Spectral, thermal, kinetic, molecular modeling and eukaryotic DNA degradation studies for a new series of albendazole (HABZ) complexes

Article abstract of DOI:10.1016/j.saa.2010.09.021

This work represents the elaborated investigation for the ligational behavior of the albendazole ligand through its coordination with, Cu(II), Mn(II), Ni(II), Co(II) and Cr(III) ions. Elemental analysis, molar conductance, magnetic moment, spectral studies (IR, UV-Vis and ESR) and thermogravimetric analysis (TG and DTG) have been used to characterize the isolated complexes. A deliberate comparison for the IR spectra reveals that the ligand coordinated with all mentioned metal ions by the same manner as a neutral bidentate through carbonyl of ester moiety and NH groups. The proposed chelation form for such complexes is expected through out the preparation conditions in a relatively acidic medium. The powder XRD study reflects the amorphous nature for the investigated complexes except Mn(II). The conductivity measurements reflect the non-electrolytic feature for all complexes. In comparing with the constants for the magnetic measurements as well as the electronic spectral data, the octahedral structure was proposed strongly for Cr(III) and Ni(II), the tetrahedral for Co(II) and Mn(II) complexes but the square-pyramidal for the Cu(II) one. The thermogravimetric analysis confirms the presence or absence of water molecules by any type of attachments. Also, the kinetic parameters are estimated from DTG and TG curves. ESR spectrum data for Cu(II) solid complex confirms the square-pyramidal state is the most fitted one for the coordinated structure. The albendazole ligand and its complexes are biologically investigated against two bacteria as well as their effective effect on degradation of calf thymus DNA.

Full text of DOI:10.1016/j.saa.2010.09.021

Spectrochimica Acta Part A 78 (2011) 196–204
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Spectral, thermal, kinetic, molecular modeling and eukaryotic DNA degradation
studies for a new series of albendazole (HABZ) complexes
Nashwa M. El-Metwalya,∗, Moamen S. Refatb,c
a Department of Chemistry, Faculty of Science, Mansoura University, Egypt
b Department of Chemistry, Faculty of Science, Port Said University, Port Said 42111, Egypt
c Department of Chemistry, Faculty of Science, Taif University, 888 Taif, Kingdom Saudi Arabia
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 May 2010
Received in revised form 8 August 2010
Accepted 8 September 2010
This work represents the elaborated investigation for the ligational behavior of the albendazole ligand
through its coordination with, Cu(II), Mn(II), Ni(II), Co(II) and Cr(III) ions. Elemental analysis, molar con-
ductance, magnetic moment, spectral studies (IR, UV–Vis and ESR) and thermogravimetric analysis (TG
and DTG) have been used to characterize the isolated complexes. A deliberate comparison for the IR
spectra reveals that the ligand coordinated with all mentioned metal ions by the same manner as a neu-
tral bidentate through carbonyl of ester moiety and NH groups. The proposed chelation form for such
complexes is expected through out the preparation conditions in a relatively acidic medium. The powder
XRD study reflects the amorphous nature for the investigated complexes except Mn(II). The conductivity
measurements reflect the non-electrolytic feature for all complexes. In comparing with the constants for
the magnetic measurements as well as the electronic spectral data, the octahedral structure was proposed
strongly for Cr(III) and Ni(II), the tetrahedral for Co(II) and Mn(II) complexes but the square–pyramidal
for the Cu(II) one. The thermogravimetric analysis confirms the presence or absence of water molecules
by any type of attachments. Also, the kinetic parameters are estimated from DTG and TG curves. ESR
spectrum data for Cu(II) solid complex confirms the square–pyramidal state is the most fitted one for
the coordinated structure. The albendazole ligand and its complexes are biologically investigated against
two bacteria as well as their effective effect on degradation of calf thymus DNA.
Keywords:
Albendazole
Thermal
Spectral
Biological
Molecular modeling
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
lates [12], Mn–binuclear complexes as a model to catalyses [13].
Recently, Ru–phenanthroline complexes with chelate ligands con-
Ligands containing heterocyclic aromatic units and their metal
complexes have extensive applications in many types of technology
[1,2]. Many heterocyclic compounds containing benzimidazoles,
which are the nucleolus of albendazole are a subject of interest
to medicinal chemistry because of the broad spectrum of their bio-
logical and pharmaceutical properties. Benzimidazole complexes
have been investigated for their antifungal, antibacterial [3,4],
antimicrobial [5,6], antiamoebic [7,8], antiparasitic [9] and anti-
tumor activities [10,11]. Although the presence of many studies
on benzimidazole complexes but the pharmacological or coordi-
native information about albendazole and some of its complexes is
absent in the literature. A considerable number of metal complexes
containing benzimidazole molecules is widely used in industry
such Cu(II)-methylene-bis(N-methyl) benzimidazole is used in
homopolimerization and co-polymerization of olefins and acry-
taining benzimidazoles and sulfur were reported to have a strong
DNA binding and high anti cancer activity, being more potent than
cisplatin against melanoma A375, and less toxic to normal cells [14].
Also, some biological studies have shown how analogous of ketone
are effective as inhibitors of cell death [15]. Through out the previ-
ous work we abstract the importance of benzimidazole moiety, so
the addition of other sites for the coordination (S and O) represents
in albendazole ligand may reveal an expected distinguish behav-
ior in coordination and application. In this study, we concern the
synthesis, structural characterization and molecular modeling for
the complexes with some metal ions in the first raw [Cu, Co, Ni, Cr
and Mn]. Furthermore, the antimicrobial activity of the free ligand
and its complexes against various pathogenic microorganisms was
evaluated.
2. Experimental
2.1. Reagents
∗
Corresponding author. Current address: Department of Chemistry, Faculty of
Education of Girls, Abha King Khalid University, Saudi Arabia.
Tel.: +966 0565370833.
Albendazole used in our study was obtained from the Egyp-
tian International Pharmaceutical Industrial Company (EIPICO). All
E-mail address: n elmetwaly00@yahoo.com (N.M. El-Metwaly).
1386-1425/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2010.09.021

N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 78 (2011) 196–204
197
Fig. 1. The structural and the modeling forms for the albendazole ligand.
Table 1
The molecular parameters of the ligand and its complexes.
The assignment of the theoretical parameters
The compound investigated
(1) [C12H15N3SO2]
The theoretical data
Total energy
Total energy
−67,064.4562148 (kcal/mol)
−106.874000637 (a.u.)
−3281.5352798 (kcal/mol)
−63,782.9209350 (kcal/mol)
−428,514.5365246 (kcal/mol)
361,450.0803098 (kcal/mol)
75.1927202 (kcal/mol)
5.285 (Debyes)
Binding energy
Isolated atomic energy
Electronic energy
Core–core interaction
Heat of formation
Dipole moment
Homo
−7.4858
Lumo
−1.8662
Total energy
Total energy
(2) [Cu (C12H15N3SO2)Cl2·H2O]
(5) [Co(C12H15N3SO2)ClOH]2H2O
(6) [Cr(C12H15N3SO2)Cl3H2O]3H2O
−116,199.6007872 (kcal/mol)
−185.175827994 (a.u.)
−3697.2963612 (kcal/mol)
−112,502.3044260 (kcal/mol)
−756,611.6461754 (kcal/mol)
640,412.0453882 (kcal/mol)
−90.2273612 (kcal/mol)
10.058 (Debyes)
Binding energy
Isolated atomic energy
Electronic energy
Core–core interaction
Heat of formation
Dipole moment
Homo
−8.1078
Lumo
−2.3574
Total energy
Total energy
−99,419.0368391 (kcal/mol)
−158.434300465 (a.u.)
−3762.7467911 (kcal/mol)
−95,656.2900480 (kcal/mol)
−644,522.8056797 (kcal/mol)
545,103.7688406 (kcal/mol)
−215.0697911 (kcal/mol)
7.341 (Debyes)
Binding energy
Isolated atomic energy
Electronic energy
Core–core interaction
Heat of formation
Dipole moment
Homo
−8.3501
Lumo
−1.4854
Total energy
Total energy
−102,019.8059128 (kcal/mol)
−162.578889288 (a.u.)
−3820.9944928 (kcal/mol)
−98,198.8114200 (kcal/mol)
−750,132.7568776 (kcal/mol)
648,112.9509648 (kcal/mol)
−170.6354928 (kcal/mol)
9.559
Binding energy
Isolated atomic energy
Electronic energy
Core–core interaction
Heat of formation
Dipole moment
Homo
−8.0914
Lumo
−1.6917
Table 2
Analytical and physical data for the Albendazole (HABZ) and its metal complexes.
Compound empirical formula (M. Wt.)
Color
Elemental analysis (%) calcd. (found)
C
H
N
M
Cl
[C12H15N3SO2] (265.33)
White
Olive green
Buff
Green
Green
Green
54.3 (55.0)
34.5 (34.6)
32.4 (30.9)
34.9 (34.2)
34.9 (33.4)
26.1 (26.2)
5.7 (5.5)
15.8 (16.8)
10.1 (4.3)
9.4 (9.1)
10.2 (10.6)
3.2 (2.7)
–
–
[CuCl2·H2O(C12H15N3SO2)] (417.80)
[MnCl2(C12H15N3SO2)]3H2O (445.22)
[NiCl·OH(H2O)2(C12H15N3SO2)] (412.52)
[CoCl·OH(C12H15N3SO2)]2H2O (412.76)
[CrCl3·H2O (C12H15N3SO2)]3H2O (495.76)
4.1 (4.1)
4.7 (4.5)
4.9 (4.3)
12.9 (13.6)
4.7 (4.8)
15.2 (15.1)
12.3 (12.0)
14.2 (14.6)
24.1 (23.6)
10.5 (10.8)
16.9 (16.5)
15.9 (16.3)
8.6 (9.0)
8.6 (8.8)
21.4 (21.8)
8.5 (8.1)

198
N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 78 (2011) 196–204
Fig. 2. (a) The structural form for two complexes (whereas: M = Co or Mn and X = OH or Cl, respectively), and (b) the structural form of Ni(II) complex.
Fig. 3. (a and b) The structural form and the modeling structure of the Cr(III) and Cu(II) complexes, respectively.
Table 3
Assignments of the IR spectral bands (cm−1) of HABZ and its metal complexes.
Compound
ꢀNH
ꢀNH
ꢀC
ꢀCI
ıNH
ıNH
2
ꢀC–S
ꢀM–N
ꢀM–O
1
2
1
N
O
(1) [C12H15N3SO2]
3149
3300
3299
3270
3255
3270
2956
2960
2958
2958
2966
2962
1629
1631
1627
1610
1648
1635
1710
1681
1693
1689
1710
1683
1525
1589
1530
1530
1536
1550
1444
1454
1452
1454
1463
1459
696
698
700
701
701
701
–
433
428
439
470
450
–
524
514
518
526
561
(2) [CuCl2·H2O (C12H15N3SO2)]
(3) [MnCl2(C12H15N3SO2)]3H2O
(4) [Ni·Cl·OH(H2O)2(C12H15N3SO2)]
(5) [Co·ClOH·(C12H15N3SO2)]2H2O
(6) [Cr·Cl3H2O(C12H15N3SO2)]3H2O
chemicals used for the study were of analytically reagent grade,
commercially available from Fulka and used without previous
purification as CoCl2·6H2O, CrCl3·6H2O, MnCl2·4H2O, NiCl2·6H2O
and, CuCl2·4H2O compounds, which represents the metal ions in
concern for the complexation.
was filtered off washed with methanol and diethyl ether and
finally dried in a vacuum desiccator. The [CoCl2(H2O)(HABZ)]3H2O
was synthesized [16] by dissolving 0.119 g (0.5 mmol) of Co(II)
chloride in ethanol (10 ml) and added to hot ethyl acetate solu-
tion (10 ml) of HABZ (0.133 g, 0.5 mmol). The blue solution was
refluxed for 4 h and the allowed to stand for 2 weeks. The
resulting blue powder was filtered off washed with ethanol and
dried in a vacuum. This complex is structurally similar with that
isolated in our study, but the molecular formulas are partially
different. This is accordance with the difference in synthesis pro-
cedures.
2.2. Synthesis of the complexes
The complexes were prepared by heating 1:1 molar ratio for the
ligand (0.2653 g, 1 mmol) with each metal chloride salt in methano-
lic medium in a water bath for 4–5 h under reflux. The precipitate
Table 4
Magnetic moments (BM) and electronic spectra bands (cm−1) of the complexes.
Complex
ꢁeff (BM)
d–d transition (cm−1
)
Intraligand and charge transfer (cm−1
)
Ligand field parameters
10 Dq (cm−1
)
B (cm−1
)
ˇ
(2)
(3)
(4)
(5)
(6)
1.85
5.90
2.83
4.45
3.72
11,628
24,154
14,662; 24,876
14,837; 16,502
16,286; 22,727
26,316; 36,496; 21,00
–
–
–
–
–
–
0.27
0.59
–
36,496; 34,014; 31,056; 26,042
36,496; 34,014; 31,645; 30,120
36,765; 34,482; 31,056
11,781.1
4750.7
–
279.6
570.8
–
36,496; 34,722; 31,446

N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 78 (2011) 196–204
199
Table 5
Thermogravimetric data of the investigated complexes.
Complex
Steps
Temp. range (◦C)
DTG peak (◦C)
Decomposed assignments
Weight loss found (calcd.%)
1st
2nd
3rd
Residue
1st
2nd
3rd
4th
Residue
1st
2nd
3rd
Residue
1st
2nd
3rd
4th
Residue
1st
2nd
112.4–234.6
235.5–429.7
528.6–787.0
168.8
323.9
681.3
−Cl2 + H2O
−C4H12OS
−C7H3N3
CuO + C
20.99 (21.28)
25.86 (25.90)
31.28 (30.91)
21.87 (21.91)
12.52 (12.14)
15.21 (15.93)
16.98 (17.11)
30.12 (29.91)
25.19 (24.92)
21.65 (21.45)
18.46 (18.87)
42.03 (42.23)
17.25 (18.11)
7.97 (8.73)
16.92 (16.83)
21.13 (21.85)
31.32 (31.53)
22.66 (21.06)
14.55 (14.52)
14.47 (14.30)
13.84 (13.61)
43.72 (43.83)
13.42 (13.71)
(2)
36.2–170.2
171.4–350.1
350.9–580.1
580.1–790.2
118.2
265.8
455.5
680.1
−3H2O
−Cl2
(3)
(4)
(5)
−C3H8S
−C7H7N3
MnO2 + 2C
−OH + 2H2O + 0.5 Cl2
−C3H8S
154.1–268.3
269.9–488.6
490.1–675.4
204.8
347.9
575.7
−C9H7N3O
NiO
30.8–148.4
149.2–250.7
300.1–510.1
511.6–785.1
71.5
191.1
381.9
672.8
−2H2O
−0.5 Cl2 + H2 + O2
−C4H10
S
−C7H4N3
CoO + C
35.2–173.3
174.7–349.1
350.5–518.7
520.3–779.4
103.0
246.6
434.8
636.0
−4H2O
−Cl2
(6)
3rd
4th
Residue
−Cl2 + CH3OH
−C11H11N3S
Cr + 0.5 O2
2.2.1. Antimicrobial activity
2.2.2. Genotoxicity
The ligand and its complexes were screened for their antimi-
crobial activity using the cup-diffusion technique [19] against
Bacillus thuringiensis as gram positive and Pseudomonas aeurogi-
nosa as gram negative bacteria. A 0.2 ml of the tested substance
(10 ␮g/ml) was placed in specified cup made in the nutrient
agar medium on which a culture of the tested bacteria has
been spread to produce uniform growth. After 24 h incuba-
tion at 37 ◦C, the diameter of inhibition zone was measured
as mm.
A solution of calf thymus DNA (2 mg) was dissolved in 1 ml of
sterile distilled water to a final concentration of 2 g/l. Stock con-
centrations of the ligand, metal chloride salts and their complexes
were prepared by dissolving 2 mg/ml in DMSO. An equal volume
of each compound and DNA were mixed thoroughly and kept at
room temperature for 2–3 h. The effects of the chemicals on the
DNA were analyzed by agarose gel electrophoresis. A 2 ␮l of loading
dye was added to 15 ␮l of the DNA–chemical mixture before being
loaded into the wall of an agarose gel. The loaded DNA–chemical
Table 6
Kinetic parameters using the Coats–Redfern (CR) and Horowitz–Metzger (HM) operated for the Albendazole complexes.
Complex
Step
Method
Kinetic parameters
E (J mol−1
)
A (S−1
)
ꢂS (J mol−1 K−1
)
ꢂH (J mol−1
)
ꢂG (J mol−1
)
r
1st
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
HM
CR
4.08 × 104
4.48 × 104
3.08 × 104
3.46 × 104
1.02 × 105
1.23 × 105
2.43 × 105
2.78 × 105
5.36 × 104
6.62 × 104
8.78 × 104
9.37 × 104
1.62 × 105
1.7 × 105
1.90 × 102
1.38 × 103
6.19 × 10−1
3.13
−2.05 × 102
−1.88 × 102
−2.55 × 102
−2.41 × 102
−1.98 × 102
−1.72 × 102
−1.69 × 101
−2.46 × 101
−1.84 × 102
−1.49 × 102
−1.6 × 102
3.71 × 104
4.11 × 104
2.59 × 104
2.96 × 104
9.45 × 104
1.15 × 105
2.36 × 105
2.70 × 105
4.96 × 104
6.23 × 104
8.26 × 104
8.85 × 104
1.55 × 105
1.63 × 105
6.71 × 103
1.12 × 104
7.96 × 104
8.48 × 104
8.19 × 104
9.0 × 104
1.27 × 105
1.24 × 105
1.78 × 105
1.73 × 105
2.83 × 105
2.79 × 105
2.5 × 105
0.9999
0.9998
0.9988
0.9992
0.9999
0.9997
0.9999
0.9993
0.9992
0.9994
0.9994
0.9997
0.9999
0.9999
0.9992
0.9996
0.9999
0.9999
0.9999
0.9998
0.9993
0.9995
0.9999
0.9999
0.9996
0.9995
0.9992
0.9993
2nd
3rd
1st
(2)
(3)
(4)
9.24 × 102
2.17 × 104
2.39 × 1012
3.52 × 1014
2.57 × 103
1.55 × 105
5.81 × 104
5.68 × 105
3.85 × 107
2.22 × 108
3.53 × 10−2
4.77 × 10−1
1.88 × 107
1.18 × 108
2.95 × 104
2.81 × 105
3.30 × 103
2.38 × 105
4.76
2.49 × 105
1.37 × 105
1.34 × 105
1.82 × 105
1.76 × 105
2.47 × 105
2.43 × 105
1.01 × 105
9.8 × 104
1st
2nd
3rd
1st
−1.41 × 102
−1.08 × 102
−9.38 × 101
−2.74 × 102
−2.52 × 102
−1.09 × 102
−9.4 × 101
9.57 × 103
1.4 × 104
8.35 × 104
8.87 × 104
8.73 × 104
9.55 × 104
3.62 × 104
1.39 × 105
2.31 × 104
3.08 × 104
2.18 × 104
3.13 × 104
3.91 × 104
5.01 × 104
1.3 × 105
2nd
3rd
4th
1st
1.28 × 105
1.90 × 105
1.86 × 105
2.05 × 105
2.75 × 105
1.08 × 105
1.05 × 105
1.52 × 105
1.50 × 105
2.1 × 105
(5)
(6)
−1.66 × 102
−1.47 × 102
−1.87 × 102
−1.52 × 102
−2.34 × 102
−2.06 × 102
−2.6 × 102
2.84 × 104
1.32 × 105
2.0 × 104
1.29 × 102
2.96 × 10−1
4.96
2.77 × 104
1.75 × 104
2.70 × 104
3.32 × 104
4.42 × 104
2nd
3rd
−2.36 × 102
−2.51 × 102
−2.30 × 102
1.19
HM
1.51 × 101
2.07 × 105

200
N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 78 (2011) 196–204
the soluble complexes using Jenway 4010 conductivity meter.
DrTGA
a
4
2
0
1
The X-ray diffraction patterns (XRD) were obtained on Pikagu
diffractometer using Cu/K␣ radiation. The infrared spectra, as KBr
discs, were recorded on a Mattson 5000 FTIR Spectrophotometer
(400–4000 cm−1) at Mansoura University. The electronic and 1H
NMR (200 MHz) spectra were recorded on UV2 Unicam UV/Vis, and
a Varian Gemini Spectrophotometers, respectively in Mansoura and
0
DTG
Cairo universities. The effective magnetic moments were evaluated
ꢀ
-1
-2
at room temperature by applying ꢁeff = 2.828 XMT, where XM is
the molar susceptibility corrected using Pascal’s constants for the
diamagnetism of all atoms in the ligand using a Johnson Matthey
magnetic susceptibility balance. The thermal studies were carried
out on a Shimadzu thermogravimetric analyzer at a heating rate of
10 ◦C min−1 under nitrogen. ESR spectrum of solid 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 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. The biological study
was carried out in Molecular Biology Center in Botany department
in Mansoura University Egypt.
TG
0
200
400 600
Temp [oC]
800
DrTGA
3
2
b
4
TG
2
DTG
1
0
-2
-4
0
3. Results and discussion
The elemental analysis and some physical characteristics are
summarized in Table 2. All the isolated complexes are stable in air,
having high melting points, insoluble in H2O and most organic sol-
vents except DMSO and DMF. They are completely soluble except
the Cr(III) and Ni(II) complexes. The molar conductivity mea-
surements for (1.0 × 10−3 mol) in DMSO solvent are found with
the range of non-conducting feature. This elucidates the proposal
of analysis data for the presence of conjugated anion covalently
attached with the central metal ion in the investigated complexes.
-1
0
200
400
600
800
Temp [oC]
DrTGA
3
2
1
0
1
c
0
DTG
-1
-2
-3
3.1. IR spectra of the complexes
TG
Essential IR bands of the ligand and its complexes are tab-
ulated in Table 3. In [CuCl2·H2O(HABZ)], [MnCl2(HABZ)]3H2O,
[NiCl·OH·2H2O(HABZ)],
[CoCl·OH(HABZ)]2H2O
and
[CrCl3·H2O(HABZ)]3H2O complexes, the mode of coordina-
tion abstracted from a comparison of the spectra for the ligand
and its complexes. This reflects that, the coordinated ligand is
displaying the same manner in coordination with all metal ions
as neutral bidentate through the oxygen of carbonyl ester group
beside the NH one. The ligand behavior in the isolated complexes
is satisfactory and acceptable due to the stereo structure of the
arrangement of active donors with each others. This permits the
bidentate attachment through the more electron dense groups.
The obscure of the amide carbonyl deprotonation is supported
by the preparation conditions represented in the relatively acidic
medium of the precipitation. The mode of coordination proposed
is confirmed through the molecular modeling of the most stable
structure applying the hyperchem program. The IR spectrum of
the ligand displays the ꢀ(C O) band at 1710, ␦NHs at 1525, 1444,
ꢀ(C–S) at 696 cm−1, and ꢀ(C N) at 1629 cm−1. The lower shift
observed clearly in ꢀ(C O) band appeared at ≈1680 cm−1 in each
complex spectrum supports its coordination in neutral state and
represents the first side in coordination [22]. Also, more or less
unshift observed for ꢀ(C N), ꢀ(C–S) supports their siding out from
complexation. The higher shift observed in ꢀ and ␦ NH1 bands
supports their coordination after the intraligand hydrogen bonding
disappearance. The appearance of new bands in all complexes
spectra assigned to ꢀM–O, ꢀM–N and ꢀM–Cl supports the pro-
posed coordination sites surrounds the central atoms. The water
0
200
400
600
800
Temp [oC]
Fig. 4. (a) The TG and DTG curves of the Cu(II) complex thermogravimetric analysis
and (b and c) of Ni(II) and Co(II) complexes, respectively.
mixtures were fractionated by electrophoresis, visualized by UV
and photographed.
2.3. Molecular modeling
An attempt to obtain an acceptable insight about the molecular
modeling structure of the ligand (Fig. 1) and some of its complexes
was done. The geometry optimization and conformational analysis
has been performed in Table 1 by the use of MM+ [20] force-field
as implemented in hyperchem 5.1 [21].
2.4. Physical measurements
Carbon, H and N were analyzed at the Microanalytical unit
of Cairo University. Cu(II), Mn(II), Co(II), Ni(II) and Cr(III) were
determined by complexometric titrations [17], but the conju-
gated chlorine was estimated gravimetrically [18] and the data
reflect the high conformity. The molar conductivities of freshly
prepared 1.0 × 10−3 mol/cm3 DMSO solutions were measured for

N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 78 (2011) 196–204
201
of hydration molecules proposed in the Mn(II), Co(II) and Cr(III)
complexes caused a little broad suffered in the higher field area
(3400–3480 cm−1), but the coordinated water displays bands at
≈720, ≈600, ≈630 cm−1 assigned for ␦r, ␦w and ␦t H2O molecules.
It should be mentioned here, that these assignments for both the
bond stretches and angular deformation of the coordinated water
molecules fall in the frequency regions reported for other related
complexes [22].
for the interaction between Ni(II) and ligand sites [26] of coor-
dination. The lower B value is reflecting the highly changeable
in nuclear charge for the cation. The parameter ˇ is highly low,
this supporting the covalent character for the coordination with
N and O atoms in comparing with that reported for NiN6 and
NiO6. The [CrCl3(H2O)(HABZ)]3H2O complex (Fig. 3a) exhibit three
4
bands at 31,446, 22,727 and 16,286 assigned to 4A2g(F) → T1g(P),
4
4
4A2g(F) → T1g(F) and 4A2g(F) → T2g(P) transitions, respectively.
The magnetic moment (3.72 BM) is well within the range for three
unpaired electrons. The electronic spectral bands beside the mag-
netic moment support strongly the octahedral for the geometry
around the Cr ion. The electronic spectrum of [CuCl2·H2O(HABZ)]
olive green complex (Fig. 3b) does not reveal any absorption bands
at 20,000 cm−1 for S → Cu charge transfer transition [27], which
supports its absence from coordination for the square-based pyra-
mid geometry in a close to C4v group. (For interpretation of the
references to color in text, the reader is referred to the web version
3.2. Spectral and magnetic studies
The magnetic measurements for the isolated complexes and
their significant electronic spectral bands are presented in Table 4.
The spectra for all complexes under investigation were carried out
in DMF solution. The spectrum of a highly diluted solution of the lig-
and reveals bands in UV region (34,246 and 33,112 cm−1) assigned
for intraligand transitions (␲ → ␲* and n → ␲*, respectively). The
magnetic moment of [MnCl2·(HABZ)]3H2O complex is 5.9 BM, as a
high spin complex for d5 configuration, near the spin only magnetic
moment value (5.8 BM). The electronic transition band at 24,154
is clearly indicating the tetrahedral coordination around man-
ganese(II) for A61 → A14(g) transition [23]. The electronic spectrum
of green [CoCl·OH(HABZ)]2H2O complex (Fig. 2) exhibits one char-
2
of the article.) There are three spin allowed transitions as 2B1 → A1,
2
2
2B1 → B2 and 2B1 → E1 usually very difficult to resolve them into
separate bands due to the very low energy difference between
these bands, so appeared at 11,628 cm−1. Band at ≈21,000 cm−1
is attributed to O → Cu charge transfer transition. The intense band
at ≈26,316 cm−1 is attributed to N → Cu charge transfer transition.
The magnetic moment of the complex [1.85 BM] within the normal
range reported for d1 systems and also, reflects the absence of any
metal–metal interaction for mononuclear complex. All the bands at
higher region ≈36,000–34,000 cm−1 assigned to intraligand ␲ → ␲*
and n → ␲* transitions, suffered marginal shift from that of their
corresponding free ligand. However, some charge transfer bands
may also be present in this region for the complexes [26].
4
acteristic band at 14,837 cm−1 attributed to 4A2→ T1(P) transition
referring to tetrahedral structure. The shoulder at 16,502 cm−1 may
be due to the spin coupling [24] also the magnetic moment value
(4.45 BM) within the range reported for such structures. The green
color is considered the additional evidence for the tetrahedral pos-
tulation. The ligand field parameters (B, ˇ and 10 Dq) are calculated,
according to equations reported for tetrahedral Co(II) complexes:
ꢁ
ꢂ
1 − 4ꢃ
3.3. Thermal analysis
ꢁeff = 3.87
ꢃ = −178 cm−1
10 Dq
The decomposition stages, temperature ranges, proposed
decomposition products as well as the calculated and found weight
loss percentages of the complexes are presented in Table 5. In
most investigated complexes, the first decomposition stage is
attributed to the removal of hydrated water molecules. The kinetic
parameters for the thermal behavior of the complexes are cal-
culated in Table 6. In [CuCl2·H2O(HABZ)] complex, the TG and
DTG curves show three decomposition stages (Fig. 4a) started at
112.4 ◦C and ended at 787.04 ◦C. The complex reveals a relative
thermal stability up to 112 ◦C and followed by a sudden decom-
position by a weight loss 20.99 (calcd.21.28%) corresponding to
the elimination of coordinated H2O and Cl2 molecules. The second
exothermic decomposition stage started at 235.5 ◦C corresponding
to the removal of C4H12OS as a terminal organic moiety by 25.86
(calcd.25.90%) weight loss. The final degradation stage started at
528.6 ◦C is translated to the removal of another organic moiety
(C7H3N3) by 31.28 (calcd.30.91) weight loss lefts CuO at ≈800 vC
as a residual polluted with carbon atom. The gradual degradation
stages for [MnCl2(HABZ)]3H2O complex started at 36.17 ◦C and
attributed to the dehydration for 3H2O by 12.52 (calcd.12.14%)
weight loss. The removal of Cl2 in the following decomposition
stage started at 171.42 ◦C by 15.21 (calcd.15.93%) weight loss. The
removal of major organic part in coordinator [C3H8S + C7H7N3] in
third and fourth steps started as 350.91 and 580.12 ◦C by 16.98
(calcd.17.11%) and 30.12 (calcd.29.92%) weight loss, respectively.
The final residue is MnO2 polluted with carbon atoms. The grad-
ual degradation stages representing in TG and DTG curves for
[NiCl·OH·2H2O (HABZ)] complex (Fig. 4b) started at 154.1 ◦C for the
first degradation stage after legal thermal stability is attributed to
the removal of 2H2O + 0.5Cl2 + OH, by 21.65 (calcd.21.45%) weight
loss. The removal of C3H8S + C9H7N3O as a whole organic moi-
eties in the two following steps started at 269.92 and 490.15 ◦C
by 18.46 (calcd.18.87%) and 42.03 (calcd.42.23%) weight loss. The
4(ꢀ3 − 15 Dq)2 − 10 Dq2
B =
60(ꢀ3 − 15 Dq) − 18ꢂ
ꢀ1 = 10 Dq
The calculated values (570.78, 0.588 and 4750.75) are found in
the range reported for the suggested structure. The ˇ value (0.59)
indicates more covalent character for Co(II)–ligand bonds. The
transition for 4A2 → T2(ꢀ1) is calculated to be 4750.7 cm−1. The
4
magnetic moment of [NiCl·OH·2H2O(HABZ)] complex (Fig. 2b) is
found to be 2.83 BM within the range of six-coordinate Ni(II) com-
plex at room temperature and corresponding to the two unpaired
electrons. The spectral bands for the d–d transition appeared
at 14,662 and 24,876 cm−1 attributed to 3A2g(F) → T1g(F)(ꢀ2)
3
3
and 3A2g → T1g(P)(ꢀ3), transitions, respectively in an octahedral
geometry. The Ni(II) complex reflects the trend of increasing the
size of the ligand the lower shift in the energy of the maxima
d–d bands, presumably due to weakening of the coordinate bond
with increased bulkiness of the ligand [25]. The spectrochemical
parameters 10 Dq, B and ˇ are calculated applying the following
equations:
(ꢀ2 + ꢀ3)
ꢂ = 10 Dq =
− 5 B
3
ꢁ
ꢂ
ꢁ
ꢂ
ꢀ2 − ꢀ3
ꢀ2 − ꢀ3
340B2 − 28
B +
2 − (ꢀ3 − ꢀ2)2 = 0
3
3
for Ni(II) octahedral systems. The values are found to be 11,781.1,
279.6 and 0.27. The 10Dq value (11,781.1 cm−1) is found within
the normal range for 3A2g → T2g(F)(ꢀ1) transition, the B value
3
is considered to be ≈27% indicating highly covalent character

202
600
N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 78 (2011) 196–204
parameters. Many authors [28–31] have discussed the advantages
of this method over the conventional isothermal method. The rate
of the decomposition process can be described as the product of
two separate functions of temperature and conversion [29], using:
400
200
0
d␣
dt
= k(T)f (˛)
(1)
where ˛ is the fraction decomposed at time t, k(T) is the tem-
perature dependant function and f(˛) is the conversion function
dependent on the mechanism of decomposition. The temperature
dependent function k(T) is of Arrhenius type and can be considered
as the rate constant k,
K = Ae−E∗/RT
(2)
where R is the gas constant in (J mol−1 k−1) substituting Eq. (2) into
0
20
40
60
80
Eq. (1) we get this equation:
Fig. 5. The XRD diagram of the Mn(II) albendazole complex.
ꢃ
ꢄ
d␣
dT
A
=
f (˛)
(3)
ϕe−E∗/RT
residual part is NiO by 17.25 (calcd.18.11%) weight. The gradual
degradation stages representing in TG and DTG curves for [CoCl·OH
(HABZ)]2H2O complex (Fig. 4c) started with sudden decomposi-
tion at low temperature 30.85 ◦C referring to the expel of two
hydrated H2O molecules by 7.97 (calcd.8.73%) weight loss. The
second decomposition step started at 149.17 ◦C attributed to the
removal of H2 + O2 + 0.5Cl2 by 16.92 (calcd.16.83%) weight loss.
The final steps reveal the removal of organic part (C4H10S and
C7H4N3) by 21.13 (calcd.21.85%) and 31.32 (calcd.31.53%) weight
loss. The residual part is CoO contaminated with carbon atom. The
gradual degradation stages representing in TG and DTG curves for
[CrCl3(H2O)(HABZ)]3H2O complex started with sudden decompo-
sition at 35.17 ◦C reflecting the thermal instability referring to the
hydrated water molecules expelled in the first step beside the coor-
dinated one by 14.55 (calcd.14.52%) weight loss. The removal of Cl2
molecule by 14.47 (calcd.14.30%) in the second step started is car-
ried out at 174.7 ◦C. The removal of 0.5Cl2 + CH3OH molecules at the
third step started at 350.5 ◦C by 13.84 (calcd.13.61%) weight loss.
The C11H11N3S organic moiety is expelled completely at 779.4 ◦C
as the final part by 43.72 (calcd.43.83%) weight losses. The residual
part represents in Cr + 0.5O2 by 13.42 (calcd.13.71%) weights.
where ϕ is the linear heating rate dT/dt. From the integration and
approximation, this equation can be obtained in the following form:
ꢅ
ꢆ
−E∗
AR
ln g(˛) =
+ ln
RT
ϕE∗
where g(˛) is a function of ˛ dependant on the mechanism of the
reaction. The integral on the right hand side is known as tempera-
ture integral and has no closed for solution. So, several techniques
have been used for the evaluation of temperature integral. Most
commonly used methods for this purpose are the differential
method of Freeman and Carroll [28] integral methods of Coat and
Redfern [30], the approximation method of Horowitz and Met-
zger [35]. The kinetic parameters for the albendazole complexes
are evaluated using the following methods and the results are in
good agreement (Table 6) with each other. The used methods are
discussed briefly:
3.4.1. Coats–Redfern equation
The equation is a typical integral method, represented as:
˛
T
2
ꢁ
ꢂ
d˛
(1 − ˛)n
A
ϕ
−E∗
=
exp
dt
3.4. Kinetic studies
RT
0
T
1
In order to assess the effect of the metal ion on the thermal
behavior of the complexes, the order n, and the heat of activa-
tion E of the various decomposition stages were determined from
the TG and DTG. Several equations [28–35] have been proposed as
means of analyzing a TG curves and obtaining values for kinetic
For convenience of integration the lower limit T1 is usually taken
as zero. This equation on integration gives:
ꢅ
ꢆ
ꢁ
ꢂ
− ln 1 − ˛
AR
E∗
(
)
ln
= ln
−
T2
ϕE∗
RT
Fig. 6. Electrophoretic mobility of Calf thymus DNA treated with HABZ (lane 1), Cr complex (lane 2), Co complex (lane 3), Cu complex (lane 4), Mn complex (lane 5), Ni
complex (lane 6), lanes from 7 to 10 represents the chloride salts of each metal ion used except Cr, respectively, the final represent control calf thymus DNA sample.

N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 78 (2011) 196–204
203
Table 7
Table 8
ESR data of Cu(II) complex at room temperature.
The values of zone inhibition of bacteria for the ligand and its metal complexes.
2
Complex
(2)
g((
g
gav
A(( × 10−4 (cm−1
)
G
˛
ˇ2
Compound
Zone of inhibition
(mm)
⊥
2.093
2.03
2.062
160
3.1
0.59
0.27
Bacillus
Pseudomonas
thuringiensis Gram
(+) bacteria
aeuroginosa Gram
(−) bacteria
A plot of ln[ − ln(1 − ˛)/T2] (LHS) against 1/T was drawn. E* is the
energy of activation in J mol−1 and calculated from the slop and A
is (S−1) from the intercept value. The entropy of activation ꢂS* in
(J K−1 mol−1) was calculated by using the equation:
(1) HABZ
(2)
(3)
(4)
(5)
0
16
0
20
16
16
0
0
0
0
0
0
ꢁ
ꢂ
Ah
ꢂS∗ = R ln
(4)
(6)
KBTs
where kB is the Boltzmann constant, h is Plank’s constant and Ts is
state [39]. This hyperfine interaction observed for the complex is
attributed to the interaction with nitrogen and oxygen nuclei adja-
cent to copper ion. Kivelson and Neiman [40] have reported the
g11 value <2.3 for covalent character of the metal–ligand bond and
>2.3 for ionic character. Applying this criterion the covalent char-
acter of the metal–ligand bond in the complex under study can be
predicated. The trigonal bipyramidal and square–pyramidal have a
the DTG peak temperature [36].
3.4.2. Horowitz–Metzger equation
The authors derived the relation:
E
ln − ln(1 − ˛) =
ꢄ
(5)
[
]
RTm
where ˛ is the fraction of the sample decomposed at time t and
ꢄ = T − Tm
ground state configuration 2B1 (unpaired electron in dx
orbital)
2
2
−y
.
and 2A1 (unpaired electron in dz orbital), respectively. Molecular
2
A plot of ln − ln(1 − ˛) against ꢄ, was found to be linear, from
[
]
orbital coefficients, ˛2 (A measure of the covalence of the in-plane
␴-bonding between a copper 3d orbital and the ligand orbital) and
the slope of which E, was calculated and Z can be deduced from the
relation:
ˇ
2 (covalent in-plane ␲-bonding), were calculated by using the fol-
ꢁ
ꢂ
lowing equations [40–44], where ˛2 = 1 indicates complete ionic
character, whereas ˛2 = 0.5 denotes 100% covalent bonding, with
the assumption of negligibly small values of the overlap integral.
Eϕ
RTm2
E
Z =
exp
(6)
RTm
where ϕ is the linear heating rate, the order of reaction, n, can be
2
calculated from the relation:
˛
= ((A///0.036) + (g// − 2.0023) + 3/7(g⊥ − 2.0023) + 0.04
n = 33.64758 − 182.295˛m + 435.9073˛2m − 551.157˛m3
ˇ2 = (g// − 2.0023)E/ − 8ꢃ˛2,
+ 357.3703˛4m − 93.4828˛5m
(7)
where ꢃ = −828 cm−1 for the free copper ion and E is the elec-
tronic transition energy. From Table 7, the ˛2 and ˇ2 values indicate
that the in-plane ␴-bonding and the in-plane ␲-bonding are highly
covalent. The lower value of ˇ2 compared to ˛2 indicates that the in-
where ˛m is the fraction of the substance decomposed at Tm
.
The entropy of activation, ꢂS*, was calculated from Eq. (4). The
enthalpy of activation ꢂH*, and Gibbs free energy, ꢂG*, were calcu-
lated from; ꢂH* = E* − RT and ꢂG* = ꢂH* − TꢂS*, respectively. The
data tabulated reveals the following observations: (i) the activa-
tion energy E, increases somewhat through the degradation steps
revealing the high stability of the remaining part suggesting a high
stability of complexes characterized by their covalence, (ii) the
negative ꢂS* values, indicates the activated fragment has ordered
structures, (iii) the positive ꢂH* reflects the endothermic decom-
position process, (iv) the positive ꢂG* singe reveals that the free
energy of the final residue is higher than that of the initial com-
pound, and the decomposition stages are non-spontaneous. This
results from increasing TꢂS* clearly from one step to another which
override the values of ꢂH* reflecting that the rate of removal of the
subsequent species will be lower than that of the precedent one
[36].
plane ␲-bonding is more covalent than the in-plane ␴-bonding. The
2
˛
value for copper(II) complex indicates a considerable covalency
in the bonding between the Cu(II) ion and the ligand.
3.6. Molecular modeling of the ligand and some of its complexes
The atomic numbering scheme and the theoretical geometry
structures for the ligand and some of its metal complexes are cal-
culated. The molecular parameters: total energy, binding energy,
isolated atomic energy, electronic energy, heat of formation, dipole
moment, HOMO and LUMO were calculated and represented in
Table 1. A comparison between the bond length of the ligand and
its complexes is illustrated. The length of C Oligand and C–N bonds
are found high in complexes than that in the free ligand indicating
their participation in complexation. However, the length of C
bond does not change.
N
3.5. ESR spectrum
The spin Hamiltonian parameters and the G value of solid state
Cu(II) complex are calculated (Table 7). Its ESR spectrum displayed
axially symmetric g tensor parameters with g11 > g⊥ > 2.0023 indi-
3.7. Ray powder diffraction of some complexes
X-ray powder diffraction pattern in the 10◦ < 2Â < 70◦ of the
Cu(II), Cr(III) and Mn(II) complexes were carried in order to give
an insight about the lattice dynamics of the compounds. The X-ray
powder diffraction obtained reflects a shadow on the fact that each
solid represents a definite compound of a definite structure which
is not contaminated with starting materials. This identification of
the complexes was done by the known method [45]. Such facts sug-
gest that the Cu(II) and Cr(III) complexes are amorphous but Mn(II)
is nanocrystalline (Fig. 5).
cating that the dx
orbital as a ground state [37]. In axial
2
2
−y
symmetry the g-values are related to the G-factor by the expression,
G = (g11 − 2)/(g⊥ − 2) = 4, which measures the exchange interaction
between copper centers in the solid. According to Hathaway [38], if
the value of G is greater than 4, the exchange interaction between
copper(II) centers in the solid state is negligible, whereas when it is
less than 4, a considerable exchange interaction exists in the solid
complex. The G value is less than 4 (3.1), this supports the little pres-
ence of exchange coupling between copper(II) centers in the solid

204
N.M. El-Metwaly, M.S. Refat / Spectrochimica Acta Part A 78 (2011) 196–204
3.8. Biological activity
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3.8.1. Eukaryotic DNA degradation effect
The DNA degradation behavior under the effect of the ligand,
metal salts and their complexes is examined. A deliberate compar-
ison reflects the completely difference in the results obtained after
mixing the calf thymus DNA with the ligand and with each complex.
The results shown in the photos (Fig. 6) the ligand and DMSO did
not degrade the DNA and the DNA migration was close to the top of
the gel. Whereas, all the complexes degraded the DNA almost com-
pletely in comparing with their original chloride salts. This behavior
is illustrated referring to the direct contact of the complexes with
the DNA which able to degrade it.
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3.8.2. Antimicrobial activity
The ligand and its complexes were tested against Gram-positive
(Bacillus thuringiensis) and Gram-negative (Pseudomonas aeurogi-
nosa) bacteria for their antibacterial activities (Table 8) using the
disc diffusion sensitivity testing method. The Ni(II), Cu(II), Co(II)
and Cr(III) complexes inhibited the growth of G +ve Bt bacterium,
whereas all the complexes were non-effective against the G −ve
bacterium. The best antibacterial complex is the Ni(II) one which
showed moderate antibacterial activity, while Cr(III), Co(II) and
Cu(II) complexes showed weak activity against Gram-positive bac-
terium. The negative results can be attributed either to the in ability
of the complexes to diffuse into the Gram-negative or the Gram-
positive bacterium and hence unable to interfere with its biological
activity or they can diffuse and inactivated by unknown cellular
mechanism by the bacterium. The positive results suggested the
diffusion of the complexes inside the Bt cells and killed bacteria as
indicated by the zones of inhibition diameter.
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