Hartree-Fock, molecular docking, spectral, kinetic and antitumor considerations for cobalt, nickel, palladium and platinum (II)-bis carbothiohydrazide complexes

Article abstract of DOI:10.1016/j.molliq.2016.04.083

New metal ion complexes were synthesized using Schiff base derivative and characterized using spectral and theoretical analysis. IR and 1H NMR spectra, suggest bi-dentate to tetra-dentate mode of bonding each towards two metal ions. Square-planar and octa

Full text of DOI:10.1016/j.molliq.2016.04.083

Journal of Molecular Liquids 220 (2016) 265–276
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
Hartree-Fock, molecular docking, spectral, kinetic and antitumor
considerations for cobalt, nickel, palladium and platinum (II)-bis
carbothiohydrazide complexes
b
Nashwa M. El-Metwaly a, , Marwa G. El-Ghalban
⁎
a
Chemistry Department, College of Applied Sciences, Umm Al-Qura University, Makah, Saudi Arabia
b
Chemistry Department, Faculty of Science, Mansoura University, Mansoura, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
New metal ion complexes were synthesized using Schiff base derivative and characterized using spectral and the-
oretical analysis. IR and 1H NMR spectra, suggest bi-dentate to tetra-dentate mode of bonding each towards two
metal ions. Square-planar and octahedral configurations are the two proposed geometries for Pd(II) or Pt(II) and
Co(II) or Ni(II) complexes, respectively. Significant spectral parameters were calculated to emphasis on the type
of bonds between active sites and the metal atoms. XRD patterns and TEM images stressed on the nanometer
sized appearance for all investigated compounds. Theoretical considerations were implemented using Gauss-
ian09 and Autodock computational tools. HF/LANL2DZ molecular modeling exerts the optimized structures
which agree with the spectral data. The frontier molecular orbitals, HOMO and LUMO were calculated. Also,
the calculated geometric parameters foresee the distinguish bioactive features of all compounds under interest.
Molecular docking utilizes defiant protein receptors attributed to the microorganisms executed in biological
application as; 3t88, 3ty7, 3cku, 2ylh and 2jrs. Considerable reduction in binding energies was recorded along
the docking process. The docked Schiff base ligand displays significant energy data with hepatocellular carcinoma
(2jrs) and Escherichia coli (3t88) receptors. This deducts the affinity of designed drug against the two infections.
The antibacterial and antifungal activities were tested against different microorganisms. The scanned compounds
display a comparable inhibition activity along the investigation process. IC50 was determined for all compounds
against hepatocellular carcinoma cells. Co(II) and Ni(II) complexes are introducing an excellent activity towards
the inhibition of all microorganisms and also offer the best IC50 values in carcinoma cell line investigation.
© 2016 Elsevier B.V. All rights reserved.
Received 31 January 2016
Received in revised form 16 April 2016
Accepted 18 April 2016
Available online xxxx
Keywords:
Schiff base
Hartree-Fock
Molecular docking
Spectral
TEM
Antitumor
1. Introduction
N2O2 donors [7,8]. In continuation for previous work [9–15], here
in our study we are dealing with bis derivative for thiocarbohdrazide
In the last few decades the Schiff base ligands include NSO do-
nors have attracted the researcher insight to intensify the research
dealing with such chelating compounds. Schiff base metal ion com-
plexes are taken a great attention due to their enormous application
in different areas based on the role of metal ion in enhancement the
activity at all. Antitumor, antiaprotozoal and antibacterial activates
are recorded with different thiosemicarbazone complexes [1–4]. A
series of salicylaldehyde thiosemicarbazone complexes have been
synthesized using Pd(II), Cu(II) and Ru(III) ions. The complexes iso-
lated have 1:1 and 1:2 (M:L) molar ratios [5]. Also, vanadium com-
plex was prepared from salicylaldehyde thiosemicarbazone and
tri-dentate mode of bonding was proposed through ONS donors
[6]. Generally, the divalent metal ion complexes have been used
for the complexation towards diprotic Schiff base ligands with
with salicylaldehyde. The bis derivative includes multi-donor centers
which enriches the coordination towards bivalent cobalt and nickel
group metals. The spectral, thermal and kinetic studies will be used to
establish the structural formula of the complexes. Gaussian09 molecu-
lar modeling and Autodock molecular docking will be elaborately im-
plemented to serve the chemical and biological investigations.
2. Experimental
2.1. Reagents
The chemicals concerned in this study to prepare the Schiff base
ligand are, thiocarbohydrazide and salicyladehyde were purchased
from Fulka and employed as it is. Also, the metal chloride salts used
for complexation as; CoCl2(H2O)6, NiCl2(H2O)6, PdCl2 and, PtCl2 are
commercially available from Sigma-Aldrich. The solvents used in syn-
thesis process are utilized without previous purification.
⁎
Corresponding author.
E-mail address: n_elmetwaly00@yahoo.com (N.M. El-Metwaly).
http://dx.doi.org/10.1016/j.molliq.2016.04.083
0167-7322/© 2016 Elsevier B.V. All rights reserved.

266
N.M. El-Metwaly, M.G. El-Ghalban / Journal of Molecular Liquids 220 (2016) 265–276
Scheme 1. Synthesis of N′,2-bis((E)-2-hydroxybenzylidene) hydrazine-1-carbothiohydrazide.
2.2. Synthesis
few drops of tri-ethylamine to accelerate the reaction which sometimes
distinguish cobalt complexation. Equi-molar ratios (1:1) were mixed
from Schiff base ligand to each metal salt. 0.3144 g (1 mmol) of ligand
dissolved in ethanol, was added drop wisely to metal chloride solution at-
tributed to, CoCl2(H2O)6(0.238 g); NiCl2(H2O)6(0.238 g); PdCl2(0.177 g)
and PtCl2(0.266 g). The mixtures refluxed for 3–4 h, the precipitates
were filtered off washed with ethanol, diethyl ether and finally dried in
a vacuum desiccator.
2.2.1. Synthesis of N′,2-bis((E)-2-hydroxybenzylidene) hydrazine-1-
carbothiohydrazide (H3L)
In a round bottom flask, 1:2 M ratio from thiocarbohydrazide
(5 mmol, 0.50 g) to salicyldehyde (10 mmol, 1.722 g) is condensed in
ethanolic solution (40 mL) (Scheme 1). The mixture was refluxed for
≈3 h, allowed to cool down. The yellow precipitate Schiff base product
was collected by filtration, washed with ether and re-crystallized in etha-
nol by a suitable yield (65%). The elemental analyses are; C; 57.36 (calcd.
57.30%), H; 4.48(calcd. 4.49%) and N; 18.83 (calcd. 17.82%). The structural
formula of the ligand (C15H14N4O2S) was verified by spectral analysis.
2.3. Biological activity
2.3.1. Anti-microorganisms activity
The compounds under investigation were tested individually against
bacteria, Escherichia coli (G−) and Staphlococcus aureus (G+) and
fungi as; Aspergillus fumigatus and canadida albicans. The biological
investigation was implemented using agar well diffusion methods
2.2.2. Synthesis of metal ion complexes
The synthesis process were carried out (Scheme 2) at the same condi-
tions except the Co(II) complex. The precipitation of Co(II) complex needs
Scheme 2. The synthesis process of complexes.
Table 1
Analytical and physical data of H3L Schiff base ligand and its metal complexes.
Compound empirical formula (Calcd)
Color
Elemental analysis (%) Calcd/Found
C
H
N
M
Cl
1) [C15H14N4O2S] (314.35)
Yellow
Brown
Dark green
Orange
Brownish yellow
57.30/57.36
38.98/38.99
37.54/37.8
35.35/35.40
30.11/30.13
4.49/4.48
3.49/3.52
3.78/3.77
3.16/3.20
2.69/2.67
17.82/17.83
12.12/12.14
11.67/11.64
10.99/11.10
9.36/9.40
–
2) [Co(Cl)2(C15H14N4O2S)](H2O)(462.21)
3) [Ni(Cl)2(C15H14N4O2S)](H2O)2(479.97)
4) [Pd(Cl)2(C15H14N4O2S)](H2O)(509.69)
5) [Pt(Cl)2(C15H14N4O2S)](H2O)(598.34)
12.75/12.80
12.23/12.22
20.88/20.87
32.60/32.61
15.34/15.44
14.77/14.55
13.91/13.92
11.85/11.88

N.M. El-Metwaly, M.G. El-Ghalban / Journal of Molecular Liquids 220 (2016) 265–276
267
Table 2
Assignments of the IR spectral bands (cm−1) of H3L Schiff base and its metal complexes.
Compound
νOH
δOH
δNH
νCN
δr(H2O), δw(H2O)
νC–O
νCS(IV)
νM–O
νM–N
1) [C15H14N4O2S]
3336
3555
3415
3424
3443
1399
1380
1349
1392
1399
1539
1535
1543
1536
1539
1595
1535
1581
1580
1578
–
1034
1027
1036
1038
1034
820
828
817
820
820
–
–
2) [Co(Cl)2(C15H14N4O2S)](H2O)
3) [Ni(Cl)2(C15H14N4O2S)](H2O)2
4) [Pd(Cl)2(C15H14N4O2S)](H2O)
5) [Pt(Cl)2(C15H14N4O2S)](H2O)
850,650
856, 670
856,645
850,660
533
537
–
425
464
460
421
–
Fig. 1. The structural and optimized form of N′,2-bis((E)-2-hydroxybenzylidene) hydrazine-1-carbothiohydrazide (H3L) ligand.
[16], pathological bacteria (1 × 106 CFU/mL) and (1 × 104 spore/mL)
2.4. Equipments
fungi were spread over nutrient agar (NA), Sab-dextrose agar and
(SDA), respectively. After cooling the media will be solidified,
100 μl from tested compound were spread over 6 mm diameter.
The solution was prepared by dissolving 20 mg of the compound
in DMSO solvent. The plates were then impregnated for 24 h, 37 °C
and 48 h, 28 °C for bacteria and fungi, respectively. The control
was prepared using DMSO solvent employed in investigation. Ampi-
cillin (50 μg/mL), and Amphotericin B (50 μg/mL) were utilized as
referenced bacteria and fungi, respectively. After impregnation, the
activity was evaluated by measuring the inhibition zone in compar-
ing with the reference as millimeters expressing the mean values for
triplicate.
Carbon, H and N were analyzed at the Microanalytical unit of Cairo
University. The metal and chloride contents were determined using
slandered methods [20]. The molar conductivities of freshly prepared
1.0 × 10−3 mol/cm3 DMSO solutions were measured for the soluble
complexes using Jenway 4010 conductivity meter. The X-ray diffraction
patterns (XRD) were obtained on Pikagu diffractometer using CuKα ra-
diation. Transmittance electron microscopy (TEM) images were taken
in Joel JSM-6390 equipment. The infrared spectra, as KBr discs, were re-
corded on JASCO FT-IR-4100 Spectrophotometer (400–4000 cm−1).
The electronic and 1H NMR (200 MHz) spectra were recorded on UV2
Unicam UV/Vis, and a Varian Gemini Spectrophotometers. The effective
magnetic moments were evaluated at room temperature by applying
pffiffiffiffiffiffiffiffiffi
μeff ¼ 2:828 XMT, where XM is the molar susceptibility corrected using
2.3.2. Antitumor activity
Pascal's constants for the diamagnetism of all atoms in the ligand using
a Johnson Matthey magnetic susceptibility balance. The thermal analysis
was carried out on a Shimadzu thermogravimetric analyzer at a heating
rate of 10 °C min−1 under nitrogen (20–900 °C range). The biological
activity was evaluated at the Regional center for Mycology and biotech-
nology, Al-Azhar University, Cairo, Egypt.
The cell lines were obtained from the American type culture collection
(ATCC, Rockville, MD). The cells were grown on RPMI-1640 medium sup-
plemented with 10% inactivated fetal calf serum and 50 μg/L gentamycin.
The cells were maintained at 37 °C in humidified atmosphere with 5% CO2
and were sub-cultured two to three times a week. Briefly, the cell lines
were grown as mono layers in growth mediums. The minelayers of
10.000 cells adhered at the bottom of the wells in a 96-wellmicrotiter
plate (Falcon, NJ, USA) promoted for 24 h at 37 °C in a humidified incuba-
tor with 5% CO2. The monolayer were then washed with sterile phosphate
buffered saline(0.01 M pH 7.2)and simultaneously the cells were treated
with 100 μL from different dilutions of tested compounds in fresh mainte-
nance medium and incubated at 37 °C. A control of untreated cells was
made in the absence of the tested compounds. Three wells were used
from each concentration for tested samples. Every 24 h the observation
under inverted microscope was made. The number of the surviving
cells was determined by staining the cells with crystal violet followed
by cell lysing using 33% glacial acetic acid and read the absorbance at
590 nm using ELISA reader after well mixing. The absorbance values
from untreated cells were considered as 100% proliferation and the
percentage of availability was calculated as (1 − (ODT / ODC) ∗ 100%
where ODt is the mean optical density of the wells treated with
the tested compounds and ODc is the mean optical density of un-
treated cells [17–19].
2.5. Theoretical calculations
2.5.1. Kinetic studies
The kinetic parameters assigned to thermal analysis were calculated.
The order (n) and the energy of activation (E) of suitable decomposition
stages were determined for TG curves. Formerly, different researchers
Table 3
1H NMR data for the ligand and some of its complexes.
δ (ppm)
H3L
Pd(II)-H3L
Pt(II)-H3L
M, 8H, Ph
7.88–7.95
7.59 and 7.62
12.05
7.1–8.21
9.14 and 9.16
12.06
7.23–7.61
7.88 and 7.95
12
S, 2H, 2CHN
S, 2H, 2OH
DMSO + H2O
S, 2H, 2NH
3.3
3.85
3.66
2.5
2.49
2.5

268
N.M. El-Metwaly, M.G. El-Ghalban / Journal of Molecular Liquids 220 (2016) 265–276
Table 4
The spectroscopic, covalence parameters and magnetic moments of complexes.
2, 3
4, 5
υ
υ
2 (cm−1
1 (cm−1
)
)
*ε 2
*ε 1
105⁎⁎ʄ2
105⁎⁎ʄ1
υ
υ
3 (cm−1
2 (cm−1
)
)
ε 3
ε 2
105ʄ3
105ʄ2
ʄ3/ʄ2
ʄ2/ʄ1
μ
eff (BM)
10Dq
B (cm−1
)
β
Z
2)
3)
4)
5)
16,666
16,600
20,000
19,048
110
108
130
90
1818
18,518
25,600
22,727
22,222
101
91
280
70
1794.5
8694
1288
3980
0.99
0.97
0.94
0.96
4.14
2.43
0
8735
11,218
794.1
560.9
0.818
0.539
+1.103
−0.256
8942.4
1375.4
4140
0
−9
*Molar absorptivity, **Oscillator strengths, ʄ, calculated using the following expression: ʄ = 4.6 × 10
ε
max
υ1/2, where, εmax is the molar absorptivity of the band maximum and υ1/2 is the
band width at half-height expressed in wave numbers: C. J. Ballahusen, Prog. Inorg. Chem. 2.251(1960).
[21–29] were established equations and discussing their advantages.
The rate of decomposition is the product of two separate functions of
temperature and conversion using:
2.5.3. Molecular docking
Docking calculations using Gasteiger partial charges added to the
ligand (designed drug) atoms, were carried out using Autodock tools
4.2. Non-polar hydrogen atoms were conjoined, and rotatable bonds
were illustrated. The calculations were performed on the ligand-protein
pattern. Auto Dock tools were implemented after the addition of; funda-
mental hydrogen atoms, Kollman united atom type charges and salva-
tion parameters [32]. Affinity (grid) maps of ×× Å grid points and
0.375 Å spacing were created applying the Autogrid program [33].
Calculating Vander Waals and the electrostatic terms were carried out
using Auto Dock parameter set- and distance-dependent dielectric
functions, respectively. Docking simulations were executed using the
Solis & Wets local search method and the Lamarckian genetic algorithm
(LGA) [34]. Initial position, orientation, and torsions of the ligand mole-
cules were set indiscriminately. All rotatable torsions were emitted dur-
ing docking. Each docking experiment was derived from 10 different
runs that were set to close after a maximum of 250,000 energy assess-
ments. The population size was set to 150. During the search, a transla-
tional step of 0.2 Å, and quaternion and torsion steps of 5 were applied.
dα
dt
¼ kðTÞfðαÞ
ð1Þ
where, α is the fraction decomposed at time t, k(T) is the temperature
dependent function and f(α) is the conversion function. The rate con-
stant and dependent function k(T) is of Arrhenius type.
ꢀ
K ¼ Ae‐E =RT
ð2Þ
where R, is the gas constant in (J mol−1 k−1) substituting Eq. (2) into
Eq. (1) we get this equation
ꢀ
ꢁ
dα
dT
A
¼
fðαÞ
ð3Þ
φ e‐Eꢀ=RT
where φ, is the linear heating rate (dT/dt). From the integration and
approximation, this equation can be obtained in the following form:
3. Results and discussion
3.1. General
ꢂ
ꢃ
–Eꢀ
AR
φEꢀ
lngðαÞ ¼
þ ln
ð4Þ
RT
The basic analytical and physical data for Schiff base ligand and its
Co(II), Ni(II), Pd(II) and Pt(II) complexes are tabulated (Table 1). All
the investigated complexes are stable in air, having high melting points,
insoluble in all organic solvents except DMSO and DMF are completely
soluble. 1:1 (M:L) molar ratio is the general formula proposed for all
investigated complexes. The molar conductivity measurements for
1 mmol/L in DMSO solvent represent 6.5–12.1 Ω−1 cm2 mol−1 values.
where g(α) is a function depending on the mechanism of the reaction.
The right hand side is known as temperature integral and has no close
for solution. So, several techniques have been used to evaluate the
temperature integral. The kinetic parameters for the ligand and its com-
plexes are evaluated using Coat-Redfern [23] and Horowitz-Metzger
methods [28].
Table 6
2.5.2. Modeling methodology
Thermogravimetric analysis data for investigated compounds.
The geometry of Schiff base ligand and its complexes are fully
optimized by Hartree-Fock (HF) method with LANL2DZ base set using
Gaussian09 software [30]. Gaussian output files were visualized by
means of Gauss-View molecular visualization program [31]. In gas
phase, according to the numbering scheme given in the view of the
compounds, HF/quantum chemical parameters of the compounds are
calculated from HOMO–LUMO energies. Also, bond lengths and effec-
tive charges for coordinating groups in optimized structures will be
deducted.
Complex Steps
Temp.
range/°C
Decomposed
Weight
loss/Found
(Calcd. %)
(1)
(2)
(3)
1st
2nd
3rd
Residue
1st
2nd
3rd
Residue
1st
43.69–310
310–426.3 –(C7H5SO)
426.3–550
–CH2N2
13.41 (13.37)
44.02 (43.74)
27.34 (27.71)
15.23 (15.28)
3.73 (3.89)
43.70 (43.72)
32.59 (32.72)
19.98 (19.67)
30.66 (31.04)
37.1 (37.33)
19.67 (19.40)
12.57 (12.23)
41.05 (40.88)
38.11 (37.98)
20.88 (21.14)
–(C3H7N2O)
4C
47.5–175.9 –H2O
176.9–400
400.1–600
–Cl2 + (C8H7N2)
–(C7H7N2S)
CoO2
42.6–283
283–350.1 –(C8H7N2OS)
350.1–570
–2H2O + CH2N2 + Cl2
Table 5
2nd
3rd
XRD spectral data of H3L ligand and its complexes.
–(C6H5O)
Ni
Residue
1st
2nd
Residue
1st
Compound
Size (nm)
θ
Intensity
d-Spacing (Å)
FWHM
(4)
(5)
24.1–420.1 –H2O + C7H6NO + Cl2
420.1–750.2 –(C8H7N2O)
H3L
3.69
3.09
3.77
3.24
13.79
7.4
8.51
13.08
13.48
7.44
1000
1010
1050
850
5.979
5.208
3.405
3.304
6.325
0.396
0.474
0.395
0.460
0.106
Co(II)-H3L
Ni(II)-H3L
Pd(II)-H3L
Pt(II)-H3L
Pd
21.6–296.5 –(C10H13N3O2) + H2O + Cl2 48.97 (49.49)
296.6–579
2nd
Residue
–(HCNS)
Pt + 4C
9.83 (9.88)
41.20 (40.63)
1000

N.M. El-Metwaly, M.G. El-Ghalban / Journal of Molecular Liquids 220 (2016) 265–276
269
Table 7
Kinetic parameters using Coats–Red fern (CR) and Horowitz–Metzger (HM) operated for H3L ligands and its complexes.
Comp.
Step
Method
Kinetic parameters
E (J mol−1
)
A (S−1
)
ΔS (J mol−1 K−1
)
ΔH (J mol−1
)
ΔG (J mol−1
)
r
(1)
(2)
(3)
(4)
(5)
2nd
3rd
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
1.39E + 05
1.56E + 05
1.15E + 05
1.30E + 05
7.85E + 04
9.53E + 04
9.45E + 04
1.30E + 05
1.31E + 05
1.58E + 05
8.94E − 02
1.53E + 11
1.29E − 02
1.91E + 06
2.06E − 02
1.22E + 06
5.00E − 03
8.15E + 05
3.98E − 02
6.85E + 10
−2.71E + 02
−3.69E + 01
−2.89E + 02
−1.33E + 02
−2.83E + 02
−1.34E + 02
−2.98E + 02
−1.40E + 02
−2.78E + 02
−4.39E + 01
1.33E + 05
1.51E + 05
1.09E + 05
1.23E + 05
7.35E + 04
9.03E + 04
8.75E + 04
1.23E + 05
1.25E + 05
1.53E + 05
3.03E + 05
1.74E + 05
3.40E + 05
2.29E + 05
2.45E + 05
1.72E + 05
3.36E + 05
2.40E + 05
3.05E + 05
1.81E + 05
0.9993
0.9991
0.9993
0.9991
0.9993
0.9991
0.9993
0.9991
0.9993
0.9991
2nd
2nd
2nd
These results display non-conducting features of the complexes [35].
This is expected with chloride anion which favor its covalent attach-
ment with the metal ions.
complexes spectra at 856 and ≈656 cm−1 assign to δr (H2O) and
δw (H2O) [38]. Also, the appearance of vibration bands attributed
to the metallic bonds for υM–N in spectra supports all the previous
data suggesting the mode of coordination. The inability to assign
υM–Cl band due to the range of its appearance is out of the scan
range. The 1H NMR spectra of [Pd(Cl)2(C15H14N4O2S)](H2O) (Fig.
1S) and [Pt(Cl)2(C15H14N4O2S)](H2O) complexes are confirming
the data abstracted from IR. The down shift for the azomethine pro-
ton is suggesting the contribution of its nitrogen site. Also, more or
less unshifted OH peak supports its ruling out. (See Table 3.)
3.2. IR and 1H NMR
All essential vibration bands of the ligand and its complexes are
listed in Table 2. The ligand spectrum displays the following bands:
3336, 1399, 1595, 1034 and 820 cm−1 assigned for υOH, δOH, δNH),
υC_N and υC_S(IV), respectively [36]. The 1H NMR spectrum of the
ligand (Table 3) (Fig. 1S) also displays peaks attributed to the protons
in the configuration of thione tutomer form (Fig. 1)The comparative
study for the IR spectra represents the significant unchangeable appear-
ance for υC_S(I–IV), υNH and δNH bands. This proposed the exclusion
of these groups from coordination towards the metal ions. This will be
verified theoretically based on the optimizes stereo for sites distribu-
tion. The lower shift observed for υC_N band in the Co(II), Ni(II),
Pd(II) and Pt(II) spectra shows the first coordination site in the sphere.
Chloride anions are considered the integral part of complex sphere due
to its coordination towards the central atoms. This proposal is in agree-
ment with the anion gravimetric analysis and the non-conducting
feature. The significant shift observed for υOH and δOH bands in
[Co(Cl)2(C15H14N4O2S)](H2O) and [Ni(Cl)2(C15H14N4O2S)](H2O)2 com-
plexes, introduces the hydroxyl groups as the other coordination sites
with the two metal ions. This is supported by the appearance of υM–O
band at ≈530 cm−1. While, the υOH band suffering the decline to
high wave numbers, promote the presence of intra-ligand H-bonding
before the complexation process which destroyed after that. So, the li-
gand mode of coordination with the [Pd(Cl)2(C15H14N4O2S)](H2O)
and [Pt(Cl)2(C15H14N4O2S)] (H2O) complexes as a neutral bi-dentate
through the azomethine groups. While, the mode is changed to neutral
tetra-dentate with Co(II) and Ni(II) ions. The neutrality feature of the li-
gand at all is expected behavior with chloride salts. The spectra of all
3.3. Electronic spectra and magnetic measurements
The significant electronic spectral data and the magnetic moments
are reported in Table 4. All the complexes spectra and their correspond-
ing ligand were recorded in DMSO solvent with the absence of any
changes during dissolution. The ligand spectrum recorded for
5.2 mmol/l shows bands at 31,250 and 27,777 cm−1 for π → π* and
25,000 cm−1 for n → π* intra-ligand transitions. The molar absorptivity
values are, ε 1 = 226.9, ε 2 = 211.5 and ε 3 = 134.6 mol−1 dm cm−1
.
The high values are completely attached with the intra-ligand transition
bands especially with π → π* transitions. The high conjugation for
chromophor groups in the ligand form affecting on the position of
charge transfer bands which nearby the visible region and deepen
the color of the compound. Such molar absorptivity values were el-
evated with 3.3 mmol/l complex solution. This may refer to the
presence of d-d transitions which have high oscillator strength
values especially for the introductory transition step. The spectrum
of [Co(Cl)2(C15H14N4O2S)] (H2O) complex, exhibits two bands
at 16,666 and 18,518 cm−1 assign to 4T1g → 4A2g (υ2) and
4T1g → 4T1g (p) (υ3) transitions, respectively. The calculated spec-
tral parameters values (10Dq, B and β) (Table 4) are within the re-
ported range for octahedral geometry (Fig. 2). The high β value
(0.818) indicates the ionic interaction with coordinating sites. The
subnormal magnetic moment value (4.14 BM) point to the presence
of strong M-M interaction or a strong L → M charge transfer transi-
tion. Moreover, the low magnetic moment value (2.53BM) of
[Ni(Cl)2(C15H14N4O2S)](H2O)2 complex in agreement with Co(II)
complex appearance reflects the same assumption. The Ni(II) complex
spectrum displays two bands at 25,600 and 16,600 cm−1. These bands
are attributing to 3A2g → 3T1g (p) (υ3) and 3A2g → 3T1g (F) (υ2)
complexes display a broad surround the range of 3440–3100 cm−1
,
which could be attributed to the presence of solvent molecules [37].
These molecules may be physically or chemically attached with
the metal ions. The crystal water appears at frequencies higher
than that of the coordination. Therefore, the vibration modes
range (3420–3370 cm−1) considered a clear guide for the presence
of lattice solvent. The chosen solvent proposed mainly based on the
analytical, thermal and 1H NMR studies. The bands observed in
Table 8
The Hartree-Fock parameters calculated for the ligand and its complexes.
Compound
EH (eV)
EL (eV)
(EH-EL) (eV)
El-Eh
X (eV)
μ (eV)
η (eV)
S (eV-1)
ω (eV)
Ϭ (eV)
L
−0.21046
−0.31544
−0.22712
−0.31792
−0.31378
−0.08773
−0.09374
−0.01039
−0.16711
−0.09601
−0.1227
−0.2217
−0.2167
−0.1508
−0.2178
0.12273
0.2217
0.21673
0.15081
0.21777
0.149095
0.20459
0.118755
0.242515
0.204895
−0.1491
−0.20459
−0.11876
−0.24252
−0.2049
0.061365
0.11085
0.108365
0.075405
0.108885
0.030683
0.055425
0.054183
0.037703
0.054443
0.181124
0.1888
0.065071
0.389984
0.192781
16.29593416
9.02119982
9.228071794
13.26172005
9.184001469
Co
Ni
Pd
Pt

270
N.M. El-Metwaly, M.G. El-Ghalban / Journal of Molecular Liquids 220 (2016) 265–276
Table 9
Significant bond distances (Å) and dipole moment (Debye) of H3L ligand with its complexes.
1,4,5
2,3
CN15
CN14
CN20
CN19
13O–C
21O–C
22O–C
22O–C
M–N15
M–N14
M–N20
M–N19
M–O13
M–O21
M–O22
M–O22
Dipole moment
1)
2)
3)
4)
5)
1.28024
1.28744
1.44181
1.28199
1.28031
1.279270
1.280491
1.356362
1.280228
1.280206
1.363189
1.363025
–
–
–
–
5.4067
12.1226
7.8208
2.2841
2.9709
1.363221
1.36391
1.36304
1.36301
1.363098
1.36310
1.36301
1.36301
5.457591
3.053270
5.213593
5.213593
4.875687
2.846109
4.884031
4.884031
6.201717
3.838932
–
–
6.226970
3.584711
–
–
transitions, respectively in an octahedral geometry (Fig. 2). The lower
energy shift for d-d transitions is attached with bulk ligands, which
perhaps introduce weak coordination [39]. The spectral parameters
(10Dq, B and β) are also calculated [40]. The values are found to be
11,218, 560.9 and 0.539. The 10Dq value is found within the range of
3A2g → 3T2g (F) (υ1) transition. The β value indicates high covalent inter-
action of sites which convenient with known NiN6 and NiO6 structures
[41]. Generally, the shortage in β value is strongly associated with the re-
duction in the effective positive charge of central atom [42]. The Racah
inter-electronic repulsion parameter values are varied for 3d transition
metal complexes with changing Z and q values. Whereas, Z is the effective
cationic charge and q is the occupation number of the dq shell. The Racah
parameter is well-expressed by the relation: B (cm−1) = 384 +
58q + 124(z + 1) − 540 / (z + 1). The z value of cobalt is +1.103, con-
siderably below the formal oxidation state (II) this reduction in oxidation
state is suitable for M–N or M–O bonds [43]. Whereas, the value for nickel
is −0.256, which reflects the overcoming of ligand anionic character on
the nickel charge. The electronic spectra of two diamagnetic complexes,
[Pd(Cl)2(C15H14N4O2S)](H2O) and [Pt(Cl)2(C15H14N4O2S)](H2O) are in-
dicative for square-planar geometries (Fig. 2). Three spin-allowed
singlet-singlet d-d transitions are anticipated for the geometry proposed.
The ground states 1A1g, 1B1g and 1Eg are in order of increasing energy in
low spin d8 systems. 1A1g → 1A2g (υ1) and 1A1g → 1B1g (υ2) transitions
observed at ≈20,000 and 22,000 cm−1 are characteristic for four arms
surround the nucleus in planar state. Also, charge transfer bands observed
in all investigated spectra in the range of 28,000–30,000 cm−1 may assign
for N → M and O → M bands. Intra-ligand transition bands expose to little
the line width at half maximum height, Cu/Kα (λ) = 1.5406 Å. The
inner crystal plane d-spacing values were determined by using Bragg
equation: nλ = 2dsin(θ) at n = 1. The sizes calculated are distinguished
in nanometer sized range (below 15 nm). The edge lengths of the parti-
cles for imaginative cubic shapes are as fellow; 93.72(H3L), 101.78(Co).
79.04(Ni), 79.11(Pd) and 70.03(Pt) Å.
3.5. Transmission electron microscopy
TEM has turn out as widely employed method for illustrating the
particle shape and size. High resolution transmission electron micro-
graph images were extracted (Fig. 3S). The micrographs exhibit nano-
meter sized particles for Co(II) and Ni(II) complexes with diameter
range 10.2–91.5 nm. The size determined for the ligand, Pd(II) or
Pt(II) complexes display their presence in micro-scale. This appearance
may refer to the aggregation for the particles which prohibit the exact
determination. The images show the spherical shape as the main aspect
except Pd(II) complex appears by rocky shape [37]. The spherical shape
of nano-particles may be attributed to highly symmetric spherical
chlorido groups introducing the complexation area. These topologies
of the complexes pointed to the presence of metal ions have a signifi-
cant influence on the formation of the nanometer particles [47]. The
spherical shapes observed express that these morphologies are consti-
tuted by a distinct accumulation of several individual particles in poly-
crystalline nature. The aspect of moderately strong diffraction spots
rather than diffraction rings confirms the formation of moderately sin-
gle crystalline cube of complexes [48,49]. The dark areas in micrographs,
are related to the high concentration of the particles naturally com-
bined. The nanometer sized aspect may improve the properties in
current application concerning the biological activity area with respect
to bulk analogue. This feature may facilitate the penetration of particles
inside the cell membrane. The out of comparison in-between the XRD
and SEM results may clarify the difference between two techniques
with the priority of XRD.
shifted appearance around 31,000–35,000 cm−1 attributed to n → π and
⁎
⁎
π → π transitions.
3.4. X-ray diffraction
XRD patterns were carried out in the 10° b 2θ b 90° range for the free
ligand and its complexes [Figs. 3, 2S] to give an apparent seeing about
the lattice dynamics of solid compounds. The clear patterns exhibit
the absence of contamination of starting materials. Known methods
[44] were used to emphasize on the obscurity of peaks attributed to
the reactants. All the patterns reflect comparatively nano-crystalline
features for all compounds [45,46]. This may be attributed to the forma-
tion of a well-defined distorted crystalline structures. The θ, d values,
full width at half maximum (FWHM) of prominent intensity peak,
relative intensity (%) and particle size of compounds were existed in
Table 5. The crystallite size was calculated by applying FWHM of the
characteristic peaks using Deby–Scherrer equation: B = 0.94 λ /
(S Cos θ), where S is the crystallite size, θ is the diffraction angle, B is
3.6. Thermal analysis
The plausible degradation behavior of all interested compounds over
the stages was translated to the data displayed in Table 6. The Schiff base
ligand was decomposed completely over three stages till reaching
550 °C with carbons residue. The degradation process for all investigat-
ed complexes was started at low temperature. The first step contributes
to the removal of solvent molecules attached physically with the coordi-
nation sphere. The coordinating sphere starts its decomposition approx-
imately with the first step which takes a broad range of temperature.
Table 10
Molecular docking energy values obtained for Schiff base ligand towards different receptors.
Receptor
Est. free energy of binding
(kCal/mol)
Est. inhibition constant
(Ki) (uM)
vdW + bond + desolve
energy (kCal/mol)
Electrostatic energy
(kCal/mol)
Total intercooled energy
(kCal/mol)
Frequency
Interact
surface
2ylh
3t88
3cku
3ty7
2jrs
−6.53
−4.92
−2.82
−3.60
−3.34
16.30
246.46
8.52
2.31
3.59
−8.38
−7.26
−4.67
−5.30
−5.74
−0.22
+0.05
+0.05
−0.17
−0.06
−8.60
−7.22
−4.62
−5.47
−5.80
30%
10%
10%
10%
30%
686.011
721.741
451.107
538.005
631.708

N.M. El-Metwaly, M.G. El-Ghalban / Journal of Molecular Liquids 220 (2016) 265–276
271
Table 11
3.7.1.1. Coats–Redfern equation. The equation is an integral method,
represented as:
The inhibition zone values (mm) against different microorganisms, for the ligand and its
complexes.
T2
a
Compound
Fungus
Bacteria
ꢀ
ꢁ
Z
Z
da
ð1−aÞ
A
φ
‐Eꢀ
¼
exp
dt:
ð5Þ
Aspergillus
flavus
Candida
albicans
Escherichia coli
(G−)
Staphlococcus
aureus (G+)
n
RT
o
T1
1)
2)
3)
4)
10.7 0.24
11.4 0.36
10.8 0.41
11.6 0.36
10.2 0.31
–
9.9 0.34
10.7 0.31
11.1 0.43
10.9 0.21
8.8 0.24
–
16.7 0.42
18.1 0.48
18.9 0.49
16.4 0.35
16.7 0.59
22
18.1 0.41
14.6 0.52
15.4 0.45
12.7 0.37
18.2 0.44
18
For convenience of integration the lower limit T1 is usually taken as
zero. This equation on integration gives:
5)
ꢂ
ꢃ
ꢀ
ꢁ
Ampicillin
Norfloxacin
Amphotericin B
− lnð1−aÞ
AR
φEꢀ
Eꢀ
ln
¼ ln
−
:
ð6Þ
T2
–
17
–
18
30
–
31
–
RT
A plot of ln½− lnð1−aÞꢁ (LHS) versus 1/T, E* is the energy of activation
T2
Sequential successive degradation process for all complexes
through the stages up to 580 °C was followed. The residual part re-
corded includes free metal atoms, metal polluted with carbons or
metal oxide. A slight difference was observed between the calculat-
ed and found weight losses in few degradation stages. This is due to
the overlapping in-between follower steps which prohibit the exact
determination for the step limits. This is affecting on calculating the
thermodynamic parameters for all stages but choosing suitable ones
have distinct limits.
in J mol−1 calculated from the slop and A is (S−1) from the value of
intercept (Fig. 4S). The entropy of activation ΔS* in (J K−1 mol−1) was
calculated by using the equation:
ꢀ
ꢁ
Ah
KBTs
ΔSꢀ ¼ Rln
ð7Þ
where KB is the Boltzmann constant, h is the Plank's constant and Ts is
the DTG peak temperature [23].
3.7.1.2. Horowitz–Metzger equation. Using derived relation [28] i:
3.7. Theoretical calculations
E
RTm
ln½− lnð1−aÞꢁ ¼
Θ
ð8Þ
3.7.1. Kinetic studies
In order to emphasis on the influence of metal ion on the thermal be-
havior of the complex, the order n and the heat of activation E for defiant
decomposition stages were calculated from the TG and DTG.
where a, is the fraction of the sample decomposed at time t and Θ=
T−Tm.
Fig. 2. The optimized structures for all complexes.

272
N.M. El-Metwaly, M.G. El-Ghalban / Journal of Molecular Liquids 220 (2016) 265–276
Fig. 3. X-ray patterns of Schiff base ligand (A) and Ni(II) complex (B).
Plot, ln[−ln(1−a)] versus Θ (Fig. 4S), was found to be linear, from
the slope of which E, was calculated and Z can be deduced from the
relation:
global hardness (η), global softness (S), global electrophilicity index
(ω) and the absolute softness (ϭ) were evaluated according to definite
equations [52,53]. Electrophilicity index (ω) is one of the most impor-
tant quantum chemical descriptors in describing toxicity and the reac-
tivity of various selective sites. The electrophilicity may quantify the
biological activity of drug receptor interaction. Also, this index measures
the stabilization energy when the system acquires extra negative charge
from the environment. η and ϭ indexes, are the measure of the molecu-
lar stability and reactivity also, their concepts are related to each others.
The softness indexes are the vice verse image for global hardness [54].
ꢀ
ꢁ
Eφ
RT2m
E
RTm
Z ¼
exp
ð9Þ
where φ is the heating rate, the order of reaction, n, can be calculated
from the relation:
n ¼ 33:64758−182:295am þ 435:9073a2m−551:157am3
þ 357:3703a4m−93:4828a5m
ð10Þ
3.7.2.1. Quantum chemical parameters. The calculated data presented in
Table 8 reflect the following notes for the ligand in free state:
I) The molecule is having soft character with flexible donation to-
wards the metal ions which reflects its reactivity. II) The positive elec-
trophilicity index (χ) value and the negative electronic chemical
potential (μ) value indicate that the molecule capable for accepting
electrons from the environment and its energy must decrease upon
accepting electronic charge. Therefore, the electrochemical poten-
tial must be negative.
where am is the fraction of the substance decomposed at Tm.
The enthalpy of activation ΔH* and Gibbs free energy were calculat-
ed from using ΔH* = E* − RT and ΔG* = ΔH* − TΔS*, equations. Also
the entropy of activation ΔS* was calculated from Eq. (7) and the data
were tabulated (Table 7). The following observations were recorded:
(i) the reduction for the activation energy (E) values for the second
step in complexes TG, may reflect the weakness of intra-ligand bonds
due to complexation (ii) the negative values of ΔS* may indicate that
the fragments have ordered structures which override along the com-
plexes degradation (iii) the positive values of ΔH* reflect the endother-
mic decomposition process, (iv) the positive values of ΔG* reveal that
the free energy of the decomposition residue is higher than that of the
initial compound, and the decomposition stages are non-spontaneous.
The upraising of TΔS*values (by negative singe) than the ligand lead
to override ΔG* values which may reflect the lower rate of decomposi-
tion for the complexes [50].
The modeling calculations for complexes are displaying the following
notice;
I) Small frontier orbital energy gapes (ΔE) were observed in compar-
ing with the ligand value, may clarify the softness of complexes which
reflect high expectation for biological reactivity. II) The EHOMO values
elevated from the free ligand may be accompanied with the elongated
weak metal–ligand bonds. III) The dipole moment values ordered by:
Co(II) N Ni (II) N Pt(II) N Pd(II). This may transpire the ionic interaction
of donor sites with Co(II) ion than the others. This is considerably
agrees with the spectral Racah parameter values for Co(II) and Ni(II)
complexes.
3.7.2. Molecular modeling study
Gaussian09 Molecular Modeling for the free ligand and its metal ion
complexes were implemented to abstract important quantum chemical
parameters and optimized geometries. The frontier orbital energy gap
between EHOMO & ELUMO is an important parameter used to characterize
the electronic structure of molecules and also used to define their reac-
tivity [51]. From the MO's images (Fig. 4), it can be seen that the HOMO
and LUMO are mainly centered on N atoms of carbothiohydrazide
moiety, which is considered the location for donor and acceptor
atoms. Although, the LUMO level is also centered with Pd(II) and
Pt(II) atoms, which considered the other acceptors of charge from
HOMO level. Moreover, electronegativity (χ), chemical potential (μ),
3.7.2.2. The bond length and atomic charges. According to the numbering
scheme given in the view (Fig. 2), the bond lengths over optimized ge-
ometries were calculated. Significant bond lengths were deducted and
tabulated in Table 9. The coordinating groups (C_N and O\\C) suffer
an elongation than the original form of the ligand. Also, the coordinating
sites have high charge density which qualify them for best coordination.
Charges over free coordinating sites are; N(15) = −0.17623,
N(20) = −0.166195, O(13) = −0.150877 and O(22) = −0.162303.
The approximately reduced charges over oxygen atoms before coordina-
tion, may refer to their participation in conjugation with phenyl groups or

N.M. El-Metwaly, M.G. El-Ghalban / Journal of Molecular Liquids 220 (2016) 265–276
273
presence of intra-ligand H-bonding. This may minimize their chance for
coordinating approach with all metal ions. The oxygen sites are coordinat-
ing with Pd(II) and Pt(II) ions, so their effective charges are reduced only
with these concerned complexes. Also, the two nitrogen charges were
reduced after complexation. This is convenient with their participation
in coordinating approach.
aspergillus flavus complexed with its inhibitor 8-azaxanthin and chloride,
Classification: oxidoreductase), canadida albicans (2ylh, structure of
N-terminal domain of Candida albicans ALS9-2G299W mutant, Classifica-
tion: cell adhesion) and hepatocellular carcinoma (2jrs, Solution NMR
Structure of CAPER RRM2 Domain. Northeast Structural Genomics Target
HR4730A, Classification: RNA binding protein) are the receptors docked
with Schiff base ligand (inhibitor). The calculated energies for the docking
process are listed in Table 10. The free energy of binding, inhibition con-
stant, electrostatic energy, total intercooled energy and interact surface
for receptor-inhibitor complexes were calculated. So, the reduction in
binding energy due to mutation, will increase the inhibitor binding affin-
ity towards protein receptors [55]. Also, these data introduce the best in-
teraction stability for docked complexes (Fig. 5, 5S). According to
computational calculation HB plot curves (Figs. 6, 6S) display different in-
teraction degrees arranged by: 2jrs N 3t88 N 2ylh N 3ty7 N 3cku. This is re-
ferring to variable capability for H-bonding interaction inside the docked
complexes. A distinguish inter-hydrogen bonding was appeared with 2jrs
receptor-inhibitor complex. 2D-plot curves (Figs. 7, 7S) explain the mode
of interaction inside the docking complex. The inhibitor thioamide
3.7.3. Molecular docking
Over the last decade, computational amplitude enhanced dramati-
cally making possible to use more sophisticated and computationally
intense methods in computer-encouraged drug design. The Autodock
tools used to predict the biological features of candidate drug or em-
phasis on experimental results. This study interested in using defiant
protein receptors attributed to microorganisms used in biological appli-
cation. Escherichia coli (3t88, Crystal structure of Escherichia coli MenB in
complex with substrate analogue, OSB-NCoA, Classification: lyase/lyase
inhibitor), Staphlococcus aureus (3ty7, Crystal Structure of Aldehyde
Dehydrogenase family Protein from Staphylococcus aureus, Classifi-
cation: oxidoreductase), Aspergillus flavus (3cku, Urate oxidase from
Fig. 4. The frontier molecular orbital's of HOMO(1) & LUMO(2) pictures of the optimized, ligand, Co(II), Ni, Pd(II) and Pt(II) complexes (A,B,C,D and E, respectively).

274
N.M. El-Metwaly, M.G. El-Ghalban / Journal of Molecular Liquids 220 (2016) 265–276
Fig. 4 (continued).
NH groups, are responsible for interaction with receptors. Finally the
pharmacologically activity of the investigated Schiff base ligand was sub-
stantially anticipated.
drug-likeness effect may attribute to the reduction for metal ion
charges which calculated previously. These reduced charges for cen-
tral atoms enhance the lipophilicity of the complex inside the cell
lipid. This lipid solubility facilitates the interaction of the compound
with biological systems and blocking their active sites. The inhibition ac-
tivity against hepatocellular carcinoma cells (Fig. 8) were recorded. The
weak inhibition is the general trend appeared except for Co(II) and
Ni(II) complexes. IC50 was determined for all complexes, in-between
Co(II) and Ni(II) complexes have 18.8 and 36 μg values. These values in-
terpret the significance effect of low concentration of such complexes
against hepatocellular carcinoma cells.
3.8. Biological activity
The biological investigation was carried out towards various micro-
organisms and the results were displayed in Table 11. The ligand and
its complexes display significant inhibitory effect against all bacteria
and fungi. Co(II) and Ni(II) complexes exhibit serious inhibition
appeared with zone diameter (mm) nearby known drugs. This
Fig. 5. Protein-inhibitor complexes for 2jrs and 3t88 receptors.

N.M. El-Metwaly, M.G. El-Ghalban / Journal of Molecular Liquids 220 (2016) 265–276
275
Fig. 6. HB plot of 2JRS and 3t88 receptors with H3L inhibitor.
4. Conclusion
calculated geometric parameters introduce a distinguish bioactive
feature of all compounds. Molecular docking using defiant protein re-
ceptors attributed to the microorganisms executed in biological applica-
tion as; 3t88, 3ty7, 3cku, 2ylh and 2jrs were carried out. Considerable
reduction in binding energies were recorded along the docking process.
Antibacterial and antifungal activates were tested against different
microorganisms and display a comparable inhibition activity along the
investigation process. IC50 was determined for all compounds against
The synthesized complexes were investigated carefully using all
possible tools. Square-planar and octahedral configurations are the
two proposed geometries. XRD patterns and TEM images suggest the
nanometer sized appearance for all investigated complexes. Molecular
modeling calculations were carried out using HF/LANL2DZ base set
displayed the optimized structures agree with the spectral data. The
Fig. 7. 2D plot of 2JRS and 3t88 receptors with H3L inhibitor.

276
N.M. El-Metwaly, M.G. El-Ghalban / Journal of Molecular Liquids 220 (2016) 265–276
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Appendix A. Supplementary data
Supplementary data to this article can be found online at http://dx.
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