Synthesis, spectral characterization, DNA binding, catalytic and in vitro cytotoxicity of some metal complexes

Article abstract of DOI:10.1016/j.molliq.2021.115381

A series of 2-(4-sulfamethazine)hydrazono-5,5-dimethylcyclohexane-1,3-dione (HL) and its complexes of Co(II), Ni(II) and Cu(II) (1–3) were synthesized. Elemental measurements, FTIR, ¹H NMR, ¹³C NMR, UV–Visible, X-ray diffraction analysis, and magnetic measurements have characterized the ligand and its complexes. By coordinating with the oxygen atom of the carbonyl group (C=O) and through the hydrazone moiety nitrogen atom (-NH-) with deprotonation, the ligand (HL) functions as a monobasic bidentate ligand. The coordination geometry of the complexes Co(II) and Ni(II) is octahedral, where the complex Cu(II) is square planar. The ligand and its complexes were determined with the optimized bond lengths, bond angles and quantum chemical parameters. The ligand and its complexes calves thymus DNA linking activity was examined through absorption spectra and viscosity measurements. Results of the evaluation of synthesized compounds against the Sections of MCF-7 and HepG-2 active tumor cells have been published in the viability assay for vinblastine and colchicine, relative to positive controls. The DPPH free radical-scavenging assay specifies the in vitro anti-oxidant function of all complexes. Finally, fungal (Candida albicans), gram-negative (Escherichia coli) and gram-positive (Staphylococcus aureus) bacteria have been investigated for the anti-microbial activities of the complexes using the disc diffusion process. Molecular docking was used to predict the binding of SARS-CoV-2 key protease in complex COVID-19 (5REA) between the ligand and breast cancer mutant (3hb5) receptor and the crystal structure.

Full text of DOI:10.1016/j.molliq.2021.115381

Journal of Molecular Liquids 326 (2021) 115381
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
Synthesis, spectral characterization, DNA binding, catalytic and in vitro
cytotoxicity of some metal complexes
Hala A. Kiwaan, Ayat S. El-Mowafy, Ashraf A. El-Bindary⁎
Chemistry 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 2-(4-sulfamethazine)hydrazono-5,5-dimethylcyclohexane-1,3-dione (HL) and its complexes of Co
Received 18 December 2020
Received in revised form 3 January 2021
Accepted 11 January 2021
Available online 14 January 2021
1
13
(II), Ni(II) and Cu(II) (1–3) were synthesized. Elemental measurements, FTIR, H NMR, C NMR, UV–Visible,
X-ray diffraction analysis, and magnetic measurements have characterized the ligand and its complexes. By co-
ordinating with the oxygen atom of the carbonyl group (C=O) and through the hydrazone moiety nitrogen
atom (-NH-) with deprotonation, the ligand (HL) functions as a monobasic bidentate ligand. The coordination ge-
ometry of the complexes Co(II) and Ni(II) is octahedral, where the complex Cu(II) is square planar. The ligand and
its complexes were determined with the optimized bond lengths, bond angles and quantum chemical parame-
ters. The ligand and its complexes calves thymus DNA linking activity was examined through absorption spectra
and viscosity measurements. Results of the evaluation of synthesized compounds against the Sections of MCF-7
and HepG-2 active tumor cells have been published in the viability assay for vinblastine and colchicine, relative to
positive controls. The DPPH free radical-scavenging assay specifies the in vitro anti-oxidant function of all com-
plexes. Finally, fungal (Candida albicans), gram-negative (Escherichia coli) and gram-positive (Staphylococcus au-
reus) bacteria have been investigated for the anti-microbial activities of the complexes using the disc diffusion
process. Molecular docking was used to predict the binding of SARS-CoV-2 key protease in complex COVID-19
Keywords:
Antitumor activities
Complexes
COVID-19
DNA binding
Molecular structure
(5REA) between the ligand and breast cancer mutant (3hb5) receptor and the crystal structure.
©
2021 Elsevier B.V. All rights reserved.
1. Introduction
increasing attention recently. Therefore, the rich structure of β-
diketones coordination has recently been examined [8].
Aromatic azo compounds have omnipresent motives and are widely
Because of their chemical stability, simple preparation [9] including
its potential functionalization at three separate molecule locations, β-
diketones is fascinating chemicals [10]. The well recognized of these is
the dimedone with fascinating and unique effects, such as pharmaco-
logical activities such as antibacterial, antiviral, antioxidant and antitu-
mor activities [11]. Dimedone constitutes an important group of
compounds due to the presence of characteristic keto group, which
acts as a starting material for many biologically active heterocyclic com-
pounds [12]. Dimedone has reactive sites that can be modified to gener-
ate a range of antimicrobial agents and fungicides by adding different
heterocyclic moieties. As biological activity applicants, sulfonamide
bases are commonly used as antifungal [13], anti-bacterial [14], antiox-
idant [15] and anticancer drugs [16]. By understanding such special
properties, a lot of these bioactive derivatives were developed. For the
past several decades, hydrazo compounds generated from sulfonamides
have been a field of concern for natural researchers due to its bioactive
functions [12]. We managed to merge the chemistry of these species to
fight resistance to antibiotics as a consequence of the pharmacological
effects of sulfonamides and metal complexes [17].
used in organic chemicals for organic colors, markers, Dyes, chemicals in
meat, Radical reaction initiators, medicinal agents and so on [1,2]. Ac-
cording to this potential combination for interesting functional proper-
ties with a variety of molecular geometries of their complexes, over the
last decades the coordination chemistry of aromatic azo compounds has
been extensively studied. These complexes have attracted interest in a
number of fields, including conducting and magnetic material prepara-
tion, nonlinear optics, supramolecular chemistry, catalysis and
bioinorganic chemistry [3,4]. Methylene active compounds (β-
diketones, β-dinitriles, benzoylacetonitriles, and etc.). Also, they were
from considerable Considering investing in organic chemistry, For ex-
ample, in several chemical syntheses, β-diketones are essential start
materials [5,6], and in fragrance and medical sectors, in particular [7].
In addition, variety of β-diketone members it has long been widely
used for the coordination chemistry as components of multidentate li-
gands in enzymes-supramolecular chemistry, they were the subject of
Due to the fascinating reaction shown by the resulting complexes
and the existence of the ligands that determine the function of such
⁎
Corresponding author.
E-mail addresses: abindary@yahoo.com, abindary@du.edu.eg (A.A. El-Bindary).
https://doi.org/10.1016/j.molliq.2021.115381
167-7322/© 2021 Elsevier B.V. All rights reserved.
0

H.A. Kiwaan, A.S. El-Mowafy and A.A. El-Bindary
Journal of Molecular Liquids 326 (2021) 115381
complexes, the chemistry of Co(II), Ni(II) and Cu(II) complexes is of
great significance [18]. In the fields of microbiology, photocatalysis,
and photophysics, copper compounds can be used [19]. Because of
their positive transition states and redox properties, as well as func-
tional DNA samples, the interest in copper (II) acetate complexes as
building blocks in supramolecular devices has increased in recent de-
cades. Copper compounds frequently display encouraging anti-cancer
behavior effects and target a large range of tumors [20,21].
sodium nitrite (0.69 g, 0.01 mol) to the lowered mixture (0 °C) of re-
quired sulfamethazine (0.01 mol) in 10 mL hydrochloric acid (5 M).
The diazonium salt solution was then applied dropwise with a vigorous
stirring for 1 h to the β-diketonate solution. The immediately formed
colored mixture was collected by sintered glass gooch, washed several
times with water and ethanol washed in a vacuum desiccator over an-
hydrous CaCl
HL = 2-(4-sulfamethazine)hydrazono-5,5-dimethylcyclohexane-
1,3-dione.
2
. The resultant ligand (HL) is:
Here, we record the formulation and explanation of 5,5-dimethyl-2-
(
(
4-sulfamethazine)hydrazono)cyclohexane-1,3-dione (HL) and its Co
II), Ni(II) and Cu(II) complexes (1–3) by different spectroscopic tech-
2.3. Preparation of the complexes (1– 3)
niques. The complexes have been measured for optimized bond lengths,
bond angles and quantum chemical parameters. Using ultraviolet ab-
sorption spectra and viscosity measurements the intercalative mode
of DNA-binding properties of the complexes with CT-DNA was investi-
gated. With the aid of Coats–Redfern and Horowitz-Metzger methods
the measured thermodynamic parameters of the complexes are exam-
ined. In addition, the ligand and its complexes were primarily screened
for their in vitro cytotoxicity antioxidants and anti-microbial activities.
Co(II), Ni(II), and Cu(II) complexes (1–3) were synthesized by the
general procedure [12,24]. A molar ratio quantity of the appropriate li-
3
gand (0.01 mol) in ethanol (20 cm ) was added dropwise to a hot eth-
3
anol (20 cm ) solution of metal nitrate (0.01 mol) and the mixture was
stirred for 5 min. In the colored solution, sodium acetate (0.01 mol) was
added and the reaction mixture was refluxed for 2 h. The formed col-
ored precipitate was separated washed with hot ethanol and dried by
filtration in a vacuum desiccator over anhydrous CaCl
.4. DNA binding experiments
The binding properties of the CT-DNA complexes of ligand (HL) and
2
.
2
. Experimental
2
2.1. Chemicals and instruments
Sulfamethazine diazonium salt, 5,5-Dimethylcyclohexane-1,3-dione,
Tris-HCl, Dimethyl sulfoxide (DMSO) and 3,5-di-tertbutylcatechol (3,5-
DTBC) were purchased from Aldrich Chemical Company and used with-
its Co(II), Ni(II), and Cu(II) were analyzed usage of spectroscopy for
electronic absorption. The inventory of CT-DNA solution has been devel-
oped in a 5 mM Tris-HCl/50 mM NaCl buffer (pH = 7.2) and processed
for full dissolution at 4 °C and was used for no more than 4 days. 1.8–1.9,
which indicates DNA was sufficiently protein-free [25]. The concentra-
tion of CT-DNA was determined by UV–vis absorption at 260 nm, taking
6600 M cm as the coefficient of molar absorption [26]. Titrations of
electronic absorption spectra were conducted at 25 °C with constant
concentration of compounds and varying concentration of CT-DNA.
3 2 2 3 2 2
out any further purification. Metal salts Co(NO ) .6H O, Ni(NO ) .6H O,
Cu(NO .3H O and CH COONa were purchased from Sigma and used
)
3 2
2
3
without any further purification. Calf thymus DNA (CT-DNA) was pur-
chased from SRL (India). Organic solvents were of analytical grade and
were used as obtained.
−1
−1
The Automated Analyzer CHNS Vario ELIII, Germany, obtained micro
analytical data (C, H and N). For each stoichiometric determination, the
amount of cobalt, nickel, and copper was calculated using the Flame Spec-
trophotometer of Atomic Absorptio (Model Varian AA240FS). The survey
equipment has been used to obtain transmission scheme: FTIR spectra
The intrinsic binding constant K
lated using Eq. (1) [27]:
b
of CT-DNA compounds were calcu-
À
Á
À
Á
À
Á
½DNAꢀ= εa−εf ¼ ½DNAꢀ= εa−εf þ 1=Kb εa−εf
ð1Þ
−1
(
KBr discs, 4000–400 cm ) by the spectrophotometer Jasco FTIR-4100;
1
13
JEOLECA-500 II H NMR and C NMR spectra operating at 500 MHz
using DMSO‑d as solvent. Using X-ray diffraction (XRD) technology,
where [DNA] is the concentration of CT-DNA in base pairs, є
a
is the vec-
6
tor of extention detected at the given DNA concentration for the Aobs
[compound], є is the function of extention of The free in solution sub-
stance, and є is the compound's extinction coefficient when totally
/
structural variations of the as-prepared materials were examined. The
molecular framework, crystal structure, and crystal structure values of
the complexes were measured and optimized through CRYSFIRE and
CHEKCELL computer programmes [22]. The molecular structures of the
compounds investigated were optimized using the 3–21 G basis set of
the HF process. With the Perkin Elmer ChemBio Draw, the molecules
were constructed and optimized using Perkin Elmer ChemBio3D software
f
b
bonded to DNA.
The relative viscosities η were determined [28] within the range of
−4
(0.1–0.6 × 10 mol/L) at chemical concentrations and each molecule
−3
was added to a DNA solution (10
mol/L) in the viscometer [29].
With a digital stopwatch, the average flow time of three replicates
1/3
[
11]. Measurements of Susceptibility to magnetism at room temperature
were calculated using Hg[Co(SCN)4] as a calibrant on a Johnson Matthey
magnetic susceptibility balance. Based on the equation: μeff = 2.84 (X
was measured. The data were provided as (η/η
[DNA] the percentage of the represented in figure to DNA, where η
and η are the viscosity of the DNA in the existence and exclusion of un-
o
)
vs. [compound]/
M
o
corr 1/2
certainty, respectively [30].
−3
2.5. Biological evaluation
(conductivity/TDS meter model Lutron YK-22CT), where the cell constant
was calibrated with 0.1 M KCl solution.
2.5.1. In vitro cytotoxicity evaluation
The HL and its complexes (1–3) cytotoxicity assay was performed on
human breast carcinoma (MCF-7) and human hepatocellular carcinoma
2.2. Preparation of the hdrazone (HL)
(
HepG-2) cells [31,32]. In Dulbecco's modified medium, with 10% heat-
The ligand (HL) was synthesized between the sulfamethazine diazo-
nium salt and 5,5-dimethylcyclohexane-1,3-dione (dimedone) accord-
ing to the Japp-Klingemann reaction [11,23]. Dimedone (1.40 g,
.01 mol) was dissolved in ethanol solution and sodium acetate
3.65 g, 0.01 mol) of 50 mL NaOH (0.4 g, 0.01 mol). The corresponding
β-diketonate sample was diluted to a volume of approximately
50 mL with water and lowered to 0 °C. The diazonium salt solution
was prepared separately by adding the dissolved aqueous solution of
inactivated bovine fetus's serum, HEPES (4-(2-hydroxyethyl)-1-
piperazineethanesulfonic acid) buffer, 1% L-glutamine, and 50 μg/mL
gentamycin, the cells were dispersed separately. The cells were incubated
separately with 0.2 ml from every drug afterwards and a regular DMSO
medication and distilled to 8 concentrations of 500, 250, 125, 62.5,
31.25, 15.60, 7.80, 3.90, 2.0, 1.0 and 0.0 μg/mL, respectively. The optical
composition was calculated by the addition of sulforhodamine B at
540 nm and adjusted by a background absorbance colorimetric procedure
0
(
1
2

H.A. Kiwaan, A.S. El-Mowafy and A.A. El-Bindary
Journal of Molecular Liquids 326 (2021) 115381
[
33]. To measure the optical density and to assess the number of viable
cells, the micro plate reader (SunRise, TECAN, Inc., USA) was used. The vi-
ability percentage was determined as: (OD /OD ) x 100%, where the mean
optical density of untreated cells is OD and the mean optical density of
wells treated with the sample being evaluated is OD . In order to obtain
compound is stable and strongly absorbed at λmax = 400 nm [35].
Therefore, the activity and interaction speeds can be determined by
electronic spectroscopy as the maximum quinone absorption emerges.
t
c
c
t
3. Results and discussion
the survival curve of and cancer cell line after medication with the stated
compound, we plotted the relationship among surviving cells and com-
pound concentration. The 50% inhibitory concentration (IC50) was mea-
sured using graph pad Prism software (San Diego, CA., USA) from
graphical plots of the dose response curve for each concentration. IC50's
easiest approximation the x-y graph for the data should be plotted and
matched to a horizontal path i.e., y = a*x + b (Eq. 2):
The findings of the physical properties of the prepared ligand (HL)
and its complexes of Co(II), Ni(II) and Cu(II) (1–3) are collected along
with their elemental analysis in Table 1. The 1:1 metal-ligand stereo-
chemistry reveals all the complexes. They are air-stable and soluble in
the most popular organic solvents. Measurements of the molar conduc-
tance of the obtained complexes were carried out in DMF at a concen-
−
3
tration of 10
M and 25 °C. The molar conductivity values ranged
IC50 ¼ ð0:5−b Þ=a
ð2Þ
−1
2
−1
between 8 and 12 Ω cm mol for complexes (1–3) show the non-
electrolytic existence of complexes [36,37]. However, conductivity mea-
surements were repeated at specific time intervals (0, 24 and 48 h) to
see the stability of the complexes over time. As a result, there was no
significant change in the measurements.
2.5.2. Anti-oxidant
By 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging
assay, the anti-oxidant activity of HL and its complexes was measured
spectro-photometerically. The freshly prepared violet solution
3.1. FTIR
(
0.004%, w/v) was stored in DPPH methanol at 10 °C in the dark [34].
The complexes examined were prepared with different concentrations
of 1280, 640, 320, 160, 80, 40, 20, 10 and 0.0 μg/mL in methanol. In
In contrast to the spectrum acquired for the corresponding ligand
HL), the FT-IR spectra of the Co(II), Ni(II) and Cu(II) complexes (1–3)
indicate important shifts. The ligand may exist as a mix of various tauto-
mers of keto-enol that deprotonate and bind as a monomeric bidentate
ligand to the metal. The following features can be pointed out:
(
3
mL of DPPH solution, each compound (40 mL) was added and the ab-
sorbance was measured spectro-photometerically. The absorbance de-
crease at 515 nm was observed continuously, with data being
collected at intervals of 1 min before the absorbance stabilized after
1
. In the ligand spectrum a medium range of the ν(NH) group, which
corresponded to the H-bonded hydrazone formation at 3268 cm−
region, disappeared in the complexes indicating that the ligand was
coordinated in the deprotonated hydrazone shape [18,38]. However,
1
6 min. The negative control absorbance (DPPH radical) values were
1
calculated without the compound being checked. Also, for comparison
and measurement, the reference anti-oxidant reagent (ascorbic acid)
was also measured. The percentage of DPPH radical inhibition (PI) has
been determined in accordance with Eq. (3):
in the ligand spectrum seen in the complexes that did not participate,
the ν(NH) band of the sulphonamide group was 2952 cm−
1
.
ÂÀ
Á
Ã
PI ¼ Acontrol−Acomplex =Acontrol ꢁ 100%
ð3Þ
2. The band because of ν(C=O….H) and ν(C_O free) groups appeared
−1
in the spectrum of the ligand at 1694 and 1625 cm , respectively
−
1
where Acomplex = absorbance of DPPH + complex at t = 16 min, and
[
39]. The band ν(C_O free) was shifted by 6–8 cm to a lower
Acontrol = absorbance of DPPH radical + methanol at t = 0 min [34].
wavenumber, indicating their coordination with the metal core. In
addition to the free ligands, the observed hypsochromic change in
the IR wavenumbers of the complexes can be connected to a
strengthening of the strong intra molecular resonance supported hy-
drogen bond in the complexes [40].
2.5.3. Anti-bacterial activity
Both synthesized HL and its complexes (1–3) were carried out inde-
pendently analysis against gram-positive coccus (Staphylococcus au-
reus), gram-negative rod (Escherichia coli), (Candida albicans) and
Fungus. The compound samples were analyzed using a 6.0 mm diame-
ter diffusion agar system (100 μL was analyzed). The average size of
−1
3
. Spectrum of the ligand display a bands at 1596 and 1370 cm due to
the azomethine group of ν(C=N)hyd and ν(C=N)py, respectively
without a significant difference from that of the complexes suggest-
ing a nonbonding nature of the nitrogen atom of (C=N) group to
metal ions [41].
5
cm of filter paper (whatman discs is processed and sterilized in an au-
toclave. Seeded with Staphylococcus aureus, Escherichia coli and Candida
albicans, The paper discs were saturated and sterile put in plates con-
taining agar media containing nutrients (agar 20 g, beef extract 3 g, pep-
tone 5 g). In DMSO solvent, antimicrobial action of the common
standard antibiotic Gentamycin (4 μg/mL) and Ketoconazole
4
. All of the spectra obtained for the complexes indicate very similar
profiles of acetate absorption that are more similar to those normally
−1
associated with coordinated acetate. Bands at 1534–1524 cm re-
−1
gion for νasym(OCO) and aband at 1437–1432 cm region for νsym
(
100 μg/mL) antifungal activity was also recorded. The % activity index
(
OCO). The Δν values (νasym–νsym) of (OCO) for all the complexes
−
1
for the compounds Using has been measured Eq. (4):
are in the range 92–102 cm
that for NaOAc (Δν = 164 cm ) [42,43], indicating a bidentate co-
ordination mode of OAc .
which is significantly lower than
−1
Inhibition zone of the compound ðdiameterÞ
−
%Activity Index ¼
Inhibition zone of the standard ðdiameterÞ
5
6
. The existence in the composition of all complexes of lattice-
ꢁ
100
ð4Þ
coordinated water molecules is further confirmed by the existence
−1
of the broadband connection at 3477–3471 cm area of water mol-
ecules corresponding to ν(OH) [44,45].
2
.6. Catalytic oxidation of 3,5-di-tertbutylcatechol (3,5-DTBC) and the
−1
. The non-ligand bands occurring in the 579–573 and 493–491 cm
ranges have been assigned to ν(M ← O) and ν(M–N), respectively [46].
catecholase activity of the studied Cu(II) complex (3)
The Cu(II) complex solution (3) in methanol (0.1 mmol/L) was
treated in the presence of air with 100 mmol/L of 3.5-di-
tertbutylcatechol (3.5-DTBC). UV–Vis spectroscopy has pursued the
course of the reaction for the first 200 min. The 3,5-DTBC is being used
in most catecholases as a precursor-like behavior studies for synthetic
model complexes. The 3,5-di-tert-butyl-o-quinone (3,5-DTBQ)
3.2. Magnetic moments and electronic spectra
The free ligand (HL) and its Co(II), Ni(II) and Cu(II) complexes (1–3)
electronic spectra are observed in the wavelength range 200–800 nm in
3

H.A. Kiwaan, A.S. El-Mowafy and A.A. El-Bindary
Journal of Molecular Liquids 326 (2021) 115381
Table 1
Analytical and physical data of the ligand (HL) and its Co(II), Ni(II) and Cu(II) complexes (1–3).
Ω−
1
μ
eff
B.M.
Structure (Molecular Formula)
Mol.
Weight (°C)
M.P.
Yield
(%)
Color
Calcd. (Exp.) (%)
C
Λ
M
2
−1
cm mol
H
N
M
C
C
20
H
H
23
N
33CoN
5
O
4
S (HL)
10S (1) [Co(L)(CH
429.50
618.52
220
>300 75
80
Yellow 55.93 (55.85) 5.39 (5.33) 16.30 (16.25)
–
–
8
–
4.45
22
5
O
3
COO)(OH
2
)
2
]
Brown
42.72 (42.66) 5.38 (5.32) 11.32 (11.38) 9.53 (9.65)
2
2H O
C
C
22
H
H
35NiN
27CuN
5
O
11S (2) [Ni(L)(CH
3
COO)(OH
COO)]H
2
2
) ]3H
2
O
636.30
569.09
>300 70
>300 75
Green
Green
41.53 (41.64) 5.54 (5.48) 11.01 (11.11) 9.22 (9.28)
46.43 (46.48) 4.78 (4.71) 12.30 (12.38) 11.16 (11.09) 12
11
2.95
1.95
22
5
O
7
S (3) [Cu(L)(CH
3
2
O
the DMF solution. The free ligand exhibits two intense bands at 25316
−
1
and 22,883 cm due to π → π* transitions of the aromatic ring and
n → π* transitions of the C_O and C_N group, respectively [47].
These transitions are also to be found in the complex spectrum, but
they displayed a bathochromic change towards complex formation,
which assisted the coordination of the ligand with the metal ion.
The geometry of the complexes of metals (1–3) was obtained from
the electronic spectra and the magnet data of the complexes. The Co
(
II) complex (1) gave three electronic spectral bands at 10,940, 20,284
−
1
4
and 25,380 cm . These bands were assigned to the transitions T1g
4
4
4
4
4
(
F) → T2g(F)(ν
1
), T1g(F) → A2g(F)(ν
2
) and T1g(F) → T1g(P)(ν
3
), re-
spectively. The band location suggested that the Co(II) complex has an
octahedral geometry overall [48]. The magnetic moment value of the
Co(II) complex was recorded at 4.45 B.M. at room temperature, corre-
sponding to three unpaired electrons. Which is close to the normal
range for octahedral complex is (4.3–5.2 B.M.), hence indicative of
high spin octahedral geometry (Fig. 1) [49,50]. The spectrum of Ni(II)
M= Co(II) (X=H
2
O, n=2); Ni(II) (X=H O, n=3); Cu(II) (X=0, n=1).
2
Fig. 1. The proposed structure of the complexes (1–3).
−1
complex (2) exhibits three bands at 10,928, 20,833 and 25,380 cm
3
3
3
3
3
3
Table 2. The average crystallite size (Cs) and the dislocation density
assigned to A2g → T2g(ν
1 2
), A2g → T1g(F)(ν ) and A2g → T1g(P)
(
D) of the XRD pattern can be determined [54,55].
3
(ν ) transitions, respectively, in an octahedral geometry around Ni(II)
For the ligand, the measured values of Cs were found to be 19.61 nm.
ion [51]. The magnetic moment value (2.95 B.M.) falls within the
range recorded for octahedral geometry [52] around the Ni(II) ion
equal to two unpaired electrons. The standard range is (2.9–3.9 B.M),
for octahedral Ni(II) complex, suggesting high spin octahedral geometry
The measured D values are measured and the ligand is found to be
−3
−2
2
.6–10 nm . The calculated lattice parameters (a, b, c, α, β and γ),
inter-planar spacing, d, and Miller indices (hkl), of HL are listed in
Table 2.
(
Fig. 1). The spectrum of Cu(II) complex (3) displays bands at 10,964,
−1
2
2,988 and 25,510 cm . The first two bands may be assigned to
2
2
2
2
B
1g → A1g(ν
1
), B1g → B2g(F)(ν
2
) and the third band may be assigned
3.5. Molecular structure
to L → M charge-transfer, respectively. The magnetic moment observed
of the complex Cu(II) is 1.95 B.M. The square planar structure of this
complex indicates at room temperature within the range recorded for
one unpaired electron (Fig. 1) [38,47].
HL and its complexes (1–3) are described in the molecular struc-
tures (HOMO & LUMO) (Figs. 3 and 4) and the bond lengths and bond
2 2
M = Co(II) (X = H O, n = 2); Ni(II) (X = H O, n = 3); Cu(II) (X = 0,
n = 1).
1
13
3
.3. H NMR and C NMR spectra
The H NMR and 13C NMR spectra of a mix of enol-azo and hydrazine
1
6
tautomers of the ligand (HL) were recorded in DMSO‑d , internal TMS at
room temperature.
1
H NMR (500 MHz), δ (ppm) = 14.61 (\\C_N\\NH\\disappeared
O, 14.15 (s, 1H, NH)Hyd., 11.30 (s, 1H, NH)sulf., 7.69–8.02 (s, 4H,
Ar-H), 3.32 (s, 4H, 2CH ), 2.24 (s, 3H, CH ), 1.01 (s, 3H, CH ) [53].
C NMR (500 MHz), δ (ppm) = 27.9 (CH ), 30.1 (CH ), 51.9 (2CH
16.4 (Ar\\H), 129.8 (C_N), 131.0 (Ar-NH-N), 192.8 (C_O), 197.2
C_O).
with D
2
2
3
3
13
3
3
2
),
1
(
3.4. X-ray diffraction
The X-ray diffraction (XRD) pattern in powder form for the ligand
(
HL) and its complexes (1–3) are shown in Fig. 2. The plot suggests
many diffraction patterns that confirm the ligand polycrystalline
phase, but the complexes (1–3) are found to be amorphous. The opti-
mized crystal structure and the ligand space group are shown in
Fig. 2. X-ray diffraction patterns of ligand (HL).
4

H.A. Kiwaan, A.S. El-Mowafy and A.A. El-Bindary
Journal of Molecular Liquids 326 (2021) 115381
Table 2
angles of the chosen geometric parameters are described in Tables S1–
S4 (Supplementary material). The quantity chemical parameters mea-
sured are indicated in Table 3. The HOMO–LUMO energy gap (ΔE) is
an important stability index that is applied in many molecular systems
to establish theoretical models to describe structure and conformation
barriers. Additional quantum chemical was measured [41]. Table 3
reports the absolute electronegativity, χ, absolute hardness, η, chem-
ical potentials, Pi, absolute softness, ω, global softness, σ, global elec-
trophilicity, S and additional electronic charge, ΔNmax, which have
been calculated by the equations: χ = – (ELUMO + EHOMO)/2,
Crystallographic data of the ligand (HL).
System: Monoclinic Space group: P2
a = 8.5109 Å
b = 6.3072 Å
c = 5.5452 Å
α = 90°
β = 90.90° γ = 90°
Peak no.
2θ (°)(Obs.)
10.3620
14.0360
15.9310
18.9420
2θ(°)(Calc.)
10.3868
14.0301
15.9719
18.9510
Diff.
−0.0248
0.0059
−0.0409
−0.0090
(hkl)
1 0 0
0 1 0
0 0 1
1
2
3
4
1 0 1
0 1 1
4 0 1
5
6
7
21.3110
45.8950
50.3330
21.3198
45.8885
50.3166
−0.0088
0.0065
0.0164
2
η = (ELUMO – EHOMO)/2, σ = 1/η, Pi = – χ, S = 1/2η, ω = Pi /2η
and ΔNmax = – Pi/η [56].
1 0 3
Fig. 3. The highest occupied Molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of Ligand (HL) and its complexes (1–3).
5

H.A. Kiwaan, A.S. El-Mowafy and A.A. El-Bindary
Journal of Molecular Liquids 326 (2021) 115381
Fig. 4. The calculated molecular structures of ligand (HL) and its complexes (1–3).
A hard molecule has a large energy gap and a soft molecule has a
small energy gap. Soft molecules are more reactive than hard ones be-
cause they could easily offer electrons to an acceptor. In a complex for-
mation system, the ligand act as a Lewis base while the metal ion acts as
a Lewis acid. Accordingly, it is concluded that ligand with a proper value
σ have a good tendency to chelate metal ions effectively [56]. This is also
confirmed from the calculated chemical potential Pi for the ligand.
When the device obtains an additional electronic charge (ΔNmax)
from the atmosphere, the reactivity index tests the stabilization of elec-
tricity, and the electrophilicity index (χ) is positive. The ligand (HL) co-
ordinates to different metal ions through the carbonyl oxygen (O–11)
and deprotonated nitrogen atom (N−12) of hydrazine moiety. These
atoms carry a greater electronegative charge, confirming the active co-
ordination sites.
Table 3
The calculated quantum chemical parameters of HL and its complexes (1–3).
Σ eV −
1
-Pi eV
S eV −1
ω eV
ΔNma × eV
Comp.
-EHOMO eV
-ELUMO eV
ΔE eV
χ eV
η eV
HL
7.036
2.073
7.232
7.640
2.436
1.259
2.902
3.754
4.6
4.736
1.666
5.067
5.697
2.3
0.434
2.45
0.46
5.14
−4.736
−1.666
−5.067
−5.697
0.217
1.228
0.230
0.257
4.876
3.409
5.929
8.351
2.059
4.093
2.340
2.932
(1)
(2)
(3)
0.814
4.33
3.886
0.407
2.165
1.943
6

H.A. Kiwaan, A.S. El-Mowafy and A.A. El-Bindary
Journal of Molecular Liquids 326 (2021) 115381
Table 4
contact (electrostatic binding) or to major or minor grooves of DNA
Thermal analysis data for the ligand (HL) and its Co(II), Ni(II) and Cu(II) chelates (1–3).
[
59,60]. The ligand (HL) intrinsic binding constants (K
DNA complexes (1–3) were determined using Eq. (1) [61,62].
The K calculated value from the absorption spectral technique of
the ligand (HL) was measured by 6.67 × 10 M . K
from the spectral absorption system of the metal complexes (1, 2 and 3)
b
) and its CT-
Compound Temp. range Mass loss found (Calc.) Assignment
(
°C)
%
b
5
−1
b
results calculated
HL
30–330
31.65 (32.55)
28.14 (28.36)
40.15 (39.07)
5.86 (5.82)
15.77 (15.37)
40.3 (41.44)
38.07 (37.35)
8.46 (8.49)
15.17 (14.94)
57.14 (57.27)
19.23 (19.28)
2.57 (3.16)
19.93 (19.7)
45.21 (44.16)
32.16 (32.97)
Loss of C
Loss of CH
Loss of C13H
12
6
H
8
O
2
N
2
3
30–800
800
30–110
4
O
2
N
3
S
6
6
6
−1
>
were calculated as 4.42 × 10 , 6.22 × 10 and 2.39 × 10 M , respec-
tively. The complexes binding constants (1–3) are comparatively higher
than those of the ligand (HL), which encourages for their electrostatic or
groove binding.
(1)
(2)
(3)
Loss of 2H
2
O
1
3
>
10–360
60–800
800
Loss of CH COO + 2H O
3 2
Loss of C
7 22 5 3
H N O S
Loss of carbon atoms + CoO
30–110
1
3
>
30–120
1
3
>
Loss of 3H
Loss of CH
2
O
A viscosity experiment was carried out in relation to spectroscopic
performance, which is considered less ambiguous and the most impor-
tant DNA-binding model tests of the solution. The classical intercalative
mode of binding to DNA is indicated by a large increase in DNA viscosity
upon adding a complex. The increased level of viscosity that can affect
its DNA affinity is in the range of 3 > 1 > 2 (Fig. 5). The fact that the clas-
sical intercalation model allows the DNA helix to be lengthened as base
pairs are separated to accommodate the binding complexes, leading to
an increase in DNA viscosity, as with the action of the known DNA
intercalators, may explain this observation [40].
10–340
40–510
800
3 2
COO + 2H O
Loss of C16
Loss of carbon atoms+NiO
Loss of H
Loss of CH
Loss of C
Loss of carbon atoms+CuO
22 5 3
H N O S
2
O
20–360
60–650
800
3 4 5
COO + C H
7 17 5 3
H N O S
3.6. Thermal analyses
3.8. Catechol oxidation
In order to obtain useful information on the thermal stability of the
synthesized ligand (HL) and its chelates (1–3) and to investigate the ex-
istence of water molecules, TGA was carried out. The temperature
ranges and the proportion of mass loss of the ligand and its chelates
are described in Table 4. These weight reductions corresponded with
the loss for the chelates of uncoordinated water and organized mole-
cules. The results were consistent with data from elementary analysis.
The chelates showed phases in the decomposition method after exceed-
ing the dehydration point. The final weight losses are due to the decom-
position of the remaining carbon atoms and the residual metal oxide.
Additionally, Coast-Redfern [57] and Horowitz-Metzger [58] equa-
tions used to determine the thermodynamic parameters of the degrada-
tion processes. The data for the decomposition of activation energy,
enthalpy, entropy, and Gibbs free energy shift are described in the
Table 5.
The synthesized copper(II) complex (3) has been tested in oxidation
of 3,5-Di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butyl-o-quinone
3,5-DTBQ) for their catalytic activity. Because of the complex's strong
(
solubility, the substrate (3,5-DTBC) and its product (3,5-DTBQ) in this
solvent, the reactivity studies were performed in methanol solution.
The substance (3,5-DTBQ) is stable and strongly absorbed at the stage
−1
−1
of λmax = 400 nm (ε = 1900 M cm in methanol) [63]. Therefore,
the activity and reaction rates can be measured using electronic spec-
troscopy following the appearance of maximum absorption of quinone
(
Fig. 6). The unusually high stability observed at room temperature for
o-quinone means that a single reaction mechanism is being followed
and that there is no further oxidative cleavage of the generated o-
quinone.
3
3
.9. Biological activity
3.7. DNA binding studies
.9.1. Antimicrobial activity
DNA is the classic pharmacological target for anticancer agents de-
The antifungal and anti-bacterial activity against Candida albicans,
pendent on metals. Consequently, many techniques of characterization
have been used to research ligand (HL) and its complexes (1–3) associ-
ations with CT-DNA.
Escherichia coli, and Staphylococcus aureus of ethanol extracts of HL
and its complexes (1–3) is calculated by the well-diffusion process
(Table 6). We can simply remember that, with the exception of complex
(1), all the compounds displayed no antibacterial activity against
Escherichia coli (inhibition zone of 10 mm). All the compounds under in-
vestigation have antibacterial activity against Staphylococcus aureus
with inhibition zones (9, 12, 11 mm of HL, (1) and (2), respectively) ex-
cept complex (3) has no activity (Fig. 7). All the compounds, on the
other hand, showed no antifungal activity against Candida albicans
other than complex (2) (12 mm inhibition zone) [64].
The electronic spectra of the compounds displayed a band at 395,
3
94, 394 and 392 nm for HL and complexes 1, 2, and 3, respectively.
These bands responsible for the transition from π-π* encountered
hypochromism along with a minor wavelength change during the addi-
tion of increased CT-DNA concentration, the intrinsic binding constant
value of the compounds was used to find out. These spectral character-
istics suggest either that the ligands and complexes bind to external
Table 5
The ligand (HL) kinetic parameters and its complexes (1–3).
Comp.
Temp. (°C)
Method
Parameters
R2
Ea (kJ.mol−1)
A (s−1
)
–ΔS* (J.mol−1.K−1
)
ΔH* (kJ.mol−1
)
ΔG* (kJ.mol−1
)
3
3
2
HL
30–330
CR
HM
CR
HM
CR
HM
CR
15.2
23.8
32.7
41.9
18.7
27.01
28.7
40.05
9.34 × 10−
4.38 × 10−
0.880
65.9
0.104
14.8
0.123
36.4
2.87 × 10
2.93 × 10
2.50 × 10
2.14 × 10
2.86 × 10
2.45 × 10
2.66 × 10
2.19 × 10
11.45
20.12
28.49
37.67
14.58
22.87
24.5
271
153
155
146
148
145
161
148
0.75282
0.9117
0.9869
0.96694
0.86771
0.8883
0.8446
0.920
2
2
(1)
(2)
(3)
110–360
110–340
120–360
2
2
2
2
2
HM
35.7
7

H.A. Kiwaan, A.S. El-Mowafy and A.A. El-Bindary
Journal of Molecular Liquids 326 (2021) 115381
Table 6
Mean inhibition zone in mm produced against Candida albicans, Staphylococcus aureus and
Escherichia coli on a range of pathogenic microorganism's results from anti-bacterial and
anti-fungal activity of ethanol extracts of HL and its complexes (1–3).
Sample code tested microorganisms
HL
(1)
(2)
(3)
Control
Fungi
Candida albicans
Ketoconazole
20
NA
NA
12
NA
RCMB 005003 (1) ATCC 10231
Gram Positive Bacteria:
Staphylococcus aureus ATCC 25923
Gram Negatvie Bacteria:
Escherichia coli ATCC 25922
Gentamycin
24
Gentamycin
30
9
12
10
11
NA
NA
NA
NA
Using the diffusion agar method, the test was conducted. Well diameter: 6.0 mm (100 μl
was tested), RCMB: Mycology and Biotechnology Regional Center.
The sample was tested at 10 mg/ml concentration.
(
i) MCF-7 (breast cancer) and (ii) HepG-2 (hepatocellular carcinoma)
by using vinblastine and colchicine as the reference compounds (refer-
ring to Figs. 8 and 9) [69,70]. Table 7 describes of the measured IC50
values, for the tested compounds. Such findings showed that the com-
plex (2) (IC50 = 192.0 ± 6.9, and 204 ± 7.3 μg/mL) is exhibiting non-
In contrast with the Colchicine toxicity against the two cell lines MCF-
Fig. 5. Effect of increasing amounts of HL and its complexes (1–3) on the relative viscosity
of DNA at 25 °C.
7
0
and HepG-2, respectively, (IC50 = 16.8 ± 0.02, and 10.0 ± 0.
2 μg/mL). Cu(II) complex (3) exhibiting good cytotoxic activity against
MCF-7 and HePG-2 cell lines with IC50 = 25.9 ± 2.8 and 17.2 ±
.4 μg/mL, respectively. The other complexes also demonstrated
2
overlooked toxicity against the two MCF-7 and HepG-2 cell lines. As
established, negative outcomes in therapeutic fields have the same sig-
nificance as positive outcomes, so we reported these outcomes when
performing negatively.
3.9.3. In vitro anti-oxidant activity
In vitro anti-oxidant tests are relatively straightforward to perform
using free radical traps, Compared to other test models, the DPPH scav-
enging method has the advantage of being fast, simple and inexpensive
[
71]. The DPPH assay is based on the measurement of decreases in molar
absorptivity of DPPH at 515 nm after reaction with HL and its complexes
1–3) [72,73]. Results of anti-oxidant activity and compounds are
(
contrasted as a reference standard with ascorbic acid and defined in
the Table 7. We can rate the DPPH radical scavenging potential of the
tested complexes in the following order on the basis of these findings:
HL > 1 > 2 > 3, as clearly shown in Fig. 10.
Fig. 6. UV–Vis spectral changes recorded for the reaction of copper(II) complex (1)
3.10. Molecular docking study
(0.1 mmol/L) with 3,5-DTBC (10 mmol/L) in methanol at 25 °C. Inset shows the course
of the absorbance at 400 nm with time (in min).
The aim of molecular docking is to achieve optimum conformation
with relative orientation between the protein and the drug such that
the free energy of the overall system is reduced [74]. In this thesis, we
used ligand molecular docking (HL) in complex COVID-19 (5REA)
with breast cancer mutant (3hb5) and crystal structure of SARS-CoV-2
main protease. The docking analysis demonstrated a favorable relation-
ship between ligand and breast cancer mutant 3hb5 and SARS-CoV-2 in
Figs. 11 and 12 and the calculated energy is listed in Table 8.
According to the findings obtained in this analysis, the HB plot curve
indicates that there were interactions of the ligand (HL). Protein bind-
ing with interactions of the hydrogen bond and decomposed energies
of interaction in kCal/mol between the ligand with the ligand breast
cancer mutant (3hb5) and the crystal structure of the main protease
SARS-CoV-2 in complex COVID-19 (5REA). The measured quality is fa-
The ligand (HL) on the bacterial and fungal species was found to
possess very less or almost no activity. Based on the principle of Over-
tone [65] and the chelation theory of Tweedy, the increased activity of
the complexes (1–3) over its ligand can be clarified [66]. The cell perme-
ability principle of Overtone enables only lipid soluble substances to
move through the lipid membrane surrounding the cell. Increasing the
lipophilicity of the complexes helps to permeate the cells, thereby lim-
iting protein synthesis and disrupting cell respiration [67]. There were
different behaviors of the complexes against different bacteria and
fungi, and the following pattern was also different. This can be attrib-
uted to a variety of variables, such as the size and function of the
metal ion and the dynamic, complex geometry and solubility, dipole
moment, microbial cell impermeability, etc. [68].
vorable where, when available, the K
was compared to the experimental K
i
value estimated by Auto Dock
value and the free energy of
i
Gibbs is negative. Based on this evidence, we can also suggest that li-
gand interaction with the mutant breast cancer (3hb5) and the crystal
structure of SARS-CoV-2 key protease in complex COVID-19 (5REA)
may be probable. 2D graph curves for ligand docking are seen in
3
.9.2. In vitro cytotoxicity study
The cytotoxic activity of HL and its complexes (1–3) is measured
against two separate human cell lines for in vitro anti-tumor activity:
8

H.A. Kiwaan, A.S. El-Mowafy and A.A. El-Bindary
Journal of Molecular Liquids 326 (2021) 115381
Fig. 7. Antibacterial activity data of ligand (HL) and its complexes (1–3).
Table 7
Cytotoxic activity of HL and its complexes (1–3) against the cell lines MCF-7 and HepG-2
and the scavenging activity of DPPH.
Compound
IC50 (μg/mL)
MCF-7
HepG-2
DPPH
HL
61.1 ± 3.6
56.5 ± 3.1
192.0 ± 6.9
25.9 ± 2.8
16.8 ± 0.02
6.2 ± 0.02
–
90.1 ± 4.2
31.0 ± 2.9
204 ± 7.3
17.2 ± 2.4
10.0 ± 0.02
4.4 ± 0.02
–
153 ± 8.21
87.63 ± 4.35
82.5 ± 3.7
39.48 ± 2.64
–
(
(
(
1)
2)
3)
Colchicine
Vinblastine
Ascorbic acid
–
12.5 ± 0.7
The findings are described as (Mean ± SD).
bonding [75]. This role gives them the ability to be effective inhibitors of
protein binding and will assist in the growth of increased inhibitory
compounds. The ligand HL showed binding energy −9.05 and −5.50
kCal/mol for 3hb5 and 5REA, respectively using H-bond, electrostatic
and van der Waals interact ions. It was deciphered that ligand (HL)
may be promising inhibitors of 3hb5 and 5REA focused on dynamic
scoring and interactions with the residue and binding capability of the
active site.
Fig. 8. Evaluation of cytotoxicity against MCF-7 cell line of ligand (HL) and its complexes
(1–3).
Figs. 13 and 14. This connection may activate the ligand's energy inter-
actions with apoptosis in cancer cells. The compound characteristics
were expressed with the inclusion of active sites available for hydrogen
Fig. 9. Evaluation of cytotoxicity against HepG-2 cell line of ligand (HL) and its complexes
Fig. 10. Evaluation of Antioxidant Activity using DPPH scavenging of ligand (HL) and its
complexes (1–3).
(1–3).
9

H.A. Kiwaan, A.S. El-Mowafy and A.A. El-Bindary
Journal of Molecular Liquids 326 (2021) 115381
Fig. 11. The ligand (HL) [green in (a) and blue in (b)] with breast cancer mutant 3hb5 receptor (the reader is referred to the online version of this article for a key to the references to color
in this figure). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article).
Fig. 12. The ligand (HL) (green in (a) and blue in (b)) in interaction with crystal structure of SARS-CoV-2 main protease in complex COVID-19 (5REA). (For interpretation of the references
to color in this figure legend, the reader is referred to the web version of this article).
Table 8
Energy values obtained in ligand (HL) docking measurements with breast cancer mutant (3hb5) receptor and SARS-CoV-2 principal protease crystal structure in complex COVID-19
(5REA).
Receptor
Gibbs. free energy of binding
kCal/mol)
inhibition constant
(K ) (uM)
vdW+H bond+ desolv energy
(kCal/mol)
Electrostatic energy
(kCal/mol)
Total intermolecular energy
(kCal/mol)
Interact
surface
(
i
3
5
hb5
REA
−9.05
−5.50
232.62
92.54
−9.40
−6.01
−0.88
−0.31
−10.28
−6.31
1063.395
668.442
10

H.A. Kiwaan, A.S. El-Mowafy and A.A. El-Bindary
Journal of Molecular Liquids 326 (2021) 115381
Fig. 13. 2D plot of interaction between ligand HL with breast cancer mutant (3hb5) receptor.
4
. Conclusion
complexes binding constants (1–3) are comparatively higher than those
of the ligand (HL), which encourages for their electrostatic or groove
binding. Molecular docking was used to predict 3hb5 and 5REA receptor
bonding between the ligand (HL). The ligand and its complexes have
been tested for their biological activity.
This paper reports the ligand (HL) and its Co(II), Ni(II) and Cu(II) com-
plexes (1–3) on the synthesis, characterization, DNA binding and biolog-
ical activity. Based on spectroscopic, magnetic, thermal and theoretical
data; the coordination geometry of the complexes Co(II) and Ni(II) is oc-
tahedral where the complex Cu(II) is tetrahedral. The ligand behaves as a
monobasic bidentate and occurs as a keto-hydrazone bonded internally
with hydrogen instead of the form of azo-enol. The HOMO and LUMO or-
bital energies of HL and their complexes has negative values, and complex
Data availability statement
The data supporting the results of this study shall, upon appropriate
request, be available from the relevant author.
(1) is stable than the other complexes. The thermo gravimetric study of
the compounds indicates that the values of decomposition activation en-
ergies (Ea) which calculated by Horowitz-Metzger equation are found to
be 23.8 kJ/mol for the ligand (HL) and it is noticed that the Ea values are
Declaration of Competing Interest
4
1.90, 27.01 and 40.05 kJ/mol for the complexes 1, 2 and 3, respectively.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
By absorption spectra and viscosity measurements the calf thymus DNA
binding behavior of the ligand (HL) and its complexes was studied. The
11

H.A. Kiwaan, A.S. El-Mowafy and A.A. El-Bindary
Journal of Molecular Liquids 326 (2021) 115381
Fig. 14. 2D plot of interaction between ligand HL with Crystal Structure of SARS-CoV-2 main protease in complex COVID-19 (5REA).
[
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Appendix A. Supplementary data
2
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.molliq.2021.115381.
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