Formation of polynuclear copper(II)-sodium(I) heterometallic complexes derived from salen-type Schiff bases

Article abstract of DOI:10.1016/j.poly.2012.09.058

Three heteronuclear Cu(II)/Na(I) complexes, [Cu₂(salen) ₂Na(ClO₄)(CH₃CN)] (1) [Cu₂(vanen) ₂Na₂(μ_1,1-NCS)₂] (2) and [(Cu)₂(L)₂(Na)

Full text of DOI:10.1016/j.poly.2012.09.058

Polyhedron 49 (2013) 113–120
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Polyhedron
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Formation of polynuclear copper(II)–sodium(I) heterometallic complexes derived
from salen-type Schiff bases
Prasanta Bhowmik a, Klaus Harms b, Shouvik Chattopadhyay a,
⇑
a Department of Chemistry, Inorganic Section, Jadavpur University, Kolkata 700 032, India
b Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35032 Marburg, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 26 July 2012
Accepted 28 September 2012
Available online 12 October 2012
Three heteronuclear Cu(II)/Na(I) complexes, [Cu2(salen)2Na(ClO4)(CH3CN)] (1) [Cu2(vanen)2Na2
1,1-NCS)2] (2) and [(Cu)2(L)2(Na)2(
1,1-CH3CN)(H2O)(ClO4)]ClO4 (3), where H2salen = N,N0-ethylenebis-
(l
l
(salicylideneimine) and H2vanen = N,N0-(1,2-ethylene)-bis(3-methoxysalicylideneimine), have been
prepared and characterized by elemental analyses, IR and UV–Vis spectroscopy and single crystal
X-ray diffraction studies. Two Cu(II)–salen units are connected by an Na ion in complex 1. Two
Cu(II)–vanen–Na(I) moieties are connected by bridging thiocyanate groups in complex 2. A novel
end-on bridging asymmetric acetonitrile is observed in complex 3.
Keywords:
Cu(II)/Na(I)
Bridging acetonitrile
End-on thiocyanate
X-ray structure
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
quadridentate bis(salicylidene)-type Schiff-base ligand family,
furnished novel Cu(II)–Na(I)–Na(I)–Cu(II) tetra-nuclear species,
Schiff bases, formed by the condensation of an amine with an
aldehyde [1], usually coordinate to a metal through the imine
nitrogen [2–10]. The literature clearly shows that the study of this
diverse ligand system is linked with many of the key advances
made in inorganic chemistry [11–17]. Among the Schiff bases,
‘‘salen-types’’, which are formed by the condensation of various
diamines and salicylaldehyde derivatives, are perhaps the most
popular ones. In general, the dinegative anionic forms of the
salen-type Schiff bases act as tetradentate chelating ligands with
two nitrogen and two oxygen atoms as donor sites to produce a
mononuclear complex [18]. However, by exploiting the fascinating
bridging ability of the phenoxo O atoms, these metal complexes
can be used as ligands to coordinate a second metal ion, thereby
generating multinuclear complexes [19]. Thus, the mononuclear
complexes of such ligands with dipositive transition elements
can suitably be used as a ‘‘ligand complex’’ for the syntheses of het-
ero-metallic complexes. Recently, we have incorporated Na(I) ions
with the help of such Cu(II) chelates, to result in hetero-metallic
complexes [20]. Now, we are examining the possibility of connect-
ing two heteronuclear Cu(II)/Na(I) entities. In the present study we
have found that counter anions having good bridging efficiency can
easily connect two such units to form a tetranuclear complex. If,
however, the bridging ability of the counter anions is not sufficient,
then solvent molecules may serve this purpose.
whereas H2salen [=N,N0-(1,2-ethylene)-bis(salicylideneimine)]
afforded a tri-nuclear Cu(II)–Na(I)–Cu(II) complex. X-ray crystal
structure determinations have established the structures of these
complexes. Herein, we report the syntheses, spectroscopic charac-
terizations and room-temperature magnetic moments of three
polynuclear hetero-metallic complexes. All of them have also been
characterized by X-ray crystallography. A novel end-on bridging
asymmetric acetonitrile ligand is observed in one of the complexes.
2. Experimental
2.1. Materials
All starting materials were commercially available, reagent
grade, and used as purchased without further purification.
2.2. Synthesis
Caution! Although our samples never exploded during handling,
only a small amount of the perchlorate salt should be prepared and
it should be handled with care.
2.2.1. Preparation of the ligands N,N0-ethylene-bis-salicylideneimine
(H2salen) and N,N0 ethylene-bis(3-methoxysalicylideneimine)
(H2vanen)
The tetradentate Schiff base ligands, H2salen and H2vanen, were
synthesized by refluxing 1,2-diaminoethane (10 mmol, 0.68 ml)
with salicyladehyde and 3-methoxysalicyladehyde (20 mmol, 3.04 g)
in methanol (50 ml) for ca. 1 h, respectively.
Our attempts with H2vanen [=N,N0-(1,2-ethylene)-bis(3-
methoxysalicylideneimine)], as a representative example of the
⇑
Corresponding author. Tel.: +91 9007777373.
E-mail address: shouvik.chem@gmail.com (S. Chattopadhyay).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.09.058

114
P. Bhowmik et al. / Polyhedron 49 (2013) 113–120
2.2.2. Synthesis of [Cu2(salen)2Na(ClO4)(CH3CN)] (1)
2.3. Physical measurements
An acetonitrile solution of Cu(II) acetate monohydrate (1 mmol,
0.25 g) was added to an acetonitrile solution of H2salen (1 mmol,
0.328 g), and the resulting mixture was refluxed for 1 h. A solution
of sodium perchlorate (1 mmol, 0.140 g) in acetonitrile was added
to this mixture, followed by refluxing for 30 min and then filtering.
Dark green single crystals suitable for X-ray diffraction were
obtained from the red coloured filtrate by slow evaporation in
the open atmosphere.
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 on a Hitachi U-3501 spectropho-
tometer. The magnetic susceptibility measurements were done
with an EG & PAR vibrating sample magnetometer, model 155 at
room temperature and diamagnetic corrections were made using
Pascal’s constants.
Yield: 0.58 g (70.4%). Anal. Calc. for
C34H31Cu2N5NaO8Cl
(823.18): C, 49.61; H, 3.80; N, 8.51. Found: C, 49.4; H, 3.7; N,
8.8%. UV–Vis, kmax (nm) (emax (dm3 molꢀ1 cmꢀ1)) (acetonitrile):
570 (683), 359 (21255). Magnetic moment: 1.71 BM.
2.4. X-ray crystallography
2.2.3. Synthesis of [Cu2(vanen)2Na2(l1,1-NCS)2] (2)
Single crystals of 1 and 2 of suitable dimensions were used for
An acetonitrile solution of Cu(II) acetate monohydrate (1 mmol,
0.25 g) was added to an acetonitrile solution of H2vanen (1 mmol,
0.328 g) and the resulting mixture was refluxed for 1 h, followed
by the addition of a solution of sodium thiocyanate (1 mmol,
0.081 g) in acetonitrile. The mixture was then stirred for about half
an hour and then filtered. The filtrate was left at room temperature
to isolate a red crystalline complex. Diffraction quality single crys-
tals were obtained from a DMF solution.
data collection using a ‘Bruker SMART APEX II’ diffractometer
equipped with graphite-monochromated Mo
Ka radiation
(k = 0.71073 Å) at 293 K. The molecular structures were solved by
direct methods and refinement by full-matrix least squares on
F2 using the SHELX-97 package [21,22]. Non-hydrogen atoms were
refined with anisotropic thermal parameters. C-bonded hydrogen
atoms were included in calculated positions and refined using
the ‘riding model’. Empirical absorption corrections were carried
out with the ABSPACK program [23].
Yield: 0.69 g (73.2%). Anal. Calc. for
C38H36Cu2N6Na2O8S2
(941.95): C, 48.45; H, 3.85; N, 8.92. Found: C, 48.62; H, 3.71; N,
8.85%. UV–Vis, kmax (nm) (emax (dm3 molꢀ1 cmꢀ1)) (acetonitrile):
534 (476), 366 (10882). Magnetic moment: 1.71 BM.
On the other hand, a crystal of complex 3 was mounted in inert
oil and transferred to the cold gas stream of the cooling device.
Data were collected at 100 K on a STOE IPDS 2T diffractometer
using graphite monochromated Mo K
a radiation, and were cor-
2.2.4. Synthesis of [(Cu)2(vanen)2(Na)2(
(ClO4) (3)
l
1,1-CH3CN)(H2O)(ClO4)]-
rected for absorption effects using multiscanned reflections. Non-
hydrogen atoms were refined anisotropically. H atoms of water
molecules were located by difference Fourier maps and were kept
fixed. All other hydrogen atoms were placed in their geometrically
idealized positions and constrained to ride on their parent atoms.
Programs used: SHELXL-97 [21,22], PLATON [24] and XAREA [25] and
SIR92 [26]. The crystal structure of 3 shows positional disorder
regarding one perchlorate anion and one methylene group in a side
chain and of the bridging acetonitrile ligand. The ‘‘acetonitrile li-
gand’’ has been refined as a superposition of one half of an aceto-
nitrile molecule and two half water molecules at the positions of
the nitrogen and the methyl group of the acetonitrile ligand. A
summary of the crystallographic data are given in Table 1.
An acetonitrile solution of Cu(II) acetate monohydrate (1 mmol,
0.2 g) was added to an acetonitrile solution of H2vanen (1 mmol,
0.328 g) and the resulting mixture was refluxed for 1 h. A solution
of sodium perchlorate (1 mmol, 0.140 g) in acetonitrile was then
added to this mixture, followed by stirring for 15 min. Red crystals
suitable for X-ray diffraction were obtained after a few days and
collected by filtration.
Yield: 0.75 g (69%). Anal. Calc. for C37H41.50Cl2Cu2N4.50Na2O18
(1081.21): C, 41.10; H, 3.87; N, 5.83. Found: C, 40.82; H, 3.45; N,
5.53%. UV–Vis, kmax (nm) (emax (dm3 molꢀ1 cmꢀ1)) (acetonitrile):
538 (524), 365 (13776). Magnetic moment: 1.71 BM.
Table 1
Crystal data and refinement details of complexes 1, 2 and 3.
Complex 1
Complex 2
Complex 3
Formula
C
34H31Cu2N5NaO8Cl
C38H36Cu2N6Na2O8S2
C37H41.5Cl2Cu2N4.5Na2O18
Formula weight
Crystal size (mm)
T (K)
823.18
941.95
0.20 ꢁ 0.20 ꢁ 0.20
293
1081.21
0.14 ꢁ 0.24 ꢁ 0.24
100
0.20 ꢁ 0.20 ꢁ 0.20
293
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/c
11.5016(8)
18.5630(12)
16.4619(12)
90
orthorhombic
Pca21
20.3227(5)
9.7675(2)
19.6508(5)
90
orthorhombic
Pbca
22.7382(5)
15.8031(3)
23.6779(7)
90
a
(°)
b (°)
103.564(4)
90
90
90
90
90
c
(°)
Z
4
4
8
dcalc (g cmꢀ3
)
1.600
1.396
1680
1.604
1.281
1928
1.685
1.229
4408
l
(mmꢀ1
F(000)
)
Total reflections
41913
32150
62198
Unique reflections
Observed data [I > 2
5223
3738
8851
6814
8997
5964
r
(I)]
Number of parameters
Rint
461
0.085
528
0.030
643
0.072
R1, wR2 (all data)
R1, wR2 [I > 2r(I)]
0.0707, 0.1282
0.0456, 0.1117
0.0533, 0.0807
0.0348, 0.0738
0.0727, 0.0608
0.0331, 0.0543

P. Bhowmik et al. / Polyhedron 49 (2013) 113–120
115
Scheme 1. Syntheses of the complexes.
salt present, different complexes, [Cu(salen)] or [Cu(vanen)(OH2)],
are produced, where the copper atoms assume square planar or
square pyramidal geometries respectively. The X-ray structures
of these complexes are reported elsewhere [28,29]. When Na(I) is
incorporated in the system, the geometry of Cu(II) changes from
square pyramidal to square planar.
It is noteworthy here that H2vanen is a compartmental ligand,
but H2salen is not. In the presence of a sodium salt, H2salen thus
forms the trinuclear Cu(II)–Na(I)–Cu(II) complex 1, whereas H2-
vanen forms a dinuclear Cu(II)–Na(I) complex. These dinuclear
complexes are then connected by thiocyanate to form the tetranu-
clear complex 2. In the absence of thiocyanate, the dinuclear units
3. Results and discussion
3.1. Syntheses
The ligands H2salen and H2vanen were prepared by the 1:2 con-
densation of 1,2-diaminoethane with salicyladehyde and 3-meth-
oxysalicyladehyde respectively in methanol, following the
literature method [27]. H2salen was reacted with copper acetate
monohydrate and sodium perchlorate to prepare complex 1. Simi-
larly, H2vanen was reacted with copper acetate monohydrate fol-
lowed by sodium thiocyanate to prepare complex 2; and sodium
perchlorate to prepare complex 3 (Scheme 1). Without any sodium

116
P. Bhowmik et al. / Polyhedron 49 (2013) 113–120
Fig. 1. ORTEP3 diagram of complex 1 with 40% ellipsoid probability. Hydrogen atoms are not shown for clarity.
are connected by a solvent acetonitrile molecule to form tetranu-
clear complex 3. The acetonitrile bridges two Cu(II)–Na(I) moieties
in an end-on fashion.
The range of deviations of the coordinating atoms [O(1), O(2),
N(1), N(2) around Cu(1) and O(3), O(4), N(3), N(4) around Cu(2)]
are ꢀ0.121 to ꢀ0.160 and +0.122 to +0.160 Å from their corre-
sponding least-square mean plane, and Cu(1) and Cu(2) also are
0.014 and 0.013 Å away from the same plane. In the Cu(II)–salen
units, the Cu(II) centre is surrounded by two adjacent imine N
atoms and by two phenoxo oxygen atoms of the ligand; the max-
imum and minimum Cu–N bond distances are 1.956(5) and
1.917(6) Å, respectively, and the Cu–O bond distances are in the
range 1.890(3)–1.902(4) Å (Table 2). On the other side of the
square plane two phenoxo oxygen atoms simultaneously act as
the binding sites to the Na+ ion. The Na+ ion thus plays the role
of a mediator to organize two Cu(II)–salen units around it. Due
to the stereo electronic disposition of the Na+ ion, the two Cu(II)–
salen units are slightly rotated with respect to each other in the
outer coordination sphere of the Na+ ion. The four phenoxo oxygen
atoms from the two (salen)2ꢀ ligands, the nitrogen atom of the
acetonitrile and an oxygen atom of the perchlorate constitute the
distorted octahedral geometry around Na+. The Na–O (phenoxo)
bond distances fall in the range 2.375(3)–2.512(3) Å. The Na–O
(perchlorate) bond distance is 2.386(4) Å and Na–N (acetonitrile)
is 2.508(5) Å. Selected bond lengths and bond angles are given in
Table 2.
It has been interesting to study the coordination chemistry of
alkali metal ions, originating mostly from a desire to develop
molecular systems that can mimic naturally occurring molecules
responsible for the selective transport of ions. Crown ethers, crypt-
ands and related ligands are the most important class of complex-
ing agents for alkali metal ions and consequently structure/
selectivity studies of the alkali metal ions usually focus on such
systems [30–32]. Recent developments in the field of supramolec-
ular chemistry have shown that small building blocks can lead,
through self-assembly processes, to large, well-defined structures,
which are held together by non-covalent interactions such as
hydrogen bonds [33,34], metal–ligand coordination [35–39], etc.
Sometimes, solvent molecules are coordinated to the metal ion to
stabilize the complex in the solid state and may lead to the
formation of polynuclear complexes using their bridging proper-
ties [40]. Acetonitrile is a commonly used solvent for the prepara-
tion of such complexes. However,
l1,1-CH3CN bridged complexes
with alkali metal ions are very rare (CSD search file, Supporting
Information).
3.2. Description of the structures
3.2.2. Complex 2
3.2.1. Complex 1
The molecular structure of 2 reveals a heteronuclear complex
The molecular structure of 1 is built from isolated trinuclear
molecules of [Cu2(salen)2Na(ClO4)(CH3CN)] (Fig. 1). The two Cu(II)
centres have a distorted square planar coordination geometry with
a hexacoordinated distorted octahedral sodium in between them.
which features a double l-1,1-thiocyanate bridged Cu(II)/Na(I)
dimer in which two pentagonal pyramidal Na(I) centres are
bridged by the two centrosymmetrically related thiocyanate ions
in an end-on fashion. A perspective view of this complex with

P. Bhowmik et al. / Polyhedron 49 (2013) 113–120
117
Table 2
maximum and minimum Cu–N bond distances are 1.935(3) and
1.921(3) Å, respectively, and the Cu–O bond distances are in the
range 1.890(2)–1.909(2) Å (Table 3). The coordination environ-
ment around Na(1) and Na(2) shows a pentagonal pyramidal
geometry where the O4 compartment [O(1), O(2), O(3), O(4) for
Na(1) and O(5), O(6), O(7), O(8) for Na(2)] from the tetradentate
Schiff base ligand and a nitrogen atom [N(5) for Na(1) and N(6)
for Na(2)] from the end-on bridging thiocyanate represent the ba-
sal plane, and the nitrogen atom [N(6) for Na(1) and N(5) for Na(2)]
from another end-on bridged thiocyanate coordinates axially. The
Na–O(methoxy) distance is larger than that of Na–O(phenolate).
The Na–O (phenoxo) bond distances are in the range 2.278(2)–
2.335(2) Å and the Na–O (methoxy) distances fall in the range
2.687(3)–2.759(3) Å. The Na–N (thiocyanate) distances are in the
range 2.383(3)–2.590(3) Å. The average Cuꢂ ꢂ ꢂNa intra-molecular
distance is 3.232 Å. The maximum and minimum Cu–O(phenoxo)
–Na bridge angles are 100.7(9)° and 99.1(9)°. Selected bond lengths
and bond angles are given in Table 3.
Selected bond lengths (Å) and bond angles (°) for complex 1.
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–O(1)
Cu(1)–O(2)
Na(1)–O(1)
Na(1)–O(2)
Na(1)–O(3)
1.925(4)
1.924(4)
1.901(2)
1.891(3)
2.424(3)
2.512(3)
2.375(3)
Cu(2)–N(3)
Cu(2)–N(4)
Cu(2)–O(3)
Cu(2)–O(4)
Na(1)–O(4)
Na(1)–O(5)
Na(1)–N(5)
1.956(5)
1.917(6)
1.890(3)
1.902(4)
2.424(4)
2.386(4)
2.508(5)
N(1)–Cu(1)–N(2)
N(1)–Cu(1)–O(1)
N(1)–Cu(1)–O(2)
N(2)–Cu(1)–O(1)
N(2)–Cu(1)–O(2)
O(1)–Cu(1)–O(2)
O(1)–Na(1)–O(2)
O(1)–Na(1)–O(3)
O(1)–Na(1)–O(4)
O(1)–Na(1)–O(5)
O(1)–Na(1)–N(5)
O(2)–Na(1)–O(3)
O(2)–Na(1)–O(4)
O(2)–Na(1)–O(5)
84.4(2)
94.1(1)
169.4(1)
171.1(1)
94.2(1)
88.8(1)
65.0(1)
103.8(1)
164.3(1)
100.9(1)
91.6(1)
77.4(1)
99.9(1)
159.3(1)
N(3)–Cu(2)–N(4)
N(3)–Cu(2)–O(3)
N(3)–Cu(2)–O(4)
N(4)–Cu(2)–O(3)
N(4)–Cu(2)–O(4)
O(3)–Cu(2)–O(4)
O(2)–Na(1)–N(5)
O(3)–Na(1)–O(4)
O(3)–Na(1)–O(5)
O(3)–Na(1)–N(5)
O(4)–Na(1)–O(5)
O(4)–Na(1)–N(5)
O(5)–Na(1)–N(5)
84.9(3)
93.1(2)
173.5(2)
171.5(2)
94.7(2)
88.2(1)
92.2(1)
66.7(1)
92.5(1)
155.2(1)
92.2(1)
93.6(1)
103.7(2)
3.2.3. Complex 3
Complex 3 crystallizes in the orthorhombic space group Pbca.
The molecular structure of 3 reveals a heteronuclear complex,
[Cu2(vanen)2Na2(l1,1-CH3CN)(ClO4)(H2O)](ClO4). A representative
the corresponding labelling scheme is depicted in Fig. 2. All the
Cu(II) centres show a four-coordinated distorted square planar
geometry in which two phenoxo and two imine nitrogen atoms
of the deprotonated di-Schiff base, (vanen)2ꢀ, constitute the equa-
torial plane. The average deviations of the coordinating atoms
around Cu(1) and Cu(2) are 0.046 and 0.049 Å from the least-
square mean planes passing through the O(2), O(3), N(1), N(2)
and O(6), O(7), N(3), N(4) atoms, respectively. The deviations of
Cu(1) and Cu(2) are 0.041 and 0.052 Å from the same planes. The
ORTEP diagram is shown in Fig. 3. Among the Cu(II) atoms, Cu(1) is
coordinated by two nitrogen atoms, N(3) and N(4), and two phen-
oxo oxygen atoms, O(5) and O(7), whereas Cu(2) is surrounded by
two imine nitrogen atoms, N(1) and N(2), and two phenoxo oxygen
atoms, O(1) and O(3). Both Cu(1) and Cu(2) have distorted square
planar geometries. There is a slight distortion to the square plane,
and the deviations of the coordinating atoms N(3), N(4), O(5) and
O(7) from the least-square mean plane through them are 0.055,
Fig. 2. ORTEP3 diagram of complex 2 with 40% ellipsoid probability. Hydrogen atoms are not shown for clarity.

118
P. Bhowmik et al. / Polyhedron 49 (2013) 113–120
Table 3
Na(1) is surrounded by two phenoxo oxygen atoms, O(5) and
Selected bond lengths (Å) and bond angles (°) for complex 2.
O(7), and two methoxy oxygen atoms, O(6) and O(8), of the Schiff
base in the basal plane, one oxygen atom, O(300) of a water mole-
cule, and one nitrogen atom, N(400) from a bridging acetonitrile, in
axial positions, forming a distorted octahedral geometry. Na(2) is
surrounded by two phenoxo oxygen atoms, O(1) and O(3), and
two methoxy oxygen atoms, O(2) and O(4), of the Schiff base in
the basal plane, one oxygen atom, O(300) of a coordinated perchlo-
rate, and one nitrogen atom, N(400) from the bridging acetonitrile,
in axial positions, forming a distorted octahedral geometry. The
Na–O(methoxy) distance is larger than that of Na–O(phenolate).
The Cuꢂ ꢂ ꢂNa intra-molecular average distance is 3.282 Å and the
Na(1)ꢂ ꢂ ꢂNa(2) intra-molecular distance is 3.546 Å. The two Na ions
are interconnected through the N atom of the acetonitrile ligand.
Due to the asymmetric bridging of the acetonitrile, the
Na(1)ꢂ ꢂ ꢂN(400) distance [2.492(2) Å] is considerably larger than
the Na(1)ꢂ ꢂ ꢂN(400) distance [2.372(2) Å]. The Cu(1)–O(5)–Na(1),
Cu(1)–O(7)–Na(1), Cu(2)–O(1)–Na(2), Cu(2)–O(3)–Na(2) and
Na(1)–N(400)–Na(2) bridging angles are 102.5(7)°, 103.0(7)°,
102.0(8)°, 102.8(8)° and 93.6(7)°, respectively. Both Cu–O–O–Na
cores are almost planar. Selected bond lengths and bond angles
are given in Tables 4 and 5. It is worth mentioning here that there
is a disorder in the structure. Only 50% of the bridges are CH3CN;
the other 50% are H2O bridges. In the second 50% the positions of
the N atom and the methyl group of the CH3CN molecule are pop-
ulated with oxygen atoms (with a distance of 265 pm between
them) of water molecules.
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–O(2)
Cu(1)–O(3)
Na(1)–O(1)
Na(1)–O(2)
Na(1)–O(3)
Na(1)–O(4)
Na(1)–N(5)
Na(1)–N(6)
1.924(2)
1.935(3)
1.893(2)
1.905(2)
2.759(3)
2.280(2)
2.318(2)
2.746(3)
2.383(3)
2.590(3)
Cu(2)–N(3)
Cu(2)–N(4)
Cu(2)–O(6)
Cu(2)–O(7)
Na(2)–O(5)
Na(2)–O(6)
Na(2)–O(7)
Na(2)–O(8)
Na(2)–N(5)
Na(2)–N(6)
1.921(3)
1.934(2)
1.909(2)
1.890(2)
2.718(3)
2.335(2)
2.278(2)
2.687(3)
2.560(3)
2.384(3)
N(1)–Cu(1)–N(2)
N(1)–Cu(1)–O(2)
N(1)–Cu(1)–O(3)
N(2)–Cu(1)–O(2)
N(2)–Cu(1)–O(3)
O(3)–Cu(1)–O(2)
O(1)–Na(1)–O(2)
O(1)–Na(1)–O(3)
O(1)–Na(1)–O(4)
O(1)–Na(1)–N(5)
O(2)–Na(1)–O(3)
O(2)–Na(1)–O(4)
O(1)–Na(1)–N(6)
O(2)–Na(1)–N(5)
O(2)–Na(1)–N(6)
O(3)–Na(1)–O(4)
O(3)–Na(1)–N(5)
O(3)–Na(1)–N(6)
84.6(1)
94.3(9)
178.3(1)
174.7(1)
93.7(1)
87.4(9)
60.5(7)
126.9(8)
154.3(9)
82.9(1)
69.6(8)
128.9(8)
103.3(1)
143.3(1)
94.1(9)
60.1(7)
143.1(1)
97.0(1)
N(3)–Cu(2)–N(4)
N(3)–Cu(2)–O(6)
N(3)–Cu(2)–O(7)
N(4)–Cu(2)–O(6)
N(4)–Cu(2)–O(7)
O(6)–Cu(2)–O(7)
O(5)–Na(2)–O(6)
O(5)–Na(2)–O(7)
O(5)–Na(2)–O(8)
O(5)–Na(2)–N(5)
O(5)–Na(2)–N(6)
O(6)–Na(2)–O(7)
O(6)–Na(2)–O(8)
O(6)–Na(2)–N(5)
O(7)–Na(2)–O(8)
O(7)–Na(2)–N(5)
O(7)–Na(2)–N(6)
O(8)–Na(2)–N(5)
84.9(1)
93.9(1)
173.8(1)
178.7(9)
94.1(9)
87.1(9)
60.7(7)
129.8(8)
161.0(9)
98.3(1)
83.2(1)
69.1(8)
128.2(8)
98.6(1)
61.4(7)
91.0(1)
144.7(1)
96.7(1)
The hydrogen atom, H(301), attached to O(300) of the coordi-
nated water molecule in the complex is engaged in hydrogen bond
formation with the symmetry related (3/2 ꢀ x, 1/2 + y, z) oxygen
ꢀ0.055, ꢀ0.056 and 0.056 Å respectively and that of Cu(1) from the
same plane is 0.015 Å. In contrast, Cu(2) lies on the square plane.
Fig. 3. ORTEP3 diagram of complex 3 with 40% ellipsoid probability. Hydrogen atoms are not shown for clarity.

P. Bhowmik et al. / Polyhedron 49 (2013) 113–120
119
Table 4
Table 6
Selected bond distances (Å) for complex 3.
Hydrogen bond distances (Å) and angles (°) for complex 3.
Cu(1)ꢀO(5)
Cu(1)ꢀO(7)
Cu(1)ꢀN(3)
Cu(1)ꢀN(4)
Cu(2)ꢀN(1)
Cu(2)ꢀN(2)
Cu(2)ꢀO(1)
Cu(2)ꢀO(3)
Na(1)ꢀO(2)
Na(1)ꢀO(5)
Na(1)ꢀO(6)
Na(1)ꢀO(7)
1.889(2)
1.904(2)
1.937(2)
1.921(2)
1.923(2)
1.917(2)
1.889(2)
1.896(2)
2.947(2)
2.329(2)
2.638(2)
2.301(2)
Na(1)ꢀO(8)
Na(1)ꢀO(300)
Na(1)ꢀN(400)
Na(2)ꢀO(1)
Na(2)ꢀO(2)
Na(2)ꢀO(3)
Na(2)ꢀO(4)
Na(2)ꢀO(100)
Na(2)ꢀN(400)
Cu(1)ꢀNa(1)
Cu(2)ꢀNa(2)
Na(1)ꢀNa(2)
2.677(2)
2.342(3)
2.492(2)
2.297(2)
2.678(2)
2.2686(2)
2.661(2)
2.342(2)
2.372(2)
3.301(1)
3.263(1)
3.546(1)
D–Hꢂ ꢂ ꢂA
O(300)–H(300)ꢂ ꢂ ꢂO(200)
O(300)–H(301)ꢂ ꢂ ꢂO(103#)
D–H
Hꢂ ꢂ ꢂA
2.00(3)
2.23(3)
Dꢂ ꢂ ꢂA
2.826(3)
3.024(5)
\D–Hꢂ ꢂ ꢂA
169(4)
168(4)
0.83(2)
0.81(2)
#: ꢀx + 3/2, y + 1/2, z.
atom of the coordinated perchlorate, O(103), to form a chain and
H(300) is involved in hydrogen bond formation with the oxygen
atom of perchlorate ion, O(200) (Fig. 4). Details of the H-bonding
are given in Table 6.
3.3. IR and electronic spectra and magnetic properties
Table 5
Selected bond angles (°) for complex 3.
The characteristic broad peaks for perchlorate in the IR spectra
of complexes 1 and 3 appear around 1065–1106 cm-1 (1065 and
1104 cmꢀ1 for complex 1 and 1072 and 1106 cmꢀ1 for complex
3). The splitting of the bands for complexes 1 and 3 are indicative
of coordinated perchlorate, as substantiated in the crystal struc-
tures [41]. A strong and sharp band due to the azomethine
(C@N) group within 1638–1585 cmꢀ1 are customarily noticed in
the IR spectra of all the complexes. A broad band at 3425 cmꢀ1
in the IR spectrum of complex 3 indicates the OH stretching vibra-
tion of the coordinated water molecule, which is involved in
hydrogen bonding. The bands in the range 2929–2930 cmꢀ1 are
due to alkyl C–H bond stretching of methoxy groups for complexes
2 and 3. In complex 2, a band at 2079 cmꢀ1 is assigned to the pres-
ence of the N-coordinated thiocyanate [20].
The electronic spectra (measured in acetonitrile solution) dis-
play a single absorption band at 570, 538 and 534 nm for com-
plexes 1, 2 and 3 respectively. The positions of these bands are
consistent with the observed square-based geometry around the
Cu(II) centres [20,42]. The intense bands at about 359, 366 and
365 nm for complexes 1, 2 and 3, respectively are due to ligand-
to-metal charge transfers. The electronic spectrum of the ligand
shows absorption bands at 220, 261 and 331 nm. These bands
are also present in the complexes.
O(5)ꢀCu(1)ꢀO(7)
O(5)ꢀCu(1)ꢀN(3)
O(5)ꢀCu(1)ꢀN(4)
O(7)ꢀCu(1)ꢀN(3)
O(7)ꢀCu(1)ꢀN(4)
N(3)ꢀCu(1)ꢀN(4)
O(5)ꢀNa(1)ꢀO(300)
O(5)ꢀNa(1)ꢀO(400)
O(5)ꢀNa(1)ꢀO(8)
O(6)ꢀNa(1)ꢀO(400)
O(6)ꢀNa(1)ꢀN(400)
O(7)ꢀNa(1)ꢀO(8)
O(5)ꢀNa(1)ꢀN(400)
O(6)ꢀNa(1)ꢀO(7)
O(6)ꢀNa(1)ꢀO(8)
O(6)ꢀNa(1)ꢀO(300)
O(5)ꢀNa(1)ꢀO(7)
O(8)ꢀNa(1)ꢀN(400)
O(300)ꢀNa(1)ꢀO(400)
O(300)ꢀNa(1)ꢀN(400)
O(7)ꢀNa(1)ꢀO(300)
O(7)ꢀNa(1)ꢀO(400)
O(7)ꢀNa(1)ꢀN(400)
O(8)ꢀNa(1)ꢀO(300)
O(8)ꢀNa(1)ꢀO(400)
O(5)ꢀNa(1)ꢀO(6)
86.3(7)
94.0(8)
175.7(9)
177.6(8)
94.3(8)
85.5(8)
120.0(8)
136.5(9)
130.1(6)
86.7(7)
86.7(7)
62.0(6)
136.5(9)
129.6(7)
168.4(7)
91.0(7)
68.2(6)
83.2(7)
86.96(9)
87.0(9)
116.0(8)
133.2(7)
133.2(7)
82.6(7)
83.2(7)
61.5(6)
O(1)ꢀCu(2)ꢀO(3)
O(1)ꢀCu(2)ꢀN(1)
O(1)ꢀCu(2)ꢀN(2)
O(3)ꢀCu(2)ꢀN(1)
O(3)ꢀCu(2)ꢀN(2)
N(1)ꢀCu(2)ꢀN(2)
O(2)ꢀNa(2)ꢀO(3)
O(1)ꢀNa(2)ꢀO(2)
O(1)ꢀNa(2)ꢀO(3)
O(1)ꢀNa(2)ꢀO(4)
O(1)ꢀNa(2)ꢀO(100)
O(1)ꢀNa(2)ꢀO(400)
O(1)ꢀNa(2)ꢀN(400)
O(3)ꢀNa(2)ꢀO(400)
O(3)ꢀNa(2)ꢀN(400)
O(4)ꢀNa(2)ꢀO(100)
O(4)ꢀNa(2)ꢀO(400)
O(4)ꢀNa(2)ꢀN(400)
O(100)ꢀNa(2)ꢀO(400)
O(100)ꢀNa(2)ꢀN(400)
O(3)ꢀNa(2)ꢀO(4)
O(3)ꢀNa(2)ꢀO(100)
O(2)ꢀNa(2)ꢀO(400)
O(2)ꢀNa(2)ꢀO(4)
O(2)ꢀNa(2)ꢀO(100)
O(2)ꢀNa(2)ꢀN(400)
86.1(7)
94.1(9)
179.6(9)
179.7(9)
94.1(8)
85.6(9)
130.6(7)
61.7(7)
69.0(7)
131.5(7)
112.7(8)
128.6(8)
128.6(8)
142.8(1)
142.8(1)
86.0(7)
92.0(7)
92.0(7)
93.3(9)
93.3(9)
62.5(6)
110.1(8)
77.0(8)
166.8(7)
87.4(8)
77.0(8)
Fig. 4. H-bonded chain of complex 3.

120
P. Bhowmik et al. / Polyhedron 49 (2013) 113–120
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Room temperature magnetic susceptibility measurements
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1.73 BM.
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In the present paper, we reported the syntheses and structures
of three heteronuclear Cu(II)/Na(I) complexes. The first one is a tri-
nuclear complex (1), where two Cu(salen) moieties are linked by a
central sodium ion. Use of the compartmental ligand H2vanen in-
stead of the non-compartmental H2salen produces a heteronuclear
Cu(II)–Na(I) moiety. These Cu(II)–Na(I) moieties can then be joined
by the use of bridging thiocyanate to prepare a tetranuclear com-
plex (2). In the absence of any such bridging ligand, a solvent ace-
tonitrile molecule bridges two Cu(II)–Na(I) moieties to form
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Acknowledgement
This work was supported by CSIR, India (Fellowship for Prasanta
Bhowmik, Sanction No. 09/096(0607)/2010-EMR-I, dated 27.1.10).
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retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
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