Copper(II) and nickel(II) complexes with two new bis(thiosemicarbazone) ligands: Synthesis, characterization, X-ray crystal structures and their electrochemistry behavior

Article abstract of DOI:10.1016/j.ica.2014.12.011

Two new bis(thiosemicarbazone) ligands 2-[1-(2-[3-[2-([2-[(4-chloroanilino)carbothioyl]hydrazono]methyl)phenoxy]propoxy]phenyl)methylidene]-N¹-(4-chlorophenyl)-1-hydrazinecarbothiamide (H₂L1) and 2-[1-(2-[3-[2-([2-[(4-chloroanilino)c

Full text of DOI:10.1016/j.ica.2014.12.011

Accepted Manuscript
Copper(II) and nickel(II) complexes with two new bis(thiosemicarbazone) li-
gands: synthesis, characterization, X-ray crystal structures and their electro-
chemistry behaviour
Seyed Abolfazl Hosseini-Yazdi, Sara Hosseinpour, Ali Akbar Khandar, W.
Scott Kassel, Nicholas A. Piro
PII:
S0020-1693(14)00749-X
http://dx.doi.org/10.1016/j.ica.2014.12.011
ICA 16337
DOI:
Reference:
To appear in:
Inorganica Chimica Acta
Received Date:
Revised Date:
Accepted Date:
16 October 2014
7 December 2014
14 December 2014
Please cite this article as: S.A. Hosseini-Yazdi, S. Hosseinpour, A.A. Khandar, W. Scott Kassel, N.A. Piro,
Copper(II) and nickel(II) complexes with two new bis(thiosemicarbazone) ligands: synthesis, characterization, X-
ray crystal structures and their electrochemistry behaviour, Inorganica Chimica Acta (2014), doi: http://dx.doi.org/
1
0.1016/j.ica.2014.12.011
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Copper(II) and nickel(II) complexes with two new bis(thiosemicarbazone)
ligands: synthesis, characterization, X-ray crystal structures and their
electrochemistry behaviour
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a,*
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Seyed Abolfazl Hosseini-Yazdi , Sara Hosseinpour , Ali Akbar Khandar , W. Scott
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Kassel , Nicholas A. Piro
a
Department of Inorganic Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz
51666-14766 Iran
Department of Chemistry, Villanova University, 800 Lancaster Avenue, Villanova, PA,
19085, USA
b
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*
Corresponding author: Seyed Abolfazl Hosseini-Yazdi (hosseiniyazdi@yahoo.com)
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Abstract
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Two new bis(thiosemicarbazone) ligands 2-[1-(2-{3-[2-({2-[(4-chloroanilino)carbothioyl]
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hydrazono}methyl)phenoxy]propoxy}phenyl)methylidene]-N -(4-chlorophenyl)-1-
hydrazinecarbothiamide
(H L1)
and
2-[1-(2-{3-[2-({2-[(4-
2
chloroanilino)carbothioyl]hydrazono}methyl)phenoxy]-2-hydroxypropoxy}phenyl)
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methylidene]-N -(4-chlorophenyl)-1-hydrazinecarbothiamide (H L2) were synthesized and
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characterized by FT-IR spectroscopy, HNMR spectroscopy and elemental analysis. Their
nickel(II) and copper(II) complexes were prepared and characterized by UV-Vis
spectroscopy, FT-IR spectroscopy, elemental analysis and single-crystal X-ray diffraction.
Both ligands lose hydrazinic hydrogen atoms upon coordination and act as dianionic
tetradentate donors. In [NiL1].EtOH and [CuL1].MeOH complexes metal centers are
coordinated by two imine nitrogen atoms and two sulfur atoms with a distorted square planar
coordination geometry. The geometrical distortion from square planar in the copper complex
is greater than in the nickel complex. Cyclic voltammetry studies of Cu(II) and Ni(II)
complexes in DMF show that all complexes able to stabilize low oxidation states of Cu(I) and
Ni(I).
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Keywords: Nickel; Copper; Bis(thiosemicarbazone); Schiff base; Cyclic Voltammetry
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1. Introduction
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Metal complexes of thiosemicarbazone and bis(thiosemicarbazone) ligands have a wide range
of biological activities including antibacterial [1], antifungal [2], antiviral [3], antimalarial
[4,5] and antitumor [6-8] activities. Some reactivities of copper and nickel complexes are
dependent on stabilization of unusual oxidation states of metals such as potential of copper
complexes as radiopharmaceuticals for the specific targeting of hypoxic tissue [9-12] and as
superoxide dismutase-like radical scavengers [13]. Also, in nickel containing enzymes such
as hydrogenase unusual oxidation states of nickel are involved [14]. Therefore, model
complexes for stabilization of nickel and copper in lower oxidation state than its normal +2
are of interest [15-18]. Electrochemical reactivity of complexes is strongly influenced by the
nature and number of various types of donor atoms. Thiosemicarbazone and
bis(thiosemicarbazone) ligands with soft donor atoms such as N of imine and S of thiolate
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with ζ-donor and π-acceptor properties can stabilize the Ni and Cu states [15]. In this paper,
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we report the synthesis, structure, and spectral and electrochemical properties of Cu N S and
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Ni N S coordination environments. Furthermore, the subtle change of introducing hydroxyl
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group to the coordination sphere and electrochemical behaviours of copper and nickel
complexes of these ligands were investigated.
2. Experimental
2. 1. Materials
2-[3-(2-formyl phenoxy)propoxy]benzaldehyde (3) and 2-[3-(2-formylphenoxy)-2-
hydroxypropoxy]benzaldehyde (4) were prepared according to literature methods [19-21].
Other reagents and solvents were obtained from Alfa Aesar and Merck and were used as
received.
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2.2. Physical Measurements
NMR spectra were recorded on Bruker Avance 400 in DMSO-d solvent and chemical shifts
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are relative to residual solvent protons as internal standard at room temperature. Elemental
analyses were performed on Elementar Vario EL III. FT-IR spectra were recorded on a FT-IR
–
1
Spectrometer Bruker Tensor 27 in the region 4000-400 cm using KBr pellets. Electronic
absorption spectra were recorded with an Analytick Jena Specord 250 in the region 230-1100
nm. Melting points were obtained with an Electrothermal 9100 and are uncorrected.
Electrochemical studies were performed using a glassy carbon as working electrode, a
platinum wire auxiliary electrode, and an Ag/AgCl reference electrode. The
+
ferrocene/ferrocenium couple (Fc/Fc , E1 = 0.505 V) was used as a standard. All potentials
/2
–
3
are referenced to the Ag/AgCl reference electrode. Solutions containing about 10
M
complexes and 0.1 M LiClO as supporting electrolyte were deoxygenated by a stream of
4
high purity nitrogen for at least 10 minutes.
2.3 Synthesis of the ligands
2.3.1 Synthesis of 4-chlorophenyl thiosemicarbazide (2)
4-chlorophenyl thiosemicarbazide was prepared in a way similar to the reported methods with
minor modification [22, 23]. 4-Chlorophenylisothiocyanate (6 mmol, 1.00 g) in 10 mL of
ethanol was added dropwise to excess hydrazine hydrate (80 %) (24 mmol, 1.43 mL) under
vigorous stirring at room temperature. The white precipitate was formed immediately.
Stirring was continued for 6 h. Then the mixture was filtered and the precipitate was washed
with ethanol to give 2. The reaction conditions should be controled because the side product
will form [24].
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2.3.2 Synthesis of H L1
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2 (6.4 mmol, 1.29 g) was dissolved in 50 ml methanol. Then a methanolic solution of
dialdehyde 3 (3.2 mmol, 0.91 g) was added and refluxed for 5 h. The yellow precipitate was
formed immediately. The mixture was filtered and the yellow precipitate was washed with
methanol and then diethyl ether. Yield 1.86 g (92 %). m. p. 210 °C (dec.). FT-IR (KBr disc,
–
1
cm ): 3402 m, 3070 w, 2927 m, 2879 m, 1605 s, 1485 s, 1453 s, 1321 m, 1293 m, 1241 s,
1
1161 m, 1050 m, 856 w, 752 s. H NMR (400 MHz, DMSO-d ): δ 2.28 (quintet, 2H,
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CH CH CH ), 4.31 (t, 4H, CH CH CH ), 6.99 (t, 2H, ArH), 7.13 (d, 2H. ArH), 7.40-7.42
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(m, 6H, ArH), 7.62 (d, 4H, ArH), 8.25 (d, 2H, ArH), 8.63 (s, 2H, ArCHN), 10.10 (s, 2H,
NH), 11.88 (s, 2H, NH) ppm.
2.3.3 Synthesis of H L2
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H L2 ligand was prepared by a similar procedure to that of H L1 except that dialdehyde 4
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(3.2 mmol, 0.96 g) was used instead of 3 as dialdehyde. The resulting yellow-colored solid
product was formed, filtered, and dried. Yield 1.91 g (92 %). m. p. 220 °C. FT-IR (KBr disc,
–
1
cm ): 3332 s, 2926 s, 2855 s, 1611 s, 1534 m, 1485 s, 1451 s, 1293 m, 1240 s, 1161 m, 1105
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m, 1028 s, 823 w, 750 s. H NMR (400 MHz, DMSO-d ): δ 4.27 (m, 5H, CH CH(OH)CH ),
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5.37 (s, 1H, OH), 6.99 (t, 2H, ArH), 7.14 (d, 2H. ArH), 7.40-7.43 (m, 6H, ArH), 7.64 (d, 4H,
ArH), 8.24 (d, 2H, ArH), 8.63 (s, 2H, ArCHN), 10.11 (s, 2H, NH), 11.87 (s, 2H, NH) ppm.
2.4. Synthesis of the complexes
2.4.1. General procedure
H L1 or H L2 (1 mmol) was dissolved in a dichloromethane-methanol mixture (10:1) under
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+
2+
reflux. To this refluxing solution was added a solution of the metal acetates of Cu and Ni
(1 mmol) dissolved in the methanol and refluxing was continued for 4 h. The solvent was
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concentrated and products were filtered off, washed with methanol and then with diethyl
ether. The complexes were isolated as air-stable solids and soluble in chloroform, DMF and
slightly soluble in ethanol and methanol.
2.4.2. [CuL1].MeOH
Dark green crystals. Yield 0.52 g (70 %). m.p. 190 °C (dec.). Anal. Calc. for
C H Cl CuN O S .CH OH: C, 51.58; H, 4.06; N, 11.28 %. Found: C, 51.48; H, 4.12: N,
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11.20 %. FT-IR (KBr disc, cm ): 3301 m, 2927 m, 1599 s, 1487 s, 1435 s, 1296 m, 1243 s,
1161 m, 1104 m, 1027 s, 803 m, 751 s.
2.4.3. [NiL1].EtOH
Brown crystals. Yield 0.56 g (74 %). m.p. 205 °C (dec.). Anal. Calc. for
C H Cl N NiO S .CH CH OH: C, 52.54; H, 4.28; N, 11.14 %. Found: C, 52.34; H, 4.30;
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N, 11.01 %. FT-IR (KBr disc, cm ): 3064 w, 2925 w, 1595 m, 1538 m, 1499 s, 1456 m,
1305 m, 1245 m, 1162 w, 1091 w, 1050 m, 827 m, 752 m.
2.4.4. [Cu(HL2)].2MeOH
Dark green precipitates. Yield 0.57 g (72 %). m.p. 175 °C (dec.). Anal. Calc. for
C H Cl CuN O S .2CH OH: C, 49.97; H, 4.32; N, 10.59 %. Found: C, 50.13; H, 4.34; N,
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10.37 %. FT-IR (KBr disc, cm ): 3326 s, 2931 w, 1595 s, 1488 s, 1393 m, 1303 s, 1249 s,
1112 m, 1044 m, 947 w, 824 m, 751 m.
2.4.5 [Ni(HL2)].MeOH
Brown precipitates. Yield 0.6 g (79 %). m.p. 210 °C (dec.). Anal. Calc. for
C H Cl N NiO S .CH OH: C, 50.82; H, 4.00; N, 11.11 %. Found: C, 50.76; H, 4.03; N,
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10.89 %. FT-IR (KBr disc, cm ): 3392 m, 3060 w, 2925 w, 1595 s, 1538 s, 1486 s, 1453 s,
1395 s, 1305 s, 1244 s, 1164 w, 1091 w, 1036 m, 825 m, 750 m.
2.5. Single-crystal X-ray diffraction
X-ray structural analysis for [CuL1].MeOH and [NiL1].EtOH: For each structure
determination a single crystal was selected and mounted using NVH immersion oil onto a
nylon fiber and cooled to the data collection temperature of 100(2) K. Data were collected on
a Bruker-AXS Kappa APEX II CCD diffractometer with Mo-Kα radiation. Unit cell
parameters were obtained from 60 data frames, 0.5 º ϕ, from three different sections of the
Ewald sphere. A complete and redundant data set was collected using the APEX2 software
[25]. These data were integrated using SAINT+ and treated with SADABS [26] absorption
corrections based on redundant multi-scan data. The systematic absences in the data were
analysed with XPREP [27] and were consistent with the centrosymmetric, monoclinic space
group P2 /c for both crystals, whose unit cell parameters were very similar. The structures
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were solved by intrinsic phasing methods and refined by least squares method on F using the
SHELXTL program package [28]. Details regarding specific solution refinement for each
compound are provided in the following paragraphs.
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Details for [CuL1].MeOH: Single crystals were grown by slow evaporation of
dichloromethane/methanol solvent mixture. The asymmetric unit was found to contain one
molecule of [CuL1] and one molecule of methanol solvent disordered over two positions.
The methanol was modeled with the aid of similarity restraints on bond distances and
anisotropic displacement parameters. All non-hydrogen atoms were refined with anisotropic
displacement parameters. Hydrogen atoms bound to nitrogen were located and refined
isotropically, and the remaining hydrogen atoms were treated as idealized contributions.
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Details for [NiL1].EtOH: Single crystals were grown by diffusing a chloroform/ethanol
solution of the compound with toluene. The crystals obtained for this complex were very
small and weakly diffracting, with data only out 0.90 Å. The asymmetric unit was found to
contain one molecule of [NiL1] and one molecule of ethanol solvent that participates in a
hydrogen bond with an NH group of the ligand. All non-hydrogen atoms were refined with
anisotropic displacement parameters. Hydrogen atoms bound to nitrogen and oxygen were
located and refined isotropically, and the remaining hydrogen atoms were treated as idealized
contributions. Table 1 summarizes crystal and refinement data for [NiL1].EtOH and
[CuL1].MeOH.
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Table 1. Crystal data and structure refinement for [NiL1].EtOH and [CuL1].MeOH
[
NiL1].EtOH
[CuL1].MeOH
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
C H Cl N NiO S
754.37
100(2) K
0.71073 Å
Monoclinic
P 21/c
C H Cl CuN O S
745.18
100(2) K
0.71073 Å
Monoclinic
P 21/c
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2
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32 30
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3 2
Unit cell dimensions
a = 18.808(3) Å, α = 90°
a = 18.9426(15) Å, α = 90 °
b = 9.2333(13) Å, β= 107.161(4)°
c = 19.805(3) Å, γ = 90°
3286.2(8) Å
b = 9.0834(8) Å, β = 106.2808(19) °
c = 19.9463(17) Å, γ = 90 °
3294.4(5) Å
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Volume
Z
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4
3
3
Density (calculated)
Absorption coefficient
F(000)
Crystal size
Theta range for data collection
Index ranges
Reflections collected
Independent reflections
Completeness to theta = 25.242° 79.3 %
1.525 Mg/m
0.926 mm
1560
0.120 x 0.050 x 0.020 mm
2.116 to 23.256 °
-20 ≤ h ≤ 20, -10 ≤ k ≤ 10, -21 ≤ l ≤ 22
33755
1.502 Mg/ m
0.996 mm
1532
0.320 x 0.210 x 0.060 mm
2.108 to 32.577 °
-28 ≤ h ≤ 28, -13 ≤ k ≤ 13, -30 ≤ l ≤ 30
96509
12000 [R(int) = 0.0476]
100.0 %
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4711 [R(int) = 0.1248]
Absorption correction
Max. and min. transmission
Refinement method
Semi-empirical from equivalents
Semi-empirical from equivalents
0.7465 and 0.6489
Full-matrix least-squares on F
12000 / 39 / 438
1.070
0.7449 and 0.6511
Full-matrix least-squares on F
4711 / 0 / 440
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Data / restraints / parameters
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Goodness-of-fit on F
1.005
Final R indices [I>2sigma(I)]
R indices (all data)
Largest diff. peak and hole
R1 = 0.0521, wR2 = 0.0973
R1 = 0.1052, wR2 = 0.1157
0.702 and –0.411 e Å
R1 = 0.0456, wR2 = 0.1275
R1 = 0.0627, wR2 = 0.1378
2.213 and –1.202 e Å
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3. Results and discussions
3.1. Synthesis of compounds
Scheme 1 illustrates the reaction scheme used to obtain H L1 and H L2 ligands. The
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synthesis of 4-substituted thiosemicarbazides can be achieved in a one-pot synthesis by the
reaction of 4-substituted phenylisothiocyanate with hydrazine. A condensation reaction
between two equivalents 4-chlorophenylthiosemicarbazide and one equivalent of 3 or 4 as
dialdehydes gave two bis(thiosemicarbazone) ligands H L1 and H L2, respectively, in high
2
3
yield. Thiosemicarbazone ligands may exist as thione/thiol tautomeric forms owing to the
intramolecular proton transfer [29] but the IR spectra of H L1 and H L2 do not display ν(S–
2
3
–
1
H) in the region 2500-2600 cm indicating that in the solid state these ligands remain in the
thione form [30].
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The infrared spectra of H L1 and H L2 show a strong absorption band at 1605 and 1611 cm
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, respectively, assigned to the C=N stretching vibration, indicating the formation of the
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Schiff base product. Furthermore, H NMR spectra of H L1 and H L2 show singlets at 8.63
2
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ppm assigned to the HC=N protons. The chemical Shift of NH–N and NH–Ar protons
observed as singlets, respectively, at 11.88 and 10.10 ppm for H L1 and 11.87 and 10.11
2
ppm for H L2.
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The reaction of nickel(II) and copper(II) acetates with ligands yielded corresponding
complexes in high yields. On the basis of their elemental analysis and X-ray analysis (only
for two complexes) the complexes were formulated as [CuL1].MeOH, [NiL1].EtOH,
[Cu(HL2)].2MeOH, and [Ni(HL2)].MeOH. In all complexes both ligands act as doubly
negatively charge anions in complexation through deprotonation of the hydrazinic hydrogen
1
atoms. In H nmr of nickel complexes in CDCl , signals of NH–N protons at 11.88 ppm for
3
H L1 and at 11.87 ppm for H L2 at free ligands are omitted upon coordination to the nickel.
2
3
But signals of NH–Ar protons appear as two distinct signals at 10.07 and 10.15 ppm for
[NiL1].EtOH and at 10.05 and 10.16 ppm for [Ni(HL2)].MeOH. The frequency of the imine
–
1
bond, ν(C=N), observed above 1600 cm in the free ligands, shifts to lower wavenumbers
upon coordination to the metal in all complexes. Distinguishing between ν(C=C) and ν(C=N)
in the complexes is difficult. Therefore, the ν(C=C) of the phenyl rings and ν(C=N) of the
imine in the complexes are assigned, without distinguishing them, to the peaks observed
–1
between 1400 to 1600 cm [31].
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Scheme1. Preparation steps of H L1 and H L2 and corresponding complexes
2 3
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3.2. Crystal structure of compounds
An ORTEP view of the nickel complex [NiL1].EtOH is given in Fig. 1 and selected bond
distances and angles are given in Table 2. In this complex ligand H L1 has lost hydrazinic
2
hydrogen atoms and therefore acts as a dianion. Two thiosemicarbazone moieties act as
convergent to form a mononuclear complex. The ligand is tetradentate and nickel is
coordinated by two imine nitrogen atoms (N13 and N43) and two sulfur atoms (S1 and S2).
The metal center has a distorted square planar NiN S coordination environment according to
2
2
the geometrical parameter η , defined as [360 – (α + β)]/141, where α, β are the two largest
4
coordination angles (166.02(14) and 161.85(14) °). The η values are zero and one for perfect
4
square planar and tetrahedral geometry, respectively [32]. The calculated η index is 0.23 for
4
Ni1 showing that nickel has a distorted square planar. The Ni–Nimine bond distances (1.902(4)
and 1.904(4) Å) and Ni–S bond distances (2.1645(14) and 2.1651(15) Å) are comparable to
corresponding distances in related complexes [33]. N12–C10 and N42–C40 bond distances
1.298(6) and 1.300(6) Å, respectively, are consistent with C=N double bond and similar to
bond distances of C=N double bonds N43–C50 and N13–C20 with 1.293(7) and 1.310(6) Å
distances, respectively. Also C–S distances are not in the range of double bond character and
are comparable to corresponding distances in other thiosemicarbazone complexes [34-36].
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1

2
2
20
21
These observations are consistent to lossing of hydrazinic hydrogens and producing negative
charges on sulfur atoms that are coordinated to nickel cation.
2
2
22
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Fig. 1. Molecular structure of [NiL1].EtOH complex. Solvent molecule is omitted
2
2
2
2
2
2
2
2
2
2
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2
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The molecular structure of the copper complex [CuL1].MeOH is given in Fig. 2 with selected
distances and angles listed in the Table 2. The molecular structure of [CuL1].MeOH is
similar to [NiL1].EtOH. The ligand acts as an N S donor set around the copper, giving a
2
2
distorted square planar geometry and η index is 0.36 for Cu1. Distortion of square planar for
4
the [CuL1].MeOH is greater than for the [NiL1].EtOH. The angles around the nickel are
closer to the 90° preferred at the square planar geometry. In copper complex deviation from
90° for N3–Cu1–N6 (99.26(7) °) and S1–Cu1–S2 (100.42(2) °) angles are greater. However,
N6–Cu1–S2 and N3–Cu1–S1 angles are, respectively, 85.18(5) ° and 86.16(5) ° and are
similar to N13–Ni1–S1 and N43–Ni1–S2 angles with values 85.71(12) ° and 86.52(14) °,
respectively. The Cu–Nimine distances (1.9915(16) and (1.9964(17) Å ) and Cu–S distances
(2.2303(5) and 2.2381(6) Å ) are longer than the Ni–Nimine distances (1.902(4) and 1.904(4)
1
2

2
2
36
37
Å ) and Ni–S distances (2.1645(14) and 2.1651(15) Å). The Cu–Sthiolate and Cu–Nimine bond
distances are similar to other compounds with Sthiolate and Nimine coordination [12, 36].
2
38
Table 2. Selected bond distances (Å) and angles (°) for [NiL1].EtOH and [CuL1].MeOH
bond distances
Ni1–S1
Ni1–S2
Ni1–N13
Ni1–N43
[NiL1].EtOH bond distances
[CuL1].MeOH
2.2381(6)
2.2303(5)
1.9915(16)
1.9964(17)
1.750(2)
1.759(2)
1.372(3)
1.368(2)
1.309(3)
1.302(3)
1.395(2)
1.397(2)
1.296(2)
1.293(3)
1.460(3)
1.457(3)
2.1645(14)
2.1651(15)
1.902(4)
1.904(4)
1.761(5)
1.756(5)
1.370(6)
1.365(6)
1.298(6)
1.300(6)
1.415(5)
1.407(5)
1.310(6)
1.293(7)
1.443(7)
1.447(7)
Cu1–S1
Cu1–S2
Cu1–N3
Cu1–N6
S1–C1
S1–C10
S2–C40
S2–C3
N11–C10
N41–C40
N12–C10
N42–C40
N13–N12
N42–N43
N13–C20
N43–C50
C21–C20
N1–C1
N4–C3
C1–N2
C3–N5
N2–N3
N5–N6
C2–N3
C4–N6
C4–C41
C2–C21
C50–C51
Bond angles
N13–Ni1–N43
N13–Ni1–S1
N43–Ni1–S1
N13–Ni1–S2
N43–Ni1–S2
S1–Ni1–S2
[NiL1].EtOH Bond angles
[CuL1].MeOH
99.26(7)
156.51(5)
85.18(5)
86.16(5)
152.87(5)
100.42(2)
96.62(17)
85.71(12)
166.02(14)
161.85(14)
86.52(14)
95.56(6)
N3–Cu1–N6
N3–Cu1–S2
N6–Cu1–S2
N3–Cu1–S1
N6–Cu1–S1
S2–Cu1–S1
2
39
2
2
40
41
Fig. 2. Molecular structure of [CuL1].MeOH complex. Solvent molecule is omitted
1
3

2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
Hydrogen bonds and short contacts in [NiL1].EtOH and [CuL1].MeOH complexes are
similar. The unit cell of [NiL1].EtOH complex consists of four units of [NiL1] and four
ethanol molecules, held together in the crystal packing by intermolecular bonds such as
hydrogen bonds, O–H…π, and C–H…π interactions (Fig. S1 and Fig. S2). The uncoordinated
ethanol molecules in [NiL1].EtOH act as hydrogen acceptor from N41–H41 and C46–H46
with distances O1S…H41 = 2.24(6) Å and O1S…H46 = 2.51 Å and as a hydrogen donor
toward π-ring (C 5 = C41, C42, C43, C44, C45, and C46) of other complex unit through
g
O1S–H1S… C 5 = 2.47 Å. In [CuL1].MeOH complex the uncoordinated methanols act as
g
hydrogen acceptor from N1–H1 and C16–H16 with distances O1S…H1 = 2.14(3) Å and
O1S…H16 = 2.44 Å and as a hydrogen donor toward N1 atom (H1S…N1 = 2.58 Å). In both
complexes uncoordinated imine nitrogen atoms (N12 and N42 in [NiL1].EtOH and N2 and
N5 in [CuL1].MeOH) are involved in intramolecular hydrogen bonds with hydrogen atoms
of 4-chloro substituted phenyl rings (see Table 3).
Table 3. Hydrogen bonds and X–H…π interactions for [NiL1].EtOH and [CuL1].MeOH
Hydrogen bonds
compound
d(H…A)
d(D…A)
D–H…A
d(D–H)
0.75(6)
0.95
0.95
0.95
0.83(3)
0.84
0.75(3)
0.95
0.95
0.95
< (D–H…A)
162(6)
122
122
142
166(3)
108
159(3)
122
144
122
i
[
NiL1].EtOH
N41–H41…O1S
C12–H12…N12
C42–H12…N42
2.24(6)
2.23
2.22
2.51
2.14(3)
2.58
2.80(3)
2.20
2.44
2.960(6)
2.847(7)
2.839(7)
3.310(7)
2.952(11)
2.952(11)
3.5118(19)
2.820(4)
3.251(13)
2.888(3)
i
C46–H46… O1S
N1–H1…O1S
O1S–H1S…N1
N4–H4…S2
C12–H12…N2
C16–H16… O1S
C36–H36…N5
ii
[
CuL1].MeOH
iii
ii
2.27
Symmetry codes (i) –x + 2, -y, -z + 2 (ii) x, -y – 1/2, z + 1/2 (iii) –x – 1, -y – 1, -z + 1
X–H…π interactions
compound
X–H…Cg
O1S–H1S…C (5)
C13–H13…C (6)
C32–H32…C (3)
C35–H35…C (4)
C50–H50A…C (5)
O2S–H2S…C (3)
d(H…Cg)
2.47(6)
2.97
2.66
2.92
d(X…Cg)
[
NiL1].EtOH
3.311(4)
3.726(6)
3.515(6)
3.655(2)
3.518(3)
3.06(3)
g
g
g
[
CuL1].MeOH
g
2.68
2.64
g
g
C2S–H2S2… C (6)
2.82
3.504(8)
g
2
57
1
4

2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
3.3 UV-Vis spectroscopy
The spectra of H L1 and H L2 exhibit similar patterns in the 230-700 nm region (Fig. S3).
2
3
The UV-Vis spectra of the metal-free ligands are dominated by intra-ligand transitions
associated with the phenyl rings, imines, and thione portions of the ligands. The electronic
spectra taken in CH Cl of copper(II) and nickel(II) complexes are shown in Fig. 3 and Fig.
2
2
4, respectively, and the spectral data are tabulated in Table 4. Coordination of
bis(thiosemicarbazone) ligands to the Cu(II) and Ni(II) leads to changes in the UV region
(230-400 nm). This is presumably because of the change in the ligand conjugation caused by
the deprotonation of the ligands upon coordination. Also, upon coordination new bands (two
bands for copper(II) complexes and one band for nickel(II) complexes) above 400 nm appear
which correspond to square planar thiosemicarbazone Cu(II) and Ni(II) complexes [9, 12].
The spectra of the nickel and copper complexes of the two ligands are very similar.
Therefore, based on the above spectral evidences, it is confirmed that the ligands H L1 and
2
H L2 are coordinated via the azomethine nitrogen and thiolate sulphur atoms with the same
3
coordination mode (Structure of Cu(II) and Ni(II) complexes of H L1 ligand have been
2
confirmed by X-ray single-crystal structure analysis).
1
5

2
75
–
5
2
2
76
77
Fig. 3 UV-Vis absorption spectra of 3 × 10 M of [CuL1].MeOH and [Cu(HL2)].2MeOH
–
4
and 4 × 10 M (inset)
2
2
78
79
–
5
Fig 4. UV-Vis absorption spectra of 3 × 10 M of [NiL1].EtOH and [Ni(HL2)].MeOH and 9
–
4
2
2
2
2
2
80
81
82
83
84
× 10 M (inset)
1
6

2
85
Table 4. Electronic spectral data of compounds in CH Cl
2 2
–
1
–1
Compound
λ, nm (ε, M cm )
H L1
312 (42005) sh, 339 (51503)
313 (43699) sh, 335 (58182)
2
H L2
3
[
[
[
[
CuL1].MeOH
245 (46054), 332 (50620), 421 (3445) sh, 569(1143)
Cu(HL2)].2MeOH 249 (39884), 334 (46093), 425 (2844) sh, 587 (1005)
NiL1].EtOH
269 (51759), 337 (38206), 498 (316) sh
269 (49114), 336 (36642), 498 (301) sh
Ni(HL2)].MeOH
2
2
2
2
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
86
87
88
89
90
91
92
93
94
95
96
97
98
99
00
01
02
03
04
05
3.4 Cyclic voltammetry
To investigate the redox properties of the complexes, the cyclic voltammograms were
recorded for all the complexes in DMF using the same cell set up. Results are summarized in
Table 5 and in Fig. 5 and Fig. 6. Bis(thiosemicarbazone) Schiff base ligands, H L1 and
2
H L2, have imine and thiolate donor sites which have π-acceptor property, therefore, they are
3
expected to stabilize the lower oxidation states of copper and nickel. Neither ligands were
electroactive in the range of –1.25 to +1 V.
[CuL1].MeOH and [Cu(HL2)].2MeOH complexes exhibit a reversible one electron reduction
II
I
process assigned to the metal-centered Cu /Cu redox couple at E = 0.023 and –0.099 V vs
1
/2
an Ag/AgCl reference electrode in DMF, respectively. Reduction in [CuL1].MeOH is easier
than [Cu(HL2)].2MeOH, also reversibility in [CuL1].MeOH (ΔE = 70 mV, i /i =1.001) is
p
pc pa
II
higher than in [Cu(HL2)].2MeOH (ΔE = 71 mV, i /i = 0.878). Redox potentials of Cu
p
pc pa
complexes lie within a range accessible to cellular oxidants and reductants [18].
The CV of [NiL1].EtOH in DMF displays a reversible reductive response at E1/2 = –0.797 V
vs Ag/AgCl (E = –0.832 V, E = –0.761 V and ΔE = 71 mV) that has been shown in Fig.
pc
pa
p
II
I
6. The value of ipc/ipa = 1.081 clearly indicates the reversibility of Ni /Ni couple.
[Ni(HL2)].MeOH complex also exhibits a reversible reductive response at E1/2 = –0.870 V
(E = –0.921 V, E = –0.821 V) but with a greater ΔE value (100 mV) than [NiL1].EtOH
pc
pa
p
complex. Therefore, in [CuL1].MeOH and [NiL1].EtOH complexes without a hydroxyl
1
7

3
3
3
3
06
07
08
09
group reduction is easier and reversibility is higher than in the corresponding
[Cu(HL2)].2MeOH and [Ni(HL2)].MeOH complexes with an OH group.
–
1
Table 5. Cyclic voltammetry data for complexes in DMF solutions at 100 mVs scan rate
Complex
Epc (V)
Epa (V)
0.058
ΔE (mV)
E1/2 (V)
0.023
|i |/|i |
p
pc pa
[
[
[
[
CuL1].MeOH
–0.013
70
1.001
0.878
1.081
1.291
Cu(HL2)].2MeOH –0.134
–0.063
–0.761
–0.821
71
–0.099
–0.797
–0.871
NiL1].EtOH
–0.832
–0.921
71
Ni(HL2)].MeOH
100
The ferrocenium-ferrocene couple shows a peak separation of 110 mV under the same experimental conditions.
ΔE = E – E and E = (E + E )/2
p
pa
pc
1/2
pc
pa
3
10
3
3
11
12
Fig 5. Cyclic voltammograms of [CuL1].MeOH (solid line) and [Cu(HL2)].2MeOH (dashed
c
–
1
3
13
line) in DMF solution containing 0.1 M LiClO at 100 mVs
4
3
3
14
15
Fig. 6. Cyclic voltammograms of [NiL1].EtOH (solid line) and [Ni(HL2)].MeOH (dashed
–
1
3
16
line) in DMF solution containing 0.1 M LiClO at 100 mVs
4
1
8

3
3
3
3
3
3
3
3
17
18
19
20
21
22
23
24
Conclusions
Two new bis(thiosemicarbazone) Schiff base ligands were prepared in good yields. Both
ligands lose hydrazinic hydrogen atoms upon coordination and act as doubly negative anions
when react with Ni(II) and Cu(II) acetates. These ligands act as N S donor set in all
2
2
complexes and hydroxyl group has no effect on coordination geometry but has influence on
II
I
electrochemical potentials and reversibility of M /M couples. Redox properties of these
complexes clearly revealed that imine N and thiolate S donor set able to stabilize the +1
oxidation state of nickel and copper.
3
3
25
26
Acknowledgements
3
3
3
3
3
3
3
3
3
3
27
28
29
30
31
32
33
34
35
36
We would like to thank University of Tabriz for supporting this work.
Appendix A. Supplementary material
CCDC 1028265 and 1028266 contain the supplementary crystallographic data for
[CuL1].MeOH and [NiL1].EtOH complexes, respectively. These data can be obtained free of
charge
from
The
Cambridge
Crystallographic
Data
Centre
via
www.ccdc.cam.ac.uk/data_request/cif. Supplementary material contains hydrogen bonds, O–
H…π, and C–H…π interactions for [NiL1].EtOH and UV-Vis spectra of H L1 and H L2
2
3
ligands.
1
9

3
3
3
3
37
38
39
40
References
[1] S. Chandra, Vandana, Spectrochim. Acta, Part A. 129 (2014) 333–338.
[2] K. Alomar, A. Landreau, M. Allain, G. Bouet, G. Larcher, J. Inorg. Biochem. 126 (2013)
76–83.
3
41
[3] A. Karaküçük-Iyidogan, D. Tasdemir, E.E. Oruç-Emre, J. Balzarini, Eur. J. Med. Chem.
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
46 (2011) 5616–5624.
[4] L.P. Duan, H.B. Zhang, Arabian J. Chem. 4 (2011) 231–234.
[5] D.L. Klayman, J.F. Bartosevich, T.S. Griffin, C.J. Mason, J.P. Scovill, J. Med. Chem. 22
(1979) 855–862.
[6] D.R. Richardson, D.S. Kalinowski, V. Richardson, P.C. Sharpe, D.B. Lovejoy, M. Islam,
P.V. Bernhardt, J. Med. Chem. 52 (2009) 1459–1470.
[7] J.A. Lessa, I.C. Mendes, P.R.O. da Silva, M.A. Soares, R.G. dos Santos, N.L. Speziali,
N.C. Romeiro, E.J. Barreiro, H. Beraldo, Eur. J. Med. Chem. 45 (2010) 5671–5677
[8] M.X. Li, C.L. Chen, D. Zhang, J.Y. Niu, B. S. Ji, Eur. J. Med. Chem. 45 (2010) 3169–
3177.
[9] J.P. Holland, F.I. Aigbirhio, H.M. Betts, P.D. Bonnitcha, P. Burke, M. Christlieb, G.C.
Churchill, A.R. Cowley, J.R. Dilworth, P.S. Donnelly, J.C. Green, J.M. Peach, S.R.
Vasudevan, J.E. Warren, Inorg. Chem. 46 (2007) 465–485.
[10] S.R. Bayly, R.C. King, D.J. Honess, P.J. Barnard, H.M. Betts, J.P. Holland, R.Hueting,
P.D. Bonnitcha, J.R. Dilworth, F.I. Aigbirhio, M. Christlieb, J. Nucl. Med. 49 (2008) 1862–
1868.
[11] R.I. Maurer, P.J. Blower, J.R. Dilworth, C.A. Reynolds, Y. Zheng, G.E.D. Mullen, J.
Med. Chem. 45 (2002) 1420–1431.
[12] A.R. Cowley, J.R. Dilworth, P.S. Donnelly, A.D. Gee, J.M. Heslop, Dalton Trans.
(2004) 2404–2412.
2
0

3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
[13] Z. Durackova, M.A. Mendiola, M.T. Sevilla, A. Valent, Bioelectrochem. Bioenerg. 48
(1999) 109–116.
[14] T.L. James, L. Cai, M.C. Muetterties, R.H. Holm, Inorg. Chem. 35 (1996) 4148–4161.
[15] S.K. Chatterjee, S. Roy, S.K. Barman, R.C. Maji, M.M. Olmstead, A.K. Patra, Inorg.
Chem. 51 (2012) 7625–7635.
[16] M.A. Cater, H.B. Pearson, K. Wolyniec, P. Klaver, M. Bilandzic, B.M. Paterson, A.I.
Bush, P.O. Humbert, S. La Fontaine, P.S. Donnelly, Y. Haupt, ACS Chem. Biol. 8 (2013)
1621–1631.
[17] Z. Xiao, P.S. Donnelly, M. Zimmermann, A.G. Wedd, Inorg. Chem. 47 (2008) 4338–
4347.
[18] P.V. Bernhardt, P.C. Sharpe, M. Islam, D.B. Lovejoy, D.S. Kalinowski, D.R.
Richardson, J. Med. Chem. 52 (2009) 407–415.
[19] A. A. Khandar, S.A. Hosseini-Yazdi, Polyhedron 22 (2003) 1481–1487.
[20] S.A. Hosseini-Yazdi, A. Mirzaahmadi, P. Samadzadeh-Aghdam, A.A. Khandar, G.
Mahmoudi, W.S. Kassel, W.G. Dougherty, Inorg. Chim. Acta. 414 (2014) 115–120.
[21] S.A. Hosseini-Yazdi, P. Samadzadeh-Aghdam, A. Mirzaahmadi, A.A. Khandar, G.
Mahmoudi, M. Ruck, T. Doert, S.S. Balula, L. Cunha-Silva, Polyhedron 80 (2014) 41–46.
[22] H. Huang, Q. Chen, X. Ku, L. Meng, L. Lin, X. Wang, C. Zhu, Y. Wang, Zh. Chen, M.
Li, H. Jiang, K. Chen, J. Ding, H. Liu, J. Med. Chem. 53 (2010) 3048–3064.
[23] L.P. Duan, H.B. Shang, Arabian J. Chem. 4 (2011) 231-234.
[24] M.D. Hall, N.K. Salam, J.L. Hellawell, H.M. Fales, C.B. Kensler, J.A. Ludwig, G.
Szakacs, D.E. Hibbs, M.M. Gottesman., J. Med. Chem. 52(2009) 3191–3204.
[25] APEX II, v. 2014.5-0; Bruker AXS: Madison, WI, 2014.
[26] SADABS, v. 2012/1: An Empirical Absorption Correction Program; Bruker AXS Inc.:
Madison, WI, 2012.
2
1

3
3
3
3
3
3
3
3
3
3
3
87
88
89
90
91
92
93
94
95
96
97
[27] XPREP – Reciprocal space exploration, v. 2014/2 Bruker AXS: Madison, WI, 2014.
[28] G.M., Sheldrick, Acta Cryst. A64 (2008) 112–122.
[29] M.A. Affan, M.A. Salam , F.B. Ahmad, J. Ismail, M.B. Shamsuddin, H.M. Ali, Inorg.
Chim. Acta. 366 (2011) 227–232.
[30] F. Basuli, M. Ruf, C.G. Pierpont, S. Bhattacharya, Inorg. Chem. 37(1998) 6113-6116.
[31] A. Sreekanth, H.-K. Fun, M.R. Prathapachandra Kurup, J. Mol. Struct. 737 (2005)
61–67.
[32] L. Yang, D.R. Powell, R.P. Houser, Dalton Trans. (2007) 955-964.
[33] M.B. Ferrari, S. Capacchi, F. Bisceglie, G. Pelosi, P. Tarasconi, Inorg. Chim. Acta.
312 (2001) 81–87.
[34] C. Rodriguez-Argüelles, P. Touron-Touceda, R. Cao, A.M. Garcia-Deibe, P. Pelagatti,
C. Pelizzi, F. Zani, J. Inorg. Biochem. 103 (2009) 35–42.
3
98
3
4
4
4
99
00
01
02
[35] A. Perez-Rebolledo, I.C. Mendes, N.L. Speziali, Ph. Bertani, J.M. Resende, A.F. de
Carvalho Alcantara, H. Beraldo, Polyhedron 26 (2007) 1449–1458.
[36] D.G. Cafatayud, E. Lopez-Torres, M.A. Mendiola, C.J. Pastor, J.R. Procopio, Eur. J.
Inorg. Chem. (2005) 4401–4409.
2
2





Ni(II) and Cu(II) complexes of new bis(thiosemicarbazone) ligands were prepared
ligands act as N S donor set and OH group has no effect on coordination geometry
2
2
New ligands can stabilize low oxidation state (+1) of nickel and copper
II
I
OH group has effect on redox potentials and reversibility of M /M couples

Two new bis(thiosemicarbazone) Schiff base ligands and their metal complexes with Cu(II) and
Ni(II) were prepared and characterized by NMR, FT-IR, UV-Vis absorption spectroscopy, single
crystal X-ray diffraction, CHN elemental analysis and cyclic voltammetry.