Synthesis, characterization, crystal structure and antioxidant activity of Ni(II) and Cu(II) complexes with 2-formilpyridine N(4)-phenylthiosemicarbazone

Article abstract of DOI:10.1016/j.poly.2015.05.009

New nickel(II) and copper(II) complexes, [Ni(HL)₂]Cl₂·2.5H₂O (1), [Cu(L)Cl] (2), [Cu(HL)(H₂O)](SO₄) (5), [Cu(L)(X)(H₂O)₂] [X = Br^? (3), OAc^? (4), NO₃^? (6), ClO₄^? (7)] were synthesized with 2-formilpyridine N(4)-phenylthiosemicarbazone (HL·HCl). The thiosemicarbazone ligand was characterized by NMR (¹H and ¹³C) spectroscopy and X-ray diffraction. All the complexes were characterized by electronic and FT-IR spectroscopy, molar conductivity, magnetic susceptibility measurements and elemental analysis. In addition, the copper(II) complexes were studied by EPR spectroscopy. Also, the crystal structures of complexes 1 and 2 were determined by single-crystal X-ray diffraction analysis. In the complex 1, the nickel atom exhibits a slightly distorted octahedral N₄S₂ coordination provided by two molecules of tridentate non-deprotonated ligand. The copper atom exhibits a distorted square-planar coordination environment in the complex 2 provided by one molecule of deprotonated ligand and one chloride anion. The free ligand and the metal complexes were screened for their antioxidant activity by free radical scavenging assays using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and compared with that of butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) standards.

Full text of DOI:10.1016/j.poly.2015.05.009

Accepted Manuscript
Synthesis, characterization, crystal structure and antioxidant activity of Ni(II)
and Cu(II) complexes with 2-formilpyridine N(4)-phenylthiosemicarbazone
Diana-Carolina Ilies, Sergiu Shova, Valeria Radulescu, Elena Pahontu, Tudor
Rosu
PII:
S0277-5387(15)00251-X
http://dx.doi.org/10.1016/j.poly.2015.05.009
POLY 11308
DOI:
Reference:
Polyhedron
To appear in:
Received Date:
Accepted Date:
24 February 2015
1 May 2015
Please cite this article as: D-C. Ilies, S. Shova, V. Radulescu, E. Pahontu, T. Rosu, Synthesis, characterization,
crystal structure and antioxidant activity of Ni(II) and Cu(II) complexes with 2-formilpyridine N(4)-
phenylthiosemicarbazone, Polyhedron (2015), doi: http://dx.doi.org/10.1016/j.poly.2015.05.009
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Synthesis, characterization, crystal structure and antioxidant activity of Ni(II) and
Cu(II) complexes with 2-formilpyridine N(4)-phenylthiosemicarbazone
Diana-Carolina Iliesa,b, Sergiu Shovac, Valeria Radulescu b, Elena Pahontud,*, Tudor Rosua
aInorganic Chemistry Department, Faculty of Chemistry, University of Bucharest, 23 Dumbrava Rosie Street,
020462 Bucharest, Romania
bOrganic Chemistry Department, Faculty of Pharmacy, University of Medicine and Pharmacy ‘‘Carol Davila’’,
6 Traian Vuia Street, 020956 Bucharest, Romania
cInstitute of Macromolecular Chemistry ‘‘Petru Poni’’, 41A Grigore Ghica Voda Alley, 700487 Iasi, Romania
dInorganic Chemistry Department, Faculty of Pharmacy, University of Medicine and Pharmacy ‘‘Carol Davila’’,
6 Traian Vuia Street, 020956 Bucharest, Romania
*Corresponding author.
E-mail address: elenaandmihaela@yahoo.com (E. Pahontu).
Abstract
New nickel(II) and copper(II) complexes, [Ni(HL)2]Cl2 ·2.5H2O (1), [Cu(L)Cl] (2),
-
-
[Cu(HL)(H2O)](SO4) (5), [Cu(L)(X)(H2O)2] [X= Br- (3), OAc- (4), NO3 (6), ClO4 (7)] were
synthesized with 2-formilpyridine N(4)-phenylthiosemicarbazone (HL·HCl). The
thiosemicarbazone ligand was characterized by NMR (1H and 13C) spectroscopy and X-ray
diffraction. All the complexes were characterized by electronic and FT-IR spectroscopy,
molar conductivity, magnetic susceptibility measurements and elemental analysis. In
addition, the copper(II) complexes were studied by EPR spectroscopy. Also, the crystal
structures of complexes 1 and 2 were determined by single-crystal X-ray diffraction analysis.
In the complex 1, the nickel atom exhibits a slightly distorted octahedral N4S2 coordination
provided by two molecules of tridentate non-deprotonated ligand. The copper atom exhibits a
distorted square-planar coordination environment in the complex 2 provided by one molecule
of deprotonated ligand and one chloride anion. The free ligand and the metal complexes were
screened for their antioxidant activity by free radical scavenging assays using 1,1-diphenyl-2-
picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS)
and compared with that of butylated hydroxytoluene (BHT) and butylated hydroxyanisole
(BHA) standards.
Keywords: 2-formilpyridine N(4)-phenylthiosemicarbazone, copper(II) complex, nickel(II)
complex, antioxidant activity, DPPH, ABTS.
1. Introduction
Thiosemicarbazones are an important group of multidentate ligands with potential
binding sites available for a wide variety of metal ions [1,2] and with a great number of
analytical applications [3-6]. The metal complexes obtained with thiosemicarbazones
represent an interesting and diverse class of compounds studied for theirs wide range of
pharmacological applications [7,8]. Among the transitional metals, thiosemicarbazones
complexes with nickel(II) and copper(II) have been more studied, as some of them have
shown anticancer, antifungal and antibacterial activities [9-11].
Thiosemicarbazones bearing a pyridine ring were the first thiosemicarbazones in
which antimalarial activity was detected, and the highest activity was reported when the N(4)
position is either disubstituted or part of a ring system [12]. A large number of complexes
with 2-pyridineformamide [10,13-15], 2-acetylpyridine thiosemicarbazone [16] or its N(4)-

substituted derivatives [17-22] have been studied for their structural diversity [23-25] and for
their biological properties that includes antitumour activity [18,26-28], antimicrobial
properties [11,16,22,29], antitrypanosomal activity [7] and anti-Mycobacterium tuberculosis
activity [27,30]. Among these compounds, 3-aminopyridinecarbaldehyde thiosemicarbazone
is considered one with great potential biological properties and is currently undergoing
clinical trials [31-34]. With 2-formilpyridine N(4)-phenylthiosemicarbazone, antimony(III)
complexes were prepared and presented antitrypanosomal activity against two forms of T.
cruzi [7]. Also, a complex of nickel(II) was prepared with the same thiosemicarbazone and
Ni(OAc)2 and studied by spectroscopic techniques [10].
In the present paper we report the synthesis, characterization and chelating behavior
of 2-formilpyridine N(4)-phenylthiosemicarbazone (HL·HCl) towards nickel(II) and
copper(II) ions. The copper(II) complexes were studied by EPR spectroscopy. The crystal
structures of the ligand and complexes 1 and 2 were resolved by X-ray diffraction. In view of
biological properties, we evaluated the antioxidant activity of the free ligand and its metal
complexes by DPPH and ABTS assays.
2. Experimental
2.1. Materials
2-formylpyridine (Aldrich) and 4-phenylthiosemicarbazide (Merck) were used as
received. NiCl2·6H2O, CuCl2·2H2O, CuBr2, Cu(CH3COO)2·H2O, Cu(ClO4)2·6H2O,
CuSO4·5H2O, and Cu(NO3)2·3H2O (Merck) were used as supplied. Solvents used for the
reactions were purified and dried by conventional methods [35].
2.2. Synthesis of 2-formylpyridine N(4)-phenylthiosemicarbazone (HL·HCl)
The ligand was prepared by a modified method reported earlier [10]. To a solution of
4-phenylthiosemicarbazide (0.167 g, 1 mmol) in ethanol (30 mL) was added slowly 2-
formylpyridine (0.107 g, 1 mmol) and a few drops of HCl. The resulting mixture was
refluxed for 4 h on a water bath. Then, the yellow precipitate was filtered, washed with
ethanol and recrystallized from methanol.
Yield 76%; M.p. 174–175°C; FW: 292.78 g/mol; Anal. Calc. for C13H13ClN4S: C,
53.28; H, 4.44; N, 19.13. Found: C, 53.45; H, 4.22; N, 19.02%. IR (KBr, cm-1): ν(N4–H)
3308, ν(N2–H) 3126, ν(C=N) 1598, ν(C=S) + ν(C=N) 1257, ν(N–N) 1079, ν(C=S) 774, ꢀ(py)
622. 1H NMR (DMSO-d6; δ, ppm; J, Hz): δ = 12.13 (s, 1H, H-N3), 10.36 (s, 1H, H-N4), 8.60
(d, 4.9, 1H, H-2), 8.42 (d, 7.7, 1H, H-5), 8.21 (s, 1H, H-7), 7.98 (t, 7.4, 1H, H-4), 7.56 (d, 7.7,
2H, H-10,14), 7.50 (dd, 7.4, 4.9, 1H, H-3), 7.39 (t, 7.7, 2H, H-11,13), 7.23 (t, 7.7, 1H, H-12);
13C NMR (DMSO-d6; δ, ppm): δ = 176.54 (C8), 151.91 (C6), 148.22 (C7), 141.21 (C2), 138.88
(C9), 138.28 (C5), 128.20 (C11,13), 126.06 (C10,14), 125.67 (C12), 124.70 (C4), 121.79 (C3).
2.3. General procedure for the preparation of the metal complexes (1–7)
To a solution of 2-formylpyridine N(4)-phenylthiosemicarbazone (0.256 g, 1 mmol)
in methanol (30 mL) was added a solution of the corresponding metal salt in methanol (10
mL). The molar ratio used was 1:2 [M:L] for the nickel(II) complex and 1:1 [M:L] for the
copper(II) complexes. Metal salts were used as follows NiCl2·6H2O for complex 1,
CuCl2·2H2O for complex 2, CuBr2 for complex 3, Cu(CH3COO)2·H2O for complex 4,
CuSO4·5H2O for complex 5, Cu(NO3)2·3H2O for complex 6, and Cu(ClO4)2·6H2O for

complex 7. The mixture was stirred for 3 h at 50°C. The precipitated obtained was filtered,
washed with methanol followed by ether and dried in vacuo.
[Ni(HL)2]Cl2 ·2.5H2O 1 Brown-reddish crystals. Yield: 75%; M.p. 179–181 °C; FW:
687.3 g/mol; Anal. Calc. for C26H29Cl2N8NiO2,5S2: C, 45.40; H, 4.22; N, 16.30; Ni, 8.54.
Found: C, 45.73; H, 3.97; N, 16.11; Ni, 8.32%. Main IR peaks (KBr, cm-1): ν(OH) 3368,
ν(N4–H) 3220, ν(N2–H) 3132, ν(C=N1) 1607, ν(C=S) + ν(CN) 1242, ν(N–N) 1076, ν(C=S)
771, ꢀ(py) 642, ν(C=N2) 1555. The complex is soluble in methanol, ethanol, acetonitrile,
DMF, DMSO and warm acetone, chloroform and dichloromethane. A methanolic solution of
complex 1 was left to stand at room temperature and, after 7 days, brown-reddish crystals
suitable for X-ray diffraction were collected.
[Cu(L)Cl] 2 Brown-reddish crystals. Yield: 63%; M.p. 213–215 °C; FW: 354.3 g/mol;
Anal. Calc. for C13H11ClCuN4: C, 44.03; H, 3.10; N, 15.80; Cu, 17.92. Found: C, 44.57; H,
2.84; N, 15.32; Cu, 17.70%. Main IR peaks (KBr, cm-1): ν(OH) 3347, ν(N4–H) 3290,
ν(C=N1) 1597, ν(C=S)+ ν(CN) 1250, ν(N–N) 1077, ꢀ(py) 642, ν(C–S) 519, ν(C=N2) 1543.
The complex is soluble in acetonitrile, chloroform, dichloromethane, acetone, DMF, DMSO
and warm methanol and ethanol.
[Cu(L)(Br)( H2O)2] 3 Dark green solid. Yield: 68%; M.p. 200–201 °C; FW: 434.7
g/mol; Anal. Calc. for: C13H15BrCuN4O2S: C, 35.88; H, 3.45; N, 12.88; Cu, 14.60. Found: C,
36.03; H, 3.31; N, 12.58; Cu, 14.47%. Main IR peaks (KBr, cm-1): ν(OH) 3343, ν(N4–H)
3288, ν(C=N1) 1596, ν(C=S)+ ν(CN) 1249, ν(N–N) 1077, ꢀ(py) 642, ν(C–S) 518, ν(C=N2)
1542. The complex is soluble in acetonitrile, acetone, chloroform, dichloromethane, DMF,
DMSO and warm methanol and ethanol.
[Cu(L)(OAc)(H2O)2] 4 Green solid. Yield: 51%; M.p. >220 °C; FW: 413.9 g/mol;
Anal. Calc. for: C15H18CuN4O4S: C, 43.49; H, 4.35; N, 13.53; Cu, 15.34. Found: C, 43.63; H,
4.12; N, 13.36; Cu, 15.11%. Main IR peaks (KBr, cm-1): ν(OH) 3392, ν(N4–H) 3253,
ν(C=N1) 1599, ν(C=S)+ ν(CN) 1254, ν(N–N) 1050, ꢀ(py) 616, ν(C–S) 519, ν(C=N2) 1549.
The complex is soluble in acetonitrile, acetone, chloroform, dichloromethane, DMF, DMSO
and warm methanol.
[Cu(HL)(H2O)](SO4) 5 Green solid. Yield: 72%; M.p. 201-202 °C; FW: 433.9 g/mol;
Anal. Calc. for C13H14CuN4O5S2: C, 35.95; H, 3.23; N, 12.90; Cu, 13.53. Found: C, 36.19; H,
3.02; N, 12.62; Cu, 13.05%. Main IR peaks (KBr, cm-1): ν(OH) 3348, ν(N4–H) 3290, ν(N2–
H) 3128, ν(C=N1) 1608, ν(C=S)+ ν(CN) 1250, ν(N–N) 1077, ν(C=S) 784, ꢀ(py) 642,
ν(C=N2) 1560. The complex is soluble in methanol, DMF, DMSO and warm acetonitrile,
acetone, and dichloromethane.
[Cu(L)(NO3)(H2O)2] 6 Dark green solid. Yield: 66%; M.p. >220 °C; FW: 416.9
g/mol; Anal. Calc. for C13H15CuN5O5S: C, 37.42; H, 3.60; N, 16.79; Cu, 15.23. Found: C,
37.88; H, 3.13; N, 16.42; Cu, 15.01%. Main IR peaks (KBr, cm-1): ν(OH) 3419, ν(N4–H)
3328, ν(C=N1) 1601, ν(C=S)+ ν(CN) 1250, ν(N–N) 1077, ꢀ(py) 642, ν(C–S) 514, ν(C=N2)
1562. The complex is soluble in methanol, DMF, DMSO and warm acetonitrile, acetone,
chloroform and dichloromethane.
[Cu(L)(ClO4)(H2O)2] 7 Green solid. Yield: 62%; M.p. >220 °C; FW: 454.3 g/mol;
Anal. Calc. for C13H15ClCuN4O6S: C, 34.34; H, 3.30; N, 12.33; Cu, 13.98. Found: C, 34.96;
H, 2.98; N, 12.12; Cu, 13.72%. Main IR peaks (KBr, cm-1): ν(OH) 3348, ν(N4–H) 3290,

ν(C=N1) 1600, ν(C=S)+ ν(CN) 1251, ν(N–N) 1077, ꢀ(py) 642, ν(C–S) 518, ν(C=N2) 1562.
The complex is soluble in ethanol, methanol, DMF and DMSO, and warm acetonitrile,
acetone, and dichloromethane.
2.4. Physical measurements
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 analyses were performed after drying the complexes at 105 °C. Infrared
spectra (4000-400 cm-1) were recorded on a Bruker Vertex 70 spectrophotometer, using KBr
pellets. The NMR spectra were recorded on a Varian Gemini 300 BB instrument operating at
300 MHz for a 1H and 75 MHz for 13C. Chemical shifts (δ, ppm) were assigned according to
the internal standard signal of TMS in DMSO-d6 (δ = 0 ppm). Coupling constants, J, are
expressed in hertz (Hz). Diffuse reflectance spectra were recorded on a Jasco V-670
spectrophotometer, using MgO dilution matrices. Electron paramagnetic resonance (EPR)
measurements were performed on polycrystalline powders and solutions DMSO, at room
temperature and 77 K, with an MiniScope MS200, Magnettech Ltd., X-band spectrometer
(9.3–9.6 GHz), connected to a PC equipped with a 100 kHz field modulation unit. The g
factors were quoted relative to the standard marker DPPH (g = 2.0036). The magnetic
susceptibility measurements were carried at room temperature in the polycrystalline state on a
Faraday magnetic balance (home-made). The complexes were studied by thermogravimetry
(TG) in static air atmosphere, with a sample heating rate of 10 °C/min using a STA 6000
Perkin Elmer. The molar conductance of the complexes in DMF (10-3 M), at room
temperature, were measured using a WTW inoLab Cond 720 conductivity instrument.
Antioxidant activity was measured on an Analytik Jena Specord 40 UV-Vis
Spectrophotometer.
2.5. X-ray crystallography
X-ray diffraction measurements for ligand were performed on a STOE IPDS II
diffractometer operating with a MoKα (λ = 0.71073 Å) X-ray tube with graphite
monochromator. Single crystal was positioned at 70 mm from the detector and 180 frames
were measured each for 60 s over 1° scan width. Crystallographic measurements for 1 and 2
were carried out on Oxford-Diffraction XCALIBUR E CCD diffractometer equipped with
graphite-monochromated MoKα radiation. The single crystals were positioned at 40 mm
from the detector and 406 and 401 frames were measured each for 30 and 160 s over 1° scan
width for 1 and 2, respectively. The unit cell determination and data integration were carried
out using the CrysAlis package of Oxford Diffraction [36a]. The structures were solved by
direct methods using Olex2 software [36b] with the SHELXS structure solution program and
refined by full-matrix least-squares on F² with SHELXL-97 [36c]. Atomic displacements for
non-hydrogen atoms were refined using an anisotropic model. All H atoms attached to carbon
atoms were inserted in idealised positions, riding on their carrier atoms. Positional parameters
of the H atoms attached to N atoms were obtained from difference Fourier syntheses and
verified by the geometric parameters of the corresponding hydrogen bonds. The Flack
parameter for ligand has been refined in order to evidence the presence of an enantiopure
compound. The molecular plots were obtained using the Olex2 program. The main
crystallographic data together with refinement details are summarized in Table 1, while
selected bond lengths are presented in Table 2.
Please insert Tables 1,2 - here

2.6. Antioxidant studies
2.6.1. DPPH radical scavenging activity assay
The antioxidant activity of the ligand and the metal complexes was measured in terms
of free radical scavenging ability using the stable radical 1,1-diphenyl-2-picrylhydrazyl
(DPPH) described by Blois method [37-39]. Briefly, the 120 µM solution of DPPH (2 ml) in
ethanol was added to tested sample solutions (2 ml) of different concentrations (50, 100, 150,
200, 250 and 500 µM) in DMF - ethanol 4:96 v/v. The samples were kept in the dark at room
temperature. After 30 min the absorbance values were measured at 517 nm and convert into
the percentage antioxidant activity (AA) using the formula AA%={1–[(Asample–Asample
blank)/Acontrol] · 100} [40], where Acontrol was the absorbance of DPPH solution, Asample was the
absorbance of sample solution with DPPH, Asample blank was the absorbance of the sample
solutions without the DPPH. All analyses were undertaken on three replicates and the results
averaged. The IC50 values were calculated by linear regression plots, where the abscissa
represented the concentration of tested compound solution and the ordinate the percent of
scavenging effect. Butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA)
were used as standards.
2.6.2. ABTS radical scavenging activity assay
The ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)] assay is based
on the ability of the antioxidants to scavenge the long-life radical cation ABTS•+ [41]. The
blue color radical cation ABTS•+ is generated by oxidation of ABTS with potassium
persulfate. ABTS was dissolved in water to a 7 µM concentration (stock solution). ABTS
radical cation (ABTS•+) was produced by reacting ABTS stock solution with 2.45 µM
potassium persulfate (1:1 v/v) and kept in the dark at room temperature for 12–16 h before
use. Prior to assay, this solution was diluted in ethanol and equilibrated at 30°C to give an
absorbance of 0.7000 0.02 at 734 nm. Then, 2 ml ABTS solution was added to tested
sample solutions (2 ml) of different concentrations (15, 20, 25, 30 and 50 µM) in DMF -
ethanol 4:96 v/v. The absorbance of the samples was measured at 734 nm, 6 minutes after
initial mixing and convert into the percentage antioxidant activity (AA) using the formula
AA%={1–[(Asample–Asample blank)/Acontrol] · 100} [40], where Acontrol was the absorbance of
ABTS solution, Asample was the absorbance of sample solution with ABTS, Asample blank was
the absorbance of the sample solutions without the ABTS. All determinations were
performed in triplicate. The IC50 values were calculated by linear regression plots, where the
abscissa represented the concentration of tested compound solution and the ordinate the
percent of scavenging effect. Butylated hydroxytoluene (BHT) and butylated hydroxyanisole
(BHA) were used as standard or positive control.
3. Results and discussion
The thiosemicarbazone ligand was synthesized in good yield and characterized by
1
13
UV-Vis, FT-IR, H NMR and C NMR spectroscopy and X-ray diffraction. The synthesis of
the complexes is reproducible and 2-formilpyridine N(4)-phenylthiosemicarbazone
coordinates as a tridentate ligand through the Npy–N–S chelating system, which was
confirmed by the X-ray structure determinations for complexes 1 and 2. The molar
conductivity values (23-55 Ω-1 cm2 mol-1) of complexes 2 - 4, 6 and 7 in 10-3 M DMF
solution show that they are non-electrolytes, except for complex 1 and 5 (70 and 86 Ω-1 cm2

mol-1) which is an electrolyte [7,42]. For complexes 3 - 4, and 6 the thermogravimetric
analyses show a weight loss between 190°C and 250°C which corresponds to two water
molecules directly bonded to the metal center [16]. For complex 5 the thermogravimetric data
show a weight loss between 190°C and 230°C which corresponds to one water molecule
directly bonded to the metal center [16]. The elemental analyses data of the
thiosemicarbazone and metal complexes (reported in Section 2) are in agreement with
structure of the ligand (Scheme 1) and with the proposed structures of the complexes
(Scheme 2).
Please insert Scheme 1- here
Please insert Scheme 2- here
3.1. Structural characterization of [Ni(HL)2]Cl2 2.5H2O(1) and [Cu(L)Cl] (2)
The single-crystal X-ray diffraction study has revealed that the ligand crystalizes in
form of chlorhydrate salt HL·HCl, as shown in Fig. 1.
Please insert Fig. 1- here
In the crystal structure of the ligand, the ionic components are connected by NH···Cl
hydrogen bonds generating a system of parallel packed wave-like tapes, running along [010].
A partial expansion in the one-dimensional hydrogen-bonded structure is illustrated in Fig. 2.
Please insert Fig. 2- here
In the supramolecular structure of the ligand, the above mentioned tapes are extended
through the weak inter-cationic CH···S interactions giving a two-dimensional and further a
three-dimensional supramolecular network (Fig. A1 (Supplementary information)).
Complexes 1 and 2 crystallize with two independent molecules of complex (A and B)
in the asymmetric part of the unit cell. The crystal structure of complex 1 comprises
[Ni(HL)2]2+ complex cations and severely disordered Cl- and solvate H2O molecules in
1:2:2.5 molar ratio. As an example, the structure of the complex cation A is shown in Fig. 3.
The nickel(II) atoms in both complex cations A and B exhibit a slightly distorted octahedral
N4S2 coordination (Table 2) provided by two tridentate non-deprotonated ligand molecules.
Please insert Fig. 3 - here
The crystal structure packing of complex 1 is determined by an extensive system of
NH···Cl, OH···Cl, NH···O and OH···O hydrogen bonds and π-π stacking interactions (the
shortest centroid-centroid distance of 3.815 and 3.896 Å), which link the different chemical
species into three-dimensional supramolecular architecture (Fig. A2 (Supplementary
information)).
The result of X-ray diffraction study of the complex 2 is presented in Fig. 4. The
copper atoms exhibit the same distorted square-planar coordination environment in two
crystallographic independent molecules, provided by one tridentate deprotonated ligand
molecule and one chloride anion.
Please insert Fig. 4 - here

The two molecules of complex 2 (A and B) are associated through a NH···Cl
hydrogen bond. In the crystal structure of complex 2, the A-B di-molecular associates are
further self-assembled via NH···S hydrogen bonding forming two-dimensional
supramolecular layers parallel to (101), which are strongly consolidated by π-π stacking
interactions. Cg1···Cg2i and Cg1···Cg2ii contacts are equal to 3.996 Å and 3.758 Å with
2.052 Å and 1.609 Å shift distances, respectively (Cg1 and Cg2 are the centroids of C8B-
C13B and N1B/C1B–C5B, respectively; symmetry codes: (i) 1 - x, 1 - y , -z; (ii) 2 - x, 1 - y , -
z) (Fig. A3 (Supplementary information)).
3.2. Infrared spectra
The IR spectrum of the ligand exhibited –NH stretching vibrations at 3308 cm-1 for
N4H and 3126 cm-1 for N2H [22,27,43]. The strong band assigned to ν(N4H) in the spectrum
of HL is shifted downwards with 20 - 55 cm-1 in all the complexes. Except for complexes 1
and 5, the –N2H stretching vibrations disappears in the spectra of all complexes, thus
indicating the coordination of the ligand to the metal ion in its deprotonated form [27]. The
strong band assigned to ν(C=N) in the spectrum of the free ligand appears at 1598 cm-1 and is
shifted with up to 10 cm-1 in all the complexes, thus suggesting the coordination of the
azomethine nitrogen to the metal center [22,26,27,29].
The presence of a strong absorption band ν(C=S) at 774 cm-1 in the ligand spectrum
suggests that the thiosemicarbazone is found in the thione form in solid state [22,29]. Upon
complexation this band is shifted with up to 23 - 28 cm-1 in all the complexes, except for
complexes 1 and 5 where it is found at 771 and 784 cm-1, respectively [7]. The band at 1257
cm-1 [ν(CS) + ν(CN)] is shifted to 1242 - 1254 cm-1 in the spectra of all complexes [44].
Also, a new absorbtion band appears în the range 514 - 519 cm-1 in the spectra of all
complexes, except for complexes 1 and 5. Thus, indicating the coordination of the ligand in
its deprotonated form in the copper(II) complexes except for complex 5 [45]. The in-plane
deformation mode of the pyridine ring at 622 cm-1 in the ligand IR spectrum shifts to 642 cm-
1
in the nickel(II) and copper(II) complexes, suggesting the coordination of the pyridine
nitrogen [7,22,26,46-48]. This showing that the thiosemicarbazone acts as a tridentate ligand
through NNS set of donor atoms.
The IR spectrum of complex 4 shows two strong bands at 1600 and 1353 cm-1,
corresponding to νa(COO–) and νs(COO–), respectively with ∆(νa–νs) = 247 cm-1. This is
consistent with the monodentate nature of the coordinated acetate ion [49,50]. For the
sulphate complex 5 the presence of strong and medium absorption bands at 1101 (ν3), 978
(ν1), and 618 (ν4) cm-1 indicates the presense of the SO42- ion [49]. The IR spectra of complex
6 shows three bands at 1490, 1384 and 1072 cm-1 which are assignable to ν5, ν1 and ν2 of the
monodentate coordinated nitrate group. The difference between frequencies ν5 and ν1 is 106
-
cm-1 [45,49]. The presence of the ClO4 ion in the complex 7 is indicated by the absorption
bands at 1130 and 1022 cm-1 which suggest the presence of the monodentate coordinated
perchlorate ion coordinated to the metal ion [49].
3.3. Electronic spectra
In Table 3 are given the significant electronic absorption bands from the spectra of
metal complexes, in solid state along with the values for magnetic moment. The absorption
bands showed by the electronic spectrum of the free ligand in the regions 44 000 - 35 700 cm-
1
and 31 250 - 23 810 cm-1 were assigned to π→π* and n→π transitions, respectively [51].
Upon complexation, these transitions were shifted by appropriate amounts.

The various absorption bands from the electronic spectrum of the nickel(II) complex
3
3
-1 3
3T1g(F)
→
→
were assigned to transitions as follows: A2g(F)
T1g(P) at 22 830 cm , A2g(F)
at 12 270 cm-1 and 3A2g(F) → 3T2g(F) at 10 310 cm-1 [10]. The magnetic moment value (2.38)
of complex 1 correspounds to two unpaired electrons per metal ion.
Except for complex 5, all the copper(II) complexes show absorption bands in the area
15 880 - 19 610 cm-1 and 12 500 - 14 000 cm-1 that were assigned to the d–d transitions:
2
2B1g→2Eg and B1g→2B2g, respectively. These transitions indicate an axial distorted
octahedral geometry of the copper(II) ion [50,52]. For complex 5, the electronic spectrum
shows an absorption band at 17 100 cm-1 which was attributed to the d–d transitions:
2
2B2→2B1 and B2→2A1, suggesting a pseudo-tetrahedral geometry for the metal center. The
magnetic moment values (1.70 - 2.08 BM) for the copper(II) complexes correspounds to one
unpaired electrons per metal ion.
Please insert Table 3- here
3.4. EPR spectra
The EPR spectra of the copper(II) complexes were recorded in the polycrystalline
state and DMSO solution to provide information about the coordination environment around
the copper(II) ion. The EPR spectral parameters of the Cu(II) complexes 2 - 7 in the
polycrystalline state at 298 K and in DMSO solution at 298 and 77 K are presented in Table
5.
Please insert Table 4- here
The EPR spectra recorded in the polycrystalline state of the complexes 2 and 5 show
rhombic behavior with g tensor values g1, g2 and g3 (Fig. 5).
Please insert Figure 5- here
For complex 3 the EPR spectrum consists in a symmetric signal located at go = 2.091.
The spectra of the complexes 4, 6 and 7 show typical axial behavior with tensor values of g//
d
> g﬩> 2.002 which are consistent with a
ground state [44,53].
x2 −y2
The geometric parameter, G quantifies the exchange interaction between copper
centers in a polycrystalline compound. It is calculated using the equation G = (g//–2)/(g﬩–2)
for axial spectra. G values less than 4.0 indicate a small exchange coupling, while G values
higher than 4.0 indicate that the exchange interaction is negligible [9,45]. For complexes 2
and 5 there is a small exchange interaction between copper centers, G < 4, and for complexes
4, 6 and 7 the exchange interaction is negligible as G > 4.
In Fig. 6 are given the EPR spectra of complexes 2 - 7 recorded in DMSO solution at
298 K. All EPR spectra of the copper(II) complexes show three of the four lines of hyperfine
structure characteristic for the d9 copper ion. Also in the second derivative of these spectra
can be observed, in the high field component, four or five nitrogen superhyperfine lines.
Please insert Figure 6 - here

The EPR spectra of the compounds 2 - 7 recorded in DMSO solution at 77 K show
d
typical axial behavior with tensor values of g// > g﬩> 2.002 which are consistent with a
ground state [44,53].
x2 −y2
Please insert Figure 7 - here
The bonding parameters α2, β2 and δ2, are considered as being measures of the
covalency of the in-plane σ bonds, in-plane π bonds and out-of-plane π bonds [45,54,55]. For
all copper(II) complexes the values of reduction factor K﬩ are higher than K// which is
consisted with in-plane π bonding (Table 3) [55-57]. The empirical factor f = g///A// (cm-1)
[45,58] is an index of tetragonal distortion. The f value for complex 2 is 119 indicating a
small distortion from planarity.
3.5. Antioxidant activity
In order to highlight the ability of the thiosemicarbazone metal complexes to interact
with different reactive radical species, the ligand and its nickel(II) and copper(II) complexes
were screened for reduction of DPPH and ABTS free radicals.
3.5.1. DPPH radical scavenging activity assay
DPPH (1,1-diphenyl-2-picrylhydrazyl radical) is a well-known stabil free radical of
violet color and under the action of antioxidant compounds is reduced to yellow color and
this change can be monitored at 517 nm [37-39]. The free radical scavenging effect of the
ligand and complexes 1 - 7 at different concentrations 25 - 250 µM by DPPH method is
presented in Table 5 and Fig. 8. The IC50 values (µM) are showed in Table 5. Low values of
IC50 indicate a higher efficiency in DPPH radical scavenging capacity.
Please insert Table 5 - here
From the tested compounds, the ligand and complexes 1, 2 and 7 exhibited a good
DPPH free radical scavenging effect, while complexes 3 - 6 showed a low antioxidant
activity. In the concentrations range 75 - 250 µM, the nickel(II) complex exhibited the higher
antioxidant activity, slightly higher than that of the BHA standard (Fig. 8). In the range of
concentrations used, for complex 4, the scavenging effect did not exceed 5%. Also, the DPPH
free radical scavenging effect of complexes 3 - 6 did not exceed 50% at a concentration of
250 µM.
Please insert Figure 8 - here
In terms of IC50 (µM), the thiosemicarbazone ligand and complexes 1, 2, 7 were found
to be more active than BHT standard. Nevertheless, the complexes 1 and 7 have comparable
IC50 (µM) values with that of BHA.
3.5.2. ABTS radical scavenging activity assay
ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)) radical cation
decolorization assay is a method for screening of antioxidant activity applicable to both
lipophilic and hydrophilic antioxidants [41]. The free radical scavenging activity of the ligand

and complexes 1 - 7 at different concentrations 7.5 - 25 µM by ABTS assay is presented in
Table 6 and Fig. 9. Also, the IC50 values (µM) are showed in Table 6, low values of IC50
indicating a higher efficiency in ABTS•+ radical scavenging activity.
Please insert Table 6 - here
All tested compounds exhibited good scavenging activity against radical cation
ABTS•+. The copper(II) complexes and ligand proved to be more efficient at scavenging the
radical cation ABTS•+ than the nickel(II) complex. Surprisingly, complex 1 showed the lower
scavenging effect against radical cation ABTS•+. Also, the ligand HL and complex 3
exhibited the higher antioxidant activity at concentration of 7.5 - 25 µM. The dependence
observed is correlated with data obtained for other copper(II) complexes [59] and is
essentially rectilinear with determination coefficients within 0.93 - 0.99.
Please insert Figure 9 - here
Regarding the IC50 values, the antioxidant activity of the metal complexes and ligand
assessed by ABTS method is lower than those of BHA and BHT standards. Also, it can be
observed that the IC50 values for the copper(II) complexes vary with the counter ion
-
-
coordinated to the metal center in the series ClO4 < NO3 < OAc- < Cl- < Br-.
4. Conclusions
New nickel(II) and copper(II) complexes derived from 2-formilpyridine N(4)-
phenylthiosemicarbazone have been synthesized and characterized. The thiosemicarbazone
acts both as non-deprotonated and deprotonated tridentate ligand coordinating to the metal
center through the Npy–N–S chelating system. In the complex 1, the nickel atom exhibits a
slightly distorted octahedral coordination environment provided by the two molecules of
ligand that coordinate in a non-deprotonated tridentate manner. For complex 2, the copper
atom exhibits a distorted square-planar environment provided by one molecule of
deprotonated tridentate ligand and one chloride anion.
The values of α2, β2 and δ2 for the copper(II) complexes show strong in-plane π
bonding.
The antioxidant activity of the ligand and its metal complexes was studied by DPPH
and ABTS free radical scavenging methods. The ligand and complexes 1, 2 and 7 complexes
exhibited a very good scavenging activity against DPPH free radical. On the other hand, the
ligand and complex 3 exhibited the higher antioxidant activity against radical cation ABTS•+.
Acknowledgements
The authors thank the Organic Chemistry Department, ICECHIM Bucharest
(Romania) for microanalysis, ‘‘Horia Hulubei’’ National Institute of Physics and Nuclear
Engineering Bucharest for help with EPR spectroscopy. Supported by National Authority for
Scientific Research of Ministry of Education and Research, Bucharest, Romania (PN II,
Grant No. 42-128/2008). This research was financially supported by European Regional
Development Fund, Sectorial Operational Program ‘‘Increase of Economic
Competitiveness’’, Priority Axis 2 (SOP IEC-A2-O2.1.2-2009- 2, ID 570, CODSMIS-CSNR:
12473, Contract 129/2010-POLISILMET.
Appendix A. Supplementary data

CCDC-1041418 (HL·HCl), 1041064 (1) and 1041065 (2) contains the supplementary
crystallographic data for this contribution. These data can be obtained free of charge via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or
deposit@ccdc.ca.ac.uk).
Supplementary data related to crystallographic data can be found in Figs. A1 - A3.
References
[1] M. Yildiz, H. Unver, D. Erdener, A. Kiraz, N. O. Iskeleli, J. Mol. Struct. 919 (2009) 227-
234.
[2] J.S. Casas, M.S. Garcia-Tasende, J. Sordo, Coord. Chem. Rev. 209 (2000) 197-261.
[3] T.S. Lobana, R. Sharma, G. Bawa, S. Khanna, Coord. Chem. Rev. 253 (2009) 977-1055.
[4] D. Pandiarajan, R. Ramesh, Y. Liu, R. Suresh, Inorg. Chem. Commun. 33 (2013) 33-37.
[5] A. Ramdass, V. Sathish, M. Velayudham, P. Thanasekaran, K.-L. Lu, S. Rajagopal, Inorg.
Chem. Commun. 35 (2013) 186-191.
[6] S.I. Orysyk, V.V. Bon, O.O. Zholob, V.I. Pekhnyo, V.V. Orysyk, Yu.L. Zborovskii, M.V.
Vovk, Polyhedron 51 (2013) 211-221.
[7] J.A. Lessa, D.C. Reis, I.C. Mendes, N.L. Speziali, L.F. Rocha, V.R.A. Pereira, C.M.L.
Melo, H. Beraldo, Polyhedron 30 (2011) 372-380.
[8] M.A. Hussein, T.S. Guan, R.A. Haque, M.B. Khadeer Ahamed, A.M.S. Abdul Majid,
Inorganica Chim. Acta 421 (2014) 270-283.
[9] M. Joseph, M. Kuriakose, M.R.P. Kurup, E. Suresh, A. Kishore, S.G. Bhat, Polyhedron
25 (2006) 61-70.
[10] T.S. Lobana, P. Kumari, G. Hundal, R.J. Butcher, Polyhedron 29 (2010) 1130-1136.
[11] H. Elo, Z. Naturforsch 62c (2007), 498-506.
[12] D.L. Klayman, J.F. Bartoserich, T.S. Griffin, C.J. Mason, J.P. Scovill, J. Med. Chem. 22
(1979) 885-893.
[13] A. Castineiras, I. Garcia-Santos, E. Bermejo, D. X. West, Polyhedron 19 (2000) 1873-
1880.
[14] I. García-Santos, A. Hagenbach, U. Abram, Dalton Trans. (2004) 677-682.
[15] I. García-Santos, U. Abram, R. Alberto, E. Vazquez-López, Inorg. Chem. 43 (2004)
1834-1836.
[16] U. El-Ayaan, M.M. Youssef, S. Al-Shihry, J. Mol. Struct. 936 (2009) 213-219.
[17] E. Bermejo, A. Castiñeiras, I. García-Santos, D. X. West, Polyhedron 22 (2003) 1147-
1154.
[18] M. del Carmen Aguirre, J. Borras, A. Castineiras, J.M. Garcia-Monteagudo, I. Garcia-
Santos, J. Niclos, D.X. West, Eur J Inorg Chem (2006) 1231-1244.
[19] T.S. Lobana, G. Bawa, R.J. Butcher, C.W. Liu, Z. Anorg. Allg. Chem. 635 (2009) 355-
360.
[20] M.A. Demertzis, P.N. Yadav, D. Kovala-Demertzi, Helv. Chim. Acta 89 (2006) 1959-
1970.
[21] D. Kovala-Demertzi, U. Gangadharmath, M.A. Demertzis, Y. Sanakis, Inorg. Chem.
Commun. 8 (2005) 619-622.
[22] I.C. Mendes, F.B. Costa, G.M. de Lima, J.D. Ardisson, I. Garcia-Santos, A. Castiñeiras,
H. Beraldo, Polyhedron 28 (2009) 1179-1185.
[23] T.S. Lobana, Rekha, R. J. Butcher, A. Castineiras, E. Bermejo, P.V. Bharatam, Inorg.
Chem. 45 (2006) 1535-1542.
[24] T.S. Lobana, R. Sharma, A. Castineiras, R.J. Butcher, Z. Anorg. Allg. Chem. 636 (2010)
2698-2703.

[25] U. Abram, K. Ortner, R. Gust, K. Sommer, J. Chem. Soc., Dalton Trans. (2000) 735-
744.
[26] K.O. Ferraz, S.M.S.V. Wardell, J.L. Wardell, S.R.W. Louro, H. Beraldo,
Spectrochim. Acta A Mol. Biomol. Spectrosc. 73 (2009) 140-145.
[27] P.I. da S. Maia, A. Graminha, F.R. Pavan, C.Q.F. Leite, A.A. Batista, D.F. Back, E.S.
Lang, J. Ellena, S. de S. Lemos, H.S. Salistre-de-Araujo, V.M. Deflon, J. Braz. Chem. Soc.
21 (2010) 1177-1186.
[28] S.A. Elsayed, A.M. El-Hendawy, S.I. Mostafa, B.J. Jean-Claude, M. Todorova, I.S.
Butler, Bioinorg. Chem. Appl. (2010)149149.
[29] J.G. da Silva, L.S. Azzolini, S.M.S.V. Wardell, J.L. Wardell, H. Beraldo, Polyhedron 28
(2009) 2301-2305.
[30] P.I. da S. Maia, F.R. Pavan, C.Q.F. Leite, S.S. Lemos, G.F. de Sousa, A.A. Batista, O.R.
Nascimento, J. Ellena, E.E. Castellano, E. Niquet, V.M. Deflon, Polyhedron 28 (2009) 398-
406.
[31] C.R. Kowol, R. Trondl, V.B. Arion, M.A. Jakupec, I. Lichtscheidl, B.K. Keppler, Dalton
Trans. 39 (2010) 704-706.
[32] M. Yang, Y.-L. Lu, M.-X. Li, X.-W. Xu, L. Chen, Inorg. Chem. Commun. 35 (2013)
117-121.
[33] C.R. Kowol, P. Heffeter, W. Miklos, L. Gille, R. Trondl, L. Cappellacci, W. Berger,
B.K. Keppler, J. Biol. Inorg. Chem. 17 (2012) 409-423.
[34] A. Popovic-Bijelic, C.R. Kowol, M.E.S. Lind, J. Luo, F. Himo, E.A. Enyedy, V.B.
Arion, A. Gräslund, J. Inorg. Biochem. 105 (2011) 1422-1431.
[35] D.D. Perrin, W.L. Armarego, D.R. Perrin, Purification of Laboratory Chemicals, second
ed., Pergamon, New York, 1990.
[36] (a) CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.36.32, 200; (b) O.V.
Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H. Puschmann, J. Appl. Cryst. 42
(2009) 339-341; (c) G. M. Sheldrick, SHELXS, Acta Cryst. A64, (2008) 112-122.
[37] M.S. Blois, Nature. 26 (1958) 1199-1200.
[38] P. Anitha, N. Chitraptiya, Y.J. Jang, P. Viswanathamurthi, J. Photochem. Photobiol. B.
129 (2013) 17-26.
[39] S. Shobana, P. Subramaniam, L. Mitu, J. Dharmaraja, S.A. Narayan,
Spectrochim. Acta A Mol. Biomol. Spectrosc. 134 (2015) 333-344.
[40] X.-J. Duan, W.-W. Zhang, X.-M. Li, B.-G. Wang, Food Chem. 95 (2006) 37-43.
[41] R. Re, N. Pellegrini, A. Proteggente, A. Pannala, M. Yang, C. Rice-Evans, Free Radic.
Biol. Med. 26 (1999) 1231-1237.
[42] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81-121.
[43] T.S. Lobana, G. Bawa, A. Castineiras, R.J. Butcher, Inorg. Chem. Commun. 10 (2007)
506-509.
[44] P.F. Rapheal, E. Manoj, M.R. Prathapachandra Kurup, Polyhedron 26 (2007) 818-828.
[45] K. Jayakumar, M. Sithambaresan, A. Ambili Aravindakshan, M.R. Prathapachandra
Kurup, Polyhedron 75 (2014) 50-56.
[46] I.C. Mendes, L.M. Botion, A.V.M. Ferreira, E.E. Castellano, H. Beraldo, Inorganica
Chim. Acta 362 (2009) 414-420.
[47] A.P. Rebolledo, M. Vieites, D. Gambino, O.E. Piro, E.E. Castellano, C.L. Zani, E.M.
Souza-Fagundes, L.R. Teixeira, A.A. Batista, H. Beraldo, J. Inorg. Biochem. 99 (2005) 698-
706.
[48] A.P. Rebolledo, G.M. de Lima, L.N. Gambi, N.L. Speziali, D.F. Maia, C.B. Pinheiro,
J.D. Ardisson, M.E. Cortes, H. Beraldo, Appl. Organometal. Chem. 17 (2003) 945-951

[49] (a) K. Nakamoto, Infrared Spectra of Inorganic and Coordination Compounds, Wiley
and Sons, New York, 1986; (b) K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, fifth ed., Wiley-Interscience, New York, 1997.
[50] D.X. West, J.K. Swearingen, A.K. El-Sawaf, Trans. Met. Chem. 25 (2000) 80-83.
[51] b) M. Belicchi-Ferrari, F. Bisceglie, G. Pelosi, P. Tarasconi, Polyhedron 27 (2008) 1361-
1367.
[52] N. Raman, A. Selvan, P. Manisankar, Spectrochim. Acta A Mol. Biomol. Spectrosc. 76
(2010) 161-173.
[53] S. Chandra, Vandana, Spectrochim. Acta A Mol. Biomol. Spectrosc. 29 (2014) 333-338.
[54] A.H. Maki, B.R. McGarvey, J. Chem. Phys. 29 (1958) 31-34.
[55] R.N. Patel, A. Singh, K.K. Shukla, D. K. Patel, V.P. Sondhiya, J. Coord. Chem. 64
(2011) 902-919.
[56] B.J. Hathaway, in: G. Wilkinson, D.R. Gillard, A.J. McCleverty (Eds.), Comprehensive
Coordination Chemistry, Pergamon Press, New York, 1987.
[57] (a) B.J. Hathaway, Structure and Bonding, Springer Verlag, Heidelberg, 1973, p.60; (b)
B.N. Figgis, Introduction to Ligands Fields, Interscience, New York, 1966.
[58] R. Pogni, M.C. Bartoo, A. Diaz, R. Basosi, J. Inorg. Biochem. 79 (2000) 333-337.
[59] M. Grazul, A. Kufelnicki, M. Wozniczka, I.P. Lorenz, P. Mayer, A. Jozwiak, M. Czyz,
E. Budzisz, Polyhedron 31 (2012) 150–158.

H
H
H
10
13
5
2
N
4
N
3
C7
8
6
11
12
4
3
N
2
C
9
N
S
14
1
Scheme 1. 2-formylpyridine N(4)-phenylthiosemicarbazone (HL).

OH2
2+
H
H
H
N
N
N
N
H
N
H
N
N
S
N
S
2-
SO4
Cu
Cu
X
OH2
OH2
-
-
-
- ( ).
7
( )
5
X = Br
, OAc
, NO
, ClO
4
( )
3
( )
4
( )
6
3
Scheme 2. Proposed structures for the copper(II) complexes 3-7.

Fig. 1. View of the asymmetric unit in the crystal structure of HL·HCl,
showing 50% probability displacement ellipsoids and the atom labelling.

Fig. 2. Supramolecular hydrogen-bonding tape in the structure of HL·HCl.
H-bond parameters: N1−H···Cl1 [N1−H 0.86 Å, H···Cl1 2.19 Å, N1···Cl1(-x + 1/2, y + 1/2, z)
3.0102(2) Å, N1−H···Cl1 159.5°]; N3−H···Cl1 [N3−H 0.86 Å, H···Cl1 2.40 Å, N3···Cl1 3.258(2) Å,
N3−H···Cl1 171.5°]; N4−H···Cl1 [N4−H 0.86 Å, H···Cl1 2.68 Å, N1···Cl1(-x + 1/2, y + 1/2, z)
3.490(2) Å, N1−H···Cl1 157.6°].

Fig. 3. X-ray structure of the complex cation [Ni(HL)2]2+ in the crystal structure of 1.
Thermal ellipsoids are drawn at 40% probability level.

Fig. 4. Two independent molecules [Cu(L)Cl] (2) in the asymmetric unit of crystal structure of
complex 2, with atom labeling. Displacement ellipsoids drown at 50% probability level. H-bond
parameters: N4B−H···Cl1A [N4B−H 0.86 Å, H···Cl1A 2.55 Å, N4B···Cl1A(1 - x,1 - y, -z) 3.321(5) Å,
N4A−H···Cl1A 149.2°]

g
3
2 - a
5 - a
g
2
g
1
2 - d2
5 - d2
g
g
3
1
g
2
2600
2800
3000
3200
3400
3600
H (Gauss)
Fig. 5. (a) EPR spectra of complexes 2 and 5 in the polycrystalline state at 298 K;
(d2) second derivative spectra at 298 K.

2
3
4
5
6
7
2600
2800
3000
3200
3400
3600
H (Gauss)
Fig. 6. EPR spectra of complexes 2 - 7 in DMSO solution at 298 K.

g
//
A
//
2
3
4
5
6
7
2600
2800
3000
3200
3400
3600
H (Gauss)
Fig. 7. EPR spectra of complexes 2 - 7 in DMSO solution at 77 K.

100
80
60
40
20
0
HL
1
2
3
4
5
6
7
BHT
BHA
0
50
100
150
200
250
300
350
Concentration (µM)
Fig. 8. The scavenging effect of the ligand HL, complexes 1 - 7,
BHT and BHA standards by DPPH method.

100
80
60
40
20
0
HL
1
2
3
4
5
6
7
BHT
BHA
5
10
15
20
25
30
Concentration (µM)
Fig. 9. The scavenging effect of the ligand HL, complexes 1 - 7,
BHT and BHA standards by ABTS method.

Table 1
Crystallographic data, details of data collection and structure refinement parameters for HL·HCl, 1
and 2.
HL·HCl
1
2
Empirical formula
Formula weight
C13H13ClN4S
292.78
C52H58Cl4N16Ni2O5S4
1374.60
C26H22Cl2Cu2N8S2
708.62
Temperature/K
293
200
293
Crystal system
Space group
orthorhombic
Pb21a
triclinic
P-1
triclinic
P-1
a/Å
b/Å
c/Å
α/°
7.6953(7)
13.0411(11)
13.9370(16)
90.00
90.00
90.00
1398.7(2)
4
1.390
11.8754(5)
12.1336(5)
24.4297(11)
87.272(3)
89.189(4)
63.015(4)
3133.2(2)
2
6.9987(5)
14.0110(15)
15.2515(12)
107.959(8)
94.955(6)
97.865(7)
1396.1(2)
2
β/°
γ/°
V/Å3
Z
Dcalc/mg/mm3
µ/mm-1
1.457
0.963
1.686
1.898
0.414
Crystal size/mm3
θmin, θmax(o)
Reflections collected
Independent reflections
Data/restraints/parameters
0.15 × 0.30 × 0.60
5.84 to 52.74
7670
2743 [Rint = 0.0226]
2734/1/172
0.0285
0.0610
1.029
0.11/-0.17
-0.02(5)
0.05 × 0.20 × 0.40
3.98 to 52.74
24504
12763 [Rint = 0.0378]
12763/0/774
0.0631
0.1558
1.030
0.90/-0.91
-
0.01 × 0.07 × 0.18
6.2 to 52.74
9993
5695 [Rint = 0.0500]
5695/0/361
0.0671
0.1319
1,035
1.00/-0.49
-
a
R1 (I > 2σ(I)
b
wR2 (all data)
GOFc
Largest diff. peak/hole/e Å‒3
Flack parameter
2
aR1 = Σ||Fo| - |Fc||/Σ|Fo|, bwR2 = {Σ[w (Fo2 - Fc2)2] /Σ[w(Fo )2 ]}1/2
.
cGOF = {Σ[w(Fo2 - Fc2)2]/(n – p)}1/2, where n is the number of reflections and p is the total number of parameters refined.

Table 2
Selected bond lenghts (Å) for HL·HCl, 1 and 2.
2
1
Molecule A
HL·HCl
Molecule B
Ligand
Molecule A
Molecule B
A
B
C
D
C1-C2
C1-N1
C2-C3
1.365(3)
1.330(3)
1.374(3)
1.378(3)
1.377(2)
1.454(3)
1.344(2)
1.277(2)
1.368(2)
1.335(2)
1.669(2)
1.380(3)
1.379(3)
1.426(2)
1.388(3)
1.362(4)
1.362(4)
1.383(3)
1.356(2)
1.374(6)
1.339(5)
1.358(7)
1.374(7)
1.373(6)
1.390(6)
1.339(5)
1.352(7)
1.387(7)
1.381(6)
1.457(6)
1.338(6)
1.283(5)
1.357(5)
1.339(5)
1.688(4)
1.389(6)
1.376(7)
1.428(6)
1.385(8)
1.375(9)
1.356(8)
1.370(7)
1.366(4)
2.114(3)
2.001(4)
2.410(1)
1.381(6)
1.335(5)
1.371(7)
1.364(7)
1.391(6)
1.443(6)
1.350(5)
1.282(5)
1.364(5)
1.334(5)
1.690(5)
1.380(7)
1.380(7)
1.423(6)
1.401(7)
1.354(9)
1.369(9)
1.378(7)
1.363(5)
2.109(3)
2.019(3)
2.422(1)
1.380(6)
1.336(5)
1.376(7)
1.367(7)
1.375(6)
1.377(8)
1.333(6)
1.365(8)
1.387(7)
1.366(7)
1.465(7)
1.340(7)
1.267(6)
1.302(7)
1.357(6)
1.753(6)
1.386(7)
1.397(7)
1.404(6)
1.369(7)
1.384(8)
1.362(9)
1.389(8)
1.324(7)
1.368(9)
1.370(8)
1.378(7)
1.446(8)
1.343(7)
1.276(6)
1.313(7)
1.348(7)
1.755(6)
1.375(7)
1.384(7)
1.415(7)
1.374(8)
1.371(8)
1.382(8)
C3-C4
C4-C5
C5-C6
1.470(6)
1.350(5)
1.274(5)
1.368(5)
1.336(5)
1.687(4)
1.373(6)
1.364(6)
1.425(5)
1.390(7)
1.356(7)
1.359(7)
1.382(7)
1.346(4)
2.072(3)
2.011(3)
2.407(1)
1.463(6)
1.345(5)
1.290(5)
1.357(5)
1.345(5)
1.686(4)
1.387(6)
1.371(7)
1.427(5)
1.374(7)
1.365(8)
1.365(8)
1.392(7)
1.350(5)
2.081(3)
2.010(3)
2.409(1)
C5-N1
C6-N2
C7-N3
C7-N4
C7-S1
C8-C9
C8-C13
C8-N4
C9-C10
C10-C11
C11-C12
C12-C13
N2-N3
Ni1-N1
Ni1-N2
Ni1-S1
Cu1-Cl1
1.363(7)
1.384(5)
1.377(8)
1.364(6)
2.010(4)
2.033(5)
1.963(4)
2.248(2)
1.966(5)
2.252(2)
2.227(2)
2.223(2)

Table 3
Electronic spectral assignments (cm-1) for the complexes 1 - 7.
Compound
Transitions d–d (cm-1)
µeff Geometry
(MB)
3
3
3
3
3
3
→
→
→
A2g(F) T2g(F) A2g(F) T1g(F) A2g(F) T1g(P)
[Ni(HL)2]Cl2 ·2.5H2O (1)
10 310
2B1g→ 2B2g
12 270
18 520
2B1g→ 2Eg
2.38 octahedral distorted
[Cu(L)(Cl)] (2)
[Cu(L)(Br)( H2O)2] (3)
[Cu(L)(OAc)(H2O)2] (4)
12 500
12 900
13 000
16 950
16 810
16 670
1.70 square planar
2.01 octahedral distorted
2.04 octahedral distorted
2B2→ 2B1, 2B2→ 2A1
[Cu(HL)(H2O)](SO4) (5)
1.96 pseudo-tetrahedral
17 100
[Cu(L)( NO3)(H2O)2] (6)
[Cu(L)(ClO4)(H2O)2] (7)
12 660
14 000
15 880
17 240
2.08 octahedral distorted
1.72 octahedral distorted

Table 4
EPR spectral parameters for copper (II) complexes 2 - 7.
2
3
4
5
6
7
Polycrystalline (298K)
g//
g﬩
2.039 (g1)
2.081 (g2)
2.121 (g3)
2.157
2.041
2.040 (g1)
2.083 (g2)
2.122 (g3)
2.187
2.044
2.160
2.039
2.091 (go)
DMSO (77K)
g//
g﬩
A//
α2
2.187
2.199
2.060
182
2.208
2.069
177
2.188
2.057
176
2.202
2.411
2.188
2.058
179
2.056
179
2.078
184
-
118
0.755
0.781
0.981
0.590
0.741
0.780
0.793
0.980
0.618
0.765
0.781
0.813
1.000
0.635
0.819
0.748
-
0.999
0.833
0.840
0.833
0.840
-
-
-
-
-
0.757
0.827
1.000
0.626
0.761
β2
δ2
0.998
-
K//
K﬩
0.747

Table 5
The scavenging effect of the ligand HL and complexes 1 - 7 by DPPH method.
Scavenging effect (%)
Compound
IC50
(µM)
25 µM
50 µM
75 µM
100 µM
125 µM
250 µM
HL
1
2
8.26 0.45 22.56 0.78 25.97 0.21 30.48 0.46 37.42 0.30 85.97 0.81 157.55
10.00 0.86 28.87 1.06 88.54 0.85 93.49 1.16 95.38 0.87 97.54 0.24 58.87
10.56 1.20 11.11 0.53 11.94 0.32 15.57 0.21 24.34 1.14 50.17 0.65 249.95
3
4
0.12 1.00
2.52 0.78
5.52 0.96
3.02 0.89
6.10 1.10 10.83 0.70 16.84 1.18 39.85 0.65 >250
3.42 0.95 3.76 1.11 4.08 0.93 4.75 0.62 >250
5
9.39 1.09 13.53 0.84 18.21 0.30 24.17 0.47 30.07 0.78 46.18 0.23 >250
6
1.96 0.91 2.85 0.26 4.72 1.02 6.18 0.57 7.29 0.76 11.01 0.46 >250
7
13.36 0.69 31.58 0.92 49.45 0.76 58.40 0.38 64.88 0.46 68.35 0.70 75.62
9.57 1.39 11.48 1.05 16.22 1.09 18.30 0.90 24.38 0.46 47.86 0.34 >250
41.58 0.59 63.81 1.42 80.15 0.89 85.12 0.71 89.02 1.22 91.97 0.63 34.49
BHT
BHA