Study of copper(II) complexes of two diacetyl monooxime thiosemicarbazones: X-ray crystal structure and magneto-structural correlation of [Cu(dmoTSCH)Cl]2·H2O (dmoTSCH = monoanion of diacetyl monooxime thiosemicarbazone)

Article abstract of DOI:10.1016/j.poly.2011.12.042

Cu(II) complexes of the tridentate thiosemicarbazone ligands diacetyl monooxime thiosemicarbazone (dmoTSCH₂) and diacetyl monooxime (4-phenyl)thiosemicarbazone (dmoPhTSCH₂) have been synthesized. X-ray crystal structures of dmoPhTSCH₂ and [Cu(dmoTSCH)Cl] ₂·H₂O (1·H₂O) are also reported. The Cu(II) compound 1·H₂O is a dinuclear complex, where the Cu(II) centers have a square pyramidal geometry and are bridged by two thiolato ligands. A C₂ axis passes through the middle of Cu₂S ₂ rectangle. Variable temperature susceptibility measurement for 1·H₂O shows that this compound exhibits a very weak antiferromagnetic behavior (in the solid state) with J₁ = -2.97 cm^-1, using the Heisenberg isotropic spin Hamiltonian (H = -J ₁S₁·S₂). DFT calculations show that the intramolecular magnetic interaction should be ferromagnetic, and the net antiferromagnetic behavior is due to competition with antiferromagnetic intermolecular interactions through hydrogen bonds.

Full text of DOI:10.1016/j.poly.2011.12.042

Polyhedron 35 (2012) 77–86
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Polyhedron
journal homepage: www.elsevier.com/locate/poly
Study of copper(II) complexes of two diacetyl monooxime thiosemicarbazones:
X-ray crystal structure and magneto-structural correlation of
[Cu(dmoTSCH)Cl]2ꢀH2O (dmoTSCH = monoanion of diacetyl monooxime
thiosemicarbazone)
Sumita Naskar a, Subhendu Naskar a,c, Heike Mayer-Figge b, William S. Sheldrick b, Montserrat Corbella d,
,
⇑
Javier Tercero d, Shyamal Kumar Chattopadhyay a,
⇑
a Department of Chemistry, Bengal Engineering and Science University, Shibpur, Howrah 711 103, India
b Lehrstuhl für Analytische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany
c Department of Applied Chemistry, Birla Institute of Technology, Mesra, Ranchi 835215, Jharkhand, India
d Department of Inorganic Chemistry, University of Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Cu(II) complexes of the tridentate thiosemicarbazone ligands diacetyl monooxime thiosemicarbazone
(dmoTSCH2) and diacetyl monooxime (4-phenyl)thiosemicarbazone (dmoPhTSCH2) have been synthe-
sized. X-ray crystal structures of dmoPhTSCH2 and [Cu(dmoTSCH)Cl]2ꢀH2O (1ꢀH2O) are also reported.
The Cu(II) compound 1ꢀH2O is a dinuclear complex, where the Cu(II) centers have a square pyramidal
geometry and are bridged by two thiolato ligands. A C2 axis passes through the middle of Cu2S2 rectangle.
Variable temperature susceptibility measurement for 1ꢀH2O shows that this compound exhibits a very
weak antiferromagnetic behavior (in the solid state) with J1 = ꢁ2.97 cmꢁ1, using the Heisenberg isotropic
spin Hamiltonian (H = ꢁJ1S1ꢀS2). DFT calculations show that the intramolecular magnetic interaction
should be ferromagnetic, and the net antiferromagnetic behavior is due to competition with antiferro-
magnetic intermolecular interactions through hydrogen bonds.
Received 26 October 2011
Accepted 31 December 2011
Available online 16 January 2012
Keywords:
Thiosemicarbazone
Diacetyl monooxime
Cu(II) complex
X-ray crystal structure
Magnetic interaction
DFT calculations
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
62Cu) has renewed interest in the study of the Cu(II) thiosemicar-
bazone complexes and their redox activities [12–16]. It is believed
The coordination chemistry of Cu(II) with nitrogen–sulfur donor
ligands remains an area of unabated attention due to their rele-
vance to the active sites of various copper containing enzymes
[1]. As a class of nitrogen–sulfur donor ligands, thiosemicarba-
zones are especially attractive because of the interesting chemical,
biological, structural and electronic properties of their metal com-
plexes [2–8]. It has also been known for a long time that Cu(II) thi-
osemicarbazone complexes possess cytotoxic and antitumor
properties, and the biological activity of the thiosemicarbazones
is enhanced on complexation to the Cu(II) ion [4,5,8–12]. A recent
discovery of selective uptake and accumulation of certain bis(thio-
semicarbazone)Cu(II) complexes by hypoxic malignant cells and
the possible application of this phenomena for imaging of tumor
cells by Positron Emission Tomography using 64Cu (or other posi-
tron emitting radionucleotides of copper, such as 60Cu, 61Cu or
that reduction of Cu(II) to Cu(I) species is responsible for the accu-
mulation of the copper thiosemicarbazone complexes inside the
tumor cells.
Most of the studies on Cu(II) thiosemicarbazone chemistry in-
volve tridentate ligands like pyridine-2-aldehyde thiosemicarba-
zone and related derivatives or tetradentate ligands like diacetyl
thiosemicarbazone or its derivatives [9–19]. Apart from their bio-
logical relevance, magneto-structural correlations of binuclear
Cu(II) complexes of the type [CuLX]2, where L is a tridentate thio-
semicarbazone monoanion and X is a monoanionic donor, have
also attracted considerable attention. In these binuclear complexes
the Cu(II) atoms may be bridged by an enethiolato sulfur atom or
by the X atoms (Scheme 1) [17–19]. In spite of considerable efforts,
the factors that govern nature of the bridging atom (i.e. thiolato
bridged versus X-bridged dimers) and the effects of various param-
eters, like bridge-angle, nature of coligands, extent of distortion of
the coordination geometry of Cu(II) (from an ideal square planar
arrangement) on the magnetic properties of the complexes are still
not well understood. Diacetyl monooxime thiosemicarbazones
(Scheme 2) have been shown to be versatile tridentate ligands
⇑
Corresponding authors. Fax: +34 934907725 (M. Corbella), tel.: +91 33 2668
0521; fax: +91 33 2668 2916 (S.K. Chattopadhyay).
E-mail addresses: montse.corbella@ub.edu (M. Corbella), shch20@hotmail.com
(S.K. Chattopadhyay).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.12.042

78
S. Naskar et al. / Polyhedron 35 (2012) 77–86
JASCO FT-IR-460 spectrophotometer. UV–Vis spectra were re-
N
corded using a JASCO V-530 UV–Vis spectrophotometer. Electro-
chemical data were collected using a CH instruments 1106A
potentiostat. A three-electrode configuration with Pt working and
auxiliary electrodes, Ag/AgCl reference electrode were used. The
potentials were calibrated against the ferrocene/ferrocenium cou-
ple (0.44 V versus Ag/AgCl reference). All the electrochemical
experiments were performed under a dry nitrogen atmosphere
with millimolar concentrations of the samples dissolved in DMSO
containing 0.1 M TEAP as the supporting electrolyte.
N
N
Cu
X
N
X
S
Cu
S
N
S
X
N
Cu
N
S
Cu
N
Magnetic susceptibility measurements were carried out on a
polycrystalline sample at the ‘‘Unitat de Mesures Magnètiques’’
(Universitat de Barcelona) with a Quantum Design SQUID MPMP-
XL susceptometer apparatus, working in the range 2–300 K under
magnetic fields of approximately 500 G (between 2 and 30 K)
and 10000 G (between 35 and 300 K). Diamagnetic corrections
were estimated from Pascal tables. The fit was performed by min-
X
Scheme 1.
OH
N
S
imizing the function R =
R
(vMꢀTexp
ꢁ
vMꢀTcalc)2/
R
(
vMꢀTexp)2. X-
EtOH, RT
M(LH)Cl
band EPR spectra, on a polycrystalline sample, was recorded on a
Bruker ESP-300E spectrometer, at room temperature and 70 K, at
the ‘‘Unitat de Mesures Magnètiques’’ (Universitat de Barcelona).
N
CuCl2 +
N
RNH
H
LH = dmoTSCH, dmoPhTSCH
R = H,
dmoTSCH2
R=C6H5, dmoPhTSCH2
2.3. Synthesis of the thiosemicarbazone ligands
Scheme 2.
The
ligands
diacetylmonooxime
thiosemicarbazone
(dmoTSCH2) and diacetylmonooxime (4-phenyl)thiosemicarba-
zone (dmoPhTSCH2) were prepared following the procedures de-
scribed in the literature [20,34].
[20–22], though their structural chemistry and magneto-structural
correlations of their complexes are scarcely explored. We are par-
ticularly interested in these types of ligands because of the well
known capability of the oxime moiety to form polynuclear com-
plexes and its potential for generating interesting supramolecular
networks [23–27]. The hydrogen atom of the oxime –OH group
can participate in strong intra- or intermolecular hydrogen bond
formations with other donor atoms or groups [21,22,28,29]. Thus
metal complexes bearing non-deprotonated oximes may be con-
sidered as supramolecular synthons, capable of forming extended
supramolecular networks via intermolecular hydrogen bonds.
Moreover, such an extended hydrogen bonding network may act
as a conduit for magnetic exchange between metal centers [30–
32].
In this paper we report two Cu(II) complexes of thiosemicarba-
zone ligands formed by condensation of diacetyl monooxime with
thiosemicarbazone or 4-(phenyl) thiosemicarbazone (Scheme 2).
The X-ray crystal structures of one of the thiosemicarbazone li-
gands and one Cu(II) complex are also reported here. The magnetic
properties of the structurally characterized Cu(II) complex is stud-
ied in details. An attempt is made to correlate the magneto-struc-
tural properties of our complex with those of similar complexes
reported in the literature.
2.3.1. dmoTSCH2
Anal. Calc. for C5H10N4SO: C, 34.48; H, 5.75; N, 32.18. Found: C,
34.51; H, 5.80; N, 32.24%. 1H NMR (d ppm): 11.56 (1H, s), 10.19
(1H, s), 8.34 (1H, s), 7.74 (1H, s), 2.09 (3H, s), 1.99 (3H, s). Selected
IR bands (cmꢁ1): 3415
m
OH, 3235
m
, 3154 msNH , 1597 (
mC@N), 1013
as
NH2
2
(mN–O), 780 (
mC@S).
2.3.2. dmoPhTSCH2
Anal. Calc. for C11H14N4SO: C, 52.80; H, 5.60; N, 22.40. Found: C,
52.65; H, 5.80; N, 22.58%. 1H NMR (d ppm): 11.66 (1H, s), 10.58
(1H, s), 9.88 (1H, s), 7.56 (2H, d), 7.36 (2H, t), 7.20 (1H, t), 2.17
(3H, s), 2.08 (3H, s). Selected IR bands (cmꢁ1): 3271
mOH, 3206
m
NH, 1593 (
2.4. Synthesis of the complexes
2.4.1. Synthesis of [Cu(dmoTSCH)Cl]2ꢀH2O (1ꢀH2O)
mC@N), 1009 (mN–O), 758 (mC@S).
To a solution of 0.171 g (1 mmol) CuCl2ꢀ2H2O in 10 mL ethanol
was added a solution of 0.175 g (1 mmol) dmoTSCH2 in 10 mL eth-
anol. A green precipitate separated out immediately. The pH of the
reaction mixture was 3–4. After 1 h of stirring, concentrated HCl
was added to the reaction mixture to adjust the pH to 1 and the
resulting mixture was stirred for another 3 h. The green precipitate
that formed was filtered, washed with alcohol and then dried over
fused CaCl2. The compound was recrystallized from ethanol. Yield:
0.120 g, 43%. Anal. Calc. for C10H20N8S2O3Cl2Cu2: C, 21.33; H, 3.55;
N, 19.91. Found: C, 21.52; H, 3.73; N, 19.98%. Electronic spectrum
2. Experimental
2.1. Materials
CuCl2ꢀ2H2O, thiosemicarbazide and diacetyl monooxime were
procured from Aldrich and were used without further purification.
HPLC grade DMF and DMSO were used for spectroscopic and elec-
trochemical studies. Tetraethyl ammonium perchlorate (TEAP)
used for the electrochemical work was prepared as reported in
the literature [33]. All solvents were of A.R. grade and were used
as received for the synthetic work.
in DMF solution k/nm (e
/Mꢁ1 cmꢁ1): 626 (232), 404 (6445), 303
(23465). ESI-MS: 472 (100%) [Mꢁ2Clꢁ2H]+. Selected IR bands
(cmꢁ1): 3227 (
m
OH), 3224 (
m
), 3140 (msNH ), 1610 (
mC@N), 1074
as
NH2
2
(mN–O).
2.4.2. [Cu(dmoPhTSCH)Cl]2 (2)
2.2. Physical measurements
This was synthesized following a similar procedure to that of
1ꢀH2O. Yield: 0.250 g, 67%. Anal. Calc. for C22H26N8S2O2Cl2Cu2: C,
37.93; H, 3.73; N, 16.09. Found: C, 37.76; H, 3.76; N, 16.13%. Elec-
Elemental analyses were performed on a Perkin-Elmer 2400 C,
H, N analyzer. Infrared spectra were recorded as KBr pellets on a
tronic spectrum in DMF solution k/nm (e
/Mꢁ1 cmꢁ1): 608 (568),

S. Naskar et al. / Polyhedron 35 (2012) 77–86
79
Table 1
Table 2
Crystallographic data for dmoPhTSCH2 and [Cu(dmoTSCH)Cl]2ꢀH2O (1ꢀH2O).
Selected bond distances (Å) and angles (°) for dmoPhTSCH2 and [Cu(d-
moTSCH)Cl]2ꢀH2O (1ꢀH2O).
dmoPhTSCH2 1ꢀH2O
1ꢀH2O
1ꢀH2O
dmoPhTSCH2
Empirical formula
M
C
11H14N4OS
C10H18Cl2Cu2N8O2S2H2O
562.48
250.33
Cu(1)–N(1)
Cu(1)–N(2)
Cu(1)–Cl(1)
Cu(1)–S(1)
Cu(1)–S(1)d
2.005(4)
1.965(4)
2.2434(13) N(1)–C(1)
2.2691(12) N(2)–N(3)
2.8346(12) N(2)–C(2)
N(3)–C(3)
S(1)–C(3)
O(1)–N(1)
1.760(5) 1.6728(17)
1.386(5) 1.4010(17)
1.293(6) 1.285(2)
1.378(5) 1.3675(18)
1.290(6) 1.287(2)
1.321(5) 1.374(2)
1.333(5) 1.339(2)
1.416(2)
T (K)
108 (2)
108 (2)
k (Å)
0.71073
monoclinic
P21/n (no. 14) C2/c
5.4867(1)
22.1337(6)
9.9385(3)
90
0.71073
monoclinic
Crystal system
Space group
a (Å)
b (Å)
c (Å)
10.5688(8)
14.5778(8)
12.9759(8)
90
N(4)–C(3)
N(4)–C(4)
a
(°)
Cl(1)–Cu(1)–S(1)
Cl(1)–Cu(1)–N(1)
Cl(1)–Cu(1)–N(2)
102.43(5)
93.74(13)
O(1)–N(1)–C(1) 116.7(3) 113.07(13)
N(3)–N(2)–C(2) 119.3(4) 120.49(13)
b (°)
92.723(3)
90
1205.58(5), 4 1999.2(2), 4
1.379
0.258
90.039(8)
90
c
(°)
167.12(12) N(2)–N(3)–C(3) 112.2(3) 117.69(13)
N(1)–C(1)–C(2) 113.3(4) 115.48(14)
163.11(13) N(2)–C(2)–C(1) 113.9(5) 112.96(14)
U (Å3), Z
Cl(1)–Cu(1)–S(1)d 93.15(4)
Dcalc (g cmꢁ3
)
1.869
2.633
S(1)–Cu(1)–N(1)
S(1)–Cu(1)–N(2)
S(1)–Cu(1)–S(1)d
N(1)–Cu(1)–N(2)
N(1)–Cu(1)–S(1)d
N(2)–Cu(1)–S(1)d
l
(mmꢁ1
)
84.70(13)
95.74(4)
78.51(17)
88.11(11)
96.83(12)
S(1)–C(3)–N(3) 125.2(3) 119.22(12)
S(1)–C(3)–N(4) 117.0(3) 127.54(12)
N(3)–C(3)–N(4) 117.8(4) 113.23(14)
Reflections collected
Total, unique
Rint
10756, 2182
0.029
4572, 1876
0.070
Obs. (I > 2.0
r
(I))
1713
1010
R1 (I > 2.0 (I))
r
0.0305
0.0339
Cu(1)–S(1)–Cu(1)d 84.14(4)
wR2 (all data)
0.0831
2182/0/156
1.01
0.25, ꢁ0.17
0.0550
1876/1/128
0.69
0.69, ꢁ0.38
d
2ꢁx, y, 1/2 ꢁ z.
Data/restraints/parameter
Goodness-of-fit (GOF) on F2
Largest difference in peak and
hole (e Åꢁ3
)
in ethanol. The analytical data support their formulations. The IR
spectra of the complexes indicate coordination through the depro-
tonated thiolate and the two imine nitrogen atoms. The structure
of one Cu(II) complex was solved to get a better understanding
of the molecular and supramolecular structures.
414 (7950), 350 (10591). ESI-MS: 624 (98%) [Mꢁ2Clꢁ2H]+. Se-
lected IR bands (cmꢁ1): 3317 (
mNH), 1597 (mC@N), 1067 (mN–O).
2.5. Crystallographic data collection and structure determination
3.2. Description of the X-ray crystal structures
Crystal data were collected on a Bruker Smart CCD area detector
diffractometer at 108(2) K for the ligand dmoPhTSCH2 and the
The ORTEP diagram for the ligand dmoPhTSCH2 is given in
Fig. 1. In the free ligand dmoPhTSCH2 (Fig. 1) the N2 atom is trans
to both S1 and N1 atoms. The iminooxime thiosemicarbazone
backbone is planar and it makes a dihedral angle of 9.41(6)° with
the phenyl ring. The observed bond lengths are similar to those re-
complex 1ꢀH2O, using graphite-monochromated MoK
a radiation.
The structures were solved by direct methods and refined by least
squares using the program SHELX 97 [35]. The non-hydrogen atoms
were refined with anisotropic displacement parameters. All hydro-
gen atoms were placed at calculated positions and refined as riding
atoms using isotropic displacement parameters coupled to those of
the parent atoms. Semi-empirical absorption corrections along with
corrections for the Lorentz and polarization effects were applied. A
summary of the crystallographic data is collected in Table 1, and the
important bond distances and angles are collected in Table 2.
ported in the literature [34] and reflect
p-delocalization over the
thiosemicarbazone backbone. In the lattice, two adjacent mole-
cules form a complementary hydrogen bonded dimer by O(1)–
H(1)ꢀ ꢀ ꢀN(1)a interactions (symmetry code for a = 2 ꢁ x, ꢁy, ꢁz;
see Table 3 for details of the H-bonding parameters). These dimers
are then interlinked with each other by complementary N(3)–
H(3)ꢀ ꢀ ꢀS(1)b (symmetry code for b = ꢁx, ꢁy, 1 ꢁ z) hydrogen bonds,
forming two dimensional sheets (Supplementary Fig. 1). Adjacent
sheets are then interconnected to each other by complementary
C(21)–H(21C)ꢀ ꢀ ꢀO(1)c interactions (symmetry code for c = 1ꢁx,
ꢁy, ꢁz) to form a three dimensional network (Supplementary
Fig. 2).
The asymmetric unit of [Cu(dmoTSCH)Cl]2ꢀH2O (Fig. 2) consists
of a square plane around the central Cu(II) atom, which is coordi-
nated to the iminooxime nitrogen (N1), imine nitrogen (N2),
deprotonated iminothiolate sulfur (S1) and the chloride ion (Cl1);
half a molecule of lattice water completes the asymmetric unit.
The dihedral angle between the two chelate rings is 3.11(6)°. The
ligand is effectively planar, but the S(1), Cu(1) and Cl(1) atoms
deviate from the plane of the ligand by 0.250(1), 0.181(1) and
ꢁ0.033(1) Å, respectively. Apart from the N(1), N(2), S(1) and
Cl(1) atoms, which constitute the square plane around the Cu(1)
atom, another sulfur atom (S(1)d, symmetry code for d = 2 ꢁ x, y,
1/2 ꢁ z) of a neighboring asymmetric unit is also coordinated to
the Cu(1) atom at a longish distance of 2.8346(12) Å, making the
2.6. Computational details
The computational strategy followed to calculate the exchange
coupling constants in transition metal complexes was described in
a previous paper [36]. For the calculation of the exchange coupling
constants for any polynuclear complex with n different exchange
constants, at least the energy of n + 1 spin configurations must
be calculated. In the case of the studied models, we have calculated
the energy corresponding to three or two different spin distribu-
tions to obtain two or one exchange coupling constants. The calcu-
lations were performed with the GAUSSIAN03 [37] program using
guess functions generated with Jaguar 6.0 software [38]. The hy-
brid B3LYP functional [39] has been used in all calculations. We
have employed a triple-n all electron basis set with two p polariza-
tion functions for copper atoms [40] and a double-n all electron ba-
sis set for the other elements, as proposed by Schaefer et al. [41].
3. Results and discussion
3.1. Synthesis
Cu(II) coordination environment square pyramidal (s = 0.07) [42].
The Cu(1)d atom of the same neighboring unit is similarly bonded
to the S(1) atom of the first unit, forming a dinuclear complex
(Fig. 3). The basal planes of the two square pyramidal Cu(II)
The Cu(II) compounds were obtained in good yields by the reac-
tion of the appropriate thiosemicarbazone ligand with CuCl2ꢀ2H2O

80
S. Naskar et al. / Polyhedron 35 (2012) 77–86
Fig. 1. ORTEP diagram of dmoPhTSCH2.
Table 3
0
Dimensions of hydrogen bonds (distances (ÅA), angles (°)) in the structures
dmoPhTSCH2 and [Cu(dmoTSCH)Cl]2ꢀH2O (1ꢀH2O).
Hꢀ ꢀ ꢀA (Å)
D–Hꢀ ꢀ ꢀA (°)
Dꢀ ꢀ ꢀA (Å)
dmoPhTSCH2
N(4)–H(4)ꢀ ꢀ ꢀN(2)
O(1)–H(1)ꢀ ꢀ ꢀN(1)a
N(3)–H(3)ꢀ ꢀ ꢀS(1)b
C(21)–H(21C)ꢀ ꢀ ꢀO(1)c
2.05
2.02
2.61
2.57
114
147
163
141
2.5372(17)
2.7669(17)
3.4665(14)
3.390(2)
1ꢀH2O
O(1)–H(1)ꢀ ꢀ ꢀCl(1)
O(1)–H(1)ꢀ ꢀ ꢀCl(1)e
O(2)–H(2)ꢀ ꢀ ꢀO(1)f
O(2)ꢀ ꢀ ꢀH(4B)g–N(4)g
N(4)–H(4A)ꢀ ꢀ ꢀCl(1)h
2.57
2.76
2.17
2.15
2.49
133
113
140
165
159
3.201(3)
3.191(3)
2.866(3)
3.008(4)
3.325(3)
D = donor and A = acceptor.
a
Symmetry element: 2 ꢁ x, ꢁy, ꢁz.
Symmetry element: ꢁx, ꢁy, 1 ꢁ z.
Symmetry element: 1 ꢁ x, ꢁy, ꢁz.
Symmetry element: 3/2 ꢁ x, 1/2 ꢁ y, ꢁz.
Symmetry element: 1 ꢁ x, y, 1/2 ꢁ z.
Symmetry element: ꢁ1 + x, y, z.
b
c
e
f
g
h
Fig. 2. Asymmetric unit and atom numbering scheme of [Cu(dmoTSCH)Cl]2ꢀH2O
(1ꢀH2O).
Symmetry element: 1/2 + x, 1/2 + y, z.
complex and/or intermolecular interactions. At room temperature
fragments are parallel and related to each other by a C2 axis pass-
ing through the middle of the Cu2S2 rectangle. The dinuclear enti-
ties, which are related to each other by a glide plane (ac), are then
interlinked by O(1)–H(1)ꢀ ꢀ ꢀCl(1)e (symmetry code for e = 3/2 ꢁ x,
1/2 ꢁ y, ꢁz) and its complementary O(1)e–H(1)eꢀ ꢀ ꢀCl(1) hydrogen
bonds, to form a one dimensional chain along the ‘c’ axis (Fig. 4).
The dimers are also connected to each other along the ‘a’ axis by
O(2)–H(2)ꢀ ꢀ ꢀO(1), O(2)–H(2)ꢀ ꢀ ꢀO(1)f (symmetry code for f = 1ꢁx,
y, 1/2 ꢁ z), O(2)ꢀ ꢀ ꢀH(4B)d–N(4)d, O(2)ꢀ ꢀ ꢀH(4B)g–N(4)g (symmetry
code g = ꢁ1 + x, y, z) hydrogen bonds to form another one dimen-
sional chain (Supplementary Fig. 3). Finally the dimers are also
interconnected to each other along the ‘b’ axis by N(4)–
H(4A)ꢀ ꢀ ꢀCl(1)h (symmetry code for h = 1/2 + x, 1/2 + y, z) hydrogen
bonds, leading to the formation of a three dimensional network
(Supplementary Fig. 4).
the
pected value for two uncoupled Cu(II) ions. The
v
MT product is 0.81 cm3 molꢁ1 K, which is close to the ex-
v
MT values are
more or less constant between 300 and ꢂ30 K, when it suddenly
starts decreasing and reaches a value of ꢂ0.33 cm3 molꢁ1 K at 2 K.
The experimental data were fitted with the Bleaney–Bowers
equation [43], derived from the Heisenberg isotropic spin Hamilto-
nian (H = ꢁJ1S1ꢀS2) for two coupled S = 1/2 ions. The best least-
squares fit was obtained with J1 = ꢁ2.97 cmꢁ1 and g = 2.098
(R = 6.2 ꢃ 10ꢁ4), with a TIP of 60 ꢃ 10ꢁ6 cm3 molꢁ1 per Cu(II) ion
(dashed line in Fig. 5). The g value is in good agreement with the
results obtained from the EPR spectrum (gav = 2.09).
As described earlier, in this compound the Cu(II) atoms in the
dinuclear unit have a square pyramidal geometry and two thiolate
atoms bridge the two Cu(II) atoms in such a manner that the
square pyramids are arranged sharing a basal-apical edge with par-
allel basal planes. Several compounds have been reported in the lit-
3.3. Magnetic properties of 1ꢀH2O
erature with the same [Cu2(l-S)2] core and a similar arrangement
of the square pyramids [17,18,44–48]. The structural parameters
and the magnetic exchange constant (J), referenced to the spin
Hamiltonian H = ꢁJS1ꢀS2, are summarized in Table 4. Most of these
compounds have pyridine-2-carbaldehyde thiosemicarbazone or
Magnetic susceptibility data were recorded from room temper-
ature to 2 K. The
vMT versus T curve (Fig. 5) is characteristic of a
very weak antiferromagnetic interaction in the dinuclear copper(II)

S. Naskar et al. / Polyhedron 35 (2012) 77–86
81
Fig. 3. The dimeric structure of [Cu(dmoTSCH)Cl]2ꢀH2O (1ꢀH2O).
0.8
0.7
0.6
0.5
χ
0.4
0.3
0
50
100
150
200
250
300
T (K)
Fig. 5.
vMT vs. T plot for compound [Cu(dmoTSCH)Cl]2ꢀH2O (1ꢀH2O). The I symbol
represents the experimental values and the dashed line and solid line represent the
best fit with the equation for a dinuclear complex and including the intermolecular
interactions, respectively.
present in compound 1, though the tridentate monoanionic thio-
semicarbazone ligand is slightly different. As a result, the struc-
tural parameters of the present compound are comparable to
those reported for the other compounds in Table 4. In contrast,
compound E, [Cu2Cl2(l-S-dept)2][Cu2Cl4(l-Cl)2] with the S-dept
(S-dept = (N,N,N0,N0-tetraethyl) pyridine-2,6-dithiocarboxamide) li-
gand [44], has two sulfur atoms in the basal plane (CuXNS2) and its
structural parameters are significantly different from the values
found for the other compounds in Table 4. So except for compound
E, the values of the structural parameters for the other compounds
are of the same order, with some variation in the Cu–Sapical dis-
tance (2.74–2.92 Å) and the Cu–S–Cu angle (85.5–99.79°); how-
ever, in spite of these similarities, the magnetic behavior is
significantly different, with values in the range ꢁ28.1 to
+13.8 cmꢁ1. It was reported by Garcia-Torjal and co-workers [17],
that the nature of the coligands in the basal plane influences the
magnetic behavior. The most antiferromagnetic coupling was
found for compounds where X has a low electronegativity value
(X = I), while the most ferromagnetic coupling values were found
for compounds where the electronegativity of X was high (X = O).
However, when the monodentate ligand (X) is polyatomic, donat-
ing through an O atom, the reported compounds (Table 4) could
Fig. 4. One dimensional zig-zag chain of 1ꢀH2O along ‘c’ axis.
some derivatives of it as a polydentate ligand and consequently the
basal plane is constituted by CuXN2S. The same basal plane is also

82
S. Naskar et al. / Polyhedron 35 (2012) 77–86
Table 4
Comparison of structural parameters and the magnetic exchange constant J (H = ꢁJS1ꢀS2) for dinuclear complexes with a [Cu2(
environment of the Cu(II) ions, sharing a base to apex edge, and a CuXYNS basal plane, where Y = N except for E where Y = S.
l-S)2] core, a square-pyramidal
X
d(Cu–Sb)a (Å)
d(Cu–Sa)b (Å)
a
(CuSCu) (°)
d(Cuꢀ ꢀ ꢀCu) (Å)
J1(exp.) (cmꢁ1
)
Ref.
A
B
C
D
I
2.27
2.27
2.28
2.28
2.27
2.28
2.28
2.27
2.27
2.30
2.29
2.27
2.78
2.83
2.74
2.76
2.84
3.42
2.75
2.92
2.82
2.80
2.82
2.77
85.80
88.3
3.46
3.58
3.47
3.49
3.44
4.17
3.45
3.55
3.50
ꢁ28.1
ꢁ12.3
ꢁ9.4
ꢁ9.4
ꢁ3.0
ꢁ2.6
ꢁ10.2
ꢁ6.8
ꢁ5.6
v. w. AF
7.6
[17]
[17]
[18]
Br
Br
Cl
Cl
Cl
NSCN
ONO
OHCOO
ONO
87.11
87.01
84.14
91.72
86
[18]
*
1ꢀH2O
E
F
G
H
I
[44]
[19]
[45]
[45]
[46]
[47]
[17,48]
85.5
2
86.34
99.79
86.54
85.83
3
J
K
ONO
ONO
3.52
3.45
3
13.8
3
*
This work. A: [{Cu(LI)I}2] (HLI = pyridine-2-carbaldehyde thiosemicarbazone); B: [{Cu(LImm)Br}2] (HLImm = pyridine-2-carbaldehyde (N(4)-methyl)
thiosemicarbazone); C: [{CuBr(LI)}2]; D: [{CuCl(LI)}2]; E: [Cu2Cl2( -S-dept)2][Cu2Cl4(
l
l
-Cl)2] (S-dept = (N,N,N0,N0-tetraethyl) pyridine-2,6-dithiocarboxam-
ide); F: [{Cu(NCS)(LI)}2]; G: [{Cu(LI)(NO2)}2]; H: [{Cu(LI)(HCOO)}2]; I: [Cu(mpsme)(ONO2] (Hmpsme = 6-methyl-2-formylpyridine Schiff base of S-
methyldithiocarbazate); J: [Cu2(L)2(NO3)2][Cu(L)(NO3)] (HL = 2-S-methyl-6-methyl-4-formyl pyrimidine-(N(4)-ethyl)-thiosemicarbazone); K: [{Cu(LImm)
NO3}2].
a
d(Cu–Sbasal).
d(Cu–Sapical).
b
distance in the range 2.3–3.0 Å. In all cases the calculated interac-
tion is ferromagnetic, with J1 values in the range +33.1 to
+3.0 cmꢁ1, for a shorter and longer distance, respectively. These re-
sults are in agreement with the calculations carried out previously
for a similar compound reported in Ref. [47].
The sign of this interaction can be rationalized using the Hay–
Thibeault–Hoffmann model [50]; the magnetic coupling constant
can be expressed as a sum of two contributions, ferromagnetic
and antiferromagnetic ones, J = JF + JAF. The quasi parallel disposi-
tion of the dx2
magnetic orbitals (basal planes of the square pyr-
ꢁy2
amid) can be translated in a poor overlap between these orbitals,
and consequently the antiferromagnetic contribution must be
close to zero, the ferromagnetic one dominating. As the angle be-
tween squares planes of the Cu(II) ions in the dinuclear compound
is 2.5°, we can expect that due to shortening of the Cu–S distance,
the antiferromagnetic term changes very little (poor overlap in all
cases), while the ferromagnetic one increases, as we have found in
the DFT calculation.
Thus, contrary to our experimental results, these calculations
indicate that the magnetic interaction in the dinuclear complex
must be ferromagnetic. As discussed in the X-ray crystal structure
section, several hydrogen bonds are present in the lattice, intramo-
lecular O–Hꢀ ꢀ ꢀCl and intermolecular O–Hꢀ ꢀ ꢀOw, N–Hꢀ ꢀ ꢀOw and N–
Hꢀ ꢀ ꢀCl interactions, generating a 3D-network, which could provide
pathways for the magnetic exchanges. Taking into account these
facts, we selected four additional models from the crystal structure
data to analyze independently each interaction. Model 2 (Fig. 6)
considers the stacking between the dinuclear complexes; for the
calculation of the magnetic exchange in this direction (J2), only
one [CuLCl] fragment of each dinuclear complex was considered.
Model 3 considers the interaction of two dinuclear complexes
through the hydrogen bonds with the water molecule (J3)
(Fig. 7). Model 4 analyzes the effect of the Clꢀ ꢀ ꢀH–N hydrogen bond
interaction (J4) (Fig. 8), and model 5 the effect of the Clꢀ ꢀ ꢀO interac-
tion (J5) (Fig. 9). As in the case of model 2, the calculations for other
models also were performed using only one [CuLCl] fragment of
each dinuclear complex. The magnetic coupling constants calcu-
lated with each model (J2, J3, J4 and J5) correspond to the intermo-
lecular exchange pathways, while J1 describes the intra-dimer
interaction in the dinuclear complex, which, as already indicated
above, is ferromagnetic (J1 = +5.0 cmꢁ1).
Fig. 6. Structural representation of the trinuclear model showing the exchange
coupling constants J1 and J2. Multiband cylinder bonds indicate the longer distance
in dinuclear entity Cu–S (2.86 Å) (model 1).
show antiferromagnetic (G, H, I) or ferromagnetic (J, K) behavior.
As was reported for other types of complexes, in some cases, the
nitrate ligand could act as a
p-acid ligand and as a consequence
could decrease the antiferromagnetic contribution [49].
Compound 1ꢀH2O shows a weak antiferromagnetic behavior,
the coupling constant being smaller than those reported for the
other compounds with monoatomic monodentate ligands (A–D).
In this case the distortion of the square-pyramid towards trigonal
bipyramid is negligible, and in consequence the overlap through
the bridge must be very poor, and a ferromagnetic behavior is ex-
pected. With the aim of understanding the observed antiferromag-
netic behavior, density functional calculations using the
experimental coordinates of this compound were performed (mod-
el 1, Fig. 6) and the obtained J1 value was +5.0 cmꢁ1. This result,
although in contradiction to the observed behavior, is expected
due to the apical equatorial nature of the bridging atoms. It is nec-
essary to take into consideration other factors to explain the exper-
imental results.
In an attempt to understand the influence of the Cu–S distance
on the exchange coupling parameter J1, we have varied this
For all models, we have obtained small negative values, indica-
tive of antiferromagnetic contributions. The calculated values are,

S. Naskar et al. / Polyhedron 35 (2012) 77–86
83
Fig. 7. Molecular structure representation and exchange coupling constant (J3) of dinuclear entity connected via hydrogen bonds. Multiband cylinder bonds indicate the
hydrogen bond (Hꢀ ꢀ ꢀOꢀ ꢀ ꢀH) in the dinuclear model.
Fig. 8. Structural representation of the trinuclear model showing the exchange coupling constant J4 between dinuclear entities (model 4). Multiband cylinder bonds indicate
the ClꢀꢀꢀH hydrogen bonds between the adjacent copper monomers.
Fig. 9. Molecular structure representation and exchange coupling constant (J5) of dinuclear entity connected via Cl–O contacts. Multiband cylinder bonds indicate the Clꢀ ꢀ ꢀO
contacts in the dinuclear entity.
J2 = ꢁ0.4 cmꢁ1, J3 = ꢁ0.1 cmꢁ1, J4 = ꢁ3.8 cmꢁ1 and J5 = ꢁ2.1 cmꢁ1
.
order to evaluate the effect of the nuclearity in the previous Ji val-
ues we carried out two new calculations, with three [CuLCl] frag-
ments (trinuclear models):
The magnetic behavior for this compound must be the sum of all
the interactions: intramolecular (J1 = +5.0 cmꢁ1) and intermolecu-
lar (J2 + J3 + J4 + J5 = ꢁ6.4 cmꢁ1), which gives a net antiferromagnetic
coupling. This result is in agreement with the sign of the coupling
constant found fitting the experimental data (ꢁ2.97 cmꢁ1).
(a) A modification of model 1 and model 2: We considered one
dinuclear complex, with J1, and their interaction with the
[CuLCl] fragment of a neighbor stacked dinuclear complex,
with a J2 interaction (Figs. 6 and 10).
As it was indicated, the calculations carried out with these mod-
els considered only two [CuLCl] fragments of different entities. In

84
S. Naskar et al. / Polyhedron 35 (2012) 77–86
2000
2500
3000
3500
4000
H / G
Fig. 12. X-band EPR spectrum, on polycrystalline sample of 1ꢀH2O, at 70 K.
Fig. 10. Spin-density distribution for trinuclear model corresponding to the S = 1/2
ground-state single-determinant B3LYP solution. Positive and negative values are
represented as white and dark surfaces, respectively.
Table 5
Experimental EPR parameters for compounds with a [Cu2(
pyramidal environment of the Cu(II) ions, sharing a base to apex edge.
l
-S)2] core and square-
giso
g||
g\
g1
g2
g3
Ref.
A
B
C
D
2.074
[17]
[17]
[18]
2.152
2.161
2.183
2.043
2.057
2.053
2.031
2.033
2.033
[18]
*
1ꢀH2O
2.18
2.17
2.05
2.07
E
F
G
H
I
[44]
[19]
[45]
[45]
2.148
2.183
2.186
2.064
2.037
2.046
2.040
2.029
2.038
2.2215
2.054
[46]
J
2.09
[47]
K
2.186
2.049
2.025
[17,48]
*
This work.
explain the different magnetic exchange pathways present in the
compound 1ꢀH2O.
From these results we can conclude that the experimental anti-
ferromagnetic behavior is due to the combination of two interac-
tions having opposite signs for J values: a ferromagnetic Cuꢀ ꢀ ꢀCu
interaction through the sulfur atom in the dinuclear complex and
antiferromagnetic interactions due to the hydrogen bonds between
dinuclear complexes. The most important antiferromagnetic con-
tributions are the J4 and J5 coupling constants, revealing the impor-
tance of the Clꢁ ligands in the magnetic properties (Figs. 8, 9 and
11).
Taking into consideration these results, we performed a new fit
of the experimental data with the Bleaney–Bowers equation [43],
considering the intramolecular ferromagnetic interaction (J1) and
including the overall intermolecular interactions with a single
Fig. 11. Calculated DFT values of the different types of exchange coupling constants
for 1ꢀH2O and the variation of these values considering the nuclearity of the models
studied (see text).
parameter (J0) [51]. The best fit was obtained with J1 = 4.79 cmꢁ1
,
J0 = ꢁ4.29 cmꢁ1 and g = 2.09 (R = 9.28 ꢃ 10ꢁ5) (solid line in Fig. 5).
This result agrees with the conclusions from the DFT calculations,
showing the observed weak antiferromagnetic behavior is due to
the competition between the ferromagnetic interaction within
the dinuclear complex and the antiferromagnetic interactions be-
tween the dinuclear complexes.
(b) A modification of model 4: In this case we considered three
[CuLCl] fragments of three neighboring dinuclear complexes,
with a J4 interaction between them (Fig. 8).
The X-band EPR spectrum of a polycrystalline sample is shown
in Fig. 12. It shows two signals at g|| = 2.18 and g\ = 2.05, character-
istic of Cu(II) ions in a square pyramidal environment. These values
are similar to the reported values for analogous compounds
(Table 5).
The J1, J2 and J4 values obtained with these models (trinuclear
models) are basically the same as those found with the dinuclear
models (models 1,2,4), with a decrease between 0.1 and 0.3 cmꢁ1
(Fig. 11). Therefore, the dinuclear models are a good approach to

S. Naskar et al. / Polyhedron 35 (2012) 77–86
85
3.4. Electrochemistry
by Fundació Catalana per a la Recerca (FCR) and the Universitat de
Barcelona.
In the cyclic voltammetry experiments, the free ligand
dmoTSCH2 shows no redox activity up to 1.0 V (versus Ag/AgCl)
in DMSO with a Pt electrode. On the cathodic side, a quasi-revers-
Appendix A. Supplementary data
ible response is obtained at ꢁ0.81 V (
DEp = 280 mV). In the corre-
CCDC 800029 and 800031 contain the supplementary crystallo-
graphic data for dmoPhTSCH2 and [Cu(dmoTSCH)Cl]2ꢀH2O
(1ꢀH2O), 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, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.poly.2011.12.042.
sponding Zn(II) complex, we could detect no oxidative response
up to 1.0 V, but an irreversible reductive response is observed at
ꢁ0.85 V. Very similar behavior is observed with the dmoPhTSCH2
ligand.
The Cu(II) complex 1ꢀH2O in DMSO solution shows a Cu(III)/
Cu(II) couple at 0.28 V (180 mV); two reductive peaks observed
at ꢁ0.30 V (300 mV) and ꢁ1.13 V are assigned to the Cu(II)/Cu(I)
couple and a ligand based reduction, respectively (Supplementary
Figs. 5 and 6). The complex 2 in DMSO solution shows the Cu(III)/
Cu(II) couple at 0.28 V (248 mV), while on the reductive side the
Cu(II)/Cu(I) couple is observed at ꢁ0.26 (260 mV) and the ligand
based reduction at ꢁ0.65 (100) V (Supplementary Fig. 7). It has
been pointed out that Cu(II) thiosemicarbazone complexes having
a reversible Cu(II)/Cu(I) potential around ꢁ0.5 to ꢁ0.6 V are hypox-
ia selective, and hence may be used as imaging agents of hypoxic
tissues [15,16]. The E0 values of the Cu(II)/Cu(I) couple of our com-
plexes are more positive than the specified range mentioned above
and hence they are not expected to show hypoxia selectivity.
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SKC thanks AICTE, UGC and CSIR for financial assistance. Sumita
thanks CSIR for a SRF. SKC also thanks Mr. Manas Ghosh for doing a
part of the work during his PG project. We also acknowledge AICTE
for funding the purchase of a CH1106A potentiostat. The infra-
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(CTQ2009-07264/BQU and CTQ2008-06670C02-01/BQU) and to
the Comissió Interdepartamental de Recerca i Innovació Tecnològ-
ica de la Generalitat de Catalunya (CIRIT) (2009-SGR1454 and
2009SGR1459) for financial support. J. Tercero is grateful to the
Centre de Computació de Catalunya (CESCA) with a grant provided

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