Synthesis and structure of mono-, di- and tri-nuclear copper(II) benzoate complexes with a tridentate N2O donor Schiff base ligand

Article abstract of DOI:10.1016/j.ica.2012.10.003

Three copper(II) complexes [CuL(PhCOOH)(ClO₄)] (1), [Cu ₂L₂(PhCOO)](ClO₄) (2) and [Cu₃L ₂{(o-NO₂)PhCOO}₂](ClO₄) (3), where HL = 2-[1-(2-dimethylamino-ethyli

Full text of DOI:10.1016/j.ica.2012.10.003

Inorganica Chimica Acta 396 (2013) 66–71
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Inorganica Chimica Acta
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Synthesis and structure of mono-, di- and tri-nuclear copper(II) benzoate
complexes with a tridentate N2O donor Schiff base ligand
c,
Pallab Bhowmik a,b,c, Shouvik Chattopadhyay a, , Ashutosh Ghosh
⇑
⇑
a Department of Chemistry, Inorganic Section, Jadavpur University, Kolkata 700 032, India
b Department of Chemistry, Sundarban Mahavidyalaya, Kakdwip, West Bengal, India
c Department of Chemistry, University College of Science, University of Calcutta, 92, A.P.C. Road, Kolkata 700 009, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 26 April 2012
Received in revised form 22 September 2012
Accepted 9 October 2012
Available online 17 October 2012
Three copper(II) complexes [CuL(PhCOOH)(ClO4)] (1), [Cu2L2(PhCOO)](ClO4) (2) and [Cu3L2{(o-NO2)-
PhCOO}2](ClO4) (3), where HL = 2-[1-(2-dimethylamino-ethylimino)-ethyl]-phenol, a well known Schiff
base ligand, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy
and single crystal X-ray diffraction studies. Complex 1 crystallizes in triclinic space group P ꢀ 1, complex
2 in monoclinic C2 and complex 3 in monoclinic P21/c. The co-ordination polyhedron around each copper
atom is best described as an elongated (4 + 1) square pyramid. Complex 1 is mononuclear with a terminal
Keywords:
Crystal structure
Copper(II)
benzoate, complex 2 is dinuclear containing a
l1,3 benzoate whereas complex 3 is trinuclear having a rare
l1,1,3 benzoate binding three copper centers simultaneously.
Ó 2012 Elsevier B.V. All rights reserved.
Schiff base
Benzoates
Centrosymmetric dimer
Trimer
1. Introduction
Polynuclear complexes containing bridging benzoate groups are
also of current interest due to their biological relevance in many
biochemical systems involving mono- and poly-metallic active
sites [23,24]. In addition, polynuclear metal benzoates are good
candidates for the investigation of exchange–coupling interaction
between adjacent metal ions [25–28]. In these complexes, a benzo-
ate group can assume many types of bridging conformations, the
most important being triatomic syn–syn, anti–anti, and syn–anti
and monatomic [27,28] (Scheme 1). These bridging modes usually
The design and synthesis of coordination polymers, based on
transition-metal ions bridged by benzoate groups, to fabricate
low-dimensional molecule-based magnetic materials are currently
under intense research [1–8]. Among them, the coordination
chemistry of polynuclear copper(II) complexes with bridging
N2O-donor ligands continues to be actively investigated because
of their relevance to a number of areas of importance, including
bioinorganic modeling chemistry [9], magnetic properties of poly-
nuclear species [10], catalysis [11] and coordination polymers
chemistry [12]. The dynamic character of the metal–ligand bonds,
nature and coordinating topologies of the ligands used, metal–li-
gand ratio, different coordination geometries of the metal centers;
nature of the counter ions and a variety of experimental conditions
(such as the temperature, solvents and methods of crystallization)
control the ultimate supra-molecular assemblies formed. The ris-
ing attention in this field is justified by the logical challenge in con-
trolling and manipulating the self-assembly process [13–16]. To
build up the coordination networks containing metal ions with
magnetic anisotropy is also interesting because of the magnetic
properties [17–22].
bind two metal atoms, but a third l1,1,3 bridging mode is also pos-
sible with which a carboxylate group binds three metal atoms, but
such bridging modes are relatively rare [29]. A CSD search provides
only two examples with copper(II), one with anthracene-9-car-
boxylato-O,O,O0 and another with 2,6-bis(trifluoromethyl)benzo-
ato-O,O,O0, where three copper(II) are bridged by a benzoate
group [30,31]. In the present paper, we report the facile syntheses,
characterisations and X-ray structures of three copper(II)
complexes with a tridentate N2O donor Schiff base. Of these three
complexes, one contains a rare l1,1,3 benzoate bridge which binds
three copper(II) centers simultaneously.
2. Experimental
⇑
Corresponding authors. Tel.: +91 9007777373.
E-mail addresses: shouvik.chem@gmail.com (S. Chattopadhyay), ghosh_59@
All chemicals were of reagent grade and used without further
purification.
yahoo.com (A. Ghosh).
0020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2012.10.003

P. Bhowmik et al. / Inorganica Chimica Acta 396 (2013) 66–71
67
Scheme 1. Syn–Syn, Syn–Anti and Anti–Anti bridging mode of benzoate group.
3.2. Physical measurements
3. Materials
Elemental analysis (carbon, hydrogen and nitrogen) was per-
formed using a Perkin–Elmer 240C elemental analyzer. IR spectra
in KBr (4500–500 cmꢀ1) were recorded using a Perkin–Elmer RXI
FT-IR spectrophotometer. Electronic spectra in acetonitrile (1200–
350 nm) were recorded in a Hitachi U-3501 spectrophotometer.
The reagents and solvents used were of commercially available
reagent quality, unless otherwise stated.
3.1. Preparations
3.1.1. Synthesis of the ligand 2-[1-(2-dimethylamino-ethylimino)-
ethyl]-phenol (HL)
3.3. X-ray crystallography
The ligand (HL) was synthesized by refluxing the N,N-dimethyl-
ethelenediamine (10 mmol) with 2-hydroxy acetophenone
(10 mmol) in methanol solution (20 ml) for ca. 3 h. The ligand
was not isolated. The methanolic solution was used for the synthe-
sis of the complexes.
Crystal data for the three crystals are given in Table 1. Single
crystals having suitable dimensions for complexess 1, 2 and 3 were
used for data collection using a ‘Bruker SMART APEX II’ diffractom-
eter equipped with graphite-monochromated Mo K
a radiation
(k = 0.71073 Å). The molecular structures were solved by direct
methods and refinement by full-matrix least squares on F2 using
the SHELX-97 package [32]. Non-hydrogen atoms were refined with
anisotropic thermal parameters. Hydrogen atoms were placed in
their geometrically idealized positions and constrained to ride on
their parent atoms. Empirical absorption corrections were carried
out with the ABSPACK program [33]. Data collection and structure
refinement parameters and crystallographic data for the three
complexes are given in Table 1.
3.1.2. Synthesis of complex [CuL(PhCOOH)(ClO4)] (1)
A methanol solution (5 ml) of copper(II) perchlorate hexahy-
drate (0.74 g, 2 mmol) was added to the methanol solution of HL
(2 mmol) with constant stirring. A solution of PhCOOH (0.245 g,
2 mmol) in methanol (5 ml) was then added to it and stirring
was continued for 30 min. An immediate separation of a small
amount of precipitate was filtered off. The filtrates were left to
stand overnight in open atmosphere when crystalline complexes
started to separate and were collected by filtration. Black single
crystals suitable for X-ray diffraction were also obtained at that
time.
4. Results and discussion
4.1. Syntheses
Yield: 0.59 g (60%). Anal. Calc. for C19H23ClCuN2O7 (489.39): C,
46.53; H, 4.73; N, 5.71. Found C, 46.7; H, 4.5; N, 5.7%. IR (KBr,
cmꢀ1): 1598 (
cC@N), {1672.8 (casC@O), 1374.5 (csC@O)} for carboxy-
The ligand (HL) was prepared by the 1:1 condensation of the
N,N-dimethylethelenediamine and 2-hydroxyacetophenone in
methanol following the literature method [21]. The complexes
were synthesized simply by allowing the Schiff base to react with
alate, 1113.7 1056.9 (c
ClO4), UV–VIS, kmax (nm), (emax (dm3 molꢀ1
cmꢀ1)) (acetonitrile), 603, 371, 300, 271.
3.1.3. Synthesis of complexes [Cu2L2(PhCOO)](ClO4) (2)
Table 1
It was prepared in a similar method to that of complex 1 except
that trimethyl amine (2 mmol) was added after the addition of
PhCOOH. Brown single crystals suitable for X-ray diffraction were
obtained from the filtrate by slow evaporation in open atmosphere.
Yield: 1.117 g. (75%). Anal. Calc. for C31H39Cu2N4O8Cl: C, 49.11;
H, 5.18; N, 7.39. Found: C, 49.1; H, 5.2; N, 7.4%. IR (KBr, cmꢀ1):
Crystal data and structure refinement of complexes 1–3.
1
2
3
Formula
M
Crystal system
Space group
a (Å)
C
19H23ClCuN2O7 C31H39Cu2N4O8Cl C45H41Cu3N7O18Cl
490.39
triclinic
P1 (No. 2)
758.21
monoclinic
C2 (No. 5)
13.452(2)
17.648(3)
7.421(2)
90
108.580(5)
90
1669.9(5)
2
1193.95
monoclinic
P21/c (No. 14)
14.0418(4)
25.1942(6)
13.8830(3)
90
95.696(1)
90
4887.2(2)
4
ꢀ
1599.8 (
1094.4 (
nitrile), 602, 368, 297, 269.
c
C@N), {1550.5 (
c
asC@O), 1434.2(
csC@O),} for carboxyalate,
max (dm3 molꢀ1 cmꢀ1)) (aceto-
8.8242(17)
10.931(2)
12.043(2)
66.977(2)
83.821(2)
77.396(2)
1043.0(3)
2
1.561
1.219
506
0.026
cClO4), UV–VIS, kmax (nm), (
e
b (Å)
c (Å)
a
(°)
b (°)
3.1.4. Synthesis of complex [Cu3L2{(o-NO2)PhCOO}2](ClO4) (3)
It was prepared in a similar method to that of complex 2 except
o-nitrobenzoic acid was used instead of benzoic acid. Deep blue
parallelepiped- shaped single crystals of 3 suitable for X-ray dif-
fraction were obtained from the methanol of the complex by slow
evaporation in air.
c
(°)
V (Å3)
Z
Dc (g cmꢀ3
l
)
1.508
1.408
784
0.101
1.623
1.431
2432
0.051
(mmꢀ1
)
F(000)
Rint
Total reflections
Yield: 1.68 g. (75%). Anal. Calc. for
C45H41Cu3N7O18Cl (FW
8155
8174
73411
Unique reflections 4793
2450
2107
0.0993, 0.3028
293
9362
7043
0.0388, 0.1064
293
1193.95): C, 45.27; H, 3.46; N, 8.21. Found: C, 45.1; H, 3.58; N,
8.2%. IR (KBr, cmꢀ1): 1605.4 (
for carboxyalate, 1091.7
cC@N), {1534.7 (casC@O), 1396.2(csC@O)}
I > 2r(I)
3313
R1, wR2 (I > 2
T (K)
r
(I))
0.0404, 0.1140
293
(c
ClO4), UV–VIS, kmax (nm), (emax
(dm3 molꢀ1 cmꢀ1)) (acetonitrile), 594, 365, 298, 273.

68
P. Bhowmik et al. / Inorganica Chimica Acta 396 (2013) 66–71
a methanol solution of Cu(ClO4)2ꢁ6H2O and benzoic acid (for 1 and
2) or o-nitrobenzoic acid (for 3) in 1:1:1 M ratio. Equimolar
amount of triethylamine was added for deprotonation of the
respective benzoic acid for the synthesis of complexes 2 and 3
(see Section 2). The mononegative tridentate Schiff base ligand
along with a benzoate or o-nitrobenzoate anion (in presence of tri-
methylamine) and perchlorate balance the charge of the complex
species (2 and 3) but the metal ion remains coordinately unsatu-
rated. In such a situation, the benzoate group can exploit their well
known bridging properties to complete the coordination sphere in
copper(II) to result in dinuclear (2) and trinuclear (3) complexes.
The benzoic acid remains in the protonated form in complex 1,
as triethylamine is not used during its synthesis. The coordination
polyhedron around copper(II) is completed by the coordination of a
perchlorate oxygen atom as evident from the X-ray crystal struc-
ture. It is worth mentioning that in absence of the benzoic acid, a
water bridged dinuclear complex is formed, the structure of which
is reported elsewhere [34]. Use of copper fluoroborate produced
the same hydroxo bridged dimeric cation [35]. Use of copper
acetate instead of copper perchlorate produces [CuL(OAc)(H2O)]
in which copper(II) assumes a distorted square pyramidal geome-
try [36]. The details of the synthesis are shown in Scheme 2.
4.2. Structural description of complexes 1, 2 and 3
4.2.1. Complex 1
The structure of 1 together with the atomic numbering scheme
is shown in Fig. 1. The co-ordination polyhedron around the cop-
per(II) is best described as an elongated (4 + 1) square pyramid.
Two nitrogen atoms, N(1) and N(2), and one oxygen atom, O(1),
from the deprotonated Schiff base ligand L and one oxygen atom
O(2) from a coordinated benzoic acid define the equatorial plane.
One oxygen atom, O(7) of a perchlorate group is semi-coordinated
to the copper(II) in the axial position at distances of 2.423(0) Å.
There is a slight distortion to the square plane and the deviations
of the coordinating atoms N(1), N(2), O(1), O(2) from the least-
square mean plane through them are 0.089, ꢀ0.086, 0.088 and
ꢀ0.085 Å, respectively, and that of the copper(II) from the same
Scheme 2. Synthesis of complexes 1, 2 and 3 and some related complexes.

P. Bhowmik et al. / Inorganica Chimica Acta 396 (2013) 66–71
69
plane is 0.124 Å. This deviation from planarity of the equatorial
plane also manifests itself in the trans angles [O(1)–Cu(1)–N(2),
N(1)–Cu(1)–O(2)], which are 167.59 and 176.95.
The puckering analysis [37,38] of Cu(1)–N(1)–C(10)–C(11)–N(2)
ring with q3 = 0.060(4) Å, q2 = Q = 0.777(4) Å indicates the five-
membered chelate ring assumes a gauche conformation. The
N(1)–Cu(1)–N(2) angle is 92.4(2).
4.2.2. Complex 2
The structure determination reveals that complex 2 consists of a
discrete, centrosymmetric dinuclear complex cation [(CuL)2
(PhCOO)]+ and one non-coordinated perchlorate anion. A view of
the complex is given in Fig. 2. In the dimer, two distorted
square-pyramidal copper(II) centers are bridged by a centrosym-
metrically related benzoate anion in l1,3 fashion leading to rela-
tively small CuꢁꢁꢁCu distance (3.136 Å). Within the dimeric unit,
each of the two trigonally distorted square-pyramidal copper(II)
centers is coordinated equatorially by N(1), N(2) and O(1) of the
deprotonated tridentate Schiff base ligand (L) and an oxygen atom,
O(2), of the bridging l1,3 benzoate ion, comprising the basal plane.
A second oxygen atom, O(1)⁄, from the centrosymmetrically re-
lated bridging phenoxo of other Schiff base coordinates axially at
a rather long distance (Cu1. . .O1, 2.574(11) Å) furnishing an elon-
gated square-pyramidal (4 + 1) geometry for each copper(II) center
in the dimeric complex (Symmetry element ⁄ = 1 ꢀ x, y, ꢀz). The
basal bond lengths are 1.924(15), 2.012(18), 1.949(13) and
1.872(13) Å for Cu1. . .N1, Cu1. . .N2, Cu1. . .O2, and Cu1. . .O1,
respectively, for both of two copper(II) centers as they are centro-
symmetrically related to each others. The deviation of the coordi-
nating atoms, N1, N2, O1, and O2, from the mean plane passing
Fig. 2. The structure of 2 with ellipsoids at 20% probability. The H atoms are not
shown for clarity. Selected bond lengths (Å) and bond angles (°): Cu(1)–O(1)
1.872(13); Cu(1)–O(2) 1.949(13), Cu(1)–N(1) 1.924(15), Cu(1)–N(2) 2.012(18);
Cu(1)–O(1⁄) 2.574(11), O(1)–Cu(1)–N(1) 93.0(6), O(1)–Cu(1)–O(2) 91.1(5),
O(2)–Cu(1)–N(2) 87.7(6), N(1)–Cu(1)–N(2) 87.4(7), O(1)–Cu(1)–N(2) 169.8(5),
O(2)–Cu(1)–N(1) 173.9(6), O(1)–Cu(1)–O(1⁄) 84.1(4), O(1⁄)–Cu(1)–O(2) 96.1(4),
O(2)–C(13)–O(2⁄) 129(2). Symmetry element ⁄ = 1 ꢀ x, y, ꢀz.
through them are not more than 0.061 Å, and that of the Copper(II)
atom from the same plane is 0.101 Å.
4.2.3. Complex 3
The structure of 3 together with the atom numbering scheme is
shown in Fig. 3. The asymmetric unit consists of a tri-nuclear spe-
cies and a perchlorate ion. In the trinuclear structure, there are
three bridging o-nitrobenzoate moieties; out of which two are in
l1,3 syn–syn bridging modes and the third one is in a very rare
l1,1,3 mode binding three copper(II) center. Each l1,3 syn–syn
bridging benzoate binds to two Copper(II) centers; Cu(1) and
Cu(2) are bridged by O(2) and O(3), whereas Cu(2) and Cu(3) by
O(6) and O(5), respectively with syn–syn bridging fashion. O(8)
of l1,1,3 benzoate moiety binds Cu(1) and O(7) binds to Cu(2,3) in
the same syn–syn fashion. It is here worth mentioning that this
type of l1,1,3 benzoate bridge, binding three copper(II) units at a
time is very rare in the literature. Only two complexes have been
reported till date [30,31].
The co-ordination polyhedron around the each copper(II) is best
described as an elongated (4 + 1) square pyramid. The square pyra-
midal geometry of central Cu(2) is formed by five oxygen atoms;
two phenoxo oxygen atoms, O(1) and O(4), from two Schiff base
units, three oxygen atoms O(3), O(6) and O(7) from three o-nitro-
benzoate units. The square pyramidal environment of each the two
terminal copper(II) is formed by N(1), N(2), O(1) or N(3), N(4), O(4)
of the Schiff base ligand and O(2), O(8) or O(5), O(7) of two differ-
ent o-nitrobenzoates.
CuꢁꢁꢁCu distances in the complex 3 are Cu(1)–Cu(2) 3.143(5) Å,
Cu(2)–Cu(3) 3.127(5) Å and Cu(1)–Cu(3) 5.931 Å. The coordinating
atoms around central copper(II), Cu(2), in the basal plane (i.e. O(1),
O(3), O(4), and O(6)) deviate from the mean square plane passing
Fig. 1. The structure of 1 with ellipsoids at 30% probability. The H atoms are not
shown for clarity. Selected bond lengths (Å) and bond angles (°): Cu(1)–O(1)
1.892(2), Cu(1)–O(2) 1.997(2), Cu(1)–N(1) 1.941(3), Cu(1)–N(2) 2.017(3),
Cu(1)–O(7) 2.422(3), O(1)–Cu(1)–N(1) 91.90(13), O(1)–Cu(1)–O(2) 90.06(10),
O(2)–Cu(1)–N(2) 90.75(11), N(1)–Cu(1)–N(2) 86.83(13), O(1)–Cu(1)–N(2)
167.57(12), O(2)–Cu(1)–N(1) 176.90(12).

70
P. Bhowmik et al. / Inorganica Chimica Acta 396 (2013) 66–71
Fig. 3. The structure of 1 with ellipsoids at 10% probability. The H atoms are not shown for clarity. Selected bond lengths (Å): Cu(1)–O(1) 1.907(2), Cu(1)–O(2) 1.978(2),
Cu(1)–O(8) 2.329(3), Cu(1)–N(1) 1.947(3), Cu(1)–N(2) 2.018(3), Cu(2)–O(1) 1.987(2), Cu(2)–O(3) 1.913(2), Cu(2)–O(4) 2.092(19), Cu(2)–O(6) 1.917(2), Cu(2)–O(7) 2.203(2),
Cu(2)–O(8) 2.848(3), Cu(3)–O(4) 1.908(2), Cu(3)–O(5) 1.990(2), Cu(3)–O(7) 2.484(2), Cu(3)–N(3) 1.952(3), Cu(3)–N(4) 2.006(3).
through them are ꢀ0.175, 0.166, ꢀ0.159 and 0.168 Å, respectively
and the deviation of the Cu(2) from the same plane is 0.318 Å. The
deviation of the coordinating atoms in the basal plane around
terminal Cu(1) (i.e. N(1), N(2), O(1), O(2)) from the mean plane
passing through them are ꢀ0.12, 0.114, ꢀ0.117, and 0.112 Å,
respectively and that of copper(II), Cu(1), from the same plane is
0.144 Å. Similar is the case for another terminal copper(II), Cu(3),
which deviates from the mean plane passing through N(3), N(4),
O(5), and O(4) is 0.116 Å and the deviations of the coordinating
atoms from the same plane are ꢀ0.118, 0.116, ꢀ0.114, and
0.116 Å, respectively. The angles between mean square planes,
containing terminal Cu(1) and central Cu(2), terminal Cu(3) and
central Cu(2), terminal Cu(1) and terminal Cu(3) are 49.95, 55.37
and 74.86°, respectively.
4.3. IR and electronic spectra and magnetic moments
In the IR spectra of all the complexes 1, 2 and 3 strong and
sharp bands due to azomethine
c(C@N) appear at 1598, 1599.8
and 1605.4 cmꢀ1, respectively. The other IR spectral bands in the
1300–1650 cmꢀ1 region are difficult to assign due to the appear-
ance of several absorption bands both from the Schiff base and
from benzoate ligands. Nevertheless, by comparing the IR spectra
of the Ni(II) complexes of the same ligand but with other anions
(azide and halides), the strong bands at 1672.8, 1550.5 and
1534.7 cmꢀ1 may be assigned to the antisymmetric stretching
mode of the benzoate group, whereas the bands at 1374.5,
1434.2 and 1396.2 cmꢀ1 may be attributed to the symmetric
stretching modes of the benzoate ligands in the complexes 1, 2
and 3, respectively. A strong and sharp band due to perchlorate ap-
pears at 1113.7, 1094.4, and 1091.7 cmꢀ1 for complexes 1, 2 and 3,
respectively [39]. The splitting of the band at1056.9 cmꢀ1 in the IR
spectrum of 1 is indicative of the presence of coordinated perchlo-
rate ions.
Bond distances between benzoate oxygen and copper(II) for l1,3
and l1,1,3 bridging modes differ significantly. Longer bond dis-
tances of l1,1,3 bridging o-nitrobenzoates with different copper(II)
centers, 2.203(2) {Cu(2)–O(7)}, 2.484(2) {Cu(3)–O(7)} and
2.329(3) Å {Cu(1)–O(8)}, indicate the coordination in the axial
positions, whereas smaller bond distances of
l
1,3 bridging o-nitro-
The electronic spectra of 1, 2 and 3 in acetonitrile solution dis-
play d–d absorption band at 603, 602 and 594 nm, respectively.
The positions of these bands are consistent with the observed
square-pyramidal geometry around the copper(II) centers
[40,41]. The UV absorption bands at 371, 300 nm for complex 1,
368, 297 nm for complex 2 and 365, 298 nm for complex 3 nm
benzoates, 1.978(2) {Cu(1)–O(2)}, 1.913(2) {Cu(2)–O(3)}, 1.917(2)
{Cu(2)–O(6)} and 1.990(2) Å {Cu(3)–O(5)} imply coordination in
equatorial plane. The bridging angles are 127.10(3)° (O2–C13–
O3), 126.60(3)° (O5–C32–O6) and 126.20(3)° (O7–C39–O8) for
two l1,3 and one l1,1,3 benzoate respectively.

P. Bhowmik et al. / Inorganica Chimica Acta 396 (2013) 66–71
71
[4] M. Verdaguer, Polyhedron 20 (2001) 1115.
may be assigned to the charge transfer transition. The bands at
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271, 269 and 273 for complexes 1, 2 and 3, respectively are due
to the p–
p⁄ transition of aromatic ring.
[8] A.J. Tasiopoulos, A. Vinslava, W. Wernsdorfer, K.A. Abboud, G. Christou, Angew.
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Room temperature magnetic susceptibility measurements
show that complexes 1, 2 and 3 have magnetic moments close to
1.73 BM as expected for discrete magnetically non-coupled
spin-only value for copper(II), as was observed in similar systems
[42–43].
5. Summary
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The facile synthesis and characterization of three copper(II)
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the last one is trinuclear. A l1,1,3 bridging benzoate is present in tri-
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nuclear complex. The mononuclear complex can be converted to
the dinuclear one by using a base which helps to deprotonate the
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effect of nitro group increases the acidity of benzoate group, allow-
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ethylamine. The facile synthesis of complex 3 may afford a
convenient synthetic route for this type of trinuclear species.
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Crystallographic data were performed at the DST-FIST, India-
funded Single Crystal Diffractometer Facility at the Department
of Chemistry, Jadavpur University.
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Appendix A. Supplementary data
CCDC Nos. 842621 (complex 1), 842622 (complex 2) and
842623 (complex 3) contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.a-
c.uk/data_request/cif. Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/
10.1016/j.ica.2012.10.003.
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[41] S. Biswas, A. Ghosh, Polyhedron 39 (2012) 31.
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