Physicochemical studies and biological evaluation on (E)-3-(2-(1-(2- hydroxyphenyl)hydrazinyl)-3-oxo-N-(thiazol-2yl)propanamide complexes

Article abstract of DOI:10.1016/j.saa.2013.01.031

Hydrazone complexes of Co(II), Ni(II), Cu(II), Pd(II), Cd(II), Zn(II) and U(VI)O₂ with (E)-3-(2-(1-(2-hydroxyphenyl)hydrazinyl)-3-oxo-N- (thiazol-2yl)propanamide (H₂o-HAH) have been synthesized. The complex structure has been elucida

Full text of DOI:10.1016/j.saa.2013.01.031

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 133–144
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Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
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Physicochemical studies and biological evaluation on (E)-3-(2-(1-(2-hydroxy-
phenyl)hydrazinyl)-3-oxo-N-(thiazol-2yl)propanamide complexes
⇑
K.M. Ibrahim, R.R. Zaky , E.A. Gomaa, M.N. Abd El-Hady
Department of Chemistry, Faculty of Science, Mansoura University, Mansoura, 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
"
Schiff base complexes of (H2o-HAH)
were prepared.
"
The complex structure was
elucidated using different
characterization techniques.
Calculation of kinetic and
thermodynamic parameters.
Antimicrobial activities of all
compounds were studied.
"
"
a r t i c l e i n f o
a b s t r a c t
Article history:
Hydrazone complexes of Co(II), Ni(II), Cu(II), Pd(II), Cd(II), Zn(II) and U(VI)O2 with (E)-3-(2-(1-(2-
hydroxyphenyl)hydrazinyl)-3-oxo-N-(thiazol-2yl)propanamide (H2o-HAH) have been synthesized. The
complex structure has been elucidated by analysis (elemental and thermal), spectroscopy (1H NMR,
13C NMR, IR, UV–visible, ESR, MS) and physical measurements (magnetic susceptibility and molar con-
ductance). The kinetic and thermodynamic parameters for the different decomposition steps of some
complexes have been calculated using the Coats–Redfern equation. Also, the association and formation
constants of Co(II) ion in absolute ethanol solutions at 294.15 K have been calculated by using electrical
conductance. Moreover, the ligand and its complexes have been screened for their antibacterial (Esche-
richia coli and Clostridium sp.) and antifungal activities (Aspergillus sp. and Stemphylium sp.) by MIC
method.
Received 27 November 2012
Received in revised form 25 December 2012
Accepted 10 January 2013
Available online 26 January 2013
Keywords:
Hydrazone complexes
13C NMR & 1H NMR studies
Electrical conductance
Antimicrobial activity
Ó 2013 Elsevier B.V. All rights reserved.
Introduction
[1] and as analytical reagents [2]. As biologically active com-
pounds, hydrazones find applications in the treatment of diseases
Hydrazones, R1R2C@NNH2 are a special group of compounds in
the Schiff base family which derived from the condensation of
hydrazines with carbonyl compounds, namely aldehydes and ke-
tones. Hydrazones are known to function as chelating agents that
can form different complexes with transition metals. Several
hydrazones are obtained depending on the experimental condi-
tions; which have application as biologically active compounds
such as anti-tumor [3], tuberculosis [4], leprosy and mental disor-
der [5]. Tuberculostatic activity is due to the formation of stable
chelates with transition metals present in the cell [6]. Thus, many
vital enzymatic reactions catalyzed by these transition metals can-
not take place in the presence of hydrazones [7]. Hydrazones also
act as herbicides, insecticides, nematocides, rodenticides and plant
growth regulators [8,9].
We have recently published some bivalent transition metal
complexes of hydrazones derived from 3-hydrazinyl-oxo-N-(thia-
zole-2-)propanamide [10–12]. In continuation of our work on
hydrazones, the present work aims to synthesize and characterize
⇑
Corresponding author. Tel.: +20 0105193223; fax: +20 0502219214.
E-mail address: rania.zaky@yahoo.com (R.R. Zaky).
1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.01.031

134
K.M. Ibrahim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 133–144
complexes of (E)-3-(2-(1-(2-hydroxyphenyl)hydrazinyl)-3-oxo-N-
(thiazol-2-yl)propanamide (H2o-HAH) with Co(II), Ni(II), Cu(II),
Pd(II), Cd(II), Zn(II) and U(VI)O2 ions. The possible modes of chela-
tions, the geometry and the nature of bonding of the complexes are
discussed on the basis of various spectroscopic techniques (1H
NMR, 13C NMR, IR, UV–visible, ESR, MS). Also, their antimicrobial
activity have been tested.
230 °C; yield 80%; see Table 1). The purity of the compound was
checked by thin layer chromatography (TLC).
Preparation of complexes
The complexes were prepared by mixing equimolar amounts of
H2o-HAH with ethanolic and/or aqueous solution of acetate salt of
Ni(II), Co(II), Cd(II), Cu(II), Zn(II) and U(VI)O2; chloride salt of pd(II)
as potassium tetrachloropalladate. The reaction mixture was
heated on a water bath for 1–3 h. The precipitate was filtered off,
washed with hot EtOH and/or H2O successfully and finally pre-
served in a vacuum desiccator over anhydrous CaCl2.
Experimental
Materials and reagents
Conductance measurements
All chemicals used were of the analytical reagent grade (AR), and
of the highest purity available. They included 3-hydrazinyl-oxo-
N-(thiazole-2-) propanamide; o-hydroxyacetophenone (Aldrich);
All conductometric titrations were measured using 0.1 mmol of
H2o-HAH and 1 mmol of CoCl2 solution as an initial concentration
from each. 20 ml of ligand in absolute ethanol was taken and ti-
trated with small addition of metal with 0.5 ml intervals were done
and the specific conductances were measured. The specific conduc-
tivity (Ks) was achieved by using a conductometer of the type
(HANNA, H1 8819 N) and a cell constant equal (1).
Cu(CH3COO)2ꢀH2O,
Cd(CH3COO)2ꢀ2H2O,
UO2(CH3COO)2ꢀ2H2O,
Ni(CH3COO)ꢀ4H2O, Co(CH3COO)ꢀ4H2O, CoCl2ꢀ6H2O, Zn(CH3COO)2ꢀ
2H2O and PdCl2 (Sigma, Merck). Organic solvents used included
absolute ethyl alcohol, diethyl ether, and dimethylsulfoxid (DOMS).
These solvents were spectroscopic pure from BDH. De-ionized water
collected from all glass equipments was usually used in all
preparations.
Biological activity
Instrumentations
Antifungal activity
The antifungal activity of the ligand (H2o-HAH) and its metal
complexes Ni(II), Co(II), Cu(II), Cd(II), Zn(II), Pd(II) and U(VI)O2 were
screened against two types of fungi viz. Aspergillus sp. and Stemphy-
lium sp. These species were isolated from the infected organs of the
host plants on potato dextrose agar. The cultures of the fungi were
purified by single spore isolation technique. The solution in different
concentrations 0.5, 1 and 1.5 mg/ml of each compound in DMSO
were prepared for testing against spore germination. A drop of the
solution of each concentration was kept separately on glass slides.
The conidia, fungal reproducing spores 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 separate glass
slides. All the slides were incubated in humid chambers at room
temperature for 24 h. Each slide was observed under the microscope
for spore germination and percent germination was finally calcu-
lated. The results were also compared with a standard antifungal
drug Miconazole at the same concentrations.
Elemental microanalyses of the isolated solid complexes for C, H
and N were performed in the Microanalytical Center. The molar con-
ductanceofthecomplexes were determined by preparing 10ꢁ3 Msolu-
tions of the complexes in DMSO at room temperature and measured on
a YSI Model 32 conductivity bridge. The IR absorption spectra were re-
corded on a Mattson 5000 FTIR Spectrophotometer, in the range 4000–
400 cmꢁ1 in KBr disk. Magnetic moment values were evaluated at
room temperature (25 1 °C) using a Johnson Matthey magnetic sus-
ceptibility balance using Hg[Co(SCN)4] as calibrant. ESR spectrum of
Cu(II) complex was obtained on a Bruker EMX Spectrometer working
in the X-band (9.78 GHz) with 100 kHz modulation frequency. The
microwave power was set at 1 mW and modulation amplitude was
set at 4 Gauss. The low-field signal was obtained after four scans with
a tenfold increase in the receiver gain. A powder spectrum was ob-
tained in a 2 mm quartz capillary at room temperature. Mass spectra
were recorded on a Mattson 5000 FTIR spectrophotometer. 1H and
13C NMR spectra of the ligand and Cd(II), Zn(II), Pd(II) and U(VI)O2 com-
plexes were recorded in DMSO on an EM-390 (200 MHz) spectrometer.
The thermal analyses (TG, DTG and DTA) were carried out in dynamic
nitrogen atmosphere (20 mL/min) with a heating rate of 10 °C/min
using Shimadzu TG-60H and DTA-60H thermal analyzers. Ni(II), Co(II),
Cu(II), Pd(II), Cd(II), Zn(II) and U(VI)O2 contents in the complexes were
determined by the well known standard methods [13]. The antifungal
and antibacterial activities were carried out at the Microanalytical cen-
ter. The specific conductivity (Ks) was achieved by using a conduc-
tometer of the type (HANNA, H1 8819 N) and a cell constant equal
(1). The conductometer was connected with ultra-thermostat of
the type (Kottermann 4130) and a digital thermometer. The temper-
ature at which all measurements were achieved, was adjusted at
21 °C.
Antibacterial activity
The antibacterial activity of the all isolated compounds were stud-
ied against Clostridium sp. and Escherichia coli bacteria. The solution in
different concentrations 0.5, 1 and 1.5 mg/ml of each compound in
DMSO were prepared for testing against spore germination. Paper discs
of Whatman filter paper of uniform diameter (2 cm) were cut and
sterilized in an autoclave. The paper discs soaked inthe desired concen-
tration of the complex solutions were placed aseptically in the petri-
dishes containing nutrient agar media 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.
The antibacterial activity of a common standard antibiotic Ampicillin
was also recorded using the same procedure as above at the same con-
centrations and solvent.
Procedures
Preparation of (E)-3-(2-(2-hydroxybenzylidene)hydrazinyl)-3-oxo-
n(thiazole-2yl)propanamide
Results and discussion
(H2o-HAH) was prepared by reflux a mixture of 3-hydrazinyl-
oxo-N-(thiazole-2-)propanamide (0.01 mol; 2.00 g) and o-hydroxy
acetophenone (0.01 mol; 1.36 g) in absolute ethanol for 3 h
(Scheme 1). On cooling, yellow crystals were formed, filtered off,
washed with EtOH and Et2O and recrystallized from EtOH (M.p.:
IR spectra
In the IR spectrum of H2o-HAH (Scheme 2), the bands
observed at 1700, 1670, 1606, 1560, 3201, 3114 and 3446 cmꢁ1

K.M. Ibrahim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 133–144
135
CH3
H
N
H
N
H2
C
N
O
C
O
C
O
NH2
+
S
HO
3-hydrazinyl-oxo-N-(thiazole-2-)propanamide
(0.01 mol; 2.00 g)
o-Hydroxy acetophenone
(0.01 mol; 1.36 g)
Reflux for 3 h.
in absolute ethanol
H
H
CH3
C
H2
C
1N
2N
2N
1C
O
2C
O
1N
H
S
O
(E)-3-(2-(1-(2-hydroxyphenyl)hydrazinyl)-3-oxo-N-(thiazol-2yl)propanamide
C
(
o
U
O
2
(
C
H
Z
n
C
C
(
O
H
3
C
O
H 2
H
3
O
C
2
.
)
O
)
C
2
.
H
O
O
4
H
O
H
O
O
)
H
C
O
O
2
.
)
H 3
2
o
H
2
2
.
O
C
2
r
(
OH2
M
H
2
d
C
O
H3C
O
O
H2
O
O
O
O
M
H3C
O
O
H2O
O
O
N
Cd
N
O
H2O
Pd
Zn
O
O
N
N
[Cu(Ho-HAH)(OAc)(H2O)].H2O
[Ni(Ho-HAH)(OAc)(H2O)].H2O
N
O
M=
OH2
OH2
O
[Cd(Ho-HAH)(OAc)(H2O)].H2O
[UO2(o-HAH)(H2O)2].2H2O
[Co(o-HAH)(H2O)2].2H2O
M=
[Pd(Ho-HAH)(H2O)].H2O
[Zn(o-HAH)(H2O)].H2O
Scheme 1. The outline of the synthesis of ligand (H2o-HAH) and its complexes.
Table 1
Analytical and physical data of H2O-HAH and its metal complexes.
Compound
Empirical formula (Molecular mass) Color
MP (°C) Yield (%) % Found (Calcd.)
Exp. (Calcd.)
a
C
H
N
M
Km
H2o-HAH (1)
C14H14O3N4S 318.87 (318.59)
Yellow
Brown
Green
Brown
Yellowish-
white
230
80
80
75
85
70
52.85 (52.78) 4.28 (4.43) 17.41 (17.58) –
–
[Ni (Ho-HAH)(OAc)(H2O)]ꢀH2O (2) NiC16H20O7N4S 472.07 (471.54)
>300
>300
>300
>300
40.78 (40.75) 4.37 (4.28) 11.73 (11.88) 12.39 (12.49) 4
40.41 (40.36) 4.23 (4.24) 11.60 (11.76) 13.40 (13.35) 5
36.25 (36.55) 3.28 (3.72) 12.25 (12.18) 21.78 (21.41) 3
36.82 (36.60) 3.81 (3.84) 10.69 (10.67) 21.65 (21.41) 3
[Cu(Ho-HAH)(OAc)(H2O)]ꢀH2O (3) CuC16H20O7N4S 476.90 (476.15)
[Pd(Ho-HAH)(H2O)]ꢀH2O (4)
PdC14H17O5N4S 459.59 (460.03)
[Cd(Ho-HAH)(OAc)(H2O)]ꢀH2O (5) CdC16H20O7N4S 525.24 (525.02)
[Zn(o-HAH)(H2O)]ꢀH2O (6)
ZnC14H16O5N4S 418.16 (417.98)
Yellowish-
white
>300
70
40.17 (40.22) 4.03 (3.85) 13.44 (13.40) 15.62 (15.64) 3
[Co(o-HAH)(H2O)2].2H2O (7)
[UO2(o-HAH)(H2O)2].2H2O (8)
CoC14H20O7N4S 447.86 (447.32)
UO2C14H20O7N4S 658.99 (658.65)
Brown
Yellow
>300
>300
80
75
37.75 (37.59) 4.31 (4.50) 12.60 (12.52) 13.4 (13.12)
25.56 (25.52) 3.11 (3.06) 8.57 (8.51) 36.73 (36.14) 4
4
a
In DMSO (ohmꢁ1 cm2 molꢁ1).
are attributed to (C@O)2 [14],
t
(C@O)1,
t
t
(C@N)1,
t
(C@N)2 [15],
2233 cmꢁ1 regions suggest intramolecular hydrogen bonding
(OAHꢀ ꢀ ꢀO) [18].
t
(NH)1, (NH)2 [16] and t(OH) [17], respectively (see Table 2).
t
The appearance of (OH) as a broad band at lower wavenumber
and the two weak broad bands in the 1900–2080 and 2155–
The shifts of the characteristic absorption bands of the free li-
gand on complexation as well as the appearance of new vibrational

136
K.M. Ibrahim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 133–144
Scheme 2. 13C NMR spectra of (A) H2o-HAH, (B) [Zn(o-HAH)(H2O)2]ꢀH2O.
Table 2
Most important IR spectral bands of H2o-HAH and its metal complexes.
Compound
t
(OH)
t
(NH)1
t
(NH)2
t
(C@O)1
t
(C@O)2
t
(C@N)1
t
(C@Nꢂ)1
t
(C@Nꢂ)2
t
(CAO)1
t
(CAO)2
t
(MAO)
t
(MAN)
1
2
3
4
5
6
7
8
3446
3374
3409
3443
3442
3440
3372
3331
3201
3199
3174
3227
3222
–
3114
1700
1696
1700
1685
1683
–
1670
1606
1595
1594
1587
1590
1589
1594
1580
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
1640
1650
1601
1606
1604
1630
1608
1165
1163
1142
1105
1083
1095
1089
530
550
542
522
522
560
552
450
460
468
437
422
455
459
1596
1620
1598
1128
1148
1137
–
–
–
–
bands indicates H2o-HAH behaves in a tridentate and/or tetraden-
tate manner depending on the metal salt used and the reaction
conditions.
The IR spectra of [Cu(Ho-HAH)(OAc)(H2O)]ꢀH2O and [Ni(Ho-
HAH)(OAc)(H2O)]ꢀH2O complexes reflect that the (H2o-HAH) acts
as a mononegative tridentate ligand coordinating via the deproto-
nated enolized carbonyl oxygen (@CAOꢁ)2, azomethine nitrogen
(C@N)1 and hydroxyl group (OH). This mode of complexation is
nated enolized carbonyl oxygens (@CAOꢁ)1, (@CAOꢁ)2. This mode
of complexation is supported by (i) the shift of (C@N)1 to lower
wavenumber, (ii) the disappearance of (C@O)1, (C@O)2, (NH)1
and (NH)2 with simultaneous appearance of new band at 1128,
1083, 1604 and 1596 cmꢁ1 which assignable to
(CAO)1(enolic)
(C@Nꢂ)2 [15], respectively (iii)
(OH) vibrations remain more or less at the same po-
t
t
t
t
t
t
,
t
t
(CAO)2(enolic) [19],
(C@N)2 and
t t
(C@Nꢂ)1 and
t
sition and (iv) the IR spectrum of this complex shows new band at
522 and 422 cmꢁ1 which may be attributed to
(ZnAO) and
t(ZnAN) [20], respectively.
supported by the following observations: (i) the shift of
t
(OH)
(C@N)1 to lower wave numbers, (ii) the disappearance of
(C@O)2 and (NH)2 with simultaneous appearance of new
t
and
t
both
t
t
Finally, for [UO2(o-HAH)(H2O)2]ꢀ2H2O and [Co(o-HAH)(H2O)2]-
bands at 1163, 1165 and 1640, 1650 cmꢁ1 which assignable to
ꢀ2H2O complexes, H2o-HAH acts as a binegative tetradentate ligand
coordinating through the two deprotonated enolized carbonyl oxy-
gen (@CAOꢁ)1, (@CAOꢁ)2, azomethine nitrogen (C@N)1 and hydro-
xyl group (OH). This mode of complexation is supported by the
disappearance of (C@O)1, (C@O)2, (NH)1 and (NH)2 with simulta-
neous appearance of new band at 1137–1148, 1089–1095, 1608–
t
(CAO)2(enolic) [19] and t
(C@Nꢂ)2 [15], respectively and (iii) the
appearance of new bands in 530–550 and 450–460 cmꢁ1 which
may be attributed to (MAO) and (MAN) [20], respectively.
Also, in [Pd(Ho-HAH)(H2O)]ꢀH2O and [Cd(Ho-HAH)(OAc)(H2-
O)]ꢀH2O complexes, H2o-HAH acts as a mononegative tridentate li-
gand coordinating via the carbonyl oxygen (C@O)1, the azomethine
nitrogen (C@N)1 and the deprotonated enolized carbonyl oxygen
(@CAOꢁ)2. This mode of complexation is supported by: (i) the dis-
1630 and 1598–1620 cmꢁ1 region assignable to
(CAO)2(enolic) [19],
(C@Nꢂ)1 and (C@Nꢂ)2 [15], respectively.
The negative shift of both (C@N)1 and (OH). Also, the IR spectra
t(CAO)1(enolic),
t
t
t
t
t
appearance of
of new bands at 1105, 1142 and 1601, 1606 cmꢁ1 which assignable
to (CAO)2(enolic) [19] and
(C@Nꢂ)2 [15], respectively, (ii) shift of
azomethine nitrogen ((C@N)1 and (C@O)1 to lower wave numbers
and (iii) the appearance of new bands in the 522–542 and 437–
468 cmꢁ1 which may be attributed to
(MAO) and (MAN) [20],
respectively. Moreover, the IR spectrum of the [Zn(o-HAH)(H2-
O)]ꢀH2O shows that H2O-HAH acts as a binegative tridentate ligand
coordinating via the azomethine nitrogen (C@N)1, the two deproto-
t
(C@O)2 and
t
(NH)2 with simultaneous appearance
of these complexes show new bands in 552–560 and 455–
459 cmꢁ1 regions which may be attributed to
[20], respectively.
t(MAO), t(MAN)
t
t
t
The complexes which have coordinated water molecules have
two sharp bands observed in 851–869 and 542–579 cmꢁ1 attrib-
t
t
uted to
The acetate complexes show two bands in 1513–1557 and
1413–1449 cmꢁ1 which can be assigned to
as(OACAO) and s(-
OACAO) of acetate group. The difference between those two bands
qr(H2O) [21] and qw(H2O) [21] vibrations, respectively.
t
t

K.M. Ibrahim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 133–144
137
Table 3
strong evidence for the presence of the acetate group. The other
ring carbon atoms did not show significant shifts.
The 1H NMR spectral data of (H2o-HAH) and its diamagnetic complexes.
Compounds
(OH)
(NH)1
(NH)2
ACH2
ACH3
Aromatic protons
Electronic spectra and magnetic moment measurements
1
4
5
6
8
13.06
12.89
12.49
12.53
10.25
12.89
11.95
11.98
–
11.20
3.69
3.54
3.52
3.45
3.49
1.88
1.83
1.91
1.90
1.86
7.21–7.78
7.34–7.89
7.31–8.06
7.19–8.12
8.78–9.81
–
–
–
–
The electronic spectrum of [Ni(Ho-HAH)(OAc)(H2O)]ꢀH2O com-
plex shows two bands at 16949 and 27,778 cmꢁ1 (see Table 5)
–
ꢁ
ꢁ
assigned to A2g ! Tꢁ1gðFÞ and A2g
!
3Tꢁ1gðPÞ transitions, respec-
3
3
3
tively, in an octahedral geometry [25]. The calculated values of
Dq, B, b and t2
structure. The position of t1 (10527 cmꢁ1) is calculated theoreti-
cally [25]. The values of the magnetic moments value ( eff. = 3.2
BM) can be taken as an additional evidence for an octahedral
geometry.
/t1 values lie in the range reported for an octahedral
(98, 106 cmꢁ1) indicates the bidentate bonding for the acetate
group [21].
l
The IR spectrum of [UO2(o-HAH)(H2O)2]ꢀ2H2O complex displays
three bands at 921 and 845 cmꢁ1 assigned to
t3 and t1 vibrations,
respectively, of the dioxouranium ion. The t3 value is used to cal-
The electronic spectrum of [Co(o-HAH)(H2O)2]ꢀ2H2O complex
shꢁows two bands aꢁt 16,667 and 18,518 cmꢁ1 attributed to
culate the force constant (F) of
t
(U@O) by the method of McGlynn
4T1g
!
4Aꢁ2gðFÞ and T1g ! Tꢁ1gðPÞ transitions, respectively, in an
4
4
et al. [22]:
2
2
octahedral configuration [25]. The calculated values of Dq, B, b
ð
t3Þ ¼ ð1307Þ ðFUAOÞ=14:103
ð1Þ
and t2
/
t
1 are in good agreement with those reported for octahedral
1 (7937 cmꢁ1) is calculated the-
The force constant obtained for uranyl complex was then
substituted into the relation given by Jones [23]:
Co(II) complexes. The position of
t
oretically [25]. Also, the magnetic moment value (5.1 BM) is con-
sistent with octahedral geometry around the Co(II) ion.
RUAO ¼ 1:08ðFUAOÞꢁ1=3 þ 1:17
to give an estimate of the (UAO) bond length in Å. The calculated
FU@O and RU@O values are 7.003 mdynes Åꢁ1 and 1.734 Å, respec-
tively, fall in the usual range for the uranyl complexes [22].
ð2Þ
The Cu(II) complex has magnetic moment value (2.1 BM), indi-
cating the presence of Cu(II) ion. The electronic spectrum of
[Cu(H2O-HAH)(OAc)(H2O)]ꢀH2O complex shows a broad band at
1689ꢁ1 cmꢁ1 with a shoulderꢁat 14286 cmꢁ1 which may be assigned
ꢁ
2
2
2
to B1g ! Eg and B1g
!
2A1g transitions, respectively, in a tetrag-
onally distorted octahedral configuration [25].
Nuclear magnetic resonance spectral studies
The electronic spectrum of [UO2(o-HAH)(H2O)2]ꢀ2H2O complex
showþs two bands at 23,809 and 27,778 cmꢁ1 may be attributed
The 1H NMR and 13C NMR spectra of H2O-HAH and its Pd(II),
Cd(II), Zn(II) and U(VI)O2 complexes were recorded in d6-DMSO.
The 1H NMR spectrum of H2O-HAH shows three signals at 13.06,
12.89 and 11.20 ppm assignable to the protons of (OH), (NH)1
and (NH)2, 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 bond-
ing. The multiplet signals observed in the 7.21–7.78 ppm region
are assigned to the aromatic protons. The sharp singlet observed
at 3.69 ppm is assigned to active methylene protons (ACH2). Also,
the 1H NMR spectra of the Pd(II) and Cd(II), complexes show the
signals attributed to the (NH)1 and OH protons indicating that
these groups play no part in coordination. But, the lack of signal
due to (NH)2 proton emphasizes the deprotonation of the enolized
carbonyl oxygen (@CAOꢁ)2. Also, the lack of signals due to (NH)1
and (NH)2 protons in the 1H NMR spectrum of the diamagnetic
Zn(II) complex emphasizes the deprotonation of the enolized car-
bonyl oxygen (@CAOꢁ)1 and (@CAOꢁ)2. Moreover, in case of
U(VI)O2 complex the protons attributed to (NH)1 and (NH)2 are dis-
appear and the (OH) proton showed an upfield shift on
complexation.
to 1Eg
[25].
!
2pu transition and charge transfer n ? pꢂ, respectively
The diamagnetic [Pd(Ho-HAH)(H2O)]ꢀH2O complex shows a
ꢁ
ꢁ
band at 22,223 cmꢁ1 which is assigned to A1g ! B1g transition
1
2
in a square-planar configuration [26].
ESR studies
The room temperature solid-state ESR spectrum of [Cu(H2O-
HAH)(OAc)(H2O)]ꢀH2O has axially symmetric g-tensor parameters
with g|| (2.40) > g\ 2.09) > 2.0023 indicating that the copper site
has a dx2
ground-state characteristic of tetrahedral, square pla-
ꢁy2
nar or octahedral stereochemistry [27]. In axial symmetry the g-
values are related by the expression, G = (g// – 2)/(g\ – 2) = 4,
where G is the exchange interaction parameter. According to Hath-
away [28], the calculated G value was 4.6 suggesting that there are
no copper–copper exchange interactions.
The ability of A|| (160 ꢃ 10ꢁ4 cmꢁ1) to decrease with increasing
of g// (2.23) is an evidence of an increase of the tetrahedral distor-
tion in the coordination sphere of copper [29,28]. In order to quan-
tify the degree of distortion of the Cu(II) complexes, we selected
the f factor g||/A|| obtained from the ESR spectrum. Where, the f
factor is regarded as an empirical index of tetrahedral distortion.
For this complex, the g||/A|| quotient is 139, demonstrating the
presence of significant dihedral angle distortion in the dxy-plane
and indicating a distorted octahedral geometry. Superhyperfine
From 13C NMR spectral data (Table 4 and Scheme 2), the signals
for the C7, C8 and C10 showed an upfield shift on complexation [24]
compared with the free ligand in all diamagnetic complexes.
While, C1 showed an downfield shift on complexation in case of
U(VI)O2 complex. Furthermore, in case of Cd(II) complex the
appearance of new signals at d = 175 ppm and d = 52 ppm give
Table 4
13C NMR Chemical shifts in (ppm) assignments for H2O-HAHNH and its diamagnetic complexes.
Compound
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C13
1
4
5
6
8
163
164
164
165
169
118
117
118
118
122
134
134
133
133
134
123
123
123
122
123
131
130
129
131
130
120
119
121
1212
118
170
163
163
162
160
177
171
170
160
162
46
54
54
56
56
167
158
158
151
154
164
164
164
163
164
112
111
112
110
112
141
140
140
141
142

138
K.M. Ibrahim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 133–144
Table 5
Magnetic moments, electronic spectra and ligand field parameters of metal complexes of H2o-HAH.
Compound
leff. (BM)
Band position (cmꢁ1
)
Dq (cmꢁ1
)
B (cmꢁ1
)
b
t2/t1
2
7
3
8
4
3.2
5.1
2.1
Diam.
Diam.
16,949; 27,778
16,667; 18,518
16,891; 14,286
23,809; 27,778
22,223
1051
919
–
–
–
876
766
–
–
–
0.8
0.8
–
–
–
1.6
2.1
–
–
–
structure for this complex was not seen at higher fields, excluding
any interaction of the nuclear spins of nitrogen (I = 1) with the un-
paired electron density on Cu(II) [30].
Kinetic data
The kinetic and thermodynamic parameters of thermal degra-
dation process have been calculated using Coats–Redfern model
[32]. Coats–Redfern relation is as follows:
Molecular orbital coefficients,
a
2 (covalent in-plane
r-bonding)
and b2 (covalent in-plane
p-bonding) were calculated:
ꢂ
ꢃ
ꢀ
ꢁ
lnð1 ꢁ
aÞ
AR
bE
E
RT
ꢀ
ꢁ
ln ꢁ
¼ ln
ꢁ
ð5Þ
A==
0:036
3ðg? ꢁ 2:0023Þ
T2
a2
¼
þ ðg== ꢁ 2:0023Þ þ
þ 0:04
ð3Þ
7
where
a represents the fraction of sample decomposed at time t,
defined by:
ðg== ꢁ 2:0023ÞE
ꢁ8ka2
b2 ¼
ð4Þ
wo ꢁ wt
a
¼
ð6Þ
wo ꢁ w
1
2Aꢁ1g transition.
ꢁ
k = 828 cm–1 for the free ion and E is the B1g
As a measure of the covalence, the value of a2 (0.75) and b2
(0.61) for the complex indicate that the in-plane -bonding and
in-plane -bonding are appreciably covalent and are consistent
!
2
wo, wt and w are the weight of the sample before the degradation,
1
at temperature t and after total conversion, respectively. T is the
derivative peak temperature. b is the heating rate = dT/dt, E and A
are the activation energy and the Arrhenius pre-exponential factor,
respectively. A plot of versus 1/T gives a straight line whose slope
(E/R) and the pre-exponential factor (A) can be determined from
the intercept. (see Table 6)
r
p
with very strong in-plane p-bonding in this complex.
Thermal analysis
ꢂ
ꢃ
lnð1 ꢁ
a
Þ
ln ꢁ
The TG of the isolated complexes was taken as a proof for the
existing of H2O molecules as well as the anions to be outside
and/or inside the coordination sphere [31,32]. The water of crystal-
lization lost in 32–150 °C regions. The complexes show thermal
stability rather than the ligand where the beginning of its decom-
position shifts to higher temperature (205–294 °C). In general, all
complexes are thermally stable but [Ni(Ho-HAH)(OAc)(H2O)]ꢀH2O
is the highest one. It is thermally stable up to 294 °C. In the tem-
perature range 294–350 °C, the TG curve displays 30.0% weight
loss which could be ascribed to the elimination of the loosely
bound (C5H5N2OS) moiety. The final weight loss of 33.8% ending
at 498 °C, is largely attributed to complete decomposition of the
organic molecule, alongside rupture of the chelate bond, leaving
NiO comprising 15.8% of the initial mass of the complex as shown
in Table 4.
T2
A number of pyrolysis processes can be represented as a first or-
der reaction. Particularly, the degradation of a series of Ho-HAH
complexes was suggested to be first order [33], therefore we as-
sume n = 1 for the remainder of the present text. The other thermo-
dynamic parameters of activation can be calculated by Eyring
equation [34]:
D
D
D
H ¼ E ꢁ RT
ð7Þ
ð8Þ
ð9Þ
hA
S ¼ Rln
kBT
G ¼
D
H ꢁ T
DS
Table 6
Thermal behavior of metal complexes of (H2o-HAH).
Compound (Molecular mass)
Temp. range, (°C)
Decomposition product(s) loss (Formula mass)
Mass% found (Calcd.)
2 (471.54)
35–115
115–294
294–350
350–498
>498
H2O (18.02)
3.8 (3.8)
H2O + C2H3O2 (77.07)
C5H5N2OS (141.11)
C9H7N2O (159.17)
Residue; NiO (74.71)
16.6 (16.5)
30.0 (29.9)
33.8 (33.8)
15.8 (15.9)
3 (476.15)
7 (447.32)
32–150
150–205
205–345
345–575
>575
H2O (18.02)
3.8 (3.8)
H2O + C2H3O2 (77.07)
C5H5N2OS (141.11)
C9H7N2O (159.17)
Residue; CuO (79.54)
16.2 (16.3)
29.7 (29.6)
33.4 (33.5)
16.7 (16.7)
45–120
120–255
255–360
360–580
>580
2 H2O (36.03)
2H2O (36.03)
C3H3N2S (99.07)
8.1 (8.1)
8. 1 (8.1)
22.0 (22.1)
45.1 (45.0)
16.7 (16.7)
C
11H9N2O2 (201.21)
Residue;CoO (74.93)

K.M. Ibrahim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 133–144
139
Table 7
Kinetic parameters of complexes evaluated by Coats–Redfern equation.
Complex
3
Peak
Mid temp. (K)
Ea (kJ/mol)
A (Sꢁ1
)
D
H (kJ/mol)
D
S (kJ/mol K)
DG (kJ/mol)
1st
378
450
570
753
119.962
170.849
161.280
125.106
3.17576E14
9.69674E14
3.29071E10
6549.09097
116.819
167.107
156.541
118.845
30.7338
38.564
105.202
149.753
184.448
254.053
2nd
3rd
4rd
ꢁ48.960
ꢁ179.559
2
7
1st
340
478
613
715
116.029
106.962
363.608
229.460
6.845E13
113.202
102.988
358.512
223.515
18.855
ꢁ107.255
258.446
ꢁ18.257
ꢁ72.211
ꢁ243.081
ꢁ13.6144
ꢁ61.072
106.791
154.256
200.084
236.569
2nd
3rd
4rd
2.48701E7
4.04323E26
1.65781E12
1st
345
451
606
766
89.616
44.116
193.083
211.620
1.21529E9
1.885
2.45602E12
1.03025E10
86.748
40.366
188.045
205.252
111.661
149.996
196.295
252.033
2nd
3rd
4rd
(A)
(B)
-11.5
lnX n=1
lnX n=1
lnX n=0.66
lnX n=0.33
lnX n=0
-11
-12.0
-12.5
-13.0
-13.5
-14.0
-14.5
-15.0
lnX n=0.66
lnX n=0.33
lnX n=0
lnX n = 0.5
lnX n = 0.5
-12
-13
0.00210 0.00215 0.00220 0.00225 0.00230 0.00235 0.00240
0.0024
0.0026
0.0028
0.0030
0.0032
1000/T
1000/T
(C) -11
(D)
-12.0
lnX n=1
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
-12
-12.5
-13.0
-13.5
-14.0
-14.5
-13
-14
-15
-16
-17
lnX n = 0.5
lnX n = 0.5
0.0015
0.0016
0.0017
0.0018
0.0019
0.0020
0.0021
0.00115 0.00120 0.00125 0.00130 0.00135 0.00140 0.00145 0.00150
1000/T
1000/T
Fig. 1. Coats–Redfern plots of (A) step(1), (B) step(2), (C) step(3) and (D) step(4) of [Cu(Ho-HAH)(OAc)(H2O)]ꢀH2O.
Thermodynamic parameters such as activation energy (Ea), pre-
exponential factor (A), entropy of activation ( S), enthalpy of activa-
tion ( H) and free energy of activation ( G) of decomposition steps
were calculated using Coats–Redfern [32] (see Table 7 and Figs. 1–3).
From the results, the following remarks can be pointed out:
The high values of activation energy (Ea) reveals the high stabil-
ity of such chelates due to their covalent bond character [35].
higher than that of the initial compound, and all the decomposition
steps are non–spontaneous processes. Also, the values of the acti-
D
D
D
vation,
tion stages of a given complex. This is due to increasing the
values of T S significantly from one step to another which over-
rides the values of H [36,37].
The negative values of the entropy (
DG increases significantly for the subsequent decomposi-
D
D
D
S) for the degradation
The positive values of the free energy (
complexes indicates that the free energy of the final residue is
D
G) for the investigated
process indicates slow reaction and the activated complex is more
ordered than the reactants [38].

140
K.M. Ibrahim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 133–144
(A) -11
(B)
lnX n=1
-11
lnX n=1
lnX n=0.66
lnX n=0.33
lnX n=0.66
lnX n=0.33
lnX n=0
-12
lnX n=0
-12
lnX n = 0.5
-13
lnX n = 0.5
-14
-15
-16
-17
-13
-14
0.0017 0.0018 0.0019 0.0020 0.0021 0.0022 0.0023 0.0024 0.0025 0.0026
0.0026
0.0027
0.0028
0.0029
0.0030
0.0031
0.0032
1000/T
1000/T
-12
-10
-11
-12
-13
-14
-15
-16
-17
(C)
(D)
lnX n=1
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
lnX n = 0.5
-13
-14
-15
lnX n = 0.5
-18
0.00130
0.00135
0.00140
1000/T
0.00145
0.00150
0.00150
0.00155
0.00160
0.00165
0.00170
0.00175
1000/T
Fig. 2. Coats–Redfern plots of (A) step(1), (B) step(2), (C) step(3) and (D) step(4) of [Ni(Ho-HAH)(OAc)(H2O)]ꢀH2O.
Electrical conductance
where (M) is the metal concentration and (L) is the ligand concen-
tration (Fig. 5). Different straight lines were obtained with sharp
breaks in presence of ligand representing stoichiometric ratios.
Interaction of Co(II) with (H2o-HAH) in solution
The specific conductance values (Ks) of different concentrations
of Co(II) solution in the absence and in the presence of ligand (E)-
3-(2-(1-(2- hydroxyphenyl)hydrazinyl)-3-oxo-N-(thiazol-2yl)pro-
panamide (H2o-HAH) was measured. From the specific conductance
values (Ks), the molar conductance (Km) values were calculated [39]
according to Eq. (8):
The association constants of Co(II) in the presence of H2o-HAH
The association constant of Co(II) in the presence of ligand could
be calculated by using Eq. (9) for 1:2 asymmetric electrolytes
[40,41].
K02
ð
K0
ꢁ
Km
3SðzÞ
Þ
KA
¼
ð11Þ
ðKs ꢁ Ksol ÞKcell ꢃ 1000
v
4C2m
þ
K
Km
¼
ð10Þ
C
where (Km, K0) are the molar and limiting molar conductance of
metal; Cm is metal concentration; S(Z) is Fuoss–shedlovsky factor
which equal (1) for strong electrolytes [42].
where (Ks) and (Ksolv) are the specific conductance of the solution
and the solvent, respectively; (Kcell = 0.99) is the cell constant and
(C) is the molar concentration of the Co(II) solution.
The Gibbs free energies of association (
DGA) [43,44] were calcu-
lated from the association constant values by Eq. (10):
The concentration dependence on the molar conductance (Km
)
of different Co(II) concentrations in the absence and presence of li-
pffiffiffi
D
GA ¼ ꢁRT ln KA
ð12Þ
gand where studied by plotting (Km) versus ( C) as shown in
Fig. 4. The molar conductance values (Km) decreased linearly by
increasing the metal concentration.
where R is the gas constant and T is the absolute temperature.
Also, the limiting molar conductance (Ko) at infinite dilutions
The formation constants (Kf) for Co(II)–H2o-HAH complexes
were estimated for Co(II) in absence and presence of the ligand
pffiffiffi
by extrapolating the relation between (Km) and ( C) to zero con-
The formation constants (Kf) for Co(II)–ligand complexes can be
calculated for each line in (M/L) relation against (Km) in presence of
ligand by using Eq. (11) [45,46].
centration for each line. In addition, the molar conductance (Km
)
was drawn against the molar ratio (M/L) in the presence of ligand,

K.M. Ibrahim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 133–144
141
-9
-10
-11
-12
-13
(A)
(B)
-11.5
lnX n=1
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
-12.0
-12.5
-13.0
-13.5
-14.0
-14.5
lnX n = 0.5
lnX n = 0.5
0.0019 0.0020 0.0021 0.0022 0.0023 0.0024 0.0025 0.0026
1000/T
0.0027
0.0028
0.0029
0.0030
0.0031
1000/T
(C)
(D)
-12.0
-12.5
-13.0
-13.5
-14.0
-14.5
-15.0
-12.0
-12.5
-13.0
-13.5
-14.0
-14.5
-15.0
lnX n=1
lnX n=0.66
lnX n=0.33
lnX n=0
lnX n=1
lnX n=0.66
lnX n=0.33
lnX n=0
lnX n = 0.5
lnX n = 0.5
0.00145 0.00150 0.00155 0.00160 0.00165 0.00170 0.00175 0.00180
0.00115 0.00120 0.00125 0.00130 0.00135 0.00140 0.00145
1000/T
1000/T
Fig. 3. Coats–Redfern plots of (A) step(1), (B) step(2), (C) step(3) and (D) step(4) of [Co(o-HAH)(H2O)2]ꢀ2H2O.
120
115
110
105
100
95
60
55
50
CoCl2+EtOH
45
40
35
30
25
20
15
10
5
90
85
80
75
70
65
60
0.000
0
0.005
0.010
0.015
0.020
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
M/L
Cm1/2
Fig. 5. The relation between molar conductance (KM) and the molar ratio (M/L) of
Co(II) in presence of (H2o-HAH) in absolute ethanol at 294.15 K.
pffiffiffi
Fig. 4. The relation between molar conductance and ( C) of Co(II) (A) in absence of
H2o-HAH, (B) in presence of H2o-HAH in absolute ethanol at 294.15 K.
titration and (KML) is the molar conductance of the complex. Also,
the Gibbs free energy of complex formation were calculated by
using Eq. (12).
Km
Kobs
ꢁ
Kobs
ꢁ KMLÞ½Lꢄ
Kf ¼
ð13Þ
ð
where (Km) is the molar conductance of the metal before addition
of the ligand, (Kobs) is the molar conductance of solution during
D
Gf ¼ ꢁRT ln K þ f
ð14Þ

142
K.M. Ibrahim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 133–144
Table 8
Association constants and Gibbs free energies of association for Co(II) with (H2o-HAH) in absolute ethanol at 294.15 K.
Km (cm2 ohmꢁ1
)
Cm
Ko
ꢁ
Km
KA
0.923
3.099
7.560
12.219
18.728
28.589
DGA (kJ/mol)
Ko2
(
Ko
ꢁ
Km
)
4C2
þ
Km3
49.200
37.80
30.100
26.400
23.402
20.700
2.439 ꢃ 10ꢁ5
4.762 ꢃ 10ꢁ5
6.976 ꢃ 10ꢁ5
9.091 ꢃ 10ꢁ5
1.111 ꢃ 10ꢁ5
1.142 ꢃ 10ꢁ5
21.80
33.2
40.90
44.60
47.60
50.30
1.099 ꢃ 105
1.67 ꢃ 105
2.016 ꢃ 105
2.248 ꢃ 105
2.399 ꢃ 105
2.536 ꢃ 105
1.191 ꢃ 105
5.401 ꢃ 104
2.727 ꢃ 104
1.839 ꢃ 104
1.281 ꢃ 104
8.869 ꢃ 103
+0.197
ꢁ2.765
ꢁ4.945
ꢁ6.186
ꢁ7.163
ꢁ8.197
Ko = 71 cm2 ohmꢁ1
.
Table 9
Formation constants and Gibbs free energies of formation for 1:2 (M/L) Co(II)-(H2o-HAH) complexes in absolute ethanol at 294.15 K.
Kobs (cm2 ohmꢁ1
)
[L]
(Kobs
ꢁ
KML) [L]
(KM
ꢁ
Kobs
)
Kf
D
Gf (kJ/mol)
49.200
37.800
30.100
9.750 ꢃ 10ꢁ5
9.523 ꢃ 10ꢁ5
9.302 ꢃ 10ꢁ5
3.139 ꢃ 10ꢁ3
1.028 ꢃ 10ꢁ3
2.884 ꢃ 10ꢁ4
39.80
51.2
58.9
1.268 ꢃ 104
4.978 ꢃ 104
2.043 ꢃ 104
ꢁ23.097
ꢁ26.441
ꢁ29.892
KM = 89 cm2 ohmꢁ1
,
KML = 27 cm2 ohmꢁ1
.
Table 10
Formation constants and Gibbs free energies of formation for 1:1 (M/L) Co(II)-(H2o-HAH) complexes in absolute ethanol at 294.15 K.
Kobs (cm2 ohmꢁ1
)
[L]
(Kobs
ꢁ
KML) [L]
(KM
ꢁ
Kobs
)
Kf
DGf (kJ/mol)
26.400
23.402
20.700
19.476
9.091 ꢃ 10ꢁ5
8.888 ꢃ 10ꢁ5
8.697 ꢃ 10ꢁ5
8.511 ꢃ 10ꢁ5
2.745 ꢃ 10ꢁ3
3.913 ꢃ 10ꢁ4
1.478 ꢃ 10ꢁ4
4.051 ꢃ 10ꢁ5
62.600
65.598
68.300
69.524
2.280 ꢃ 104
1.676 ꢃ 105
4.619 ꢃ 105
1.716 ꢃ 106
ꢁ24.532
ꢁ29.409
ꢁ31.887
ꢁ35.096
KM = 89 cm2 ohmꢁ1
,
KML = 19 cm2 ohmꢁ1
.
Table 11
Formation constants and Gibbs free energies of formation for 2:1 (M/L) Co(II)-(H2o-HAH) complexes in absolute ethanol at 294.15 K.
Kobs (cm2 ohmꢁ1
)
[L]
(Kobs
ꢁ
KML) [L]
(KM
ꢁ
Kobs
)
Kf
DGf (kJ/mol)
18.607
17.422
17.000
16.227
8.333 ꢃ 10ꢁ5
8.163 ꢃ 10ꢁ5
8.000 ꢃ 10ꢁ5
7.843 ꢃ 10ꢁ5
2.172 ꢃ 10ꢁ4
1.161 ꢃ 10ꢁ4
8.000 ꢃ 10ꢁ5
1.779 ꢃ 10ꢁ5
70.393
71.580
72.000
72.773
3.240 ꢃ 105
6.166 ꢃ 105
9.000 ꢃ 105
4.089 ꢃ 105
ꢁ31.020
ꢁ32.593
ꢁ33.517
ꢁ37.218
KM = 89 cm2 ohmꢁ1
,
KML = 19 cm2 ohmꢁ1
.
Table 12
Formation constants and Gibbs free energies of formation for 3:1 (M/L) Co(II)-(H2o-HAH) complexes in absolute ethanol at 294.15 K.
Kobs (cm2 ohmꢁ1
)
[L]
(Kobs
ꢁ
KML) [L]
(KM
ꢁ
Kobs
)
Kf
DGf (kJ/mol)
16.467
16.308
15.814
15.033
15.050
7.690 ꢃ 10ꢁ5
7.547 ꢃ 10ꢁ5
7.407 ꢃ 10ꢁ5
7.273 ꢃ 10ꢁ5
7.143 ꢃ 10ꢁ5
1.128 ꢃ 10ꢁ4
9.871 ꢃ 10ꢁ5
6.029 ꢃ 10ꢁ5
2.399 ꢃ 10ꢁ5
3.571 ꢃ 10ꢁ6
72.533
72.692
73.186
73.967
73.950
6.429 ꢃ 105
7.364 ꢃ 105
1.214 ꢃ 106
3.082 ꢃ 106
2.071 ꢃ 106
ꢁ32.695
ꢁ33.027
ꢁ34.248
ꢁ36.527
ꢁ41.184
KM = 89 cm2 ohmꢁ1 KML = 15 cm2 ohmꢁ1
, .
From the results, the following remarks can be pointed out:
Biological activity
– The association free energies evaluated for complexes are spon-
taneous and small (see Table 8), indicating that electrostatic
attraction force.
– Different complexes resulted from the interaction of metal with
ligand which are 1:2, 1:1, 2:1 and 3:1 (M/L) complexes with for-
mation constants and formation Gibbs free energies (see Tables
9–12) of the order:
Diseases caused by microbial infections are a serious menace to
the health of human being and often have connection to some
other diseases when the body system gets debilitated. Developing
antimicrobial drugs and maintaining their potency in opposition to
resistance by different classes of microorganisms as well as a broad
spectrum of antibacterial and antifungal activities are some of the
major concerns of research in this area.
Kf (3:1) > Kf (2:1) > Kf (1:1) > Kf (1:2) for (M/L), and
Minimum inhibitory concentration (MIC) [47,48] was deter-
mined for each of the active compounds. All of the tested com-
pounds showed a remarkable biological activity against different
types of Gram-positive and Gram-negative bacteria (Clostridium
sp. and E. coli) and against fungi species (Stemphylium sp. and
D
Gf (3:1) > DGf (2:1) > DGf (1:1) > DGf (1:2).
– The formation constants and formation Gibbs free energies
increase by increasing the metal concentration which favors
spontaneous processes.

K.M. Ibrahim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 133–144
143
Fig. 6. Effect of ligand and its metal complexes toward (A) Aspergillus sp., (B) Stemphylium sp. (C) E. Coli and (D) Clostridium sp.
Aspergillus sp.) (Fig. 6). On comparing the biological activity of the
ligand and its metal complexes with the standard (Miconazole and
Ampicillin), from the results, the Ni(II), Co(II), Cu(II), Cd(II), Zn(II),
Pd(II) and U(VI)O2 metal complexes shown potential antimicrobial
activities against all the bacterial and fungal strains. Amongst all
the compounds tested, Pd(Ho-HAH)(H2O)]ꢀH2O complex demon-
strated the most potent antibacterial and antifungal activity
(90%) at the higher concentration of 1.5 mg/ml [49]. In general all
the metal complexes possess higher antimicrobial activity than
the ligand and this may be due to the change in structure due to
coordination and chelating tends to make metal complexes act as
more powerful and potent bactereostatic agents, thus inhibiting
the growth of the microorganisms. Moreover, coordination reduces
the polarity of the metal ion mainly because of the partial sharing

144
K.M. Ibrahim et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 133–144
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