Polymeric complexes - LXI. Supramolecular structure, thermal properties, SS-DNA binding activity and antimicrobial activities of polymeric complexes of rhodanine hydrazone compounds

Article abstract of DOI:10.1016/j.molliq.2015.12.010

A series of new ligands 5-(4′-alkylphenylazo)-3-phenylamino-2-thioxothiazolidin-4-one (HL_n) were synthesized from the coupling of 3-phenylamino-2-thioxothiazolidin-4-one with aniline and its p-derivatives. These ligands and their Co(II) polymeric complexes of the [(Co)₂(L_n)₂(HL_n)(CH₃COO)₂(H₂O)₂]_n have been deduced from elemental analyses, IR, ¹H-NMR, X-ray diffraction and mass spectra as well as magnetic and thermal measurements. IR and ¹H NMR studies reveal that the ligands (HL_n) exist in the tautomeric enol/hydrazo form in both states with intramolecular hydrogen bonding. The important infrared (IR) spectral bands imply that HL_n is coordinated to the metal ion in a monobasic tetradentate via NH (hydrazone), oxygen of the carbonyl group (CO), nitrogen of the NH (3-phenylamine) and thion sulfur (CS) group. The complexes are polymeric, non-electrolytes, paramagnetic and octahedral six-coordinated. The molecular and electronic structures of the investigated compounds (HL_n) were also studied using quantum chemical calculations. The salmon sperm DNA (SS-DNA) binding activity of the ligands (HL_n) was studied by absorption spectra. The interaction between ligands (HL_n) and SS-DNA shows hypochromism effect coupled with obvious bathochromism. The values of binding constant are correlated with Hammett's constant (σ^R). The cytotoxic activity of ligands (HL_n) and their Co(II) complexes were tested against two human cancer HePG-2 (Hepatocellular carcinoma) and MCF-7 (breast cancer). The antioxidant activities of ligands (HL_n) and their Co(II) complexes were performed by ABTS method. The antimicrobial activity of ligands HL_n and their Co(II) complexes were tested against Gram negative bacteria (Escherichia coli), Gram positive bacteria (Staphylococcus aureus) and yeast (Candida albicans).

Full text of DOI:10.1016/j.molliq.2015.12.010

Journal of Molecular Liquids 215 (2016) 711–739
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
Polymeric complexes — LXI. Supramolecular structure, thermal
properties, SS-DNA binding activity and antimicrobial activities of
polymeric complexes of rhodanine hydrazone compounds
b
c
a
A.Z. El-Sonbati a, M.A. Diab a, A.A. El-Bindary a, , M.M. Ghoneim , M.T. Mohesien , M.K. Abd El-Kader
⁎
a
Chemistry Department, Faculty of Science, Damietta University, Damietta 34517, Egypt
b
Chemistry Department, Faculty of Science, Tanta University, Tanta, Egypt
c
Botany Department, Faculty of Science, Damietta University, Damietta 34517, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of new ligands 5-(4′-alkylphenylazo)-3-phenylamino-2-thioxothiazolidin-4-one (HLn) were synthe-
sized from the coupling of 3-phenylamino-2-thioxothiazolidin-4-one with aniline and its p-derivatives. These
ligands and their Co(II) polymeric complexes of the [(Co)2(Ln)2(HLn)(CH3COO)2(H2O)2]n have been deduced
from elemental analyses, IR, 1H-NMR, X-ray diffraction and mass spectra as well as magnetic and thermal
measurements. IR and 1H NMR studies reveal that the ligands (HLn) exist in the tautomeric enol/hydrazo form
in both states with intramolecular hydrogen bonding. The important infrared (IR) spectral bands imply that
HLn is coordinated to the metal ion in a monobasic tetradentate via NH (hydrazone), oxygen of the carbonyl
group (CO), nitrogen of the NH (3-phenylamine) and thion sulfur (CS) group. The complexes are polymeric,
non-electrolytes, paramagnetic and octahedral six-coordinated. The molecular and electronic structures of the
investigated compounds (HLn) were also studied using quantum chemical calculations. The salmon sperm
DNA (SS-DNA) binding activity of the ligands (HLn) was studied by absorption spectra. The interaction between
ligands (HLn) and SS-DNA shows hypochromism effect coupled with obvious bathochromism. The values of
binding constant are correlated with Hammett's constant (σR). The cytotoxic activity of ligands (HLn) and their
Co(II) complexes were tested against two human cancer HePG-2 (Hepatocellular carcinoma) and MCF-7 (breast
cancer). The antioxidant activities of ligands (HLn) and their Co(II) complexes were performed by ABTS method.
The antimicrobial activity of ligands HLn and their Co(II) complexes were tested against Gram negative bacteria
(Escherichia coli), Gram positive bacteria (Staphylococcus aureus) and yeast (Candida albicans).
Received 21 October 2015
Received in revised form 8 November 2015
Accepted 2 December 2015
Available online xxxx
Keywords:
Co(II) complexes
SS-DNA binding
Molecular structure
Antimicrobial activities
© 2015 Elsevier B.V. All rights reserved.
1. Introduction
keto–enol tautomers. Hydrazone compounds of rhodanine usually
react as chelating with transition metal ions by bonding through the
In recent past, a variety of molecules based on rhodanine have been
synthesized and evaluated with improved pharmacological activities
due to their wide range of pharmacological and clinical utilization
[1–8]. Rhodanine compounds and their complexes play an important
role in biological reactions [9,10]. These molecules are considered
as good antimycobacterial, antifungal, antidiabetic, antihepatitis C
virus (HCV), anticancer, antioxidant, pesticidal, antihypertensive and
antineoplastic agents. These molecules attracted much attention and
encouraged the chemists and biologists to extensive investigations or
molecular manipulations [5,11]. Chemical properties of rhodanine and
its derivatives are of interest due to coordination capacity and their
use as metal extracting agents; these molecules are capable of having
oxygen and hydrazinic nitrogen atoms [1,8], as they form a stable six-
membered characterization of 5-(4′-alkylphenylazo)-3-phenylamino-
2-thioxothiazolidin-4-one (HLn) and their polymer complexes with
cobalt(II). HLn act as monobasic tetradentate reacting with Co(II)
through the CO (rhodanine moiety), hydrazinic N with displacement
of hydrogen atom, CS (rhodanine moiety) and amidic N.
DNA is one of the most important biomacromolecules in life
processes because it carries inheritance information and instructs
the biological synthesis of proteins and enzyme through the process
of replication and transcription of genetic information. DNA plays an
important role in the process of storing, copying and transmitting
gene messages. DNA is also a major target for drugs and some harm-
ful chemicals, and the studies on the binding nature of these small
molecules to DNA are important and fundamental issues on life sci-
ence because these drugs and chemicals can significantly influence
the genetic information expression and result in some diseases
⁎
Corresponding author.
E-mail address: abindary@yahoo.com (A.A. El-Bindary).
http://dx.doi.org/10.1016/j.molliq.2015.12.010
0167-7322/© 2015 Elsevier B.V. All rights reserved.

712
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
Fig. 1. Structure of ligands (HLn).
Table 1
Physical properties and elemental analyses data of the ligands (HLn) and their Co(II) complexes (1–5).
% Exp. (calc.)
Compound
M.P. (°C)
Composition
C
H
N
M
HL1
131
–
53.60
(53.63)
46.22
(46.43)
56.00
(56.14)
48.03
(48.15)
54.90
(54.88)
46.77
(46.89)
49.70
(49.66)
43.14
4.00
(3.91)
3.56
(3.72)
4.10
(4.09)
3.66
(3.86)
3.70
(3.66)
3.35
(3.51)
3.10
(3.03)
2.89
15.60
(15.64)
12.12
(12.50)
16.40
(16.37)
12.74
(12.96)
17.10
(17.07)
12.04
(13.40)
15.50
(15.45)
12.03
–
8.37
(8.77)
–
(1)
HL2
(2)
HL3
(3)
HL4
[(Co)2(HL1)(L1)2(CH3COO)2(H2O)2]n
[(Co)2(HL2)(L2)2(CH3COO)2(H2O)2]n
[(Co)2(HL3)(L3)2(CH3COO)2(H2O)2]n
[(Co)2(HL4)(L4)2(CH3COO)2(H2O)2]n
[(Co)2(HL5)(L5)2(CH3COO)2(H2O)2]n
161
–
8.78
(9.10)
–
164
–
(9.40)
–
164
–
8.47
(8.68)
–
(4)
(43.32)
48.30
(48.26)
42.12
(3.02)
3.00
(2.95)
2.87
(12.38)
18.80
(18.77)
14.86
HL5
178
–
8.15
(8.49)
(5)
(42.34)
(2.95)
(15.12)
aMicroanalytical data as well as metal estimations are in good agreement with the stoichiometry of the proposed complexes.
bThe excellent agreement between calculated and experimental data supports the assignment suggested in the present work.
cHL1–HL5 are the ligands and L1–L5 are the anions.

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
713
the complexes of these ligands with cobalt acetate [7]. The Co(II)
complexes attracted attention in coordination chemistry, thermal
stability and biological function of some bimetallic complexes for
which structural information was obtained by spectrochemical and
magnetochemical means; due to the Co(II) in d7 is known, in four co-
ordinate as tetrahedral and six coordinate as octahedral stereochem-
istries [14–18].
The aim of this work is to, synthesis and characterize of Co(II) com-
plexes of 5-(4′-alkylphenylazo)-3-phenylamino-2-thioxothiazolidin-4-
one (HLn) by elemental analyses, IR, 1H & 13C NMR, UV–Vis, X-ray
diffractometer, magnetic moment, molar conductance, and thermal
analysis. Molecular and electronic structures of the ligands (HLn) have
been discussed. Mass spectra and X-ray diffraction analysis of ligands
(HL1, HL3 and HL4) were discussed. The activation thermodynamic
Fig. 2. Proposed structure of Co(II) complexes.
⁎
parameters, such as activation energy (Ea), enthalpy (ΔH ), entropy
related to the cell proliferation and differentiation [12,13]. In our
laboratories, we have initiated a series of studies of the effects of sub-
stituents at p-position of the aromatic amine on the stoichiometries of
⁎
⁎
(ΔS ), and Gibbs free energy change of the decomposition (ΔG ) were
calculated using Coats–Redfern and Horowitz–Metzger methods. The
Fig. 3. The molecular structures for HLn.

714
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
Table 2
The selected geometric parameters for HL1.
Bond lengths (Å)
Bond angles (°)
Bond angles (°)
C(25)–H(38)
C(25)–H(37)
C(25)–H(36)
C(21)–H(35)
C(20)–H(34)
C(18)–H(33)
C(17)–H(32)
C(11)–H(31)
C(10)–H(30)
C(9)–H(29)
C(8)–H(28)
C(7)–H(27)
N(6)–H(26)
C(17)–C(22)
C(21)–C(22)
C(20)–C(21)
C(19)–C(20)
C(18)–C(19)
C(17)–C(18)
C(7)–C(12)
C(11)–C(12)
C(10)–C(11)
C(9)–C(10)
C(8)–C(9)
1.113
1.113
1.113
1.104
1.102
1.104
1.103
1.104
1.103
1.103
1.103
1.103
1.051
1.345
1.345
1.343
1.348
1.347
1.342
1.346
1.345
1.342
1.342
1.342
1.342
1.003
1.037
1.273
1.249
1.272
1.351
1.375
1.281
1.575
1.221
1.377
1.479
1.794
1.374
1.374
1.409
H(38)–C(25)–H(37)
H(38)–C(25)–H(36)
H(38)–C(25)–O(24)
H(37)–C(25)–H(36)
H(37)–C(25)–O(24)
H(36)–C(25)–O(24)
C(19)–O(24)–C(25)
H(34)–C(20)–C(21)
H(34)–C(20)–C(19)
C(21)–C(20)–C(19)
C(20)–C(19)–C(18)
C(20)–C(19)–O(24)
C(18)–C(19)–O(24)
H(33)–C(18)–C(19)
H(33)–C(18)–C(17)
C(19)–C(18)–C(17)
H(35)–C(21)–C(22)
H(35)–C(21)–C(20)
C(22)–C(21)–C(20)
H(32)–C(17)–C(22)
H(32)–C(17)–C(18)
C(22)–C(17)–C(18)
C(17)–C(22)–C(21)
C(17)–C(22)–N(16)
C(21)–C(22)–N(16)
H(23)–N(16)–C(22)
H(23)–N(16)–N(15)
C(22)–N(16)–N(15)
C(5)–S(4)–C(3)
N(16)–N(15)–C(5)
H(30)–C(10)–C(11)
H(30)–C(10)–C(9)
C(11)–C(10)–C(9)
H(29)–C(9)–C(10)
H(29)–C(9)–C(8)
C(10)–C(9)–C(8)
H(28)–C(8)–C(9)
H(28)–C(8)–C(7)
C(9)–C(8)–C(7)
H(31)–C(11)–C(12)
H(31)–C(11)–C(10)
C(12)–C(11)–C(10)
H(27)–C(7)–C(12)
H(27)–C(7)–C(8)
C(12)–C(7)–C(8)
C(7)–C(12)–C(11)
C(7)–C(12)–N(6)
111.887
108.169
110.347
108.167
110.354
107.776
118.767
116.943
120.926
122.131
115.683
125.543
118.775
118.575
118.627
122.798
120.437
118.181
121.382
121.128
118.067
120.805
117.202
122.386
120.412
122.189
108.605
129.206
96.437
116.122
120.035
119.886
120.079
120.144
120.146
119.709
119.865
120.019
120.116
120.723
118.691
120.586
121.023
118.446
120.531
118.978
122.597
C(11)–C(12)–N(6)
H(26)–N(6)–C(12)
H(26)–N(6)–N(2)
C(12)–N(6)–)–N(2)
S(14)–C(3)–S(4)
S(14)–C(3)–N(2)
S(4)–C(3)–N(2)
O(13)–H(23)–N(16)
N(6)–N(2)–C(3)
N(6)–N(2)–C(1)
C(3)–N(2)–C(1)
H(23)–O(13)–C(1)
N(15)–C(5)–C(1)
N(15)–C(5)–S(4)
C(1)–C(5)–S(4)
O(13)–C(1)–C(5)
O(13)–C(1)–N(2)
C(5)–C(1)–N(2)
Dihedral angle (°)
C(18)–C(17)–C(22)–N(16)
C(20)–C(21)–C(22)–N(16)
C(8)–C(7)–C(12)–N(6)
C(10)–C(11)–C(12)–N(6)
C(7)–C(12)–N(6)–N(2)
N(15)–C(5)–C(1)–N(2)
118.424
114.354
116.442
122.051
125.084
129.758
105.156
154.903
125.249
123.904
110.84
108.968
116.374
131.246
112.38
115.027
129.783
115.187
179.997
-179.99
179.986
-179.988
-32.896
-179.655
C(7)–C(8)
H(23)–O(13)
N(16)–H(23)
C(22)–N(16)
N(15)–N(16)
C(12)–N(6)
N(2)–N(6)
C(19)–O(24)
C(5)–N(15)
C(3)–S(14)
C(1)–O(13)
C(5)–C(1)
S(4)–C(5)
C(3)–S(4)
N(2)–C(3)
C(1)–N(2)
O(24)–C(25)
Table 3
The selected geometric parameters for HL2.
Bond lengths (Å)
Bond angles (°)
Bond angles (°)
C(23)–H(37)
C(23)–H(36)
C(23)–H(35)
C(21)–H(34)
C(20)–H(33)
C(18)–H(32)
C(17)–H(31)
C(11)–H(30)
C(10)–H(29)
C(9)–H(28)
C(8)–H(27)
C(7)–H(26)
N(6)–H(25)
C(17)–C(22)
C(21)–C(22)
C(20)–C(21)
C(19)–C(20)
C(18)–C(19)
C(17)–C(18)
C(7)–C(12)
1.114
1.114
1.113
1.104
1.103
1.103
1.103
1.104
1.103
1.103
1.103
1.103
1.051
1.346
1.346
1.342
1.344
1.344
1.343
1.346
1.345
H(37)–C(23)–H(36)
H(37)–C(23)–H(35)
H(37)–C(23)–C(19)
H(36)–C(23)–H(35)
H(36)–C(23)–C(19)
H(35)–C(23)–C(19)
H(33)–C(20)–C(21)
H(33)–C(20)–C(19)
C(21)–C(20)–C(19)
C(20)–C(19)–C(18)
C(20)–C(19)–C(23)
C(18)–C(19)–C(23)
H(32)–C(18)–C(19)
H(32)–C(18)–C(17)
C(19)–C(18)–C(17)
H(34)–C(21)–C(22)
H(34)–C(21)–C(20)
C(22)–C(21)–C(20)
H(31)–C(17)–C(22)
H(31)–C(17)–C(18)
C(22)–C(17)–C(18)
108.481
107.466
110.299
107.519
110.261
112.668
119.462
119.492
121.045
118.008
120.302
121.69
119.877
119.118
121.006
120.811
118.114
121.075
121.077
117.833
121.09
H(25)–N(6)–C(12)
H(25)–N(6)–N(2)
C(12)–N(6)–N(2)
S(14)–C(3)–S(4)
S(14)–C(3)–N(2)
S(4)–C(3)–N(2)
O(13)–H(24)–N(16)
N(6)–N(2)–C(3)
N(6)–N(2)–C(1)
114.364
116.46
122.051
125.08
129.763
105.156
154.915
125.252
123.907
110.834
108.969
116.371
131.248
112.381
115.024
129.783
115.191
C(3)–N(2)–C(1)
H(24)–O(13)–C(1)
N(15)–C(5)–C(1)
N(15)–C(5)–S(4)
C(1)–C(5)–S(4)
O(13)–C(1)–C(5)
O(13)–C(1)–N(2)
C(5)–C(1)–N(2)
Dihedral angle (°)
C(18)–C(17)–C(22)–N(16)
C(20)–C(21)–C(22)–N(16)
C(8)–C(7)–C(12)–N(6)
−179.998
−179.998
179.979
C(11)–C(12)

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
715
Table 3 (continued)
Bond lengths (Å)
Bond angles (°)
Bond angles (°)
C(10)–C(11)
C(9)–C(10)
C(8)–C(9)
1.342
1.342
1.342
1.342
1.004
1.037
1.274
1.249
1.272
1.351
1.51
1.281
1.575
1.221
1.377
1.479
1.794
1.374
1.374
C(17)–C(22)–C(21)
C(17)–C(22)–N(16)
C(21)–C(22)–N(16)
H(24)–N(16)–C(22)
H(24)–N(16)–N(15)
C(22)–N(16)–N(15)
C(5)–S(4)–C(3)
N(16)–N(15)–C(5)
H(29)–C(10)–C(11)
H(29)–C(10)–C(9)
C(11)–C(10)–C(9)
H(28)–C(9)–C(10)
H(28)–C(9)–C(8)
C(10)–C(9)–C(8)
H(27)–C(8)–C(9)
H(27)–C(8)–C(7)
C(9)–C(8)–C(7)
H(30)–C(11)–C(12)
H(30)–C(11)–C(10)
C(12)–C(11)–C(10)
H(26)–C(7)–C(12)
H(26)–C(7)–C(8)
C(12)–C(7)–C(8)
C(7)–C(12)–C(11)
C(7)–C(12)–N(6)
C(11)–C(12)–N(6)
117.775
122.127
120.097
122.19
108.581
129.228
96.438
116.139
120.036
119.883
120.081
120.147
120.145
119.708
119.867
120.016
120.117
120.723
118.695
120.581
121.026
118.444
120.53
C(10)–C(11)–C(12)–N(6)
C(7)–C(12)–N(6)–N(2)
N(15)–C(5)–C(1)–N(2)
−179.979
−32.812
−179.688
C(7)–C(8)
H(24)–O(13)
N(16)–H(24)
C(22)–N(16)
N(15)–N(16)
C(12)–N(6)
N(2)–N(6)
C(19)–C(23)
C(5)–N(15)
C(3)–S(14)
C(1)–O(13)
C(5)–C(1)
S(4)–C(5)
C(3)–S(4)
N(2)–C(3)
C(1)–N(2)
118.981
122.586
118.431
Table 4
The selected geometric parameters for HL3.
Bond lengths (Å)
Bond angles (°)
Bond angles (°)
C(21)–H(34)
C(20)–H(33)
C(19)–H(32)
C(18)–H(31)
C(17)–H(30)
C(11)–H(29)
C(10)–H(28)
C(9)–H(27)
C(8)–H(26)
C(7)–H(25)
N(6)–H(24)
C(17)–C(22)
C(21)–C(22)
C(20)–C(21)
C(19)–C(20)
C(18)–C(19)
C(17)–C(18)
C(7)–C(12)
C(11)–C(12)
C(10)–C(11)
C(9)–C(10)
C(8)–C(9)
1.104
1.103
1.103
1.103
1.103
1.104
1.103
1.103
1.103
1.103
1.051
1.347
1.347
1.342
1.341
1.341
1.343
1.346
1.345
1.342
1.342
1.342
1.342
1.003
1.037
1.274
1.249
1.272
1.351
1.281
1.575
1.221
1.377
1.479
1.794
1.374
1.374
H(33)–C(20)–C(21)
H(33)–C(20)–C(19)
C(21)–C(20)–C(19)
H(32)–C(19)–C(20)
H(32)–C(19)–C(18)
C(20)–C(19)–C(18)
H(31)–C(18)–C(19)
H(31)–C(18)–C(17)
C(19)–C(18)–C(17)
H(34)–C(21)–C(22)
H(34)–C(21)–C(20)
C(22)–C(21)–C(20)
H(30)–C(17)–C(22)
H(30)–C(17)–C(18)
C(22)–C(17)–C(18)
C(17)–C(22)–C(21)
C(17)–C(22)–N(16)
C(21)–C(22)–N(16)
H(23)–N(16)–C(22)
H(23)–N(16)–N(15)
C(22)–N(16)–N(15)
C(5)–S(4)–C(3)
N(16)–N(15)–C(5)
H(28)–C(10)–C(11)
H(28)–C(10)–C(9)
C(11)–C(10)–C(9)
H(27)–C(9)–C(10)
H(27)–C(9)–C(8)
C(10)–C(9)–C(8)
H(26)–C(8)–C(9)
H(26)–C(8)–C(7)
C(9)–C(8)–C(7)
120.073
119.833
120.094
120.261
120.264
119.475
119.779
120.051
120.17
O(13)–H(23)–N(16)
N(6)–N(2)–C(3)
N(6)–N(2)–C(1)
C(3)–N(2)–C(1)
H(23)–O(13)–C(1)
N(15)–C(5)–C(1)
N(15)–C(5)–S(4)
C(1)–C(5)–S(4)
O(13)–C(1)–C(5)
O(13)–C(1)–N(2)
154.932
125.247
123.915
110.831
108.97
116.365
131.255
112.381
115.021
129.784
115.192
120.84
118.03
121.13
C(5)–C(1)–N(2)
Dihedral angle (°)
C(18)–C(17)–C(22)–N(16)
C(20)–C(21)–C(22)–N(16)
C(8)–C(7)–C(12)–N(6)
C(10)–C(11)–C(12)–N(6)
C(7)–C(12)–N(6)–N(2)
N(15)–C(5)–C(1)–N(2)
121.177
117.779
121.044
118.088
121.969
119.943
122.183
108.56
179.985
−179.985
179.987
−179.978
−32.818
−179.634
129.257
96.436
C(7)–C(8)
116.153
120.033
119.886
120.081
120.146
120.15
119.704
119.864
120.017
120.119
120.724
118.692
120.584
121.023
118.448
120.529
118.98
H(23)–O(13)
N(16)–H(23)
C(22)–N(16)
N(15)–N(16)
C(12)–N(6)
N(2)–N(6)
C(5)–N(15)
C(3)–S(14)
C(1)–O(13)
C(5)–C(1)
H(29)–C(11)–C(12)
H(29)–C(11)–C(10)
C(12)–C(11)–C(10)
H(25)–C(7)–C(12)
H(25)–C(7)–C(8)
C(12)–C(7)–C(8)
C(7)–C(12)–C(11)
C(7)–C(12)–N(6)
C(11)–C(12)–N(6)
S(4)–C(5)
C(3)–S(4)
N(2)–C(3)
C(1)–N(2)
122.597
118.422
(continued on next page)

716
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
Table 4 (continued)
Bond lengths (Å)
Bond angles (°)
Bond angles (°)
H(24)–N(6)–C(12)
H(24)–N(6)–N(2)
C(12)–N(6)–N(2)
S(14)–C(3)–S(4)
S(14)–C(3)–N(2)
S(4)–C(3)–N(2)
114.354
116.459
122.069
125.08
129.76
105.159
salmon sperm DNA binding activity of the ligands (HLn) was studied by
absorption spectra measurements.
sperm DNA (SS-DNA) was purchased from SRL (India). Double distilled
water was used to prepare all buffer solutions.
2.2. Preparation of azodye ligands
2. Experimental
Preparation
of
5-(4′-alkylphenylazo)-3-phenylamino-2-
2.1. Materials
thioxothiazolidin-4-one (HLn) (Fig. 1); 25 ml of distilled water contain-
ing hydrochloric acid was added to aniline or a 4-alkyl-aniline. To the
resulting mixture stirred and cooled to 0 °C, a solution of sodium nitrite
0.01 mol in 20 ml of water was added dropwise. The formed diazonium
chloride was consecutively coupled with an alkaline solution of 3-
phenylamino-2-thioxothiazolidin-4-one 0.01 mol in 10 ml of pyridine.
3-Phenylamino-2-thioxtiazolidin-4-one was prepared previously
[1,8,13]. The standard chemical cobalt acetate, aniline and 4-
alkylanilines (alkyl: CH3, OCH3, Cl and NO2) were purchased from
Sigma and Aldrich and used without any further purification. Salmon
Table 5
The selected geometric parameters for HL4.
Bond lengths (Å)
Bond angles (°)
Bond angles (°)
C(21)–H(34)
C(20)–H(33)
C(18)–H(32)
C(17)–H(31)
C(11)–H(30)
C(10)–H(29)
C(9)–H(28)
C(8)–H(27)
C(7)–H(26)
N(6)–H(25)
C(17)–C(22)
C(21)–C(22)
C(20)–C(21)
C(19)–C(20)
C(18)–C(19)
C(17)–C(18)
C(7)–C(12)
C(11)–C(12)
C(10)–C(11)
C(9)–C(10)
C(8)–C(9)
1.104
1.103
1.103
1.103
1.104
1.103
1.103
1.103
1.103
1.051
1.347
1.347
1.343
1.342
1.342
1.343
1.346
1.345
1.342
1.342
1.342
1.342
1.003
1.037
1.274
1.249
1.272
1.351
1.727
1.281
1.575
1.221
1.377
1.479
1.794
1.374
1.374
H(33)–C(20)–C(21)
H(33)–C(20)–C(19)
C(21)–C(20)–C(19)
C(20)–C(19)–C(18)
C(20)–C(19)–Cl(23)
C(18)–C(19)–Cl(23)
H(32)–C(18)–C(19)
H(32)–C(18)–C(17)
C(19)–C(18)–C(17)
H(34)–C(21)–C(22)
H(34)–C(21)–C(20)
C(22)–C(21)–C(20)
H(31)–C(17)–C(22)
H(31)–C(17)–C(18)
C(22)–C(17)–C(18)
C(17)–C(22)–C(21)
C(17)–C(22)–N(16)
C(21)–C(22)–N(16)
H(24)–N(16)–C(22)
H(24)–N(16)–N(15)
C(22)–N(16)–N(15)
C(5)–S(4)–C(3)
N(16)–N(15)–C(5)
H(29)–C(10)–C(11)
H(29)–C(10)–C(9)
C(11)–C(10)–C(9)
H(28)–C(9)–C(10)
H(28)–C(9)–C(8)
C(10)–C(9)–C(8)
H(27)–C(8)–C(9)
H(27)–C(8)–C(7)
C(9)–C(8)–C(7)
H(30)–C(11)–C(12)
H(30)–C(11)–C(10)
C(12)–C(11)–C(10)
H(26)–C(7)–C(12)
H(26)–C(7)–C(8)
C(12)–C(7)–C(8)
C(7)–C(12)–C(11)
C(7)–C(12)–N(6)
C(11)–C(12)–N(6)
H(25)–N(6)–C(12)
H(25)–N(6)–N(2)
C(12)–N(6)–N(2)
S(14)–C(3)–S(4)
119.374
120.663
119.962
119.575
120.223
120.201
120.612
119.34
O(13)–H(24)–N(16)
N(6)–N(2)–C(3)
N(6)–N(2)–C(1)
C(3)–N(2)–C(1)
H(24)–O(13)–C(1)
N(15)–C(5)–C(1)
N(15)–C(5)–S(4)
C(1)–C(5)–S(4)
O(13)–C(1)–C(5)
O(13)–C(1)–N(2)
154.955
125.246
123.92
110.827
108.971
116.366
131.251
112.383
115.007
129.797
115.194
120.048
120.75
118.006
121.244
121.082
117.768
121.149
118.021
122.004
119.975
122.169
108.541
129.289
96.431
C(5)–C(1)–N(2)
Dihedral angle (°)
C(18)–C(17)–C(22)–N(16)
C(20)–C(21)–C(22)–N(16)
C(8)–C(7)–C(12)–N(6)
C(10)–C(11)–C(12)–N(6)
C(7)–C(12)–N(6)–N(2)
N(15)–C(5)–C(1)–N(2)
−179.999
180
179.984
−179.986
−32.136
−179.659
C(7)–C(8)
H(24)–O(13)
N(16)–H(24)
C(22)–N(16)
N(15)–N(16)
C(12)–N(6)
N(2)–N(6)
C(19)–Cl(23)
C(5)–N(15)
C(3)–S(14)
C(1)–O(13)
C(5)–C(1)
116.159
120.04
119.885
120.075
120.144
120.152
119.705
119.863
120.012
120.125
120.723
118.682
120.594
121.032
118.439
120.528
118.971
122.624
118.403
114.435
116.559
122.197
125.075
129.759
105.166
S(4)–C(5)
C(3)–S(4)
N(2)–C(3)
C(1)–N(2)
S(14)–C(3)–N(2)
S(4)–C(3)–N(2)

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
717
The colored precipitate, which formed immediately, was filtered and
washed several times with water. The crude product was purified by
recrystallization from hot ethanol [7]. The analytical data confirmed
the expected compositions (Table 1). The ligands (Fig. 1) were also
characterized by 1H NMR and IR spectroscopy.
(0.03 mol) in EtOH (20 cm3) was added dropwise to a hot EtOH solution
(20 cm3) of Co(CH3COO)2·4H2O (0.02 mol) with stirring and the reac-
tion mixture was refluxed for 3 h. The solution was concentrated to
half of its original volume by evaporation and allowed to cool at room
temperature. During this, a polycrystalline solid was separated, which
was isolated by filtration, washed with EtOH, ether and dried in vacuo
over anhydrous CaCl2. Formation of the polymer complexes (Fig. 2)
can be obtainable in the following reaction:
The resulting formed ligands are:
HL1
=
5-(4′-methoxyphenylazo)-3-phenylamino-2-
thioxothiazolidin-4-one.
2Co(CH3COO)2 . 4H2O + 3HLn → [(Co)2(Ln)2(HLn)(CH3COO)2(H2O)2]
HL2 = 5-(4′-methylphenylazo)-3-phenylamino-2-thioxothiazolidin-
4-one.
HL3 = 5-(phenylazo)-3-phenylamino-2-thioxothiazolidin-4-one.
HL4 = 5-(4′-chlorophenylazo)-3-phenylamino-2-thioxothiazolidin-
2.4. Measurements
4-one.
Microanalytical data (C, H and N) were collected on Automatic
Analyzer CHNS Vario ELIII, Germany. Spectroscopic data were obtained
using the following instruments: FT-IR spectra (KBr disks, 4000–
400 cm−1) by Jasco FTIR-4100 spectrophotometer; the 1H-NMR spectra
by Bruker WP 300 MHz using DMSO-d6 as a solvent containing TMS as
the internal standard. X-ray diffraction analysis of compounds in pow-
der forms was recorded on X-ray diffractometer in the range of diffrac-
tion angle 2θ = 4–80°. This analysis was carried out using CuKα
HL5 = 5-(4′-nitrophenylazo)-3-phenylamino-2-thioxothiazolidin-
4-one.
2.3. Preparation of Co(II) complexes
All Co(II) polymer complexes were synthesized according to the
general procedure [7]: a stoichiometric amount of the desired ligand
Table 6
The selected geometric parameters for HL5.
Bond lengths (Å)
Bond angles (°)
Bond angles (°)
C(21)–H(36)
C(20)–H(35)
C(18)–H(34)
C(17)–H(33)
C(11)–H(32)
C(10)–H(31)
C(9)–H(30)
C(8)–H(29)
C(7)–H(28)
N(6)–H(27)
C(17)–C(22)
C(21)–C(22)
C(20)–C(21)
C(19)–C(20)
C(18)–C(19)
C(17)–C(18)
C(7)–C(12)
C(11)–C(12)
C(10)–C(11)
C(9)–C(10)
C(8)–C(9)
1.104
1.104
1.104
1.104
1.104
1.103
1.103
1.103
1.103
1.051
1.346
1.345
1.344
1.348
1.347
1.343
1.346
1.345
1.342
1.342
1.342
1.342
1.005
1.038
1.275
1.25
1.272
1.351
1.259
1.28
1.575
1.221
1.376
1.479
1.794
1.374
1.375
1.316
1.315
C(19)–N(24)–O(26)
C(19)–N(24)–O(25)
O(26)–N(24)–O(25)
H(35)–C(20)–C(21)
H(35)–C(20)–C(19)
C(21)–C(20)–C(19)
C(20)–C(19)–C(18)
C(20)–C(19)–N(24)
C(18)–C(19)–N(24)
H(34)–C(18)–C(19)
H(34)–C(18)–C(17)
C(19)–C(18)–C(17)
H(36)–C(21)–C(22)
H(36)–C(21)–C(20)
C(22)–C(21)–C(20)
H(33)–C(17)–C(22)
H(33)–C(17)–C(18)
C(22)–C(17)–C(18)
C(17)–C(22)–C(21)
C(17)–C(22)–N(16)
C(21)–C(22)–N(16)
H(23)–N(16)–C(22)
H(23)–N(16)–N(15)
C(22)–N(16)–N(15)
C(5)–S(4)–C(3)
N(16)–N(15)–C(5)
H(31)–C(10)–C(11)
H(31)–C(10)–C(9)
C(11)–C(10)–C(9)
H(30)–C(9)–C(10)
H(30)–C(9)–C(8)
C(10)–C(9)–C(8)
H(29)–C(8)–C(9)
H(29)–C(8)–C(7)
C(9)–C(8)–C(7)
H(32)–C(11)–C(12)
H(32)–C(11)–C(10)
C(12)–C(11)–C(10)
H(28)–C(7)–C(12)
H(28)–C(7)–C(8)
C(12)–C(7)–C(8)
C(7)–C(12)–C(11)
C(7)–C(12)–N(6)
C(11)–C(12)–N(6)
H(27)–N(6)–C(12)
H(27)–N(6)–N(2)
C(12)–N(6)–N(2)
123.194
123.277
113.529
117.229
120.927
121.844
116.528
122.139
121.333
121.134
117.124
121.742
120.232
118.425
121.342
121.014
117.472
121.514
117.03
S(14)–C(3)–S(4)
S(14)–C(3)–N(2)
S(4)–C(3)–N(2)
O(13)–H(23)–N(16)
N(6)–N(2)–C(3)
N(6)–N(2)–)–C(1)
C(3)–N(2)–C(1)
H(23)–O(13)–C(1)
N(15)–C(5)–C(1)
N(15)–C(5)–S(4)
C(1)–C(5)–S(4)
O(13)–C(1)–C(5)
O(13)–C(1)–N(2)
C(5)–C(1)–N(2)
Dihedral angle (°)
C(18)–C(17)–C(22)–N(16)
C(20)–C(21)–C(22)–N(16)
C(8)–C(7)–C(12)–N(6)
C(10)–C(11)–C(12)–N(6)
C(7)–C(12)–N(6)–N(2)
N(15)–C(5)–C(1)–N(2)
125.137
129.758
105.104
154.405
125.155
123.876
110.964
108.934
116.031
131.371
112.597
115.476
129.532
114.989
−179.933
179.94
179.976
−179.978
−33.186
−179.523
121.919
121.05
123.452
108.738
127.808
96.346
C(7)–C(8)
H(23)–O(13)
N(16)–H(23)
C(22)–N(16)
N(15)–N(16)
C(12)–N(6)
N(2)–N(6)
C(19)–N(24)
C(5)–N(15)
C(3)–S(14)
C(1)–O(13)
C(5)–C(1)
S(4)–C(5)
C(3)–S(4)
N(2)–C(3)
C(1)–N(2)
N(24)–O(26)
N(24)–O(25)
116.416
120.034
119.885
120.082
120.148
120.143
119.71
119.872
120.012
120.116
120.726
118.697
120.577
121.017
118.457
120.526
118.988
122.567
118.445
114.324
116.416
121.983

718
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
Fig. 4. The molecular structures (HOMO &LUMO) for HLn.

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
719
Table 7
The calculated quantum chemical parameters for the ligands (HLn).
EHOMO
(eV)
ELUMO
(eV)
ΔE
(eV)
χ
(eV)
η
(eV)
σ
Pi
(eV)
S
ω
(eV)
Comp.
ΔNmax
(eV)−1
(eV)−1
HL1
HL2
HL3
HL4
HL5
−1.671
−1.907
−2.035
−1.614
−4.249
−0.333
−0.332
−0.332
−0.333
−0.004
1.338
1.575
1.703
1.281
4.245
1.002
0.669
1.49476831
1.26984127
1.17439812
1.56128025
0.47114252
−1.002
0.74738416
0.63492063
0.58719906
0.78064012
0.23557126
0.75037668
0.79573349
0.82247343
0.7398144
1.06525377
1.49775785
1.4215873
1.38990018
1.51990632
1.00188457
1.1195
1.1835
0.9735
2.1265
0.7875
0.8515
0.6405
2.1225
−1.1195
−1.1835
−0.9735
−2.1265
radiation (λ = 1.540598 Ả). The applied voltage and the tube current
are 40 KV and 30 mA, respectively. Mass spectra were recorded by the
EI technique at 70 eV using MS-5988 GS-MS Hewlett-Packard. UV–
Visible spectra by Perkin-Elmer AA800 spectrophotometer Model AAS.
Thermal analysis of the ligands and their Co (II) complexes was carried
out using a Shimadzu thermogravimetric analyzer under a nitrogen
atmosphere with heating rate of 10 °C/min over a temperature range
from 30 °C up to 800 °C. Magnetic susceptibility measurements were
determined at room temperature on a Johnson Matthey magnetic
susceptibility balance using Hg[Co(SCN)4] as calibrate. Conductivity
buffer solution to eliminate the absorbance of SS-DNA itself. The intrin-
sic binding constant Kb of the compound with SS-DNA was determined
using the following Eq. (1) [23]:
ꢀ
ꢁ
ꢀ
ꢁ
ꢀ
ꢁ
½DNAꢀ= єa–єf ¼ ½DNAꢀ= єb–єf þ 1=Kb єa–єf
ð1Þ
where [DNA] is the concentration of SS-DNA in base pairs, єa is the
extinction coefficient observed for the Aobs/[compound] at the given
DNA concentration, єf is the extinction coefficient of the free compound
in solution and єb is the extinction coefficient of the compound when
fully bond to DNA. In plots of [DNA] / (єa − єf) vs. [DNA], Kb is given
by the ratio of the slope to the intercept.
measurements of the complexes at 25
1 °C were determined in
DMF (10−3 M) using conductivity/TDS meter model Lutron YK-22CT.
The molecular structures of the investigated compounds were
optimized by HF method with 3-21G basis set. The molecules were
built with the Perkin Elmer ChemBio Draw and optimized using Perkin
Elmer ChemBio3D software [18,19].
2.6. Cytotoxicity investigation
2.6.1. Cell lines and chemical reagents
Hepatocellular carcinoma (HePG-2) and mammary gland breast
cancer (MCF-7) cell lines were obtained from ATCC via Holding compa-
ny for biological products and vaccines (VACSERA), Cairo, Egypt.
Chemical reagents; RPMI-1640 medium, MTT, DMSO and 5-fluorouracil
were purchased from Sigma chemicals (St. Louis, USA), Fetal Bovine
serum (FBS) was purchased from (GIBCO, UK). 5-fluorouracil (5-FU)
was used as a standard anticancer drug for comparison.
2.5. DNA binding experiments
The binding properties of the ligands and their complexes to SS-DNA
have been studied using electronic absorption spectroscopy. SS-DNA
(50 mg) was dissolved by stirring overnight in double deionized
water (pH = 7.0) and kept at 4 °C. Doubly distilled water was used to
prepare buffers (20 mM phosphate buffer (NaH2PO4–Na2HPO4),
pH = 7.2). A solution of (SS-DNA) in the buffer gave a ratio of UV absor-
bance at 260 and 280 nm (A260/A280) of ca. 1.8, indicating that the DNA
was sufficiently free of protein [20]. The DNA concentration was deter-
mined by UV absorbance spectroscopy using the molar absorption coef-
ficient of 6600 M−1 cm−1 at 260 nm for SS-DNA [21,22] and was found
to be 1.4 × 10−4. Electronic absorption spectra (200–900 nm) were car-
ried out using 1 cm quartz cuvette at 25 °C by fixing the concentration of
ligand (1.00 × 10−3 mol.L−1), while gradually increasing the concentra-
tion of SS-DNA (0.00 to 1.30 × 10−4 mol.L−1). An equal amount of
SS-DNA was added to both the compound solutions and the references
2.6.2. MTT assay
The cell lines mentioned above were used to determine the inhibito-
ry effects of ligands and their Co(II) complexes on cell growth using the
MTT assay [24]. This colorimetric assay is based on the conversion of the
yellow tetrazolium bromide (MTT) to a purple formazan derivative by
mitochondrial succinate dehydrogenase in viable cells. Cell lines were
cultured in RPMI-1640 medium with 10% fetal bovine serum. Antibi-
otics added were 100 units/ml penicillin and 100 μg/ml streptomycin
at 37 °C in a 5% CO2 incubator. The cell lines were seeded in a 96-well
plate at a density of 1.0 × 104 cells/well at 37 °C for 48 h under 5% Co2,
followed by 24 h incubation with the indicated drug doses [25]. In the
end of the drug treatment, 20 μl of MTT solution at 5 mg/ml was
added and incubated for 4 h. Dimethyl sulfoxide (DMSO) in volume of
100 μl is added into each well to dissolve the purple formazan formed.
The colorimetric assay is measured and recorded as absorbance at
570 nm using a plate reader (EXL 800). Cytotoxicity was expressed as
Table 8
IR data (cm−1) of free ligands (HLn) and their Co(II) complexes (1–5).
Compound
υ(NH)
υ(C = O)
υ(C = S)
υ(Co-O)
υ(Co-N)
υ(Co-S)
HL1
(1)
HL2
(2)
HL3
(3)
HL4
(4)
HL5
(5)
3207
–
3205
–
3209
–
3207
–
1751
1722
1754
1718
1727
1725
1751
1724
1735
1716
881
825
882
815
842
815
823
819
846
844
–
680
–
684
–
690
–
690
–
680
–
528
–
590
–
598
–
580
–
590
–
485
–
488
–
499
–
498
–
480
3210
–
Fig. 5. The relation between Hammett's substitution coefficients (σR) vs. energy gap (ΔE).
aNumbers as given in Table 1.

720
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
IC50 (μg/mL) which indicates the concentration of the compound that
inhibited proliferation rate of the tumor cells by 50% as compared to
the control untreated cells. IC50 values were determined from the plot:
% relative cell viability (% inhibition concentration) vs. compound con-
centration. The relative cell viability values were calculated as follows:
sample was run without ABTS and using MeOH/phosphate buffer
(1:1) instead of tested compounds. L-ascorbic acid was used as standard
antioxidant (positive control) and the negative control was run with
ABTS and MeOH/phosphate buffer (1:1) only.
A ðcontrolÞ−A ðtestÞ
A ð570 nmÞ of treated samples
%Inhibition ¼
ꢁ 100
%The relative cell viability ¼
ꢁ 100
A ðcontrolÞ
A ð570 nmÞ of untreated sample
2.8. Antimicrobial investigation
2.7. Antioxidant investigation
Rhodanine compounds were individually tested against Gram nega-
tive (Escherichia coli) bacteria, Gram positive (Staphylococcus aureus)
and yeast (Candida albicans). Each of the compounds was dissolved in
DMSO and solutions of the concentration 1 mg/ml were prepared sepa-
rately and paper disks of Whatman filter paper were prepared with
standard size (5 cm) and sterilized in an autoclave. The paper disks
were soaked in the desired concentration of the complex solution and
were placed aseptically in the petri dishes containing nutrient agar
media (agar 20 g, beef extract 3 g and peptone 5 g) seeded with
Staphylococcus aureus, E. coli and Candida albicans. The petri dishes
were incubated at 36 °C and the inhibition zones were recorded after
24 h of incubation. Each treatment was replicated three times. The
antibacterial activity of a common standard antibiotic ampicillin and
Antioxidant activity screening assay ABTS method [26–28] used for
determination of scavenging activity of ligands (HLn) and their Co(II)
complexes (1–5). For each of the investigated compounds (2 mL) of
ABTS (2,2′-azinobis-(3-ethyl-benzothiazoline-6-sulphonic acid)
solution (60 μM) was added to 3 mL MnO2 solution (25 mg/mL), all
prepared in (5 mL) aqueous phosphate buffer solution (pH 7, 0.1 M).
The mixture was shaken, centrifuged, filtered and the absorbance of
the resulting green blue solution (ABTS free radical solution) at
734 nm was adjusted to approx. ca. 0.5. Then, 50 μl of (2 mM) solution
of the tested compound in spectroscopic grade MeOH/phosphate buffer
(1:1) was added. The absorbance was measured and the reduction in
color intensity was expressed as inhibition percentage (I %). Blank
Fig. 6. X-ray diffraction patterns for ligands (HL1, HL3 and HL4) and the complex (1) in powder forms.

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
721
Fig. 7. a. Mass spectrum of HL1. b. Mass spectrum of HL3. c. Mass spectrum of HL4.

722
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
antifungal colitrimazole was also recorded using the same procedure as
above using the same concentration and solvents. The % activity index
for the complex was calculated by the formula:
structures (HOMO &LUMO) for HLn are presented in Fig. 4. The HOMO–
LUMO energy gap, ΔE, which is an important stability index, is applied
to develop theoretical models for explaining the structure and confor-
mation barriers in many molecular systems. The smaller the value of
ΔE is, the more the stability the compound has [3,18]. The calculated
quantum chemical parameters are given in Table 7. Additional parame-
ters such as separation energies, ΔE, absolute electronegativities, χ,
chemical potentials, Pi, absolute hardness, η, absolute softness, σ, global
electrophilicity, ω [29], global softness, S, and additional electronic charge,
ΔNmax, have been calculated according to the following Eqs. (2–9):
Zone of inhibition by test compound ðdiameterÞ
%Activity Index ¼
ꢁ 100
Zone of inhibition by standard ðdiameterÞ
3. Results and discussion
3.1. Molecular structure
The molecular structures of the ligands (HLn) were optimized by HF
method with 3-21G basis set. The molecules were built with the Perkin
Elmer ChemBioDraw and optimized using Perkin Elmer ChemBio3D
software. The geometrical parameters bond lengths and bond angles
of HLn are calculated and presented in Fig. 3 and Tables 2–6. Molecular
ΔE ¼ ELUMO−EHOMO
ð2Þ
ð3Þ
−ðEHOMO þ ELUMO
Þ
χ ¼
2
a)
b)
c)
Scheme 1. a. Fragmentation patterns of HL1. b. Fragmentation patterns of HL3. c. Fragmentation patterns of HL4.

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
723
Fig. 9. TGA curves of complexes (1–5).
Fig. 8. TGA curves of ligands HL
Table 10
Thermal analysis data of the complexes (1–5).
ELUMO−EHOMO
η ¼
ð4Þ
Complexa Temp. range (°C) Found mass loss (calc.) % Assignment
2
(1)
(2)
(3)
(4)
(5)
0–140
11.4 (11.45)
50.49 (50.75)
26.41(26.64)
11.7 (11.15)
11.19 (11.88)
50.95 (50.15)
25.9 (26.39)
11.96 (11. 56)
11.97 (12.27)
49.73 (49.6)
25.8(26.15)
12.8 (11.95)
11.42 (11.34)
50.36 (50.9)
26.4(26.7)
11.82 (11.04)
11.03 (11.08)
51.33 (51.26)
26.28(26.85)
10.36 (10.7)
Loss of C4H10O6.
σ ¼ 1=η
Pi ¼ −χ
ð5Þ
ð6Þ
140–510
510–800
N800
Loss of C32H26N8O2S4.
Loss of C16H14N4O2S2.
Loss of 2CoO
0–145
Loss of C4H10O6.
145–505
505–800
N800
Loss of C32H26N8S4.
Loss of C16H14N4OS2.
Loss of 2CoO
1
S ¼
ð7Þ
2η
0–160
Loss of C4H10O6.
ω ¼ Pi2=2η
ð8Þ
ð9Þ
160–550
550–800
N800
Loss of C30H22N8S4.
Loss of C15H12N4OS2.
Loss of 2CoO
ΔN max ¼ −Pi=η
0–155
Loss of C4H10O6.
155–515
515–800
N800
Loss of C30H20N8S4Cl2.
Loss of C15H11N4OS2Cl.
Loss of 2CoO
The value of ΔE for ligands HL1, HL2, HL3, HL4 and HL5 was found
1.338, 1.575, 1.703, 1.281 and 4.245 eV, respectively. The calculations
indicated that the HL4 is more stable form than the other ligands
[3].The relation between Hammett's substitution coefficients (σR) vs.
energy gap (ΔE) is shown in Fig. 5. It is clear that that the values increase
with increasing σR.
0–155
Loss of C4H10O6.
155–525
525–800
N800
Loss of C30H20N10O4S4.
Loss of C15H11N5O3S2.
Loss of 2CoO
a
Numbers as given in Table 1.
3.2. Metal complexes
The interaction of hydrazone ligands (HLn) with [Co(CH3COO)2].4H2O
in a molar ratio 2:3 [Co:HLn] under reflux conditions gave the polymeric
products presented in Table 1. The polymeric Co(II) complexes are stable
in air and soluble in DMF and DMSO. The molar conductance values for
the cobalt (II) complexes (10−3 M) are measured in DMF at 25 °C and
these values are in the range of 4–12 Ω−1 cm2 mol−1 indicating a non-
electrolytic nature [23]. The no electrolytic nature of the Co(II) polymeric
complexes implies the contribution of acetate ions to the coordination
sphere in the complexes under investigation.
Table 9
Thermal analysis data of the ligands (HLn).
Compound
Temp. range (°C)
Found mass loss (calc.) %
Assignment
30–260
260–570
570–800
30–265
265–700
700–800
30–330
330–800
30–350
350–800
30–400
62 (61.9)
30 (29.6)
8 (8.6)
65 (64.9)
30 (30.9)
5 (4.3)
68 (67.7)
32 (32.3)
71 (71.3)
29 (28.9)
59 (59.5)
28 (28.4)
13 (12.3)
Decomposition of a part of the ligand (C9H6N2S2O).
Further decomposition of a part of the ligand (C6H6N2).
Further decomposition of a part of the ligand (OCH3).
Decomposition of a part of the ligand (C9H6N2S2O).
Further decomposition of a part of the ligand (C6H6N2).
Further decomposition of a part of the ligand (CH3).
Decomposition of a part of the ligand (C9H6N2S2O).
Further decomposition of a part of the ligand (C6H6N2).
Decomposition of a part of the ligand (C9H7N2S2OCl).
Further decomposition of a part of the ligand (C6H5N2).
Decomposition of a part of the ligand (C9H6N2S2O).
Further decomposition of a part of the ligand (C6H6N2).
Further decomposition of a part of the ligand (NO2).
HL1
HL2
HL3
HL4
HL5
400–600
600–800

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Evidence for all polymeric nature comes from its solubility proper-
3.3. Infrared spectra and nature of coordination
ties and the metal polymer complex to ligand stoichiometry which is
shown to be 2:3 from the elemental analysis. IR spectroscopy provides
partial evidence that the ligand is acting as a bridge, and that bridging
occurs through both the S and NH from side and through O and N
(hydrazone) from the other side.
The three bands around 823–882, 3205–3210 and 1727–1754 cm−1
in the ligands assigned to υ(CS), –NH(3-phenylamine) and υ(CO)
groups, respectively, were shifted to lower frequencies and –NH(3-
phenylamine) disappearance in all polymer complexes. This indicates
Fig. 10. Coats–Redfern (CR) of ligands (HLn), Stages (I, II).

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
725
Fig. 10 (continued).
the participation of the thione sulfur, NH(3-phenylamine) and carbonyl
oxygen groups, in the chelation (Table 8) [30]. The splitting of υ(N=N)
band into two bands in the ranges 1435–1520 and ~1230 cm−1 due to
υ(HC=N) and υ(=N–NH) hydrazone, respectively, for ligands provides
an evidence that the hydrazone N participate in the chelation after depro-
tonation leading to a covalent linkage. This is more rather confirmed from
the observation of Karabatoses et al. [31] and El-Sonbati et al. [32] where
the hydrazone form is more than the azo structure for similar compounds
(Fig. 1D). In all polymer complexes, CN group remained intact, indicating
the non-participation of the azomethine nitrogen in the chelation [33].
The strong observed at ~1111–1123 cm−1 may be assigned to υ(N–N)
vibration mode [34] is affected on complexation. It is blue shifted and ap-
pearance as a weak band. In all polymer complexes, there are two bands
υas(1427–1444) and υs(1230–1243) cm−1 stretching vibration of acetate
group. The correlation between the positions of the antisymmetric and
symmetric stretching vibration of this group was earlier studied [35]. It
was concluded from these studies that the frequency difference between
the two carbonyl stretches of ionic acetate groups is usually in the interval
~160 cm−1, longer values were found for monodentate and lower values
for bidentate groups [36]. Correspondingly, the split of 195–201 cm−1 in
polymer complexes indicates monodentate acetate. This is supported by
results of Ryde [37].
The above interpretation is further supported by the appearance
of the non-ligand bands at: 680–690 cm−1; υ(Co–O), 528–598 cm−1
;
υ(Co–N) [38] and 480–500 cm−1; υ(Co–S) [39]. Such class of
compounds is with different types of hydrogen bonding [2–6]:
1. H-bonding of the type NH⋯O between the –NH (hydrazone) group
and C=O group.
2. Intermolecular hydrogen bonding of the NH⋯O type of one molecule
to another one.
3. The case is more favored. This is due to the presence of a broad band
located at 870–965 cm−1 which could be taken as a good evidence
for the intermolecular hydrogen bonding.
In all polymer complexes ~3500–3200 cm−1 is observed, such
region is attributed to different probabilities: (i) it is due to either free
OH or NH, (ii) bonded –OH group or –NH group or (iii) due to the
presence of coordinated water molecules.
3.4. 1H NMR spectra
The 1H NMR spectra of the ligands are recorded in dimethylsulfoxide
(DMSO-d6) solution using tetramethylsilane (TMS) as internal stan-
dard. The broad signal exhibited by the ligands can be assigned to

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A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
intramolecular hydrogen bonded proton of NH (hydrazone) at
∼11.5 ppm and NH(3-phenylamine) at ∼9.0 ppm were not affected by
dilution and disappear in the presence of D2O. The chemical shifts of
the different types of protons in the 1H NMR spectra of the ligands
(HL1 and HL2) display sharp signals at 3.7 and 2.3 ppm with an integra-
tion equivalent to three hydrogens corresponding to the O–CH3 and C–
CH3 groups, respectively. The aromatic rings give a group of multi sig-
nals at 6.5–8.0 ppm.
Fig. 11. Coats–Redfern (CR) of Co(II) complexes (1–5), Stages (I, II).

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
727
Fig. 11 (continued).
The 13C NMR of ligands exhibited signals at 170 _172 ppm
corresponding to the carbon of (C=N) groups, signals appear at 160–
163 ppm corresponding to (C=O) groups and signals around
~200 ppm corresponding to the carbon of (C=S). Ligands have different
chemical shift due to aromatic ring substituent. Therefore, it is clear
from these results that the data obtained from the elemental analyses;
IR and 1H NMR spectra measurements are in agreement with each
other.
fragmentation mode of ligand (HL1) shows the exact mass of 358 corre-
sponding to the formula C16H14N4O2S2 (Fig. 7a). The ion of m/z = 358
undergoes fragmentation to a stable peak at m/z = 224 by losing
C7H7N2O atoms (structure I) as shown in Scheme (1a). A breakdown
of the backbone of HL1 ligand gives the fragment (structure II) with
m/z = 77 by losing of C3H2N2OS2.
The mass spectrum fragmentation mode of ligand (HL3) shows the
exact mass of 328 corresponding to the formula C15H12N4OS2
(Fig. 7b). The ion of m/z = 328 undergoes fragmentation to a stable
peak at m/z = 224 by losing C6H5N2 atoms (structure I) as shown in
Scheme (1b). A breakdown of the backbone of HL3 ligand gives the frag-
ment (structure II) with m/z = 77 by losing of C3H2N2OS2.
The mass spectrum fragmentation mode of ligand (HL4) shows the
exact mass of 362.5 corresponding to the formula C15H11N4OS2Cl
(Fig. 7c). The ion of m/z = 362 undergoes fragmentation to a stable
peak at m/z = 224 by losing C6H4N2Cl atoms (structure I) as shown in
Scheme (1c). A breakdown of the backbone of HL4 ligand gives the
fragment (structure II) with m/z = 77 by losing of C3H2N2OS2.
3.5. X-ray diffraction analysis
The X-ray diffraction (XRD) patterns of HL1, HL3 and HL4 ligands and
complex (1) in powder forms are shown in Fig 6. The XRD patterns of
HL1, HL3 and HL4 ligands show many sharp diffraction peaks in addition
to a broad hump at 2θ = 8°. This behavior indicates that the powder is a
mixture of amorphous and polycrystalline nature. The XRD pattern of
complex (1) shows amorphous nature.
3.6. Mass spectra
3.7. Electronic spectra and magnetic measurements
The mass spectra of ligands (HL1, HL3 and HL4) are recorded and in-
vestigated at 70 eV of electron energy. It is obvious that, the molecular
ion peaks are in good agreement with their suggested empirical formula
as indicated from elemental analyses (Table 1). The mass spectrum
The electronic absorption spectra of the two ligands (HLn) exhibits
bands at 26,350–26,150 cm−1 (CS) (n → π*), 30,460–30,250 cm−1
(CO) (n → π*), 32,980–33,100 cm−1 (H-bonding and association),

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A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
40,240–39,890 cm−1 (phenyl) (ph-ph*, π–π*) [40] and 29,610–
29,350 cm−1 transition of phenyl rings overlapped by composite
broad π–π* of azo/CH=N structure. In the Co(II) complexes, the (CS
and CO) (n–π*) transition shifts to lower energy. These shifts or the
disappearance of the bands are indicative of coordination of the ligands
are indicative of coordination of the ligands to Co(II).
Based on magnetic moment values, the cobalt(II) compounds fall
into two classes. In the first, the so called ionic complexes are with μeff
Fig. 12. Horowitz–Metzger (HM) of ligands (HLn), stages (I, II).

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
729
Fig. 12 (continued).
values lying in the first range 4.3–5.6 B.M., while the second is with
much smaller values (1.7–2.9 B.M.) and are of covalent properties.
From such scope of representation, the first class of cobalt(II) com-
plexes. (i) may be associated with low spin octahedral field, while the
second class (ii) is of square planar environment around cobalt(II).
The spectra of our data exhibited bands located at 9200–2210 and
43,320–4400 cm−1. Such finding is a strong indicative of octahedral
spatial configuration. It is of interest to mention that the low magnetic
moments of Co(II) complexes (μeff. = 1.15–1.24 B.M./atom) could be
referred to occur through a ligand bridge as shown in Fig. 2. Another
reason for the lowering magnetic moments may be due to the admix-
ture of cobalt(II) and cobalt(III) ions in the same molecule.
(C6H6N2) (Found 30.0%, calc. 29.6%). The third stage in the temperature
range 570–800 °C corresponds to loss of a part of the ligand (OCH3)
(Found 8.0%, calc. 8.6%).
HL2 ligand shows three decomposition steps, the first stage that oc-
curs in the temperature range 30–265 °C is attributed to loss of
(C9H6N2S2O) (found 65.0% and calc. 64.9%). The second stage in the
temperature range 265–700 °C corresponds to loss of a part of the ligand
(C6H6N2) (found 30.0%, calc. 30.9%). The third stage in the temperature
range 700–800 °C corresponds to loss of a part of the ligand (CH3)
(Found 5.0%, calc. 4.3%).
HL3 ligand shows two decomposition steps, the first stage that
occurs in the temperature range 30–330 °C is attributed to loss of
(C9H6N2S2O) (found 68.0% and calc. 67.7%). The second stage in the
temperature range 330–800 °C corresponds to loss of a part of the ligand
(C6H5N2) (found 32.0%, calc. 32.3%).
3.8. Thermal analysis
HL4 ligand shows two decomposition steps, the first stage that
occurs in the temperature range 30–350 °C is attributed to Loss of
(C9H7N2S2OCl) (found 71.0% and calc. 71.3%). The second stage in the
temperature range 350–800 °C corresponds to loss of a part of the ligand
(C6H5N2) (found 29.0%, calc. 28.9%).
HL5 ligand shows three decomposition steps, the first stage that
occurs in the temperature range 30–400 °C is attributed to Loss of
(C9H6N2S2O) (found 59.0% and calc. 59.5%). The second stage in the
The TGA curves for the ligands (HLn) are shown in Fig. 8. It is clear
that the change of substituent affects the thermal properties of the
ligands. The temperature intervals and the percentage of loss of masses
are listed in Table 9.
HL1 ligand shows three decomposition steps, the first stage that
occurs in the temperature range 30–260 °C is attributed to loss of
C9H6N2S2O (found 62.0% and calc. 61.9%). The second stage in the tem-
perature range 260–570 °C corresponds to loss of a part of the ligand

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A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
temperature range 400–600 °C corresponds to loss of a part of the ligand
(C6H6N2) (found 28.0%, calc. 28.4%). The third stage in the temperature
range 700–800 °C corresponds to loss of a part of the ligand (NO2)
(found 13.0%, calc. 12.3%).
The TGA curves for Co(II) complexes (1–5) are shown in Fig. 9. The
temperature intervals and the percentage of loss of masses are listed
in Table 10. The TG curves of all Co (II) complexes (1–5) showed the
loss of C4H10O6 in the temperature range ~30–150 °C. The first stage is
Fig. 13. Horowitz–Metzger (HM) of Co(II) complexes (1–5), stages (I, II).

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
731
Fig. 13 (continued).
Table 11
Thermodynamic data of the thermal decomposition of ligands (HLn).
Parameter
Ea
Compound
Decomposition temperature (°C)
Method
R
⁎
⁎
⁎
ΔG
A
ΔS
ΔH
(kJ mol−1
)
(s−1
)
(J mol−1 K−1
)
(kJ mol−1
)
(kJ mol−1
)
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
45.8
53.6
180
193
46.9
48.4
162
173
329
338
108
120
70.9
80.8
102
114
31.2
39.2
108
119
7.58 × 101
4.18 × 102
4.43 × 108
6.40 × 109
7.11 × 101
1.17 × 102
2.34 × 107
2.50 × 108
2.54 × 1030
1.70 × 1032
1.51 × 104
2.05 × 105
5.53 × 105
1.40 × 107
1.31 × 106
2.10 × 107
3.31 × 100
3.59 × 101
1.59 × 104
5.78 × 104
−214
−200
−87.9
−65.8
−215
−210
−113
−92.2
333
41.2
49
159
159
247
241
161
160
250
245
151
142
242
236
131
129
181
179
152
150
254
255
0.99221
0.99398
0.99355
0.99169
0.99322
0.99788
0.98442
0.99156
0.99453
0.99452
0.99432
0.9939
0.99122
0.98595
0.99104
0.99064
0.99523
0.98744
0.98712
0.98669
211–346
498–624
158–401
502–643
225–271
443–630
142–240
301–418
127–372
496–715
HL1
HL2
HL3
HL4
HL5
174
186
42.3
43.8
155
166
325
333
101
113
67.1
76.9
96.5
108
26.9
34.9
101
112
367
−173
−152
−139
−112
−134
−111
−240
−220
−173
−163
HM
CR
HM
CR
HM

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A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
Table 12
Thermodynamic data of the thermal decomposition of Co(II) complexes (1–5).
Parameter
Ea
Compounda
Decomposition temperature (°C)
Method
R
⁎
⁎
⁎
ΔG
A
ΔS
ΔH
(kJ mol−1
)
(s−1
)
(J mol−1 k−1
)
(kJ mol−1
)
(kJ mol−1
)
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
10.6
19.4
722
734
11.4
21.7
691
726
14.8
25
412
430
6.76
18.6
744
740
8
6.31 × 103
5.36 × 102
2.20 × 1045
1.88 × 1046
6.47 × 103
9.87 × 102
4.44 × 1043
1.14 × 1046
1.43 × 102
2.14 × 101
6.11 × 1024
1.77 × 1026
1.35 × 103
3.95 × 102
8.17 × 1046
5.05 × 1046
2.51 × 103
3.83 × 102
1.50 × 1022
5.83 × 1022
−293
−275
615
5.59
14.4
715
727
6.41
16.8
684
719
9.81
20
406
423
1.70
13.5
738
734
3.01
13.1
360
371
181
179
223
221
181
177
221
220
181
178
229
224
188
182
221
221
183
180
223
225
0.96357
0.94125
0.97664
0.99571
0.9262
140–510
510–545
140–505
505–540
150–500
500–550
155–515
515–540
155–500
500–550
(1)
(2)
(3)
(4)
633
−293
−270
583
0.9493
0.98464
0.98183
0.9478
629
−286
−264
221
0.93629
0.99286
0.99395
0.92499
0.90661
0.98471
0.97099
0.9166
249
−306
−278
645
HM
CR
HM
CR
641
−301
−278
171
18.1
367
377
0.93422
0.92419
0.93396
(5)
HM
183
a
Numbers as given in Table 1.
related to loss of the part of the deprotonated ligand. The second stage is
related to loss of HLn. The final weight losses are due to the decomposi-
tion of metal oxides residue (Table 10).
3.8.1.2. Horowitz–Metzger equation. The Horowitz–Metzger equation is
an illustrative of the approximation methods. These authors derived
the relation:
3.8.1. Calculation of activation thermodynamic parameters
The thermodynamic activation parameters of decomposition
processes of the ligands HLn and their Co(II) complexes (1–5) namely
activation energy (Ea), enthalpy (ΔH*), entropy (ΔS*), and Gibbs free
energy change of the decomposition (ΔG*) are evaluated graphically
by employing the Coast–Redfern [41] and Horowitz–Metzger [42]
methods.
"
#
1−n
1−ð1−αÞ
1−n
Eaθ
2:303RT2s
log
¼
; for n≠1
ð13Þ
when n = 1, the LHS of Eq. (13) would be log[−log(1-α)] (Figs. 12 and
13). For a first order kinetic process, the Horowitz–Metzger equation
may write in the form:
3.8.1.1. Coast–Redfern equation. The Coast–Redfern equation, which is a
typical integral method, can represent as:
ꢄ
ꢂ
ꢃꢅ
Wα
Wγ
Eaθ
2:303RT2s
log log
¼
− log2:303
ð14Þ
ꢂ
ꢃ
Z
Z
α
T2
dx
ð1−αÞ
A
ϕ
Ea
RT
¼
exp
−
dt
ð10Þ
n
0
T1
where θ = T − Ts, wγ = wα − w, wα = mass loss at the completion
reaction; w = mass loss up to time t. The plot of log [log (wα/wγ)] vs.
θ was drawn and found to be linear from the slope of which Ea was cal-
culated. The pre-exponential factor, A, is calculated from equation:
For convenience of integration, the lower limit T1 is usually taken as
zero. This equation on integration gives
ꢄ
ꢅ
ꢄ
ꢅ
lnð1−αÞ
Ea
RT
AR
ϕEa
Ea
RT2s
A
ln −
¼ −
þ ln
ð11Þ
T2
ꢄ
ꢂ
ꢃꢅ
¼
ð15Þ
Ea
RTs
ϕ exp
−
A plot of left-hand side (LHS) against 1/T was drawn (Figs. 10 and
11). Ea is the energy of activation and calculated from the slope and A
⁎
The entropy of activation, ΔS , is calculated from Eq. (12). The en-
in (s−1) from the intercept value. The entropy of activation (ΔS ) in
⁎
⁎
⁎
thalpy activation, ΔH , and Gibbs free energy, ΔG , is calculated from:
(Jmol−1 K−1) is calculated by using the equation:
ΔHꢂ ¼ Ea−RT
ð16Þ
ð17Þ
ꢄ
ꢂ
ꢃꢅ
Ah
kBTs
ΔSꢂ ¼ 2:303 log
R
ð12Þ
ΔGꢂ ¼ ΔHꢂ−TΔSꢂ
⁎
⁎
⁎
The calculated values of Ea, A, ΔS , ΔH and ΔG for the decomposi-
tion steps for ligands (HLn) and cobalt(II) complexes (1–5) are summa-
rized in Tables 11 and 12.
Where kB is the Boltzmann constant, h is the Plank's constant and Ts
is the TG peak temperature.

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
733
Fig. 14. Absorption spectra of ligands (HLn) in buffer pH 7.2 at 25 °C in the presence of increasing amount of SS-DNA. Arrows indicate the changes in absorbance upon increasing the
SS-DNA concentration. Inset: plot of [DNA] / (εa − εf) M2 cm vs. [DNA] M for titration of DNA with ligands (HLn).
3.9. Stoichiometries of the cobalt(II) complexes
complexes reveal that three molecules of the ligand and two of the
anions are coordinated to the two metal atoms in all complexes.
The ligands present four donor sites: the azo nitrogen, the carbonyl
oxygen and the thionyl sulfur of rhodanine moiety and the NH
group of 3-phenylamino. However, it is clear that the utilization of
all the four bonding sites would introduce certain steric restrictions
and hence either both the azo nitrogen and the carbonyl group
Analytical data of the polymeric complexes (Table 1) were isolat-
ed in the general formulae [(Co)2(Ln)2(HLn)(CH3COO)2(OH2)2]n as
shown in Fig. 2. The 2:3 stoichiometries of the polymeric complexes
were calculated from their elemental analyses. The analytical
data and the molar conductance measurements of the polymeric

734
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
DNA interaction study by UV–Visible Spectroscopy Electronic ab-
sorption spectra was initially used to examine the interaction between
ligands (HLn) and SS-DNA. After interaction with increasing amount
of DNA, all the peaks decreased gradually and the wavelengths have
minor red shift of 1–2 nm. Long and Barton [43] had pointed out that
the absorption peaks shift of the small molecules after they interacted
with DNA could be as the clues to judge the binding mode between
the small molecules and DNA: If the binding involves a typical
intercalative mode, a hypochromism effect coupled with obvious
bathochromism for the characteristic peaks of the small molecules will
be found due to the strong stacking between the chromophore and
the base pairs of DNA [44]. Therefore, based on this viewpoint, the inter-
action between ligands (HLn) and SS-DNA could be noncovalent
intercalative binding. After intercalating the base pairs of DNA, the π*
orbital of the intercalated ligand could couple with π orbital of base
pairs, thus decreasing the π–π* transition energy, and further resulting
in the bathochromism. On the other hand, the coupling of a π orbital
with partially filled electrons decreases the transition probabilities
hence results hypochromic shift. Since hypochromism due to π–π*
stacking interactions may appear in the case of the intercalative binding
mode, while bathochromism (red-shift) may be observed when the
DNA duplex is stabilized [45,46].
Fig. 15. The relation between Hammett's substitution coefficients (σR) vs. intrinsic binding
constants (Kb) of the ligands (HLn).
would coordinate or the NH group and the carbonyl group
would coordinate. The coordination of NH group and carbonyl
group seems unlikely in view of the large size of the chelated ring.
Polymeric complexes do not have a sharp melting point and decom-
pose at higher temperature.
The intrinsic binding constants (Kb) of all the ligands (HLn) with
SS-DNA were determined (Eq. 1) [47]. The Kb values obtained from
the absorption spectral technique for ligands (HL1−HL5) were calculat-
ed as 2.63 × 105, 3.15 × 105, 4.64 × 105, 5.1 × 105 and 7.35 × 105 M−1
,
respectively. The values of binding constant are related to the nature of
the p-substituent as they increase according to the following order
p-(NO2 N Cl N H N CH3 N OCH3). This can be attributed to the fact that
the effective charge increased due to the electron withdrawing p-
substituent (HL4 and HL5) while it decreased by the electrons donating
character of (HL1 and HL2). This is in accordance with that expected
from Hammett's constant (σR) as shown in Fig. 15, correlate the binding
constant values with σR it is clear that all these values increase with
increasing σR.
3.10. DNA binding studies
3.10.1. Electronic absorption measurements
Absorption titration is one of the most universally employed
methods to study the binding modes and binding extent of compounds
to DNA. Absorption titration experiments were performed with fixed
concentrations of the ligands (HLn) (30 μM) while gradually increasing
the concentration of DNA (10 mM) at 25 °C. While measuring the
absorption spectra, an equal amount of DNA was added to both the
compound solution and the reference solution to eliminate the absor-
bance of DNA itself. We have determined the intrinsic binding constant
to SS-DNA by monitoring the absorption intensity of the charge transfer
spectral bands near 470, 455, 437, 480 and 540 nm for the ligands
(HL1−HL5), respectively. The absorption spectra of these ligands with
increasing concentration of SS-DNA in the range 300–700 nm are
shown in Fig. 14.
3.11. Cytotoxic activity
The synthesized ligands (HLn) and their Co(II) complexes (1–5)
have been evaluated for in vitro cytotoxic activity against two human
cancer cell lines; HePG-2 (Hepatocellular carcinoma) and MCF-7 (breast
cancer). Inhibitory activity against HePG-2 and MCF-7 cell lines was de-
tected by using different concentrations (i.e., 50, 25, 12.5, 6.25, 3.125,
1.56, and 0 μg) of the tested compounds and viability cells (%) were de-
termined by the colorimetric method, data presented in Table 13. Also,
Table 13
Evaluation of cytotoxicity of ligands (HLn) and their Co(II) complexes (1–5) against HePG-2 and MCF-7 cells.
Compound
cell lines
HePG-2
Sample conc.
5-FU
HL1
8.3
HL2
7.9
HL3
7.5
HL4
7.6
HL5
13.1
(1)
30.4
(2)
13.4
(3)
51.2
(4)
31.9
(5)
30.4
100 μg/ml
50 μg/ml
25 μg/ml
12.5 μg/ml
6.25 μg/ml
3.125 μg/ml
1.56 μg/ml
0 μg/ml
8.6
17.1
24.0
33.1
56.8
70.6
88.7
100
15.6
21.9
36.7
55.4
74.3
92.6
15.6
24.3
38.4
56.7
78.1
95.5
14.2
20.8
34.6
47.1
58.3
76.4
14.3
22.0
35.3
54.7
73.5
90.5
18.8
26.4
37.2
67.5
75.9
96.9
42.8
53.9
66.2
87.5
99.1
100
100
48.1
60.0
72.8
85.3
98.2
22.1
31.8
45.6
63.7
83.5
100
100
44.0
56.2
67.3
79.1
95.4
65.9
79.3
93.7
42.8
55.7
68.3
89.5
100
100
100
42.0
53.7
65.3
78.5
98.4
100
100
39.6
100
100
100
100
58.6
77.3
94.1
100
100
100
100
100
MCF-7
100 μg/ml
50 μg/ml
25 μg/ml
12.5 μg/ml
6.25 μg/ml
3.125 μg/ml
1.56 μg/ml
0 μg/ml
5.8
24.0
30.8
42.7
54.9
69.3
88.1
34.6
46.5
59.2
68.4
83.3
98.5
7.9
13.4
20.0
31.5
50.3
61.7
74.6
20.1
27.2
39.5
51.3
72.8
93.4
28.3
39.1
52.0
63.7
77.2
96.3
50.8
10.3
16.2
28.5
48.4
62.8
81.6
100
64.5
76.2
92.3
54.7
70.3
91.2
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
735
inhibitory concentration 50 (IC50) was calculated from Fig. 16 and
Table 13. The results clearly revealed that most of the compounds pos-
sessed cytotoxic activity as evidenced by the IC50 values, as reported
in Table 14. The results revealed that some tested compounds have
cytotoxic activity against the hepatocellular carcinoma (HePG-2) and
mammary gland breast cancer (MCF-7) cell lines with superiority of
HL3 (IC50 = 5.4 μg/mL and 5.6 μg/mL, respectively). All ligands HLn ex-
hibit highly significant cytotoxic activity against HePG-2 cell line.
Fig. 16. Cytotoxic and antitumor activity of ligands (HLn) and their Co(II) complexes (1–5) against HePG-2 and MCF-7 cells.

736
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
Fig. 16 (continued).
Among all the ligands tested against MCF-7 cell line HL3 is exhibiting
very good cytotoxic activity, but ligands HL1, HL2, HL4 and HL5 are
exhibiting good to moderate cytotoxic activity as shown in Table 14.
All cobalt(II) complexes are exhibiting moderate to weak cytotoxic or
non-cytotoxic activity. Apparently, complexation reduces the cytotoxic
activity of ligands. Comparing results with 5-fluorouracil (5-FU)

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
737
Table 14
Table 16
Inhibition of cell viability of ligands (HLn) and their Co(II) complexes (1–5) against HePG-
2 and MCF-7 cells in comparison with standard drug 5-fluorouracil.
Antibacterial and antifungal activities data of ligands (HLn) and their Co(II) complexes
(1–5).
Cell lines [IC50 (μg/mL)]
Compound
(mg/ml)
E. coli
S. aureus
C. albicans
Compound
HePG-2
MCF-7
Diameter of
inhibition
zone (mm) index
%
Diameter of
activity inhibition
%
Diameter of
activity inhibition
%
activity
5-FU
HL1
HL2
HL3
HL4
HL5
(1)
(2)
(3)
(4)
(5)
7.9 0.24
8.3 0.47
9.0 0.68
5.4 0.31
7.9 0.38
10.3 0.97
34.8 3.15
12.4 1.04
96.5 6.35
37.1 2.98
32.9 2.32
5.6 0.13
19.4 1.27
41.5 3.41
5.6 0.21
17.6 1.10
29.5 1.29
81.6 4.87
67.0 4.11
N100
zone (mm) index
zone (mm) index
HL1
HL2
HL3
HL4
HL5
(1)
(2)
(3)
9
3
20
14
6
–
–
–
–
37.5
12.5
83.3
58.3
25.0
–
–
–
–
14
7
16
17
10
3
4
–
2
63.6
31.8
72.7
77.3
45.4
13.6
18.2
–
17
6
25
21
14
–
–
–
–
65.4
23.1
96.1
80.8
53.8
–
–
–
–
93.5 6.37
62.7 4.12
(4)
9.1
(5)
3
24
–
12.5
100
–
5
22
–
22.7
100
–
–
–
26
–
–
100
Data presented as mean SD. IC50 (μg/ml): 1–10 (very strong). 11–20 (strong). 21–50
(moderate). 51–100 (weak) and above 100 (non-cytotoxic). All the compounds and the
standard dissolved in DMSO, diluted with culture medium containing 0.1% DMSO. The
control cells were treated with culture medium containing 0.1% DMSO.
Ampicillin
Colitrimazole
response indicated that HL3 have higher cytotoxic activity than 5-FU.
The other compounds also showed cytotoxic activity but at higher IC50
values. The results indicated the importance of different heterocyclic
rhodanine derivatives in enhancing the cytotoxic activity.
Co(II) complex of HL3 represented a lower antioxidant activity com-
pared to its un-complexed compound. In accordance with the cytotox-
icity testing results, the complexation decreases the biological activity
of the synthesized compound.
3.12. Antioxidant activity
3.13. Antimicrobial activity
Oxygen is vital for aerobic life process. However about 5% or more of
the inhaled O2 is converted to reactive oxygen species (ROS). A free rad-
ical (FR) can be defined as a chemical species possessing an unpaired
electron. FR can be positively charged, negatively charged or electrically
neutral [48]. When generation of ROS overtakes the antioxidant defense
of the cells, the free radicals start attacking the cell proteins, lipids and
carbohydrates which leads to a number of physiological disorders
[49]. Free radicals have been implicated in the pathogenesis of diabetes,
liver damage, nephrotoxicity, inflammation, cancer, cardiovascular dis-
orders, neurological disorders and in the process of aging [50].
Antioxidants are chemical substances that donate an electron to the
free radical and convert it to a harmless molecule. They may reduce the
energy of the free radical or suppress radical formation or break chain
propagation or repair damage and reconstitute membranes.
Table 15 expressed results of radical scavenging ability and percent-
age of inhibition of each ligands (HLn), their Co(II) complexes (1–5) and
standard ascorbic acid, as a reference compound by ABTS method. The
results showed that all ligands have high antioxidant activity and have
asymptotic effect of ascorbic acid. HL3 presented the better activity
among all other compounds and when compared with ascorbic acid.
There are poor antioxidant activity for Co(II) complexes (1–5). The
The antimicrobial activity of ligands (HLn) and their Co(II) com-
plexes (1–5) were tested against bacteria and fungi (yeast) for detecting
their antimicrobial activities [9,51,52]. The used organisms in the pres-
ent investigations included Gram negative (E. coli) bacteria, Gram posi-
tive (Staphylococcus aureus) and yeast (Candida albicans). The results of
the antibacterial activities of the synthesized compounds are recorded
in Table 16. All HLn were found to have antibacterial activity against
Gram negative bacteria; namely; E. coli (inhibition zone =9 mm with
activity index 37.5% for HL1, inhibition zone =3 mm with activity
index 12.5% for HL2, inhibition zone = 20 mm with activity index
83.3% for HL3, inhibition zone = 14 mm with activity index 58.3% for
HL4 and inhibition zone = 6 mm with activity index 25% for HL5).
Only complex (5) has antibacterial activity against Gram negative
bacteria; namely; E. coli (inhibition zone =3 mm with activity index
12.5%).
All compounds under investigation have antibacterial activity
against Gram positive bacteria; namely S. aureus (inhibition zone =
14 mm with activity index 63.6% for HL1, inhibition zone = 7 mm
with activity index 31.8% for HL2, inhibition zone = 16 mm with activity
index 72.7% for HL3, inhibition zone = 17 mm with activity index 77.3%
for HL4, inhibition zone = 10 mm with activity index 45.4% for HL5, in-
hibition zone = 3 mm with activity index 13.6% for complex (1), inhibi-
tion zone = 4 mm with activity index 18.2% for complex (2), inhibition
zone = 2 mm with activity index 9.1% for complex (4) and inhibition
zone = 5 mm with activity index 22.7% for complex (5)) while complex
(3) has no activity. Only ligands HLn have antifungal activity against
C. albicans (inhibition zone = 17 mm with activity index 65.4% for
HL1, inhibition zone = 6 mm with activity index 23.1% for HL2, inhibi-
tion zone = 25 mm with activity index 96.1% for HL3, inhibition
zone = 21 mm with activity index 80.8% for HL4 and inhibition
zone = 14 mm with activity index 53.8% for HL5). HLn were found to
have high antibacterial and antifungal activities than their complexes
(Fig. 17). HL3 was found to have high antibacterial activity against
E. coli (Fig. 17a) and antifungal activity against C. albicans (Fig. 18)
more than the other ligands. HL4 was found to have high antibacterial
activity against S. aureus as shown in Fig. 17(b) more than other ligands.
HL3 and HL4 are good antibacterial and antifungal agents.
Table 15
Results of radical scavenging activity and % of inhibition of each ligands (HLn) and their
Co(II) complexes (1–5) by ABTS method.
Compounds
Absorbance
% inhibition
Control of ABTS
Ascorbic-acid
0.520
0.057
0.070
0.082
0.055
0.068
0.079
0.332
0.296
0.424
0.339
0.283
0
89.0
86.5
84.2
89.4
86.9
84.8
36.1
43.1
18.5
34.8
45.6
HL1
HL2
HL3
HL4
HL5
(1)
(2)
(3)
(4)
(5)

738
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
Fig. 17. Antibacterial activity data of ligands (HLn) and their Co(II) complexes against (a) Escherichia coli and (b) Staphylococcus aureus.
4. Conclusion
bonding sites are 3-NH, CS, CO and hydrazo groups. The XRD patterns
of ligands indicate that the powder is a mixture of amorphous and
polycrystals nature. The polymeric complexes exhibit amorphous na-
ture. The interaction between ligands (HLn) and SS-DNA involves a
hypochromism effect coupled with bathochromism. There are straight
line relationships between energy gap (ΔE) and the SS-DNA binding
activity (Kb) of the ligands with Hammett's p-substitution coefficients
(σR). It is clear that that the values of energy gap (ΔE) and the SS-
The IR, 1H-NMR spectra show that ligands (HLn) exist in tauto-
meric between both states enol/hydrazo form with intramolecular
hydrogen bonding. The ligands coordinate to cobalt(II) as monobasic
tetradentate. The cobalt(II) complexes are non-electrolytes, paramag-
netic and six-coordinated octahedral polymeric complexes of struc-
ture [(Co)2(Ln)2(HLn)(CH3COO)2(H2O)2]n. It is clear that, the four
Fig. 18. Antifungal activity data of ligands (HLn) and their Co(II) complexes against Candida albicans.

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 215 (2016) 711–739
739
DNA binding activity (Kb) increase with increasing σR. Rhodanine de-
rivatives have been evaluated to have biological and pharmacological
activities. HL3 has the highest cytotoxic, antioxidant and antimicrobial
activities.
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