Synthesis, characterization, antimicrobial, and MOE evaluation of nano 1,2,4-triazole-based Schiff base ligand with some d-block metal ions

Article abstract of DOI:10.1002/aoc.6219

Three new metal complexes of 4-(benzylideneamino)-5-phenyl-4H-1,2,4-triazole-3-thiol ligand (L) and three transition metal ions: Fe (III), Cu (II), and Zn (II) were synthesized and characterized. The ligand derived from 4-amino-5-phenyl-1,2,4-triazole-3-thiol and benzaldehyde was synthesized in a 1:1 molar ratio. All the chelates were characterized by elemental analysis, conductivity measurements, thermal analysis, FT-IR, and ¹H-NMR spectroscopy. The IR spectrum revealed that the Schiff base ligand coordinated in a neutral bidentate manner with the metal ions through the azomethine N and thiol S. The thiol group coordinated to the metal ions without proton displacement as confirmed from the ¹H NMR spectra. The conductivity data showed the electrolytic nature of the Fe (III) and Cu (II) complexes while the Zn (II) complex was nonelectrolyte. All metal complexes had octahedral structure as depicted by spectral and elemental analyses. The complexes start decomposition at 35°C, and they decomposed in four to five steps. The scanning electron microscope (SEM) analysis confirmed the presence of metal complexes in nanostructure. The 1,2,4-triazole Schiff base ligand (L) and its transition metal complexes have been screened for their antibacterial (Gram [+] bacteria): Bacillis subtilis and Staphylococcus aureus, (Gram [?] bacteria): Escherichia coli and Pseudomonas aeruginosa and two fungi: Candida albicans and Aspergillus flavus by agar diffusion method. The two metal complexes were subjected to molecular docking study against crystal structure of Aspergillus fumigatus (PDB ID: 6NE0) and crystal structure of Mycobacterium tuberculosis (PDB ID: 5UHF). The mode of binding between the A. fumigatus (PDB ID: 6NE0) and Mycobacterium tuberculosis strains and the complexes was discussed.

Full text of DOI:10.1002/aoc.6219

Received: 16 January 2021
DOI: 10.1002/aoc.6219
Revised: 10 February 2021
Accepted: 19 February 2021
F U L L P A P E R
Synthesis, characterization, antimicrobial, and MOE
evaluation of nano 1,2,4-triazole-based Schiff base ligand
with some d-block metal ions
Nessma F. Mahmoud
| Ashraf A. Abbas
| Gehad G. Mohamed
Chemistry Department, Faculty of
Three new metal complexes of 4-(benzylideneamino)-5-phenyl-4H-1,-
2,4-triazole-3-thiol ligand (L) and three transition metal ions: Fe (III), Cu (II),
and Zn (II) were synthesized and characterized. The ligand derived from
4-amino-5-phenyl-1,2,4-triazole-3-thiol and benzaldehyde was synthesized in a
1:1 molar ratio. All the chelates were characterized by elemental analysis, con-
Science, Cairo University, Giza, Egypt
Correspondence
Nessma F. Mahmoud, Chemistry
Department, Faculty of Science, Cairo
University. Giza, l26l3, Egypt.
Email: nesmaf@sci.cu.edu.eg;
nessmamahmoud27@gmail.com
1
ductivity measurements, thermal analysis, FT-IR, and H-NMR spectroscopy.
The IR spectrum revealed that the Schiff base ligand coordinated in a neutral
bidentate manner with the metal ions through the azomethine N and thiol
S. The thiol group coordinated to the metal ions without proton displacement
1
as confirmed from the H NMR spectra. The conductivity data showed the
electrolytic nature of the Fe (III) and Cu (II) complexes while the Zn
(II) complex was nonelectrolyte. All metal complexes had octahedral structure
as depicted by spectral and elemental analyses. The complexes start decompo-
sition at 35ꢀC, and they decomposed in four to five steps. The scanning elec-
tron microscope (SEM) analysis confirmed the presence of metal complexes in
nanostructure. The 1,2,4-triazole Schiff base ligand (L) and its transition metal
complexes have been screened for their antibacterial (Gram [+] bacteria):
Bacillis subtilis and Staphylococcus aureus, (Gram [−] bacteria): Escherichia coli
and Pseudomonas aeruginosa and two fungi: Candida albicans and Aspergillus
flavus by agar diffusion method. The two metal complexes were subjected to
molecular docking study against crystal structure of Aspergillus fumigatus
(PDB ID: 6NE0) and crystal structure of Mycobacterium tuberculosis (PDB ID:
5UHF). The mode of binding between the A. fumigatus (PDB ID: 6NE0) and
Mycobacterium tuberculosis strains and the complexes was discussed.
K E Y W O R D S
1,2,4-triazole, Candida albicans, diffusion method, MOE, thermal analysis
Three metal chelates of new Schiff base were prepared and characterized.
Gehad G. Mohamed, Ph.D:0000-0003-4152-3150
Appl Organomet Chem. 2021;e6219.
wileyonlinelibrary.com/journal/aoc
© 2021 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.6219

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MAHMOUD ET AL.
1 | INTRODUCTION
charming fields.[17–21] Transition cations have distinct
optical, electrical, and magnetic properties, but through
the interactions between transition cations and Schiff
base ligands, the characteristics can be modified and
enhanced to be applied to broader fields.
The nucleus of 1,2,4-triazole can be regarded as a
pharmacophore and has been used in a number of thera-
peutically relevant molecules that have demonstrated a
broad range of pharmacological activities such as antimi-
crobial, anticancer, antiviral, anti-inflammatory, analge-
sic, and anticonvulsant. There have been many efforts to
strengthen its act by the issue of multidrug resistant
micro-organisms; several attempts have been done to
improve the activity of these compounds by incorporating
different substituents on the triazole nucleus. Triazoles
with azomethine group (-CH=N-), known as Schiff bases
of triazole, are also reported to possess antimicrobial,
antiviral, and other activities.[1–3] Compounds containing
the substructure of 3-substituted-4-amino-5-mercapto-1,-
2,4-triazoles show a wide range of biological activity and
include amino and mercapto groups capable of coordi-
nating metal ions.[4,5]
The donor-chelating sites of sulfur and nitrogen are
also used as effective pesticides. The transition metal
complexes of substituted triazole derivatives are com-
monly applied to optical pH sensing as chemical trans-
ducers. Increased biological activity is demonstrated by
metal complexes with thiols containing additional
hydroxyl groups. As sodium channel blockers, substituted
triazole compounds are used either alone or in conjunc-
tion with therapeutically active compounds to regulate
the activity of the sodium channel to minimize different
forms of pain.[6–8]
In various fields of use, the coordinating compounds
of d-block metal ions play a distinct role. Among differ-
ent complexes, Schiff base complexes are more produc-
tive than many others.[9] This is because their process of
synthesis is easy, has excellent features, and has different
applications such as bioactivity, catalysis, and optical
sensors.[10–13] Notable biological activities, including
antibacterial, antifungal, anti-inflammatory, analgesic,
antituberculosis, antioxidant, and antiviral effects, were
strongly demonstrated in the Schiff base metal com-
plexes. Nanostructure compound studies are very
common due to their unique properties, which are
completely different in terms of their presence in the
bulk process, revealing vast numbers of molecules on the
surface. A significant consideration for regulating the size
of the materials on a submicrometer scale is the choice of
the synthesis method.[14]
Keeping the above facts in mind, this study focuses
on the coordination behavior of 4-(benzylideneamino)-
5-phenyl-4H-1,2,4-triazole-3-thiol ligand (Figure 1)
towards Fe (III), Cu (II), and Zn (II) metal ions and their
characterization by elemental analysis, conductivity
measurements, magnetic susceptibility, thermal analysis,
FT-IR, and 1H-NMR spectroscopy. The antimicrobial
activities were screened, and the data showed that Zn
(II) complex was the most potent one compared to Fe
(III) and Cu (II) complexes; to verify the scale of the
complexes, a scanning electron microscope analysis was
performed. In addition, in order to shed light on the way
of binding between the triazole Schiff base ligand and its
Zn (II) complex, the molecular docking analysis was
carried out with crystal structure of Aspergillus fumigatus
(PDB ID: 6NE0) and crystal structure of Mycobacterium
tuberculosis (PDB ID: 5UHF).
2 | EXPERIMENTAL
2.1 | Materials and reagents
All chemicals used were of the analytical reagent grade
(AR) and of highest purity available. The chemicals used
involved 4-amino-5-phenyl-1,2,4-triazole-3-thiol and
benzaldehyde which were supplied from Sigma-Aldrich.
ZnCl2.2H2O (BDH), CuCl2.2H2O and FeCl3.6H2O
(Prolabo) were used. Organic solvents were spectroscopic
Due to their vast potential utilities, many reports
have targeted many examples of complexes through
their interactions with micro-organisms and tumor
activity.[15,16] Based on their structural diversity and their
potential properties, the synthesis and analysis of transi-
tion metal complexes are one of the most active and
FIGURE 1 The optimized structure of 1,2,4-triazole Schiff base
ligand (L)

MAHMOUD ET AL.
3 of 14
pure from BDH included ethanol, diethyl ether, and
dimethylformamide. Hydrogen peroxide, sodium chlo-
ride, sodium carbonate, glacial acetic acid, and sodium
hydroxide (A.R.) were used.
heated under reflux for 2 h. The solvent was then vacuum
extracted, and cold water (20 ml) was applied to the sol-
vent. The solid obtained was collected and crystallized
from ethanol by filtration to give colorless crystals of
Schiff's base (3) in 85% yield, mp.186ꢀC (Scheme 1).[22,23]
4-(benzylideneamino)-5-phenyl-4H-1,2,4-triazole-3-thiol
(L). Yield 85%; m.p. 186ꢀC; white solid. Anal. Calc. for
C15H12N4S (%): C, 64.38; H, 4.28; N, 20.0. Found
(%): C, 64.22; H, 4.16; N, 19.8. FT-IR (ν, cm−1): thiol
(SH) 2932sh, azomethine (CH=N) 1604sh, ν(C-S) 1365sh,
ν(N-C-S) 964 m.1H NMR (300 MHz, DMSO-d6, δ, ppm):
14.2 (s, 1H, thiol proton), 9.72 (s, 1H, CH=N azomethine),
7.51–8.03 (m, 10H, aromatic protons). UV–Vis (λmax, nm):
272 (π–π* of aromatic rings) and 322 (n–π* of SH and
CH=N groups).
2.2 | Instrumentations
Carbon, hydrogen, and nitrogen microanalyses were per-
formed using the CHNS-932 (LECO) Vario Elemental
Analyzer at the Microanalytical Center, Cairo University,
Egypt. Metal analysis accompanied the dissolution of the
solid complex in concentrated HNO3, neutralization with
ammonia of the diluted aqueous solutions and titration
with EDTA of the metal solutions. On a Perkin-Elmer
1650 (4000–400 cm−l) spectrometer, FT-IR spectra were
registered as KBr discs. At room temperature, electronic
spectra were registered as solutions in ethanol on a
Shimadzu 3101pc spectrophotometer. As a solution in
2.4 | Synthesis of metal complexes
1
DMSO-d6, H NMR spectra were recorded at room tem-
By mixing equal amounts (l.428 mmol) of hot saturated
ethanol solution of the 1,2,4-triazole Schiff base ligand
with the same metal chloride ratio, the Fe (III), Cu
(II) and Zn (II) complexes were prepared (lM: lL molar
ratio). For 3 h, the mixture was refluxed. Filtration col-
lected the resulting precipitates and washed them several
times with hot ethanol until the filtrates were clear. In
order to provide 83, 73, and 79 percent yield for Fe (III),
Cu (II), and Zn (II) complexes, respectively, the solid
complexes then dried in desiccator over anhydrous cal-
cium chloride.
perature on a 300 MHz Varian-Oxford Mercury using
TMS as an internal standard.
Using the Jenway 4,010 conductivity meter, the molar
conductivity of 10−3 M solid complex solutions in DMF
was calculated. On the UV mini-1240, UV–Vis spectro-
photometer, Shimadzu, UV–Vis spectra (wavelength
range from 200 to 700 nm) were carried out. Ther-
mogravimetric analyses (TG and DTG) of solid complexes
were performed using the Shimadzu TG-50H thermal
analyzer from room temperature to 1000ꢀC. A Quanta
FEG250 SEM (National Research Center, Egypt) recorded
a scanning electron microscopic (SEM) image of the com-
plexes. Using the MS-5988 GS-MS Hewlett–Packard
instrument at the Microanalytical Center, National
Center for Research, Egypt, mass spectra were recorded
by the EI technique at 70 eV. The antimicrobial activities
were carried out at the University of Cairo Microanalyti-
cal Center.
[Fe(L)(H2O)2Cl2]Cl.H2O
Yield 83%; m.p. 142ꢀC; brown solid. Anal. Calc. for
C15H18Cl3FeN4O3S (%): C, 36.25; H, 3.62; N, 11.28. Found
(%): C, 36.17; H, 3.57; N, 11.17. Λm (Ω−1mol−1cm2) = 60.9;
FT-IR (ν, cm−1): thiol (SH) 2931sh, azomethine (CH=N)
1627sh, ν(C-S) 1355 m, ν(N-C-S) 967 m, H2O stretching of
coordinated water 918 s and 880 m, (M O) 579 m,
(M N) 509 m. UV–Vis (λmax, nm): 272 (π–π* of aromatic
rings) and 331 (n–π* of SH and CH=N groups).
[Cu(L)(H2O)3Cl]Cl
2.3 | Synthesis of Schiff base ligand
Yield 73%; m.p. 171ꢀC; dark green solid. Anal. Calc.
for C15H18Cl2CuN4O3S (%): C, 38.42; H, 3.82; N, 11.95.
Found (%): C, 38.26; H, 3.55; N, 11.63. Λm
To a solution of 4-amino-5-phenyl-1,2,4-triazole-3-thiol (1)
(10 mmol) in glacial acetic acid (30 ml) was added benzal-
dehyde (2) (10 mmol). The reaction mixture was then
(Ω−1mol−1cm2)
=
61.7; FT-IR (ν, cm−1): thiol
(SH) 2,939 m, azomethine (CH=N) 1615sh, ν(C-S)
1357sh, ν(N-C-S) 964sh, H2O stretching of coordinated
water 916 s and 879 m, (M O) 578 m, (M N) 515 m.
UV–Vis (λmax, nm): 267 (π–π* of aromatic rings) and
324 (n–π* of SH and CH=N groups).
[Zn(L)(H2O)2Cl2].2H2O.
Yield 79%; m.p. 125ꢀC; yellowish white solid. Anal.
Calc. for C15H20Cl2N4O4SZn (%): C, 36.88; H, 4.09; N,
11.48. Found (%): C, 36.47; H, 3.99; N, 11.25. Λm
SCHEME 1 Preparation of 1,2,4-triazole Schiff base ligand (L)

4 of 14
MAHMOUD ET AL.
(Ω−1mol−1cm2) = 23; FT-IR (ν, cm−1): thiol (SH) 2963 m,
azomethine (CH=N) 1617sh, ν(C-S) 1358sh, ν(N-C-S)
972sh, H2O stretching of coordinated water 926 m and
2.8 | Computational methodology
Theoretical calculations for 1,2,4-triazole Schiff base
ligand (L) density functional theory (DFT) and molecular
modeling were performed on the theory level of Gauss-
ian03 package at DFT. Using DFT based on the B3LYP
method along with the LANL2DZ basis package, the
molecular geometry for the tested ligand was completely
optimized. Quantum chemical parameters were deter-
mined for the investigated molecule, such as the highest
occupied molecular orbital energy (EHOMO), the lowest
unoccupied molecular orbital energy (ELUMO), and the
HOMO-LUMO energy difference (ΔE).[28,31,32]
1
874sh, (M O) 576 m, (M N) 501sh. H NMR (300 MHz,
DMSO-d6, δ, ppm): 14.22 (s, 1H, thiol proton), 9.78 (s,
1H, CH=N azomethine), 7.51–7.90 (m, 10H, aromatic
protons). UV–Vis (λmax, nm): 270 (π–π* of aromatic rings)
and 326 (n–π* of SH and CH=N groups).
2.5 | Spectrophotometric studies
Within the wavelength range of 200 to 700 nm, the
absorption spectra of 1,2,4-triazole Schiff base ligand
(L) and its metal complexes under study have been
scanned.
3 | RESULTS AND DISCUSSION
3.1 | Characterization of the Schiff base
ligand
2.6 | Molecular docking
Molecular docking studies were carried out using MOE
2008 software in order to determine the possible
binding modes of the most active compounds against the
crystal structure of A. fumigatus (PDB ID: 6NE0) and the
crystal structure of M. tuberculosis (PDB ID: 5UHF).[24–27]
It is an interactive molecular graphics software for the
measurement and display of a receptor and ligand and
complex molecules in viable docking modes. The ligand
and the receptor are required in PDB format as input.
The amino acid chain was retained, and the molecules of
water and co-crystallized ligands were eliminated. Gauss-
ian03 program has been developed to organize complexes
in the PDB file format. The A. fumigatus crystal structure
(PDB ID: 6NE0) and the M. tuberculosis crystal structure
(PDB ID: 5UHF) were downloaded from the protein data
bank (https://www.rcsb.org/pdb).
The novel l,2,4-triazole Schiff base ligand (L) was pre-
pared as previously mentioned in the experimental part.
The isolated ligand was colorless crystal, stable in air,
and soluble in the most common organic solvents. The
new ligand was subjected to elemental analysis (C, H, N),
infrared spectral studies IR, lH-NMR, molar conductivity,
mass spectra, and thermal analysis (TG and DTG), in
order to identify its formula to investigate its molecular
structure.[33] The chemical composition of the ligand
(L) was figured out from elemental analysis data in
Table 1, and it was found to be (Calcd.) 64.38 C%, 4.28 H
% and 20.0 N%; (Found) 64.22 C%, 4.16 H% and 19.8 N
%.[34–37]
TABLE 1 The different quantum chemical parameters of the
1,2,4-triazole Schiff base ligand (L)
The calculated quantum chemical parameters
2.7 | Antimicrobial activity
E (a.u.)
−1195.25
1.6438
−0.115
0.012
The in vitro antibacterial and antifungal activity tests
were performed through the well diffusion method[28]
using ampicillin and amphotericin as positive control for
antibacterial agent and antifungal agent, respectively.
The bacterial organisms used are Gram(+) bacteria:
Bacillis subtilis and Staphylococcus aureus, Gram(−) bac-
teria: Escherichia coli and Pseudomonas aeruginosa, and
two fungi of C. albicans and Aspergillus flavus. By dis-
solving the compounds in DMSO, the stock solution
(0.00 l mol) was prepared. The diameter was measured in
millimeters for the inhibition zones. Triplicate antimicro-
bial activities were carried out, and the average was taken
as the final reading.[29,30]
Dipole moment (Debye)
EHOMO (eV)
E
LUMO (eV)
ΔE (eV)
χ (eV)
0.103
0.064
η (eV)
0.051
σ (eV)−1
Pi (eV)
S (eV)−1
ω (eV)
19.607
−0.064
9.803
0.040
ΔNmax
1.254

MAHMOUD ET AL.
5 of 14
3.1.1 | Geometrical optimization of the
triazole Schiff base ligand (L)
The molecule is better for donating electrons as
the value of EHOMO becomes higher. This implies that
the Schiff base ligand of triazole supplies electrons of the
transition metal ions to the unoccupied d-orbital, and this
raises the probability of complexation. Also, the energy of
the small band gap showed that the molecule was more
reactive. The ΔE value of the 1,2,4-triazole Schiff base
ligand (L) was very small (0.103 eV). In order to increase
the biological activities of the prepared substances, the
dipole moment is considered a very important function.
In characterizing the molecular structure of the pre-
pared compounds, calculating theoretical parameters
would help. So using the DFT process, the structure of
the 1,2,4-triazole Schiff base ligand has been opti-
mized.[38] Furthermore, other quantum chemical
parameters such as energy of the highest occupied
molecular orbital, EHOMO, energy of the lowest unoccu-
pied molecular orbital, ELUMO (Figure 2), energy gap
(ΔE), chemical potentials, Pi, electronegativity, χ,
dipole moment, μ, softness, σ, hardness, η and addi-
tional electronic charge, ΔNmax were calculated. Differ-
ent equations as mentioned below have been
calculated and then shown in Table 1. The determined
ligand (L) bond lengths and bond angles were shown
in supporting information Table S1, and the optimized
structure of the Schiff triazole base ligand (L) was
shown in Figure 1 above 1.[39,40]
3.1.2 | Molecular electrostatic
potential map
In supporting information Figure S1, molecular electro-
static potential map (MEP) of the synthesized ligand was
observed. The MEP provided valuable data on the distri-
butions of charge intensity, electrophilic interactions,
and chemically reactive sites present in the ligand.[41]
FIGURE 2 The different
molecular orbitals of the
1,2,4-triazole Schiff base ligand
(L), (a) HOMO, (b) HOMO-1,
(c) HOMO-2, (d) LUMO,
(e) LUMO+1, and (f) LUMO+2

6 of 14
MAHMOUD ET AL.
TABLE 2 The different Mulliken charges of 1,2,4-triazole
The positive electrostatic potential surfaces were
Schiff base ligand (L)
defined by the blue color that referred to the regions
of lower electron density. The negative regions were
depicted by a red color that referred to nucleophilic
sites. The ligand MEP showed a red color surrounding
the azomethine and thiol groups, while the rings of
triazole and benzene were surrounded by blue-green
colors.
Atom
C1
Mulliken charges
0.837730
C2
0.366659
N3
0.242000
N4
0.463837
This suggested that azomethine and thiol groups were
the more reactive sites that were electrophilic surfaces
that coordinated with metal ions.[42]
N5
0.208192
C6
−0.177309
0.300623
C7
C8
0.304355
C9
−0.170149
−0.012506
−0.174264
−0.174264
0.356570
3.1.3 | Vibrational properties
H10
C11
H12
C13
H14
H15
H16
S17
Experimental vibrational analysis was compared with
the theoretical data carried out based on the optimized
ligand structure to confirm the efficient preparation of
the ligand (supporting information Figure S2). System-
atic errors occurred in the data observed using quan-
tum chemical methods such as the DFT process. Using
the LanL2DZ level scaling factor of 0.96 will solve
these errors. The experimental data showed that the
ligand had five important characteristic bands which
were appeared at 2932, 1604, 1365, 1273, and
964 cm−1 which corresponded to ν (SH), ν (CH=N),
ν(C-S), ν(C-N), and ν(N-C-S), respectively. Theoreti-
cally, these bands were measured (supporting informa-
tion Figure S1) and their values of 2930, 1605, 1364,
1272, and 964 cm−1 were found. Such results verified
that the theoretical data are similar to the experimen-
tal values. So with successful techniques, the ligand
was prepared.[43,44]
0.005619
0.005559
−0.015479
−0.635564
0.847248
H18
N19
C20
H21
C22
C23
C24
C25
H26
C27
H28
C29
H30
H31
H32
−0.877112
0.680636
0.014207
−0.389267
0.000388
0.851854
0.231513
−0.040324
0.341695
−0.039590
−0.173996
−0.033164
−0.033593
0.001450
3.1.4 | Mulliken atomic charges for the
triazole Schiff base ligand
The Mulliken atomic charges are shown in Table 2 and
supporting information Figure S3. The total charge of the
donor nitrogen atom of azomethine group was −0.877 a.
u. For the donor thiol sulphur atom, the total charge was
−0.636 a.u. The remaining charges, which are the num-
ber of charges on all atoms other than donating atoms on
the ligand, are more positive, indicating that electrons
will transfer from several atoms in the ligand to metal
due to hyperconjugation during complexation. The C1
and C20 atoms had higher positive atomic charges than
the other carbon atoms of 0.837 and 0.680 a.u., respec-
tively. This was due to the electronegative atoms such as
azomethine nitrogen and thiol sulfur connected to these
carbon atoms.[45]
3.2 | Characterization of metal
complexes
1,2,4-Triazole Schiff base ligand (L) and its three solids d-
block metal complexes have been isolated in pure form.
The complexes are air stable for long time and insoluble
in MeOH, EtOH, acetone, CCl4 as well as benzene. The
prepared complexes were soluble in DMF and DMSO sol-
vents. Comparison of the elemental analyses for both the

MAHMOUD ET AL.
7 of 14
calculated and found percentages was used to deduce the
compositions and the proposed formulae of the isolated
complexes.[46]
proton. This signal still appeared at the same position as
the ligand which supports the coordination of triazole
Schiff base ligand to metal ions with protonated thiol
group. The lH-NMR spectrum of the Zn (II) complex rev-
ealed singlet signal at ꢁ9.78 ppm which can be assigned
to azomethine (-CH=N-) proton. This shift in signal posi-
tion of the azomethine group can attributed to binding of
azomethine group to metal ions. Also, the multiplet
signal within the range 7.51–7.90 ppm was assigned to
the aromatic protons in the Zn (II) complex. The signal
of coordinated water molecules appeared at 3.30 ppm
impeded with the water molecules of DMSO.[53]
3.3 | IR spectral studies
In the range of 4000–400 cm−l, the IR spectrum of the
free 1,2,4-triazole Schiff base ligand was carried out. The
sharp bands observed at 2932 cm−l for ν (SH) stretching,
1604 cm−l for ν (CH=N) stretching, 1365 cm−l for ν(C-S)
stretching, and 1273 cm−l for ν(C-N) stretching
vibrations. The medium band observed at 964 cm−l
was assigned for ν(N-C-S) stretching vibration. The
vibrational frequencies of the three metal complexes also
3.5 | Molar conductivity
referred to the following points[47]
:
Molar conductivity values (in Ω−l mol−l cm2) of the three
metal complexes were calculated at room temperature in
DMF solvents. In general, higher values of molar conduc-
tance are representative of the metal complexes' electro-
lytic nature. It was assumed from the results that the
Fe (III) complex had molar conductivity value of
60.9 Ω−l mol−l cm2, indicating its ionic nature and con-
firming its electrolytic nature.[54–56] The Cu (II) complex
had molar conductivity value of 61.7 Ω−l mol−l cm2 indi-
cating also the electrolytic nature of the complex. The
molar conductivity value of the Zn (II) complex was
23.1 Ω−l mol−l cm2, indicating its non-ionic nature.
• The investigated metal complexes displayed stretching
bands in the range 2931–2963 cm−l assigned for ν
(SH) indicating that the ligand coordinates to metal
ions via protonated thiol moiety.
• The complexes exhibited notable changes of the
azomethine CH=N group, where the bands in the
three complexes were found in the range of 1627–
1617 cm−l. This was an evidence confirming that
complexation reaction occurred through formation of
coordinate bond with azomethine nitrogen atom of the
1,2,4-triazole Schiff base ligand (supporting informa-
tion Figure S4).[48]
• The spectra of complexes showed new bands in range
of 916–926 and 874–880 cm−l which assigned for H2O
stretching vibration of the coordinated water. Medium
bands in range of 576–579 cm−l can have assigned to
ν(M-O) stretching vibrations of coordinated water. The
bands in range of 501–515 cm−l were attributed to
stretching vibration of ν(M-N).[49–52]
3.6 | Mass spectral studies
The 1,2,4-triazole Schiff base ligand's mass spectrum was
reported, and its proposed molecular weight was con-
firmed by the obtained molecular ion (m/z) peaks. The
1,2,4-triazole Schiff base ligand (L) mass spectrum
showed a m/z peak at 280.11 amu corresponding to the
(Cl9H7FeNO2) molecule. At 496.24 m/z, the mass spec-
trum of the Fe (III) complex revealed a molecular ion
peak close to its experimental molecular weight. It also
showed a sequence of peaks corresponding to different
fragments at m/z = 418.09, 248.14, 217.10, 103.02, and
76.00 amu. The strength of these peaks provided an idea
of fragment stability.[57–59]
It can be assumed that the 1,2,4-triazole Schiff base
ligand prepared was treated as a neutral bidentate ligand
coordinated to the metal ions through the thiol sulfur
atom and the azomethine nitrogen atom.
3.4 | 1H-NMR spectra
At m/z
= 280.11 amu corresponding to the
1
The H-NMR spectrum of the 1,2,4-triazole Schiff base
[C15H12N4S]+ ion confirming the complex formation,
the molecular ion peak of the parent ligand was found.
The Cu (II) complex revealed a mass spectrum with a
molecular ion peak at 468.39 m/z which was quite simi-
lar to its experimental molecular weights. It also revealed
a sequence of peaks corresponding to different fragments
at m/z = 380.48, 255.77, 192.03, 102.98, and 75.97 amu;
see supporting information Figure S6.
ligand displayed three significant peaks at 14.20, 9.72,
and 7.51–8.03 ppm with an integration equivalent to the
hydrogen protons corresponding to the (s, 1H, thiol pro-
ton), (s, 1H, CH=N azomethine), and (m, 10H, aromatic
protons), respectively (supporting information Figure S5).
1
The H-NMR spectrum of the Zn (II) complex showed
singlet signal at 14.22 ppm which is assigned to the thiol

8 of 14
MAHMOUD ET AL.
The Zn (II) complex mass spectrum showed a molec-
(II) complex had one unpaired electron showed a mag-
netic moment value of 1.76 BM at room temperature,
suggesting a high spin octahedral configuration. The dif-
fused reflectance spectrum of this complex indicated the
ular ion peak at 488.41 m/z that was close to its experi-
mental molecular weights. At m/z = 280.10 amu, the
parent ligand molecular ion peak was observed.
d–d transition bands at 15,087, 19,478, and 25,288 cm−1
.
2
2
The bands appeared correspond to B1g! A1g (dx2-
2
2
2
2
3.7 | UV–vis spectra and magnetic
y2!dz2), B1g! B2g (dx2-y2!dxy) and B1g! Eg (dx2–
y2!dxz, dyz) transitions, respectively. These data
suggested an octahedral geometry around Cu (II) ion in
the complex.[64] The Zn (II) complex has no unpaired
electron so it was diamagnetic and octahedral geometry
was suggested.[34]
moment measurements
1,2,4-Triazole Schiff base ligand (L) electronic spectra
and its complexes (supporting information Figure S7)
were calculated in DMF over the 200–700 nm range. The
free 1,2,4-triazole Schiff base ligand (L) showed different
bands in the UV–Vis region. The electronic absorption
spectrum of 1,2,4-triazole Schiff base ligand (L) gave a
sharp band at 277 nm which was mainly attributed to the
locally excited intraligand π ! π* transition.
3.8 | Thermal analysis studies (TG and
DTG)
This band was shifted to the wavelength range of
267–272 nm in the three metal complexes. The band at
322 nm was assigned to n-π* transition, indicating the
coordination of azomethine nitrogen and thiol sulfur to
the metal centers. This band was shifted to 326–331 nm
for the metal complexes.[60,61] Even though a coefficient
of molar extinction was not given, it can be calculated
In the temperature range from room temperature to
1000ꢀC, the thermal properties of the 1,2,4-triazole Schiff
base ligand and its metal complexes were studied. At
10ꢀC min−l, the heating rate was adequately covered. In
supporting information Table S2, the weight losses over
the temperature range, thermal decomposition rate, and
the residual masses corresponding to the final degrada-
tion products are summarized. With DTG, a single or
multistage mass loss was observed for these complexes
and attributed to the removal of molecular fragments due
to thermal decomposition.[65,66] The thermal analyses
(TG and DTG) were used to confirm the suggested frag-
mentation patterns and evaluate the degradation temper-
atures of the ligand. The TG data for the 1,2,4-triazole
Schiff base ligand (L) showed three steps of decomposi-
tion. The first step within the temperature range of
130–230ꢀC with temperature maximum 205ꢀC was corre-
lated with evolution of C7H7N molecule with mass loss of
37.64% (calcd. 37.50%). The second decomposition step
within the temperature range of 230–325ꢀC corresponds
to decomposition of another part of ligand (C7H5S mole-
cule) with mass loss of 42.59% (calcd 43.21%). The third
step of decomposition within temperature range of
325–435ꢀC corresponds to complete decomposition of the
final molecule of the ligand with mass loss of 19.08%
(calcd 19.29%). The total weight loss amounted to 99.91%
(calcd. 99.99%).
using
a
modified form of Beer's law for this
instrument[62]:.
A = εbC.
If ε is the coefficient of molar extinction of the two
metal complexes (Lmol−1 cm−1), A is absorbance, b is the
path length of the cuvette (cm) equal to 1, and C is the
concentration of metal complex solution (mol/L).
The molar extinction coefficient (ε in Lmol−1 cm−1
)
for the Fe (III) complex was 15,700 Lmol−1 cm−1 (n-π*
transition) and 29,680 Lmol−1 cm−1 (π -π* transition).
For the Cu (II) complex, the molar extinction coeffi-
cient was 18,300 Lmol−1 cm−1 (n-π* transition) and
27,600 Lmol−1 cm−1 (π-π* transition). For the Zn
(II) complex, the molar extinction coefficient was
11,590
Lmol−1
cm−1
(n-π*
transition)
and
26,510 Lmol−1 cm−1 (π-π* transition). Finally, for triazole
Schiff base ligand (L), the molar extinction coefficient
was 34,500 Lmol−1 cm−1 (n-π* transition) and
32,580 Lmol−1 cm−1 (π -π* transition).
The Fe (III) complex showed a magnetic moment
value of 5.42 BM at room temperature indicating the
presences of five unpaired electrons, suggesting a high
The thermogram of [Fe(L)(H2O)2Cl2]Cl.H2O complex
showed four decomposition steps within the temperature
range of 30–905ꢀC. The first and second decomposition
steps were accompanied by loss of C4H8Cl2S molecule in
the temperature range of 30–275ꢀC with an estimated
weight loss of 32.69% (calcd. 32.02%). The third and
fourth steps of decomposition showed loss of
C10H10ClN4O1.5 molecule at 275–905ꢀC with an estimated
weight loss of 48.52% (calcd. 49.45%). Thereafter, the
3
2
spin t2g eg configuration for the Fe (III) ion in an octa-
hedral environment. Two absorption bands were located
at 21,655 and 20,195 cm−1 in the diffused reflectance
spectrum of the Fe (III) complex. A charge transfer band
can be assigned to the first band, and the second band
6
4
[63]
can be assigned to the transition A1! T2,
implying
an octahedral geometry around the Fe (III) ion. The Cu

MAHMOUD ET AL.
9 of 14
percentage of the residue corresponds to ferric oxide con-
taminated with carbon and the total approximate weight
loss was found to be 81.31% (calcd. 81.46%).
decomposition involved the removal of C7H11NO3 mole-
cule in the 445–1000ꢀC temperature range and were
accompanied by weight loss of 32.64% (calcd. 32.17%).
The net weight loss was 83.73% (calcd. 83.40%), and zinc
oxide remained as a residue. The residues of decomposi-
tion were subjected to IR study to ensure the complete
decomposition of the ligand and the data obtained
evidenced the presence of metal oxide (ν(M-O)) at
570 cm−1 (broad) and 594 cm−1 (broad) for Fe (III) and
Cu (II) complexes, respectively (supporting information
Figure S8).
The TG thermogram of [Cu(L)(H2O)3Cl]Cl complex
showed four decomposition steps within the temperature
range of 30–865ꢀC. The first and second decomposition
steps were accompanied by loss of 2HCl and C5H11N2S
molecules in the temperature range of 30–340ꢀC with an
estimated weight loss of 43.03% (calcd. 43.54%). The third
and fourth steps of decomposition showed loss of
C5H5N2O2 molecule at 340–865ꢀC with an estimated
weight loss of 27.12% (calcd. 26.68%). Thereafter, the per-
centage of the residue corresponds to copper oxide con-
taminated with carbon and the total estimated weight
loss was found to be 70.15% (calcd. 70.22%). TG curve of
the [Zn(L)(H2O)2Cl2].2H2O complex showed five steps of
decomposition. The first, second, and third steps of
decomposition occurred in the 35–445ꢀC temperature
range, corresponding to the loss of 2HCl and C8H7N3S
molecules and were followed by a weight loss of 51.08%
(calcd. 51.23%). The fourth and fifth steps of
3.9 | SEM analysis
The SEM micrographs of the 1,2,4-triazole Schiff base
ligand, Fe (III), Cu (II) and Zn (II) complexes are given
in Figure 3. The SEM micrographs of the free ligand and
its Fe (III), Cu (II), and Zn (II) complexes with the inclu-
sion of small grains in the nanometer scale showed dra-
matically different morphological structures. Ligand
FIGURE 3 Scanning electron microscope (SEM) images of (a) 1,2,4-triazole Schiff base ligand (L), (b) [Fe(L)(H2O)2Cl2]Cl.H2O, (c) [Cu
(L)(H2O)3Cl]Cl, and (d) [Zn(L)(H2O)2Cl2].2H2O metal complexes

10 of 14
MAHMOUD ET AL.
(L) exhibited regularly compact-shaped particles with
small grains with average particle size 37.40 nm, while
the Fe (III) complex exhibited irregular morphology with
average grain size 8.99 nm. The Cu (II) complex showed
irregular morphology with average grain size of
21.21 nm, while the Zn (II) complex had average grain
size 22.48 nm. The formation of metal complexes has
been further confirmed by the various surface morphol-
ogies between the parent ligand and its metal complexes.
The average grain size obtained from SEM analysis
showed that with nano-sized grains, the complexes are
polycrystalline.[67] The Fe (III) complex showed very
small nano-sized structure of only 8.99 nm.
3.11 | Biological activities
3.11.1 | Antibacterial activity
The compounds under investigation were tested individu-
ally against different bacterial species such as S. aureus
(G+), Bacillis subtilis (G+), P. aeruginosa (G−), and E.
coli (G−). Biological investigation was screened using
agar well diffusion methods.[68] Comparative analysis for
antibacterial study of 1,2,4-triazole Schiff base ligand
(L) and its complexes were listed in Table 3 and Figure 5.
The bacterial growth inhibitory capacity of the
1,2,4-triazole Schiff base ligand and its complexes follow
the order:
for S. aureus and Bacillis subtilis: L < Cu (II) < Fe
(III) < Zn (III).
3.10 | Structura1 interpretation
for P. aeruginosa and E. coli: L < Cu (II) < Fe
(III) < Zn (III).
Based on all previous data, several tools such as elemen-
tal analysis, molar conductivity, IR, mass spectrometry
and thermal analysis data, and the proposed structures of
metal complexes were stated in Figure 4 to characterize
the structures of the 1,2,4-triazole Schiff base ligand and
Fe (III), Cu (II) and Zn (II) complexes.
The Zn (II) complex was the most active antibacterial
agent than the Fe (III) and Cu (II) complexes. Based on
the partial sharing of the positive charge of metal ions
with donor groups, this increase in antibacterial activity
was rationalized.[69,70] This may support the argument
that some form of biomolecular binding to metal ions or
interchelation or electrostatic interactions causes the
inhibition of biological synthesis. So it can be concluded
that Zn (II) complex revealed higher antimicrobial activ-
ity than the free 1,2,4-triazole Schiff base ligand.[71]
3.11.2 | Antifungal activity
The results gained for biological activity for the prepared
1,2,4-triazole Schiff base ligand and its metal complexes
were given in Table 3 and Figure 5 against different fungi
organisms such as A. flavus and C. albican. Amphotericin
B was used as reference compound for antifungal activi-
ties.[72] The data showed that metal complexes had the
capacity of inhibiting the metabolic growth of the investi-
gated fungi, which may indicate broad-spectrum proper-
ties than the free 1,2,4-triazole Schiff base ligand
(L) itself. The activity of these metal complexes may be
arising from the presence of the metal ions and CH=N
moiety which have chelating properties.[73,74] The in vitro
antifungal activity demonstrated that Zn (II) complex
had higher antifungal activity in comparison with that of
the Fe (III) complex, while ligand (L) and Cu
(II) complex had no activity against fungi.[75]
The antimicrobial behavior of the prepared
1,2,4-triazole Schiff base ligand (L) and its metal com-
plexes were verified by measuring the activity index
FIGURE 4 The structures of metal complexes with a chemical
composition of [M(L)(H2O)2Cl2].xCl.nH2O (M: Fe (III), Cu (II), and
Zn (II))
according to the following relation[76,77]
:

MAHMOUD ET AL.
11 of 14
TABLE 3 Biological activity of 1,2,4-triazole Schiff base ligand (L) and its metal complexes
Inhibition zone diameter (mm/mg sample)
Gram (+) Bacteria
Gram (−) Bacteria
Fungi
Bacillus
Subtilis
Staphylococcus
aureus
Escherichia
coli
Pseudomonas
aeruginosa
Aspergillus
flavus
Candida
albicans
Sample
Control: DMSO
0
0
0
0
0
0
Ampicillin
26
21
25
26
-----
-----
(Antibacterial agent)
Amphotericin B
-----
-----
-----
-----
17
21
(Antifungal agent)
Ligand (L)
12
13
11
14
9
12
12
11
12
10
13
10
18
0
0
[Fe(L)(H2O)2Cl2]Cl. H2O
[Cu(L)(H2O)3Cl]Cl
[Zn(L)(H2O)2Cl2] .2H2O
12
13
16
13
0
11
0
12
10
FIGURE 5 Biological activity of
1,2,4-triazole Schiff base ligand
(L) and its metal complexes
Activity index (A) = Inhibition zone of compound
(mm) × l00.
immunocompetent host, and aspergilloma and allergic
bronchopulmonary aspergillosis, the only infections
noticed in such hosts, are rare clinical syndromes. There-
fore, A. Fumigatus has been thought to be a weak
pathogen for years. However, there has been a dramatic
rise in serious and typically lethal invasive aspergillosis,
now the most common mold infection worldwide,
with an increase in the number of immunosuppressed
patients.[80,81]
Inhibition zone of standard drug (mm)
From the results, it is deduced that Zn (II) complex
had the highest antibacterial/antifungal activity index[78]
see supporting information Figure S9.
;
3.12 | Molecular modeling of ligand
(L) and its complexes: Docking study
A. fumigatus is a saprophytic fungus which plays a
vital role in the recycling of carbon and nitrogen from
the environment. The soil, where it lives and grows on
organic debris, is its natural environmental niche. While
this species is not the most prevalent fungus in the world,
it is one of the most ubiquitous of those with airborne
conidia. It sporulates abundantly, producing thousands
of conidia with each conidial head. Environmental stud-
ies showed that at least several hundred A. fumigatus
conidia per day would be inhaled by all humans. There-
fore, for most patients, disease occurs mainly in the
Molecular docking studies have been carried out in order
to predict the binding modes of l,2,4-triazole Schiff base
ligand (L) and its Zn (II) complex to crystal structure of
A. fumigatus (PDB ID: 6NE0) and crystal structure of M.
tuberculosis (PDB ID: 5UHF).[79]
One of the most ubiquitous airborne saprophytic
fungi is A. fumigatus. Humans and animals continuously
inhale this fungus' various conidia. Conidia are typically
destroyed by innate immune processes in the

12 of 14
MAHMOUD ET AL.
lungs, but in the most highly predisposed, transmission
to virtually any organ occurs.[82]
One of the oldest known human diseases, tuberculosis
(TB), is still one of the main causes of death, as two
million people die per year from this disease. TB has many
symptoms that involve the bone, central nervous system,
and many other organ systems, but it is mainly a pulmo-
nary disease that is caused by aerosol droplet deposition of
M. tuberculosis onto lung alveolar surfaces. Furthermore,
since some M. tuberculosis the pathogen may play a role
in disease progression. As characterized by increased
transmissibility, as well as being associated with higher
morbidity and mortality in infected individuals, M. tuber-
culosis strains are reportedly more virulent than others.
Despite the widespread use of an attenuated live vac-
cine and many antibiotics, new vaccines and medicines
and more precise and rapid diagnostics are needed; there
is more TB than ever before. Researchers are using data
collected from the full sequence of the M. tuberculosis to
identify targets in M. tuberculosis. The genome of M.
tuberculosis and from modern genetic and physiological
approaches will help to produce these sorely needed
antituberculosis agents.[84] The [Zn(L)(H2O)2Cl2].2H2O
complex showed the highest interaction with minimum
binding energy of −10.0 kcal/mol of crystal structure of
M. tuberculosis (PDB ID: 5UHF); see supporting informa-
tion Figure S10.
Figure 6 showed the binding models of 1,2,4-triazole
Schiff base ligand to crystal structure of A. fumigatus
(PDB ID: 6NE0). From the data shown in supporting
information Tables S3 and S4, it was found that through
a hydrogen bond and a π-interaction, all the compounds
tested interacted with the protein. Interaction energy
values showed that the Zn (II) complex had the most sta-
ble interaction with a minimum binding energy of
−3.6 kcal/mol than the free 1,2,4-triazole Schiff base
ligand (L).[83]
The binding energy histogram (−E kcal/mol)
(supporting information Figure S11) between the
1,2,4-triazole Schiff base ligand and its three transition
metal complexes with A. fumigatus crystal structure recep-
tors (PDB ID: 6NE0) and the M. tuberculosis crystal struc-
ture (PDB ID: 5UHF) revealed that [Zn(L)(H2O)2Cl2].2H2O
had a minimum binding energy of −10.0 kcal/mol with
crystal structure of M. tuberculosis (PDB ID: 5UHF).
4 | CONCLUSION
In order to classify the 1,2,4-triazole Schiff base ligand
under investigation and its transition metal complexes,
various physicochemical, spectroscopic, and thermal
methods of analysis were used. In addition, the [Zn(L)
(H2O)2Cl2].2H2O complex was classified as the most active
antibacterial/antifungal compound among them when
researching their antimicrobial activities. MOE studies
revealed that the same complex has the highest binding
interaction with minimum binding energy that can interact
with several receptors in the proteins studied.
DATA AVAILABILITY STATEMENT
The data that support the findings of this study are
available on request from the corresponding author. The
data are not publicly available due to privacy or ethical
restrictions.
FIGURE 6 A 3D plot of the interaction between 1,2,4-triazole
Schiff base ligand (L) with receptors of (a) 6NE0 and (b) 5UHF

MAHMOUD ET AL.
13 of 14
[23] Y. A. Ibrahim, A. A. Abbas, A. H. M. Elwahy, Carbo. Lett.
1999, 3, 331.
[24] X. X. Qi, N. Ren, D. H. Zhang, J. J. Zhang, RSC Adv. 2015, 9,
9261.
[25] N. F. Mahmoud, W. H. Mahmoud, G. G. Mohamed, Appl.
Organomet. Chem. 2020, 34.
[26] W. H. Mahmoud, R. G. Deghadi, G. G. Mohamed, Indian Jour-
nal of Chemistry 2020, 58, 1319.
AUTHOR CONTRIBUTIONS
Nessma Mahmoud: Formal analysis; investigation;
methodology; resources; software. Ashraf Abbas:
Formal analysis; methodology; resources; supervision.
Gehad Mohamed: Data curation; formal analysis;
resources; supervision; validation.
ORCID
[27] K. Bhattacharjee, W. Kaminsky, S. R. Joshi, A. K. Chandra,
K. M. Rao, Inorg. Chim. Acta 2016, 441, 95.
[28] P. Skehan, R. Storeng, J. Natl, Cancer Inst. 1990, 42, 1107.
[29] C. J. Dhanaraj, I. U. Hassan, J. Johnson, J. Joseph, R. S.
Nessma F. Mahmoud https://orcid.org/0000-0003-2876-
1971
Ashraf A. Abbas https://orcid.org/0000-0001-7061-9907
Gehad G. Mohamed https://orcid.org/0000-0002-1525-
5271
Joseyphus, J. Photochem.
162, 115.
& Photobio., B: Biology 2016,
[30] A. Albert, Selective Toxicity, 6th ed., Wiley: New York l979.
[31] J. Lakshmipraba, S. Arunachalam, R. V. Solomon, P.
Venuvanalingam, J. Coord. Chem. 2015, 68, 1374.
[32] W. H. Mahmoud, R. G. Deghadi, G. G. Mohamed, Arab. J of
Chem. 2020, 13, 5390.
[33] W. H. Mahmoud, N. F. Mahmoud, G. G. Mohamed, A. A. El-
Bindary, A. Z. El-Sonbati, Spectrochim Acta a: Mol. Biomol.
Spectrosc. 2015, 150, 451.
[34] W. H. Mahmoud, M. M. Omar, F. N. Sayed, J. Therm. Anal.
Calorim. 2016, 124, 1071.
[35] A. H. Ahmed, A. M. Hassan, H. A. Gumaa, B. H.
Mohamed, A. M. Eraky, A. A. Omran, Arab. J. of Chem.
2019, 12, 4287.
REFERENCES
[1] J. Xu, Y. Cao, Zhang, J Eur. J. Med. Chem 2011, 46, 3142.
[2] M. Ferreira, L. Pinheiro, O. Santos-Filho, M. Pecanha, C.
Sacramento, V. Machado, V. Ferreira, T. Souza, N. Boechat,
Med. Chem. Res. 2014, 23, 1501.
[3] S. Panda, S. Nayak, Supramole. Chem. 2015, 27, 679.
[4] Y. L. Wang, N. Zhang, Q. Y. Liu, Z. M. Shan, R. Cao, M. S.
Wang, J. J. Luo, E. L. Yang, Cryst. Growth des. 2011, 11, 130.
[5] S. A. Zabin, M. Abdelbaset, Euro. J. Chem. 2016, 7, 322.
[6] C. Malins, H. G. Glever, T. E. Keyes, J. G. Vos, W. J. Dressick,
B. D. MacCraith, Sensors & Actuator 2000, 69, 89.
[7] Y. Saegusu, S. Harada, S. J. Nakamma, Het Chem 1970,
27, 739.
[36] W. H. Mahmoud, N. F. Mahmoud, G. G. Mohamed,
J. Organomet. Chem. 2017, 31, e3858.
[37] W. H. Mahmoud, N. F. Mahmoud, G. G. Mohamed, J. of
Coord. Chem 2017, 70, 3552.
[38] W. H. Mahmoud, M. M. Omar, Y. M. Ahmed, G. G.
Mohamed, Appl. Organometal. Chem. 2020, 34, e5528.
[39] P. Geerlings, F. D. Proft, W. Langenaeker, Chem. Rev. 2003,
103, 1793.
[40] P. K. Chattaraj, S. Giri, J. Phys. Chem. A 2007, 111, 11116.
[41] O. Sahin, U. O. Ozdemir, N. Seferoglu, Z. K. Genc, K. Kaya, B.
Aydiner, S. Tekin, Z. Seferoglu, J. Photochem. & Photobio. B
2017, 178, 428.
[8] A. Beguma, B. Sreedhar, K. Laxmi, P. Mamatha, C. S. Devi,
Res. J. of Pharma., Bio. and Chem. Sci 2014, 5, 408.
[9] A. Y. Al-Dawood, N. M. El-Metwaly, H. A. El-Ghamry, J. Mol.
Liq. 2016, 220, 311.
[10] A. K. M. Nur Alam Siddiki, S. Rahman, A. Rahman, A. Salam,
A. Yousuf, F. Islam, A. Arafat, Bang. Pharm. J. 2012, 15, 83.
[11] M. Shebl, S. M. E. Khalil, S. A. Ahmed, H. A. A. Medien,
J. Mol. Str. 2010, 980, 39.
[12] S. K. Bharti, G. Nath, R. Tilak, S. K. Singh, Eur. J. Med. Chem.
2000, 45, 651.
[42] B. Babur, N. Seferoglu, E. Aktan, T. Hokelek, E. Sahin, Z.
Seferoglu, J. Mol. Str. 2015, 1081, 175.
[13] G. Kumar, V. Singh, K. Singh, I. Ahmad, D. S. Yadav, A.
Kumar, N. Shishodia, J. Pharm. 2012, 2, 45.
[43] S. Alturk, D. Avci, O. Tamer, Y. Atalay, O. Sahin, J. Phys.
Chem. Solids 2016, 98, 71.
[14] H. M. Refaat, H. A. El-Badway, S. M. Morgan, J. Mol. Liq.
2016, 220, 802.
[44] E. Ermis, J. Mol. Str. 2018, 1156, 91.
[15] K. Drlica, X. Zhao, Microbiol. Mol. Biol. Rev 1997, 61, 377.
[16] K. Sandstrom, S. Warmlander, M. Leijon, A. Graslund, Bio-
chem. Biophys. Res. Commun. 2003, 304, 55.
[17] Y. Xia, Z. Y. Yang, P. Xia, K. F. Bastow, Y. Tachibana, S. C.
Kuo, E. Hamel, T. Hackl, K. H. Lee, J. Med. Chem. 1998,
4, 1155.
[18] D. K. Saha, U. Sandbhor, K. Shirisha, S. Padhye, D.
Deobagkar, C. E. Anson, A. K. Powell, Bioorg. Med. Chem. Lett.
2004, 14, 3027.
[45] W. M. I. Hassan, E. M. Zayed, A. K. Elkholy, H. Moustafa,
G. G. Mohamed, Spectrochim Acta A: Mol. Biomol. Spectrosc.
2013, 103, 378.
[46] A. Z. El-Sonbati, W. H. Mahmoud, G. G. Mohamed, M. A.
Diab, S. M. Morgan, S. Y. Abbas, Appl. Organometal. Chem.
2019, 33, e5048.
[47] M. A. Alaghaz, H. A. Bayoumi, Y. A. Ammar, S. A. AldLmani,
J. Mol. Str. 2013, 1035, 383.
[48] P. Tyagi, S. Chandra, B. S. Saraswat, D. Yadav, Spectrochem.
Acta a 2015, l45, l55.
[19] I. Turel, A. Golobic, A. Klavzar, B. PiLar, P. Buglyo, E. Tolis,
D. Rehder, J. Inor Biochemistry 2003, 95, 199.
[49] Y. K. Abdel-Monem, S. A. Abou El-Enein, M. M. El-Sheikh-
Amer, J. Mol. Str. 2017, 1127, 386.
[20] Y. Wang, C.-W. Jin, S.-M. He, N. Ren, J.-J. Zhang, J. Mol. Str.
2016, 1125, 383.
[50] N. G. Zaki, W. H. Mahmoud, A. M. El Kerdawy, A. M.
Abdallah, G. G. Mohamed, Spectrochem. Acta a 2020, 229,
117938.
[21] M. Maity, M. C. Majee, S. Kundu, S. K. Samanta, E. C.
Sanudo, S. Ghosh, M. Chaudhury, Inorg. Chem. 2015, 54, 9715.
[22] S. Panda, S. Nayak, J. of Fluores. 2016, 26, 413.

14 of 14
MAHMOUD ET AL.
[51] M. A. Diab, G. G. Mohamed, W. H. Mahmoud, A. Z.
El-Sonbati, S. M. Morgan, S. Y. Abbas, Appl. Organometal,
Chem. 2019, 33, e4945.
[52] M. A. Diab, A. Z. El-Sonbati, A. A. El-Bindary, S. M. Morgan,
M. K. Abd El-Kader, J. Mol. Liq. 2016, 218, 571.
[53] A. A. Abdel Aziz, I. S. A. El-Sayed, M. M. H. Khalil, Appl.
Organometal. Chem. 2017, 31, e37301.
[54] W. H. Mahmoud, G. G. Mohamed, M. M. I. El-Dessouky, Spe-
ctrochim. Acta a 2014, 122, 598.
[55] A. M. A. Alaghaz, H. A. Bayoumi, Y. A. Ammar, S. A.
AldLmani, J. Mol. Str. 2013, 1035, 383.
[72] A. A. Abou-Hussein, W. Linert, Spectrochim. Acta a 2015,
141, 223.
[73] R. M. Ramadan, A. K. A. Al-Nasr, A. F. H. Noureldeen,
Spectrochim. Acta a 2014, 11, 417.
[74] K. Dhahagani, S. M. Kumar, G. Chakkaravarthi, K. Anitha, J.
Rajesh, A. R. G. Rajagopal, Spectrochim. Acta a 2014, 117, 87.
[75] W. H. Mahmoud, R. G. Deghadi, G. G. Mohamed, Res. Chem.
Intermed. 2016, 42, 7869.
[76] I. Muhammad, I. Javed, I. Shahid, I. Nazia, Turk. J. Biol. 2007,
31, 67.
[77] T. D. Thangadurai, K. Natarajan, Indian J. Chem. A 2001,
40, 573.
[78] Z. H. Chohan, H. Pervez, A. Rauf, K. M. Khan, C. T. Supuran,
J. Enzyme Inhib. Med.Chem. 2004, 19, 417.
[56] M. Hanif, Z. H. Chohan, Spectrochim. Acta a 2013, 104, 468.
[57] W. H. Mahmoud, F. N. Sayed, G. G. Mohamed, Appl.
Organomet. Chem. 2016, 30, 959.
[58] W. H. Mahmoud, R. G. Deghadi, G. G. Mohamed, Appl.
Organomet. Chem. 2016, 30, 221.
[79] L. Messori, P. Orioli, D. Vullo, E. Alessio, E. Iengo, Eur.
J. Biochem. 2000, 267, 1206.
[59] G. Y. Nagesh, B. H. M. Mruthyunjayaswamy, J. Mol. Str. 2015,
1085, 198.
[60] D. X. West, A. A. Nasar, Transition Met. Chem. 1999, 24, 617.
[61] P. P. Netalkar, S. P. Netalkar, V. K. Revankar, Polyhedron
2015, 100, 2l5.
[80] J. Haines, Biocycle 1995, 6, 32.
[81] D. R. Hospenthal, K. J. Kwon-Chung, J. E. Bennett, Med
Mycol. 1998, 36, 165.
[82] J. P. Latgé, Clin Microbiol Rev. 1999, 12, 310.
[83] W. H. Mahmoud, R. G. Deghadi, G. G. Mohamed, J Therm
Ana1 Ca1orim 2016, 127, 2149.
[62] W. A. Hayes, D. S. Mills, R. F. Neville, J. Kiddie, L. M. Collins,
Anal. Biochem. 2011, 416, 202.
[84] I. Smith, Clin. Microbiol. Rev. 2003, 16, 463.
[63] W. H. Mahmoud, N. F. Mahmoud, G. G. Mohamed, A. Z.
El-Sonbati, A. A. El-Bindary, J. Mol. Str. 2015, 1095, 15.
[64] F. N. Sayed, W. H. Mahmoud, M. M. Omar, G. G. Mohamed,
Appl. Organomet. Chem. 2019, 33, e5143.
[65] N. F. Mahmoud, O. A. Fouad, A. E. Ali, G. G. Mohamed, Ind.
Eng. Chem. Res. 2020 Article in press (doi.org/10.1021/acs.iecr.
0c06288).
SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.
[66] W. H. Mahmoud, N. F. Mahmoud, G. G. Mohamed, J. Chin.
Chem. Soc. 2019, 66, 945.
[67] Z. Parsaee, K. Mohammadi, J. Mol. Str. 2017, 1137, 512.
[68] N. M. El-Metwaly, M. G. El-Ghalban, J. Mol. Liq. 2016,
220, 265.
[69] N. Dharmaraj, P. Viswanathamurthi, K. Natarajan, Trans.
Met. Chem. 2001, 26, 105.
[70] Z. H. Chohan, K. M. Khan, C. T. Supuran, Appl. Organomet.
Chem. 2004, 18, 305.
How to cite this article: Mahmoud NF,
Abbas AA, Mohamed GG. Synthesis,
characterization, antimicrobial, and MOE
evaluation of nano 1,2,4-triazole-based Schiff base
ligand with some d-block metal ions. Appl
Organomet Chem. 2021;e6219. https://doi.org/10.
1002/aoc.6219
[71] R. G. Deghadi, W. H. Mahmoud, G. G. Mohamed, Appl.
Organomet. Chem. 2020, 34, e5883 1-20.