Spectral, magnetic, thermal, molecular modelling, ESR studies and antimicrobial activity of (E)-3-(2-(2-hydroxybenzylidene) hydrazinyl)-3-oxo- n(thiazole-2-yl)propanamide complexes

Article abstract of DOI:10.1016/j.molstruc.2011.06.050

(E)-3-(2-(2-hydroxybenzylidene)hydrazinyl)-3-oxo-n(thiazole-2-yl) propane-mide (H₂L) has been prepared and its structure confirmed by elemental analysis, IR and ¹HNMR spectroscopy. It has been used to produce diverse complexes with Ni(II), Co(II) and Cu(II) ions. The complexes obtained have been investigated by thermal analysis, spectral studies (IR, UV-visible, ESR), and magnetic measurements. IR spectra suggest that the H ₂L acts as a bidentate ligand coordinating via (CN)₁ and (OH)_phenolic or deprotonated enolized carbonyl oxygen (CO) ₁. The electronic spectra of the complexes and their magnetic moments provide information about geometries. The room temperature solid state ESR spectra of the Cu(II) complexes show d_{x2-y 2} as a ground state, suggesting tetragonally distorted octahedral or square-planar geometries around Cu(II) centre. The molar conductance measurements proved that the complexes are non-electrolytes. The bond length, bond angle, HOMO, LUMO, dipole moment and charges on the atoms have been calculated to confirm the geometry of the ligand and the investigated complexes. Also, thermal properties and decomposition kinetics of all compounds are investigated. The interpretation, mathematical analysis and evaluation of kinetic parameters (Ea, A, ΔH, ΔS and ΔG) of all thermal decomposition stages have been evaluated using Coats-Redfern and Horowitz-Metzger methods. Finally, the antimicrobial activity has been tested.

Full text of DOI:10.1016/j.molstruc.2011.06.050

Journal of Molecular Structure 1002 (2011) 76–85
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Journal of Molecular Structure
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Spectral, magnetic, thermal, molecular modelling, ESR studies
and antimicrobial activity of (E)-3-(2-(2-hydroxybenzylidene)
hydrazinyl)-3-oxo-n(thiazole-2-yl)propanamide complexes
R.R. Zaky a, T.A. Yousef b,
⇑
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
a r t i c l e i n f o
a b s t r a c t
Article history:
(E)-3-(2-(2-hydroxybenzylidene)hydrazinyl)-3-oxo-n(thiazole-2-yl) propane-mide (H2L) has been
prepared and its structure confirmed by elemental analysis, IR and 1HNMR spectroscopy. It has been used
to produce diverse complexes with Ni(II), Co(II) and Cu(II) ions. The complexes obtained have been inves-
tigated by thermal analysis, spectral studies (IR, UV–visible, ESR), and magnetic measurements. IR spectra
suggest that the H2L acts as a bidentate ligand coordinating via (C@N)1 and (OH)phenolic or deprotonated
enolized carbonyl oxygen (@CAOA)1. The electronic spectra of the complexes and their magnetic
moments provide information about geometries. The room temperature solid state ESR spectra of the
Cu(II) complexes show dx2ꢀy2 as a ground state, suggesting tetragonally distorted octahedral or square-
planar geometries around Cu(II) centre. The molar conductance measurements proved that the
complexes are non-electrolytes. The bond length, bond angle, HOMO, LUMO, dipole moment and charges
on the atoms have been calculated to confirm the geometry of the ligand and the investigated complexes.
Also, thermal properties and decomposition kinetics of all compounds are investigated. The interpreta-
Received 18 March 2011
Received in revised form 29 June 2011
Accepted 30 June 2011
Available online 12 July 2011
Keywords:
Hydrazone complexes
ESR
Thermal analysis
Antimicrobial activity
tion, mathematical analysis and evaluation of kinetic parameters (Ea, A,
DH, DS and DG) of all thermal
decomposition stages have been evaluated using Coats–Redfern and Horowitz–Metzger methods. Finally,
the antimicrobial activity has been tested.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
the ligand individually. Therefore, we report here the synthesis
and characterization of Ni(II), Co(II) and Cu(II) complexes with
The coordination chemistry of substituted hydrazones has
received much impetus by the remarkable anticancer, amoebicidal,
antibacterial, antimicrobial and antileukaemic activities exhibited
by these compounds which can be related to their metal complex-
ing abilities [1–3]. Aroylhydrazone possess strong pharmacological
properties and may inhibit many enzymatic reactions catalysed by
transition metals. The chemical and pharmacological properties of
aroylhydrazone have been extensively investigated owing to their
potential applications as antineoplastic, antiviral, antiinflamma-
tory and antitumor agents [4–6]. Also, hydrazones have been used
for the analytical determination of wide variety of metal ions [7–9].
Hydrazones have interesting ligation properties due to presence of
several coordination sites. The metal complexes formed by the
combination of transition metal ion with a potent acylhydrazone
ligand should be more biologically active than the metal salts or
(E)-3-(2-(2-hydroxybenzylidene)hydrazinyl)-3-oxo-n(thiazole-2-
yl)propanamide (H2L). The antifungal and antibacterial properties
of the ligand and its complexes were tested.
2. Experimental
2.1. Apparatus and reagents
The IR absorption spectra were recorded on a Mattson 5000
FTIR Spectrophotometer. The electronic spectra were measured
on a Unicam UV/vis Spectrometer UV2. Thermogravimetric analysis
was performed using an automatic recording thermobalance type
(951 DuPont instrument). Samples were subjected to heat on a rate
of 10 °C/min (25–800 °C) in N2. 1H NMR spectra for H2L and
diamagnetic complexes, in DMSO, were recorded on EM-390
(200 MHz) Spectrometer. Carbon and hydrogen content for the
ligand and its complexes was determined at the Microanalytical
Unit, Mansoura University, Egypt. Co(II), Ni(II), Cu(II), Clꢀ and
⇑
Corresponding author. Tel.: +20 122247712.
E-mail address: drroka78@yahoo.com (T.A. Yousef).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.06.050

R.R. Zaky, T.A. Yousef / Journal of Molecular Structure 1002 (2011) 76–85
77
SO24ꢀ contents in the complexes were determined by the well
known standard methods [10]. ESR spectra were 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 4 scans with a 10-fold increase in the
receiver gain. A powder spectrum was obtained in a 2 mm quartz
capillary at room temperature. All metal salts used were pure
(Fluka, Aldrich or Merck).
off, washed with EtOH and Et2O and recrystallized from EtOH
(M.p.: 225 °C; yield 90%). The purity of the compound was checked
by TLC.
2.3. Preparation of complexes
The complexes were prepared by mixing equimolar amounts of
H2L with ethanolic and/or aqueous solution of chloride salt of
Cu(II); acetate salt of Ni(II), Co(II) and Cu(II) and sulphate salt of
Cu(II) (Scheme 1). The reaction mixture was heated under reflux
on a water bath for 1–3 h. The isolated complexes were washed
several times with water, ethanol and finally with diethyl ether
and the pure complexes thus obtained were dried in a desiccator
over anhydrous 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.
2.2. Preparation of the ligand
(E)-3-(2-(2-hydroxybenzylidene)hydrazinyl)-3-oxo-n(thiazole-
2yl)propan-mide (Scheme 1) was prepared by heating a mixture of
3-hydrazinyl-oxo-N-(thiazole-2-) propanamide (0.01 mol; 2.00 g)
and salicyladehyde (0.01 mol; 1.36 g) under reflux in absolute
ethanol for 3 h. On heating, white crystals were formed, filtered
Scheme 1. The outline of the synthesis of ligand and its complexes.

78
R.R. Zaky, T.A. Yousef / Journal of Molecular Structure 1002 (2011) 76–85
2.4. Molecular modelling
On comparison of the spectrum of the ligand with that of
[Ni(H2L)(OAc)2]ꢁH2O, [Co(H2L)(OAc)2]ꢁ2H2O and [Cu(H2L)Cl2]ꢁH2O
complexes, we found that there are negative shift of both (OH)
and (C@N)1 vibrations. While, the (C@O)1, (C@O)2, (C@N)2,
(N1H) and (N2H) vibrations remain at more or less at the same
position Table 2, which indicates that they does not participate
in coordination to the metal ion. So, the H2L acts as a neutral biden-
tate coordinating via (OH) and azomethine nitrogen (C@N)1 atoms.
Also, new bands were observed in 518–521 and 460–470 cmꢀ1 re-
An attempt to gain a better insight on the molecular structure of
the ligand and its complexes, geometry optimization and
conformational analysis has been performed by the use of MM+
force-field as implemented in hyperchem 8.0 [11]. The low lying
obtained from MM+ was then optimized at PM3 using the Polak–
Ribiere algorithm in RHF-SCF, set to terminate at an RMS gradient
m
m
m
m
m
m
m
of 0.01 kcal molꢀ1
.
gions which assigned to m(MAO) and m(MAN) [16], respectively.
Moreover, the IR spectra of [Cu(HL)2(H2O)2] and [Cu(HL)(OAc)]
complexes reflect that the H2L acts as a monoanionic bidentate
ligand coordinating via the deprotonated enolized carbonyl oxygen
(@CAOꢀ)1 and azomethine nitrogen (C@N)1. This mode of
complexation is supported by the following observations: (i) the
2.5. Antimicrobial activity
The compounds, Gentamycin and Colitrimazole were dissolved
in DMSO at concentration of 1 lg/ml. The twofold dilutions of the
solution were prepared. The microorganism suspensions [12] at
10 CFU/ml (colony forming unit/ml) concentration were inoculated
to the corresponding wells. The plates were incubated at 36 °C for
24 and 48 h for the bacteria and Candida albicans, respectively. The
MIC values were determined as the lowest concentration that
completely inhibited visible growth of the microorganism as
detected by unaided eye.
shift of
m
(C@N)1 to lower wave numbers, (ii) the disappearance
(C@O)1 and (N1H) with simultaneous appearance of
(CAO)1(eno-
(C@N), respectively and (iii) the appearance of new bands
at 523 and 478 cmꢀ1 which may be attributed to
(CuAO) and
(CuAN), respectively [18].
In metal acetate complexes, the acetate group coordinates to
the metal ions in a bidentate manner where the difference
between the two acetate bands is
6 180 cmꢀ1 [19]. Also, the
bands of coordinated water observed at 854 and 595 cmꢀ1, are
assigned to r(H2O) and w(H2O), respectively [19]. Moreover,
of both
m
m
new band at 1125 and 1614 cmꢀ1 which assignable to
m
lic) and
m
m
m
3. Results and discussion
D
m
The isolated solid complexes are stable in air and easily soluble in
DMF and DMSO only. All complexes decompose on heating at
>300 °C. The molar conductance value, in DMSO, is 3–6 Xꢀ1
cm2 molꢀ1 indicating that the all complexes are non-electrolytes
Table 1.
q
q
strong evidence for the presence or absence of water of crystalliza-
tion and/or coordinated water supported by the thermogram of all
complexes.
3.2. Electronic spectra and magnetic moment measurements
3.1. IR and 1H NMR spectral studies
The electronic spectrum of [Ni(H2L)(OAc)2]ꢁH2O complex shows
two bands at 13,605 and 22,727 cmꢀ1 attributed to 3A2g ? 3T1g(F)
and 3A2g ? 3T1g(P) transitions, respectively, in an octahedral geom-
The 1H NMR spectrum of H2L (Fig. 1) in d6-DMSO shows three
signals at 12.89, 11.20 and 13.06 ppm assignable to the protons
of (N1H), (N2H) and (OH)phenolic, respectively. 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 multiple signals observed in the
6.96–7.78 ppm region are assigned to the aromatic and (AN@CAH)
protons. The signal at d 3.69 ppm is assigned to the protons of
methylene group (ACH2A). The infrared spectrum of H2L exhibits
characteristic bands at 1692, 1649, 1615, 1566, 3215, 3153 and
etry [20]. The calculated values of Dq, B, b and m2/m1 lie in the range
reported for an octahedral structure Table 3 [20]. The position of m1
(8146 cmꢀ1) is calculated theoretically. The value of the magnetic
moment (
leff. = 3.13 B.M.) is additional evidence for an octahedral
geometry.
The electronic spectrum of [Co(H2L)(OAc)2]ꢁ2H2O complex
exhibits two bands at 14,065 and 17,241 cmꢀ1 attributed to
4T1g ? 4A2g(F) and 4T1g ? 4T1g(P) transitions, respectively, in an
3425 cmꢀ1 assigned to
[14], (N1H), (N2H) [15] and (OH) [16] vibrations, respectively
m
(C@O)1,
m
(C@O)2 [13],
m(C@N)1,
m
(C@N)2
octahedral configuration [20]. The calculated Dq, B, b and m2/m1 val-
m
m
ues are in the range reported for an octahedral environment
around Co(II) complexes. The position of m1 (6541 cmꢀ1) is calcu-
lated theoretically. Also, the value of the magnetic moment (4.97
B.M.) is additional evidence for an octahedral geometry around
the Co(II) ion.
Table 2. The appearance of (OH) as a broad band at lower wave-
number and the two weak broad bands in the 1900–2080 and
2150–2230 cmꢀ1 regions suggest intramolecular hydrogen
bonding (OAHꢁ ꢁ ꢁO) [17].
Table 1
Analytical and physical data of H2L and its metal complexes.
Kmꢂ
Compound empirical formula (F.wt.)
Colour
MP (°C)
Yield (%)
%Found (Calcd)
C
H
M
H2L
White
Green
Green
Green
Green
Green
225
90
80
85
80
78
82
51.42
(51.30)
40.84
(40.91)
39.61
(39.46)
34.32
(34.15)
44.24
(44.18)
42.28
4.11
(3.97)
4.35
(4.04)
4.40
(4.28)
3.15
(3.09)
3.80
(3.71)
3.36
–
–
–
4
4
6
3
4
C
13H12O3N4S (304.3)
[Ni(H2L)(OAc)2]ꢁH2O
NiC17H20O8N4S (499.1)
[Co(H2L)(OAc)2]ꢁ2H2O
CoC17H22O9N4S (517.3)
[Cu(H2L)Cl2]ꢁH2O
>300
>300
>300
>300
>300
11.82
(11.76)
11.36
(11.39)
14.01
(13.91)
9.01
(8.99)
14.94
(14.92)
CuC13H14O4N4SCl2 (456.7)
[Cu(HL)2(H2O)2]
CuC26H26O8N8S2 (706.1)
[Cu(HL)(OAc)]
CuC15H14O5N4S (425.9)
(42.30)
(3.32

R.R. Zaky, T.A. Yousef / Journal of Molecular Structure 1002 (2011) 76–85
79
Fig. 1. 1H NMR spectrum of (E)-3-(2-(2-hydroxybenzylidene)hydrazinyl)-3-oxo-n(thiazole-2-yl) propanamide (H2L).
Table 2
Most important IR spectral bands of H2L and its metal complexes in cmꢀ1
.
Compound
m(OH)
m
(N1H)
m
(N2H)
m
(C@O)1
m
(C@O)2
m
(C@N)1
m
(C@N)2
m
(CH2)
m
(CAO)1
m
(C@Nꢂ)2
m
(MAO)
m
(MAN)
H2L
3425
3385
3380
3385
3419
3428
3215
3208
3209
3217
3261
3275
3153
3174
3150
3116
–
1692
1691
1692
1692
1700
1701
1649
1648
1646
1646
–
1615
1606
1601
1606
1595
1596
1566
1581
1574
1570
1566
1574
2933
2935
2937
2937
2933
2934
–
–
–
–
1125
1125
–
–
–
–
1614
1614
–
–
[Ni(H2L)(OAc)2]ꢁH2O
[Co(H2L)(OAc)2]ꢁ2H2O
[Cu(H2L)Cl2]ꢁH2O
[Cu(HL)2(H2O)2]
[Cu(HL)(OAc)]
521
521
519
523
523
460
470
472
478
478
–
–
Table 3
Magnetic moments, electronic spectra and ligand field parameters of metal complexes of H2L.
Complex
leff (B.M.)
Band position (cmꢀ1
)
Dq (cmꢀ1
)
B (cmꢀ1
)
b
m2/m1
[Ni(H2L)(OAc)2]ꢁH2O
[Co(H2L)(OAc)2]ꢁ2H2O
[Cu(H2L)Cl2]ꢁH2O
[Cu(HL)2(H2O)2]
3.13
4.97
1.92
1.98
2.01
13,605; 22,727
14,065; 17,241
14,709
14,749; 16,667
14,285
903
763
–
–
–
813
803
–
–
–
0.78
0.83
–
–
–
1.67
2.15
–
–
–
[Cu(HL)(OAc)]
Table 4
ESR data of the copper (II) complexes at room temperature.
expression, G = (g|| ꢀ 2)/(g\ ꢀ 2) = 4, where G is the exchange inter-
action parameter. According to Hathaway and Billing [23], if the
value of G is greater than 4, the exchange interaction between
Cu(II) centres in the solid state is negligible, whereas when is less
than 4, a considerable exchange interaction is indicated in the solid
Complex
g‚
g\
A‚ ꢃ 10ꢀ4 (cmꢀ1
)
G
a2
b2
[Cu(HL)2(H2O)2]
[Cu(H2L)Cl2]ꢁH2O
[Cu(HL)(OAc)]
2.23
2.26
2.20
2.05
2.08
2.06
160
174
168
4.6
3.2
3.3
0.75
0.81
0.37
0.6
0.70
0.58
complex. The calculated
G
values for [Cu(HL)2(H2O)2],
[Cu(H2L)Cl2]ꢁH2O and [Cu(HL)(OAc)] complexes are 4.5, 4.4 and
4.2, respectively (Fig. 2), suggesting that there are no copper–cop-
per exchange interactions.
The Cu(II) complexes have magnetic moment values (1.92–2.01
B. M.) which correspond to those reported for d9-systems. The
electronic spectra of [Cu(H2L)Cl2]ꢁH2O and [Cu(HL)(OAc)]
complexes exhibit a broad band with a maximum at 14,709 and
14,285 cmꢀ1, respectively, assigned to 2B1g ? 2A1g transition as
reported for square planar Cu(II) complexes [21]. The electronic
spectrum of [Cu(HL)2(H2O)2] complex shows a broad band at
16,667 cmꢀ1 with a shoulder at 14,749 cmꢀ1 which may assign to
2B1g ? 2Eg and 2Eg ? 2A1g transitions, respectively, in a tetrago-
nally distorted octahedral configuration [21].
The tendency of A|| to decrease with an increase of g|| is an index
of an increase of the tetrahedral distortion in the coordination
sphere of copper [24]. In order to quantify the degree of distortion
of the Cu(II) complexes, we selected the f factor g||/A|| obtained
from the ESR spectra. Although the f factor, which is considered
as an empirical index of tetrahedral distortion [25]. Its value ranges
between 105 and 135 for square planar complexes, depending on
the nature of the coordinated atoms. In the presence of a tetrahe-
drally distorted structure the values can be much larger [26]. For
[Cu(H2L)Cl2]ꢁH2O and [Cu(HL)(OAc)] complexes the g||/A|| quotient
is 129 and 130, respectively, evidence in support of the square
planar geometry with no appreciable tetrahedral distortion. But,
the ratio g||/A|| for the complex [Cu(HL)2(H2O)2] is 139 demonstrat-
ing the presence of significant dihedral angle distortion in the
xy-plane and indicating a tetrahedral distortion from square planar
geometry and the results are consistent with distorted octahedral
geometry around the copper site.
3.3. ESR spectra
The solid state ESR spectra of some complexes exhibit axially
symmetric g-tensor parameters with g‚ 6 g? > 2:0023 indicating
that the copper site has a dx2ꢀy2 ground-state characteristic of
tetrahedral, square planar or octahedral stereochemistry [22].
The spin Hamiltonian parameters of these complexes were calcu-
lated Table 4. In axial symmetry the g-values are related by the
Molecular orbital coefficients,
a r-bonding)
2 (covalent in-plane
and b2 (covalent in-plane
p-bonding) were calculated [27–30]:

80
R.R. Zaky, T.A. Yousef / Journal of Molecular Structure 1002 (2011) 76–85
8000
6000
4000
2000
0
bly covalent and are consistent with very strong in-plane
ing in this complex, but in [Cu(H2L)Cl2]ꢁH2O and [Cu(HL)(OAc)]
complexes, the results indicate that the in-plane -bonding and
in-plane -bonding are appreciably ionic. These results are antici-
p-bond-
c
r
p
b
pated because there are appropriate ligand orbitals to combine
with the dxy orbital of the Cu(II) ion. For the square planar geome-
try complexes, the lower values of b2 compared to 2 indicate that
a
a
the in-plane
-bonding. These data are well consistent with other reported
values [31,32].
p-bonding is more covalent than the in-plane
r
-2000
-4000
-6000
-8000
-10000
3.4. Thermal analysis
The TG of the isolated complexes was taken as a proof for the
existing of water molecules as well as the anions to be coordina-
tion sphere. The water of crystallization lost in 30–110 °C regions
while those coordinated lost at 235 °C. The complexes show
thermal stability rather than the ligand where the beginning of
its decomposition shifts to higher temperature (246–700 °C). In
general, all complexes are thermally stable; [Cu(HL)2(H2O)2]
is the highest one. It is thermally stable up to 238 °C above which
the dehydration begins. In the temperature range 238–350 °C, the
TG curve displays 45.1% weight loss which could be ascribed to the
elimination of the two coordinated water molecules [33] as well as
the two loosely bound (C5H5ON2S) fragments. The second weight
loss stage (350–446 °C) is due to decomposition of the two organic
portions (2C6H5O). The final weight loss of 34.3% ending at 600 °C,
is largely attributed to complete decomposition of the remaining
more two tightly bound fragment (2C2HN2) as well as the release
of half oxygen molecule. The remaining final fired product is
CuO, representing 11.2%. The data of the different decomposition
steps of all isolated complexes are shown in Table 5.
2500
3000
3500
4000
4500
G (Gauss)
Fig. 2. Room temperature X-band ESR spectra of (a) [Cu(H2L)Cl2]ꢁH2O (b)
[Cu(HL)(OAc)] and (c) [Cu(HL)2(H2O)2].
ꢀ
ꢁ
A‚
0:036
3ðg? ꢀ 2:0023Þ
a2
¼
þ ðg‚2:0023Þ þ
þ 0:04
7
ðg‚ ꢀ 2:0023ÞE
ꢀ8ka2
b2 ¼
where k = 828 cmꢀ1 for the free ion and E is the 2B1g ? 2A1g
transition.
As a measure of the covalency of the in-plane
indicates complete ionic character, whereas
r-bonding a
2 = 1
a
2 = 0.5 denotes 100%
covalent bonding, with the assumption of negligibly small values
of the overlap integral. The b2 parameter gives an indication of
the covalency of the in-plane
p
-bonding. The smaller the b2, the
3.5. Kinetic data
larger the covalency of the bonding.
The values of a2 and b2 for [Cu(HL)2(H2O)2] complex indicate
The kinetic and thermodynamic parameters of thermal degra-
dation process have been calculated using Coats–Redfern and
that the in-plane
r-bonding and in-plane p-bonding are apprecia-
Table 5
Thermal behaviour of metal complexes of H2L.
Complex (M.wt.)
Temp. range (°C)
Decomp. prod. (F.wt.)
Wt. loss (%)
Found
Calcd
[Ni(H2L)(OAc)2]ꢁH2O (499.1)
[Co(H2L)(OAc)2]ꢁ2H2O (517.3)
[Cu(H2L)Cl2]ꢁH2O (456.7)
35–105
145–246
246–393
393–700
>700
H2O (18.015)
2C2H3O2 (118.092)
C3H4N2S (100.136)
3.8
23.6
20.0
37.5
15.1
3.6
23.7
20.1
37.6
15.0
C10H8O2N2 (188.176)
Residue, NiO (74.709)
32–109
139–284
284–398
398–595
>595
2H2O (36.032)
2C2H3O2 (118.092)
C3H4N2S (100.136)
6.9
22.7
19.3
36.6
14.5
7.0
22.8
19.4
36.4
14.4
C10H8O2N2 (188.176)
Residue, CoO (74.929)
30–110
110–255
255–365
365–675
>675
H2O (18.015)
Cl2 (70.906)
C3H4N2S (100.136)
3.9
15.5
22.0
41.2
17.4
4.0
15.5
21.9
41.2
17.4
C10H8O2N2 (188.176)
Residue, CuO (79.540)
[Cu(HL)2(H2O)2] (706.1)
[Cu(HL)(OAc)] (425.9)
238–350
350–446
446–600
>600
2H2O + 2(C5H5ON2S)(318.119)
2C6H5O (186.089)
2C2HN2+½O2 (122.018)
Residue, CuO (79.540)
45.1
26.4
17.3
11.2
45.1
26.4
17.3
11.2
160–330
330–380
380–510
>510
C2H3O2 (59.054)
13.9
33.1
34.3
18.7
13.9
33.2
34.2
18.7
C5H5ON2S (141.045)
C8H6N2+½O2 (146.156)
Residue, CuO (79.540)

R.R. Zaky, T.A. Yousef / Journal of Molecular Structure 1002 (2011) 76–85
81
Table 6
Kinetic parameters of complexes evaluated by Coats–Redfern equation.
Complex
Peak
Mid temp (K)
Ea (kJ/mol)
A (Sꢀ1
)
D
Hꢂ (kJ/mol)
D
Sꢂ (kJ/mol K)
D
Gꢂ (kJ/mol)
[Co(H2L)(OAc)2]ꢁ2H2O
1st
344
484
616
767
444.9
27.0
476.7
174.4
7.2862E7
1.4872Eꢀ5
20887.45
3.4683E7
442.1
22.9
471.5
168.1
ꢀ0.0955
ꢀ0.3414
ꢀ0.1682
ꢀ0.1084
474.9
188.2
575.2
251.2
2nd
3rd
4rd
[Ni(H2L)(OAc)2]ꢁH2O
1st
343
468
591
823
30.9
72.4
131.4
648.3
0.30654
53.23621
7.4560E6
28.1
68.6
126.5
641.5
ꢀ0.2559
ꢀ0.2156
ꢀ0.1190
ꢀ0.1505
115.9
169.5
196.9
765.4
2nd
3rd
4th
233861.8
[Cu(HL)2(H2O)2]
[Cu(HL)(OAc)]
1st
2nd
563
683
108.9
198.6
52210.3
145.9
104.3
192.9
ꢀ0.1598
ꢀ0.2103
ꢀ0.2327
ꢀ0.0072
ꢀ0.2143
194.3
336.6
1st
2nd
3rd
529
628
710
65.9
215.0
98.3
7.66498
5.4965E12
94.46723
61.6
209.8
92.4
184.7
214.3
244.6
[Cu(H2L)Cl2]ꢁH2O
1st
360
460
575
742
45.2
41.3
126.6
88.2
61.00084
0.04279
1.8189E6
8.5545
42.2
37.5
121.8
82.1
ꢀ0.2123
ꢀ0.2747
ꢀ0.1305
ꢀ0.2346
118.7
163.9
196.9
256.2
2nd
3rd
4rd
Table 7
Kinetic parameters of complexes evaluated by Horowitz–Metzger equation.
Complex
Peak
Mid temp (K)
Ea (kJ/mol)
A (Sꢀ1
)
D
Hꢂ (kJ/mol)
D
Sꢂ (kJ/mol K)
D
Gꢂ (kJ/mol)
[Co(H2L)(OAc)2]ꢁ2H2O
1st
344
484
616
767
444.7
27.5
476.7
174.3
7.3729E7
1.5191Eꢀ5
19667.38
441.8
23.5
471.6
167.9
ꢀ0.0954
ꢀ0.3411
ꢀ0.1687
ꢀ0.1083
474.6
188.6
251.0
251.0
2nd
3rd
4rd
3.4931E7
[Ni(H2L)(OAc)2]ꢁH2O
1st
343
468
591
823
30.3
72.5
131.4
648.5
0.30516
55.64061
6.8283E6
27.5
68.6
126.5
641.7
ꢀ0.2559
ꢀ0.2152
ꢀ0.1197
ꢀ0.1504
115.2
169.3
197.3
765.5
2nd
3rd
4th
237173.6
[Cu(HL)2(H2O)2]
[Cu(HL)(OAc)]
1st
2nd
563
683
108.6
198.8
57356.8
145.1
103.9
193.1
ꢀ0.1591
ꢀ0.2104
ꢀ0.2323
ꢀ0.0072
ꢀ0.2146
193.5
336.8
1st
2nd
3rd
529
628
710
65.8
215.3
98.6
8.00962
5.485E12
90.30893
61.4
210.0
92.7
184.4
214.6
245.1
[Cu(H2L)Cl2]ꢁH2O
1st
360
460
575
742
45.6
41.3
126.9
88.3
56.94588
0.04366
1.8612E6
8.46765
42.6
37.5
122.1
82.1
ꢀ0.2128
ꢀ0.2745
ꢀ0.1303
ꢀ0.2347
119.3
163.8
197.0
256.3
2nd
3rd
4rd
remainder of the present text. The other thermodynamic parame-
ters of activation can be calculated by Eyring equation [37]:
Horowitz–Metzger models [34,35]. Coats–Redfern relation is as
follows:
ꢂ
ꢃ
ꢀ
ꢁ
D
D
D
H ¼ E ꢀ RT
ð3Þ
ð4Þ
ð5Þ
lnð1 ꢀ
a
Þ
AR
bE
E
RT
ln ꢀ
¼ ln
ꢀ
ð1Þ
T2
hA
S ¼ R ln
kBT
where
defined by:
a
represents the fraction of sample decomposed at time t,
woꢀwt
S ¼
D
H ꢀ T
DS
a
¼
, wo, wt and w are the weight of the sample
1
woꢀwpropto
before the degradation, 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
Thermodynamic parameters such as activation energy (Ea), pre-
exponential factor (A), entropy of activation ( S), enthalpy of
activation ( H) and free energy of activation ( G) of decomposi-
tion steps were calculated using Coats–Redfern [34] and
Horowitz–Metzger [35] methods Tables 6 and 7. In both methods,
the lift side of Eqs. (3) and (4) are plotted against 1/T and h, respec-
tively (Figs. 3 and 4). From the results, the following remarks can
be pointed out:
D
D
D
lnð1ꢀ
a
pre-exponential factor, respectively. A plot of ln½ꢀ
Þꢄ versus 1/
2
T gives a straight line whose slope (E/R) and the prTe-exponential
factor (A) can be determined from the intercept.The Horowitz–
Metzger relation [35] used to evaluate the degradation kinetics is:
Eh
RT2s
ln½ꢀ lnð1 ꢀ
a
Þꢄ ¼
ð2Þ
- The high values of the energy of activation, E of the complexes
reveals the high stability of such chelates due to their covalent
bond character [38].
where h = T ꢀ Ts, Ts is the DTG peak temperature, T is the tempera-
ture corresponding to weight loss Wt. A straight line should be
E
- The positive sign of
DG for the investigated complexes reveals
observed between ln½ꢀ lnð1 ꢀ
a
Þꢄ and h with a slope of RT2. A number
s
that the free energy of the final residue is higher than that of
the initial compound, and all the decomposition steps are
non-spontaneous processes. Also, the values of the activation,
of pyrolysis processes can be represented as a first order reaction.
Particularly, the degradation of a series of H2L complexes was
suggested to be first order [36], therefore we assume n = 1 for the

82
R.R. Zaky, T.A. Yousef / Journal of Molecular Structure 1002 (2011) 76–85
lnX n=1
lnX n=1
lnX n=0.66
lnX n=0.66
lnX n=0.33
lnX n=0
(A)
(B)
lnX n=0.33
lnX n=0
-11
-12
-13
-14
lnX n = 0.5
lnX n = 0.5
-12
-13
-14
0.0018
0.0019
0.0020
0.0026
0.0027
0.0028
0.0029
1000/T
1000/T
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
-10
-11
-12
-13
-11
-12
-13
-14
(C)
(D)
lnX n = 0.5
lnX n = 0.5
0.0016
0.0017
0.0018
0.0027
0.0028
0.0029
0.0030
0.0031
1000/T
1000/T
lnX n=1
lnX n=0.66
lnX n=0.33
lnX n=0
(E)
lnX n = 0.5
-11
-12
0.0026
0.0027
0.0028
0.0029
1000/T
0.0030
0.0031
Fig. 3. Coats–Redfern plots of (A) [Co(H2L)(OAc)2]ꢁ2H2O, (B) [Cu(HL)(OAc)], (C) [Cu(H2L)Cl2]ꢁH2O (D) [Cu(HL)2(H2O)2] and (E)[Ni(H2L)(OAc)2]ꢁH2O.
D
G increases significantly for the subsequent decomposition
stages of a given complex. This is due to increasing the values
of T S significantly from one step to another which overrides
the values of H [39–41].
- The negative values of S for the degradation process indicates
ular orbitals (LUMO) of each ligand and its complexes have been cal-
culatedandpresentedinTables(SupplementaryMaterials)(1S–7S).
The lower HOMO energy values show that molecules donating
electron ability is the weaker. On contrary, the higher HOMO
energy implies that the molecule is a good electron donor. LUMO
energy presents the ability of a molecule receiving electron [42].
Analysis of the data in Tables 1S–7S (Supplementary Materials)
calculated for the bond lengths and angles for the bond, one can
conclude the following remarks:
D
D
D
more ordered activated complex than the reactants or the reac-
tion is slow [37].
3.6. Molecular modelling
1. The C(8)AN(6) bond length becomes slightly longer in complex
as the coordination takes place via N atoms of ACANAN@CA
group that is formed on deprotonation of OH group in [Cu(H-
L)(OAc)] complex [43].
The molecular numbering of ligand and its metal complexes are
shown in Figs. 5–7. Some parameters like total energy, binding
energy, electronic energy, heat of formation, dipole moment, highest
occupied molecular orbitals (HOMO) and lowest unoccupied molec-

R.R. Zaky, T.A. Yousef / Journal of Molecular Structure 1002 (2011) 76–85
83
lnX n=1
1
0
lnX n=1
lnX n=0.66
lnX n=0.33
lnX n=0
lnX n = 0.5
(A)
lnX n=0.66
lnX n=0.33
lnX n=0
(B)
1
lnX n = 0.5
0
-1
-2
-1
1
-20
-10
0
10
20
30
-20
-10
0
10
T-Ts
T-Ts
lnX n=1
lnX n=1
lnX n=0.66
lnX n=0.33
lnX n=0
(C)
(D)
2
1
lnX n=0.66
lnX n=0.33
lnX n=0
lnX n = 0.5
lnX n = 0.5
0
0
-1
-1
0
10
20
30
40
-20
-10
0
T-Ts
T-Ts
lnX n=1
0.5
0.0
(E)
lnX n=0.66
lnX n=0.33
lnX n=0
lnX n = 0.5
-0.5
-1.0
-20
-10
0
10
20
T-Ts
Fig. 4. Horowitz–Metzger plots of (A) [Co(H2L)(OAc)2]ꢁ2H2O, (B) [Cu(HL)(OAc)], (C) [Cu(H2L)Cl2]ꢁH2O (D) [Cu(HL)2(H2O)2] and (E)[Ni(H2L)(OAc)2]ꢁH2O.
2. There is a large variation in N(10)AN(16) bond lengths on com-
plexation. It becomes slightly longer as the coordination takes
place via N(6) atom and O(8) in case of [Cu(H2L)Cl2]ꢁH2O
complex while becomes shorter in case of [Cu(HL)(OAc)]
complex.
3. The C(11)AO(18) bond distance in [Cu(HL)(OAc)] complex
becomes longer due to the formation of the MAO bond which
makes the CAO bond weaker [44].
C(1)AC(2)AO(7), and N(16)AC(8)AC(1) angles which are
reduced or increased on complex formation as a consequence
of bonding.
5. The bond angles in complexes namely, [Cu(H2L)Cl2]ꢁH2O and
[Cu(HL)(OAc)] are quite near to a square planar geometry
predicting dsp2 hybridization.
3.7. Antimicrobial activity
4. The bond angles of the hydrazone moiety of L are altered
somewhat upon coordination but the angles around the metal
undergo appreciable variations upon changing the metal
centre [45]. the largest change affects C(8)AN(16)AN(10),
Minimum inhibitory concentration (MIC) [46,47] was
determined for each of the active compounds along with Gentamy-
cin and Colitrimazole as standard controls; results are shown in

84
R.R. Zaky, T.A. Yousef / Journal of Molecular Structure 1002 (2011) 76–85
Fig. 5. Molecular modelling of the ligand.
Fig. 6. Molecular modelling of [Cu(HL)(OAc)].
Fig. 7. Molecular modelling of [Cu(H2L)Cl2]ꢁH2O.
Table 8. This screening was performed against the Gram-negative
and Escherechia coli, in addition to the pathogenic fungi C. albicans.
The following standard organisms used in the antimicrobial
screening were obtained from IFO (Institute Fermentation of
Osaka); E. coli IFO 3301 and C. albicans IFO 0583. The tested
compounds were dissolved in dimethylsulphoxide (DMSO) at a
concentration of 1 mg/ml. Amongst all the compounds tested,
[Cu(H2L)Cl2]ꢁH2O demonstrated the most potent antimicrobial

R.R. Zaky, T.A. Yousef / Journal of Molecular Structure 1002 (2011) 76–85
85
Table 8
Antimicrobial and antimycotic activities in terms of MIC (mg/ml) after 48 h.
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Compound
E. coli
C. albicans
H2L
3000
1500
750
3000
750
187.5
375
–
3000
3000
375
1500
1500
3.75
–
[Co(H2L)(OAc)2]ꢁ2H2O
[Ni(H2L)(OAc)2]ꢁH2O
[Cu(HL)2(H2O)2]
[Cu(HL)(OAc)]
[Cu(H2L)Cl2]ꢁH2O
Gentamycin
Colitrimazole
5.85
´
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observed antimicrobial activity was highly dependent on the metal
complex, in which copper complex played an important role in
achieving an excellent level of biological activity. It is observed
from these studies that most of the metal chelates have a higher
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passage of only lipid soluble materials due to which liposolubility
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it increases the delocalization of p-electrons over the whole chelate
ring and enhances the lipophilicity of the complex. This increased
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of the microorganism. It was observed from the Table 8, complexes
demonstrated the lowest potent antimicrobial activity.
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Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.molstruc.2011.06.050.
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