Co(II), Cd(II), Hg(II) and U(VI)O2 complexes of o-hydroxyacetophenone[N-(3-hydroxy-2-naphthoyl)] hydrazone: Physicochemical study, thermal studies and antimicrobial activity

Article abstract of DOI:10.1016/j.saa.2012.05.086

The o-Hydroxy acetophenone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H ₂o-HAHNH) has been prepared and its structure is confirmed by elemental analysis, IR, ¹H NMR and ¹³C NMR spectroscopy. It has been used to produce diverse complexes with Co(II), Cd(II), Hg(II) and U(VI)O₂ ions. The isolated complexes have been investigated by elemental analysis, magnetic measurements, molar conductivity, thermal (TG, DTG) and spectral (¹H NMR, ¹³C NMR, IR, UV-visible, MS) studies. Infrared spectra suggested H₂o-HAHNH acts as a bidentate and/or tridentate ligand. The electronic spectrum of [Co(Ho-HAHNH)₂] complex as well as its magnetic moments suggesting octahedral geometry around Co(II) center. The TG analyses suggest high stability for most complexes followed by thermal decomposition in different steps. Moreover, the kinetic and thermodynamic parameters (Ea, A, ΔH, ΔS and ΔG) for the different decomposition steps of the [Co(Ho-HAHNH)₂] and [Cd(Ho-HAHNH)₂] complexes were calculated using the Coats-Redfern and Horowitz-Metzger methods. Moreover, the antibacterial and antifungal activities of the isolated compounds were studied using a wide spectrum of bacterial and fungal strains.

Full text of DOI:10.1016/j.saa.2012.05.086

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 683–694
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Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
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Co(II), Cd(II), Hg(II) and U(VI)O2 complexes
of o-hydroxyacetophenone[N-(3-hydroxy-2-naphthoyl)] hydrazone:
Physicochemical study, thermal studies and antimicrobial activity
a
R.R. Zaky a, T.A. Yousef b, , K.M. Ibrahim
⇑
a Department of Chemistry, Faculty of Science, Mansoura University, Mansoura, Egypt
b Department of Toxic and Narcotic Drug, Forensic Medicine, Mansoura Laboratory, Medicolegal Organization, Ministry of Justice, Egypt
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
Effect of ligand and its metal complexes toward (A) Aspergillus sp., (B) Stemphylium sp. and (C) Tricho-
derma sp.
"
Synthesis of o-hydroxy
acetophenone [N-(3-hydroxy-
2-naphthoyl)] hydrazone.
Synthesis and characterization
Co(II), Cd(II), Hg(II) and U(VI)O2
complexes with hydrazone.
"
100
90
80
70
60
"
"
Kinetic parameters (Ea, A,
and G) have been calculated.
Molecular modeling of the free
DH, DS
D
50
0.5 mg/ml
1 mg/ml
1.5 mg/ml
40
30
20
ligand and its complexes has been
calculated.
Antibacterial and antifungal studies
showing good results.
10
0
"
a r t i c l e i n f o
a b s t r a c t
Article history:
The o-Hydroxy acetophenone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H2o-HAHNH) has been prepared
and its structure is confirmed by elemental analysis, IR, 1H NMR and 13C NMR spectroscopy. It has been
used to produce diverse complexes with Co(II), Cd(II), Hg(II) and U(VI)O2 ions. The isolated complexes
have been investigated by elemental analysis, magnetic measurements, molar conductivity, thermal
(TG, DTG) and spectral (1H NMR, 13C NMR, IR, UV–visible, MS) studies. Infrared spectra suggested
H2o-HAHNH acts as a bidentate and/or tridentate ligand. The electronic spectrum of [Co(Ho-HAHNH)2]
complex as well as its magnetic moments suggesting octahedral geometry around Co(II) center. The
TG analyses suggest high stability for most complexes followed by thermal decomposition in different
Received 28 March 2012
Received in revised form 4 May 2012
Accepted 17 May 2012
Available online 4 July 2012
Keywords:
Hydrazone complexes
1H and 13C NMR
steps. Moreover, the kinetic and thermodynamic parameters (Ea, A,
D D D
H⁄, S⁄ and G⁄) for the different
Thermal analysis
decomposition steps of the [Co(Ho-HAHNH)2] and [Cd(Ho-HAHNH)2] complexes were calculated using
the Coats–Redfern and Horowitz–Metzger methods. Moreover, the antibacterial and antifungal activities
of the isolated compounds were studied using a wide spectrum of bacterial and fungal strains.
Ó 2012 Elsevier B.V. All rights reserved.
Antibacterial and antifungal activity
Introduction
Schiff bases hydrazone derivatives and their metal complexes
have been studied for their interesting and important properties,
e.g., antibacterial [1,2], antifungal [3]. Schiff bases hydrazone
derivatives are versatile ligands and they offer the possibility of
different modes of coordination towards transition metal ions.
⇑
Corresponding author at: Department of Chemistry, Faculty of Science, Manso-
ura University, Mansoura, Egypt. Tel.: +20 1222247712.
E-mail address: drroka78@yahoo.com (T.A. Yousef).
1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.05.086

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R.R. Zaky et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 683–694
They also employ as extracting agents in spectrophotometric
determination of some ions [4] and spectrophotometric determi-
nation of some species in pharmaceutical formulations [5], as well
as uses in catalytic processes [6,7] and wastewater treatment [8].
We have recently published some transition metal complexes of
hydrazones derived from 3-hydroxy naphthoic acid hydrazide
[9–11]. In continuation of our previous work on hydrazones [1,2],
the present work aims to synthesize and characterize complexes
of o-hydroxyacetophenone [N-(3-hydroxy-2-naphthoyl)] hydra-
zone (H2o-HAHNH) with Co(II), Cd(II), Hg(II) and U(VI)O2 ions.
The possible modes of chelations, the geometry and the nature of
bonding of the complexes are discussed based on various spectro-
scopic methods (1H NMR, 13C NMR, IR, UV–visible, MS). In addition,
the kinetics and thermodynamic parameters of the decomposition
steps for Co(II) and Cd(II) complexes have been studied employing
Coats–Redfern and Horowitz–Metzger methods. The antibacterial
and antifungal activities of the ligand and its metal complexes have
also been examined.
complexes were determined by preparing 10ꢀ3 M solutions of the
complexes in DMSO at room temperature and measured on a YSI
Model 32 conductivity bridge. Thermogravimetric analysis was
performed using an automatic recording thermobalance type
(DuPont 951 Instrument) Thermal Analyzer between room tem-
perature to 800 °C. Magnetic moment values were evaluated at
room temperature (25 1 °C) using a Johnson Matthey magnetic
susceptibility balance using Hg[Co(SCN)4] as calibrant. The elec-
tronic spectrum of Co(II) complex was recorded in DMSO solution
on an Unicam UV2–UV–visible spectrometer, in the range 200–
900 nm. Infrared spectra of the ligand and its metal complexes
were recorded on Mattson 5000 FTIR spectrophotometer, in the
range 4000–500 cmꢀ1 in KBr disk. Mass spectra were recorded on
a Mattson 5000 FTIR spectrophotometer. 1H and 13C NMR spectra
of the ligand and Cd(II), Hg(II) and U(VI)O2 complexes were
recorded in DMSO on an EM-390 (200 MHz) spectrometer.
Molecular modeling
An attempt to gain better insight on the molecular structure of
the ligand and its complexes, geometric optimization and confor-
mational analysis has been performed using PM3 [13] forcefield
as implemented in hyperchem 8 [14]. The low lying obtained from
MM+ was then optimized at PM3 using the Polak–Ribiere algo-
rithm in RHF-SCF, set to terminate at an RMS gradient of
Experiment
Material
All manipulations were performed under aerobic conditions. All
metal salts and other reagents used were pure (Fluka, Aldrich or
Merck).
0.01 kcal molꢀ1
.
Biological activity
Preparation of o-Hydroxy acetophenone [N-(3-hydroxy-2-naphthoyl)]
hydrazone (H2o-HAHNH, C19H16O3N2)
Antifungal activity
Antifungal activity, based on the determined growth inhibition
rates of the mycelia of strain (Aspergillus sp., Trichoderma sp. and
Stemphylium sp.) in Potato Dextrose Broth medium (PDB) were
determined. These species were isolated from the infected organs
of the host plants on potato dextrose agar (potato 250 g + dextrose
20 g + agar 20 g) medium. The cultures of the fungi were purified
by single spore isolation technique. The solution in different con-
centrations 0.5, 1 and 1.5 mg/ml of each compound in DMSO were
prepared for testing against spore germination. A drop of the solu-
tion of each concentration was kept separately on glass slides. The
conidia, fungal reproducing spores (approximately 200) lifted with
the help of an inoculating needle, were mixed in every drop of each
compound separately. Each treatment was replicated thrice and a
parallel DMSO solvent control set was run concurrently on sepa-
rate glass slides. All the slides were incubated in humid chambers
at 25 2 °C for 24 h. Each slide was observed under the microscope
for spore germination and percent germination was finally calcu-
lated. A zone of inhibition of growth was taken as an indication
of antifungal activity. The results were also compared with a stan-
dard antifungal drug Miconazole at the same concentrations.
H2o-HAHNH (Scheme 1) was prepared by heating a mixture of
3-hydroxy naphthoic acid hydrazide (0.01 mol; 2.02 g) and
o-hydroxy acetophenone (0.01 mol; 1.36 g) under reflux in abso-
lute ethanol for 2 h. On heating, pale yellow crystals were formed,
filtered off, washed with absolute ethanol and diethyl ether, and
recrystallized from EtOH (M.p.: 290 °C; yield 90%). The purity of
the compound was checked by TLC.
Synthesis of metal complexes
The metal complexes were synthesized by taking 50 ml solu-
tions of each Co(II), Cd(II), Hg(II) and U(VI)O2 acetate (10 mmol)
in distilled water or absolute ethanol and 50 ml hot absolute etha-
nol solution of the ligand H2o-HAHNH (10 mmol, 3.20 g) in a
round-bottom flask. After refluxing the reactants for 1–3 h and
cooling to room temperature, the complexes precipitated and were
filtered in a glass crucible. The products were washed several times
with water, ethanol and finally with diethyl ether and the pure
complexes thus obtained were dried in a desiccator over anhy-
drous CaCl2. The isolated complexes are powder-like, stable in
the normal laboratory atmosphere, and soluble in DMF or DMSO.
The characterization of these complexes was based on the physical
and spectroscopic techniques.
Antibacterial activity
Chemical compounds were individually tested against a panel
of gram positive Clostridium sp. and negative Escherichia coli bacte-
rial pathogens. Each of the compounds was dissolved in DMSO and
solutions of the concentration 2 mg/ml and 1 mg/ml were pre-
pared separately. Paper discs of Whatman filter paper were pre-
pared with standard size (5 cm) were cut and sterilized in an
autoclave. The paper discs soaked in the desired concentration of
the complex solutions were placed aseptically in the petridishes
containing nutrient agar media (agar 20 g + beef extract 3 g + pep-
tone 5 g) seeded with Clostridium sp. and E. coli bacteria separately.
The petridishes were incubated at 37 °C and the inhibition zones
were recorded after 24 h of incubation. Each treatment was repli-
cated nine times. The antibacterial activity of a common standard
antibiotic ampicillin was also recorded using the same procedure
Analyses of the complexes
Elemental analyses
The complexes were analyzed for metal content gravimetrically
by literature procedures [12] after decomposing the organic matter
with a mixture of HNO3 and HCl and evaporating from the residue
to dryness with concentrated H2SO4.
Physico-chemical measurements
Elemental analyses (C and H) were performed on a Perkin–
Elmer 2400 Series II Analyzer. The molar conductance of the

R.R. Zaky et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 683–694
685
O
H
NH2
O
C
HN
C
CH3
o-hydroxy acetophenone
O
H
Reflux in absolute ethanol
for 2 h
O
3-hydroxy naphthoic acid hydrazide
O
H
N
HN
C
CH3
C
O
H
O
o-hydroxyacetophenone[N-(3-hydroxy-2-naphthoyl)] hydrazone
M(OAc)2
Reflux (1-3) h
H2O
O
AcO
O
O
N
M
M
AcO
N
N
O
O
H2O
[Co(Ho-HAHNH)2],
[Cd(Ho-HAHNH)2]
[Hg(H2o-HAHNH)(OAc)2(H2O)2],
[UO2(H2o-HAHNH)(OAc)2(H2O)2]
Scheme 1. The outline of the synthesis of ligand and its complexes.
as above at the same concentrations and solvent. The % Activity In-
dex for the complex was calculated by the formula as under:
recorded as the lowest concentrations of the substance that had
no visible turbidity. Control experiments with DMSO and uninocu-
lated media were run parallel to the test compounds under
the same conditions. All the compounds were more effective at
1.0 and 2.0 mg/ml concentrations. Consequently, all the com-
pounds were screened at these concentrations against both the
bacteria.
Zone of inhibition by test compoundðdiametreÞ
%Activity Index¼
Zone of inihibition by standardðdiametreÞ
ꢁ100
Minimal inhibitory concentration (MIC) measurement
The MIC was determined using the disc diffusion technique by
preparing discs containing 0.1–1.0 mg/ml of each compound
against both the bacteria and applying the protocol. The twofold
dilutions of the solution were prepared. The microorganism sus-
pensions at 10 CFU/ml (colony forming unit/ml) concentration
were inoculated to the corresponding wells. The plates were incu-
bated at 36 °C for 24 for the bacteria. At the end of the incubation
period, the minimal inhibitory concentrations (MIC) values were
Results and discussion
The color, melting points and elemental analyses of the ligand
and isolated complexes are listed in Table 1. The isolated solid
complexes are stable in the air and easily soluble in DMF and
DMSO only. All complexes decompose on heating at >300 °C. The
molar conductance values, in DMSO, are 3–7 Ohmꢀ1cm2 molꢀ1
indicating that all complexes are non-electrolytes.

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R.R. Zaky et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 683–694
The force constant obtained for uranyl complex was then substi-
IR spectral studies
tuted into the relation given by Jones [23] to give an estimate of
the (U–O) bond length in Å.
The infrared spectrum of H2o-HAHNH displays five bands at
1647, 1618, 3125, 3240 and 3419 cmꢀ1 assigned to
m
m(C@O) [15],
RUꢀO ¼ 1:08ðFUꢀOÞꢀ1=3 þ 1:17
(C@N)hydrazone [16], m(NH) [17], (OH)naphthoic [18] and (OH)phenolic
The calculated FU–O and RU–O values are 6.987 mdynes Åꢀ1 and
1.735 Å, respectively, fall in the normal range for the uranyl
complexes.
[18] vibrations, respectively. The two bands at 1273 and
1365 cmꢀ1 are attributed to d(OH)phenolic and d(OH)naphthoic [19].
The appearance of (OH)naphthoic and (OH)phenolic as a broad band
at lower wavenumbers and the two weak broad bands in the
1900–2080 and 2150–2230 cmꢀ1 regions suggest intramolecular
hydrogen bonding (O–Hꢂ ꢂ ꢂO) [19].
Nuclear magnetic resonance spectral studies
Comparison of the infrared spectrum of the ligand with those of
its metal complexes reveals that H2o-HAHNH (Structure 1) be-
haves as a bidentate and/or tridentate ligand depending on the me-
tal salt and the reaction conditions (Scheme 1, Table 2).
The 1H and 13C NMR spectra of H2o-HAHNH and its Cd(II), Hg(II)
and U(VI)O2 complexes (Scheme 2) were recorded in DMSO. The 1H
NMR spectrum of H2o-HAHNH in DMSO shows three signals at
11.24, 11.32 and 12.19 ppm assignable to the protons of (NH),
(OH)phenolic and (OH)naphthoic respectively (Table 3). The appearance
of the signal attributed to the proton of OH group at a high value
downfield from TMS suggests the presence of intramolecular
hydrogen bonding. The multiplet signals observed in the 6.92–
8.67 ppm region are assigned to the aromatic protons. Also, the
1H NMR spectra of the Hg(II) and U(VI)O2 complexes show the sig-
nals attributed to the (NH), (OH)naphthoic and (OH)phenolic protons
remain more or less at the same positions indicating that these
groups play no part in coordination but in case of 1H NMR spec-
trum of Cd(II) complex there is no signal attributable to (OH)naph-
In [UO2(H2o-HAHNH)(OAc)2(H2O)2] (Structure 2) and [Hg(H2o-
HAHNH)(OAc)2(H2O)2] complexes, H2o-HAHNH acts as a neutral
bidentate ligand coordinating via carbonyl oxygen (C@O) and azo-
methine nitrogen (C@N). This mode of chelation is supported by
the shift of both
ber. The (NH) vibration remains more or less at the same position.
The (OH)naphthoic is shifted to higher wavenumber. Moreover, the
infrared spectra of these complexes showed new bands at (520,
525) and (425, 432) cmꢀ1 assignable to
(M–O) and (M–N),
respectively, [20]. The complexes show two bands at (1382,
1376) and (1571, 1573) cmꢀ1, which can be assigned to
as(O–
m(C@N) and m(C@O) vibrations to lower wavenum-
m
m
m
m
m
proton indicating the deprotonation of this group on
thoic
C–O) and
ms(O–C–O) of the acetate group. The difference (189,
complexation. The most significant features of the 13C NMR spectra
of the Hg(II), U(VI)O2, Cd(II) complex were detected when compar-
ing with the spectrum of the corresponding free ligand. From 13C
NMR spectral data (Table 4), for the Hg(II) and U(VI)O2 complexes,
the signal for C3 and C4 carbon showed an upfield shift on complex-
ation [24] compared with the free ligand. Moreover, the appear-
ance of new signals at (174, 177) and (52, 55) ppm give strong
evidence for the presence of the acetate group. Additionally, the
signal for C3 and C4 carbon of Cd(II) complex showed an upfield
shift while, C6 showed an downfield shift on complexation. The
other ring carbon atoms did not show significant shifts.
197 cmꢀ1) between those two bands indicates the monodentate
bonding for the acetate group [21]. Also, the bands of coordinated
water observed at (824, 844) and (531, 546) cmꢀ1, are assigned to
qr(H2O) and qw(H2O), respectively, [21]. Moreover, strong evidence
for the presence or absence of coordinated water supported by the
thermogram of all complexes.
Also, H2o-HAHNH behaves as a mononegative tridentate ligand
coordinating through the azomethine nitrogen (C@N), carbonyl
oxygen (C@O) and the (OH)naphthoic with the displacement of the
hydrogen atom from the latter group. This behavior is observed
in [Co(Ho-HAHNH)2] (Structure 3) and [Cd(Ho-HAHNH)2] com-
plexes. This mode of chelation is based on the disappearance of
Electronic spectra
the (OH)naphthoic and the shift of both
wavenumbers. In addition, the new bands were observed at (512,
525) and (425, 430) cmꢀ1 tentatively attributed to
(M–O) and
(M–N), respectively [20].
The infrared spectrum of [UO2(H2o-HAHNH)(OAc)2(H2O)2] com-
plex displays two bands at 920 and 870 cmꢀ1 assigned to
3 and m1
vibrations, respectively, of the dioxouranium ion. The m3 value is
m(C@O) and m(C@N) to lower
The electronic spectrum of [Co(Ho-HAHNH)2] complex shows
m
4
two bands at 14,211 and 17,212 cmꢀ1 attributed to T1g(F) ?
m
4A2g(F) and 4T1g(F) ? 4T1g(P) transitions, respectively, in an octahe-
dral configuration [25]. The calculated values of Dq (766), B (766), b
m
(0.76) and m2/m1 (2.15) are in good agreement with those reported
for octahedral Co(II) complexes. In addition, the magnetic moment
(4.98 BM) is consistent with octahedral geometry around the Co(II)
ion.
used to calculate the force constant (F) of m(U@O) by the method
of McGlynn et al. [22].
2
The electronic spectrum of [UO2(H2o-HAHNH)(OAc)2(H2O)2]
ð
m3Þ ¼ ð1307Þ2ðFUꢀOÞ=14:103
complex contains two bands at 21,276 and 25,000 cmꢀ1 may be
Pþ
1
attributed to
!
2pu transition and charge transfer n ? p⁄
,
g
respectively [25].
Table 1
Analytical and physical data of H2o-HAHNH and its metal complexes.
Compound Empirical Formula F.W. Found (Calcd.)
Color
Yield (%)
%Found (Calcd.)
C
H
M
H2o-HAHNH C19H16O3N2 320.112 (320.350)
Yellow
Brown
Yellowish-white
Orange
Yellowish-white
90
85
78
80
75
71.24 (71.27)
65.48 (65.42)
60.54 (60.76)
37.22 (37.10)
40.87 (40.93)
5.08 (5.03)
4.40 (4.33)
4.12 (4.02)
3.49 (3.52)
3.98 (3.88)
[Co(Ho-HAHNH)2] (C1) CoC38H30O6N4 696.841 (697.617)
[Cd(Ho-HAHNH)2] (C2) CdC38H30O6N4 751.968 (751.070)
[UO2(H2o-HAHNH)(OAc)2(H2O)2] (C3) UC23H26O11N2 745.351 (744.411)
[Hg(H2o-HAHNH)(OAc)2(H2O)2] (C4) HgC23H26O9N2 674.751 (675.011)
8.46 (8.54)
14.42 (14.90)
32.07 (31.90)
29.86 (29.70)
In DMSO (ohmꢀ1 cm2 molꢀ1).

R.R. Zaky et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 683–694
687
Structure 1. Molecular modelling of H2o-HAHNH.
Table 2
Most important IR spectral bands of H2o-HAHNH and its metal complexes in cmꢀ1
.
Compound
t
(OH)naphthoic
t
(OH)phenolic
t
(NH)
t
(C@O)
t
(C@N)
t
(C–O)naphthoic
t
(M–O)
t
(M–N)
H2o-HAHNH
3240
3305
3445
-
3419
3425
3430
3445
3430
3125
3189
3186
3223
3221
1647
1630
1629
1633
1631
1618
1596
1598
1597
1598
1219
1246
1233
1234
1236
–
–
[UO2(H2o-HAHNH)(OAc)2(H2O)2]
[Hg(H2o-HAHNH)(OAc)2(H2O)2]
[Co(Ho-HAHNH)2]
520
511
525
512
425
420
430
425
[Cd(Ho-HAHNH)2]
-
Structure 3. Molecular modelling of [Co(Ho-HAHNH)2] complex.
(like C@N, O–H, and C@O). The lower HOMO energy values show
that molecule donating electron ability is the weaker. On contrary,
the higher HOMO energy implies that the molecule is a good elec-
tron donor. LUMO energy presents the ability of a molecule receiv-
ing electron [26].
Structure 2. Molecular modelling of [Hg(H2o-HAHNH)(OAc)2(H2O)2] complex.
Molecular modeling
The atomic numbering scheme and the theoretical geometry
structures for the ligand and some of its metal complexes are cal-
culated. The molecular parameters: total energy, binding energy,
isolated atomic energy, electronic energy, heat of formation, dipole
moment, HOMO and LUMO were calculated and represented in Ta-
ble 5. A comparison between the bond length of the ligand and its
complexes is illustrated. All the active groups taking part in coor-
dination have bonds longer than that already exist in the ligand
Thermal analysis
The TG and DTG curves of [Co(Ho-HAHNH)2] complex show that
it is thermally stable up to 365 °C, above which point partial
decomposition of the complex begins. In the temperature range
365–450 °C, the TG curve is indicative of 26.6% weight loss, which

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R.R. Zaky et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 683–694
Scheme 2. 13C NMR spectra of (A) H2o-HAHNH and (B) [Hg(H2o-HAHNH)(OAc)2(H2O)2] complex.
Table 3
The 1H NMR spectral data of H2o-HAHNH and its diamagnetic complexes.
Compounds
–CH3
Aromatic protons
NH
(OH)phenolic
(OH)naphthoic
H2o-HAHNH
[Cd(Ho-HAHNH)2]
[UO2(H2o-HAHNH)(OAc)2(H2O)2]
[Hg(H2o-HAHNH)(OAc)2(H2O)2]
1.88
1.83
1.91
1.90
6.92–8.67
6.98–8.69
7.11–8.66
7.11–8.72
11.24
11.36
11.27
11.31
11.32
11.45
11.41
11.44
12.19
–
12.21
12.17
ture range 335–460 °C, the TG curve exhibit 24.8% weight loss
which could be ascribed to the elimination of (2C6H5O) moieties.
The second weight loss stage (460–565 °C) is largely due to the full
decomposition of the remaining organic portions (2C13H10N2) of
the two ligand molecules as well as the release of half oxygen
molecule. This stage is accompanied by 58.1% weight loss in the
TG curve. The remaining final fired product is CdO, representing
17.1%.
Table 4
13C NMR Chemical shifts in (ppm) assignments for H2o-HAHNH and its diamagnetic
complexes.
Compound
C1
C2
C3
C4
C5
C6
H2o-HAHNH
[Cd(Ho-HAHNH)2]
[UO2(H2o-HAHNH)(OAc)2(H2O)2]
[Hg(H2o-HAHNH)(OAc)2(H2O)2]
163
164
163
164
120
121
119
120
178
169
171
170
170
163
165
165
120
130
126
127
157
162
158
156
Kinetic data
could be ascribed to the elimination of the two loosely bound
3-hydroxynaphthoyl (2C6H5O) moieties. The second weight loss
stage (450–640 °C) is largely due to the full decomposition of the
remaining organic portions (2C13H10N2) of the two ligand mole-
cules and release half an oxygen molecule. This stage is accompa-
nied by 62.7% weight loss in the TG curve. The remaining final fired
product is CoO representing 10.7% (Scheme 3).
Non-isothermal calculations were used extensively to evaluate
the thermodynamic and kinetic parameters for the different ther-
mal decomposition steps of the Co(II) complexes were determined
using the Coats–Redfern [27] and Horowitz–Metzger [28].
The rate of decomposition of a solid depends upon the temper-
ature and the amount of material. The expression for the thermal
decomposition of a homogeneous system has the following general
form:
The [Cd(Ho-HAHNH)2] complex is thermally stable up to 335 °C
above which point partial decomposition begins. In the tempera-

R.R. Zaky et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 683–694
689
Table 5
d
dt
a
¼ KðTÞgð
aÞ
ð1Þ
The molecular parameters of the ligand and its complexes.
The assignment of the
theoretical parameters
The compound
investigated
The theoretical data
Where t is the time, T is the absolute temperature and
gree of transformation defined as:
a is the de-
Total energy
H2o-HAHNH
[Co(Ho-HAHNH)2]
[Hg(H2o-
ꢀ85364.0706966 (kcal/
mol)
ꢀ136.036288981 (a.u.)
ꢀ4517.0013846 (kcal/
mol)
wo ꢀ wt
a
¼
Total energy
Binding energy
wo ꢀ w
1
In which wo, wt and w are the weights of the sample before
1
Isolated atomic energy
Electronic energy
ꢀ80847.0693120 (kcal/
the degradation, at temperature t and after total conversion,
respectively. K(T) is the rate coefficient that usually follows the
mol)
ꢀ619217.2816306(kcal/
mol)
533853.2109341(kcal/
mol)
Arrhenius equation. The differential conversion function, g(
may present various functional forms but its most commonly
form for solid–state reactions is g( )n, where n is the
a)
Core–core interaction
Heat of Formation
a
) = (1ꢀ
a
ꢀ31.7823846 (kcal/
reaction order, assumed to remain constant during the reaction
mol)
[29,30].
Dipole moment
HOMO
LUMO
2.65 (Debys)
The rate constant is normally expressed by the Arrhenius
equation:
ꢀ8.810811
ꢀ1.089322
Total energy
ꢀ181373.9200668
ꢀ
ꢁ
Ea
RT
(kcal/mol)
K ¼ A exp
ꢀ
ð2Þ
Total energy
Binding energy
ꢀ289.037704065 (a.u.)
ꢀ8686.6488648 (kcal/
mol)
Where Ea is the activation energy, A is the Arrhenius pre-exponen-
tial factor which indicates how fast the reaction occurs and R is the
gas constant in (J molꢀ1 K). Substituting in Eq. (1), we get:
Isolated atomic energy
Electronic energy
ꢀ172687.2712020
(kcal/mol)
ꢀ1953127.7461738
(kcal/mol)
ꢀ
ꢁ
d
dt
a
Ea
RT
¼ A exp
ꢀ
gð
aÞ
ð3Þ
Core–core interaction
Heat of formation
ꢀ42.3760279 (kcal/
mol)
ꢀ268.2028648 (kcal/
mol)
When the reaction is carried out under a linear temperature pro-
gram (T = To + bt, where b = dT/dt is the heating rate and To the start-
ing temperature). A large number of decomposition processes can
be represented as first order reaction [31]. Particularly, the degrada-
tion of the investigated series of metal complexes was suggested to
be first order in sample weight reaction. Therefore we will assume
n = 1 for the remainder of the present text. Under this assumption
the integration of Eq. (3) leads to:
Dipole moment
HOMO
LUMO
3.315 (Debys)
ꢀ3.84974
ꢀ1.039509
Total energy
ꢀ141239.1015403
HAHNH)(OAc)2(H2O)2] (kcal/mol)
Total energy
Binding energy
ꢀ225.078807463 (a.u.)
ꢀ6415.4095063 (kcal/
mol)
Isolated atomic energy
Electronic energy
ꢀ134823.6920340
ꢀ
ꢁ
Z
T
(kcal/mol)
A
b
E
RT
lnð1 ꢀ
aÞ ¼ ꢀ
Exp
ꢀ
dT
ð4Þ
ꢀ1301268.8363412
(kcal/mol)
1160029.7348009
(kcal/mol)
To
Core–core Interaction
Heat of formation
On the basis of Eq. (4), it is possible to analyze experimental data by
the integral method, in order to determine the degradation kinetic
parameters A and Ea. The temperature integral in the right-hand
side of Eq. (4) has no exact analytical solutions and several kinds
of approximations are generally used. Two methods that differ on
the way of resolving Eq. (4) are compared using the TGA data of
the studied complexes. These methods are
ꢀ353.5665063 (kcal/
mol)
Dipole moment
HOMO
LUMO
8.044 (Debys)
ꢀ5.868872
ꢀ1.131408
Eah
RT2s
ln½ꢀlnð1 ꢀ
aÞꢄ ¼
Forn ¼ 1
ð6Þ
ð7Þ
Coats–Redfern method
The Coats–Redfern [27] method is as follows:
"
#
!
1ꢀn
1ꢀð1ꢀ
a
1ꢀn
Þ
A RT2S
b E
Ea Eah
ꢂ
ꢃ
ꢀ
ꢁ
ln
¼ln
ꢀ þ
RTS
For n–1
gð
a
Þ
AR
bE
Ea
RT
RT2S
ln
¼ ln
ꢀ
ð5Þ
T2
Where h = T–Ts, Ts is the DTG peak temperature, T the temperature
corresponding to weight loss Wt. In this method a straight line
should be observed between ln
Where g(
a
) = 1-(1ꢀ
a
)1ꢀn/1ꢀn for n – 1 and g(
a
) = ꢀln(1ꢀ
a
) for
n = 1, R is the universal gas constant. The correlation coefficient, r,
v
½ꢀlnð1 ꢀ Þꢄ and h with a slope of
a
Ea
was computed using the least square’s method for different values
h
i
.
RT2s
gðaÞ
of n (n = 0.33, 0.5, 0.66 and n = 1) by plotting ln
versus 1/T for
T2
Figs. 3 and 4 show the Horowitz–Metzger plots for the metal
the investigated metal complexes are shown in Figs. 1 and 2. The
n-value which gave the best fit (r ꢃ 1) was chosen as the order
parameter for the decomposition stage of interest. The slope of
the straight line equal (Ea/R) and the intercept the pre- exponential
factor, A can be determined. The data obtained are represented in
Table 6.
complexes under study. The obtained data are recorded in Table 7.
Thermodynamic parameters
The other thermodynamic parameters of activation can be cal-
culated by Eyring equation [32,33]:
D
Hꢅ ¼ Ea ꢀ RT
ð8Þ
Horowitz–Metzger method
The Horowitz–Metzger [28] relation was used to evaluate the
degradation kinetics is
ꢀ
ꢁ
hA
D
Sꢅ ¼ R ln
kBT
ꢀ 1
ð9Þ

690
R.R. Zaky et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 683–694
6
5
+
13 10
2
2
Scheme 3. Decomposition pathway of [Co(Ho-HAHNH)2] complex.
D
Gꢅ ¼
D
H ꢀ T
D
S
ð10Þ
(iv) The activation energy Ea increases somewhat through the
degradation steps revealing the high stability of the remain-
ing part suggesting a high stability of complexes character-
ized by their covalence.
Where
D
H⁄ is the enthalpy of activation (kJ/mol), S⁄ is the entropy
D
of activation (kJ/mol.K) and
D
G⁄ is the Gibbs free enthalpy of activa-
tion (kJ/mol), h is the Planck constant and kB the Boltzmann con-
stant. The kinetic parameters evaluated by Coats–Redfern and
Horowitz–Metzger methods are listed in Tables 6 and 7, respec-
tively. From the results the following remarks can be pointed out:
(v) The negative value of the entropy of activation,
D
S⁄
of some decomposition steps in case of the ion
exchanger and its metal complexes with all investi-
gated metal ions indicates that the activated frag-
ments have more ordered structure than the
undecomposed ones and the later are slower than
the normal [34,35].
(i) The kinetic parameters (Ea, A,
D D D
H⁄, S⁄ and G⁄) of all stud-
ied complexes have been determined (Tables 6 and 7) using
CR and HM methods. The values obtained from the two
methods are quite comparable.
(vi) The positive sign of activation enthalpy change,
D
H⁄ indi-
cates that the decomposition stages are endothermic
processes.
(vii) The high values of the energy of activation, Ea of the com-
plexes reveals the high stability of such chelates due to their
covalent bond character [36].
(ii) The thermodynamic data obtained with the two methods
are in harmony with each other.
(iii) The correlation coefficients of the Arrhenius plots of the
thermal decomposition steps were found to lie in the range
0.9820–0.9996, showing a good fit with linear function.

R.R. Zaky et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 683–694
691
(A) -12
lnX n=1
(A)
lnX n=0.66
lnX n=1
-13
lnX n=0.33
lnX n=0
lnX n = 0.5
lnX n=0.66
lnX n=0.33
lnX n=0
-13
lnX n = 0.5
-14
-15
-14
-15
-16
-16
0.00140
0.00145
0.00140
0.00145
0.00150
1000/T
1000/T
(B)
(B) -13
lnX n=1
lnX n=1
lnX n=0.66
lnX n=0.33
lnX n=0
-13
-14
-15
lnX n=0.66
lnX n=0.33
lnX n=0
lnX n = 0.5
lnX n = 0.5
-14
-15
0.00120
0.00125
1000/T
0.00130
0.00125
0.00130
1000/T
Fig. 2. Coats–Redfern plot of (A) first degradation step and (B) second degradation
step for [Cd(Ho-HAHNH)2] complex.
Fig. 1. Coats–Redfern plot of (A) first degradation step and (B) second degradation
step for [Co(Ho-HAHNH)2] complex.
metal complexes exhibited greater antifungal activity against
Aspergillus sp. as compare to the standard drug Miconazole. The
Co(II), Cd(II) and U(VI)O2 complexes show better activity against
Stemphylium sp. than the standard, whereas, Cd(II) complex is
more effective against Trichoderma sp. From the data it has also
been observed that the complexes are more active than the ligand
[40]. The toxicity of the complexes can be related to the strength of
the metal–ligand bond, besides other factors such as size of the cat-
ion [41]. Where, the higher the size of metal ion, the higher the
antifungal activity of the complex. Also, the study exhibited that
any metal salt alone has higher activity than its investigated com-
plex. However, metal salts alone can not be used as antibacterial
agents because of their natural toxicities and the probability of
binding to the free ligand [42] presented in the biological systems
such as the nitrogen bases of nucleic acids and/or proteins.
The mode of action of the compounds may involve formation of
a hydrogen bond through the azomethine group (>C@N–) with the
active centers of cell constituents [43,44] resulting in interferences
with the normal cell process.
(viii) The positive sign of
D
G⁄ for the investigated complexes
reveals that the free energy of the final residue is higher than
that of the initial compound, and hence all the decomposi-
tion steps are non-spontaneous processes. This results from
increasing the T
override the values of
D
S⁄ clearly from one step to another which
D
H⁄ reflecting that the rate of removal
of the subsequent species will be lower than that of the prec-
edent one [37–39].
Antifungal activity
In the screening of antifungal activity it has been envisaged that
the studies must lead to an overall comparison of activities be-
tween the ligand and its metal complex so that the mechanism
of the activity can be understood. The experimental antifungal
activity data (Fig. 5) indicate that the ligand as well as its com-
plexes shows an appreciable activity against Aspergillus sp., Stem-
phylium sp. and Trichoderma sp. at 0.5, 1.0 and 1.5 mg/ml
concentration. Their activity generally increases with increasing
the concentration of the compounds. DMSO control has shown a
negligible activity as compare to the ligand and its metal com-
plexes. The complexes are more effective against Aspergillus sp.
than Stemphylium sp. and Trichoderma sp. [Cd(Ho-HAHNH)2] shows
the highest activity (98%) against Aspergillus sp. at the concentra-
tion of 1.5 mg/ml among all the metal complexes. The same com-
plex also shows the highest activity (94%) against Stemphylium sp.
The antifungal activity varies in the following order of fungal
species: Aspergillus sp. > Stemphylium sp. > Trichoderma sp. All the
However, this is certain that o-Hydroxy acetophenone as well as
their metal chelate can offer this novel application if sufficient
studies are centered on their biological activities. The present work
is a step further in this direction.
Antibacterial activity
The ligand and their metal complexes, standard drug Ampicillin
and DMSO solvent control were screened separately for their anti-
bacterial activity against E. coli and Clostridium sp. at 1.0 and

692
R.R. Zaky et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 683–694
Table 6
Kinetic Parameters of complexes evaluated by Coats-Redfern equation.
Complex
Peak
Mid Temp (K)
Ea (kJ/mol)
A (Sꢀ1
)
D
H⁄ (kJ/mol)
D
S⁄ (kJ/mol K)
D
G⁄ (kJ/mol)
[Co(Ho-HAHNH)2]
1st
2nd
1st
680
819
670
837
617.98
742.71
410.89
428.16
2.2985E-6
1.5160E-6
2.5196E-6
9.6590E-7
612.32
735.90
405.32
421.20
ꢀ0.35970
ꢀ0.36471
ꢀ0.35882
ꢀ0.36864
856.93
1034.61
645.73
729.76
[Cd(Ho-HAHNH)2]
2nd
1
lnX n=1
(A)
lnX n=1
lnX n=0.66
lnX n=0.33
lnX n=0
(A)
lnX n=0.66
lnX n=0.33
lnX n=0
0
-1
-2
-3
-4
-5
lnX n = 0.5
lnX n = 0.5
0
-1
-2
0
10
20
30
40
50
-40
-30
-20
-10
0
T-Ts
T-Ts
lnX n=1
1
(B)
(B)
lnX n=1
lnX n=0.66
lnX n=0.33
lnX n=0
lnX n=0.66
lnX n=0.33
lnX n=0
-1
-2
-3
-4
-5
lnX n = 0.5
lnX n = 0.5
0
-1
-2
-100
-90
-20 -10
0
10 20 30 40 50 60 70
T-Ts
T-Ts
Fig. 4. Horowitz–Metzger plot of (A) first degradation step and (B) second
degradation step of [Cd(Ho-HAHNH)2] complex.
Fig. 3. Horowitz–Metzger plot of (A) first degradation step and (B) second
degradation step of [Co(Ho-HAHNH)2] complex.
2.0 mg/ml concentration. Their activity is greatly enhanced at the
higher concentration [45]. The activity of the complexes has been
compared with the activity of a common standard antibiotic Ampi-
cillin and % Activity Index for the complexes has been calculated.
The antibacterial results suggest that the ligand and its complexes
(Tables 8 and 9) show a moderate activity against both the bacteria
[46,47] as compared to the standard drug (Ampicillin). The metal
complexes show higher antibacterial activity than the ligand. The
% Activity Index data show the highest activity for [Cd(Ho-
HAHNH)2] against E. coli and Clostridium sp. at the concentration
of 2.0 mg/ml. The complexes are more effective against Clostridium
sp. than E. coli and show better antibacterial activity than the li-
gand. According to Overtone’s concept of cell permeability, the li-
pid membrane that surrounds the cell favors the passage of only
the lipid-soluble materials due to which liposolubility is an impor-
tant factor, which controls the antibacterial activity. On chelation,
the polarity of the metal ion will be reduced to a greater extent due
to the overlap of the ligand orbital and partial sharing of the posi-
tive charge of the metal ion with donor groups. Further, it increases
Table 7
Kinetic parameters of complexes evaluated by Horowitz-Metzger equation.
Complex
Peak
Mid Temp (K)
Ea (kJ/mol)
A (Sꢀ1
)
D
H⁄ (kJ/mol)
D
S⁄ (kJ/mol K)
D
G⁄ (kJ/mol)
[Co(Ho-HAHNH)2]
1st
2nd
1st
680
819
670
837
617.45
742.26
409.45
429.73
2.1190E-6
1.4859E-6
2.4832E-6
8.8470E-7
611.79
735.45
403.88
422.78
ꢀ0.36038
ꢀ0.36488
ꢀ0.35894
ꢀ0.36937
856.86
1034.29
644.38
731.94
[Cd(Ho-HAHNH)2]
2nd

R.R. Zaky et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 683–694
693
100
(A)
90
80
70
60
50
0.5 mg/ml
1 mg/ml
1.5 mg/ml
40
30
20
10
0
100
(B)
90
80
70
60
50
0.5 mg/ml
1 mg/ml
1.5 mg/ml
40
30
20
10
0
100
(C)
90
80
70
60
50
0.5 mg/ml
1 mg/ml
1.5 mg/ml
40
30
20
10
0
Fig. 5. Effect of ligand and its metal complexes toward (A) Aspergillus sp., (B) Stemphylium sp. and (C) Trichoderma sp.
the delocalization
p
-electrons over the whole chelate ring and
hydrogen bond through the azomethine group with the active cen-
ter of cell constituents, resulting in interference with the normal
cell process.
The negative results can be attributed either to the inability of
the complexes to diffuse into the Gram-negative bacteria cell
membranes and hence unable to interfere with its biological activ-
ity or they can diffuse and inactivated by unknown cellular mech-
anism i.e. bacterial enzymes.
enhances the lipophilicity of the complexes. This increased
lipophilicity enhances the penetration of the complexes into lipid
membranes and blocking of the metal binding sites in the enzymes
of microorganisms. These complexes also disturb the respiration
process of the cell and thus block the synthesis of the proteins
that restricts further growth of the organism. Furthermore, the
mode of action of the compound may involve formation of a
Table 8
Antibacterial activity of the ligand and its complexes.
Compound
E. coli (mg/ml)
Clostridium sp. (mg/ml)
Diameter of inhibition zone (in mm)
% Activity index
Diameter of inhibition zone (in mm)
% Activity index
1.0
2.0
1.0
2.0
1.0
2.0
1.0
2.0
H2o-HAHNH
3
4
19
81
81
63
100
21
84
90
68
100
5
7
36
86
86
64
100
41
88
94
71
100
[Co(Ho-HAHNH)2]
[Cd(Ho-HAHNH)2]
[UO2(H2o-HAHNH)(OAc)2(H2O)2]
Ampicillin
15
13
10
16
18
16
13
19
12
12
9
14
16
12
17
14

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R.R. Zaky et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 683–694
[18] K. Nakamoto, Infrared Spectra of Inorganic, Coordination Compounds, Wiley
Table 9
Interscience, New York, 1970.
Antimicrobial activitiy in terms of MIC (mg/ml) after 48 h.
[19] K. Pyta, P. Przybylski, A. Huczyn´ ski, A. Hoser, K. Wozn´ iak, W. Schilf, B.
Kamien´ ski, D. Eugeniusz Grech, J. Mol. Struct. 970 (2010) 147–154.
[20] D.X. West, D.L. Huffman, J. Trans, Met. Chem. 14 (1989) 190–194.
[21] G.A.A. Al-Hazmiy, M.S. El-Shahawiz, I.M. Gabr, A.A. El-Asmy, J. Coord. Chem. 58
(2005) 713–723.
[22] S.P. McGlynn, J.K. Smith, J. Chem. Phys. 35 (1961) 105–116.
[23] L.H. Jones, Spectrochim. Acta. 10 (1958) 395–403.
[24] M.C. Rodríguez-Argüelles, S. Mosquera-Vázquez, P. Tourón-Touceda, J.
Sanmartín-Matalobos, A.M. García-Deibe, M. Belicchi-Ferrari, G. Pelosi, C.
Pelizzi, F. Zani, J. Inorg. Biochem. 101 (2007) 138–143.
[25] A.B.P. Lever, Inorganic Electronic Spectroscopy, Elsevier, Amsterdam, 1968.
[26] S. Sagdinc, B. Koksoy, F. Kandemirli, S.H. Bayari, J. Mol. Struct. 917 (2009) 63–
70.
[27] A.W. Coats, J.P. Redfern, Nature 20 (1964) 68–69.
[28] H.H. Horowitz, G. Metzger, Anal. Chem. 35 (1963) 1464–1468.
[29] M.S. Abu-Bakr, H. Sedaira, E.Y. Hashem, Talanta 41 (10) (1994) 1669–1674.
[30] D. Kara, M. Alkan, Talanta 55 (2001) 415–423.
[31] A. Broido, J. Ploym. Sci. A-2, 7 (1969) 1761–1773.
[32] K. Schwetlick, Kinetyczne Metody Badania Mechanizmow Reakcji, PWN
Warszawa, 1975.
Compounds
E. coli
Clostridium sp.
H2o-HAHNH
0.8
0.4
0.4
0.3
0.2
0.7
0.4
0.4
0.5
0.3
[Co(Ho-HAHNH)2]
[Cd(Ho-HAHNH)2]
[UO2(H2o-HAHNH)(OAc)2(H2O)2]
Ampicillin
The positive results suggested the very diffusion of the com-
plexes into the bacterial cells and were able to kill the bacterium
as indicated by the zones of inhibition of bacterial growth.
References
[1] T.A. Yousef, G.M. Abu El-Reash, T.H. Rakha, U. El-Ayaan, Spectrochim. Acta. 83
(1) (2011) 271–278.
[2] R.R. Zaky, T.A. Yousef, J. Mol. Struct. 1002 (2011) 76–85.
[3] A.S. El-Tabl, F.A. El-Saied, W. Plass, A.N. Al-Hakimi, Spectrochim. Acta, Part A 71
(2008) 90–99.
[4] S. Sivaramaiah, P.A. Reddy, J. Anal. Chem. 60 (2005) 828–832.
[5] A.A. El-Emam, F.F. Belal, M.A. Moustafa, S.M. El-Ashry, D.T. El-Sherbing, S.H.
Hansen II, Farmaco 58 (2003) 1179–1186.
[6] M.S. Niasari, A. Amiri, Appl. Catal. 290 (2005) 46–53.
[7] P. Pelagalli, M. Cacelli, C. Pelizz, M. Costa, Inorg. Chim. Acta 342 (2003) 323–
326.
[8] M.G. El-Meligy, S.E. El-Rafie, K.M. Abu-Zied, Desalination 173 (2005) 33–44.
[9] K.M. Ibrahim, I.M. Gabr, R.R. Zaky, J. Cood. Chem. 62 (7) (2009) 1100–1116.
[10] K.M. Ibrahim, I.M. Gabr, G.M. Abu El-Reash, R.R. Zaky, Monatsheft. Fur. Chemie.
140 (6) (2009) 625–632.
[11] R.R. Zaky, K.M. Ibrahim, I.M. Gabr, Spectrochim. Acta. 81 (1) (2011) 28–34.
[12] A.I. Vogel, Quantitative Inorganic Analysis, Longmans, London, 1989.
[13] N.L. Allinger, J. Am. Chem. Soc. 99 (1977) 8127–8134.
[14] HyperChem version 8.0 Hypercube, Inc., 2002.
[15] K.M. Ibrahium, T.H. Rakaha, A.M. Abdalla, M.M. Hassanian, J. Ind. Chem. 32
(1993) 361–363.
[16] T.A. Yousef, T.H. Rakha, Usama El Ayaan, G.M. Abu El Reash, J. Mol. Struct.
1007 (2012) 146–157.
[33] R.G. Mortimer, Physical Chemistry Harcourt and Science Technology Company,
Academic Press, San Diego, 2000.
[34] S.H. Guzara, Q.H. Jin, Chem. Res. Chin. Univ. 24 (2) (2008) 143–147.
[35] H.T.S. Britton, Hydrogen Ions, vol. I, third ed., Chapman and Hall, London, 1942.
[36] T. Taakeyama, F.X. Quinn, Thermal Analysis Fundamentals and Applications to
Polymer Science, John Wiley and Sons, Chichester, 1994.
[37] P.B. Maravalli, T.R. Goudar, Thermochim. Acta. 335 (1999) 35–41.
[38] K.K.M. Yusuff, R. Sreekala, Thermochim. Acta. 159 (1990) 357–368.
[39] S.S. Kandil, G.B. El-Hefnawy, E.A. Baker, Thermochim. Acta 414 (2004) 105–
113.
[40] K.N. Thimmaiah, G.T. Chandrappa, Rangaswamy, Jayarama, Polyhedron 3
(1984) 1237–1239.
[41] R. Nagar, J. Inorg. Biochem. 40 (1990) 349–356.
[42] R.B. Johari, R.C. Sharma, J. Ind. Chem. Soc. 65 (1988) 793–794.
[43] L. Mishra, V.K. Singh, Synth. Ind. J. Chem. 32A (1993) 446–449.
[44] J.R. Soares, T.C.P. Dinis, A.P. Cunha, L.M. Almeida, Free Radical Res. 26 (1997)
469–478.
[45] Z.H. Abd El-Wahab, M.R. El-Sarrag, Spectrochim. Acta. 60A (2004) 271–277.
[46] K. Deepa, K.K. Aravindakshan, Synth. React. Inorg. Met-Org. Nano-Met. Chem.
35 (2005) 409–416.
[47] P.K. Panchal, H.M. Parekh, M.N. Patel, Toxicol. Environ. Chem. 87 (2005) 313–
320.
[17] T.A. Yousef, O.A. El-Gammal, S.E. Ghazy, G.M. Abu El-Reash, J. Mol. Struct. 1007
(2011) 271–283.