Nickel(II) complexes of N(4)-substituted thiosemicarbazones derived from pyridine-2-carbaldehyde: Crystal structures, spectral aspects and Hirshfeld surface analysis

Article abstract of DOI:10.1016/j.molstruc.2021.130362

Seven Ni(II) complexes {[NiL¹₂]·2H₂O (1), [Ni₂L²₂SO₄]·1?H₂O (2), [Ni(HL²)₂](NO₃)₂·H₂O·EtOH (3), [NiL²

Full text of DOI:10.1016/j.molstruc.2021.130362

Journal of Molecular Structure 1237 (2021) 130362
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstr
Nickel(II) complexes of N(4)-substituted thiosemicarbazones derived
from pyridine-2-carbaldehyde: Crystal structures, spectral aspects and
Hirshfeld surface analysis
a
a,∗
a,b,∗
, Hoong-Kun Func
P.F. Rapheal , E. Manoj , M.R. Prathapachandra Kurup
a
Department of Applied Chemistry, Cochin University of Science and Technology, Kochi, Kerala 682 022, India
Department of Chemistry, School of Physical Sciences, Central University of Kerala, Tejaswini Hills, Periye, Kasaragod, 671 320, India
X-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Seven Ni(II) complexes {[NiL12]·2H2O (1), [Ni2L22SO4]·1½H2O (2), [Ni(HL )2](NO3)2·H2O·EtOH (3),
2
Received 25 December 2020
Revised 20 March 2021
Accepted 22 March 2021
Available online 3 April 2021
2
2
2
3
3
[
NiL (HL )]OAc·3H2O (4), [Ni(HL )2](ClO4)2·2H2O (5), [NiL OAc]·2½H2O (6), [NiL NO3]·3H2O (7)} of
three thiosemicarbazone ligands, vizpyridine-2-carbaldehyde-N(4)-p-methoxyphenyl thiosemicarbazone
1
2
(
HL ), pyridine-2-carbaldehyde-N(4)-phenethyl thiosemicarbazone (HL ) and pyridine-2-carbaldehyde-
3
N(4)-pyridyl thiosemicarbazone [HL ] were synthesized and physico-chemically characterized by means
of partial elemental analyses, molar conductivity measurements, electronic, infrared spectral studies and
magnetic susceptibility measurements. In the complexes, the thiosemicarbazones coordinate both in the
thione form and in the deprotonated thiolate form. Pyridine nitrogen, azomethine nitrogen and thio-
late/thione sulfur are involved in coordination in all the complexes. The single crystal X-ray structures of
complexes 1a, 5 and [NiL32]·H2O (7a) are discussed, show octahedral coordination around Ni(II). Struc-
tural studies corroborate spectral characterization. Supramolecular interactions of the three complexes
are verified by Hirshfeld surface analyses, which reveal the dominant role of van der Waals forces (H···H
interactions) and confirm the reinforcement of π-π/C–H···π interactions in the crystal lattice packing of
these complexes.
Keywords:
Thiosemicarbazone
Ni(II) complex
Pyridine-2-carbaldehyde
Crystal structure
Hirshfeld surface analysis
©
2021 Elsevier B.V. All rights reserved.
1
. Introduction
ing a pyridine ring act as NNS tridentate systems. The ability to
exist as E and Z stereoisomers also make these systems versatile in
coordination [6]. Ni(II) thiosemicarbazone complexes have recently
been reported as efficient electrocatalyst [7] and photo-induced
molecular catalyst [8] for hydrogen production. Conversely the sub-
stituted derivatives of pyridine-2-carbaldehyde thiosemicarbazone
(HL) and their complexes with different metal ions have drawn
special attention due to their interaction with enzymes such as ri-
bonucleotide reductases, DNA polymerase and cell thiols [9]. Some
reports show that labile four-coordinated nickel(II) complexes with
tridentate thiosemicarbazone ligands exhibit antibacterial activi-
ties, whereas, six-coordinated nickel(II) complexes with thiosemi-
carbazone ligands show no activities against the test microorgan-
isms [10]. Based on the continuing interest of Ni(II) thiosemi-
carbazones, we report here seven new Ni(II) complexes of three
Thiosemicarbazones are considered as an important class of N,
S-donor ligands due to their structural diversity and variable donor
properties over a span of time [1]. The potentially beneficial bio-
logical effects such as antitumor, antibacterial, antiviral and anti-
malarial activities of thiosemicarbazones have added their chem-
istry very much interesting [2-4]. Introducing heterocyclic systems
have aroused considerable interest both in the coordination chem-
istry and in the biological activity of thiosemicarbazones. Chelation
of a thiosemicarbazone with a transition metal has become a tool
for enhancing their biological activity. They can coordinate as neu-
tral keto form or as anionic enolate form after deprotonation and
can adopt a variety of different coordination modes depending on
the substituents and metal ions [5]. Thiosemicarbazones contain-
different thiosemicarbazone ligands. The ligands include pyridine-
1
2
-carbaldehyde-N(4)-p-methoxyphenyl thiosemicarbazone (HL ),
pyridine-2-carbaldehyde-N(4)-phenethyl thiosemicarbazone (HL2)
and pyridine-2-carbaldehyde-N(4)-pyridyl thiosemicarbazone (HL3)
(Scheme 1). The ligands HL , HL2 and their copper(II), man-
∗
Corresponding authors.
1
E-mail addresses: manoje@cusat.ac.in (E. Manoj), mrp@cukerala.ac.in (M.R.P. Ku-
rup).
https://doi.org/10.1016/j.molstruc.2021.130362
0
022-2860/© 2021 Elsevier B.V. All rights reserved.

P.F. Rapheal, E. Manoj, M.R.P. Kurup et al.
Journal of Molecular Structure 1237 (2021) 130362
Scheme 1. The thiosemicarbazones HL , HL and HL3.
1
2
2.3.2. Synthesis of [Ni L2 SO ]·1½H O (2)
ganese(II) and cobalt(III) complexes have been reported earlier
11-13]. The spectral aspects of all the complexes are investigated
2
2
4
2
To a solution of the HL2 (1 mmol) in 25 ml hot boiling ethanol
[
and X-ray diffraction study of two of them are presented along
with crystal structure of an octahedral complex, derived from a
square planar complex on crystallization. Hirshfeld surface analy-
ses of three nickel(II) complexes of three different ligands are also
studied.
at 82 °C was added a solution of NiSO ·7H O (1 mmol) in a mix-
4
2
ture of ethanol (15 ml) and water (10 ml) and heated under re-
flux at 84 °C for four hours and the resulting solution was kept to
cool down naturally at room temperature overnight. The complex
formed was filtered, washed thoroughly with 5 ml each of water,
ethanol and ether and dried in vacuo over P O10.
4
2
. Experimental
2
2
2
.3.3. Syntheses of [Ni(L )(HL )](OAc)·3H O (4) and
2
3
[NiL (OAc)]·2½H O (6)
2
.1. Materials
2
To a solution of the respective ligand (1 mmol)) in 25 ml hot
boiling ethanol at 82 °C was added Ni(OAc) ·4H O (1 mmol) and
Pyridine-2-carbaldehyde (Aldrich), 2-phenylethylamine, p-
2
2
heated under reflux at 84 °C for two hours and the resulting
solution was kept to cool down naturally at room temperature
overnight. The complex formed was filtered, washed thoroughly
with 5 ml each of water, ethanol and ether and dried in vacuo over
anisidine and 2-aminopyridine (Fluka) were used as received.
-Methyl-4-phenyl-3-thiosemicarbazide was prepared as reported
4
previously [14]. Nickel(II) nitrate hexahydrate, nickel(II) sulphate
heptahydrate, nickel(II) acetate tetrahydrate, and nickel(II) perchlo-
rate hexahydrate (Merck) were used as supplied and solvents were
purified by standard procedures before use. Caution! Perchlorate
complexes of metals with organic ligands are potentially explosive
and should be handled with care.
P4O10.
2
2.3.4. Synthesis of [Ni(HL )2](ClO4)2·2H2O (5)
To a solution of the HL2 (1 mmol) 25 ml hot boiling ethanol
at 82 °C was added Ni(ClO ) ·6H O (1 mmol) and heated at re-
4
2
2
flux for one hour and the resulting solution was kept to cool down
naturally at room temperature overnight. The complex formed was
filtered, washed thoroughly with 5 ml each of water, ethanol and
2
.2. Syntheses and characterization of thiosemicarbazones
The syntheses of HL1 and HL2 and crystal structure of HL2 have
ether and dried in vacuo over P O10.
4
been reported earlier [13,15].
3. Physical measurements
2
.2.1. Synthesis of HL3
To a solution of 1.00 g (5. 52 mmol) of 4-methyl-4-phenyl-3-
Elemental analyses of the thiosemicarbazones and the com-
thiosemicarbazide in MeCN (5 ml), was added 0.520 g (5.52 mmol)
of 2-aminopyridine and 0.591 (5.52 mmol) of pyridine-2-
plexes were done on a Heracus elemental analyzer at CDRI, Luc-
know, India and on a Vario EL III CHNS analyzer at SAIF, Kochi,
India. The IR spectra were recorded on a Thermo Nicolet AVATAR
g
carbaldehyde and heated at reflux for 1.5 h. The solution was
chilled (overnight) by keeping in a refrigerator and the compound
formed was collected by filtration through quantitative filter paper,
washed well with MeCN (10 ml) and recrystallized from ethanol
370 DTGS model FT-IR spectrophotometer with KBr pellets at SAIF,
Kochi. The far IR spectra were recorded using polyethylene pel-
−1
lets in the 500–100 cm
region on a Nicolet Magna 550 FTIR
(
80 ml). It was then dried in vacuo over P O10. Yield 52%, M.P.
4
instrument at the Regional Sophisticated Instrument Facility, In-
dian Institute of Technology, Bombay, India. Electronic spectra were
recorded on a Cary 5000, version 1.09 UV-Vis-NIR spectrophotome-
ter from a solution in CHCl3 at DAC, CUSAT, Kochi. The magnetic
susceptibility measurements were carried out at the Indian Insti-
tute of Technology, Roorkee, India, at room temperature in the
polycrystalline state on a PAR model 155 Vibrating Sample Mag-
netometer at 5 kOe field strength. The molar conductivities of the
1
76–177 °C. Elemental Anal. Found (Calc.): C, 55.72 (56.01); H, 4.40
4.31); N, 27.75 (27.22); S, 12.18 (12.46)%.
(
2
2
.3. Syntheses of complexes
.3.1. Syntheses of [NiL1 ]·2H O (1), [Ni(HL ) ](NO ) ·H O·EtOH (3),
2
2
2
2
3
2
2
3
[NiL NO ]·3H O (7)
3
2
complexes in dimethylformamide solutions (10 3 M) at room tem-
−
To a solution of the respective ligand (1 mmol) in 25 ml hot
boiling ethanol at 82 °C was added Ni(NO ) ·6H O (1 mmol) and
perature were measured using a direct reading conductivity meter.
3
2
2
heated under reflux at 84 °C for two hours and the resulting
solution was kept to cool down naturally at room temperature
overnight. The complexes formed were filtered, washed thoroughly
with 5 ml each of water, ethanol and ether and dried in vacuo over
4. X-Ray crystallography
Single crystals of compounds [NiL1 ]·DMF (1a) and
2
2
P4O10
.
[Ni(HL ) ](ClO ) ·2H O (5) of X-ray diffraction quality were
2
4
2
2
2

P.F. Rapheal, E. Manoj, M.R.P. Kurup et al.
Journal of Molecular Structure 1237 (2021) 130362
Table 1
Crystal refinement parameters of the complexes 1a, 5& 7a.
[NiL12]·DMF (1a)
[Ni(HL )2](ClO4)2·2H2O (5)
2
[NiL32]·H2O (7a)
Parameters
Empirical Formula
Formula weight (M)
C31H33N9NiO3S2
702.49
C30H36Cl2N8NiO10S2
862.38
C24H20N10Ni1O1S2
587.31
Temperature (T) K
293(2)
100.0(1)
150(2)
Wavelength (Mo Kα) ( A˚ )
0.71073
0.71073
0.71073
Crystal system
Space group
Triclinic
P1¯
Orthorhombic
Fddd
Monoclinic
I 2/a
Lattice constants
a ( A˚ )
b ( A˚ )
c ( A˚ )
10.2850(14)
10.6120(10)
16.3600(11)
108.467(6)
93.263(8)
102.453(9)
1638.6(3)
2
10.6424(4)
44.668(3)
31.2715(15)
90.00
12.7091(6)
9.2346(4)
21.2265(8)
90.00
α (°)
β (°)
γ (°)
90.00
94.311(4)
90.00
90.00
Volume V ( A˚ 3
)
14,865.7(13)
16
2484.17(18)
4
Z
Calculated density (ρ) (Mg
1.424
1.541
1.570
−
3)
m
Absorption coefficient, μ
0.767
0.844
0.990
mm 1
−
)
(
F(000)
732
7136
1208
Crystal size (mm)
Limiting Indices
0.25 × 0.20 × 0.15
−12≤h ≤ 0,
0.78 × 0.28 × 0.19
−10≤h ≤ 12,
0.23 × 0.18 × 0.13
−15≤h ≤ 15,
−10≤k ≤ 10,
−25≤l ≤ 24
11,503
−
−
12≤k ≤ 12,
19≤l<≤19
−52≤k ≤ 52,
−37≤l ≤ 37
Reflections collected
6106
4259
Independent Reflections
Refinement method
5768 [R(int) = 0.0444]
Full-matrix least-squares on F
5768 / 162 / 469
4259 [R(int) = 0.0425]
Full-matrix least-squares on F
4259/ 5 / 272
2187[R(int) = 0.0531]
2
2
2
Full-matrix least-squares on F
Data / restraints / parameters
Goodness-of-fit on F2
Final R indices [I > 2σ (I)]
R indices (all data)
2187/1/173
0.998
1.055
1.099
R1 =0.0550, wR2 = 0.1010
R1 = 0.1862, wR2 =0.1284
0.304 and −0.395
R1 = 0.0238, wR2 = 0.0448
R1 = 0.0239, wR2 = 0.0449
0.687 and −0.609
R1 = 0.0466, wR2 = 0.1089
R1 = 0.0618, wR2 = 0.1179
0.681 and –0.896
Largest difference peak
and hole (e A˚ 3
−
)
R1 = ꢀ||Fo| - |Fc|| / ꢀ|Fo|
.
2
2
)
/ ꢀw(Fo ) ]1/2.
2
2 2
wR2 = [ꢀw(Fo -Fc
Table 2
Magnetic susceptibilities, molar conductivities and partial elemental analyses of the complexes.
∗
Complex
μ(B.M)
λ
M
Found (Calc.)%
C
H
N
S
[
[
[
[
[
[
[
NiL12]·2H2O (1)
2.88
Dia.
2.89
2.86
3.09
Dia.
Dia.
5
51.13(50.54)
45.05(44.64)
47.53(47.13)
52.35(51.97)
41.71(41.78)
40.34(40.12)
34.04(33.44)
4.46(4.54)
4.68(4.12)
4.43(4.94)
5.07(5.45)
4.07(4.21)
4.52(4.33)
4.19(3.74)
16.50(16.84)
14.12(13.88)
17.66(17.17)
15.46(15.15)
12.94(12.99)
16.48(16.71)
19.17(19.50)
9.58(9.64)
11.49(11.92)
8.43(7.86)
8.19(8.67)
7.56(7.44)
7.74(7.65)
7.52(7.44)
2
Ni2L 2SO4]·1½H2O (2)
19
160
85
136
2
2
Ni(HL )2](NO3)2·H2O·EtOH (3)
2
2
NiL (HL )]OAc·3H2O (4)
2
Ni(HL )2](ClO4)2·2H2O (5)
3
NiL OAc]·2½H2O (6)
3
NiL NO3]·3H2O (7)
20
∗
Molar conductivity of 10 M DMF solution, in ohm cm2 mol−1
−3
−1
.
grown from their DMF and methanol solutions respectively, by
slow evaporation at room temperature in air. Single crystals of
isotropically. Nitrogen bound hydrogen atoms were located from
˚
Fourier maps and N–H distances were restrained to 88± 0.01 A.
the complex [NiL32]·H O (7a) were obtained by slow evapora-
Hydrogens bound to oxygen of water molecule in 7a could not
be located and were ignored in the final stage of refinement.
DMF molecule is disordered over two sites with occupancies of
0.578(11) and 0.422(11) for major and minor disordered parts
respectively. Perchlorate ions in 5 are disordered over two sites
with occupancies of 0.5424(7) and 0.4576(7) for major and minor
disordered parts respectively. Molecular graphics employed were
ORTEP-III [17], PLATON [18] and Mercury [19].
2
tion of a solution of complex 7 in methanol water mixture. The
crystallographic data and structure refinement parameters of all
the complexes are given in Table 1. The data collection and cell
refinement of 1a were carried out using a ARGUS-MACH3 (Nonius,
˚
1
997) with graphite monochromated Mo Kα (λ = 0.71073 A)
radiation at the National Single Crystal X-Ray Diffraction Facility,
IIT, Bombay, India while OXFORD DIFFRACTION XCALIBUR-S was
used for 7a. A single crystal of compound 5 is diffracted by a
Bruker Smart Apex2 CCD area detector diffractometer equipped
5. Results and discussion
˚
with graphite monochromated Mo Kα (λ = 0.71073 A) radia-
tion, at the School of Physics, Universiti Sains Malaysia, Penang,
Malaysia. The trial structures were solved using SHELXS-97
Compositions and empirical formulae of the seven Ni(II) com-
plexes were determined by using elemental analyses. Molar con-
ductivity measurements, UV-Vis absorption spectra, FT-IR spectra
and magnetic susceptibility measurements were also done. The
stoichiometries of the complexes with partial elemental analyses,
molar conductivity and magnetic susceptibility of the complexes
[
16] and refinements were carried out by full-matrix least squares
on F2 (SHELXL-2018/1) [16]. All non-hydrogen atoms were refined
anisotropically, and all hydrogen atoms on carbon were placed
in calculated positions, guided by difference maps and refined
3

P.F. Rapheal, E. Manoj, M.R.P. Kurup et al.
Journal of Molecular Structure 1237 (2021) 130362
Fig. 1. ORTEP diagram of the complex 1a in 50% probability ellipsoids. All hydrogen atoms and DMF are omitted for clarity.
Fig. 2. ORTEP diagram of the complex 5 in 50% probability ellipsoids. All hydrogen atoms, water molecules and anions are omitted for clarity.
5.1. Crystal structures of [NiL1 ]·DMF (1a), [Ni(HL ) ](ClO ) ·2H O
2
are presented in Table 2. Molar conductivity measurements show
that complexes 1, 2, 6, and 7 are non-electrolytes and the remain-
ing are cationic complexes, behaving either as 1:1 ( 4) or 2:1 (5)
2
2
4
2
2
(5) & [NiL3 ]·H O (7a)
2
2
electrolytes in 10 3 M DMF solution. The complexes 2, 6 and 7
are diamagnetic indicating probable square planar geometry for a
normal spin free d8 system. Complexes 1, 3, 4 and 5 are paramag-
netic with μeff/= 2.85 - 3.09 BM. In the compounds 1, 2, 6 and 7,
the thiosemicarbazones deprotonate and chelate in thiolate form.
In complexes 3 and 5 the thiosemicarbazones are in the thione
form, whereas in 4 both the thione and the deprotonated thiolate
forms of the ligand are coordinated, in agreement with IR spectral
study.
−
The Ni(II) centers in all the three complexes adopt octahe-
dral geometry by the coordination of the mono deprotonated form
of the respective ligands, HL1 in [NiL1 ]·DMF (1a) and HL in
3
2
[NiL3 ]·H O (7a), but by the coordination of the neutral ligand HL
2
2
2
2
in [Ni(HL ) ](ClO ) ·2H O (5). The molecular structures of 1a, 5
2
4
2
2
and 7a along with atom numbering schemes are given in Figs. 1-
3. The Ni(II) ion in complexes 1a and 7a are coordinated in a
meridional fashion [20,21] using pairs of cis pyridyl nitrogen, trans
azomethine nitrogen and cis thiolate sulfur atoms by two monoan-
4

P.F. Rapheal, E. Manoj, M.R.P. Kurup et al.
Journal of Molecular Structure 1237 (2021) 130362
Fig. 3. ORTEP diagram of the complex 7a in 50% probability ellipsoids. All hydrogen atoms and water molecule are omitted for clarity.
ionic ligands. In complex 5, two molecules of the neutral ligand
HL2 are coordinated in the meridional fashion [20] using pairs of cis
pyridyl nitrogen, trans azomethine nitrogen and cis thione sulfur
atoms. Heterocyclic thiosemicarbazones show a strong tendency
for this meridional coordination and is seen in most of their octa-
hedral metal complexes, resulting in two bicyclic chelate systems.
In complex 1a, the bicyclic chelate systems Ni1, S1, C7, N3, N2, C6,
C5, N1 and Ni1, S2, C21, N7, N6, C20, C19, N5 are approximately
Table 3
Selected bond lengths ( A˚ ) and bond angles (°) of HL , [NiL12] DMF (1a),
2
2
3
[
Ni(HL )2](ClO4)2·2H2O (5) and [NiL 2]·H2O (7a).
∗
HL2
1a
5
7a
S1–C7
1.6849(13)
1.2837(15)
1.3783(14)
1.3587(16)
1.3401(16)
1.707(5)
1.733(5)
1.289(5)
1.275(6)
1.367(5)
1.367(5)
1.332(6)
1.322(6)
1.375(6)
1.360(6)
2.3899(15)
2.4028(15)
2.101(4)
2.107(4)
2.028(4)
2.021(5)
118.6(4)
110.8(4)
117.1(5)
127.7(4)
115.1(4)
90.08(15)
1.6982(11)
1.724(3)
S2–C21
N2–C6
1.2877(15)
1.3628(13)
1.3578(15)
1.3320(15)
2.4416(3)
2.0927(10)
2.0357(9)
1.287(5)
1.378(4)
1.321(4)
1.375(5)
2.3996(10)
2.117(3)
2.020(3)
˚
planar as evidenced by the maximum deviation of 0.0618(16) A
N6–C20
˚
for S1 and 0.055(4) A for N5 respectively. Half of the complex
N2– N3
N6–N7
molecules of 5 and 7a were generated by symmetry. The bicyclic
chelate system Ni1, S1, C7, N3, N2, C6, C5, N1 in complex 5 is ap-
N3–C7
N7–C21
˚
proximately planar with a maximum deviation of −0.0546(9) A for
N4–C7
N1, while the same system in complex 7a is also planar with max-
N8–C21
˚
imum deviation of 0.087(3) A for N1. The dihedral angle formed
Ni1–S1
Ni1–S2
by the mean planes of the bicyclic chelate systems of each of the
ligands is 86.28(12)˚ in 1, 84.56(3)˚ in 5 and 87.64(8) ˚ in 7a. The
bond lengths Ni–Nazomethine, Ni–Npy, and Ni–S in all the complexes
increases in that order as in similar compounds [19-22]. In com-
pound 1, the trans angles N1–Ni1–S1, N5–Ni1–S2 and N2–Ni1–N6
are 159.08(12), 158.87(12) and 173.06(16)˚ respectively, while these
angles N1–Ni1–S1 and N2–Ni1–N2a are 158.77(3) and 174.93(5)˚ in
complex 5 and 158.51(8) and 179.02(16)˚ in complex 7a respec-
tively. These factors suggest considerable distortion from an oc-
tahedral geometry around Ni(II) center in all the complexes, but
Ni1–N1
Ni1–N5
Ni1–N2
Ni1–N6
C6–N2–N3
N2–N3–C7
N4–C7–N3
N3–C7–S1
N4–C7–S1
N1–Ni1–N5
N1–Ni1–N1a
N2–Ni1–N6
N2–Ni1–N2a
S1–Ni1–S2
S1–Ni1–S1a
S1–Ni1–N1
S1–Ni1–N5
S1–Ni1–N2
S1–Ni1–N2a
S1–Ni1–N6
N1–Ni1–N2
N1–Ni1–N2a
N1–Ni1–N6
N1–Ni1–S2
N1–Ni1–S1a
N2–Ni1–N5
N2–Ni1–S2
S2–Ni1–N5
S2–Ni1–N6
N5–Ni1–N6
114.37(10)
120.47(10)
116.16(10)
119.25(8)
124.59(9)
120.93(10)
119.41(9)
115.12(10)
121.75(9)
123.2(7)
117.9(3)
112.0(3)
118.0(3)
126.6(3)
115.4(3)
93.66(5)
86.61(16)
173.06(16)
96.37(6)
lesser in complex 7a.
174.93(5)
179.02(16)
In compound 5, the ligand HL2 undergoes structural reorienta-
tion to coordinate to the metal in an NNS manner. The azome-
thine nitrogen, was in E configuration with both pyridyl nitrogen
and thione sulfur atoms in its metal free form of ligand [15], is
now in Z form with pyridine nitrogen and sulfur atoms. The C–
95.615(15)
158.78(3)
96.19(5)
159.08(12)
92.02(11)
80.41(12)
158.51(8)
81.29(3)
80.47(8)
102.17(3)
100.20(8)
˚
S bond length increases slightly by 0.0133(13) A and the N3–C7
105.10(11)
78.68(16)
bond length remains almost same on coordination, in agreement
77.48(4)
98.99(4)
78.64(11)
100.63(11)
with the coordination via thione form of the ligand. In complex 1a,
95.71(16)
88.95(11)
˚
˚
the C–S {1.707(5) A for C7–S1 and 1.733(5) A for C21–S2} and C–N
˚ ˚
1.332(6) A for N3–C7 and 1.322(6) A for C21–N7} bond lengths are
{
89.25(3)
92.39(8)
consistent with partial single and double bond character confirm-
ing the coordination via thiolate sulfur after deprotonation. Simi-
lar bonding in complex 7a is also evidenced by the C–S {1.724(3)
97.18(16)
103.31(12)
158.87(12)
80.49(13)
78.60(17)
˚
˚
A for C7–S1} and C–N {1.321(4) A for N3–C7} bond lengths. The
Ni–Nazomethine bond lengths are less compared to Ni–Npyridine, in-
dicating the higher strength of former bond than the latter in all
∗
Ref [15].
5

P.F. Rapheal, E. Manoj, M.R.P. Kurup et al.
Journal of Molecular Structure 1237 (2021) 130362
Fig. 4. A view of the packing of molecules of 1a along the c axis showing hydrogen bonding interactions.
Fig. 5. A view of the unit cell packing of the molecule 5 along the a axis showing ABABAB… packing along the c axis.
6

P.F. Rapheal, E. Manoj, M.R.P. Kurup et al.
Journal of Molecular Structure 1237 (2021) 130362
Table 4
Interaction parameters of [NiL12]·DMF (1a).
π-π interactions
Cg(I)···Cg(J)
Cg(5) Cg(7)a
Cg(6) Cg(8)b
Cg···Cg ( A˚ )
α (°)
β (°)
24.3
27.6
21.7
24.5
3.671(3)
3.711(3)
3.670(3)
3.711(3)
3.8(3)
3.3(3)
3.8(3)
3.3(3)
c
Cg(7)· Cg(5)
b
Cg(8) ·Cg(6)
C–H···π interactions
C–H···Cg(J)
H—Cg ( A˚ )
C—Cg ( A˚ )
C–H···Cg (°)
102
d
C1–H1···Cg(2)
2.92
2.99
3.00
3.244(7)
3.323(6)
3.814(6)
d
C15–H15· Cg(1)
103
e
C23–H23· Cg(1)
147
Cg(1)= Ni1, S1, C7, N3, N2; Cg(2)= Ni1, S2, C21, N7, N6; Cg(5)= N1, C1, C2, C3, C4, C5; Cg(6)= N5, C15, C16, C17, C18, C19; Cg(7)= C8, C9, C10, C11, C12, C13;
Cg(8)= C22, C23, C24, C25, C26, C27, α (°) = Dihedral angle between planes I and J@β (°) = Angle between Cg(I)–Cg(J) vector and Cg(J) perp
Hydrogen bonding interactions
D–H ·A
D–H ( A˚ )
H–A ( A˚ )
D–A ( A˚ )
D–H ·A (°)
155(4)
162(4)
151(4)
156
f
N4–H4’···O3
0.88(3)
0.88(3)
0.88(3)
0.93
2.07(4)
2.20(4)
2.58(4)
2.55
2.889(16)
3.042(19)
3.371(6)
3.416(8)
3.269(7)
2.893(7)
3.185(14)
3.692(5)
2.866(6)
f
N4–H4’···O3A
e
N8–H8···S2
g
C3–H3···O2
h
C4–H4···O1
0.93
2.60
129
C9–H9···N3
0.93
2.29
122
f
C13–H13···O3
0.93
2.40
142
b
C20–H20···S1
C27–H27···N7
0.93
2.82
156
0.93
2.26
122
D = donor, A = acceptor, Equivalent position codes a= -x, 1+y, z; b = -x, -y, -z; c = x, -1+y, z; d = x. y, z; e = 1-x, -y, -z; f = -1+x,-1+y,z; g = 1-x,1-y,-z, h= 1-x, -y, -z
Table 5
2
Interaction parameters of [Ni(HL )2](ClO4)2·2H2O (5).
C–H···π interactions
C–H···Cg(J)
H···Cg ( A˚ )
C–Cg (Ǻ)
3.2744(13)
C–H···Cg (°)
102
a
C1–H1···Cg(1)
C1–H1···Cg(3)
2.95
2.95
b
3.2744(13)
102
Cg(1) = Ni1, S1, C7, N3, N2; Cg(3)= Ni1, S1a, C7a, N3a, N2a.
Hydrogen bonding interactions
D–H···A
D–H ( A˚ )
H···A ( A˚ )
D–A ( A˚ )
D–H···A (°)
126.4(12)
146.6(14)
159.3(14)
157.1(13)
134.8(13)
165
b
O1S–H1A···N3
0.837(13)
0.845(14)
0.872(9)
0.932(9)
0.932(9)
0.93
2.204(14)
2.086(14)
1.950(10)
2.292(10)
2.171(13)
2.46
2.7827(13)
2.830(2)
b
O1S–H1B···O3A
b
N3–H3’···O1S
2.7827(13)
3.171(2)
b
N4–H4’···O3B
b
N4–H4’···O4A
2.903(6)
c
C2–H2···.O2B
3.371(3)
d
C3–H3···O2B
0.93
2.52
3.239(3)
134
C8–H8A···S1
0.97
2.76
3.1091(15)
102
D = donor, A = acceptor, Equivalent position codes a = ¾-x, -1/4-y, z; b = x, y, z; c = 1-x, -1/4+z, - 1/4+-z; d = 3/4+x,-y, -1/4+z.
the complexes. The Ni–S bond length in complex 5 is higher com-
pared to that in 1 and 7a, is in agreement with thione coordination
Table 3).
In complex 1a, the molecules are connected by various hydro-
5.2. Infrared spectra
(
The IR spectral bands are found helpful to decide the coordina-
tion modes, which are listed in Tables 7 and 8. In the IR spectra of
complexes 3 and 5, bands at 3204 and 3234 cm 1 regions are due
to the stretching frequency for 2NH. Besides, no band due to the
SH group is observed between 2600 and 2500 cm 1 in agreement
with the thione form of the ligand in these complexes [23]. In the
−
gen bonding interactions (Fig. 4) and are packed in the lattice in
a ‘face to face’ arrangement along the a axis. The crystal structure
cohesion is reinforced by making use of π-π and C–H···π ring in-
teractions. Relevant hydrogen bonding, C–H···π and π-π ring in-
teractions of the complex 1a are given in Table 4.
−
4
spectra of the complexes 1, 2, 6 and 7, ν( NH) vibrations appear
in the range 3312–3440 cm 1, but there is no band correspond-
ing to stretching of the hydrazine NH, consistent with deprotona-
tion of the ligands in these complexes. The shift of the thiocarbonyl
stretching and bending modes to lower frequencies in all the com-
plexes is in accordance with the coordination through sulfur. The
ν(Ni–S) bands in the 325 – 375 cm 1 regions further confirm the
sulfur coordination [23]. A similar shift of ν(C=N) frequencies cor-
roborate coordination of the azomethine nitrogen [20]. Additional
evidence for coordination of the imine nitrogen is the presence of
−
The molecules of 5 are packed in a ‘face to face’ ABABAB…
manner along the c axis within the unit cell (Fig. 5), as a result of
diverse hydrogen bonding and C–H…π ring interactions (Table 5).
The ‘face to face’ ABABAB…manner packing is seen in the crystal
lattice of complex 7a also, but is along the b axis (Fig. 6). Various
hydrogen bonding and π···π ring interactions of complex 7a are
given in Table 6. In the crystal packing of complex 5, no signifi-
cant π-π interactions are observed, while the lattice cohesion of
complex 7a lacks relevant C–H···π interactions.
−
7

P.F. Rapheal, E. Manoj, M.R.P. Kurup et al.
Journal of Molecular Structure 1237 (2021) 130362
Table 6
Interaction parameters of [NiL32]·H2O (7a).
π—-π interactions
Cg(I)···Cg(J)
Cg-Cg( A˚ )
α °
18.43(18)
18.43(18)
β °
20.1
37.7
a
Cg(5)···Cg(6)
3.903(2)
3.903(2)
b
Cg(6)···Cg(5)
Cg(5)= N1, C1, C2, C3, C4, C5; Cg(6)= N5, C8, C9, C10, C11, C12, α (°) = Dihedral angle between planes I and J, β (°) = Angle
between Cg(I)–Cg(J) vector and Cg(J) perp
Hydrogen bonding interactions
D–H···A
D–H ( A˚ )
H···A ( A˚ )
D–A ( A˚ )
D–H···A (°)
175(3)
171
c
N4–H4N···N5
0.87(4)
0.95
2.43(4)
2.49
3.299(4)
3.429(4)
3.628(4)
2.852(4)
3.623(4)
3.602(4)
C4–H4···O111
d
C6–H6···S1
0.95
2.73
157
C9–H9···N3
0.95
2.25
120
b
C9–H9···S1
0.95
2.84
140
c
C12–H12···S1
0.95
2.77
146
D = donor, A = acceptor, Equivalent position codes a= -1/2+x, -y, z; b = ½+x, -y, z; c = 3/2-x, -1/2-y, -1/2-z; d = 1-x, -y, -z.
Fig. 6. A view of the unit cell packing of the molecule 7a along the a axis showing different hydrogen bonding interactions.
−
1
−1
The sulfato complex 2 exhibits a medium band at 977 cm due
ν(Ni–N) bands in the 417-/430 cm range [23,24]. A second band
due to ν(C=N) is resolved in the spectra of 1, 2, 4, 6 and 7 at ca.
−
−1
1
to ν , a medium band at 451 cm due to ν , medium and weak
1
2
−1
1
600 cm . Coordination of the pyridine nitrogen atom is clearly
bands at 1185, 1118 and 1023 cm corresponding to ν , and weak
3
band at 609 cm 1 due to ν , which are assigned to the coordina-
−
shown by the shift to higher frequencies of the deformation mode
4
−1
bands that appear in the ranges 613–622 and 401 - 412 cm
the spectra of HL , HL and HL3 [25]. The ν(M–N) bands for the
pyridyl nitrogen are assigned in the 211–272 cm region, confirm
the coordination of pyridine nitrogen.
in
tion of bidentate sulfate group [26].
1
2
In the spectrum of the complex 3, the absence of the combi-
−1
−1
nation bands (ν1 ν4) in the region 1700–1800 cm
rules out
+
8

P.F. Rapheal, E. Manoj, M.R.P. Kurup et al.
Journal of Molecular Structure 1237 (2021) 130362
Table 7
Infrared spectral data (cm 1) of the ligands and their complexes.
−
2
4
Compound
HL1
ν(C = N)
ν(N = C)
ν(N–N)
ν/δ(C-S)
py(ip)
py(op)
ν( N-H)
ν( N-H)
1584
1566
1586
1534
1575
1576
1570
1593
1537
1568
1024
1133
1079
1143
1156
1135
1143
1078
1126
1159
1334,837
1300,829
1324,897
1338.894
1302,886
1310,891
1310,886
1298,929
1277,903
1260,897
613
646
622
670
637
637
637
614
641
640
401
409
406
438
425
417
425
412
421
416
3134
—
3310
3440
3374
3312
3428
3419
3424
3310
3411
3416
[
NiL12]·2H2O (1)
1608
HL2
3129
—
[
[
[
[
Ni2L22SO4]·1½H2O (2)
1624
—
2
Ni(HL )2](NO3)2·H2O·EtOH (3)
3234
—
2
2
NiL (HL )]OAc·3H2O (4)
1600
—
2
Ni(HL )2](ClO4)2·2H2O (5)
3204
3057
—
3
HL
3
[
[
NiL OAc]·2½H2O (6)
1612
1608
3
NiL NO3]·3H2O (7)
—
Table 8
Metal-ligand stretching frequencies (cm 1) of the complexes.
the monocoordinated nitrato group, are observed at 1713 and 1738
−
−1
cm
.
Complexes
νNi–Nazo.
νNi–Npy
νNi–S
The spectrum of the acetate-containing complex 4 displays rel-
−
1
NiL12]·2H2O (1)
atively strong bands at 1559 due to νa(COO) and 1417 cm
due
[
[
[
[
[
[
[
417
425
430
412
427
428
427
245
228
248
271
211
220
225
372
358
375
325
371
345
355
Ni2L22SO4]·1½H2O (2)
to ν (COO) indicating the ionic nature of the acetate in this com-
s
2
Ni(HL )2](NO3)2·H2O·EtOH (3)
pound [28]. In complex 6 strong bands observed at 1570 and 1400
2
2
NiL (HL )]OAc·3H2O (4)
−1
cm
are assigned to νa(COO) and νs(COO), which support the
2
Ni(HL )2](ClO4)2·2H2O (5)
unidentate nature of acetate group [28].
3
NiL OAc]·2½H2O (6)
3
The perchlorate complex 5 shows single broad band at 1122
NiL NO3]·3H2O (7)
cm 1 and strong bands at 637 and 624 cm , indicating the pres-
−
−1
ence of ionic perchlorate. The bands at 1122 cm 1 are assignable
−
−
1
to ν (ClO ) and, a medium band at 915 cm may be assigned to
3
4
the possibility for coordinated nitrato group. The bands at ca. 830
ν (ClO ) of the perchlorate ion [11].
1
4
cm 1 (ν ), 1380 cm
−
−1
(ν ) and 700 cm (ν ) clearly point out
−1
2
3
4
the uncoordinated nature of the nitrato group [12].
The nitrato complex 7 has two strong bands at 1260 and 1383
5.3. Electronic spectra
cm 1 with a separation of 123 cm
−
−1
corresponding to ν1 and ν4
indicating the presence of a terminal monodentate nitrato group
27]. The ν +ν4 combination bands, considered as diagnostic for
The high-energy π→π∗ transitions ca. 42,000 cm are not sig-
−1
[
nificantly altered on complex formation. The n→π∗ transitions as-
1
Fig. 7. dnorm surface view, shape index and curvedness of complex a) [NiL12]·DMF (1a), b) [Ni(HL )2] (ClO4)2·2H2O (5) and c) [NiL 2] ·H2O(7a).
2
3
9

P.F. Rapheal, E. Manoj, M.R.P. Kurup et al.
Journal of Molecular Structure 1237 (2021) 130362
Fig. 8. 2D finger print plots of complex a) [NiL12] (1), b) [Ni(HL )2] (5) and c) [NiL32] (7a) showing the percentage of contacts contributed to the total Hirshfeld surface area.
2
Table 9
Diamagnetism in Ni(II) complexes is a consequence of eight
Electronic spectral data (cm 1) of the ligands and their complexes.
−
electrons being paired in the four low-lying d orbitals, the upper
orbital being dx2-y . The four lower orbitals are often so close in
energy that individual transitions from them to the upper d level
cannot be distinguished resulting in a single absorption band. The
Compound
π→π∗
n→π∗
C T
—
d -d
2
HL1
42,730,38,760
41,800,37,880
42,190,36,630
42,200,38,310
30,770
—
NiL12]·2H2O (1)
[
32,360 22,620 11,590
30,960
HL2
—
—
−1
very weak band at ca. 19,000 cm
corresponds to the d-d bands
[
[
[
[
Ni2L22SO4]·1½H2O (2)
33,010 22,320 17,010
32,220 22,570 11,860
33,110 22,108 18,910
33,070 22,420 18,180
−1
of the complexes 2, 6 and 7. A weak shoulder at ca.23000 cm is
2
Ni(HL )2](NO3)2·H2O·EtOH (3) 42,120,38,610
assigned to charge transfer transition.
2
2
NiL (HL )]OAc·3H2O (4)
41,600,37,910
42,300,37,740
41,840,35,840
42,200,35,910
41,900,38,020
2
Ni(HL )2](ClO4)2·2H2O (5)
3
HL
29,500
—
—
—
—
3
[
[
NiL OAc]·2½H2O (6)
32,100 22,230
32,210 22,070
.4. Hirshfeld surface analysis of [NiL1 ]·DMF (1a),
5
3
2
NiL NO3]·3H2O (7)
2
3
[
Ni(HL ) ](ClO ) ·2H O (5) & [NiL ]·H O (7a)
2
4
2
2
2
2
The Hirshfeld surface analyses of the complexes 1a, 5 and 7a
were performed using the program Crystal Explorer 17.5 [30]. The
Hirshfeld dnorm, shape index and curvedness surfaces of all com-
plexes were mapped (Fig. 7). The two-dimensional decomposed
fingerprint plots were also plotted (Fig. 8) to understand and con-
firm the supramolecular interactions quantitatively [31,32].
sociated with the azomethine functions of the thiosemicarbazone
moieties are shifted to higher energy for the complexes [29].
The ground state of Ni(II) in an octahedral coordination is
3A2g. Electronic spectral bands of hexacoordinate compounds of
nickel(II) can be assigned to the three spin allowed transitions
3T2g(F) ← 3A2g(F) (ν1), 3T1g(F) ← A (F) (ν ) and 3T1g(P) ←
The hydrogen bonding interactions are evidenced by intense red
coloured spots on the Hirshfeld surface mapped with dnorm func-
tions. A number of small red spots is also visible indicating short
H···H contacts, which is clearer on dnorm surfaces of the complexes
1 and 7a. Presence of blue triangles (bow-tie pattern) in the shape
index surface and the flat surfaces on the aromatic rings in the
curvedness indicate the presence of π-π stacking interactions in
the lattice, which are more and clear in the complexes 1a and 7a.
The red regions of the Hirshfeld surface mapped over shape index
properties of complexes 1 and 5 are indicating the C–H···π interac-
tions in their crystal lattices. These measures of curvature provide
clear insight on molecular packing in the crystal.
3
2g
2
3A2g(F) (ν ) in the increasing order of energy with molar absorp-
3
tivity generally below 20. The ν3 band is often masked by the
high-intensity charge transfer bands [20]. The energy of the ν1 is
equal to 10 Dq. It is found that the spectra of the octahedral com-
plexes 1, 3, 4 and 5 do not resolve to get all the three bands pos-
sible. Table 9 shows the band maxima of electronic transitions for
the ligands and their complexes in chloroform solutions. The bands
−1
at ca.12000 cm are assigned to ν1 and the bands at ca.17000 –
1
9,000 cm 1 are assigned to ν2. But ν3 is presumably obscured by
−
−1
the weak charge transfer bands at ca.23000 cm [29].
10

P.F. Rapheal, E. Manoj, M.R.P. Kurup et al.
Journal of Molecular Structure 1237 (2021) 130362
Table 10
Attributes of Hirshfeld surfaces of the Ni(II) thiosemicarbazone complexes.
Volume ( A˚ 3
˚ 2
Complex
)
Area (A )
Globularity (G)
Asphericity (ꢁ)
[
[
[
NiL12]·DMF (1a)
690.67
708.01
590.82
592.45
608.69
517.28
0.638
0.631
0.658
0.275
0.090
0.124
2
Ni(HL )2](ClO4)2·2H2O (5)
3
NiL 2] ·H2O (7a)
The 2D fingerprint plots clearly analyze and display the vari-
ous intermolecular interactions in the crystal lattices. The H···H in-
teractions (van der Waals forces) are observed as the most domi-
nant forces in all the complexes and are found in the middle of the
scattered point of the 2D fingerprint plots. The percentage of H···H
contacts contributed to the total Hirshfeld surface area is 46.1, 37.2
and 37.4% for the complexes 1a, 5 and 7a respectively. The rela-
tive contribution of other significant interactions observed for the
complex 1a are C···H (21.4%), S···H (9.9%), O···H (9.3%), N···H (6.8%)
and C···C (4.7%); while that of complex 5 are O···H (23.3%), C···H
Supplementary materials
Supplementary material associated with this article can be
found, in the online version, at doi:10.1016/j.molstruc.2021.130362.
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Comparison of the Hirshfeld volume and surface area of the co-
ordination spheres of the three complexes (Table-10) shows a more
crowded environment for the complex 7a compared with others,
as evidenced by their lower value and is mainly because of the
absence of perchlorate ion or DMF in the lattice. Globularity is a
measure of the degree of deviation of the surface area from that
of a sphere of an analogous volume. The lower globularity and the
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Declaration of Competing Interest
2
6 (2007) 5088–5094, doi:10.1016/j.poly.2007.07.028.
The authors declare that “there are no conflicts of interest to
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CRediT authorship contribution statement
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