Structural, spectral, thermal and biological studies on 2-oxo-N′-((4-oxo-4H-chromen-3-yl)methylene)-2-(phenylamino)acetohydrazide (H2L) and its metal complexes

Article abstract of DOI:10.1016/j.molstruc.2011.03.043

A new series of metal complexes formed by the reaction of 2-oxo-N′-((4-oxo-4H-chromen-3-yl)methylene)-2-(phenylamino) acetohydrazide(H₂L) and Cu(II), Co(II), Ni(II), Cd(II), Zn(II), Hg(II) and U(VI)O22+ ions. The isolated complexes have been characterized by elemental analyses, spectral (IR, UV-visible and ¹H NMR) as well as magnetic and thermal measurements. The data revealed that the ligand acts as neutral ON or ONO as well as mononegative ONO. On the basis of magnetic and electronic spectral data an octahedral geometry for the Co(II), Cu(II) and U(VI)O₂ complexes, a tetrahedral structure for the Ni(II), Cd(II), Zn(II) and Hg(II) complexes have been proposed. 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, kinetic parameters were determined for each thermal degradation stage of some complexes using Coats-Redfern and Horowitz-Metzger methods. Moreover, the ligand and its complexes were screened against Bacillus thuringiensis (Bt) as Gram positive bacteria and Pseudomonas aeuroginosa (Pa) Gram negative bacteria using the inhibitory zone diameter.

Full text of DOI:10.1016/j.molstruc.2011.03.043

Journal of Molecular Structure 1007 (2012) 1–10
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Structural, spectral, thermal and biological studies on
2-oxo-N0-((4-oxo-4H-chromen-3-yl)methylene)-2-(phenylamino)
acetohydrazide (H2L) and its metal complexes
⇑
Ola A. El-Gammal, Gaber Abu El-Reash , Sara F. Ahmed
Department of Chemistry, Faculty of Science, Mansoura University, Mansoura, P.O.Box 70, Mansoura, Egypt
a r t i c l e i n f o
a b s t r a c t
A new series of metal complexes formed by the reaction of 2-oxo-N0-((4-oxo-4H-chromen-3-yl)methy-
Article history:
lene)-2-(phenylamino)acetohydrazide(H2L) and Cu(II), Co(II), Ni(II), Cd(II), Zn(II), Hg(II) and U(VI)O2þ
Received 30 November 2010
Received in revised form 15 March 2011
Accepted 18 March 2011
2
ions. The isolated complexes have been characterized by elemental analyses, spectral (IR, UV–visible
and 1H NMR) as well as magnetic and thermal measurements. The data revealed that the ligand acts
as neutral ON or ONO as well as mononegative ONO. On the basis of magnetic and electronic spectral data
an octahedral geometry for the Co(II), Cu(II) and U(VI)O2 complexes, a tetrahedral structure for the Ni(II),
Cd(II), Zn(II) and Hg(II) complexes have been proposed. 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, kinetic parameters were determined for each thermal degradation
stage of some complexes using Coats–Redfern and Horowitz-Metzger methods. Moreover, the ligand and
its complexes were screened against Bacillus thuringiensis (Bt) as Gram positive bacteria and Pseudomonas
aeuroginosa (Pa) Gram negative bacteria using the inhibitory zone diameter.
Available online 25 March 2011
Keywords:
2-Oxo-N0-((4-oxo-4H-chromen-3-
yl)methylene)-2-
(phenylamino)acetohydrazide (H2L)
Coats–Redfern
Horowitz–Metzger
Antimicrobial activity
Hydrazone derivatives
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
ters as entropy (DS), enthalpy (DH) and free energy (DG) for each
step of degradation have been evaluated. In addition the antibacte-
rial activity of the ligand and its metal complexes against (Bt) as
Gram positive bacteria and (Pa) as Gram negative bacteria using
the inhibitory zone diameter was evaluated.
Hydrazones are important class of ligands which present in
numerous physiological and biological applications as antimicro-
bial, antitumour agents, insecticides, anticoagulants, anticonvul-
sant, analgesic, antioxidants, anti-inflammatory, antiplatelet,
antitubercular and plant growth regulators [1–4].
Metal complexes of hydrazones have found applications as cat-
alysts [5], luminescent probes [6], nonlinear optics and molecular
sensors [7]. Moreover, it has been recently shown that pyridoxal
isonicotinyl hydrazone can be used in the treatment of iron over-
load [8].
Chromone derivatives offered interesting possibilities from the
point of view of both organic synthesis and assays of their biolog-
ical activity [9]. We were thus motivated to undertake a systematic
study of preparation and characterization of a new transition metal
complexes formed with 2-oxo-N0-((4-oxo-4H-chromen-3-yl)meth-
ylene)-2-(phenylamino)acetohydrazide (H2L) and Cu(II), Co(II),
Ni(II), Cd(II), Zn(II), Hg(II) and U(VI)O22þ ions. Also, the thermal deg-
radation and kinetic parameters such as energy of activation (Ea)
and the pre-exponential factor (A); and thermodynamic parame-
2. Experimental
2.1. Instrumentation and materials
All the chemicals were purchased from Aldrich and Fluka and
used without further purification. Elemental analyses (C, H and
N) were performed with a Perkin–Elmer 2400 series II analyzer.
IR spectra (4000–400 cmꢀ1) for KBr discs were recorded on a Matt-
son 5000 FTIR spectrophotometer. Electronic spectra were re-
corded on a Unicam UV–Vis spectrophotometer UV2. Magnetic
susceptibilities were measured with a Sherwood scientific mag-
netic susceptibility balance at 298 K. 1H NMR measurements in
d6-DMSO at room temperature were carried out on a Varian Gem-
ini WM-200 MHz spectrometer at the Microanalytical Unit, Cairo
University. Thermogravimetric measurements (TGA, DTA, 20–
1000 °C) were recorded on a DTG-50 Shimadzu thermogravimetric
analyzer at a heating rate of 10 °C/min and nitrogen flow rate of
20 ml/min.
⇑
Corresponding author.
E-mail address: gaelreash@mans.edu.eg (G.A. El-Reash).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.03.043

2
O.A. El-Gammal et al. / Journal of Molecular Structure 1007 (2012) 1–10
2.2. Synthesis of H2OCAH
3. Results and discussion
3.1. IR and 1HNMR spectra
2-hydrazino-2-oxo-N-phenyl-acetamide 2-Hydrazino-2-oxo-N-
phenyl-acetamide was synthesized according to the general
literature method [10]. H2L was synthesized by heating under re-
flux for 4 h an ethanolic solution of 2-hydrazino-2-oxo-N-phenyl-
acetamide in a 1:1 molar ratio with 3-chromonaldehyde. The pale
yellow precipitate was filtered off, washed several times with eth-
anol and recrystallized from hot ethanol and finally dried in vac-
uum desiccator over anhydrous CaCl2.
The most important IR bands of H2L (Structure 1) and its com-
plexes with probable assignments are given in Table 2. The ligand
has multi-coordination sites which gave variable coordination
modes. A comparison of the spectrum of H2L and those of com-
plexes revealed that the ligand coordinates in the keto and enol
forms. H2L shows two bands at 1566 and 1598 cmꢀ1 assignable
to
[13]. The two sharp bands located at 1680 and 1639 cmꢀ1 are
attributed to (C@O) (Chromonic) and
(C@O)2 + (C@O)3]-
(hydrazonic) vibrations, respectively. The medium bands observed
at 3284 and 3252 cmꢀ1 are attributable to (N1H) [14] and (N4H)
[15] vibrations, respectively. The medium intensity band at
1084 cmꢀ1 is referred to
(NAN) vibration [16]. The absence of
m(C@N) (azomethine) and m(C@C)phenyl vibrations, respectively
2.3. Synthesis of metal complexes
m
[
m
m
A hot ethanolic solution of the respective metal chlorides Co(II),
Ni(II), Cu(II), Cd(II), Hg(II) or acetates (Zn(II) and U(VI)O2)
(1.0 mmol) was added to hot ethanolic solution of H2L (0.335 g,
1.0 mmol). The resultant mixture was heated under reflux for 2–
3 h., 0.5 gm of sodium acetate in 30 ml bidistilled water was added
as a buffering agent except in case of zinc and uranyl complexes.
The formed precipitates were filtered off, washed with ethanol fol-
lowed by diethyl ether and dried in a vacuum desiccator over
anhydrous CaCl2. The physical and analytical data of the isolated
complexes are listed in Table 1. The complexes have high melting
points and insoluble in common organic solvents; partially soluble
in DMSO and DMF and found to be non-electrolytes.
m
m
m
hydrogen bond does not suggest the hydrogen bonding [17].
The 1H NMR spectrum of H2L in d6-DMSO shows two signals at
d@10.06 and 10.27 ppm relative to TMS assignable to N1H and N4H
[14] protons, respectively. The multiplets at 7.00–8.50 ppm are as-
signed to the phenyl ring protons [18], while the signals at 8.6 and
8.7 ppm are due to CH(chromonic) proton [19] and CH proton [20] of
azomethine group, respectively.
The position of the bands assigned to
m
(C@O)2(hydrazonic) and
m
(N1H) vibrations remaining unchanged in all complexes indicat-
ing that these groups are not involved in coordination.
IR spectrum of [Co(H2L)Cl2(H2O)2] complex indicates that H2L
behaves as a neutral NO bidentate via C@N(azomethine) and
C@O(chromonic) groups (Structure 2). This behavior is revealed
2.4. Antibacterial activity
The in vitro antibacterial of the reported complexes was evalu-
ated against Bacillus thuringiensis (Bt) as Gram positive and Pseudo-
monas aeuroginosa (Pa) Gram negative bacterial cultures using
Gentamicin as standard control. The hole plate diffusion method
[11] was adopted for the activity measurements. The bacterial
strains were grown in nutrient agar slants. A suspension of the
by the shift of
wavenumber. The
confirming contribution of azomethine group in coordination
[17] and
(C@O)3(hydrazonic) band remains practically unaltered
m
(C@N) and
m(C@O)(chromonic) bands to lower
m(NAN) vibration shifts to lower wavenumber
m
indicating that this group is not participated in bonding.
In [Hg(H2L)Cl2]H2O (Structure 3) and [UO2(H2L)(OAc)2]H2O
complexes, H2L coordinates as a neutral NO bidentate through
C@N(azomethine) and C@O3 (hydrazonic) groups. This mode of
studied compounds (0.2 ml of each (10 lg/ml) was incubated at
36 °C for 36 h for the bacterial culture. After inoculation, the diam-
eter (in mm) of the clear inhibition zone surrounding the sample is
taken as a measure of the inhibition power against the particular
organisms. The experiments were repeated three times and the
values recorded are the mean average.
chelation is confirmed by the shift of
m
m
m
(C@N)(azomethine) and
(C@O)3(hydrazonic) to lower wavenumber. The presence of
(C@O)(chromonic) band at the same position suggesting that this
group is not participating in coordination. The broad bands ob-
served at 1553 and 1431 cmꢀ1 assignable to
as(OCO) and s(OCO)
vibrations, respectively with frequency difference (
= 122 cmꢀ1
m
m
D
m
)
2.5. Molecular modeling
[21] confirming monodentate nature of the acetate group [22].
Moreover, the IR spectrum exhibits two bands at 914 and
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 [12]. 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
820 cmꢀ1, assignable to asymmetric stretching frequency (m3
)
and symmetric stretching frequency (
m1), respectively, of the diox-
ouranium ion [17,23]. The force constant (F) for the bonding sites
of m(U@O) is calculated by the method of McGlynn et al. [24]; FUAO
value is found to be 6.89 mdynes Åꢀ1. Also, the UAO bond distance
gradient of 0.01 kcal molꢀ1
.
is calculated by the method of Jones; [25] RUAO value is 1.73 Å fall-
Table 1
Analytical and physical data of H2L and its metal complexes.
Compound, empirical formula, (F.Wt)
Color
M.p. (°C)
% Found (Calcd.)
M
Yield (%)
Cl
C
H
H2L, C18H13N3O4, (335.3)
Pale yellow
Green
Reddish brown
Green
Pale yellow
Orange
Pale yellow
Deep brown
270
–
–
63.10 (64.47)
42.86 (42.74)
43.09 (43.14)
50.33 (50.45)
43.10 (43.22)
50.24 (50.39)
33.87 (34.60)
35.33 (35.64)
3.19 (3.91)
3.22 (3.39)
2.88 (3.42)
2.99 (2.82)
2.75 (2.82)
3.11 (3.59)
2.01 (2.42)
2.56 (2.85)
93
80
84
86
72
81
76
78
[Cu(H2L)Cl2(H2O)]H2O, C18H17Cl2CuN3O6, (505.8)
[Co(H2L)Cl2(H2O)2], C18H17Cl2CoN3O6, (501.2)
[Ni(HL)Cl], C18H12ClN3NiO4, (428.5)
[Cd(HL)Cl]H2O, C18H14CdClN3O5, (500.2)
[Zn(HL)(OAc)]H2O, C20H17N3O7Zn, (476.8)
[Hg(H2L)Cl2]H2O, C18H15Cl2HgN3O5, (624.8)
[UO2(H2L)(OAc)2]H2O, C22H21N3O11U, (741.4)
>300
>300
>300
294
>300
295
12.10 (12.56)
11.90 (11.76)
13.15 (13.69)
21.98 (22.47)
13.20 (13.72)
32.80 (32.10)
32.01 (32.10)
14.31 (14.02)
13.89 (14.15)
8.33 (8.27)
6.88 (7.09)
–
10.91 (11.35)
–
>300

O.A. El-Gammal et al. / Journal of Molecular Structure 1007 (2012) 1–10
3
O
O
O
O
O
*
H
N
N
N
H
N
N
N
H
O
OH
O
4
2
2
3
1
Structure 1. H2L.
Table 2
Principle infrared bands of H2L and its metal complexes.
Compound
m(C@N)
m
(C@0)2
m
(C@0)3
m(C@0)Chr
m
(N4H)
m
(CAO)
m
(NAN)
m
(C@N)*
m
(MAO)
m(MAN)
H2L
1566
1521
1550
1554
1573
1575
1540
1535
1639
1641
1639
1642
1643
1644
1639
1643
1639
1617
1639
–
–
–
1680
1677
1665
1658
1666
1660
1679
1681
3252
3252
3253
–
–
–
–
–
–
1108
1114
1114
–
1084
1060
1060
1074
1074
1074
1081
1080
–
–
–
1610
1616
1610
–
–
–
[Cu(H2L)Cl2(H2O)]H2O
[Co(H2L)Cl2(H2O)2]
[Ni(HL)Cl]
[Cd(HL)Cl]H2O
[Zn(HL)(OAc)]H2O
[Hg(H2L)Cl2]H2O
[UO2(H2L)(OAc)2]H2O
501
500
500
514
514
500
514
434
473
474
460
474
474
447
1633
1620
3253
3255
–
–
Chr: chromonaldehyde.
*
New azomethine band.
Structure 2.
ing in the usual range as reported earlier [26] and extremely in
accordance with that calculated by the use of MM + force field
(as implemented in hyperchem 8.0) [12].
(C@O)(chromonic) groups. This mode of chelation is confirmed
by the following observations; (i) A shift of (C@O)(chromonic)
to lower wavenumber, (ii) A shift of (C@N)(azomethine) either
m
m
Also, H2L behaves as neutral ONO tridentate ligand through
C@N(azomethine), C@O3(hydrazonic) and (C@O)(chromonic)
groups in [Cu(H2L)Cl2(H2O)]H2O (Structure 4). This behavior is sug-
to lower wavenumber in Ni(II) complex or to higher wavenumber
in Cd(II) and Zn(II) complexes and (iii) the disappearance of bands
due to
neous appearance of new bands in the regions (1610–1616 cmꢀ1
and (1108–1114 cmꢀ1), respectively attributable to new
(C@N)
m m
(N4H) and (C@O)3(hydrazonic) vibrations with simulta-
gested by the shift of
m
(C@O)(chromonic),
m
(C@N)(azomethine)
)
and
m
(C@O)2(hydrazonic) vibrations to lower wavenumber.
m
Finally, HOCAH coordinates in mononegative ONO tridentate
manner in [Ni(HL)Cl] (Structure 5), [Cd(HL)Cl]H2O (Structure 6)
and [Zn(HL)(OAc)]H2O (Structure 7) through C@N(azomethine),
deprotonated carbonyl oxygen (@CAOA)3(hydrazonic) and
[27] and m(CAO) vibrations [28].
Enolization of the carbonyl oxygen (@CAOA)3(hydrazonic) is
further confirmed by the absence of the signal due to N4H proton
in the 1H NMR spectrum of Cd(II) complex. Also, the N1H proton

4
O.A. El-Gammal et al. / Journal of Molecular Structure 1007 (2012) 1–10
Structure 3.
Structure 4.
Structure 5.
Structure 6.
appeared singlet at 10.60 ppm nearly at the same position that ob-
served in H2L ligand.
The broad bands at ꢁ3399–3454, 868–850, and at ꢁ567 cmꢀ1 in
the IR spectra of the investigated complexes are referred to m(OH),
New bands observed in all complexes at 500–514 and 434–
D(H2O), pr(H2O) and Pw (H2O) vibrations for the coordinated water.
474 cmꢀ1 tentatively assigned to
respectively.
m(MAO) [29] and
m(MAN) [30],
The broad band centered at 3500 cmꢀ1 in the spectra of the studied
complexes may be due to hydrated water. To verify between the

O.A. El-Gammal et al. / Journal of Molecular Structure 1007 (2012) 1–10
5
Structure 7.
Table 3
Spectral absorption bands, magnetic moments and ligand field parameters of H2L metal complexes.
Compound
Band position (cmꢀ1
)
Assignment
Ligand field parameters
leff (BM)
Dq (cmꢀ1
)
B (cmꢀ1
)
b
[Cu(H2L)Cl2(H2O)]H2O
13,440
15,200
23,148
2B1g
2B1g
LMCT
?
?
2Eg
–
–
–
2.08
2A1g
[Ni(HL)Cl]
[Co(H2L)Cl2(H2O)2]
17,450
14,880
17,860
3T1(F) ? 3T1(P)
4T1g(F) ? 4A2g(F)
4T1g(F) ? 4T1g(p)
–
762
–
794
–
0.81
3.6
5.57
[UO2(H2L)(OAc)2]H2O
[Zn(HL)(OAc)]H2O
21,930
27,625
1R+
?
2p4
–
–
–
0.0
0.0
g
n ? p⁄
24,271
22,222
Charge transfer
LMCT: ligand to metal charge transfer.
Table 4
Decomposition steps with the temperature range and weight loss for H2L complexes.
Complex
Temp. range (°C)
Removed species
Wt. loss
Found (%)
Calcd (%)
[Cu(H2L)Cl2H2O]H2O
31–112
AH2O
3.45
3.56
113–240
241–389
390–555
556–779
780–800
A(H2O + 0.5Cl2)
A(C6H6N + 0.5Cl2)
A(C3N2OH)
AC9H5O2
ACuO(residue)
10.65
25.01
16.17
28.45
15.52
10.56
25.22
16.02
28.69
15.72
[Ni(HL)Cl]
338–480
480–589
590–800
A(C6H6N + CO + C2N2H + 0.5Cl2)
AC9H5O2
ANiO(residue)
48.88
33.11
17.98
48.68
33.87
17.43
[Cd(HL)Cl]H2O
34–116
AH2O
3.33
3.60
224–422
423–589
743–795
796–800
A(C7H6NO + 0.5Cl2)
AC2N2H
AC9H5O2
31.25
11.31
28.50
25.54
31.10
10.60
29.01
25.67
ACdO(residue)
[Zn(HL)(OAc)]H2O
32–124
AH2O
3.75
3.77
353–528
529–759
760–800
A(OAc + C7H6NO + C9H5O2)
AC2N2H
AZnO(residue)
67.02
12.21
16.98
68.01
11.12
17.06
coordinated and hydrated water, TGA measurement was carried
out.
insolubility. Electronic spectra of metal complexes were measured
in dimethylsulfoxide (DMSO) solution. The tentative assignments
of the significant spectral absorption bands, magnetic moments
and ligand field parameters of metal complexes are given in Table
3.
3.2. Electronic spectra and magnetic measurements
The n ? p⁄ transitions associated to the azomethine and car-
bonyl functions of the ligand could not be displayed because its
The electronic spectrum of [Cu(H2L)Cl2(H2O)]H2O shows two
bands at 13,440 and 15,197 cmꢀ1 attributable to 2B1g ? 2Eg and

6
O.A. El-Gammal et al. / Journal of Molecular Structure 1007 (2012) 1–10
2B1g ? 2A1g transitions, respectively, in an octahedral geometry
[29,31]. A new absorption at 23,148 cmꢀ1 was attributed to a li-
gand to metal charge transfer transition. The magnetic moment va-
lue is higher than normal range of copper (II) complexes which
may be referred to spin–orbital coupling [32].
The electronic spectrum of the [Ni(HL)Cl] exhibits a broad band
at 17,452 cmꢀ1 assigned to 3T1(F) ? 3T1(P) transition. The band po-
sition and the magnetic moment value (Table 3) can be taken as
evidence for the tetrahedral stereochemistry [33].
In its TG thermogram, the first stage at 31–112 °C with weight loss
of 3.45 (Calcd. 3.56%) is corresponding to the loss of one lattice
water molecule. The second step with weight loss of 10.65 (Calcd.
10.56%) at 113–240 °C is attributed to the elimination of
H2O + 0.5Cl2. The third step at 241–389 °C with weight loss of
25.01 (Calcd. 25.22%) is referring to the removal of C6H6N + 0.5Cl2.
The fourth step corresponds to the elimination of C3N2OH with
weight loss of 16.17 (Calcd. 16.02%). This is followed by loss of
C9H5O2 fragment with weight loss of 28.45 (Calcd. 28.69%). The
residual part is CuO (Found 15.52, Calcd. 15.72%). An inspection
of the data represented in Table 4 indicates that the TG thermo-
grams displayed a high residual part for the studied complexes
reflecting a higher thermal stability owing to the existence of five
membered rings.
The electronic spectrum of [Co(H2L)Cl2(H2O)2] shows two bands
4
at 14,880 and 17,857 cmꢀ1 assignable to the T1g(F) ? 4A2g(F) and
4T1g(F) ? 4T1g(p) transitions, respectively, for octahedral geometry
[34]. The magnetic moment value (leff = 5.57 BM) and the ligand
field parameters are further evidence for octahedral Co(II) com-
plexes [35]. The high value of leff may be due to high orbital
contribution.
3.4. Kinetic data
Finally, the spectrum of [UO2(H2L)(OAc)2]H2O exhibits two
bands, the first one at 27,624 cmꢀ1 due to a charge transfer, prob-
ably H2L ? O@U@O, while the second band at 21,929 cmꢀ1 may be
The kinetic and thermodynamic parameters of the thermal deg-
radation process have been calculated using Coats–Redfern and
Horowitz–Metzger models [37,38]. Coats–Redfern relation is as
follows:
assigned to the 1R+
?
2p4 transition [36].
g
3.3. Thermogravimetric studies
ꢀ
ꢁ
ꢂ
ꢃ
lnð1 ꢀ
aÞ
AR
bE
E
RT
ln ꢀ
¼ ln
ꢀ
ð1Þ
T2
The stages of decomposition, temperature range, decomposition
product as well as the weight loss percentages of some metal com-
plexes are given in Table 4. Fig. 1 shows the TGA curves of some
metal complexes. [Cu(H2L)Cl2H2O]H2O a representative example.
where
fined by:
a
represents the fraction of sample decomposed at time t, de-
woꢀwt
a
¼
1, wo, wt and w1 are the weight of the sample be-
woꢀw
(B)
(A)
(D)
(C)
Fig. 1. (A) Thermal analysis curve (TGA, DTG) of [Cu(H2L)Cl2H2O]H2O. (B) Thermal analysis curve (TGA, DTG) of [Ni(HL)Cl]. (C) Thermal analysis curve (TGA, DTG) of
[Cd(HL)Cl]H2O. (D) Thermal analysis curve (TGA, DTG) of [Zn(HL)(OAc)]H2O.

O.A. El-Gammal et al. / Journal of Molecular Structure 1007 (2012) 1–10
7
Table 5
Kinetic parameters evaluated by Coats–Redfern equation for H2L complexes.
Complex coats
[Ni(HL)Cl]
Peak
Mid temp (K)
Ea kJ/mol
A (Sꢀ1
)
D
H⁄ (kJ/mol)
D
S⁄ (kJ/mol K)
D
G⁄ (kJ/mol)
1st
2nd
682
800
161.99
230.64
3.42 ꢄ 105
156.32
223.99
ꢀ0.145
ꢀ0.139
255.87
335.65
8.61 ꢄ 105
[Cu(H2L)Cl2(H2O)2]H2O
1st
344
449
587
745
941
53.97
57.67
86.46
90.89
153.38
3.57 ꢄ 104
6.68 ꢄ 104
7.88 ꢄ 104
1.80 ꢄ 105
2.78 ꢄ 105
51.11
53.94
81.58
84.70
145.56
ꢀ0.158
ꢀ0.155
ꢀ0.156
ꢀ0.151
ꢀ0.150
105.78
123.96
173.63
197.85
286.92
2nd
3rd
4th
5th
[Zn(HL)(OAc)]H2O
[Cd(HL)Cl]H2O
1st
2nd
3rd
350
713
918
54.02
111.99
138.31
6.01 ꢄ 104
1.36 ꢄ 105
1.73 ꢄ 105
3.00 ꢄ 104
1.20 ꢄ 105
3.55 ꢄ 105
3.38 ꢄ 106
51.11
106.06
130.68
ꢀ0.154
ꢀ0.153
ꢀ0.153
ꢀ0.160
ꢀ0.153
ꢀ0.146
ꢀ0.130
105.27
215.76
272.00
1st
348
596
779
45.44
74.21
108.25
690.94
42.55
69.25
101.78
682.28
98.39
160.67
216.01
818.08
2nd
3rd
4th
1042
fore 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
Metzger [38] methods (Tables 5 and 6). In both methods, the lift
side of Eqs. (3) and (4) are plotted against 1/T and h, respectively
(Figs. 2–9). From the results, the following remarks can be pointed
out:
lnð1ꢀ
a
pre-exponential factor, respectively. A plot of ln½ꢀ
Þꢂ 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 [38] used to evaluate the degra-
dation kinetics is:
– 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 [41].
– The positive sign of
DG for the investigated complexes reveals
Eh
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,
ln ½ꢀ lnð1 ꢀ
aÞꢂ ¼
ð2Þ
RT2s
where h = T ꢀ Ts, Ts is the DTG peak temperature, T is the tempera-
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 [42–44].
– The negative values of S for the degradation process indicates
ture corresponding to weight loss Wt. A straight line should be ob-
E
served between ln½ꢀ lnð1 ꢀ
a
Þꢂ and h with a slope of RT2. A number of
s
D
degradation processes can be represented as a first order reaction.
Particularly, the degradation of a series of H2L complexes was sug-
gested to be first order [39], therefore we assume n = 1 for the
remainder. The other thermodynamic parameters of activation
can be calculated by Eyring equation [40]:
D
D
more ordered activated complex than the reactants or the reac-
tion is slow [40].
D
D
D
Hꢃ ¼ E ꢀ RT
ð3Þ
ð4Þ
ð5Þ
hA
Sꢃ ¼ R ln
kBT
3.5. Molecular modeling
Gꢃ ¼
D
H ꢀ T
DS
The molecular structure along with atom numbering of H2L and
its metal complexes are shown in Structures 1–7. Analysis of the
data in Tables 1S–14S (Supplementary materials) calculated for
the bond lengths and angles for the bond, one can conclude the fol-
lowing remarks:
Thermodynamic parameters such as activation energy (E), pre-
exponential factor (A), entropy of activation ( S), enthalpy of acti-
vation ( H) and free energy of activation ( G) of decomposition
D
D
D
steps were calculated using Coats–Redfern [37] and Horowitz–
Table 6
Kinetic parameters evaluated by Horowitz–Metzger equation for H2L complexes.
Complex Horowitz
Peak
Mid temp (K)
Ea (kJ/mol)
A (Sꢀ1
)
D
H⁄ (kJ/mol)
D
S⁄ (kJ/mol K)
D
G⁄ (kJ/mol)
[Ni(HL)Cl]
1st
2nd
682
808
161.70
230.81
3.56 ꢄ 105
156.02
224.09
ꢀ0.145
ꢀ0.139
255.34
336.84
8.70 ꢄ 105
[Cu(H2L)Cl2(H2O)2]H2O
1st
344
449
587
745
941
53.79
57.57
86.05
90.72
153.86
3.69 ꢄ 104
7.41 ꢄ 104
7.62 ꢄ 104
1.85 ꢄ 105
2.85 ꢄ 105
50.93
53.84
81.17
84.52
146.04
ꢀ0.158
ꢀ0.155
ꢀ0.157
ꢀ0.151
ꢀ0.150
105.51
123.47
173.38
197.51
287.21
2nd
3rd
4th
5th
[Zn(HL)(OAc)]H2O
[Cd(HL)Cl]H2O
1st
2nd
3rd
350
713
918
54.99
111.37
138.72
6.58 ꢄ 104
1.35 ꢄ 105
1.74 ꢄ 105
3.08 ꢄ 104
1.22 ꢄ 105
3.80 ꢄ 105
3.16 ꢄ 106
52.08
105.44
131.09
ꢀ0.154
ꢀ0.153
ꢀ0.153
ꢀ0.160
ꢀ0.153
ꢀ0.146
ꢀ0.130
105.98
215.19
272.40
1st
348
596
779
45.75
74.51
108.01
690.65
42.85
69.55
101.54
681.99
98.63
160.88
215.33
818.37
2nd
3rd
4th
1042

8
O.A. El-Gammal et al. / Journal of Molecular Structure 1007 (2012) 1–10
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
Linear Fit of Data1_J
-12.0
-11.5
lnX n = 0.5
Linear Fit of Data1_J
###
-13.0
-13.5
-14.0
-14.5
-12.5
-13.0
0.0027
0.0028
0.0029
1/T
0.0030
0.0031
0.00138
0.00141
1/T
0.00144
0.00147
Fig. 4. Coats–Redfern plot of first degradation step for [Cu(H2L)Cl2(H2O)]H2O
complex.
Fig. 2. Coats–Redfern plots first degradation steps for [Ni(HL)Cl] complex.
lnX n=1
0.5
1. The N(10)AN(11) and N(11)AC(14) bond lengths becomes
slightly longer in complexes as the coordination takes place
via N atoms of AC@NAN@CA group that is formed on deproto-
nation of OH group in [Ni(HL)Cl], [Cd(HL)Cl]H2O and
[Zn(HL)(OAc)]H2O complexes [14].
lnX n=0.66
lnX n=0.33
lnX n=0
lnX n = 0.5
Linear Fit of Data1_J
0.0
###
2. In [Ni(HL)Cl], [Cd(HL)Cl]H2O and [Zn(HL)(OAc)]H2O complexes,
C(9)AO(13) and C(9)AN(10) bond distances are enlonged and
shortened, respectively. This is referred to the formation of
the MAO bond which makes the CAO bond weaker and forming
-0.5
a
double bond character [45]. On the other hand, in
[Co(H2L)Cl2(H2O)2] and [Hg(H2L)Cl2]H2O complexes, this bond
distance remains practically unaltered indicating that this
group is not participated in bonding [46].
-1.0
-1.5
3. The bond angles of the hydrazone moiety of H2L are altered
somewhat upon coordination but the angles around the metal
undergo appreciable variations upon changing the metal center
[46]; the largest change affects C(9)AN(10)AN(11),
-20
-10
0
10
20
T-Ts
Fig. 5. Horowitz–Metzger plot of first degradation step for [Cu(H2L)Cl2(H2O)]H2O
complex.
lnX n=1
lnX n=0.66
lnX n=0.33
lnX n=1
lnX n=0.66
lnX n=0.33
lnX n=0
-11.0
0
lnX n=0
lnX n = 0.5
Linear Fit of Data1_J
lnX n = 0.5
Linear Fit of Data1_J
-11.5
-12.0
-12.5
-1
-2
0.0026
0.0027
0.0028
0.0029
-15
0
15
30
T-Ts
1/T
Fig. 3. Horowitz–Metzger plot of first degradation step for [Ni(HL)Cl] complex.
Fig. 6. Coats–Redfern plot of first degradation step for [Zn(HL)(OAc)]H2O complex.

O.A. El-Gammal et al. / Journal of Molecular Structure 1007 (2012) 1–10
9
lnX n=1
lnX n=1
lnX n=0.66
lnX n=0.33
lnX n=0
0.5
lnX n=0.66
lnX n=0.33
lnX n=0
1.0
0.5
lnX n = 0.5
Linear Fit of Data1_J
lnX n = 0.5
Linear Fit of Data1_J
0.0
-0.5
-1.0
0.0
-0.5
-1.0
-10
0
10
-10
0
10
20
T-Ts
30
40
50
T-Ts
Fig. 9. Horowitz–Metzger plot of first degradation step for [Cd(HL)Cl]H2O complex.
Fig. 7. Horowitz–Metzger plot of first degradation step for [Zn(HL)(OAc)]H2O
complex.
4. 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 represents the ability of a molecule receiving
electron as in Table 7 [47].
lnX n=1
lnX n=0.66
lnX n=0.33
-11.5
lnX n=0
3.6. Antimicrobial activity
lnX n = 0.5
Linear Fit of Data1_J
The biological activity of H2L and its complexes against
B. thuringiensis (Bt) as Gram positive bacteria and P. aeuroginosa
(Pa) as Gram negative bacteria is summarized in Table 8. It is clear
that the complexes exhibit high inhibition activity against bacteria
Bt and Pa.
-12.0
-12.5
[Cd(HL)Cl]H2O and [UO2(H2L)(OAc)2]H2O complexes exhibited
high inhibitory effects on Bt while [Hg(H2L)Cl2]H2O complex
against Pa organisms. The lowest one is H2L. This can be attributed
to the ability of the complexes to diffuse into the cell membrane of
the organism. Examining the values for Gram’s positive bacteria in
Table 5, one can arrange the compounds as:[Cd(HL)Cl]H2O =
[UO2(H2 L)(OAc)2]H2O > [Hg(H2L)Cl2]H2O > [Co(H2L)Cl2(H2O)2] >
[Ni(HL)Cl] > [Zn(HL)(OAc)]H2O > [Cu(H2L)Cl2(H2O)]H2O > H2L.
On the other hand, the inhibition activity values against
Gram’s negative can arrange the compounds as: [Hg(H2L)Cl2]H2O >
[Cd(HL)Cl]H2O > [Ni(HL)Cl] > [UO2(H2L)(OAc)2]H2O > [Zn(HL)(OAc)]-
H2O > [Co(H2L)Cl2(H2O)2].
0.0028
0.0029
1/T
0.0030
Fig. 8. Coats–Redfern plot of first degradation step for [Cd(HL)Cl]H2O complex.
4. Conclusion
O(13)AC(9)AN(10) and O(13)AC(9)AC(8) angles which are
reduced or increased on complex formation as a consequence
of bonding [14].
The complexes: [UO2(H2L)(OAc)2]H2O, [Co(H2L)Cl2(H2O)2],
[Ni(HL)Cl], [Cd(HL)Cl]H2O, [Zn(HL)(OAc)]H2O, [Hg(H2L)Cl2]H2O,
[Cu(H2L)Cl2(H2O)]H2O have been synthesized with 2-oxo-N0-((4-
Table 7
Some energetic properties of H2L and its complexes calculated by PM3 method.
Compound
Total energy
(kcal/mol)
Binding energy
(kcal/mol)
Electronic energy
(kcal/mol)
Heat of formation
(kcal/mol)
Dipole
moment (D)
HOMO (eV)
LUMO (eV)
H2L
ꢀ9.20 ꢄ 104
ꢀ1.41 ꢄ 105
ꢀ1.40 ꢄ 105
ꢀ1.07 ꢄ 105
1.23 ꢄ 105
ꢀ4363.36
ꢀ4784.26
ꢀ5294.86
ꢀ4505.53
ꢀ4621.17
ꢀ4353.57
ꢀ4991.80
ꢀ6.21 ꢄ 105
ꢀ1.01 ꢄ 106
ꢀ1.06 ꢄ 106
ꢀ7.94 ꢄ 105
ꢀ8.17 ꢄ 105
ꢀ6.85 ꢄ 105
ꢀ8.40 ꢄ 105
ꢀ32.78
ꢀ151.23
ꢀ476.38
ꢀ102.28
ꢀ210.90
ꢀ19.38
2.04
5.87
2.99
11.45
12.47
4.72
ꢀ9.20
ꢀ4.20
ꢀ4.03
ꢀ9.38
ꢀ7.88
ꢀ8.94
ꢀ8.64
ꢀ0.80
ꢀ1.26
ꢀ1.39
ꢀ1.90
ꢀ1.94
ꢀ0.98
ꢀ1.67
[Cu(H2L)Cl2(H2O)]H2O
[Co(H2L)Cl2(H2O)2]
[Hg(H2L)Cl2]H2O
[Ni(HL)Cl]
[Cd(HL)Cl]H2O
[Zn(HL)(OAc)]H2O
ꢀ9.95 ꢄ 104
ꢀ1.12 ꢄ 105
ꢀ64.94
8.39

10
O.A. El-Gammal et al. / Journal of Molecular Structure 1007 (2012) 1–10
Table 8
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Compound
Zone of inhibition of bacterial growth (mm)
Bacillus thuringiensis
Pseudomonas aeuroginosa
(Gram-positive)
(Gram-negative)
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Gentamicin
H2L
[Cu(H2L)Cl2(H2O)]H2O 40
[Co(H2L)Cl2(H2O)2]
[Ni(HL)Cl]
48
35
48
0
0
14
44
47
26
48
30
56
54
71
48
65
71
[Cd(HL)Cl]H2O
[Zn(HL)(OAc)]H2O
[Hg(H2L)Cl2]H2O
[UO2(H2L)(OAc)2]H2O
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geometry for Co(II), Cu(II) and U(VI)O22þ, a tetrahedral structure
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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.2011.03.043.
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