Synthesis, Spectroscopic Characterization, Molecular Docking, and Evaluation of Antibacterial Potential of Transition Metal Complexes Obtained Using Triazole Chelating Ligand

Article abstract of DOI:10.1155/2020/1548641

Mononuclear chelates of Ni(II), Co(II), Fe(III), Cd(II), and Cu(II) derived from triazole novel tridentate ligands were prepared and characterized by different spectroscopic methods. The metal to ligand ratio was 1: 2, which was revealed by elemental anal

Full text of DOI:10.1155/2020/1548641

Hindawi
Journal of Chemistry
Volume 2020, Article ID 1548641, 12 pages
https://doi.org/10.1155/2020/1548641
Research Article
Synthesis, Spectroscopic Characterization, Molecular Docking,
and Evaluation of Antibacterial Potential of Transition Metal
Complexes Obtained Using Triazole Chelating Ligand
,
4
NajlaaS.Al-Radadi ,1 EhabM.Zayed,2 GehadG.Mohamed,3 andHayamA.AbdElSalam2
1Department of Chemistry, Faculty of Science, Taibah University, Al-Madinah Al-Monawara 14177,
P. O. Box 30002, Saudi Arabia
2Department of Green Chemistry, National Research Centre, Dokki, Giza 12622, Egypt
3Department of Chemistry, Faculty of Science, Cairo University, Giza 12613, Egypt
4Egypt Nanotechnology Center, Cairo University, El-Sheikh Zayed, 6th October 12588, Giza, Egypt
Correspondence should be addressed to Najlaa S. Al-Radadi; nsa@taibahu.edu.sa
Received 26 September 2019; Revised 19 December 2019; Accepted 14 January 2020; Published 24 February 2020
Academic Editor: Radhey Srivastava
Copyright © 2020 Najlaa S. Al-Radadi et al. )is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
Mononuclear chelates of Ni(II), Co(II), Fe(III), Cd(II), and Cu(II) derived from triazole novel tridentate ligands were prepared
and characterized by different spectroscopic methods. )e metal to ligand ratio was 1 : 2, which was revealed by elemental analysis.
All the complexes were electrolytic in nature as suggested by the conductivity measurements. IR pointed out that the coordination
of the triazole ligand toward the metal ions was carried out through N amino and S thiophenolic atoms. )e complexes were found
to have octahedral geometry, and their thermal stability was also studied. )e XRD spectrum of Co(II) and Fe(III) complexes
concluded their crystalline structure. )e parent ligand and its chelates were investigated for antimicrobial potential. Bioassay of
all triazole complexes showed increased activity as compared to that of the ligand. )e complexes having Ni(II), Co(II), and Cu(II)
ions as metal center exhibited superior antibacterial activity in opposition to Gram-positive (B. subtilis and S. pyogenes) and
Gram-negative (E. coli and P. vulgaris) bacterium as compared to standard.
1,2,4-triazole ligands has good application in recent years
[10–14]. A lot of transition metal complexes of 1,2,4-tri-
azoles substituted can be prepared [15]. )e 1,2,4-triazoles
have been explored for linking ligands among transition
metal ions. )e target for the linking can be from first N to
second N (N1 to N2) atoms. In recent years, preparing
coordination ligands using 1,2,4-triazole moiety acquired
great attention [16]. A variety of derivatives of 1,2,4-triazole
in addition to its own complexes was reported as an ex-
cellent compound for constructing many metal coordi-
nation polymers [17–21]. Fatty acids containing nitrogen
derivatives have good attention recently because of their
high biological activity [22].
1. Introduction
)e complexes exhibiting photoluminescence acquire much
attention and interest, being utilized for different applica-
tions including biological probes, oxygen sensors, and
phosphorescent dopants in optoelectronic apparatus [1, 2].
In modern coordination chemistry, compounds which
have cyclic imines are of great importance in forming stable
complexes with some transition metal ions [3, 4]. Triazole
compounds with some transition metals showed significant
antibacterial, antitumor, and antifungal activity besides
effective antiviral agents [5–8]. We find the metal com-
plexes of ligands which have S,N-heterocycles promising
for enhanced biological activities compared to the native
ligand [9]. )e preparation of metal complexes containing
From the above discussion and mentioned facts, our idea
was to enhance access to pharmacologically interesting

2
Journal of Chemistry
complexes depending on their derivatives with selected
metallic cations considered as important feed stocks for the
chemical industry with promise of potential advance. In
present study we discuss the preparation, characterization,
and antibacterial study relating to Ni(II), Cu(II), Fe(III),
Cd(II), and Co(II) complexes of 4-amino-5-stearyl-1,2,4-
triazole-3-thiol (HL). In the current work, the synthesis of
bidentate triazole ligand and its monomeric metal com-
plexes in the company relating to Cd(II), Co(II), Fe(III),
Cu(II), and Ni(II) ions is demonstrated. )e synthesized
complexes were analyzed through state-of-the-art physico-
chemical techniques including NMR, IR, and EDS and
screened for antibacterial potential against some pathogenic
species.
(15 cm3) was added. Mixed solution was refluxed using a
water bath as long as 3 h whereupon the complexes were
going to precipitate. )e collected precipitate was filtered,
clean washing was done using ethanol and diethyl ether, and
it was vacuum-dried for later experiments.
2.3. [Cu(HL)2(H2O)2]Cl2. Yield 75%; brown solid, Anal.
Calcd. for C38H80Cl2CuN8O2S2 (%): C, 51.90; H, 8.85; N,
12.88; S, 6.95; Cu, 6.75. Found (%): C, 51.88; H, 9.17; N,
12.74; S, 7.29; M, 7.22. IR (], cm− 1): 2755 sh (C-SH), 1630 sh
(N-NH2), 830 sh coordinated H2O, 566 s (Cu-O), 447s (Cu-
N), 430 s (Cu-S).
2.4. [Cd(HL)2(H2O)2]Cl2. Yield 85%; dark green, Anal.
Calcd. for C38H80CdCl2N8O2S2 (%): C, 48.88; H, 8.23; N,
12.45; S, 6.55; Cu, 11.76. Found (%): C, 49.15; H, 8.68; N,
12.07; S, 6.91; M, 12.11. IR (], cm− 1): 2770 sh (C-SH), 1634sh
(N-NH2), 740 s coordinated H2O, 565 s (Cd-O), 465 w (Cd-
N), 438 s (Cd-S).
2. Materials and Methods
All analytical grade reagents having utmost purity were
utilized in this work. )e ranges of chemicals were
CuCl2·2H2O procured from Sigma; COCl2·6H2O,
CdCl2·2H2O, and NiCl2·6H2O from BDH; and FeCl3·6H2O
from Prolabo. )e organic solvents were absolute ethyl al-
cohol and dimethylformamide (DMF), and they were ob-
served spectroscopically and cleaned using BDH. Every
preparation was made in double-distilled water.
2.5. [Fe(HL)2(H2O)2]Cl3. Yield 87%; green, Anal. Calcd. for
C38H80FeCl3N8O2S2 (%): C, 50.13; H, 8.63; N, 11.54; S, 6.62;
Fe, 5.86. Found (%): C, 50.30; H, 8.89; N, 12.35; S, 7.07; M,
6.15. IR (], cm− 1): 2730 sh (C-SH), 1640 s (N-NH2), 766 sh
coordinated H2O, 560 s (Fe-O), 525 s (Fe-N), 462 w (Fe-S).
2.1. Instrumentation. A Jenway 4010 conductivity meter was
utilized to record the molar conductance of solid chelates in
DMF, while the solid reflectance spectra were recorded using
a Shimadzu 3101pc spectrophotometer.
2.6. [Ni(HL)2(H2O)2]Cl2. Yield 82%; pale brown, Anal.
Calcd. for C38H80NiCl2N8O2S2 (%): C, 51.69; H, 8.88; N,
13.71; S, 6.90; Ni, 6.45. Found (%): C, 52.17; H, 9.22; N, 12.81;
S, 7.33; Ni, 6.71. IR (], cm− 1): 2780 sh (C-SH), 1625 sh (N-
NH2), 835 w coordinated H2O, 580 s (Ni-O), 530 s (Ni-N),
446 sh (Ni-S).
l
Extensive H-NMR spectra beginning 0 to 15 ppm
recorded on Varian-Oxford Mercury were operated at
300 MHz. )e samples for lH-NMR spectra were prepared in
DMSod6 (deuterated dimethylsulfoxide). For powder XRD
analysis, BV XRD spectrometer from Philips Analytical type
PW 1840 controlled at 40 kV plus 25 mA applying 2000 W
radiation via copper anode was used. Faraday method was
applied for molar magnetic susceptibility analysis of pow-
dered samples. Pascal’s constant diamagnetic corrections
were done while calibrations were performed using Hg
[Co(SCN)4]. FTIR spectrum was taken among
4000–200 cm− 1 using PerkinElmer FTIR type 1650 spec-
trophotometer by preparing KBr pellets.
2.7. [Co(HL)2(H2O)2]Cl2. Yield 63%; dark blue, Anal. Calcd.
for C38H80CoCl2N8O2S2 (%): C, 51.79; H, 9.13; N, 12.46; S,
7.12; Ni, 6.58. Found (%): C, 52.16; H, 9.21; N, 12.81; S, 7.33;
Co, 6.73. IR (], cm− 1): 2760sh (C-SH), 1650 br (N-NH2),
835 s coordinated H2O, 575 m (Co-O), 490 s (Co-N), 427 w
(Co-S).
CHNS-932 (LECO) Vario elemental analyzer was used
to analyze the separated solid chelates in duplicate for
presence of C, H, N, S, and Cl at Microanalytical Center,
Cairo University.
Mass spectra were taken on MS-5988 GS-MS HP
spectrometer controlled on 70 eV via EI technique at Mi-
croanalytical Center, Cairo University. Considering thermal
analyses (TG, DTG, and DTA) Shimadzu TG-60 H simul-
taneous DTA-TG apparatus was used in dynamic nitrogen
(20 mL·min− 1) atmosphere having 10°C·min− 1 rate of
heating.
2.8. Molecular Modeling Methodology. )e optimized
structural geometry of the triazole ligand was identified
using Gaussian 09 software by applying DFT/B3LYP
process having range of base sets [23]. )e Gaussian files
obtained through this method were visualized using Gauss-
View molecular visualization program [24]. )ey were
calculated by using HOMO-LUMO energies; the DFT/
B3LYP quantum chemical parameter was calculated in
accordance with the numerical pattern appearing in gas
phase in the view of the compounds. Additionally, the other
parameters of optimized structures such as considerable
bond lengths, excitation energies, oscillator strengths, and
efficient charges required for coordinating functional
groups were figured out.
2.2. Metal Complexes Synthesis. To a solution of the triazole
ligand (0.3 g, 0.847 mM) in ethanol (30 cm3), a solution
containing metal (II)/(III) chloride (0.847 mM) in ethanol

Journal of Chemistry
Compound
3
Table 1: Elemental and physical data of triazole ligand and its metal complexes.
% found (calcd.)
μeff (B.M) Λ Ω ·mol− l·cm2
− 1
m
C
H
N
S
M
. . .
5.86 (6.18)
6.58 (6.75)
6.45 (6.75)
6.75 (7.23)
HL
64.12 (64.33) 10.45 (10.80) 15.58 (15.80) 8.75 (9.04)
. . .
92.20
5.30
. . .
92.20
130
120
43.10
124
[Fe(HL)2(H2O)2]Cl3
[Co(HL)2(H2O)2]Cl2
[Ni(HL)2(H2O)2]Cl2
[Cu(HL)2(H2O)2]Cl2
50.13 (50.30)
51.79 (52.17)
51.69 (52.17)
51.90 (51.91)
8.63 (8.83)
9.13 (9.15)
8.88 (9.15)
8.85 (9.11)
8.23 (8.63)
11.54 (12.36) 6.62 (7.06)
12.46 (12.81)
13.71 (12.81)
12.88 (12.75) 6.95 (7.29)
12.45 (12.08) 6.55 (6.90) 11.76 (12.08)
7.12 (7.32)
6.90 (7.32)
3.60
1.70
[Cd(HL)2(H2O)2]Cl2 48.88 (49.19)
Diama
2.9. Molecular Docking. Docking computations were per-
formed using AutoDock tools 4.2 by applying Gasteiger
partial charges incorporated into the designed drug (li-
gand) atoms. Depending on the protein-ligand interaction
pattern, the calculations were carried out. Hydrogen atoms
with nonpolar nature were conjoined, and bonds which can
be rotatable were clarified. Subsequent to the incorporation
of fundamental hydrogen atoms, Kollman unified atom
style charges, and salvation factors, the AutoDock tools
were pertained [25, 26]. Electrostatic and van der Waals
terms were determined using distance dependent dielectric
functions and AutoDock parameter set, respectively. For
simulative docking, Lamarckian genetic algorithm and
Solis and Wets local search methodology were applied [27].
Incidentally, properties of the ligand molecule like torsions,
primary position, and orientation were positioned. )e
entire rotatable torsions were excluded throughout docking
experiment. Ten diverse runs were performed for every
docking experiment, which was positioned toward block
subsequent to decisive 250,000 energy assessments while
the size was set up to 150. During the experiment, torsion
3. Results and Discussion
)e elemental analyses of the triazole-thiol and its mono-
meric chelates were determined, showed good support with
the proposed structures of the ligand and its chelates, and
have been reported in Table 1.
3.1. Infrared Spectral Analysis of Triazole Ligand and
Complexes. IR spectrum of ligand showed an intense signal
at 2820 cm− 1 pointing out the presence of thiophenolic
group (–SH). )is sharp signal was shifted in the spectra of
complexes (2730–2780 cm− 1), indicting that the thio-
phenolic –SH group still protonated and was involved in
coordination with metal ions [28]. )e ligand showed an
intense band due to stretching vibrations of amino group at
3200–3240 cm− 1. )is band was embedded within the -OH
stretching vibration of coordinated water molecules at
3250–3500 cm− 1. )e bending vibration of the amino group
at 1608 cm− 1 was observed consistently with the amino
absorption of free triazole ligand [29]. )is latter peak was
transferred to 1625–1650 cm− 1 for spectra of metal chelates,
confirming the coordination of amino group to metal ions
[29].
˚
and translational step of 5 and 0.2 A were utilized,
respectively.
Besides the above bands, the IR bands, due to triazole
ring systems between 1520 and 1566 cm− 1 which are almost
unaffected in the complexes, have been assigned to C�N.
)ese facts were further confirmed by occurrence of some
new signals (M–N) at 447–530 cm− 1, (M–S) at
427–462 cm− 1, and (M–O) at 565–580 cm− 1 in the spectra of
complexes [29, 30]. Bands at 745–780 cm− 1 may be attrib-
uted to rocking and wagging modes of the coordinated
water. It was concluded from the significant shift of free
ligand (NH2) to lower wave number side, with increased
wave number for thiophenolic (C–S) stretching band in
complexes, that bonding of the ligand to metal ion is through
thiophenolic sulfur and amino nitrogen.
2.10. Biological Activity. )e biological activity of triazole
and its corresponding chelates was evaluated using agar
well diffusion method against B. subtilis (ATCC6635), S.
pyogenes(ATCC443) (Gram+); E. coli (ATCC25922), P.
vulgaris(ATCC33420) (Gram− ) bacterium. Total 500 μL
spore solution with 10− 6–10− 7 spores mL− 1 concentration
was inoculated very soon prior to solidification for every
examined organism in sterilized agar preceded with
pouring into sterile Petri dishes, having 45 mm radius,
later permitted for solidification. )en, a sterile cork borer
with 3 mm radius was utilized for creating three wells at
different locations to every agar solidified Petri dish. To
each well, 100 mg·mL− 1 experimental compounds were
mixed with DMF poured in the sterile Petri plates and then
allowed for 48 h incubation on 37°C. )e control was
prepared using 0.l mL DMF at the same conditions. )e
zone of inhibition was calculated for control and experi-
mental Petri dish containing metal complexes or free
triazole ligand. For determination of antibacterial activity
of these compounds, the experiment was performed in
triplicate. )e IC50 (the lowest concentration of compound
capable of inhibiting 50% growth) was calculated from
MIC measurements.
3.2. lH NMR Analysis of Ligand and Its Monomeric
l
Complexes. H NMR spectra of ligand in DMSO exhibited a
singlet at δ � 13.34 ppm for thiophenolic –SH, singlet at
δ � 5.45 ppm due to NH2 group, multiplets in the region
δ � 1.19–2.46 ppm due to -CH2 groups, and CH3 singlet at
l
δ � 0.82 ppm. H NMR spectrum of Cd(II) complex in
DMSO showed small intensity peak at δ � 13.34 ppm cor-
responding to the presence of thiophenolic –SH, thus in-
dicating remaining of hydrogen and coordination of ligand
to metal through thiophenolic SH group. )is finding

4
Journal of Chemistry
Table 2: )ermoanalytical results (TG and DTG) of triazole ligand and its metal complexes.
Mass loss total
mass loss calcd
(estim) %
28.24 (29.47)
71.77 (70.54) 100.1
(100.1)
TG range DTGmax
∗
Compound
n
Assignment
Residue
—
DTA (°C)
(°C)
(°C)
24–200
162, 181
2
(i) Loss of C7H16
(ii) Loss of C12
H22N4S
60(− ), 72(+), 99(− ), 110(+),
186(− ), 219(− )
HL
200–325 204, 237
2
(i) Loss of 3HCl
and C25H54
(ii) Loss of
25–300
267
1
50.91 (51.44)
55(− ), 67(+), 152(− ), 235(+),
280(+), 500(− ), 688(− ),
711(− )
[Fe(HL)2(H2O)2]Cl3
½Fe2O3
CoO
40.49 (39.73) 91.40
(91.17)
300–780
381, 573
2
0.5(H2O),
C13H25N8S2
(i) Loss of 2HCl,
CH4, and C3H9
(ii) Loss of H2O and
C20H37
(iii) Loss of
C14H30N8S2
(i) Loss of 2HCl,
CH4, and C5H13
(ii) Loss of C12H25
(iii) Loss of H2O
and C7H11
(iv) Loss of
C13H23N8S2
(i) Loss of CH4 and
2HCl
(ii) Loss of H2O and
C31H61
(iii) Loss of
C6H13N8S2
(i) Loss of CH4,
2HCl, and C8H19
(ii) Loss of H2O and
C11H18
25–250
250–400
400–680
150
359
410
1
1
1
15.67 (15.16)
33.75 (33.28)
80(+), 176(− ), 199(− ),
263(− ), 350(+), 415(− )
[Co(HL)2(H2O)2]Cl2
[Ni(HL)2(H2O)2]Cl2
[Cu(HL)2(H2O)2]Cl2
[Cd(HL)2(H2O)2]Cl2
44.62 (43.98) 94.04
(92.42)
25–200
200–250
250–350
58
1
1
1
18.33 (18.93)
19.82 (19.28)
12.95 (13.36)
241
287
40(− ), 63(+), 115(− ), 125(+),
208(− ), 286(− ), 345(− ),
370(+), 415(− )
NiO
CuO
CdO
41.60 (39.95) 92.70
(91.52)
350–600
363
1
25–150
150–350
350–650
73,110
541
2
1
1
10.36 (9.04)
81(+), 95(− ), 114(+), 237(− ),
273(+), 369(− ), 399(+)
51.11 (51.49)
29.71 (30.35) 91.85
(90.88)
393
25–250
233
1
20.01 (22.47)
250–400
400–500
500–800
311
442
630
1
1
1
18.12 (17.43)
100(+), 234(− ), 306(+),
456(+), 523(+)
9.06 (9.01)
37.43 (37.31) 84.62
(86.22)
(iii) Loss of C6H12
(iv) Loss of
C12H27N8S2
confirmed the IR data. )e peak due to NH2 group was
found in the Cd(II) complex at 5.35 ppm. )is shift con-
firmed the participation of NH2 in coordination with the
metal ions. Peaks corresponding to -CH3 and -CH2 groups
are also present in spectrum of Cd(II) complex without any
change. Retention of peaks without any formal change in-
dicated the preservation of the formal structure of ligand
without any deformation [31].
)is analysis also helped to determine the thermal sta-
bility of the new synthesized complexes. By controlling
conditions such as temperature starting from atmo-
spheric temperature to ∼1000°C under N2 gas and con-
trolling the heating rates properly on 10°C min-l, weight
loss was calculated. )ermogravimetric and DTA data are
provided in Table 2.
)e TG curves of Fe(III) and Co(II) chelates pointed out
the first step decomposition around 25–300 and 25–250°C
with 51.44% mass loss (calculated 50.9 l%) and 15.16 mass loss
(calculated 15.67%), indicating the 1oss of 3HC1 and C25H54,
and 2HC1, CH4, and C3H9 molecules, respectively. )e Fe(III)
and Co(II) complexes showed weight loss of 39.73% (calcu-
lated 40.49%) and 78.37% (calculated 77.26%) at temperature
ranges of 300–780 and 250–680°C, which correspond to the
removal of remaining ligand molecules, respectively.
3.3. Molar Conductance Study. )e molar conductance
values measured in DMF solution were found to be 43.10,
− 1
130, 124, 120, and 92.20 Ω ·mol− lcm2 for Cu(II), Co(II),
Cd(II), Ni(II), and Fe(III) complexes, respectively. Re-
spective molar conductance values confirmed that the
complexes were electrolytes [32].
A weight loss of 18.93% (calculated 18.33%) was ob-
served in the TG curve of Ni(II) complex in 25 and 200°C
temperature range which suggested e1imination about
2HC1, CH4, and part of the organic 1igand (C5H13). )e
weight losses of 72.59% (calculated 74.37%) at temperature
3.4. ?ermogravimetric Analysis. For determination of the
general scheme for thermal decomposition of chelates
and evaluation of the presence of water molecule either
inside or outside the central metal ion, thermogravi-
metric analysis (TG, DTG, and DTA) was performed.

Journal of Chemistry
5
range 200–600°C corresponded to the removal of the
remaining ligand molecules.
3.7. X-Ray Diffraction Analysis (Powder-XRD). )e syn-
thesized Fe(III) and Co(II) complexes were found to have a
crystalline character [37, 38].
Simi1ar1y at a temperature of 25–150°C and 25–250°C,
CH4 and 2HC1 or CH4, 2HC1, and C8H19 moieties were
eliminated corresponding to a weight loss of 9.04% (cal-
culated 10.36%) and 22.47% (calculated 20.0 l%) for Cu(II)
and Cd(II) complexes, respectively. )e remaining ligand
molecules were eliminated in the subsequent steps and the
decomposition was completed at ∼650 and 800°C leading to
the formation of the stable metal oxide CuO and CdO.
)e DTA data listed in Table 2 pointed out that the
decomposition of the ligand and its metal complexes
appeared as exothermic and endothermic peaks.
3.7.1. Structural Interpretation. Depending on the range of
spectral and physicochemical analysis presented here, the
structures of ligand and its metal complexes are shown in
Figures 1 and 2.
3.8. Molecular Modeling
3.8.1. Molecular Parameters. Additional parameters such
as chemical potentials (Pi), absolute electronegativities (χ),
global softness (S), absolute hardness (η), additional
electronic charge (ΔNmax), global electrophilicity (ω), and
absolute softness (σ) estimated for the Hl free ligand are
listed in Supplementary Table 1. )e toxicity and the re-
activity of various selective sites could be described by
electrophilicity index (ω), which is considered as signifi-
cant quantum chemical headline. )e biological activity of
drug-receptor interaction may be quantified by the elec-
trophilicity. Also, the stabilization energy was determined
by this index when the system was obtained from the
environment on an additional negative charge. )e η and σ
parameters are scheme of the molecular reactivity and
stability, and their perceptions were linked with all others.
)e softness index was on the contrary to global stiffness.
)e suggested structures were supported by these pa-
rameters, and the mentioned quantum chemical param-
eters were studied through the recommended equations
[39–41]. )e calculated data are presented in Supple-
mentary Table 1, and the following study able to illustrate
that
3.5. Magnetic Moment Analysis and Electronic Spectra.
)e subtle reflectance spectra for Fe(III) complex indicated a
signal at 21,362 cm− 1, possibly specified toward 6Alg ⟶ T2g
(G) conversion into octahedral geometry belonging to
6
4
complex [33–35]. )e transition A1g ⟶ T2g (G) and
6A1g ⟶ T1g was split into two signals at 17,642 and
4
12,784 cm− 1. )e Fe(III) complex has magnetic moment
5.30 B.M. )erefore, the produced complex showed octa-
hedral geometry indicating d2sp3 hybridization of Fe(III)
[35], while in case of Cu(II) complex broad band was ob-
served at 15,921 cm− 1. )is signal was generally perfectly
symmetric with an octahedral geometry designed for Cu(II)
complex. )e value of l.70 B.M from magnetic moment
pinpointed the octahedral structure [36].
)e Co(II) complex spectrum of diffused reflectance
showed three signals at 13,215, 15,841, and 17,492 cm− 1. )e
octahedral geometry was supported by the value of the
magnetic moment of the complex (μeff � 5.06 B.M.) [36]. )e
spectrum reflectance of Ni(II) complex also showed three
spectral peaks at 21,645, 17,377, and 13,542 cm− 1. )e lo-
cations of all three peaks were clearly harmonic by those
portended in favor of octahedral geometry [35]. )ese bands
(i) )e information of HL ligand indicated an enor-
mous possibility in favor of biological action based
on elevated ω value.
3
3
can be assigned, respectively [36], to A2g(F) ⟶ Tlg(F),
3
3
3
3A2g(F) ⟶ T2g(P), and A2g(F) ⟶ T2g(F) conversion.
Octahedral geometry can be additionally supported by the
magnetic moment value μeff � 3.30 B.M. )e empirical for-
mula of Cd(II) complex indicated that it has diamagnetic
and octahedral geometry properties [36].
(ii) η is hardness, whereas S and ω were indexes for
softness; as the energy difference between EHOMO
and ELUMO increasing the stability of the molecule
increases (Figure 3). )erefore, the reactive soft
molecule is having pliable contribution to metal
ions. )us, the explored HL ligand was observed soft
against coordination.
3.6. Mass Spectral (MS) Studies. )e mass spectra of the
ligands Ni(II), Cd(II), and Co(II) chelates exhibited mo-
lecular ion m/z bands at 354, 876, 928, and 880 atomic mass
unit, which were in accordance with the molecular weights
proposed, 354, 874, 928, and 878.5 amu, respectively. )e
molecular weights of the ligand and metal chelates agreed
with elemental and thermogravimetric analyses, which have
been utilized to prove the suggested formula. )ese prove
the stoichiometry of complexes as we suggested in this type
[M(Hl)2]. )e multipeak type of the spectrum mass indi-
cated the nature of the sequent degradation of base com-
pound having peaks’ series identical to a variety of fractions.
)e intensity of peaks provides an insight about stability of
fragments. )e fragmentation pattern of free ligand is shown
in Scheme 1.
(iii) It was clear from the negative electronic chemical
potential (μ) value and the positive electrophilicity
index (χ) value that the HL ligand has a negative
electronic chemical potential due to accepting
electrons from the environment, which leads to
decrease in its energy [42].
(iv) )e overall energy for the liberated ligand observed
was very tiny, which clearly signified that the iso-
lated ligands were stable.
(v) )e very tiny energy space may be related to low
kinetic stability, reflecting efficient electronic charge
transfer interaction and high chemical reactivity,
making the ligand strongly polarizable.

6
Journal of Chemistry
H2N
SH
N
N
H3C
H2
C
(H2C)15
N
4-amino-5-heptadecyl-4H-1,2,4-triazole-3-thiol
Chemical formula:C19H38N4S
Exact mass:354.28
H2N
SH
H2N
N
N
SH
N
N
C12H24
N
C15H30
N
Molecular weight: 283.46
Molecular weight: 325.54
H2N
H2N
SH
N
SH
N
C9H18
C10H20
N
N
N
N
Molecular weight: 241.38
Molecular weight: 255.40
H2N
H2N
SH
N
SH
N
N
C6H12
C5H10
N
N
N
Molecular weight: 199.30
Molecular weight: 185.27
H2N
H2N
SH
N
H
N
SH
N
N
H2C
N
N
Molecular weight:
56.07
N
N
Molecular weight: 129.16
N
N
N
Molecular weight: 116.14
Molecular weight: 69.07
Scheme 1
H2N
N
CH3
N
M
N
H2
SH
N
C
(CH2)15
H3C
H
C2
N
(H2C)15
N
N
Cln
HS
NH2
4-amino-5-heptadecyl-4H-l,2,4-triazole-3-thiol
OH2
H2O
H2N
Figure 1: Proposed structure of triazole ligand.
SH
3.8.2. ?e Atomic Charges, Bond Angles, and Bond Lengths.
)e calculation of atomic charges played a significant role in
the application of quantum mechanical calculations [42, 43].
)e estimated atomic charge was determined by Mulliken
population analysis with optimized geometry and the data
N
H3C
C
N
(H2C)15
H2
Figure 2: Proposed structure of complexes.

Journal of Chemistry
7
HOMO
LUMO
Figure 3: HOMO and LUMO patterns of triazole ligand.
Figure 4: Numbering system for triazole ligand.
electronegativity, and from that these atoms were suggested
as center of chelation. Results listed in Supplementary Ta-
bles 2 and 3 indicated that sulfur (S7) and amino nitrogen
N6 atoms in Hl have extra negative charges compared to
other atoms.
50
40
)e suitable places of coordination with metal ions
were predicted using Mulliken method existent of triazole
ligand HL that was additionally carried through MEP
analysis. On the other hand, the bond of (Cl-C24) had
more length than the other bonds in triazole ring (N2,N3),
(N3,C4), and (C4,N5); the large bond length of (C4,S7) and
(N5,N6); and the big bond angle (N3,C4,S7), (Cl,N5,N6),
(C4,N5,N6), and (N2,C1,C24), Supplementary Tables (2,
3). Also, the high dihedral bond angles (N3,C4,N5,N6),
30
20
Cd-complex
Cu-complex
Ni-complex
10
0
Co-complex
Fe-complex
HL
DMSO
(S7,C4,N5,C1),
(S7,C4,N5,N6),
(N3,C4,S7,H27),
(N5,C4,S7,H27), (Cl,N5,N6,H25), (Cl,N5,N6,H26),
(C4,N5,N6,H25), (C4,N5,N6,H26), (C24,C1,N5,C4),
(C24,C1,N5,N6), (N2,C1,C24,C23), (N2,C1,C24,H61),
(N2,C1,C24,H62), (N5,C1,C24,C23), (N5,C1,C24,H61),
(N5,C1,C24,H62), (N2,N3,C4,S7), and (C24,C1,N2,N3)
enhanced the rapture of these bonds firstly, Supple-
mentary Tables 2 and 3. )is suggestion was compatible
with mass fragmentation and thermal degradation and
confirmed the discussion.
Figure 5: Biological activity of triazole ligand and its metal
complexes.
are listed in Supplementary Tables 2 and 3 and is shown in
Figure 4. Since noticed, the N(II) and N(III) atoms have
lower negative atomic charges compared to nitrogen atoms
(N6) from the amino group, and also the existence of N2 and
N3 beside and attached to N6 and S7 causes higher
3.8.3. Antimicrobial Activity of Ligand and Its Monomeric
Complexes. Synthesized triazole and its corresponding

8
Journal of Chemistry
Table 3: Biological activity of triazole ligand and its metal chelates.
Inhibition zone (mm sample)
Sample
Gram negative
Gram positive
Escherichia coli
Proteus vulgaris
Bacillus subtilis
Staphylococcus pyogenes
Control: DMSO
HL
0
0
0
0
11
30
44
40
40
22
7
12
22
32
33
27
30
6
11
25
25
30
35
27
7
10
20
27
32
30
25
8
[Fe(HL)2(H2O)2]·Cl3
[Co(HL)2(H2O)2]·Cl2
[Ni(HL)2(H2O)2]·Cl2
[Cu(HL)2(H2O)2]·Cl2
[Cd(HL)2(H2O)2]·Cl2
Amikacin
Figure 6: )ree-dimensional plot of interaction of triazole ligand with E. coli (3 t88) receptor.
metal chelates were investigated against Bacillus subtilis,
antibacterial activity against B. subtilis and S. pyogenes or-
Proteus vulgaris, Escherichia coli, and Staphylococcus pyo-
genes to estimate their potential as antimicrobial agents by
well-diffusion method, which is well known as the agar ditch
method. An observed zone of inhibition is shown in Fig-
ure 5. )e counted zones of inhibition next to the growth of
respective microorganisms are listed in Table 3. It was
observed from Table 3 that all complexes showed greater
antibacterial activity than that of ligand [44]. All the com-
plexes showed very good results against all bacterial strains.
Furthermore, metal complexes showed excellent antibac-
terial activity against E. coli. In addition, Cd(II), Ni(II), and
Co(II) chelates have very good antibacterial activity toward
P. vulgaris, while Ni(II) and Cu(II) complexes showed high
ganisms Figure 5.
)e zone of inhibition can be monitored by altering
the incubation conditions, culture medium, concentra-
tion of the antibacterial agent, and rate of diffusion. )e
activity of all the synthesized complexes may be dem-
onstrated according to the chelation theory where the
polarity of the metal atom decreased by chelation. )is
reduction in polarity is due to partial share of the π
electron delocalization and positive charge of the donor
groups of the coordination sphere (Figure 5). Also, the
lipophilic nature of the central atom increased by che-
lation, serving its penetration to the lipid layer of the cell
membrane [45]. )e main aim of this work was to utilize

Journal of Chemistry
9
Figure 7: )ree-dimensional plot of interaction of triazole ligand with B. subtilis (5 h67) receptor.
Figure 8: )ree-dimensional plot of interaction of triazole ligand with P. vulgaris (5i39) receptor.

10
Journal of Chemistry
these complexes as drug agents in several widespread
diseases originated by septicemia, E. coli, e.g., diarrhea,
vomiting urinary tract infectivity, and infections obtained
from hospitals [46].
Conflicts of Interest
)e authors declare that there are no conflicts of interest
regarding the publication of this paper.
Acknowledgments
3.9. Molecular Docking. Antimicrobial features of drugs
were explained using AutoDock tools. )e triazole ligand
(guest) executed had diverse peptide receptors from host: E.
coli (3 t88), B. subtilis (5 h67), and P. vulgaris (5i39) by
molecular docking (Figures 6–8). )e space and energies
since most excellent type designed for docking method was
examined. Along with computation, a sturdy communica-
tion through all receptors having comparable results was
illustrated using HB plots (Figures 6–8). )is indicated
mutable competence for the H-bonding contact via multi-
central groups internal docking complexes. All proteins have
inter-hydrogen bonding [47,48]. )e docking process was
evidenced using 2D plots (Figures 6–8). )erefore, the tri-
azole-thiol ligand interrelated with AA (amino acids) of
proteins via -H bonding as follows.
)e authors wish to articulate their thanks and gratefulness
to the Chemistry Department in Taibah University, Cairo
University, and Nationa1 Research Center.
Supplementary Materials
Table S1: the calculated quantum chemical parameters of the
ligand. Table S2: selected geometric atomic charges, bond
angles, and bond length of the ligand. Table S3: selected
geometric dihedral bond angles (°) of the ligand. (Supple-
mentary Materials)
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