Synthesis, characterization and crystal structures of nickel(II), palladium(II) and copper(II) complexes with 2-furaldehyde-4- phenylthiosemicarbazone

Article abstract of DOI:10.1016/j.poly.2012.12.030

2-Furaldehyde-4-phenylthiosemicarbazone (HL) and its nickel(II), palladium(II) and copper(II) complexes: [Pd(L)₂] (1), [Ni(L) ₂] (2), [Cu₂(L)₂(Et₃N) ₂(H₂O)₄ ](SO₄

Full text of DOI:10.1016/j.poly.2012.12.030

Polyhedron 51 (2013) 307–315
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Polyhedron
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Synthesis, characterization and crystal structures of nickel(II), palladium(II) and
copper(II) complexes with 2-furaldehyde-4-phenylthiosemicarbazone
d
e
a
Diana-Carolina Ilies a,b, Elena Pahontu c, , Sergiu Shova , Aurelian Gulea , Tudor Rosu
⇑
a Inorganic Chemistry Department, Faculty of Chemistry, University of Bucharest, 23 Dumbrava Rosie Street, 020462 Bucharest, Romania
b Organic Chemistry Department, Faculty of Pharmacy, University of Medicine and Pharmacy ‘‘Carol Davila’’, 6 Traian Vuia Street, 020956 Bucharest, Romania
c Inorganic Chemistry Department, Faculty of Pharmacy, University of Medicine and Pharmacy ‘‘Carol Davila’’, 6 Traian Vuia Street, 020956 Bucharest, Romania
d Institute of Macromolecular Chemistry ‘‘Petru Poni’’, 41A Grigore Ghica Voda Alley, 700487 Iasi, Romania
e Coordination Chemistry Department, Moldova State University, 60 Mateevici Street, 2009 Chisinau, Republic of Moldova
a r t i c l e i n f o
a b s t r a c t
Article history:
2-Furaldehyde-4-phenylthiosemicarbazone (HL) and its nickel(II), palladium(II) and copper(II) com-
plexes: [Pd(L)2] (1), [Ni(L)2] (2), [Cu2(L)2(Et3N)2(H2O)4 ](SO4) (3), [Cu2(L)2(Et3N)2(H2O)4 ](NO3)2 (4),
[Cu(L)2(H2O)2] (5), [Cu(L)(OAc)(H2O)] (6) were synthesized and characterized. The ligand has been char-
acterized by elemental analyses, IR, electronic, 1H NMR and 13C NMR spectroscopy. The bidentate nature
of the ligand is evident from the IR spectra.
The nickel(II), palladium(II) and copper(II) complexes have been characterized by different physico-
chemical techniques like molar conductivity, magnetic susceptibility measurements, electronic, infrared
and EPR spectral studies. For the copper(II) complexes metal–ligand bonding parameters have been eval-
Received 23 November 2012
Accepted 28 December 2012
Available online 7 January 2013
Keywords:
2-Furaldehyde-4-phenylthiosemicarbazone
Nickel(II) complex
Palladium(II) complex
Copper(II) complex
uated from the EPR spectra. These parameters indicate the presence out-of-plane
p bonding.
In addition, the structures of the ligand, nickel(II) and palladium(II) complexes have been determined
by single-crystal X-ray diffraction. These complexes crystallized into triclinic lattices with space group
ꢀ
P1. The metal ion is coordinated through the sulfur atom and the azomethine nitrogen atom.
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
thiophene-2- and furan-2-carbaldehyde thiosemicarbazone com-
plexes [6].
The coordination chemistry of thiosemicarbazones with S and N
donor atoms and their complexes with transition metal ions, which
commence with Jensen’s work [1] has been extensively investi-
gated [2]. Thiosemicarbazones as well as their metal derivatives
have many biochemical and pharmacological properties. Some of
the detected biological activities of the thiosemicarbazones and
their complexes with transition metal ions are antibacterial, anti-
fungal, antiarthritic, antimalarial, antitumor, antiviral and espe-
cially anti-HIV activity [3].
The 2-furaldehyde-4-phenyl thiosemicarbazone has formed cis
[Ni(HL)2] square planar complex [6] and [Th(HL)2(NO3)4] complex
[7].
This work is the result of our systematic studies in this field [8–
11]. In the present communication, we report the synthesis and
spectral studies of new mononuclear Ni(II), Pd(II) and Cu(II) com-
plexes with 2-furaldehyde-4-phenyl thiosemicarbazone. Reaction
of NiF2ꢀ4H2O with 2-furaldehyde-4-phenyl thiosemicarbazone in
methanol, led to the formation of trans [Ni(HL)2].
Thiosemicarbazones ligands based on aldehydes have generally
formed trans square planar complexes [4], while ketone based
thiosemicarbazones have formed only cis square planar complexes
[5].
2. Experimental
2.1. Materials
The substituents at C2 carbon appear to influence the geometry
of Ni(II) complexes. The effect of the substituents at the N1
nitrogen on the geometry of Ni(II) complexes is analyzed for
2-Furaldehyde (Aldrich) and 4-phenylthiosemicarbazide
(Merck)wereusedasreceived. ThemetalsaltsPdCl2ꢀH2O, NiF2ꢀ4H2O,
CuSO4ꢀ5H2O, Cu(NO3)2ꢀ3H2O, CuCl2ꢀ2H2O, Cu2(OAc)4ꢀ (H2O)2
(Merck) were used as supplied. Solvents used for the reactions were
purified and dried by conventional methods [12]. The ligand has
been prepared by the method reported earlier [13]. As an example
some characteristics of the ligand are summarized below.
⇑
Corresponding author.
E-mail addresses: ilies_diana@hotmail.com (D.-C. Ilies), elenaandmihaela@
yahoo.com (E. Pahontu).
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.12.030

308
D.-C. Ilies et al. / Polyhedron 51 (2013) 307–315
2.2. Synthesis of Schiff base 2-furaldehyde-4-phenylthiosemicarbazone
(HL)
Main IR peaks (KBr, cmꢁ1): (N4H) 3294;
m
m
(C@N1) 1601;
m
(C@S) + (CN) 1260; (C–S) 509; m
m
m
(C@N2) 1550. The complex is
soluble in DMF and DMSO, partially soluble in ethanol, methanol
To a solution of 4-phenylthiosemicarbazide (0.167 g, 1 mmol) in
ethanol (20 mL) was added slowly 2-furaldehyde (0.096 g, 1 mmol)
dissolved in ethanol (10 mL). The mixture was stirred for 2 h at
room temperature, then refluxed for 6 h and kept at 4 °C for five
days. The resulting precipitate of yellow-brown color was filtered,
washed with ethanol and recrystallized from methanol–ethanol
(1:1, v/v). Fine yellow-brown crystals obtained upon slow evapora-
tion at room temperature were characterized, including single
crystal X-ray diffraction.
and is insoluble in acetone, chloroform.
2.3.5. Synthesis of the complex [Cu(L)2(H2O)2] (5)
Green solid. Yield: 82%; M.p. 223–225 °C; M.wt.: 587.5; Anal.
Calc. for C24H24CuN6O4S2: C, 49.02; H, 4.08; N, 14.29; Cu, 10.80.
Found: C, 49.37; H, 3.86; N, 14.02; Cu, 10.52%.
Main IR peaks (KBr, cmꢁ1): (N4H) 3296;
m
m
(C@N1) 1596;
m
(C@S) + (CN) 1259; (C–S) 519; m
m
m
(C@N2) 1546. The complex is
soluble in DMF and DMSO, partially soluble in ethanol, methanol
Yield 87%; M.p. 149–150 °C; M.wt.: 245; Anal. Calc. for C12H11-
N3OS: C, 58.76; H, 4.52; N, 17.13. Found: C, 59.18; H, 4.22; N,
17.02%.
and chloroform.
2.3.6. Synthesis of the complex [Cu(L)(OAc)(H2O)] (6)
IR(KBr, cmꢁ1):
m
(N4–H) 3302,
m
(N2–H) 3128,
m
(C@N, st. intense)
Green-brown solid. Yield: 86%; M.p. >250 °C; M.wt.: 402.5; Anal.
Calc. for C14H17CuN3O5S: C, 41.73; H, 4.22; N, 10.43; Cu, 15.77.
Found: C, 41.97; H, 4.06; N, 10.18; Cu, 15.54%.
1619, (C@S) + (CN) 1272,
m
m
m
(N–N) 1015, m
(C@S) 735; 1H NMR
(DMSO-d6; d, ppm): d = 9.85 (s, 1H, H-5, CH@N); 7.63–7.56(m,
3H, H-2, 3, 4); 7.40–7.33(m, 5H, H-8, 9, 10, 11, 12); 13C NMR
(DMSO-d6; d, ppm): d = 159.40 (C-5); 150.9 (C-10); 134.32 (C-7);
131.32 (C-9,11); 121.62 (C-10); 118.75 (C-8,12);
Main IR peaks (KBr, cmꢁ1): (N4H) 3292;
m
m
(C@N1) 1601;
m
(C@S) + (CN) 1246; (C–S) 530; m
m
m
(C@N2) 1568. The complex is
soluble in DMF and DMSO, partially soluble in ethanol, methanol
and chloroform.
2.3. General procedure for the preparation of the metal complexes
(1–6)
2.4. Physical measurements
Complexes 1–6 were prepared by direct reaction between the
ligand and the corresponding metal salts.
C, H and N analyses were performed with the Carlo-Erba LA-118
microdosimeter whereas the AAS-1N Carl-Zeiss-Jena spectrometer
was used for the determination of Cu(II). Physico-chemical analy-
ses were performed after drying the complexes at 105 °C.
2.3.1. Synthesis of the complex [Pd(L)2] (1)
To a stirred solution of PdCl2ꢀ2H2O (2 mmol, 0.423 g) in ethanol
(15 mL) was added a solution of 2-furaldehyde-4-phenylthiose-
micarbazone (2 mmol, 0.490 g) in ethanol (20 mL) and 2–3 drops
of triethylamine (Et3N). The mixture was stirred for 3 h at room
temperature and refluxed for 5 h. The brown-reddish colored solid
was filtered, washed with hot water, then ethanol followed by
ether and dried in vacuo.
Infrared spectra (4000–400 cmꢁ1) were recorded on a Bruker
Vertex 70 spectrophotometer, using KBr pellets. The 1H NMR spec-
tra were recorded on a Bruker 400 DRX spectrometer in CDCl3 solu-
tion, using TMS as the internal standard. Diffuse reflectance spectra
were recorded on a Jasco V-670 spectrophotometer, using MgO
dilution matrices. Electron paramagnetic resonance (EPR) mea-
surements were performed on polycrystalline powders and solu-
tions DMSO, at room temperature and 77 K, with an MiniScope
MS200, Magnettech Ltd., X-band spectrometer (9.3–9.6 GHz), con-
nected to a PC equipped with a 100 kHz field modulation unit. The
g factors were quoted relative to the standard marker TCNE
(g = 2.00277). The magnetic susceptibility measurements were car-
ried at room temperature in the polycrystalline state on a Faraday
magnetic balance (home-made). The complexes were studied by
thermogravimety (TG) in static air atmosphere, with a sample
heating rate of 10 °C/min using a DuPont 2000 ATG thermo bal-
ance. The molar conductance of the complexes in dimethylform-
amide solutions (10ꢁ3 M), at room temperature, were measured
using a Consort type C-533 conductivity instrument.
Yield: 84%; M.p. >250 °C; M.wt.: 595; Anal. Calc. for C24H20PdN6-
O2S2: C, 48.40; H, 3.36; N, 14.11; Pd, 17.82. Found: C, 48.89; H,
3.07; N, 13.88; Pd, 17.57%.
Main IR peaks (KBr, cmꢁ1): (N4H) 3290;
m
m
(C@N1) 1598;
m
(C@S) + (CN) 1252; (C–S) 510; m
m
m
(C@N2) 1560. The complex is
soluble in DMF and DMSO, and is partially soluble in ethanol,
methanol and chloroform.
2.3.2. Synthesis of the complex [Ni(L)2] (2)
Brown-reddish solid. Yield: 72%; M.p. 249–250 °C; M.wt.: 547;
Anal. Calc. for C24H20NiN6O2S2: C, 52.65; H, 3.65; N, 15.35; Ni,
10.78. Found: C, 53.07; H, 3.27; N, 15.18; Ni, 10.52%.
Main IR peaks (KBr, cmꢁ1):
(C@S) + (CN) 1250; (C–S) 521;
m
m
(N4H) 3290;
m
(C@N1) 1600;
m
m
m
(C@N2) 1565. The complex is
2.5. X-ray crystallography
soluble in DMF and DMSO, and is partially soluble in ethanol,
methanol and chloroform.
Crystallographic measurements for (HL), 1 and 2 were carried
out with an Oxford-Diffraction XCALIBUR E CCD diffractometer
2.3.3. Synthesis of the complex [Cu2(L)2(Et3N)2(H2O)4 ](SO4) (3)
Reddish solid. Yield: 74%; M.p. 169–171 °C; M.wt.: 985; Anal.
Calc. for C36H58Cu2N8O10S3: C, 43.85; H, 5.88; N, 11.37; Cu, 12.89.
Found: C, 44.09; H, 5.46; N, 11.08; Cu, 12.62%.
equipped with graphite-monochromated Mo K radiation. The
a
crystals were placed 40 mm from the CCD detector. The unit cell
determination and data integration were carried out using the Cry-
sAlis package of Oxford Diffraction [14a]. All structures were
solved by direct methods using SHELXS-97 [14b] and refined by
full-matrix least-squares on Fo2 with SHELXL-97 [14b]. All atomic dis-
placements for non-hydrogen, non-disordered atoms were refined
using an anisotropic model. All H atoms attached to carbon were
introduced in idealized positions (dCH = 0.96 Å) using the riding
model with their isotropic displacement parameters fixed at
120% of their riding atom. Positional parameters of the H attached
to N atoms were obtained from difference Fourier syntheses and
verified by the geometric parameters of the corresponding
Main IR peaks (KBr, cmꢁ1): (N4H) 3290;
m
m
(C@N1) 1604;
m
(C@S) + (CN) 1246; (C–S) 555; m
m
m
(C@N2) 1552. The complex is
soluble in DMF and DMSO, partially soluble in ethanol, methanol
and is insoluble in acetone, chloroform.
2.3.4. Synthesis of the complex [Cu2(L)2(Et3N)2(H2O)4 ](NO3)2 (4)
Reddish solid. Yield: 79%; M.p. 170–172 °C; M.wt.: 1013; Anal.
Calc. for: C36H58Cu2N10O12S2: C, 42.64; H, 5.72; N, 13.82; Cu,
12.53. Found: C, 42.87; H, 5.52; N, 13.63; Cu, 12.32%.

D.-C. Ilies et al. / Polyhedron 51 (2013) 307–315
309
Table 2
hydrogen bonds. The main crystallographic data together with
Selected bond lengths (Å) and bond angles (°) of (HL) and 1, 2.
refinement details are summarized in Table 1. Selected bond
lengths and angles are presented in Table 2.
HL
1
2
A
B
A
B
S1–C6
1.679(2)
1.367(3)
1.346(3)
1.278(3)
1.339(3)
1.423(3)
1.383(3)
1.370(4)
1.432(3)
1.387(3)
1.342(3)
1.348(3)
1.374(4)
1.365(4)
1.396(4)
1.394(5)
1.422(5)
1.285(6)
1.735(2)
1.397(2)
1.297(3)
1.298(3)
1.365(3)
1.405(2)
1.383(3)
1.390(3)
1.428(3)
1.367(3)
1.378(2)
1.349(3)
1.378(3)
1.368(3)
1.380(3)
1.355(3)
1.405(3)
1.333(3)
2.2794(6)
2.027(2)
83.18(6)
96.82(6)
1.737(2)
1.388(2)
1.297(3)
1.296(3)
1.370(3)
1.403(3)
1.384(3)
1.379(3)
1.425(3)
1.377(3)
1.380(2)
1.349(3)
1.369(3)
1.382(3)
1.375(3)
1.350(3)
1.403(3)
1.330(3)
2.2909(6)
2.025(2)
82.58(6)
97.42(6)
1.735(2)
1.396(3)
1.294(3)
1.302(3)
1.368(3)
1.402(3)
1.391(3)
1.394(3)
1.420(3)
1.372(3)
1.380(3)
1.357(3)
1.388(3)
1.382(3)
1.378(3)
1.348(3)
1.406(3)
1.332(4)
2.1725(7)
1.919(2)
85.16(6)
94.84(6)
1.744(2)
1.400(3)
1.301(3)
1.304(3)
1.364(3)
1.409(3)
1.385(3)
1.389(3)
1.430(3)
1.382(4)
1.373(3)
1.350(3)
1.385(4)
1.370(4)
1.386(4)
1.354(3)
1.416(3)
1.338(4)
3. Results and discussion
N2–N1
N2–C6
N1–C5
C6–N3
N3–C7
C7–C8
C7–C12
C5–C1
C8–C9
C1–O1
C1–C2
C9–C10
C10–C11
C11–C12
O1–C4
The Schiff base (HL) was synthesized in ethanol in good yield.
The structure of formed ligand was established by IR, 1H NMR
and 13C NMR spectroscopy and by X-ray crystallography.
All complexes were synthesized by direct reaction of the inor-
ganic salt solutions with the ligand solution. The obtained com-
plexes are microcrystalline solids which are stable in air and
have melting points above 169–250 °C. They are insoluble in or-
ganic solvents such as acetone, chloroform, partially soluble in eth-
anol, methanol, but soluble in DMF and DMSO. The synthesis of the
complexes is reproducible and the thiosemicarbazone coordinates
as a bidentate ligand. The molar conductivity values (6–10 Xꢁ1
cm2 molꢁ1) of the complexes 1, 2, 5, 6 in 10ꢁ3 M solution DMF
-
C3–C2
C3–C4
M1–S1
M1–N1
N1–M–S1
N1–M– S1(i)
show that they are non-electrolytes and 3, 4 (82 and 103
X
ꢁ1 cm2 -
2.1814(7)
1.909(2)
85.17(6)
94.83(6)
molꢁ1) are electrolytes [15]. Thermogravimetric analyses show
that four water molecules are directly bound to the metal center
in the complexes 3, 4 and two water molecules in 5, 6.
–
–
The elemental analyses data of the Schiff base and complexes
(reported in Section 2) are in agreement with structure of the li-
gand (Scheme 1) and with structures of the complexes (Scheme 2).
Symmetry code: (i) 1 ꢁ x, 1 ꢁ y, 1 ꢁ z for molecule A, ꢁx, 1 ꢁ y,1 ꢁ z for molecule B.
11
9
12
1
N
H 5
C
4
N
H
3.1. Structural characterization of (HL), [Pd(L)2] (1) and [Ni(L)2] (2)
10
7
4
2
O
C
N
8
Suitable crystals of (HL), [Pd(L)2] (1) and [Ni(L)2] (2), for single
crystal X-ray study were grown from acetonitrile, by slowly evap-
orating. The single crystal X-ray study has revealed that all the
compounds have molecular structure built of the neutral entities
depicted in Figs. 1, 3 and 4.
H
'
1
3
S
2
Scheme 1. Schiff base ligand (HL).
The main crystal packing motif of (HL) consists of 1D supramo-
troid distance between centrosymmetrically related phenyl rings
equal to 4.215 Å, as depicted in Fig. 2.
lecular chains sustained by N–Hꢀ ꢀ ꢀS hydrogen bonds and
p–p
stacking interactions, which is evidenced by short centroid-to-cen-
Table 1
Crystallographic data, details of data collection and structure refinement parameters for (HL), 1 and 2.
Compound
(HL)
1
2
Empirical formula
Molecular weight
T (K)
C
12H11N3OS
C24H20PdN6O2S2
594.98
293(2)
C24H20N6NiO2S2
547.29
200(1)
245.3
293(2)
k (Å)
Mo Ka
; 0.71073
Mo Ka
; 0.71073
Mo Ka; 0.71073
Crystal system
Space group
a (Å)
b (Å)
c (Å)
triclinic
P1
triclinic
P1
triclinic
P1
ꢀ
ꢀ
ꢀ
5.8162(5)
9.8481(10)
11.1495(9)
71.429(8)
83.206(7)
88.717(8)
601.04(9)
2
9.9327(6)
12.9458(5)
12.9458(5)
78.536(4)
68.539(5)
70.810(5)
1191.77(11)
2
9.4901(9)
10.2419(18)
11.9520(14)
90.646(12)
95.522(9)
92.142(11)
1155.4 (3)
2
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (g/cm3)
1.355
0.256
1.658
0.989
1.573
1.057
l
(mmꢁ1
)
F(000)
256
600
564
hmin, h
Crystal size (mm)
(°)
6.7 to 52
0.20 ꢂ 0.20 ꢂ 0.15
3880/2350 [Rint = 0.0199]
0.42/ꢁ0.41
0.0531
6.54 to 52
0.25 ꢂ 0.15 ꢂ 0.15
12851/46526 [Rint = 0.0295]
0.39/ꢁ0.25
0.0247
5.76, 52.00
0.20 ꢂ 0.02 ꢂ 0.01
9423/4545 [Rint = 0.0258]
0.32/ꢁ0.31
0.0375
max
Reflections collected/unique
D
qmax and D ]
qmin [e Åꢁ3
R1a[I > 2
r
(I)]
b
wR2 (all data)
0.1597
1.081
0.0404
0.913
0.0853
1.019
GOFc
a
b
c
R1
wR2 = {
GOF = {
=
R
||Fo| ꢁ |Fc||/
R|Fo|.
[w (Fo2 ꢁ Fc2)2]/
R[w(Fo ) .
]}1/2
2
2
R
[w(Fo ꢁ Fc2)2]/(n ꢁ p)}1/2, where n is the number of reflections and p is the total number of parameters refined.
2
R

310
D.-C. Ilies et al. / Polyhedron 51 (2013) 307–315
NH
C
R
N
N
S
S
OH2
Cu
N
O
R
N
C
H
OH2
R
H
C
H2O
R
O
X
Cu
N
n
R
OH2
R
N
C
HN
R = C2H5
X = SO42 n = 1
;
X = NO3
; n = 2
3, 4
N
S
H
N
S
H
C
N
C
N
X
N
CH
X
N
CH
O
Cu
O
Cu
O
O
X
O
C
S
N
N
HC
X
N
C
H
H3C
X = H
2O
X = H
2O
5
6
Scheme 2. Proposed structures of the metal complexes.
The crystal structure motif of compound 2 can be characterized
as a 3D supramolecular network, sustained by multiple C–Hꢀ ꢀ ꢀO
hydrogen bonds and
p–p stacking interactions. The fragment of
3D supramolecular architecture is shown in Fig. 5. The centrosym-
metrically related A and B crystallographic independent furane
rings are stacked separately with the centroid-to-centroid dis-
tances of 3.671 Å and 4.019 Å, respectively. It is noteworthy, that
no any short intermolecular contacts involving N–H groups have
been detected.
Molecular complexes A and B in crystal structure 3 are associ-
ated into the infinite chains along crystallographic axis a through
N3A–Hꢀ ꢀ ꢀS1Bi hydrogen bond as depicted in Fig. 6. The second
NH group from molecule B does not participate into the hydrogen
bond formation, the intermolecular separation between N1B and
S1A(ii) atoms is equal to 4.21 Å.
Fig. 1. Perspective view of the (HL) molecule, along with atom numbering scheme.
Thermal ellipsoids are drawn at 50% probability level.
The asymmetric units of 2 and 3 each contain two crystallo-
graphically independent half molecules (denoted as A and B). In
each case the metal ions sit on inversion centers and thus each
monomer is centrosymmetric, as depicted in Figs. 3 and 4. The cen-
tral ions have a square-planar coordination environment provided
by two monodeprotonated bidentate ligands, which exhibit typical
(N2S2) coordinating behavior for thiosemicarbazone moieties [16],
resulting into the formation of the five-membered chelate ring.
The monodeprotonated bidentate ligand shows a cis-configura-
tion for the N1 and S1 atoms. In the free ligand, these fragments
presents a trans-configuration, indicating that the complexation
occurs after an 180° rotation around the C6–N2 and N1–N2 bond,
Fig. 1. The comparison analysis of the bonds lengths for protonated
ligand in free form and deprotonated in coordinated form (Table 2)
confirm the delocalization of the electron density within thiosem-
icarbazone moiety [17].
3.2. Infrared spectra and coordination mode
The infrared spectral data of the ligand and metal complexes are
reported in Section 2. The IR spectra of the complexes are com-
pared with that of the free ligand to determine the changes that
might occur during complex formation. The proposed assignments
are based on previous results [8–11] and pertinent references
[6,7,18]. The strong band at 3304 cmꢁ1 in the spectrum of (HL)
has been assigned to m
(N4H). In the complexes this band is shifted
downwards by 8–12 cmꢁ1, suggesting differences in hydrogen
bonding of N4H between the uncomplexed and complexed thio-
semicarbazone [18]. The band at 3128 cmꢁ1 in the spectrum of free
ligand due to m
(N2H) vibration disappears in the spectra of all com-
plexes, providing a strong evidence for the ligand coordination
around Cu(II) ion in the deprotonated form [19].

D.-C. Ilies et al. / Polyhedron 51 (2013) 307–315
311
Fig. 2. View of 1D chain in crystal structure of (HL). The S1 atom acts as proton acceptor towards N2 atom: N2–Hꢀ ꢀ ꢀS1 [N2–H 0.860, Hꢀ ꢀ ꢀS1 2.523, N2ꢀ ꢀ ꢀS1 3.363(4) Å, N2–
Hꢀ ꢀ ꢀS1 165.4° (ꢁx + 1, ꢁy + 1, ꢁz + 1)].
Fig. 3. X-ray molecular structure of two independent [PdL2] complexes along with the atom numbering scheme. Thermal ellipsoids are drawn at 50% probability level.
Symmetry codes: (i) 1 ꢁ x, 1 ꢁ y, 1 ꢁ z; (ii) ꢁx, 1 ꢁ y, 1 ꢁ z.
Fig. 4. View of the asymmetric part of the unit cell in the crystal structure of [NiL2] along with the atom numbering scheme. Thermal ellipsoids are drawn at 50% probability
level. Symmetry codes: (i) ꢁx, 1 ꢁ y, 2 ꢁ z; (ii) 1 ꢁ x, 1 ꢁ y, ꢁz.

312
D.-C. Ilies et al. / Polyhedron 51 (2013) 307–315
Fig. 5. View of 3D supramolecular network in the crystal structure 2. H-bond parameters: C4A–Hꢀ ꢀ ꢀO1B [C4A–H 0.93 Å, Hꢀ ꢀ ꢀO1B 2.72 Å, C4Aꢀ ꢀ ꢀO1B(i) 3.326(3) Å,
C4A–Hꢀ ꢀ ꢀO1B 123.8°]; C4B–Hꢀ ꢀ ꢀO1A [C4B–H 0.93 Å, Hꢀ ꢀ ꢀO1A 2.81 Å, C4Bꢀ ꢀ ꢀO1A(i) 3.396(3) Å, C4B–Hꢀ ꢀ ꢀO1A 122.3°] Symmetry codes: (i) ꢁx, ꢁy, 1 ꢁ z. (ii) 1 ꢁ x, ꢁy, 1 ꢁ z.
Fig. 6. H-bonded infinite chain in the crystal structure [Ni(L)2]. Non relevant hydrogen atoms are omitted for clarity. Inermolecular H-bond N3A–Hꢀ ꢀ ꢀS1B [N3A–H 0.86 Å,
Hꢀ ꢀ ꢀS1B 2.90 Å, N3Aꢀ ꢀ ꢀS1B(i) 3.618(2) Å, N3A–Hꢀ ꢀ ꢀS1B 141.8°] is also shown. Symmetry codes: (i) 1 ꢁ x, 1 ꢁ y, 1 ꢁ z; (ii) x ꢁ 1, y, z.
The intense band in the spectrum of ligand at 1619 cmꢁ1 has
been assigned to (C@N) of the thiosemicarbazone moiety. In the
3.3. Electronic spectra
m
spectra of the respective complexes this band is shifted to lower
frequency by ca.15–25 cmꢁ1, suggesting the coordination of the
azomethine nitrogen to the metal center [20].The bands at the fre-
The significant electronic absorption bands in the spectra of the
ligand and all the complexes, in solid state are presented in Table 3.
The energy values of the d–d transitions suggest a square planar
geometry for complexes 1 and 2 and an octahedral distorted geom-
etry for complexes 3–6 [24]. The electronic spectrum of ligand
show the following intraligand absorption maxima, corresponding
quencies 1272 cmꢁ1 (CN)] and 735 cmꢁ1, respectively, in
[m(CS) + m
the spectrum of (HL) have been shifted to lower frequencies in the
range 1246–1260 and 745–756 cmꢁ1, respectively, indicating coor-
dination of the thiolato sulfur [21].
to
p ?
p⁄ and n ? p⁄ transitions: 37040 cmꢁ1 and 27030 cmꢁ1
For the complex 3 bands at 1090, 950 and 620 cmꢁ1 are assign-
[18d,25]. These bands are slightly shifted, to lower energies, in
able to m3, m1 and m4 of the non-coordinated sulfato group [18,22].
the complexes.
The nitrate complex 4 shows a single band at ca. 1385 cmꢁ1. It is
The electronic spectra of complexes 1 and 2 show three spin-
allowed bands. These absorption bands may be assigned to the
ꢁ
attributable to ionic NO3 [23]. The acetate complex 6 has two
strong bands at 1494 and 1428 cmꢁ1, corresponding to mas (COOꢁ)
3B1g(F) ? 3B2g(F), B1g(F) ? 3A2g(F), B1g(F) ? 3A2g(P) transitions,
respectively, and reflect d8 ions in an square planar geometrical
environment [24,26b]. The magnetic moment values (3.55,
3.48 BM), correspond to two unpaired electrons per metal ion.
3
3
and
mas (COOꢁ) and
the bidentate nature of the coordinated acetate [18,23].
m
s(COOꢁ), respectively. The difference between frequencies
[
m
s(COOꢁ) ] = 66 cmꢁ1. This difference confirms

D.-C. Ilies et al. / Polyhedron 51 (2013) 307–315
313
Table 3
Electronic spectral assignments (cmꢁ1) of (HL) and 1–6 complexes.
Compound
Transitions d–d (cmꢁ1
)
leff MB
Geometry
3B1g (F) ? 3B2g(F)
3B1g(F)?3A2g(F)
3B1g(F) ? 3A2g(P)
[Pd(L)2] (1)
[Ni(L)2] (2)
14500
15000
18860
18340
–
3.55
3.48
square planar
square planar
27 740
2B1g
?
2A1g
2B1g
?
2B2g
2B1g 2Eg
?
[Cu2(L)2(Et3N)2 (H2O)4](SO4) (3)
[Cu2(L)2(Et3N)2(H2O)4](NO3)2 (4)
[Cu(L)2(H2O)2] (5)
10750
10870
10990
10750
14450
14590
14490
14280
17540
17860
16940
–
1.28
1.37
1.93
2.01
octahedral distorted
octahedral distorted
octahedral distorted
octahedral distorted
[Cu(L)(OAc)(H2O)2] (6)
The electronic spectra of complexes 3–6 show d–d bands in the
regions 10750–10990, 14280–14590 and 16940–17860 cmꢁ1
which may be assigned to 2B1g ? 2A1g, 2B1g ? 2B2g, 2B1g ? 2Eg tran-
sitions, respectively, due to the distorted octahedral geometry
[24,26]. The values of leff (1.93, 2.01 BM) for complexes 5, 6 sug-
gest the presence of an unpaired electron. Also, it indicates the
existence of monomeric species of copper(II).
The subnormal magnetic moment values (1.28, 1.37 BM) for
complexes 3 and 4 indicates that the copper centers are antiferro-
magnetically coupled [26,27].
3.4. EPR spectra
The EPR spectral parameters of the Cu(II) complexes 3–6 in the
polycrystalline state at 298 K and in DMSO solution at 298 and
77 K are presented in Table 4. The EPR spectra of the complexes re-
corded in the polycrystalline state provide information about the
coordination environment around copper(II). The spectra of the
compounds 3–6 show typical axial behavior with slightly different
g// and g\ values. In these Cu(II) complexes, tensor values of
g// > g\ > 2.002 are consistent with a dx2ꢁy2 ground state [28].
For complexes 3 and 4 we got a half field signal at g = 4.178 and
4.184, respectively, indicating dimeric species [29,30], Fig. 7.
The geometric parameter G is a measure of the exchange inter-
action between copper centers in a polycrystalline compound. It is
calculated using the equation G = (g// ꢁ 2)/(g\ ꢁ 2) for axial spec-
tra. G values less than 4.0 indicate a small exchange coupling (com-
plexes 3, 4). If G is higher than 4.0, the exchange interaction is
negligible (complexes 5, 6) [31].
Fig. 7. EPR spectra of 3 and 4 in the polycrystalline state at 298 K and 77 K.
The spectra of complexes 3–6, in DMSO solution at 77 K, shows
a typical distorted octahedral geometry and hyperfine splitting
into four lines. In Fig. 8 are given EPR spectra of complexes 3 and
4, in DMSO solution at 77 K. These show four well defined hyper-
fine lines in the parallel region corresponding to the electron
spin–nuclear spin interaction. In addition the spectra of the com-
Table 4
EPR spectral parameters of the metal complexes 3–6.
3
4
5
6
Polycrystalline (298 K)
g//
g\
2.132
2.035
2.228
2.059
2.236
2.034
2.370
2.027
DMSO (77 K)
g//
g\
A//
a2
b2
d2
2.222
2.096
177
0.791
0.874
0.985
0.693
0.779
2.228
2.070
176
0.783
0.899
0.850
0.705
0.666
2.390
2.078
177.3
0.949
0.969
0.746
0.920
0.708
2.262
2.075
160
0.772
0.984
0.889
0.748
0.687
Fig. 8. EPR spectra of 3 and 4 in DMSO solution at 77 K.
plexes 3–5 show five nitrogen superhyperfine lines in the high field
component and three lines for complex 6, Fig. 9.
K//
K\
The EPR parameters g//, g\, A// and the energies of the d–d tran-
sition were used to evaluate the bonding parameters a
2, b2 and d2.

314
D.-C. Ilies et al. / Polyhedron 51 (2013) 307–315
financially supported by European Regional Development Fund,
Sectoral Operational Program ‘‘Increase of Economic Competitive-
ness’’, Priority Axis 2 (SOP IEC-A2-O2.1.2-2009- 2, ID 570, COD
SMIS-CSNR: 12473, Contract 129/2010-POLISILMET.
Appendix A. Supplementary data
CCDC 810821 (HL), CCDC 810820 (1), CCDC 887390 (2) contain
the supplementary crystallographic data for this contribution.
These data can be obtained free of charge via http://www.ccdc.ca-
m.ac.uk/conts/retrieving.html (or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: (+44) 1223 336 033; or deposit@ccdc.ca.ac.uk).
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