Geometrical structures, thermal properties and antimicrobial activity studies of azodye complexes

Article abstract of DOI:10.1016/j.molliq.2016.02.026

A novel series of metal complexes with 4-(2,3-dimethyl-1-phenylpyrazol-5-one azo)-3-aminophenol ligand (HL) are prepared and characterized by elemental analyses, IR, UV-Visible spectra, ¹H NMR spectra, mass spectra, X-ray diffraction analysis,

Full text of DOI:10.1016/j.molliq.2016.02.026

Journal of Molecular Liquids 218 (2016) 16–34
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
Geometrical structures, thermal properties and antimicrobial activity
studies of azodye complexes
a,
a
b
c
b
a
A.Z. El-Sonbati ⁎, A.A. El-Bindary , G.G. Mohamed , Sh.M. Morgan , W.M.I. Hassan , A.K. Elkholy
a
Chemistry Department, Faculty of Science, Damietta University, Damietta, Egypt
Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt
Environmental Monitoring Laboratory, Ministry of Health, Port Said, Egypt
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel series of metal complexes with 4-(2,3-dimethyl-1-phenylpyrazol-5-one azo)-3-aminophenol ligand
Received 10 December 2015
Accepted 9 February 2016
Available online xxxx
1
(HL) are prepared and characterized by elemental analyses, IR, UV–Visible spectra, H NMR spectra, mass spectra,
X-ray diffraction analysis, conductivity measurements and magnetic susceptibility measurements as well as ther-
mal analysis. The IR spectrum revealed that the ligand (HL) coordinates as monobasic tridentate manner with
ONO donor sites of nitrogen atom of azo group ( \\ N_N), oxygen atom of the deprotonated phenolic \\ OH
Keywords:
Metal complexes
1
group and exocyclic carbonyl oxygen atom forming a five/six-membered chelate structures. The H NMR spectra
data indicated that the phenolic proton is also displaced during complexation. From the magnetic and spectral
studies, it was obvious that the geometrical structures of these complexes are octahedral. The molecular struc-
tures of the ligand (HL) and its metal complexes are optimized theoretically and the quantum chemical param-
eters are calculated. The XRD patterns of the ligand (HL) and complex (3) are a mixture of crystalline and
Molecular structures
Quantum chemical parameters
Thermodynamic parameters
Antimicrobial activities
⁎
a
amorphous phases. The activation thermodynamic parameters, such as activation energy (E ), enthalpy (ΔH ),
⁎
⁎
entropy (ΔS ), and Gibbs free energy change of the decomposition (ΔG ) are calculated using Coats–Redfern
and Horowitz–Metzger methods. The ligand (HL) and its metal complexes are screened for their antimicrobial
activity against, four bacteria (two Gram positive, i.e. Bacillus subtilis, Streptococcus pneumoniae, and two Gram
negative, i.e. Escherichia coli and Pseudomonas aeruginosa) and two fungi species (Aspergillus fumigatus and Can-
dida albicans). The obtained data implies that all the complexes have high antimicrobial activities toward
B. subtilis, S. pneumoniae, E. coli and A. fumigatus than the ligand (HL). In addition to that, complexes (1), (3) and
(5) showed antifungal effect against C. albicans.
©
2016 Elsevier B.V. All rights reserved.
1
. Introduction
Many authors reveal an excellent work devoted to the synthesis and
those derived from aniline-based diazo components [9]. Furthermore,
they were proved to have biological activity against bacteria and fungi
organisms [10,11]. Azo derivatives containing antipyrine moiety have
many advantages including color depending effect as an intrinsic prop-
erty leading to better dye ability.
The data from our laboratory [1,12–14] have demonstrated that the
bidentate azodye ligands play a key role in making new complexes with
transition metal ions. However, little is known concerning the constitu-
tion of these complexes, as well as the chemistry involved in their prep-
aration, or the structural and coordination in such complexes. El-
Sonbati et al. [11,15] found that the stability of multiple hydrogen bond-
ed ligands depends not only on the number of hydrogen bonds but also
on the hydrogen bonding pattern.
characterization of azodyes as well as their metal complexes [1–4]. The
variety of coordination modes of azodye of 3-aminophenol and/or
pyrazolone were demonstrated in a number of complexes and their bi-
ological applications as well and potentiometric studies have been of
considerable interest [5–7]. Many attempts were done to prepare sym-
metric/asymmetric polydentate ligands in order to achieve rare coordi-
nation number with divalent metal ions whose importance was mainly
due to their ability to form metal chelates. Due to new interesting appli-
cations found in the field of pesticides and medicine, the metal com-
plexes with bi/tridentate O, N/O, N, O types of alternative structures
had attracted the attention of chemists [8]. Azo compounds are known
to be involved in a number of biological reactions which based on het-
erocyclic amines have higher strength and give brighter dyeing than
This paper describes the characterization of 4-(2,3-dimethyl-1-
phenylpyrazol-5-one azo)-3-aminophenol ligand (HL) and its metal
1
complexes by elemental analyses, IR, H NMR, UV–Vis spectra, X-ray dif-
fractometer, magnetic moment, molar conductance, and thermal analy-
sis. The antimicrobial activity of the ligand (HL) and its metal complexes
are studied and comparison of the antimicrobial activity results of the li-
gand (HL) and its metal complexes with the standard antibacterial and
⁎
Corresponding author.
E-mail address: elsonbatisch@yahoo.com (A.Z. El-Sonbati).
http://dx.doi.org/10.1016/j.molliq.2016.02.026
167-7322/© 2016 Elsevier B.V. All rights reserved.
0

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
17
antifungal drugs was carried out. The molecular structures of the inves-
tigated ligand (HL) and its metal complexes were studied and quantum
chemical parameters were calculated. Moreover, the thermodynamic
parameters are calculated and discussed.
of 0.01 mol sodium nitrite in 20 ml of water was added dropwise. The
formed diazonium chloride was consecutively coupled with an alkaline
solution of 0.01 mol 3-aminophenol, in 10 ml of pyridine. Immediately,
the deep purple precipitate formed was filtered through sintered glass
crucible and washed several times by distilled water. The crude product
was purified by recrystallization from hot ethanol (yield ~68%) then
2
. Experimental
2 5
dried in a vacuum desiccator over anhydrous P O . The structure of
2
.1. Preparation of the ligand (HL)
the formed ligand (HL) was established by elemental analyses, IR and
H NMR spectroscopies.
1
The ligand (HL) was prepared as described previously [5,7] by
coupling an equimolar amount of 1-phenyl-2,3-dimethyl-4-
aminopyrazol-5-one and 3-aminophenol as shown in Fig. 1. In a typical
preparation, 25 ml of distilled water containing 0.01 mol hydrochloric
acid was added to 1-phenyl-2,3-dimethyl-4-aminopyrazol-5-one
2.2. Preparation of complexes
The metal complexes were prepared by the addition of hot solution
(60 °C) of the appropriate metal chloride (0.664 mmol) in absolute eth-
anol (15 ml) to the hot solution (60 °C) of the organic ligand (0.3 g HL)
(
0.01 mol). To the resulting stirred and cooled (0 °C) mixture, a solution
Fig. 1. The formation mechanism and tautomeric structures of the azo ligand (HL).

18
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
Table 1
Elemental analyses data physical properties of HL ligand and its complexes.
Compound
Color (% yield)
M.p. (°C)
Exp. (calcd.)%
C
μ
eff
A
m
(Ω mol−1 cm2)
−1
(B.M.)
H
N
M
HL (C17
H
17
N
5
O
2
)
Reddish brown
265
63.09
5.25
21.65
–
–
–
(
68)
(63.16)
42.78
(42.42)
37.54
(37.61)
37.42
(37.63)
39.60
(5.26)
3.90
(3.74)
3.55
(3.69)
3.90
(3.69)
3.60
(21.67)
14.70
(14.56)
12.92
(12.90)
12.86
(12.91)
13.69
[
[
[
[
[
Cr(L)Cl
2
H
N
2
O] H
2
O (1)
Cr)
] .5H
ClCo)
] 5H
ClNi)
Green
(83)
Black
(94)
Green
(80)
Brown
(70)
Yellowish brown
(75)
N300
N300
N300
N300
N300
10.41
(10.79)
10.64
(10.86)
10.62
(10.82)
12.62
4.2
4.3
3.1
1.8
da
58.0
57.0
34.0
30.0
55.0
(C
17
H
20
5
O
7
Cl
2
Co(L)Cl(H
2
O)
2
2
O (2)
(C
17
H
30
N
5
O
7
Ni(L)Cl(H
2
O)
2
2
O (3)
(C
17
H
30
N
5
O
7
Cu(L)Cl(H
2
O)
2
] 3H
2
O (4)
(C
17
H
26
N
5
O
7
ClCu)
(39.92)
38.45
(38.94)
(3.91)
3. 89
(3.82)
(13.70)
13.74
(13.36)
(12.42)
21.45
Cd(L)Cl(H
2
O)
2
]H
2
O (5)
(C
17
H
22
N
5
O
7
ClCd)
(21.46)
a
d = diamagnetic.
in ethanol and DMF (15 ml). The resulting mixture was heated with stir-
ring to evaporate all the solvents to get a precipitate. The precipitate was
dried and weighed to calculate the percent yield. All the above steps
were repeated for all the selected d-transition metals. The elemental
analyses data and physical properties are listed in Table 1.
Pseudomonas aeruginosa (RCMB 010043)) and two fungal species
(Aspergillus fumigatus (RCMB 02568) and Candida albicans (RCMB
05036)) [16]. Well diameters (6 mm) were made in the media and
the hole was loaded with the compounds. Amphotericin B was taken
as a reference for the antifungal effect, while ampicillin was used as
standard for the evaluation of antibacterial activity against Gram posi-
tive bacteria and gentamicin was used as a standard in assessing the ac-
tivity of the tested compounds against Gram negative bacteria [16]. The
results are expressed as the mean of zone of inhibition in mm ± stan-
dard deviation. Optical densities of antimicrobial were measured after
24 h at 37 °C to bacteria organisms and measured after 48 h at 28 °C
to fungal species. The plates were then incubated at 37 °C or 28 °C for
bacteria and fungi, respectively. The diameters of inhibition zone were
determined after 24 h and 3–5 days for bacteria and fungi, respectively,
taking the consideration of the control.
2
.3. Methodology of antimicrobial
The ligand (HL) and its metal complexes (1–5) of 5 mg/ml concen-
tration were tested for their antibacterial and antifungal activities.
These assays were performed at the Regional Center for Mycology and
Biotechnology, Al-Azhar University, Egypt. The tested compounds
were evaluated against two Gram positive bacteria (Bacillus subtilis
(
RCMB 010067) and Streptococcus pneumoniae (RCMB 010010)),
two Gram negative bacteria (Escherichia coli (RCMB 010052) and
Fig. 2. 1H NMR spectrum of HL ligand.

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
19
2
.4. Measurements
The molecules were built with the Gauss View 3.09 and optimized
using Gaussian 03W program [5,19]. The corresponding geometries
were optimized without any geometry constraints for full geometry op-
timizations. Frequency calculation was executed successfully, and no
imaginary frequency was found, indicating minimal energy structures.
All the compounds and solvents used were purchased from Aldrich
and Sigma and used as received without further purification. Elemental
microanalyses of the separated ligand and solid chelates for C, H, and N
were determined on Automatic Analyzer CHNS Vario ELIII, Germany.
Mass spectra were recorded by the EI technique at 70 eV using MS-
2.5. Methods of calculations
5
988 GS-MS Hewlett-Packard. The IR spectra were recorded as KBr
1
disks using a Perkin-Elmer 1340 spectrophotometer. The H NMR spec-
trum was obtained with a JEOL FX90 Fourier transform spectrometer
The molecular geometry for the tested compound was fully opti-
mized using Density functional theory B3LYP method, where (B3) [20,
21] stands for Becke's three parameter exact exchange-functional com-
bined with gradient-corrected correlation functional of Lee, Yang and
Parr (LYP) [22] by implementing 6–311 + g(d,p) [23] and LANL2DZ
[24,25] as basis sets for the isolated ligand and complex, respectively.
All the calculations were done using the Gaussian 09 software package
[26]. The optimized structures were visualized using Chemcraft version
1.6 package [5] and GaussView version 5.0.9 [27]. As a consequence of
using multiplicity other than singlet, both HOMO and LUMO split into
two levels with different spins namely, “Alpha” (α) and “Beta” (β)
were employed. The energy difference, ΔE is measured as the smallest
difference between LUMO and HOMO having the same spin since
using different spins produce an optically spin forbidden transition
(dark excited state). The binding energy of metal to all moieties in the
complex was calculated by subtracting the total energy of the complex
from the summation of the energies of isolated metal ion and (single
point at the optimized geometry of the complex excluding the metal
ion) using LANL2DZ [24,25] as a basis set.
6
with DMSO-d as the solvent and TMS as an internal reference. X-ray
diffraction analysis of the compounds in powder form was recorded
o
on an X-ray diffractometer in the range of diffraction angle 2θ = 5–
o
6
1
2
0 . This analysis was carried out using CuKα radiation (λ =
.54056 Å). The applied voltage and the tube current are 40 KV and
5 mA, respectively. Ultraviolet–visible (UV–Vis) spectra of the com-
pounds were recorded in Nujol mulls using a Unicom SP 8800 spectro-
photometer. The magnetic moment of the prepared solid complexes
was determined at room temperature using the Gouy's method.
Mercury(II) (tetrathiocyanato)cobalt(II), [Hg{Co(SCN) }], was used for
4
the calibration of the Gouy tubes. Diamagnetic corrections were calcu-
lated from the values given by Selwood [17] and Pascal's constants.
M
Magnetic moments were calculated using the equation, μeff. = 2.84 [Tχ-
coor. 1/2
]
. Thermal studies were computed on Simultaneous Thermal An-
alyzer (STA) 6000 system using thermogravimetric analysis (TGA)
method. Thermal properties of the samples were analyzed in the tem-
perature range from 30 to 1000 °C at the heating rate of 10 °C/min
under dynamic nitrogen atmosphere. ESR measurements of powdered
samples were recorded at room temperature using an X-band spec-
trometer utilizing a 100 kHz magnetic field modulation with diphenyl
picrylhydrazyl (DPPH) as a reference material. The conductance mea-
surement was achieved using Sargent Welch scientific Co., Skokie, IL,
USA. The molecular structure of the investigated compound was opti-
mized initially with the PM3 semiempirical method so as to speed up
the calculations. The resulting optimized structures were fully re-
optimized using ab initio Hartree–Fock (HF) [18] with 6-31G basis set.
3. Results and discussion
3.1. Characterization of the ligand (HL)
Our earlier studies on coordination behavior of azodye derivatives
have shown that this 4-(2,3-dimethyl-1-phenylpyrazol-5-one azo)-3-
aminophenol ligand (HL) (Fig. 1) presents a variety of chelating coordi-
nation behavior, depending on the nature of the metal ion and ligand.
Fig. 3. 1H NMR spectrum of HL ligand with D
O.
2

20
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
Fig. 4. The structure of complexes (1–5).
1
Structure of the ligand was established by UV, IR and H NMR spec-
In agreement with spectrum data, infrared spectrum of HL ligand
gives interesting results and conclusions. The formation of ligand is con-
tral data in addition to the elemental analysis data. A basic structure re-
quirement for tautomerism is the presence of a proton in the molecule.
This requirement is manifested in case of azodye containing an\\OH
group conjugated with the azo group and these dyes exist as a tauto-
meric azo-hydrazo mixture both in solution and in the solid phase
2
firmed by the absence of the NH group of 4-amino-1-phenyl-2,3-
dimethylpyrazolin-5-one and instead a strong new band appeared at
−
1
~1490 cm
corresponding to the azo dye (N_N) group (Fig. 1) [8]
was reported. Additionally, IR spectrum of the HL ligand shows a
[
28]. Thus the ligand under investigation is also capable of exhibiting
broad band assigned to phenolic OH group; υ(OH) [5,7] and a strong
band at 1323 cm assigned to the stretching frequency of the phenolic
−
1
keto-azo (Fig. 1A) and keto-hydrazo tautomerisms (Fig. 1C). It has
been reported that the azo ligand exhibited a strong band in the range
3
above 31,250 cm in ethanol medium [29]. However, the ultraviolet
spectrum of the ligand under investigation gave characteristic band at
~
trum showed an absorption band at 21,930 cm due to π–π* electronic
transition involving the whole conjugate system (five-membered oxy-
gen heterocycles and the azo group) [30].
C\\O bond; υ(C\\O) [11], which affected on complexation with differ-
−
1
−1
7,000–35,200 cm , whereas hydrazones exhibited a strong band
ent degrees. The bands appearing in the region 1480 and 750 cm
−
1
were usual modes of phenyl ring vibration [11], while a band at
−
1
3
2848 cm for CH stretching vibrations of methyl group was found [8].
−
1
35,500 cm (in ethanol) for the azo form. In addition to this, the spec-
Hydrogen bonding represents one of the most versatile interactions
that could be used for molecular recognition. It might be possible to
tune the strength of the hydrogen bond effectively by linking the
hydrogen-bonding site to a reaction center through a conjugated spacer,
−
1
Fig. 5. X-ray diffraction pattern of HL powder form.

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
21
phenol) as shown in Fig. 1. The predominant hydrogen bond is probably
of the first/second type due to the formation of a chelate structure. In-
termolecular hydrogen bonding can form a cyclic dimer through the
(
D) O\\H\\N_N type between OH/N_N of one molecule and OH/
N_N group of another one, (E) O\\H\\O_C type between OH/
C_O(antipyrine) of one molecule and OH/C_O(antipyrine) group of
another one as shown in Fig. 1.
In general, hydrogen bonding involving OH group is a proton donor
and their O atoms are proton acceptors. Both intra and intermolecular
OH…N may form a number of structures in a simultaneous equilibrium.
1
6
H NMR spectrum of the ligand was recorded in DMSO-d at room
temperature which supports the occurrence of the form depicted in
Figs. 2 and 3. In 1H NMR spectrum of the ligand, the _C\\CH
and
\N\\CH protons were observed as singlet at δ 2.47 and 2.60 ppm, re-
3
\
3
spectively. In the aromatic region, a few doublets and in few cases some
overlapping doublets/multiplets are observed in the range of δ
6
.10–7.6 ppm. Another singlet corresponding to one proton for azodye
free ligand is observed in the range of δ ~ 9.59 and 13.03 ppm. This signal
disappeared when a D O exchange experiment was carried out. It can
2
be assigned to OH and/or NH (Fig. 1). Absence of\\CH (~3.85 ppm) pro-
ton signal of the ligand (HL) moiety indicated the existence of the ligand
in the keto-azo form. According to El-Sonbati et al. [8], hydrogen bond-
ing leads to a large deshielding of the protons.
3.2. Structure of the metal complexes
By comparing the infrared spectrum of the ligand and its complexes
the following features for some of the prepared complexes are
observed:
1
. In IR spectra of all complexes, υ(C_O) for the exocyclic carbonyl
−
1
−1
group at 1620 cm
is shifted, with 15–25 cm , to lower wave
numbers. This indicates that the exocyclic carbonyl oxygen is bonded
to metallic ions [31].
2
. The N_N stretching frequency of the azo group is shifted to lower
−
1
frequency by ~25 cm due to the involvement of one of the azo ni-
trogen atoms in coordination with metal ion [8]. This lowering of fre-
quency can be explained by the transfer of electrons from the
nitrogen atom to the metal ion due to coordination.
Fig. 6. X-ray diffraction patterns for complexes (2) and (3).
−1
3. A medium intensity broad band at 2935 cm in the spectrum of li-
gand is due to υ(OH) stretching vibration [5]. The band at 1275 cm−
1
and by altering the charge state of the reaction center in the solution. At
the hydrogen-bonding end, azodye is used as a proton acceptor to form
a hydrogen bond with OH group of ligand.
is characteristic for phenolic υ(C\\O) and it shifted to 1260–
1235 cm in all the complexes, confirms the chelation of phenolic
oxygen to metal ions.
−
1
El-Sonbati et al. [8,13–15] found that three types of hydrogen bonds
may exist in equilibrium with each other. The hydrogen bond in
this case is of intramolecular type either with (B) OH…N_N and
OH…O(antipyrine) or (C) NH…O(antipyrine) and NH…O(amino
4. Based on the above spectral evidences, it is concluded that the ligand
is coordinated to the metal ions as a monobasic tridentate chelating
agents, coordinated to the metal ions via the azodye nitrogen, proton
displacement from the phenolic OH group, i.e. M\\O bonding is
Fig. 7. Mass spectrum of HL ligand.

22
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
Scheme 1. Fragmentation patterns of HL ligand.
415–455 cm− which can be assigned to υ(M\\O) and υ(M\\N) vi-
1
identified and exocyclic carbonyl oxygen atoms forming the more
stable six membered chelate rings (Fig. 4).
. Far infrared spectra of the metal complexes showed several non-
ligand bands of low intensity appearing in the regions 505–595 and
brations, respectively [8].
6. The existence of the broad band in the region 3440–3455 cm in all
the complexes confirms the O\\H stretching of the coordinated and
−
1
5
Fig. 8. Mass spectrum of complex (5).

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
23
Fig. 9. The optimized structure of HL ligand and its metal complexes within numbering of atoms.
hydration water molecules. Also, according to Stefov et al. [32], coor-
dinated water should exhibit frequencies and appear in the spectra of
1H NMR spectrum of cadmium(II) complex recorded in DMSO-d
further substantiates the mode of coordination suggested by IR spectral
studies. In the spectrum of cadmium(II) complex, the proton signal due
6
−
1
metal complexes at 870, 580 and 500 cm
.

24
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
to\\OH disappears and this is a clear indication that phenolic oxygen is
bonded to the metal ion after deprotonation. Signals for N\\CH and
\CH protons do not show any significant changes when compared
to the free ligand. Thus, from IR and H NMR spectral data it is clear
that the ligand is bonded to the metal ion in a keto-azo form.
mass spectrum fragmentation mode of ligand (HL) shows the exact
mass of 323 corresponding to the formula C17 (Fig. 7). The ion
of m/z = 323 undergoes fragmentation to a stable peak at m/z = 122
or 109 or 94 or 76 as shown in Scheme 1. The mass spectrum
fragmentation mode of complex (5) shows the exact mass of 523
3
17 5 2
H N O
\
3
1
corresponding to the formula [Cd(L)Cl(H
m/z = 502 (M-H O) undergoes successive fragmentation to a stable
peak at m/z = 64 that may correspond to C molecule. The loss of
O leads to the fragmentation with m/z = 207. The loss of
N molecule leads to the fragmentation with m/z = 91. The loss of
O molecule leads to the fragmentation with m/z = 224.
2 2 2
O) ] H O (Fig. 8). The ion of
3
.3. X-ray diffraction analysis
2
5 4
H
The X-ray diffraction, XRD, patterns of the ligand (HL) and its metal
C
C
C
11 4 3
N H
complexes (2) and (3) are shown in Figs. 5 and 6. The XRD patterns of
the ligand (HL) and complex (3) have sharp diffraction peaks at around
2
6 7
H
11 5 6
N H
o
o
θ = 10–20 and 2θ = 25–30 , this indicates that HL and complex (3)
are a mixture of crystalline and amorphous phases. While the XRD pat-
3.5. Molecular structures of the ligand and its complexes
tern of complex (2) is amorphous phase.
Theoretical approaches made by Liang and Lipscomb [33] indicated
that the nitrogen atom is more negatively charged than the oxygen
atom in the isolated metal ion and consequently it may account for
the coordination of the nitrogen atom rather than the oxygen atom, to
the metal ion. Moreover, these authors have found that in the presence
of the metal ion, the tridentate binding conformation with both N and
(O,O) atoms coordinated to the metal ions is favored.
3
.4. Mass spectra
The electron impact mass spectra of ligand and its Cd(II) complex
are recorded and investigated at 70 eV of electron energy. It is obvious
that, the molecular ion peaks are in good agreement with their sug-
gested empirical formula as indicated from elemental analysis. The
Fig. 10. HOMO and LUMO molecular orbitals of ligand (HL) and its complexes (1–5).

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
25
Fig. 10 (continued).
The optimized structures of the ligand (HL) and its metal complexes
are presented in Fig. 9. Selected geometric parameters such as bond
lengths and bond angles of HL ligand and its metal complexes are tabu-
lated in Tables S1–S7 in the supplementary. The HOMO and LUMO
states of the HL ligand and its metal complexes are shown in Fig. 10.
Quantum chemical parameters of the HL ligand and its metal complexes
are obtained from calculations such as energies of the highest occupied
molecular orbital (EHOMO) and the lowest unoccupied molecular orbital
total energy difference between the complex and its fragments can be
used to express the binding energy with acceptable accuracy. The bind-
ing energies of the trivalent Cr(III) (complex (1)) are more than all diva-
lent metals, which is expected due to more charged metals which create
stronger bonds. Furthermore, the divalent metal complexes showed
binding energies in the ascending order complex (5) b complex
(2) b complex (3) b complex (4).
(
ELUMO) as listed in Tables 2 and 3. The total dipole moment in Debye
(
D) and Total energy (T.E.) in atomic units (a.u.) for all the complexes
3.6. Electronic spectra and magnetic moments
is shown in Table 3. Higher dipole moment usually signifies a higher
possibility to dissolve in polar solvents. Complex (4) showed the highest
dipole moment, on the other hand, complex (1) possesses the lowest di-
pole moment. The energies of the highest occupied molecular orbital
The electronic absorption spectra of metal complexes can be classi-
fied into three types of spectra depending on the nature of the electronic
transitions involved. These types are: (i) spectra associated with elec-
tronic transitions within the molecular orbitals of the ligand molecules
(L–L spectra), (ii) spectra associated with the metal influenced by
the presence of the ligand and these spectra are generally referred to
as d-d spectra or crystal field spectra, (iii) spectra involving electronic
transition from an orbital lying on the ligand to an orbital lying on the
metal or vice versa. Such charge transfer processes are termed ligand
to metal (LMCT) charge transfer or metal to ligand (MLCT) charge
transfer.
(
HOMO), lowest unoccupied molecular orbital (LUMO) with different
symmetries α, β and their energy difference, ΔE in a.u. are tabulated
in Table 3. Since, the energy difference, ΔE is inversely proportional to
the reactivity of the complex, the reactivity of the studied complexes
follows the ascending order complex (1) b complex (4) b complex
(3) b complex (5) b complex (2). The total energy usually is basis set
as well as method dependent that usually indicated that their absolute
values for energies are almost meaningless. On the other hand, the

26
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
Fig. 10 (continued).
In this part, the important role played by magnetic and electronic
spectra in determining the geometrical structures of the above investi-
gated metal chelates will be elucidated.
The reflectance spectrum of the Cu(II) chelate consists of a low in-
tensity shoulder band centered at 16,849 cm . The 2
−1
E
and 2
T
g
2g
9
states of the octahedral Cu(II) ion (d ) split under the influence of
The diffused reflectance spectrum of the Cr(III) complex showed
the tetragonal distortion and the distortion can be such as to cause
the three transitions B1g → B2g and B1g → E to remain unresolved
g
−
1
2
2
2
2
three bands at 16,949, 17,857 and 21,030 cm
assignable to
2g(F) → T2g(F), A2g(F) → T2g and A2g(F) → T2g(P) spin allowed
d-d transitions [34]. The magnetic moment value is found to be
.2 B.M. for Cr(III) complex, which indicates the presence of Cr(III) com-
4
4
4
4
4
4
A
in the spectra [39]. It is concluded that, all three transitions lie within
the single broad envelope centered at the same range previously
mentioned. This assignment is in agreement with the general obser-
vation that Cu(II) d–d transitions are normally close in energy [40].
The magnetic moment of 1.8 falls within the range normally observed
for octahedral Cu(II) complex [41]. A moderately intense peak ob-
4
plex in octahedral structure. The Ni(II) complex reported herein is high
spin with a room temperature magnetic moment value of 3.10 B.M.;
which is in the normal range observed for octahedral Ni(II) complexes
−
1
(
μ
eff = 2.9–3.3 B.M.) [35]. This indicates that the complex of Ni(II) is
served in the range 37,383 cm is due to ligand–metal charge trans-
six coordinate and probably octahedral [36]. Its electronic spectrum, in
addition to show the π–π* and n–π* bands of the free ligand, display
three bands, in the solid reflectance spectrum at:
fer transition [42]. The electronic spectrum of the Co(II) complex
−
1
gives band at 21,505 cm
refers to the charge transfer band. The
4
1g(F) → 4
bands observed are assigned to the transitions
T
T
2g(F) at
−
1
and 4 1g(F) → 4
−1
1
7,346 cm
T A2g(F) at 18,165 cm , suggesting that
ν1 : 16; 407 cm−
1
:
3
A2gðFÞ→ T2gðFÞ:
3
there is an octahedral geometry around Co(II) ion [35,43,44]. From
the position of the bands, the Co(II) chelates is octahedral with large-
ly covalent bonds between the organic ligand and the metal ion [37].
The magnetic susceptibility measurements lie in the 4.3 B.M. range
ν2: 17; 421 cm− : A2g → T1gðFÞ:
1 3
3
(
normal range for octahedral Co(II) complexes is 4.3–5.2 B.M.), is an
ν3: 19; 083 cm− : A2g→ T1gðPÞ:
1 3
3
indication of octahedral geometry [45]. The complex of Cd(II) is dia-
magnetic. In analogy with those described for Cd(II) complexes con-
taining N-O donor Schiff bases [42] and according to the empirical
formula of this complex, an octahedral geometry was proposed for
the Cd(II) complex.
The position of these bands confirms the octahedral configuration of
the complex [37,38]. The spectrum showed also a band at 37,174 cm
which may be attributed to (LMCT).
−
1

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
27
Fig. 10 (continued).
3
.7. ESR spectrum of Cu(II) complex
the unpaired electron is localized in dx2-y2 orbital [47] of the Cu(II)
ion and the spectrum features are characteristics of axial symmetry
[48]. The unpaired electron in this 3d9 case assigned to 3dx2 − y2 or-
bital, and the overlapping of this antibonding orbital with the ligand
2 s and 2p σ orbital is often determined by the use of the following
equation:
The spin-Hamiltonian parameters of copper complexes are listed
in Table 4. The spin-Hamiltonian parameters, electronic absorption
spectrum and magnetic moment values for the copper(II) complex
suggested elongated distorted octahedral Cu(II) complex. Kivelson
and Neiman [46] have reported the g|| b 2.3 for covalent character
of the metal–ligand bond and N2.3 for ionic character. Applying this
criterion the covalent character of the metal–ligand bond in the com-
plex under study can be predicted. Further, the values are consistent
with the mixed Cu\\N, and Cu\\O bonded copper complexes. The
2
α ¼ A =Po þ ðg −2:0023Þ þ Koðg −2:0023Þ þ 0:04:
ll
ll
⊥
2
where α give an approximate indication of the strength of the inter-
o
action between the metal and the ligand. P is the dipolar contribu-
trend g|| N g
⊥
N g
e
(2.0023) observed for this complex showed that
tion to the hyperfine splitting value.
Table 2
The calculated quantum chemical properties for ligand tautomers (A–C).
Compound
E
HOMO
E
LUMO
ΔE (a.u.)
μ (D)
T.E (a.u)
χ (a.u.)
η
(a.u.)
σ
(a.u.)
Pi
(a.u.)
S
Ω
(a.u.)
ΔNmax
(a.u.)
−
1
−1
(
a.u.)
(a.u.)
(a.u.)
(A)
(B)
(C)
−0.1973
−0.2182
−0.2044
−0.0689
−0.1113
−0.0907
0.1284
0.1069
0.1137
4.529
4.110
6.394
−1082.473
−1083.205
−1082.493
0.1331
0.1648
0.1475
0.0642
0.0535
0.0568
15.576
18.702
17.593
−0.1331
−0.1648
−0.1475
7.788
9.351
8.797
0.1379
0.2539
0.1915
2.073
3.082
2.596
Table 3
The dipole moment, total energy (T.E.), EHOMO, ELUMO, energy difference (ΔE) in a.u., binding energy (B.E.), absolute electronegativities (χ), chemical potentials (Pi), absolute hardness (η),
absolute softness (σ), global electrophilicity (Ω), global softness (S) and additional electronic charge (ΔNmax) in a.u. of complexes (1–5).
E
HOMO
E
LUMO
(a.u.)
Complexa μ (D)
B.E.
a.u.)
η
(a.u.)
σ
(a.u.)
Pi
(a.u.)
S
Ω
(a.u.)
ΔNmax
(a.u.)
T.E (a.u.)
ΔE (a.u.)
χ (a.u.)
−1
−1
(a.u.)
(
(a.u.)
α
β
α
β
1
2
3
4
5
7.930 −1335.555 −0.30606 −0.30866 −0.19333 −0.20420 0.10446 −2.345 0.2564 0.0522 19.146
8.892 −1394.419 −0.14284 −0.20361 −0.05179 −0.12976 0.07385 −1.316 0.1667 0.0369 27.082
9.983 −1418.694 −0.18426 −0.18541 −0.09119 −0.09078 0.09307 −1.387 0.1381 0.0473 21.135
10.485 −1445.491 −0.20216 −0.20066 −0.08868 −0.10152 0.09914 −1.397 0.1511 0.0496 20.174
9.326 −1297.389 −0.14674 −0.20420 −0.05343 −0.11494 0.08926 −1.205 0.1596 0.0446 22.407
−0.2564
9.573
0.1282 4.909
0.0833 4.514
0.0690 2.919
0.0756 3.048
0.0798 3.575
−0.1667 13.541
−0.1381 10.568
−0.1511 10.087
−0.1596 11.203
a
Numbers as given in Table 1.

28
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
2
Table 4
The α value (Table 4) for complex (4) indicated considerable cova-
The spin Hamilton parameters of Cu(II) complex.
lency in the bonding between the Cu(II) ion and the ligand, comparable
to that obtained by El-Sonbati et al. [51,52]. The super-exchange split-
ting constant A|| was obtained semi-empirically, according to Pryce [53].
The small A|| value can be attributed to the decreased dipolar inter-
action. This reduction may be due to the orientation of the 4-(2,3-
dimethyl-1-phenylpyrazol-5-one azo)-3-aminophenol groups in a
manner so as to increase the separation between successive planes.
The g||/A|| values showed that the complex has an octahedral geometry
[8], and this is further confirmed by the Symons plot [54].
Compounda
g
g
g
G
α
2
A
ll
b
ll
l
av
4
2.221
Numbers as given in Table 1.
2.047
2.11
5.5
0.54
94.63
a
b
−4
−1
A values in 10 cm
.
In addition there is an exchange coupling interaction between two
copper centers explained by Hathaway et al. [49,50] expression G =
|| − 2)/(g − 2). According to Hathaway, if the value of G is greater
(
g
⊥
than four, the exchange interaction is negligible interaction as indicated
in solid complex. The calculated G value is given in Table 4 and found to
3.8. Thermal analysis
⊥
be 5.5. It is clear that gav N g N 2.04, characteristic of axial symmetry,
Thermal properties of ligand and its metal complexes were charac-
suggesting that the principal axes of this structure are parallel to each
other and that all the sites are equivalent in every orientation in the stat-
terized on the basis of thermogravimetric analysis in the temperature
range 30–1000 °C as shown in Fig. 11. The temperature intervals and
the percentage of loss of masses are listed in Table 5. The ligand showed
two decomposition steps. The first stage occurs in the temperature
2
ic magnetic field. Approximate metal ligand σ -bond coefficient (α ),
which is defined as the fraction of unpaired electron density located
on the copper ion, for the present complex fall in the range indicating
appreciable in-plane covalency, neglecting the π-bonding with the
help of the optical absorption data in the solid state using the relation.
range 50–265 °C which is attributed to loss of C
ond stage in the temperature range 265–1000 °C is corresponding to
loss of C12 molecule.
The TG curve of complex (1) showed three decomposition steps, the
first step corresponds to the loss of H O molecule within the tempera-
5 6
H molecule. The sec-
11 5 2
H N O
2
gav: ¼ 2:0023−4 λα =ΔE:
2
ture range of 35–125 °C with found mass loss of 4.12% (calcd 3.74%).
The second step of decomposition occurs within the temperature
range 125–230 °C and corresponds to the loss of H
ecules with found mass loss 23.24% (calcd. 23.91%). The third step cor-
responds to the loss of C12 0.5 fragment within the temperature
2 2 2 2
O, C H and Cl mol-
14 5
H N O
range of 230–1000 °C with found mass loss 50.27% (calcd. 49.08%).
The complex (2) decomposes in two steps within the temperature
range 30–1000 °C. The first step of decomposition within the tempera-
ture range 30–45 °C can assigned to the loss of water molecules of hy-
dration with a mass loss 12.44% (calcd. 13.27%). The second step can
be attributed to loss of 3H
2 15 5
O, HCl and C14H N O fragments with a
mass loss of 65.90% (calcd. 66.28%).
The complex (3) decomposes in three steps, the first step of decom-
position within the temperature range 30–67 °C is due to the loss of
5
H
2
O molecules. The second step of decomposition occurs within the
temperature range 67–443 °C and corresponds to the loss of 2H O,
HCl and C11 10O molecules with a mass loss 43.74% (calcd. 42.13%).
The third step corresponds to the loss of C fragment within the
temperature range of 443–1000 °C with found mass loss of 26.37%
2
H
6 5 5
H N
(
calcd. 27.11%).
On the other hand, complex (4) exhibits three decomposition steps.
The first step of decomposition within the temperature range 30–130 °C
Fig. 11. TGA curves of ligand (HL) and its metal complexes (1–5).
Table 5
a
Weight losses percentage of ligand and its metal complexes .
Compound
TG range
°C)
na
Mass loss
Calcd. (exp.) %
Total mass loss
Calcd. (exp.) %
Assignment
Metallic residue
(
HL
50–265
65–1000
35–125
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
20.43 (20.30)
79.57 (79.70)
3.74 (4.12)
100
C
C
H
H
5
H
6
2
(100)
76.73
(77.63)
12
H
11
N
5
O
2
–
1
2
O
0.5Cr
+3C
2 3
O
1
2
25–230
30–1000
23.91 (23.24)
49.08 (50.27)
13.27 (12.44)
66.28 (65.90)
16.60 (16.13)
42.13 (43.74)
27.11 (26.37)
7.04 (7.30)
2
2 2 2
O + C H + Cl
12 14 5 0.5
C H N O
2
3
30–45
5–1000
30–67
79.55
(78.34)
85.84
4H
3H
5H
2H
C H N
6 5 5
2H
3H
C
H
2H
2
2
2
2
O
CoO + 3C
NiO
4
O + HCL + C14
O
O + HCl + C11H O
10
15 5
H N O
6
4
7–443
43–1000
(85.64)
4
5
30–130
84.43
(85.15)
2
O
CuO
1
3
30–390
90–990
29.06 (28.70)
48.33 (49.15)
3.44 (3.69)
2
O + HCl + C
2
H
4
NO
15 11 4
H N
30–129
29–995
68.62
(69.85)
2
O
CdO + 3C
1
65.18 (66.16)
2
O + HCl + C14
H
15
N
5
O
na = number of decomposition steps.
a
Numbers given in Table 1.

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
29
corresponds to the loss of two water molecules of hydration with a mass
loss of 7.30% (calcd. 7.04%). The second step of decomposition within
the temperature range 130–390 °C corresponds to the loss of 3H O,
HCl and C NO fragments with a mass loss of 28.70% (calcd. 29.06%).
The third step corresponds to the loss of C15 fragment within
the temperature range of 390–990 °C with found mass loss of 49.15%
3.9. Kinetic studies
2
The kinetic parameters such as activation energy (E
a
), enthalpy
⁎
⁎
H
2 4
(ΔH ), entropy (ΔS ), and Gibbs free energy change of the decomposi-
⁎
H
11
N
4
tion (ΔG ) are evaluated graphically by employing the Coats–Redfern
[55] and Horowitz–Metzger [56] methods.
(
calcd. 48.15%).
The TG curve of complex (5) exhibits two decomposition steps. The
first step of decomposition occurs within the temperature range 30–
29 °C and corresponds to the loss of water molecule of hydration
with a mass loss of 3.69% (calcd. 3.44%). The second step of decomposi-
tion corresponds to the loss of 2H O, HCl and C14 O fragments with
3.9.1. Coast-Redfern equation
The Coats–Redfern equation, which is a typical integral method, can
represent as:
1
2
15 5
H N
a mass loss 66.16% (calcd. 65.18%). In all complexes the final weight
losses are due to the decomposition of the rest of the ligand and metal
oxides residue.
ꢀ
ꢁ
a
0
dx
ð1−αÞ
A
φ
T2
T1
Ea
RT
∫
¼
∫
exp −
dt:
ð1Þ
n
Fig. 12. Coats–Redfern (CR) of ligand (HL) and its metal complexes (1–5).

30
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
For convenience of integration, the lower limit T
zero. This equation on integration gives:
1
usually taken as
3.9.2. Horowitz–Metzger equation
The Horowitz–Metzger equation is an illustrative of the approxima-
tion methods. These authors derived the relation:
ꢂ
ꢃ
ꢂ
ꢃ
lnð1−αÞ
Ea
RT
AR
φEa
ln −
¼ −
þ ln
:
ð2Þ
"
#
2
1−n
T
1−ð1−αÞ
a
E θ
log
¼
2:303RTs
;
for n ≠ 1
ð4Þ
2
1
−n
a
A plot of left-hand side (LHS) against 1/T was drawn (Fig. 12). E is
−
1
the energy of activation and calculated from the slop and A in (s
)
when n = 1, the LHS of Eq. (4) would be log[−log(1 − α)] (Fig. 13). For
a first order kinetic process, the Horowitz–Metzger equation may write
in the form:
from the intercept value. The entropy of activation calculated by using
the equation:
ꢂ
ꢀ
ꢁꢃ
ꢂ
ꢀ
ꢁꢃ
Ah
kBTs
Wα
Wγ
Eaθ
2:303RTs
ꢀ
ΔS ¼ 2:303 log
R
ð3Þ
log log
¼
− log2:303
ð5Þ
2
where k
the TG peak temperature.
B
is the Boltzmann constant, h is the Plank's constant and T
s
is
where θ = T − T
action; w = mass loss up to time t. The plot of log [log (w
s
, w
γ
= w
α
− w, w
α
= mass loss at the completion re-
/w )] vs. θ was
α
γ
Fig. 13. Horowitz–Metzger (HM) of ligand (HL) and its metal complexes (1–5).

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
31
Table 6
Kinetic parameters of HL ligand and its metal complexes .
⁎
Compound
Decomposition
Method
Parameters
Correlation coefficient
temperature (°C)
(r)
E
(
a
A
ΔSa
ΔHa
ΔGa
kJ mol−1)
(s−1)
(J mol K−1
)
−1
(kJ mol−1)
(kJ mol−1)
HL
1
216–650
153–446
50–555
CR
HM
10.2
24.2
1.23E−03
5.94E−02
−3.08E+02
−2.76E+02
4.35
18.3
222
213
0.99818
0.99276
CR
HM
10.5
13.0
2.79E−03
1.22E−02
−2.99E+02
−2.87E+02
5.71
8.24
177
173
0.99005
0.98848
2
CR
HM
11.5
23.2
3.25E−03
1.80E−01
−2.98E+02
−2.65E+02
6.69
18.4
178
171
0.9939
0.99675
3
66–573
CR
HM
11.0
22.5
3.06E−03
1.24E−01
−2.99E+02
−2.68E+02
6.06
17.6
183
176
0.99624
0.98791
4
109–607
185–530
CR
HM
10.6
21.8
2.66E−03
7.01E−02
−3.00E+02
−2.73E+02
5.31
16.6
195
189
0.99688
0.9956
5
CR
HM
28.4
39.4
1.48E−01
3.68E+00
−2.67E+02
−2.40E+02
23.2
34.2
192
186
0.9973
0.99749
a
Numbers given in Table 1.
Table 7
a
Antibacterial activity data of HL ligand and its metal complexes (1–5). The results are recorded as the diameter of inhibition zone (mm) ± SD.
Gram positive bacteria
Gram negative bacteria
Compound
Bacillus subtilis
Streptococcus pneumoniae
Pseudomonas aeruginosa
Escherichia coli
(RCMB 010067)
(RCMB 010010)
(RCMB 010043)
(RCMB 010052)
HL
1
2
3
4
5
16.4 ± 0.63
27.2 ± 1.2
21.3 ± 0.58
22.3 ± 0.58
20.4 ± 0.58
24.2 ± 1.5
32.4 ± 0.3
−ve
14.3 ± 2.1
23.4 ± 0.34
19.3 ± 2.1
20.6 ± 1.2
17.3 ± 1.2
22.1 ± 0.58
23.8 ± 0.2
−ve
−ve
−ve
−ve
−ve
−ve
−ve
−ve
17.3 ± 0.1
13.8 ± 1.5
22.7 ± 5.8
18.2 ± 0.19
19.8 ± 0.72
16.8 ± 0.72
20.1 ± 2.1
−ve
Ampicillin
Gentamicin
19.9 ± 0.3
a
Numbers given in Table 1.
⁎
The entropy of activation, ΔS , is calculated from Eq. (3). The enthal-
py activation, ΔH , and Gibbs free energy, ΔG , calculated from:
drawn and found to be linear from the slope of which E
The pre-exponential factor, A, calculated from equation:
a
was calculated.
⁎
⁎
ꢀ
Ea
RT2s
A
ΔH ¼ Ea−RT
ð7Þ
ð8Þ
¼
ꢂ
ꢀ
ꢁꢃ :
ð6Þ
Ea
RTs
φ exp −
ꢀ
ꢀ
ꢀ
ΔG ¼ ΔH −TΔS :
Fig. 14. Antibacterial activity data of HL ligand and its complexes (1–5) against Bacillus subtilis.

32
A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
Fig. 15. Antibacterial activity data of HL ligand and its complexes (1–5) against Escherichia coli.
⁎
⁎
⁎
The calculated values of E
a
, A, ΔS , ΔH and ΔG for the decomposi-
The antibacterial and antifungal activities of the ligand (HL) and its
metal complexes (1–5) are tested against four bacteria and two fungi
organisms. The used organisms in the present investigation included
Gram positive bacteria (B. subtilis and S. pneumoniae), Gram negative
bacteria (E. coli and P. aeruginosa) and fungi (A. fumigatus and
C. albicans). The results of the antibacterial activity of the ligand (HL)
and its metal complexes (1–5) are recorded in Table 7. It was found
that all the compounds have antibacterial activity against Gram positive
bacteria; namely B. subtilis (Fig. 14) and S. pneumonia, when compared
with gentamicin. The ligand (HL) and its metal complexes (1–5) were
found to have no antibacterial activity against Gram negative bacteri-
um; namely, P. aeruginosa, but have antibacterial activity against
E. coli, when compared with ampicillin as shown in Fig. 15.
The antifungal activity of HL and its complexes (1–5) were reported
and they were found to have antifungal activity against A. fumigatus as
shown in Fig. 16 and Table 8. The HL ligand, complexes (2) and (4)
have no antifungal activity against C. albicans, while the complexes
(1), (3) and (5) have antifungal activity against C. albicans and inhibition
zone is 19.6, 15.7 and 17.1 mm, respectively.
tion steps for ligand (HL) and its metal complexes (1–5) are summa-
rized in Table 6. The kinetic data obtained from the two methods are
comparable and can be considered in good agreement with each other.
3
.10. Antimicrobial activity
The azodyes of pyrazolone and/or 3-aminophenol are an essential
structural requirement for biological activity [8]. Several azodye
compounds and their metal complexes have been reported to possess
remarkable antibacterial and antifungal activities [1,4,13]. The antimi-
crobial action of azodye compounds may be significantly enhanced by
the presence of azo group which have chelating properties. These prop-
erties may be used in metal transport across the bacterial membranes or
to attach to the bacterial cells at a specific site from which it can inter-
fere with their growth [8]. Despite the importance of studying the anti-
bacterial and antifungal activities of 4-(2,3-dimethyl-1-phenylpyrazol-
5
-one azo)-3-aminophenol in biological applications, to the best of our
knowledge no studies on the antimicrobial activities have been done.
Fig. 16. Antifungal activity data of HL ligand and its complexes (1–5) against Aspergillus fumigatus.

A.Z. El-Sonbati et al. / Journal of Molecular Liquids 218 (2016) 16–34
33
Table 8
References
a
Antifungal activity data of HL ligand and its metal complexes (1–5). The results are re-
corded as the diameter of inhibition zone (mm) ± SD.
[
1] M.A. Diab, A.Z. El-Sonbati, A.A. El-Bindary, G.G. Mohamed, Sh.M. Morgan, Res. Chem.
Intermed. 41 (2015) 9029–9066.
[2] N.A. El-Ghamaz, A.Z. El-Sonbati, M.A. Diab, A.A. El-Bindary, G.G. Mohamed, Sh.M.
Aspergillus fumigatus
RCMB 02568)
Candida albicans
(RCMB 05036)
Compound
(
Morgan, Spectrochim. Acta A 147 (2015) 200–211.
[
[
[
[
3] A.Z. El-Sonbati, G.G. Mohamed, A.A. El-Bindary, W.M.I. Hassan, M.A. Diab, Sh.M.
Morgan, A.K. Elkholy, J. Mol. Liq. 212 (2015) 487–502.
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HL
1
2
3
4
5
15.2 ± 1.5
25.2 ± 0.72
17.6 ± 0.63
21.3 ± 1.2
15.7 ± 2.1
23.2 ± 1.2
23.7 ± 0.1
−ve
19.6 ± 0.63
−ve
15.7 ± 1.5
−ve
17.1 ± 0.63
25.4 ± 0.1
Liq. 209 (2015) 625–634.
6] A.A. El-Bindary, A.Z. El-Sonbati, M.A. Diab, Sh.M. Morgan, J. Mol. Liq. 201 (2015)
Amphotericin B
36–42.
a
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Numbers given in Table 1.
[
[
8] A.Z. El-Sonbati, M.A. Diab, A.A. El-Bindary, A.M. Eldesoky, Sh.M. Morgan,
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On comparing the antimicrobial activity of the ligand and its
complexes with the standard drugs (ampicillin, gentamicin and
amphotericin B), the following results are obtained:
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Acta A 140 (2015) 111–131.
13] A.Z. El-Sonbati, M.A. Diab, A.A. El-Bindary, Sh.M. Morgan, Spectrochim. Acta A 127
(
[
[
[
(
•
•
All complexes have high antimicrobial activities than the ligand (HL).
Complex (1) has the highest antimicrobial activities (except against
P. aeruginosa) than the other metal complexes.
(
2014) 310–328.
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6
•
•
•
Complexes (1) and (5) have high effect than gentamicin; as standard
drug against E. coli.
Complex (1) has high effect than amphotericin B; as standard drug
against Aspergillus fumigatus.
The antimicrobial activity of the compounds against Gram positive
bacteria (B. subtilis and S. pneumoniae), Gram negative bacteria
[
(
[
[
[
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(Escherichia coli) and fungus (A. fumigatus) follows the order complex
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4
. Conclusion
—
(
The structures of the ligand and its metal complexes were confirmed
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1
by the elemental analyses, IR, H NMR, mass spectra, molar conduc-
tance, magnetic, ESR, UV- vis and thermal analysis. Therefore, from
the IR spectra, it was found that the ligand (HL) acts as monobasic
-
tridentate through the (\\N_N), enolic (C\\O) and oxygen keto moi-
ety groups forming a five/six-membered structures. Octahedral geo-
metric structures are suggested for all the complexes. The thermal
properties of the ligand and its complexes (1–5) were investigated by
thermogravimetry analysis (TG) and the calculated values of E
a
, A,
ΔS , ΔH and ΔG for the decomposition steps for ligand (HL) and its
metal complexes (1–5) are discussed. The trend g|| N g N g (2.0023)
⁎
⁎
⁎
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