Polymer complexes. LXIX. Some divalent metal(II) polymer complexes of potentially bidentate monomer N-[4-(5-methyl-isoxazol-3-ylsulfamoyl)-phenyl]-acrylamide: Synthesis, spectroscopic characterization, thermal properties, antimicrobial agents and DNA studies

Article abstract of DOI:10.1002/aoc.4207

Monomer of N-[4-(5-methyl-isoxazol-3-ylsulfamoyl)-phenyl]-acrylamide (HL) and some transition metal polymeric complexes of the general formula {[M(HL)(OH₂)₂(OCOCH₃)₂] xH₂O}_n (M = Co(II), x = 2; Ni(II), x = 3; Mn(II), x = 2) and [Cd(HL)₂(OCOCH₃)₂] were synthesized and characterized by elemental analysis, IR, UV spectroscopy, conductance measurements, magnetic susceptibility, thermogravimetric analyses and X-ray diffraction analysis. In all polymer complexes, the spectral data revealed that the ligand act as bidentate neutral molecule and coordinate to metal ion through enolic sulphonamide OH and isoxazol-N. In all polymer complexes, the spectral data revealed that the ligand act as bidentate neutral molecule and coordinate to metal ion through enolic sulphonamide OH and isoxazol-N. The molar conductance data revealed that the polymer complexes are non-electrolytes while UV-vis and magnetic measurements data have been shown that the polymer complexes have octahedral geometry. All the studies revealed coordination six for the metals in all the polymer complexes and octahedral structures were suggested. The inhibitive effect of HL against C38 steel was investigated in 2?M HCl solution (tafel polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) methods). The type of HL is mixed inhibitor whose adsorption habit onto C38 steel.

Full text of DOI:10.1002/aoc.4207

Received: 6 October 2017
DOI: 10.1002/aoc.4207
Revised: 8 November 2017
Accepted: 9 November 2017
F U L L P A P E R
Polymer complexes. LXIX. Some divalent metal(II) polymer
complexes of potentially bidentate monomer N‐[4‐(5‐
methyl‐isoxazol‐3‐ylsulfamoyl)‐phenyl]‐acrylamide:
Synthesis, spectroscopic characterization, thermal
properties, antimicrobial agents and DNA studies
A.Z. El‐Sonbati1
| M.A. Diab1
| Sh.M. Morgan2
| A.M. Eldesoky3,4 | M.Z. Balboula1
1 Chemistry Department, Faculty of
Science, Damietta University, Egypt
2 Environmental Monitoring Laboratory,
Ministry of Health, Port Said, Egypt
3 Engineering Chemistry Department,
High Institute of Engineering &
Technology (New Damietta), Egypt
4 Al‐Qunfudah Center for Scientific
Research (QCSR), Chemistry Department,
Al‐Qunfudah University College, Umm
Al‐Qura University, Kingdom of Saudi
Arabia
Monomer of N‐[4‐(5‐methyl‐isoxazol‐3‐ylsulfamoyl)‐phenyl]‐acrylamide (HL)
and some transition metal polymeric complexes of the general formula
{[M(HL)(OH2)2(OCOCH3)2] xH2O}n (M = Co(II), x = 2; Ni(II), x = 3; Mn(II), x
= 2) and [Cd(HL)2(OCOCH3)2] were synthesized and characterized by elemental
analysis, IR, UV spectroscopy, conductance measurements, magnetic suscepti-
bility, thermogravimetric analyses and X‐ray diffraction analysis. In all polymer
complexes, the spectral data revealed that the ligand act as bidentate neutral
molecule and coordinate to metal ion through enolic sulphonamide OH and
isoxazol‐N. In all polymer complexes, the spectral data revealed that the ligand
act as bidentate neutral molecule and coordinate to metal ion through enolic
sulphonamide OH and isoxazol‐N. The molar conductance data revealed that
the polymer complexes are non‐electrolytes while UV‐vis and magnetic mea-
surements data have been shown that the polymer complexes have octahedral
geometry. All the studies revealed coordination six for the metals in all the poly-
mer complexes and octahedral structures were suggested. The inhibitive effect of
HL against C38 steel was investigated in 2 M HCl solution (tafel polarization,
electrochemical impedance spectroscopy (EIS) and electrochemical frequency
modulation (EFM) methods). The type of HL is mixed inhibitor whose adsorp-
tion habit onto C38 steel.
Correspondence
A. Z. El‐Sonbati, Chemistry Department,
Faculty of Science, Damietta University,
Egypt
Email: elsonbatisch@yahoo.com
KEYWORDS
corrosion inhibition, molecular docking, polymer complexes, thermal properties, thermodynamic
parameters
1 | INTRODUCTION
Also, the metal chelates of sulphadrugs compounds
showed strong bacteriostatic efficiency than the
Sulphadrugs have a broad spectrum effect against
many bacterial strains[1] and they are widely used in treat-
ment of various bacterial infections.[2–4] Metal of drug
interactions were emerged as a new field of study.[5–8]
sulphadrugs compounds.[9,10]
Coordination supramolecules and polymers based on
transition metals compounds were discussed.[11,12] The
styling of coordination polymers is based on transition
Appl Organometal Chem. 2018;e4207.
wileyonlinelibrary.com/journal/aoc
Copyright © 2018 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4207

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EL‐SONBATI ET AL.
metals. The polymer complexes of sulphadrugs with a series
of metal ion were studied.[13–19] DNA is the main target mol-
ecule for most anticancer and antiviral therapies according
to cell biology.[20] The interactions of DNA with transition
metal complexes and different types of interaction of these
metal complexes with DNA have been informed.
isoxazol‐3‐yl)‐benzenesulfonamide in dry benzene until
the evolution of hydrogen chloride ceased,[18] forming a
white powder of monomer yield ~ 65 % and m.p. 220 °C.
Microanalysis for C13H14N3SO4; Found: C, 50.72; H,
4.65; N, 13.85; S, 10.63. Calc. for HL: C, 50.81; H, 4.23;
N, 13.68; S, 10.42%. Mass spectrum, the ion of m/z =
307 undergoes fragmentation to a stable peak at m/z =
252, 173, 97 and 82 by losing C2H3CO, C5H5N, CSO2
and NH atoms, respectively. IR [υmax. (cm‐1) (KBr)]:
3283‐3178 (N‐H str. sym.), 3055 (=C‐H str.), 2977 (C‐H
str. ‐CH3), 2874 (C‐H str.‐ CH2), 1518, 1591 (C=C Ph.
ring), 2776 (C‐H str. sym.) 1473 (oxazole ring str.), 1369
(S=O asym.), 1162 (S=O sym.), 1095 (C‐H) oxazole),
1033 (ring skeletol oxazol), 795 cm‐1 (N‐H wag.), 1390,
1165 cm‐1 (N‐O isoxazole).
Organic inhibitors are applied extensively to keep
metals from corrosion in many aggressive acidic media;
these organic inhibitors are compounds containing nitro-
gen, sulfur or oxygen.[21,22] Regrettably, most of the
organic used inhibitors are very expensive and health haz-
ards. The toxicity of these organic inhibitors restricts the
field of their application. So it was necessary to find low‐
cost inhibitors of the non‐hazardous type for the protection
of metals against corrosion. These requirements were satis-
fied by sulfa drugs compounds which have a large number
of functional adsorption centers (e.g. –NH2 group, –SO2–
NH– group, O and/or N‐ hetero atoms and aromatic rings).
In this study describes the coordination behavior of
monomer with Co(II), Ni(II), Mn(II) and Cd(II) acetate.
The structure of the studied polymer complexes is eluci-
dated using elemental analysis, IR, UV spectroscopy, con-
ductance measurements, magnetic susceptibility, X‐ray
diffraction and thermal analysis measurements. Thermal
decomposition and thermodynamic parameters of the
polymer complexes are discussed. The protection effect
and electrochemical habit of HL for C38 steel contain
2 M HCl acid is given by the tafel polarization, EIS and
EFM tests are studied.
1H NMR: δ (ppm) 7.43‐7.80 (d, Ar, 4H), 6.10, 6.30 (s,
CH2=, 2H), 5.80 (s, =CH, 1H), 10.65, 10.85 (s, SO2NH,
1H, exchangeable with D2O), 5.18 (s, CONH, 1H,
exchangeable with D2O), 6.26 (s, =CH oxazole ring, 1H)
and 2.10 (s, CH3, 3H). 13C NMR (DMSO‐d6): δ (ppm)
170.0 (3C), 168.0 (10C), 158.6 (7C), 153.8 (4C), 132.6 (1C),
127.6 (2C), 128.8 (5,9C), 126.2 (12C), 119 (6,8C) and 13.7
(13C) (Figure 1)
2.3 | Polymerization
Monomer was homopolymerized by the method
described by Diab, El‐Sonbati and co‐workers.[11,12,18]
The IR spectrum of the homopolymer was almost the
same as that of the monomer except the absence of a peak
at 1585 cm‐1 which assigned to the participation of (C=C)
in the polymerization.
2 | EXPERIMENTAL
The experimental technique has been described
previously.[11,12,18]
2.4 | Isolation of polymer complexes
Polymer complexes were prepared by refluxing the mono-
mer with Co(II), Ni(II), Mn(II) and Cd(II) acetate in DMF
as a solvent, and 0.1 % (w/v) initiator (2,2'‐azobisisobuty-
ronitrile (AIBN)). The resulting mixture was heated at
reflux for ~ 8 hrs. The hot solution was precipitated by
pouring in large excesses of distilled water containing
dilute hydrochloric acid, to remove the metal salts that
were incorporated into the polymer complexes. The poly-
mer complexes (Figure 1) were filtered, washed with
water, and dried in a vacuum oven at 40 °C for several days.
2.1 | Material and methods
4‐Amino‐N‐(5‐methyl‐isoxazol‐3‐yl)‐benzenesulfonamide
was bought Aldrich and used without further purification.
Acryloyl chloride (Aldrich Chemical Co. Inc.) was used
without further purification. 2,2'‐Azobisisobutyronitrile
(AIBN) was purified by dissolving in hot ethanol and fil-
tering.[11] The solution was left to cool. Co(OCOCH3)2.
4H2O, Ni(OCOCH3)2. 4H2O, Mn(OCOCH3)2. 4H2O and
Cd(OCOCH3)2.2H2O (Sigma Aldrich), and sodium car-
bonate (Merck) (BDH). Organic solvents were spectro-
scopic pure from BDH included ethanol, diethyl ether
and dimethylformamide.
2.4.1 | {[Co(HL)(OCOCH3)2(H2O)2] 2H2O}n
(1)
Anal. calcd. for C17H27N3SO12Co: C, 36.70; H, 4.14; N, 7.55;
S, 5.76; Co, 10.60%. Experimental: C, 36.64; H, 4.04; N, 7.35;
S, 5.56; Co, 10.91%. IR [υmax. (cm‐1) (KBr)]: 3060 (OH str.
enolic.), 2930 (C‐H str. ‐CH3), 2927 (C‐H str.‐ CH2), 1475,
2.2 | Preparation of monomer
HL monomer was prepared by the reaction of equimolar
amounts of acryloyl chloride and 4‐amino‐N‐(5‐methyl‐

EL‐SONBATI ET AL.
3 of 23
FIGURE 1 Structure of the monomer, homopolymer (PHL) and polymer complexes
1412 (oxazole ring str.), 1311 (S=O asym.), 1162 (S=O sym.),
1094 (C‐H) oxazole), 1020 (ring skeletol oxazol), 1531
(CH3COO‐ sym.), 1311 (CH3COO‐ asym.), 3315 (OH water),
835 (OH rocking water), 794 (N‐H wag.). 592 (Co‐O), 440
(Co‐N). Molar Cond. (10‐3 M, DMSO): 20.33 Ω‐1 cm2 mol‐1.
μeff. = 4.80 BM., UV‐Vis. (cm‐1): Racah parameter < free
ion value, β < 1, υ2/υ1 = 2.04.
wag.). 594 (Ni‐O), 445 (Ni ‐N). Molar Cond. (10‐3 M,
DMSO): 10.50 Ω‐1 cm2 mol‐1. μeff. = 2.88 BM,. UV.vis.
(cm‐1): Racah parameter < free ion value, β < 1, υ2/υ1 =
1.59.
2.4.3 | {[Mn(HL)(OCOCH3)2(H2O)2] 2H2O}n
(3)
2.4.2 | {[Ni(HL)(OCOCH3)2(H2O)2] 3H2O}n
Anal. calcd. for C17H27N3SO12Mn: C, 36.96; H, 4.17; N,
7.61; S, 5.80; Mn, 9.95%. Experimental: C, 36.88; H, 4.11;
N, 7.44; S, 5.65; Mn, 10.18%. IR [υmax. (cm‐1) (KBr)]:
3108 (OH str. enolic.), 2910 (C‐H str. ‐CH3), 2890(C‐H
str.‐ CH2), 1470, 1396 (oxazole ring str.), 1330 (S=O
asym.), 1162 (S=O sym.), 1088 (C‐H) oxazole), 1034 (ring
skeletol oxazol), 1524 (CH3COO‐ sym.), 1330 (CH3COO‐
asym.), 3265 (OH water), 835 (OH rocking water), 796
(N‐H wag.). 569 (Mn‐O), 480 (Mn‐N). Molar Cond. (10‐3 M,
DMSO): 8.44 Ω‐1 cm2 mol‐1. μeff. = 5.91 B.M., UV.vis. (cm‐1):
(2)
Anal. calcd. for C17H29N3SO13Ni: C, 35.56; H, 4.01; N,
7.32; S, 5.58; Ni, 10.23%. Experimental: C, 35.44; H, 3.84;
N, 7.04; S, 5.35; Ni, 10.60%. IR [υmax. (cm‐1) (KBr)]: 3080
(OH str. enolic.), 2908 (C‐H str. ‐CH3), 2880 (C‐H str.‐
CH2), 1481, 1411 (oxazole ring str.), 1307 (S=O asym.),
1132 (S=O sym.), 1095 (C‐H) oxazole), 1025 (ring skeletol
oxazol), 1536 (CH3COO‐ sym.), 1308 (CH3COO‐ asym.),
3404 (OH water), 835 (OH rocking water), 764 (N‐H

4 of 23
EL‐SONBATI ET AL.
Racah parameter < free ion value, β < 1, F2 = 1166,
F4 = 97, B = 68, C = 3401.
concentration was determined by UV absorbance at
260 nm (Ɛ = 6600 M−1 cm−1).[24] Electronic absorption
spectra were carried out using 1 cm quartz cuvettes at
25 °C by fixing the concentration of Schiff base or com-
plexes (1.00 × 10−3 mol L−1), while gradually increasing
the concentration of CT‐DNA (0.00 to 1.30 × 10−4 mol L−1).
An equal amount of CT‐DNA was added to both the
compound solutions and the references buffer solution
to eliminate the absorbance of CT‐DNA itself. The intrin-
sic binding constant (Kb) of the compound with CT‐DNA
was determined using the following equation:[24]
2.4.4 | {[Cd(HL)2(OCOCH3)2] 3H2O}n (4)
Anal. calcd. for C30H38N6S2O15Cd: C, 40.07; H, 3.56; N,
9.35; S, 7.12; Cd, 12.51%. Experimental: C, 39.97; H,
3.44; N, 9.15; S, 6.88; Cd, 13.04%. IR [υmax. (cm‐1) (KBr)]:
3112 (OH str. enolic.), 2925 (C‐H str. ‐CH3), 2890 (C‐H
str.‐ CH2), 1473, 1404 (oxazole ring str.), 1313 (S=O
asym.), 1164 (S=O sym.), 1067 (C‐H) oxazole), 1055 (ring
skeletol oxazol), 1535 (CH3COO‐ sym.), 1313 (CH3COO‐
asym.), 3270 (OH water), 792 (N‐H wag.). 586 (Cd‐O),
435 (Cd‐N). Molar Cond. (10‐3 M, DMSO): 15.30 Ω‐1
cm2 mol‐1. μeff. = diamagnetic
½DNAꢀ
½DNAꢀ
1
ꢀ
ꢁ
ꢀ
ꢁ
ꢀ
ꢁ
¼
þ
(1)
εa−εf
εb−εf
Kb εa−εf
where [DNA] is the concentration of CT‐DNA in base pairs,
єa is the molar extinction coefficient observed for the Aobs
2.5 | Biological activity investigation
/
For this investigation the agar well diffusion method was
applied.[23,24] The antibacterial activities of the investi-
gated compounds were tested against three local Gram
positive bacterial species (Bacillus cereus, Staphylococcus
aureus and Enterococcus faecalis) and three local Gram
negative bacterial species (Escherichia coli, Klebsiella
pneumoniae and Pseudomonas aeruginosa) on nutrient
agar medium. Also, the antifungal activities were tested
against three local fungal species (Aspergillus niger, Fusar-
ium oxysporum and the yeast Candida albicans) on DOX
agar medium. The concentrations of each solution were
50, 100 and 150 μg/ml in buffered dimethylformamide
(DMF) solution. By using a sterile cork borer (10 mm
diameter), wells were made in agar medium plates previ-
ously seeded with the test microorganisms. 200 μl of each
compound was applied in each well. The agar plates were
kept at 4 °C for at least 30 min to allow the diffusion of the
compound to agar medium. The plates were then incu-
bated at 37 °C or 30 °C for bacteria and fungi, respectively.
The diameters of inhibition zone were determined after
24 h and 7 days for bacteria and fungi, respectively, taking
the consideration of the control values (DMF).
Dimethylformamide (DMF) was used as a blank and pen-
icillin was used as the antibacterial standard drug and
miconazole was used as the antifungal standard drug.
[compound] at the given DNA concentration, єf is the molar
extinction coefficient of the free compound in solution and
єb is the molar extinction coefficient of the compound when
fully bond to DNA. In plots of [DNA]/(єa–єf) versus [DNA],
Kb is given by the ratio of the slope to the intercept.
2.7 | Measurements
Microanalyses of carbon, hydrogen, nitrogen and sulfur
were carried out using a CHNS‐932 (LECO) Vario Ele-
1
mental Analyzer at the Microanalytical Center. H NMR
spectra were on record with a 330 MHz Varian‐Oxford
Mercury. Infrared spectra were recorded as KBr discs
using a Perkin‐Elmer 1340 spectrophotometer. Mass spec-
tra were recorded by the EI technique at 70 eV using MS‐
5988 GS‐MS Hewlett‐Packard. Ultraviolet‐visible (UV‐
Vis) spectra of the compounds were recorded in nujol
mulls using a Unicom SP 8800 spectrophotometer. Mag-
netic moment of the prepared solid complexes was deter-
mined at room temperature using the Gouy's method.
Mercury(II) (tetrathiocyanato)cobalt(II), [Hg{Co(SCN)4}],
was used for the calibration of the Gouy tubes. Diamag-
netic corrections were calculated from the values given
by Selwood[25] and Pascal's constants.
Magnetic moments were calculated using the equa-
tion, μeff. = 2.84 [TcM ]
coor. 1/2. The conductance was
achieved using Sergeant Welch scientific Co., Skokie, IL,
USA. Simultaneous Thermal Analyzer (STA) 6000 system
was used in computing the thermal studies by thermogra-
vimetric analysis (TGA) method. Thermal properties were
studied from 50 °C to 800 °C at the heating rate of 15 °C/
min under dynamic nitrogen atmosphere. X‐ray diffrac-
tion analysis of compounds powder forms was recorded
on X‐ray diffractometer analysis in the range of diffraction
angle 2θo = 4–80o.[24] This analysis was carried out using
2.6 | DNA binding measurements
The binding properties of the monomer (HL) and com-
plexes (1–4) to CT‐DNA have been studied using elec-
tronic absorption spectroscopy. The stock solution of
CT‐DNA was prepared in 5 mM Tris–HCl/50 mM NaCl
buffer (pH = 7.2), which a ratio of UV absorbance at 260
and 280 nm (A260/A280) of ca. 1.8–1.9, indicating that the
DNA was sufficiently free of protein and the

EL‐SONBATI ET AL.
5 of 23
CuKα radiation (λ = 1.540598 Ả). The applied voltage and
the tube current are 40 kV and 30 mA, respectively.
Docking calculations were carried out on receptors of
crystal structures of Escherichia coli (3t88) and Staphylococcus
aureus (3q8u) proteins models. The MMFF94 Force field was
used for energy minimization of compound molecule using
Docking Server. Affinity (grid) maps of 20 × 20 × 20 Å grid
points and 0.375 Å spacing were generated using the Autogrid
program.[26–28] Auto Dock parameter set‐ and distance‐
dependent dielectric functions were used in the calculation
of the van der Waals and the electrostatic terms, respectively.
Escherichia coli (3t88) and Staphylococcus aureus (3q8u).
The docking study showed a favorable interaction
between start and forms A and B with the receptors
(3t88 and 3q8u) as shown in Figures 2–4 and energy is
given in Table 1. 2D plot curves for start and forms A
and B of monomer are shown in Figures 5–7.
3.2 | Structure and characterization of
polymer complexes
3.2.1 | Elemental analyses
The analytical data of the isolated polymer complexes are
shown in Section 2. The formation of these polymer com-
plexes may propose according to the following equations:
2.8 | Electrochemical tests
Electrochemical tests were lead to three electrodes cell
thermostatic utilized a Gamrypotentiostat/galvanostat/
ZRA (model PCI300/4). A saturated calomel and plati-
num electrode were utilized as reference and auxiliary
electrodes. The C38 steel electrodes were 10 x 10 ml and
were welded with a copper wire on one side. All method
CoðCH3COOÞ2:4H2O
ꢄꢂ
ꢃ
ꢅ
þ HL →
CoðHLÞðOCOCH3Þ2ðH2OÞ2 2H2O
n
(1)
NiðCH3COOÞ2:4H2O
ꢄꢂ
ꢃ
ꢅ
was done at temperature (30
1 °C). The potentiody-
þ HL →
NiðHLÞðOCOCH3Þ2ðH2OÞ2 3H2O
n
namic diagrams were measured from ‐50 to 50 V at a rate
scan 1 mV S‐1 after the steady state is approached (30 min)
and the open potential circuit was observed after putted
the electrode for 15 min in the solution test.
(2)
MnðCH3COOÞ2:4H2O
EFM and EIS tests were obtained by utilized the same
methods as before with a Gamry framework system
depends on ESA400. EchemAnalyst 5.5 Software was uti-
lized for drawing, graphing and fitting data. EIS tests were
done in a range of frequency of 100 kHz to 10 mHz with
amplitude of 5 mV peak‐to‐peak ac signals utilized at
respective for potential corrosion. EFM had done utilized 2
frequencies 2 and 5 Hz. The frequency base was 1 Hz. In this
research, we utilized a signal perturbation with amplitude
of 10 mV for both frequencies perturbation of 2 and 5 Hz.
ꢄꢂ
ꢃ
ꢅ
þ HL →
MnðHLÞðOCOCH3Þ2ðH2OÞ2 2H2O
n
(3)
CdðCH3COOÞ2:2H2O
ꢄꢂ
ꢃ
ꢅ
þ HL →
CdðHLÞ2ðOCOCH3Þ2 3H2O
(4)
n
The general formulae of the polymeric complexes can
be depicted as shown in (Figure 1). The C, H, N, S, and
metal contents of polymer complexes gave satisfactory
elemental analysis, suggesting 1:1/1:2 (metal: ligand) stoi-
chiometry with the structure predicted (Figure 1). All the
isolated polymer complexes are air stable for extended
periods and remarkably soluble in DMSO and DMF.
3 | RESULTS AND DISCUSSION
3.1 | Characterization of monomer
The monomer is characterized as in Section 2. The mono-
mer was then polymerized as in Section 2. The monomer
was then polymerized by radical polymerization initiated
by 2,2'‐azobisisobutyronitrile (AIBN). The homopolymer
has been characterized by various techniques.[16,18] The
proposed formula was confirmed by mass spectrum of
monomer showing a peak at 307 amu corresponding to
the molecular ion peak of the monomer moiety
([C13H13N3O4S] atomic mass 307 amu). The observed
peak was in good agreement with the proposed formula
as indicated by the analytical data. The results showed a
possible arrangement between the start and monomer
(forms A and B) with receptors of crystal structures of
3.2.2 | Molar conductance measurements
The conductance measurements recorded for 10‐3 M solu-
tions of the polymer complexes in DMSO are less polar.
Very low molar conductance (ΛM) values in the range of
8.44 to 20.33 ohm‐1 cm2 mol‐1 in polymer complexes, that
they are non‐electrolytic. Hence the two acetate groups in
the inside coordination sphere and confirmed by analytical
data. The low ΛM values may be attributed to the large cat-
ions.[1] The electrical conductivity of these polymer com-
plexes found in order: Co(II) > Cd(II) > Ni(II) > Mn(II).

6 of 23
EL‐SONBATI ET AL.
FIGURE 2 The start (green in (a) and gray in (b)) in interaction with receptors of crystal structures of Escherichia coli (3t88) and
Staphylococcus aureus (3q8u)
sharp bands at 1369 [υasym(SO2] and 1162 [υsym(SO2)]
cm‐1. In the polymer complexes, the asymmetric and sym-
metric modes are shifted, upon coordination to the transi-
tion metals.[30] The shift of the SO2 stretching vibration to
lower frequencies due to the transformation of the sulfon-
amide (‐SO2NH) to the enol form (‐SO(OH)=N) as a result
of complex formation to give more stable six‐membered
ring.[30] The band related to isoxazol ring stretching vibra-
tions in the free monomer appeared at ~ 1473 cm‐1 suf-
fered a shift at 1481‐1470 and 1412‐1396 cm‐1 in the
spectra of polymer complexes indicating that the
isoxazole moiety is participation in coordination.[31] In
all the polymer complexes (1‐3) the lattice/coordinated
water molecules are indicated by the appearance of a
broad band centered at ~3315‐3403 cm‐1[24] as confirmed
by thermal analysis. The rocking mode of coordination
water is also observed in the range ~ 835 cm‐1.[24] It is
assumed that the υ(NH) of CONH is merged with υ(OH)
of coordinated water. The υ(C=O) of the CONH group is
not changed. The coordination of acetate group is indi-
cated by the appearance of two additional bands due to
υ(COO‐)sym and υ(COO‐)asym at 1535‐1523 and 1330‐
1311 cm‐1, respectively, in all the polymer complexes.
The magnitude of Δυ = 205‐212 cm‐1 suggests the
coordination of the acetate group in the unidentate
fashion.[32] In the spectra of all polymer complexes,
3.3 | IR spectral studies
In the absence of a powerful technique such as X‐ray crys-
tallography. IR spectroscopy has proven to be the most
suitable technique to give enough information to eluci-
date the nature of bonding of monomer to metal ion.
The IR spectrum of monomer exhibits four potential
donor sites, oxygen of the enolic (OH) group, nitrogen of
isoxazole, sulphonamide (SO2), and CONH groups
(Figure 8). The CONH band nearly not changed indicat-
ing it is not involved in coordination. In the spectrum of
monomer a broad band is observed in the region 3283‐
3178 cm‐1. This band attributed to υ(NH).
The IR data of the monomer and its polymer com-
plexes are listed in Table 2. The IR spectra of the polymer
complexes are compared with those of the monomer in
order to determine the coordination sites that may
involved in chelation. There are some guide peaks, in
the spectra of the monomer, which are of good help for
achieving this goal. The sharp peaks 1591 and 1518 cm‐1
were due to the aromatic C=C stretching vibrations.[29]
The absorption band at ~ 3283 cm‐1; υ(NH) of the
sulphonamide group in the free monomer, was disap-
peared or hidden under the peak of water molecules.
The presence of coordinated water molecules renders it
difficult to confirm the enolization of the sulfonamide
group. The SO2 group modes of the monomer appear as
appearance
of
new
bands
in
the
region

EL‐SONBATI ET AL.
7 of 23
FIGURE 3 The HL (form A) (green in (a) and gray in (b)) in interaction with receptors of crystal structures of Escherichia coli (3t88) and
Staphylococcus aureus (3q8u)
586‐562 and 465‐445 cm‐1 has been attributed to M‐O
and M‐N bonds, respectively.[33,34] From the IR spectral
data it is concluded that monomer (HL) (form B)
due to the interaction of monomer with Ni(II), Co(II)
and Mn(II) metal ions.
The electronic spectrum of Ni(II) polymer complex
act as
a
bidentate ligand in polymer complexes,
exhibits bands at 10800 cm‐1 [3A2g
→
3T2g(F)(υ1)],
3
coordinating through enolic sulphonamide‐OH and
isoxazol‐N moiety.
17200 cm‐1 [3A2g → T1g(F)(υ2)] and 263000 cm‐1 [3A2g
3
[36]
→ T1g(P)(υ3)] transitions in an octahedral field.
The
In 1H NMR spectrum of monomer the absorption
peaks at 10.64 ‐ 11.25 ppm, assignable to hydrogen
bonded NH or OH protons (Figure 1 and Figure 9a).
These signals disappeared on repeating the measurements
in the presence of D2O (Figure 9b).
υ2/υ1 ratio is 1.59 which occurs in the usual range (1.60‐
[24]
1.82) expected for octahedral Ni(II) complexes.
The
spectral parameters of the Ni(II) polymer complex as cal-
[37]
culated according to the method of Lever
are as fol-
lows: Dq = 1080 cm‐1, Bo = 740 cm‐1, β = 0.71 and
LFSE (kcal mol‐1) = 37.12. The reduction of the Racah
parameter from the free ion value of 1038 cm‐1 and the
βo = 29% are indicative of the presence of strong cova-
lency in the polymer complex.
3.4 | Electronic spectra and magnetic
measurements
The electronic spectrum of the free monomer exhibited
two absorption bands at ~ 46500 cm‐1 assigned to the
π→π* transition for the intra‐ligand of aromatic system
C=C character and a strong band at ~ 37040 cm‐1 is refer
to n→π* transition for oxygen atom of S=O/C=O group
or nitrogen atom of imine –N=C groups, respectively.[35]
Upon complexation, there are some electronic changes
Co(II) polymer complex exhibits absorption bands at
4
9010 cm‐1 [4T1g(F) → T2g(F)(υ1)], 18350 cm‐1 [4T1g(F) →
4A2g(F)(υ2)] and 21250 cm‐1 [4T1g(F) → 4T1g(P)(υ3)] transi-
tions, and the magnetic moment for the Co(II) polymer
complex in the 4.80 B.M. supporting octahedral geome-
try.[38] The ligand field splitting energy (10Dq =
9340 cm‐1), interelectronic repulsion parameters (Bo
=

8 of 23
EL‐SONBATI ET AL.
FIGURE 4 The HL (form B) (green in (a) and gray in (b)) in interaction with receptors of crystal structures of Escherichia coli (3t88) and
Staphylococcus aureus (3q8u)
TABLE 1 Energy values obtained in docking calculations of start and HL (form A and form B) with receptors of crystal structures of
Escherichia coli (3t88) and Staphylococcus aureus (3q8u)
Total
Est. Free Energy Est. inhibition
vdW+ bond+
desolv energy
(kcal/mol)
Electrostatic
Energy (kcal/
mol)
intercooled
Energy (kcal/
mol)
of Binding (kcal/
mol)
constant (Ki)
Interact
surface
Compounda Receptors
(μM)
Start
3 t88
3q8u
‐4.27
‐5.41
743.12
107.62
‐5.15
‐5.46
‐0.20
‐0.90
‐5.35
‐6.36
560.196
627.268
HL (form A) 3 t88
3q8u
‐5.04
‐5.50
202.19
93.57
‐5.88
‐6.22
‐0.88
‐0.76
‐6.77
‐6.97
574.327
725.422
HL (form B) 3 t88
3q8u
‐5.11
‐5.79
178.63
56.78
‐6.63
‐7.24
‐0.04
‐0.10
‐6.67
‐7.34
701.529
759.070
aSymbols as given in Figure 1.
838 cm‐1) and covalency factor (nephelauxetic ratio) (β =
0.75) and LFSE (kcal mol‐1) = 26.75 for the octahedral
Co(II) polymer complexes have been calculated using
the secular equation given by Konig.[39] The υ2/υ1 ratio
is 2.04 which occurs in the usual range expected for octa-
hedral Co(II) complexes.
moment is 5.91 B.M., indicating the presence of five
unpaired spins and hence there is high‐spin complex.
The experimentally observed transition energies are
used to calculate the values of parameters B, C, Dq and
β. Various ligand field parameters were calculated for
the polymer complexes and the value of Dq in Co(II) poly-
[40]
Mn(II) polymer complex shows four electronic absorp-
mer complex was calculated from transition energy
4
tion bands at 19602 cm‐1 [6A1g → T2g(G)], 23805 cm‐1
and in Ni(II) and Mn(II) Dq obtained from the first tran-
sition. The Naphelauxetic (β) was readily obtained by
using the relation β = B(complex)/B(free ion). The values
of β lie in the range of 0.87‐0.75. Parameters B and C are
linear combinations of certain coulomb's and exchange
4
4
[6A1g → Eg, A1g(4G)] (10B + 5C), 28568 cm‐1 [6A1g
→
4Eg(4G)] (17B = 5C) and 29846 cm‐1 [6A1g → T1g(4P)]
transitions, suggesting of octahedral geometry.[37] Mn(II)
polymer complex in the present study show magnetic
4

EL‐SONBATI ET AL.
9 of 23
FIGURE 6 2D plot of interaction between HL (form A) and
receptors (a) crystal structure of Escherichia coli (3t88) and (b)
crystal structure of Staphylococcus aureus (3q8u)
FIGURE 5 2D plot of interaction between start and receptors (a)
crystal structure of Escherichia coli (3t88) and (b) crystal structure of
Staphylococcus aureus (3q8u)
inter‐electronic repulsion parameters B and C. By using
values of the Racah parameters B and C values for the
parameters B (680 cm‐1) and C (3401 cm‐1), values for the
parameters F2 (1166) and F4 (97) have been calculated.
The electron‐electron repulsion in the complex is less than
integral and are generally treated as empirical parameters
obtained from the spectra of the free ion. Slater Condon‐
Shortly parameters F2 and F4 are related to the Racah

10 of 23
EL‐SONBATI ET AL.
the free ion, resulting the increased distance between elec-
trons and thus, an effective increase in the size of the
orbital will take place. On increasing delocalization, the
value of β (0.87) decreases. This is why the calculated value
of the β in the present complex is less than one. This indi-
cates that the complex under study has appreciable cova-
lent character in metal ligand (M‐L) bond.
3.5 | X‐ray diffraction analysis
The X‐ray diffraction (XRD) patterns powder forms of
monomer and polymer complexes (1, 3 and 4) are shown
in Figure 10. The XRD patterns of polymer complexes (1,
3 and 4) show a broad peak in the range of 2θo = 20‐ 27o
indicating a completely amorphous structures while
monomer shows many diffraction peaks which indicate
the polycrystalline phase.[41]
3.6 | Thermal analysis of HL and its
polymer complexes
The thermal properties of HL and its metal polymer
complexes were characterized on the basis of thermogravi-
metric analysis (TGA) method in the temperature range
30–800 °C (Figure 11). The effect of temperature and the per-
centage of loss of mass are listed in Table 3. The TGA curve
of the HL show three composition steps, the first step is at
temperature range 50–163 °C and it suits loss of CH3 (found
4.84%; calc. 4.89%) and the second stage at the temperature
range 163‐426 °C suits to loss of C3H2N2SO (found 37.12%;
calc. 37.13%). The final stage at the temperature range 426‐
800 °C suits to loss of C9H8NO3 (found 58.04%; calc. 57.98%).
Complex {[Co(HL)(OCOCH3)2(H2O)2] 2H2O}n (1)
decomposed at three stages, the first stage at temperature
range 25–76 °C which related to evaluation of 2H2O mole-
cules (found 6.71%; calc. 6.48%).[42] The second stage in the
range 76‐456 °C correlated with the loss of 2H2O +
2CH3COO + C9H9N2O3S (found 67.60%; calc. 66.02%).
The third stage in the range 456‐726 °C, the complex loss
C3H4N (found 9.60 %; calc. 9.71%) and one carbon atom
and CoO remained as a final product (found 16.09 %; calc.
15.64%).
Complex {[Ni(HL)(OCOCH3)2(H2O)2] 3H2O}n (2)
decomposed at three stages, the first stage at temperature
range 30‐93 °C which correspond to loss 3H2O molecules
(found 9.61%; calc. 9.41%). The second stage in the range
93‐428 °C which related to loss a part of 2H2O + 2CH3COO
+ C8H8NO (found 49.13%; calc. 50.20%), the third stage in
the range 428‐800 °C the complex loss C4H5N2O2S (found
25.60%; calc. 25.28%) and leaving one carbon atom and NiO
as a final product (found 15.66%; calc. 15.11%).
FIGURE 7 2D plot of interaction between HL (form B) and
receptors (a) crystal structure of Escherichia coli (3t88) and (b)
crystal structure of Staphylococcus aureus (3q8u)
Complex {[Mn(HL)(OCOCH3)2(H2O)2] 2H2O}n (3)
decomposed at three stages, the first stage at

EL‐SONBATI ET AL.
11 of 23
FIGURE 8 IR spectrum of monomer
TABLE 2 IR spectra (cm‐1) of the monomer and its polymer complexes
υ(OH) υ(SO2) υ(SO2) υ(H2O) Isoxazole Ring
enolic (asym) (sym.) (coord) str.
Compound
HL
υ(NH)
υ(M‐O) υ(M‐N)
3283,3260, 3178
‐
3060
3080
3108
3112
1337
1311
1307
1330
1313
1156
1162
1132
1162
1164
‐
835,794
835,764
835,796
‐
1467,1417, 1369
‐
‐
440
445
480
435
{[Co(HL)(OCOCH3)2(H2O)2] 2H2O}n (1)
{[Ni(HL)(OCOCH3)2(H2O)2] 3H2O}n (2)
{[Mn(HL)(OCOCH3)2(H2O)2] 2H2O}n (3)
{[Cd(HL)2(OCOCH3)2] 3H2O}n (4)
‐
‐
‐
‐
1475,1412 592
1481,1411 594
1470,1396 569
1473,1404 586
temperature range 30‐95 °C which correspond to loss
2H2O molecules (found 5.85%; calc. 6.52%) and the sec-
ond stage in the range 95‐455 °C which related to loss
a part of 2H2O + 2CH3COO (found 27.19%; calc.
27.90%). The third stage in the range 455‐780 °C the
complex loss C8H13N3SO3 (found 42.51%; calc. 41.84%)
and five carbon atoms and MnO remained as residue
(found 25.45%; calc. 23.93%).
3.7 | Kinetic studies
The kinetic parameters such as the thermal activation
energy of decomposition (Ea), enthalpy (ΔH*), entropy
(ΔS*) and Gibbs free energy change of the decomposition
(ΔG*) are evaluated graphically by employing the Coast‐
Redfern and Horowitz‐Metzger methods.[43,44]
Complex
{[Cd(HL)2(OCOCH3)2]
3H2O}n
(4)
3.7.1 | Coast‐Redfern equation
decomposed at four stages, the first stage at temperature
range 35‐112 °C related to evaluation of 3H2O molecules
(found 6.13%; calc. 6.01%). The second stage in the range
112‐240 °C related to evaluation of CH3COO (found
6.59%; calc. 6.57%) and the third stage in the range 240‐
470 °C which correlated with elimination a part of
CH3COO + C6H10N4S2O5 (found 37.34%; calc. 37.96%).
The fourth stage, which was the final stage, in the range
470‐800 °C loss C20H16N2O2 (found 35.04%; calc. 35.17%)
and leaving CdO as a final product (found 14.90%; calc.
14.29%).
The Coast‐Redfern equation, which is a typical integral
method, can represent as:
ꢆ
ꢇ
dx
A
Ea
a
0
T2
T1
∫
¼
∫
exp −
dt
(5)
n
ð1−αÞ
ϕ
RT
For convenience of integration, the lower limit T1 usu-
ally taken as zero. This equation on integration gives:
ꢈ
ꢉ
ꢈ
ꢉ
lnð1−αÞ
Ea
¼ − þ ln
RT
AR
In −
(6)
T2
φEa

12 of 23
EL‐SONBATI ET AL.
FIGURE 9 1H‐NMR spectrum of (a) monomer and (b) monomer with D2O
ꢈ
ꢆ
ꢇꢉ
Ah
ΔS* ¼ 2:303 log
R
(7)
A plot of left‐hand side (LHS) against 1/T was drawn
(Figure 12). Ea is the energy of activation and calculated
kBTs
from the slop. The entropy of activation calculated by
using the equation:
where kB is the Boltzmann constant, h is the Plank's con-
stant and Ts is the TG peak temperature.

EL‐SONBATI ET AL.
13 of 23
FIGURE 11 TGA curves of HL and polymer complexes
3.7.2 | Horowitz‐Metzger equation
The Horowitz‐Metzger equation is an illustrative of the
approximation methods. These authors derived the rela-
tion:
"
#
1−n
1−ð1−αÞ
1−n
Eaθ
2:303RT2s
log
¼
;
for n≠1
(8)
when n = 1, the LHS of equation 8 would be log[‐log(1‐α)]
(Figure 13). For a first order kinetic process, the Horowitz‐
Metzger equation may write in the form:
ꢈ
ꢆ
ꢇꢉ
Wα
Eaθ
2:303RT2s
log log
¼
− log2:303
(9)
Wγ
where θ = T‐Ts, wγ = wα‐ w, wα = mass loss at the comple-
tion reaction; w = mass loss up to time t. The plot of log
[log (wα/wγ)] vs. θ was drawn and found to be linear from
the slope of which Ea was calculated. The pre‐exponential
factor, A, calculated from equation:
ꢈ
ꢆ
ꢇꢉ
Ea
Ea=RT2s ¼ A= φ exp −
(10)
RTs
The entropy of activation, ΔS*, is calculated from
equation 7. The enthalpy activation, ΔH*, and Gibbs free
energy, ΔG*, calculated from:
ΔH* ¼ Ea−RT
(11)
(12)
ΔG* ¼ ΔH*−T ΔS*
The calculated values of Ea, A, ΔS*, ΔH* and ΔG* for the
decomposition steps for HL monomer and its polymer
complexes (1‐4) are summarized in Table 4. The kinetic
data obtained from the two methods are comparable and
FIGURE 10 X‐ray diffraction patterns of powder forms for a)
monomer, b) polymer complex (1), c) polymer complex (3) and d)
polymer complex (4)

14 of 23
EL‐SONBATI ET AL.
TABLE 3 TGA analyses of monomer and polymer complexes
Compounda
TG range (°C)
Mass loss Found (Calcd.) %
Assignment
HL
50–163
163‐426
426‐800
4.84 (4.89)
37.12 (37.13)
58.04 (57.98)
CH3
C3H2N2SO
C9H8NO3
(1)
(2)
(3)
(4)
25–76
76‐456
456‐726
< 726
6.71 (6.48)
67.60 (66.02)
9.60 (9.71)
2H2O
2H2O + 2CH3COO + C9H9N2O3S
C3H4N
CoO + C
16.09 (15.64)
30‐93
93‐428
428‐800
< 800
9.61 (9.41)
49.13 (50.20)
25.60 (25.28)
15.66 (15.11)
3H2O
2H2O + 2CH3COO + C8H8NO
C4H5N2O2S
NiO + C
30‐95
95‐455
455‐780
< 780
5.85 (6.52)
27.19 (27.90)
42.51 (41.84)
25.45 (23.93)
2H2O
2H2O + 2CH3COO
C8H13N3SO3
MnO + 5C
35‐112
112‐240
240‐470
470‐800
< 800
6.13 (6.01)
6.59 (6.57)
37.34 (37.96)
35.04 (35.17)
14.90 (14.29)
3H2O
CH3COO
CH3COO + C6H10N4S2O5
C20H16N2O2
CdO
aNumbers as given in Table 2.
can be considered in good agreement with each other.[24,45]
From the values of the thermal activation energy of decom-
position (Ea) of HL monomer and its polymer complexes
(1‐4), it was found that the Ea value for the complex (1)
is higher compared to the other complexes.
Escherichia coli and Klebsiella pneumoniae (Table 5). It
was found that Cd(II) polymer complex (4) has more anti-
bacterial activity than the penicillin against Klebsiella
pneumoniae. The activity of the Cd(II) polymer complex
(4) may be due the fact that:
The entropy is found to be negative values in the HL
and its polymer complexes (1‐4) which indicates more
ordered activated complex than the reactants or the
reaction is slow.[38] The positive value of ΔG* for HL
and its polymer complexes (1‐4) is non‐spontaneous
processes.
1. Cd(II) polymer complex (4) has corresponding metal
chloride salt in 1:2 (metal: monomer) molar ratio
(Section 2).
2. the Cd(II) polymer complex (4) has more than one
[46]
unit of sulfonamide.
The antifungal activity results of the HL and its poly-
mer complexes were investigated against Aspergillus
niger, Fusarium oxysporum and the yeast Candida
albicans and listed in Table 6. It was found that the mono-
mer and M(II) complexes polymer have neither antifun-
gal nor anticandidal activities.
3.8 | Antimicrobial activity studies
Antimicrobial activities of sulphadrugs and metal com-
plexes may be enhanced by the presence of oxygen, nitro-
gen, and sulfur atoms which have chelating properties.[46]
Antibacterial and antifungal activities of monomer and
metal polymer complexes were tested against three local
Gram positive bacteria (Bacillus cereus, Staphylococcus
aureus and Enterococcus faecalis), three local Gram nega-
tive bacteria (Escherichia coli, Klebsiella pneumoniae and
Pseudomonas aeruginosa) and three local fungi (Aspergil-
lus niger, Fusarium oxysporum and the yeast Candida
albicans) and the results were recorded in Tables 5 and
6. All the monomer and polymer complexes have no anti-
bacterial activity against Gram positive bacteria and Gram
negative bacteria except Cd(II) polymer complex (4) has
antibacterial activity against Staphylococcus aureus,
3.9 | DNA binding activity study
DNA binding usually exhibits hypochromic as a conse-
quence of the intercalation mode, which involves a strong
stacking interaction between an aromatic chromophore
and the base pairs of DNA. The intrinsic binding constant
to CT‐DNA by monitoring the absorption intensity of the
charge transfer spectral bands near 262 nm for the HL and
259, 256, 259 and 259 nm for polymer complexes (1‐4),
respectively, was determined.

EL‐SONBATI ET AL.
15 of 23
FIGURE 12 Coats–Redfern (CR) of HL and its polymer complexes
DNA interaction study by UV–Visible spectroscopy
electronic absorption spectra was initially used to
examine the interaction between ligand and CT‐DNA.
After interaction with increasing amount of DNA, the
absorption spectra of HL monomer and its polymer
complexes (1‐4) display clear hypochromism with slight
red shift (~1‐2 nm). These interactions result in the
observed hypochromic [28,38]. The intrinsic binding
constant (Kb) values obtained from the absorption
spectral technique (Figure 14) were calculated as 2.19
×105 M‐1 for HL and 8.62 ×105 M‐1, 1.16 ×106 M‐1, 6.51
×105 M‐1 and 2.91 ×105 M‐1 for polymer complexes
(1‐4), respectively. From these results we noted that the
highest value of Kb is belong complex (2) and these
indicated that the Ni(II) is highly binding with CT‐
DNA and these due to the lower ionic radiusas shown in
Figure 15.
3.10 | Corrosion inhibition of C38 steel
using HL
3.10.1 | Potentiodynamic polarization
measurement
Polarization tests were done in order to gain knowledge
concerning the kinetics of the cathodic and anodic reac-
tions. Figure 16 shows the polarization behavior of C38
steel electrode in 2 M HCl without and with unlike dose
of HL. Figure 16 gives that both the cathodic and
anodic reactions are impressive by the putting of

16 of 23
EL‐SONBATI ET AL.
TABLE 4 Thermodynamic parameters for monomer and polymer complexes
Temp.
range
Compounda (°C)
Parameter
Correlation coefficient (r)
Method Ea (kJ mol−1
)
ΔS* (J mol‐1 K‐1) ΔH* (kJ mol−1
)
ΔG* (kJ mol−1
)
HL
(1)
(2)
(3)
(4)
224‐456 CR
42.8
50.5
‐2.34E+02
‐2.18E+02
37.7
45.4
181
179
0.99967
0.99894
HM
249‐448 CR
80.7
92.4
‐1.73E+02
‐1.51E+02
75.5
87.1
185
183
0.99745
0.99805
HM
120‐251 CR
51.3
57.7
‐1.86E+02
‐1.66E+02
47.5
53.9
133
130
0.99941
0.9984
HM
211‐447 CR
54.2
63.9
‐2.14E+02
‐1.92E+02
49.2
58.9
178
174
0.99849
0.99848
HM
280‐485 CR
63.2
73
‐2.06E+02
‐1.87E+02
57.7
67.6
193
191
0.99907
0.99823
HM
aNumbers as given in Table 2.
FIGURE 13 Horowitz–Metzger (HM) of HL and its polymer complexes

EL‐SONBATI ET AL.
17 of 23
TABLE 5 Antibacterial activity data of monomer and polymer complexes. The results were recorded as the average diameter of inhibition
zone (mm) standard deviation
Gram positive bacteria
Gram negative bacteria
Conc.
(μg/ml)
Bacillus
cereus
Staphylococcus
aureus
Enterococcus
faecalis
Escherichia
coli
Klebsiella
pneumoniae
Pseudomonas
aeruginosa
Compounda
HL
50
100
150
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
0.3
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
0
(1)
50
100
150
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
(2)
50
100
150
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
(3)
50
100
150
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
(4)
50
100
150
‐ve
‐ve
‐ve
0.2
0.2
0.2
0
0
0
‐ve
‐ve
‐ve
0.4
0.8
0.8
0
0
0
0.4 0*
0.55 0.04*
0.60 0*
‐ve
‐ve
‐ve
Penicillin
50
100
150
1
3
3
0.14
0.28
0.14
2
2
2
0
0.14
0
1.46 0.03
1.86 0.03
1
3
3
0
0
0
‐ve
‐ve
‐ve
0.87 0.033
1.06 0.033
1.4 0.058
2.2
0
aNumbers as given in Table 2.
*Indicate significant different value from that of penicillin.
TABLE 6 Antifungal activity data of monomer and polymer complexes. The results were recorded as the average diameter of inhibition
zone (mm) standard deviation
Compounda
Conc. (μg/ml)
Aspergillus niger
Fusarium oxysporum
Candida albicans
HL
50
100
150
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
(1)
(2)
50
100
150
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
50
100
150
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
(3)
50
100
150
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
(4)
50
100
150
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
‐ve
Miconazole
50
100
150
1
3
4
0
0.14
0
2
3
3
0
0
0
1.1
1.3
1.7 0.058
0
0
aNumbers as given in Table 2.

18 of 23
EL‐SONBATI ET AL.
FIGURE 14 Plot of [DNA]/(εa − εf) as function of DNA concentration as determined from the absorption spectral data of HL and its
polymer complexes
%IEp ¼ ½ iocorr‐icorrÞ=iocorrꢀx 100
(13)
investigated HL and the protection efficiency improve as
the inhibitor dose rise, but the cathodic reaction is more
inhibited, i.e the addition HL lower the anodic liquefac-
tion of alloy and also prevent the cathodic reactions.
Therefore, HL is play as mixed kind inhibitor.
The data in Table 7 given corrosion current density
lower obviously after the appending of inhibitors in
2 molar acid and % IE rise with higher the dose of inhib-
itor. The Ecorr with inhibitor was improve with no definite
trend, lead to that this inhibitor play as mixed–kind inhib-
itors. %IEp was record by utilized equation:
where icorr and io
are the inhibited and lack
corr
inhibited current corrosion densities, respectively.
It is evident from Table 7 that the (βa) and (βc) Tafel lines
equal upon unchanged appending of organic derivatives,
improvement to a nearly parallel set of anodic lines,
and almost parallel cathodic curves record too. The
inhibitor adsorbed lower the surface area for corrosion with-
out impressive of the mechanism corrosion of alloy in acidic
solution.[47]

EL‐SONBATI ET AL.
19 of 23
Figure 17 given Nyquist (a) and Bode (b) curves given at
open‐circuit potential both in lack and attendance of ris-
ing dose of investigated HL. The improvement in the size
of the capacitive loop with the appending of HL gives that
a gradually barrier forms on the alloy surface. The rise in
the size of capacitive loop Figure 17(a) enhances, at a
fixed inhibitor dose.
The Nyquist digrames do not given best semicircles as
theory expected of EIS. The change from ideal semicircle
due to the dispersion of frequency as well as to the
inhomogeneity's of the surface. The Cdl (double layer
capacitance) is measured from equation 14:
Cdl ¼ Yoωn‐1= sin ½n ðπ=2Þꢀ
(14)
FIGURE 15 The relation between ionic radius of metal
complexes vs. intrinsic binding constants (Kb)
where Yo = CPE magnitude, ω = 2πfmax, fmax = the imag-
inary frequency at which the component of the imped-
ance is maximal.
After test the shape of the Nyquist curves, the corrosion
process was controlled mainly charged‐transfer.[47] From
the EIS data (Table 8), we noted that the data of Rct rise
with rising the dose of the inhibitor and this lead to an rise
in % IE. Data of capacitance double layer are also lower to
the maximum inhibitor extent. The lower in CPE/Cdl data
from a lower in local dielectric constant and/or an improve
in the double layer thickness, given that HL protect the
C38 steel from corrosion. The main advantages of EIS are
to follow the corrosion behavior of the metal with constant
time. The inhibition efficiency was calculated from the
charge transfer resistance data from equation 15:[38]
ꢂ
ꢀ
ꢁꢃ
%IEEIS ¼ 1– R°ct=Rct x 100
(15)
FIGURE 16 Tafel polarization diagrams for the corrosion of C38
steel in 2 M hydrochloric acid attendance and lack of unlike dose of
HL at 30 1 °C
where Ro and Rct are the charge‐transfer resistance
ct
values without and with inhibitor, consecutively.
3.10.2 | EIS test
3.10.3 | EFM method
EIS is a powerful method in the research of corrosion.
Mechanistic information, properties of surface and kinet-
ics of electrode can be given from impedance plots.[38]
The advantages of EFM test give it an ideal for online mon-
itoring of corrosion. The causality factors are higher
strength data of the EFM which act as an internal check
TABLE 7 Concentrations parameters effect of HL for C38 steel in 2 M hydrochloric acid attendances and lack of unlike dose of inhibitor at
30 1 °C
icorr × 10 (μA cm‐2)
βa × 10 (mV dec‐1)
βc × 10 (mV dec‐1)
θ
% IE
‐5
‐3
‐3
Conc., M.
‐Ecorr (mV vs. SCE)
Blank
455
2.56
2.09
2.05
2.01
1.84
1.83
1.06
82.6
84.3
94.0
71.2
42.5
83.5
112.7
202.5
145.3
141.6
197.2
107.2
127.1
151.4
‐‐‐‐‐
‐‐‐‐‐
1x10‐6
3x10‐6
5 x10‐6
7x10‐6
9x10‐6
11x10‐6
475
474
448
434
474
494
0.1835
0.1992
0.2148
0.2812
0.2851
0.5859
18.35
19.92
21.48
28.12
28.51
58.59

20 of 23
EL‐SONBATI ET AL.
βa). The EFM parameters were given in Table 9 show that,
the appended of HL at a given dose to the acidic solution
lower the current corrosion density, lead to these com-
pounds protect the corrosion of alloy through adsorption.
The best data of CF‐2 and CF‐3 in Table 9 are similar to
their theoretical data of 2.0 and 3.0, respectively lead to
the calculated value are quality good.
The % IEEFM improves by raising the inhibitor dose
and was measured from equation 16:
ꢂ ꢀ
ꢁꢃ
%IEEFM ¼ 1‐ icorr=iº
x 100
(16)
corr
where iocorr and icorr are current corrosion densities with-
out and with inhibitor, consecutively.
3.10.4 | Mechanism of corrosion
protection
From the electrochemical experiments the % IE relies on
dose, metal nature, surface conditions and the type of
inhibitor adsorption on C38 steel.
The results of corrosion value attendance of this
inhibitor:
i. The lower of rate and current of corrosion with rise
in dose of the inhibitor.
ii. The change in Tafel lines to maximum regions of
potential.
iii. The lower in % IE corrosion with improve tempera-
ture lead to desorption of the adsorbed inhibitor mol-
ecules obtain.
FIGURE 17 EIS Nyquist (a) and Bode diagrams (b) for the
corrosion of C38 steel in 2 M hydrochloric acid attendance and
lack of unlike dose of HL at 30 1 °C
on verified data and of the EFM test. The CF‐2 and CF‐3
are record from the frequency spectrum of the responses
current. The data of EFM in acidic solution with and with-
out various doses of HL given in Figure 18. The two higher
peaks, with amplitude of about 200 μA, are the given to the
40 and 100 mHz (2 and 5 Hz) excitation frequencies. The
EFM experimental data were utilized two unlike models:
iv. The %IE relies on charge density and their equip-
ment of adsorption centers in the molecule.
It was observed that the type of adsorption relies on
the affinity of the C38 steel towards the clouds of π‐elec-
tron of the ring. Metals such as iron, which have a higher
attract towards aromatic moieties, were obtain to adsorb
benzene rings in orientation flat. HL exhibits excellent
inhibition power due to its larger molecular size that
may facilitate better surface coverage.
diffusion complete control of the cathodic reaction and
[48,49]
the ‘activation’ model.
The higher peaks were uti-
lized to measure the (icorr), (CF‐2 and CF‐3) and (βc and
TABLE 8 Kinetic parameters given by EIS test for C38 steel in 2 M HCl attendance and lack of unlike dose of HL at 30 1 °C
RS × 10 (Ω cm2)
Yο × 10 (μΩ−1sn)
n
Rct (Ω cm2)
Cdl × 10 (μFcm−2
)
θ
%IE
‐3
‐6
‐3
× 10
‐5
Conc., M.
Blank
9.131
9.120
13.28
10.51
11.35
9.49
158.4
158.3
169.5
167.0
157.7
148.8
156.8
758.5
758.7
743.9
758.1
769.4
807.5
755.6
1.018
9.956
8.942
8.940
8.570
1.099
1.082
1.035
‐‐‐‐‐
‐‐‐‐‐‐
1x10‐6
3x10‐6
5 x10‐6
7x10‐6
9x10‐6
11x10‐6
1.048
1.258
1.538
1.557
1.892
1.985
0.0286
0.1907
0.3381
0.3461
0.4619
0.4871
2.86
19.07
33.81
34.61
46.19
48.71
11.00

EL‐SONBATI ET AL.
21 of 23
1E-3
1E-4
1E-5
1E-6
1E-7
1E-8
1E-4
1E-5
1E-6
1E-7
1E-8
1x10-6 M
Blank
0.0
0.5
1.0
1.5
0.0
0.5
1.0
1.5
Freq, Hz
Freq, Hz
1E-4
1E-5
1E-6
1E-7
1E-8
1E-9
1E-4
1E-5
1E-6
1E-7
1E-8
1E-9
-6
3x10-6 M
5x10 M
0.0
0.5
1.0
1.5
0.0
0.5
1.0
1.5
Freq, Hz
Freq, Hz
1E-4
1E-5
1E-6
1E-7
1E-8
1E-5
1E-6
1E-7
1E-8
7x10-6 M
9x10-6 M
0.0
0.5
1.0
1.5
0.0
0.5
1.0
1.5
Freq, Hz
Freq, Hz
-6
1E-5
1E-6
1E-7
1E-8
11x10 M
0.0
0.5
1.0
1.5
Freq, Hz
FIGURE 18 EFM spectra for the corrosion of C38 steel in 2 M hydrochloric acid attendance and lack of unlike dose of HL at 30 1 °C
TABLE 9 Electrochemical kinetic parameters obtained by EFM technique for C38 steel in 2 M HCl without and with various concentra-
tions of HL at 30 1 °C
‐3
‐3
Conc., M.
icorr (μA cm‐2)
βa × 10 (mV dec‐1)
βc × 10 (mV dec‐1)
CF‐2
CF‐3
θ
%IE
Blank
101.20
107.9
327.3
297.5
190.0
188.8
225.7
147.2
85.4
96.5
1.93
3.12
‐‐‐‐‐
‐‐‐‐‐‐
1x10‐6
3x10‐6
5 x10‐6
7x10‐6
9x10‐6
11x10‐6
57.24
38.77
36.68
35.36
33.62
32.86
1.98
1.89
1.93
2.07
1.78
1.95
3.45
3.23
3.27
3.06
3.04
3.14
0.4343
0.6168
0.6375
0.6005
0.6077
0.6752
43.43
61.68
63.75
60.05
60.77
67.52
140.9
105.6
92.6
104.4
75.6
study and thermodynamics parameters of N‐[4‐(5‐
methyl‐isoxazol‐3‐ylsulfamoyl)‐phenyl]‐acrylamide and
its M(II) complexes. Monomer and its M(II) complexes
are screened for their antimicrobial activity against bacte-
ria and fungi species. It was found that Cd(II) complex
4 | CONCLUSIONS
The molecular structures, elemental analyses, IR spectra,
spectral studies, molar conductance, magnetic measure-
ments, mass spectra, X‐ray diffraction analysis, thermal

22 of 23
EL‐SONBATI ET AL.
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has more antibacterial activity than the penicillin against
Klebsiella pneumoniae. From the values of the thermal
activation energy for decomposition (Ea) of monomer
and its polymer complexes, it was found that the Ea value
for the complex (1) is higher compared to the other com-
plexes. HL is good corrosion inhibitor for C38 steel in 2 M
HCl solution. The effectiveness of this inhibitor depends
on its structure. The variation in inhibitive efficiency
depends on the type and the nature of the substituent
present in the inhibitor molecule. Double layer capaci-
tances decrease with respect to blank solution when the
inhibitor added. This fact may explained by adsorption
of the inhibitor molecule on the C38 steel surface. EFM
can be utilized as a fast and nondestructive tests for calcu-
lation of corrosion without prior information of Tafel
lines
[13] A. Z. El‐Sonbati, M. A. Diab, M. S. El‐Shehawy, M. M. Makpel,
Spectrochim. Acta A 2010, 75, 394.
[14] A. Z. El‐Sonbati, A. A. Al‐Sarawy, M. Moqbel, Spectrochim.
Acta A 2009, 74, 463.
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J. Mol. Struct. 2011, 990, 26.
[17] A. Z. El‐Sonbati, M. A. Diab, M. M. EL‐Halawany, N. E. Salam,
Spectrochim. Acta A 2010, 77, 755.
[18] A. Z. El‐Sonbati, A. M. Belal, M. A. Diab, M. Z. Balboula,
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ACKNOWLEDGEMENT
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[22] G. Gece, Corro. Sci. 2011, 53, 3873.
The authors would like to thank Prof. Dr. M.I. Abou‐
Dobara, Botany Department, Faculty of Science, Damietta
University, Egypt for his help during testing antimicrobial
activity.
[23] M. I. Abou‐Dobara, A. Z. El‐Sonbati, Sh. M. Morgan, World J.
Microbiol. Biotechnol. 2013, 29, 119.
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ORCID
[25] P. W. Selwood, Magnetic Chemistry, Interscience Pub. Inc., New
York 1956.
A.Z. El‐Sonbati http://orcid.org/0000-0001-7059-966X
M.A. Diab http://orcid.org/0000-0002-9042-1356
Sh.M. Morgan http://orcid.org/0000-0002-8921-4894
[26] H. M. Refaat, H. A. El‐Badway, Sh. M. Morgan, J. Mol. Liq.
2016, 220, 802.
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