.76(3)º falls within the range reported for
similar copper(II) complexes51. The coordination
environment around central copper(II) ions with two
YADAV et al.: REACTIVITY OF TRICINE IN PRESENCE OF Cu(C1O4)2.6H2O & 2,2′-BIPYRIDINE
1039
Table 3Selected parameters for weak interactions in the complexes (1), (2) and (3)
D-H···A
D-H
(Å)
H···A
(Å)
D···A
(Å)
DHA
(°)
Sym. code
0.93
2.52
3.377(4)
154
- x, y, -1- z
0.76
0.91
0.82
0.82
0.93
0.93
0.93
0.93
0.97
0.97
1.94(8)
2.44
2.12
2.48
2.55
2.52
2.35
2.51
2.30
2.51
2.694(7)
2.860(8)
2.923(10)
2.783(7)
3.032(9)
3.198(11)
3.249(10)
3.283(10)
3.087(10)
3.440(12)
169(6)
109
167
103
113
130
163
140
137
159
2- x,1- y, -z

-1+ x, y, z
1-x,1-y,1-z
--2-x,1-y,-z
-1+x, 1+y,z
----2- x,1-y,1-z
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
0.93
2.58
2.59
2.58
2.48
2.53
2.55
2.47
2.46
2.57
2.02
2.60
2.42
2.51
2.23
3.079(10)
3.350(13)
3.073(10)
3.320(12)
3.290(13)
3.461(19)
3.223(17)
3.33(3)
3.156(11)
2.82(4)
3.48(3)
3.222(10)
3.38(5)
2.936(13)
114
139
113
150
139
168
138
155
121
143
159
145
156
132
--1-x,1-y,1-z
---x,-y,1-z
--x,-1+y,-1+z
1-x,-y,1-z
-----x,-1-y,-z
--1-x,-y,-z
1-x,-y,-z
-x,-1-y,-z
Complex (1)
C(1)-H(1)···O(20)
Complex (2)
O (3)-H(3A)···O(2)
N(3)-H(3B)···O(4)
O (4)-H(4)···O(6)
O(4)-H(4)···O(4)
C(1)-H(1)···O(1)
C(2)-H(2)···O(5)
C(7)-H(7)···O(2)
C(10)-H(10)···O(4)
C(12)-H(12A)···O(5)
C(16)-H(16A)···O(6)
Complex (3)
C(1)-H(1)···O(1)
C(14)-H(8)···O(6)
C(22)-H(13)···O(3)
C(25)-H(16)···O(8)
C(34)-H(22)···O(5)
C(39)-H(26)···O(18)
C(39)-H(26)···O(13)
C(40)-H(27)···O(26)
C(45)-H(32)···O(23)
C(50)-H(35)···O(12)
C(56)-H(41)···O(26)
C(59)-H(44)···O(2)
C(111)-H(111)···O(12)
C(120)-H(120)···O(30)
Fig. 3Molecular structure (ORTEP) of (1) drawn at 40 %
probability level.
Fig. 4Molecular structure (ORTEP) of (2) drawn at 40 %
probability level.
nitrogen atoms from bpy ligand and two oxygen
atoms from the bridging oxo groups provides a near
regular square–pyramidal geometry. The bond
distances (Cu-N and Cu-O) range from 1.929(7) to
1.944(8) Å. The apical position is occupied by O(4)
from the bridging nitrato group at a distance of
2.310(6) Å. The corresponding τ value for the square
pyramidal Cu(3) atom is found as 0.056º. The nitrato
oxygen O(4) bridging atom also coordinates with
Cu(2), forming an asymmetric monoatomic bridge
1040
INDIAN J CHEM, SEC A, AUGUST 2011
Fig. 5(a) Molecular structure (ORTEP) of (3) drawn at 40 % probability level. [All hydrogen atoms are omitted for clarity];
(b) Figure showing the copper(II) chromophores.
between Cu(3) and Cu(2) at the distances Cu(3)–O(4)
= 2.310(6) Å, Cu(2)–O(4) = 2.032(6) Å, along with a
Cu(3)–O(4)–Cu(2) bridging angle of 132.31º.
The coordination geometry around Cu(2) is best
described as being distorted octahedral. The basal
plane consists of three nitrogen atoms of bpy rings
and an O(4) atom of bridging nitrate group with
distances ranging from 2.032(8) to 2.082(9) Å. The
apical position is occupied by N(17) atom of bpy ring
with a bond length of 2.208(10) Å. The Cu(2) atom
lies 0.199 Å, above the basal plane towards N(17).
Moreover, this nitrate group is also linked to Cu(1)
through O(3) at a distance of 1.952(6) Å forming a
bridge between Cu(2) and Cu(1) (anti, anti) and
likewise between Cu(1) and Cu(3) (syn, anti). The
geometry around Cu(1) can be described as being
distorted square pyramidal, tending towards trigonal
bipyramidal geometry in view of τ = 0.56. The basal
plane consists of three nitrogen atoms of bpy ligands
and an oxygen atom of nitrate ligand at distances
ranging from 1.952(6) to 2.056(8) Å. The fifth
position is occupied by N(13) atom of bpy ligand at a
distance of 2.195(9) Å. The Cu(1) atom lies at 0.152 Å
above the basal plane towards N(13). The nitrate
anion bridges three copper(II) ions i.e., Cu(I), Cu(2)
and Cu(3), at a distance of [Cu(1)–Cu(2) = 4.34 Å,
Cu(2)–Cu(3) = 8.97 Å and Cu(1)–Cu(3) = 5.94 Å
respectively. The centrosymmetric nature of the
complex results in the repeated Cu(1), Cu(2) and
Cu(3) center atoms.
The influence of intra- and intermolecular bpy–bpy
π-stacking interactions is considered to play a role in
this molecular structure. The intermolecular π–π
interactions with the face-to-face distance being 3.62 Å
and 3.49 Å, form a 1D chain stacked along b-axis
(Supplementary data S3). There are intramolecular
and π–π stacking interactions, between the
neighboring pyridine groups attached to Cu(2) and
Cu(3) ions (ring to ring distance 3.62 Å).
Electrochemical studies
Cyclic voltammograms of the complexes were
recorded at a scan rate of 50 mV/s. in spectroscopic
grade DMF (10-4M) using tetrabutyl ammonium
perchlorate as supporting electrolyte. Cyclic
voltammogram of complex (1) displays a reduction
peak at Epc = -180 V with the corresponding oxidation
peak at Epa = -70 mV. The complex (2) shows a broad
reduction peak Epc= -130 mV with the corresponding
oxidation peak at Epa= -50 mV. Cyclic voltammogram
of complex (3) shows two well separated peaks
(marked as A and B) at -170 V and -650 V (vs.
Ag/AgCl) during cathodic scan as depicted in Fig. 6.
These two peaks are assigned to two consecutive
reductions (CuII CuII→ CuII CuI→ CuI CuI ) occurring
at different Cu(II) centers52. Similarly, stepwise
oxidation ( CuI CuI→ CuII CuI→ CuII CuII ) was also
observed at 20 mV and 280 mV. The reduction peaks
observed at -1050 mV and -1480 mV were assigned
to stepwise reduction of bipyridyl rings (bpy-1, bpy-2).
Magnetic properties
The magnetic susceptibility measurements of a
representative hexanuclear complex (3) at different
temperatures were recorded in the temperature range
5-300 K under a magnetic field of 1000 Oes. The χmT
value at room temperature (300 K) is found to be
1.62 cm3 mol-1 K, lower than the expected value from
six magnetically isolated Cu(II) ions (g > 2.00;
YADAV et al.: REACTIVITY OF TRICINE IN PRESENCE OF Cu(C1O4)2.6H2O & 2,2′-BIPYRIDINE
1041
density is extremely weak. Other bridges, such as
µ-hydroxo54, azido55 or diazine type56,57 can interact
with the spin-rich dx2-y2 orbital of the Cu(II) ions.
Conclusions
The synthesis and characterization of some
interesting Cu(II) complexes ranging from
mononuclear to dinuclear and finally to a hexanuclear
complex is reported. The self-assembly of the
complexes through secondary interactions provide a
channel-type structure in which ClO4- anions are
found floating. However, in the presence of dil. nitric
acid, tricine does not react with Cu(II) ion and
instead, formation of oxo bridged complex dominates.
The Cu(II) ions in hexanuclear complex (3) interact
ferromagnetically.
Fig. 6Cyclic voltamogram of Complex (3) in DMF (10-4M).
Acknowledgement
Authors are thankful to CSIR, New Delhi, India,
for financial support (01(2322)/09/EMR-II).
Supplementary Data
CCDC reference no. 792033, 805831, 805832
contains the supplementary crystallographic data for
complexes (1-3) respectively. These data can be
obtained free of charge via http://www.ccdc.cam.ac.
uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; Fax (+44) 1223-336-033;
Email: [email protected]. Crystal packing
diagrams of complex (1) (S1), complex (2) (S2) and
complex (3) (S3) may be obtained from authors on
request.
Fig. 7 Variation of of χmT versus T of complex (3).
6 × 0.4 = 2.4 cm3 mol-1 K approximately). The χmT
increases with decreasing temperature, reaching a
maximum value of 4.55 cm3 mol-1 K at 4K (Fig. 7). For
planar
bis-µ-hydroxido
copper(II)
species,
antiferromagnetic behaviour is observed with Cu-O-Cu
angle (θ) larger than 97.5º, while ferromagnetic
interaction is observed for complexes with smaller
values of this angle53. In complex (3), the bridging
angle (θ) is observed as 94.76(3)º, being lower than
97.5º, it is thus inferred that in this complex a
ferromagnetic interaction occurs. Additionally, it is
also reported that Cu(II) complexes bearing nitratoO,O′ bridge show negligible magnetic interaction54. In
most cases both the oxygen atoms of the nitrate ion are
coordinated in axial positions where the unpaired spin
References
1 Mukherjee A, Nethaji M & Chakravarty A R, Angew Chem
Int Ed, 43 (2004) 87.
2 Mukherjee A, Raghunathan R, Saha M K, Nethaji M,
Ramasesha R & Chakravarty A R, Chem Eur J, 11 (2005)
3087.
3 Kato M & Tanase T, Inorg Chem, 44 (2005) 8.
4 Buvaylo E A, Kokozay V N, Vassilyeva O Y, Skelton B W,
Jezierska J, Brunel L C & Ozarowski A, Inorg Chem, 44
(2005) 206.
5 Carranza J, Brennan C, Sletten J & Clemente-Juan J M,
Inorg Chem, 42 (2003) 8716.
6 Muhonen H, Hatfield W E & Helms J H, Inorg Chem, 25
(1986) 800.
7 Mishra S, Pfalzgraf L G H, Jeanneau E & Chermette H,
Dalton Trans, (2007) 410.
8 Si S F, Tang J K, Liao D Z, Jiang Z H & Yan S P, Inorg
Chem Commun, 5 (2002) 76.
9 Mukherjee A, Rudra I, Nethaji M, Ramasesha S &
Chakravarty A R, Inorg Chem, 42 (2003) 463.
1042
INDIAN J CHEM, SEC A, AUGUST 2011
10 Beer P D & Gale P A, Angew Chem Int Ed, 40 (2001) 486.
11 Müller A, Das S K, Bőgge H & Beugholt C, Schmidtmann
M, Chem Commun, (1999) 1035.
12 Fujita M, Nagao S & Ogura K, J Am Chem Soc, 117 (1995)
1649.
13 Kim Y H, Calabrese J & McEwen C, J Am Chem Soc, 118
(1996) 1545.
14 Alcalde E, Ramos S & Pérez-Garcia L, Org Lett, 1 (1999)
1035.
15 Tabares L C, Navarro J A R & Salas J M, J Am Chem Soc,
123 (2001) 383.
16 Salta J, Chen Q, Chang Y–D & Zubieta J, Angew Chem Int
Ed Engl, 33 (1994) 757.
17 Ghosh A K, Ghoshal D, Mostafa G, Ribas J & Chaudhuri N
R, Cryst Growth Des, 6 (2006) 36.
18 Zhao Y-J, Hong M-C, Liang Y-C, Su W-P, Cao R, Zhou Z–
Y & Chan A S C, Polyhedron, 20 (2001) 2619.
19 Rarig R S & Zubieta J, Inorg Chim Acta, 319 (2001) 235.
20 Fujita M, Kwon Y J, Washizu S & Ogura K, J Am Chem Soc,
116 (1994) 1151.
21 Suen M-C, Tseng G-W, Chen J-D, Keng T–C & Wang J-C,
Chem Commun, (1999) 1185.
22 Blake A J, Champness N R, Chung S S M, Li W–S &
Schröder M, Chem Commun, (1997) 1675.
23 Jin K, Huang X, Pang L, Li J, Appel A & Wherland S, Chem
Commun, (2002) 2872.
24 Su C-Y, Cai Y-P, Chen C-L, Lissner F, Kang B–S & Kaim
W, Angew Chem, Int Ed, 41 (2002) 3371.
25 Sui B, Fan J, Okamura T A, Sun W Y & Ueyama N, New J
Chem, 25 (2001) 1379.
26 Crans D C, Ehde P M, Shin P K & Pettersson L, J Am Chem
Soc, 113 (1991) 3728.
27 Dubler E, Häring U K, Scheller K H, Baltzer P & Sigel H,
Inorg Chem, 23 (1984) 3785.
28 Baggio R, Calvo R, Garland M T, Peña O, Perec M & Slep L
D, Inorg Chem Commun, 10 (2007) 1249.
29 Baldomá R, Monfort M, Ribas J, Solans X & Maestro M A,
Inorg Chem, 45 (2006) 8144.
30 Sen S, Mitra S, Kundu P, Saha M K, Krüger C & Bruckmann
J, Polyhedron, 16 (1997) 2475.
31 Sheldrick G M, SHELXS-97 Program for the Solution of
Crystal Structures, (University of Göttingen, Göttingen,
Germany), 1997.
32 Sheldrick G M, Acta Cryst, 46A (1990) 467.
33 Bruno I J, Cole J C, Edgington P R, Kessler M, Macrae C F,
McCabe P, Pearson J & Taylor R, Acta Cryst, 58B (2002)
389.
34 Brandenburg K & Putz H, DIAMOND Version 3.0, Crystal
Impact GbR, Bonn, Germany, 2004.
35 Spek A L, J Appl Cryst, 36 (2003) 7.
36 Graham B, Spiccia L, Fallon G D, Hearn M T W, Mabbs F
E, Moubaraki B & Murray K S, J Chem Soc Dalton Trans,
(2001) 1226.
37 Fischer E O & Fischer H, J Organometal Chem, 3 (1965)
181.
38 Nakamoto K, Infrared and Raman Spectra of Inorganic and
Co-ordination Compounds, 4th Edn, John Wiley & Sons,
New York, 1986, pp. 228, 229, 237.
39 D’aniello M J, Jr & Barefield E K, J Organometal Chem, 76
(1974) C50.
40 Logan N & Simpson W B, Spectrochim Acta, 21 (1965) 857.
41 Waters T N & Wright P E, J Inorg Nucl Chem, 33 (1971)
359.
42 Mukhopadhyay U, Bernal I, Massoud S S & Mautner F A,
Inorg Chim Acta, 357 (2004) 3673.
43 Song Y, Zhu D–R, Zhang K–L, Xu Y, Duan C–Y & You XZ, Polyhedron, 19 (2000) 1461.
44 Blackman A G & Tolman W B, Struct and Bonding, Berlin,
97 (2000) 180.
45 Li D, Li S, Yang D, Yu J, Huang J, Li Y & Tang W, Inorg
Chem, 42 (2003) 6071.
46 Yokoi H & Addison A W, Inorg Chem, 16 (1977) 1341.
47 Asokan A, Varghese B & Manoharan P T, Inorg Chem, 38
(1999) 4393.
48 Youngme S, Van Albada G A, Roubeau O, Pakawatchai C,
Chaichit N & Reedijk J, Inorg Chim Acta, 342 (2003) 48.
49 Addison A W, Rao T N, Reedijk J, Rijn J V & Verschoor G
C, J Chem Soc, Dalton Trans, 1984, 1349.
50 Ray A, Rosair G M, Rajeev R, Sunoj R B, Rentschler E &
Mitra S, J Chem Soc Dalton Trans, (2009) 9510.
51 Castro I, Faus J, Julve M, Bois C, Real J A & Lloret F, J
Chem Soc Dalton Trans, (1992) 47.
52 Zhang W, Liu S, Ma C & Jiang D, Polyhedron, 17 (1999)
3835.
53 Crawford V H, Richardson H W, Wasson J R, Hodgson D J
& Hatfield W E, Inorg Chem, 15 (1976) 2107.
54 Hoog P D, Gamez P, Leuken M, Roubeau O, Krebs B &
Reedijk J, Inorg Chim Acta, 357 (2004) 213.
55 Grove H, Sletten J, Julve M, Lloret F & Cano J, J Chem Soc
Dalton Trans (2001) 259.
56 Escuer A, Goher M A S, Mautner F A & Vicente R, Inorg
Chem, 39 (2000) 2107.
57 Tandon S S, Thompson L K, Bridson J N & Benelli C, Inorg
Chem, 34 (1995) 5870.