Cobalt(II) complexes based on (1-methyl-1H-benzo[d]imidazol-2-yl) methanol derivative: synthesis, crystal structure, spectroscopy, DFT calculations, and antioxidant activity

Article abstract of DOI:10.1080/00958972.2018.1428742

In this paper, we present a combined experimental and computational study of two new cobalt(II) complexes as [Co(Hmbm)₂(OAc)₂] and [Co(Hmbm)₂(H₂O)₂]Cl₂ (Hmbm = (1-methyl-1H-benzo[d]imidazol-2-yl)methanol). Both complexes were characterized by FT-IR and UV–vis spectroscopy, elemental analysis, and single-crystal X-ray crystallography. The molecular geometries, electronic transitions, and vibrational frequencies of the two complexes and the ligand (Hmbm) in the ground state have been calculated using global hybrid (B3LYP) and range-separated hybrid (CAM-B3LYP) density functional. Qualitative description of excited states and charge transfer character of electronic transitions states were carried out by plotting the Natural Transition Orbitals (NTOs) for main states, and were assigned to LMCT. The ligand and its Co(II) complexes have been evaluated for their potential as DPPH radical scavengers.

Full text of DOI:10.1080/00958972.2018.1428742

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Cobalt(II) complexes based on (1-methyl-1H-
benzo[d]imidazol-2-yl) methanol derivative:
synthesis, crystal structure, spectroscopy, DFT
calculations, and antioxidant activity
Anfel Benhassine, Houssem Boulebd, Barkahem Anak, Abdelmalek
Bouraiou, Sofiane Bouacida, Mustapha Bencharif & Ali Belfaitah
To cite this article: Anfel Benhassine, Houssem Boulebd, Barkahem Anak, Abdelmalek Bouraiou,
Sofiane Bouacida, Mustapha Bencharif & Ali Belfaitah (2018) Cobalt(II) complexes based on (1-
methyl-1H-benzo[d]imidazol-2-yl) methanol derivative: synthesis, crystal structure, spectroscopy,
DFT calculations, and antioxidant activity, Journal of Coordination Chemistry, 71:2, 311-328
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Journal of Coordination Chemistry, 2018
Vol. 71, no. 2, 311–328
https://doi.org/10.1080/00958972.2018.1428742
Cobalt(II) complexes based on (1-methyl-1H-benzo[d]
imidazol-2-yl) methanol derivative: synthesis, crystal
structure, spectroscopy, DFT calculations, and antioxidant
activity
Anfel Benhassinea, Houssem Boulebda, Barkahem Anakb, Abdelmalek Bouraiouc,
Sofiane Bouacidac,d, Mustapha Bencharifb and Ali Belfaitaha
alaboratoire des Produits naturels d’origineVégétale et de synthèse organique, faculté des sciences exactes,
université des frères mentouri-Constantine, Constantine, algeria; blaboratoire de chimie des matériaux
de Constantine, faculté des sciences exactes, Campus de Chaabatersas, université des frères mentouri-
Constantine, Constantine, algeria; cunité de recherche de Chimie de l’environnement et moléculaire
d
structurale, faculté des sciences exactes, université des frères-mentouri, Constantine, algeria; faculté des
sciences exactes, département sciences de la matière, université oum el Bouaghi, Constantine, algeria
ABSTRACT
ARTICLE HISTORY
received 2 october 2017
accepted 3 January 2018
In this paper, we present a combined experimental and computational
study of two new cobalt(II) complexes as [Co(Hmbm)2(OAc)2] and
[Co(Hmbm)2(H2O)2]Cl2 (Hmbm = (1-methyl-1H-benzo[d]imidazol-
2-yl)methanol). Both complexes were characterized by FT-IR and
UV–vis spectroscopy, elemental analysis, and single-crystal X-ray
crystallography. The molecular geometries, electronic transitions,
and vibrational frequencies of the two complexes and the ligand
(Hmbm) in the ground state have been calculated using global hybrid
(B3LYP) and range-separated hybrid (CAM-B3LYP) density functional.
Qualitative description of excited states and charge transfer character
of electronic transitions states were carried out by plotting the Natural
Transition Orbitals (NTOs) for main states, and were assigned to LMCT.
The ligand and its Co(II) complexes have been evaluated for their
potential as DPPH radical scavengers.
KEYWORDS
2-substituted benzimidazole;
Cobalt(ii) complexes; X-ray
crystal structures; dPPh, dft
calculations
CONTACT mustapha Bencharif
ali.belfaitah@umc.edu.dz
m_bencharif@umc.edu.dz; ali Belfaitah
abelbelfaitah@yahoo.fr,
supplemental data for this article can be accessed at https://doi.org/10.1080/00958972.2018.1428742.
© 2018 informa uK limited, trading as taylor & francis Group

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A. BENHASSINE ET AL.
1. Introduction
Over recent decades, metal coordination compounds have shown increased interest because
of their potential as functional materials and their structural diversity. Structures of com-
plexes can be designed depending on the nature of metal ion, atom-donor connecting
ligand, and reaction conditions [1]. Recently, the coordination chemistry of benzimida-
zole-based ligands has rapidly developed, as illustrated by an increasing number of reports
highlighting their properties as versatile N-donors exhibiting various coordination modes
[2–5].
The benzimidazole core is a privileged substructure and present in a number of bio-mol-
ecules including DNA purine bases and vitamin B12 as well as in a range of therapeutic
agents [6]. This heterocyclic scaffold is also found in potent antifungal [7], antimicrobial [8],
anti-hypertensive [9], anti-HIV [10], antioxidant, and antitumor agents [11, 12]. The coordi-
nation of bioactive benzimidazoles and related compounds, with transition metal ions, often
results in discovery and/or enhancement of their biological properties [13, 14]. Transition
metal complexes of benzimidazole derivatives remain an important and popular area of
research due to their simple synthesis, versatility, and diverse range of medicinal applications
such as anticancer agents [15], antioxidant [16], and enzyme inhibitors [17, 18].
A number of interesting reports related to the synthesis and characterization of coordi-
nation compounds of 2-substituted benzimidazole bearing additional nitrogen, oxygen, or
sulfur atoms as potential bonding sites toward transition metal ions have been described
by several groups [19]. These ligands provide a variety of metal-ligand coordination modes.
In some cases, bidentate ligands give a six-coordinate compound by inclusion of the central
ion in a planar delocalized system [20]. In four-coordinate compounds, type [M(L)2X2,
M(II)=Co, Zn, Cu, L=ubz (uroylbenzimidazole), mbc (2-methylcarbamatebenzimidazole), X=Cl,
Br], the central ion acquires a tetrahedral geometry [21–23]. The selection of the anion is
important because the topology of the resulting structure can be controlled by changing
the structure of the anion even for structures containing the same ligand and metal ion [24].
Following our previous work related to the use of (benz)imidazole as a medicinal scaffold
for the synthesis of new compounds with biological interest [25–28], we describe in this
paper the synthesis, characterization, and antioxidant evaluation of new cobalt(II) coordina-
tion complexes derived from (1-methyl-1H-benzo[d]imidazol-2-yl)methanol. Different phys-
icochemical analyses were used to characterize the new synthesized complexes including
elemental analysis, FT-IR and UV–vis spectroscopy and single-crystal X-ray analysis. The exper-
imental results have been compared with computational studies by DFT method using global
hybrid (B3LYP) and range-separated hybrid (CAM-B3LYP) density functional. To assign the
bands observed in electronic spectra, theoretically possible electronic transitions were deter-
mined using TD-DFT calculations. The antioxidant potential of the two cobalt(II) complexes
and Hmbm has been investigated and evaluated by DPPH free radical scavenging method.
2. Experimental
2.1. Measurements and materials
IR spectra were recorded by means of a Shimadzu FT IR-8201 PC spectrophotometer with
KBr pellets. UV–visible spectra were recorded on a UV–visible spectrophotometer Jeway
6300. Elemental analyses for C, H, and N were recorded on a Carlo-Erba CHNS apparatus/O.

JOURNAL OF COORDINATION CHEMISTRY
313
EA 1108. Melting points were determined on a Köfler melting point apparatus and are uncor-
rected. Thin layer chromatography (TLC) was carried out on precoated Merck silica gel alu-
minum sheets 60 F254, and detection by UV light at 254 nm. Anhydrous 1,2-dimethoxyethane
(DME) was freshly distilled under argon from sodium/benzophenone. Commercial grade
reagents were used as supplied: o-phenylenediamine 98% (Alfa Aesar), glycolic acid 98%
(Alfa Aesar), dimethyl sulfate 99% (Sigma-Aldrich), Co(OAc)2 (Sigma-Aldrich), CoCl2·6H2O
(Sigma-Aldrich).
2.2. Synthesis of the ligand (Hmbm)
The ligand (1-methyl-1H-benzo[d]imidazol-2-yl)methanol was prepared in two steps as
follows:
2.2.1. Synthesis of (1H-benzo[d]imidazol-2-yl)methanol
To 5.0 g (0.046 mol) of o-phenylenediamine dissolved in 100 mL of a solution of hydrochloric
acid (4 N), 3 equiv. (10.48 g, 0.138 mol) of glycolic acid were added, and the mixture was
refluxed for 18 h. After completion of the reaction (TLC), the mixture was allowed to cool to
room temperature, and alkalinization with NH4OH (10%) was achieved (pH = 9). The resulting
precipitate was isolated by filtration, washed with water (3 × 5 mL), and dried on air. White
solid; Yield: 6.02 g (88%); M.p. 114–116 °C.
2.2.2. Synthesis of (1-methyl-1H-benzo[d]imidazol-2-yl)methanol (Hmbm)
To 1.2 eq. (2.3 g, 0.041 mol) of KOH dissolved in a 50% (v/v) water–ethanol mixture (14 mL),
5.1 g (0.034 mol) of 1-(1H-benzimidazol-2-yl) methanol was added. The solution was cooled
to 0 °C, and 5 mL of dimethyl sulfate was added dropwise over 30 min (the temperature of
the mixture did not exceed 5 °C). The mixture was kept under stirring at 0 °C for 30 min and
at room temperature for additional 15 min. The solid obtained was recovered by filtration
and washed with water, giving the title compound as a white solid. It was purified by recrys-
tallization from a mixture of CH3CN/EtOH. White solid; Yield: 4 g (72%); M.p. 122–124 °C; 1H
NMR (250 MHz, CDCl3): δ 7.76–7.64 (m, 1H), 7.29–7.19 (m, 3H), 5.13 (OH, br s, 1H), 4.88 (CH2,
s, 2H), 3.81 (N-CH3, s, 3H); FT-IR (4000–600 cm−1): 3450–2800, 1639, 1454, 1312, 1007, 860,
744, 567; UV–vis (MeOH) (λmax, nm (logε, M−1 cm−1): 280(5.35), 268(5.18), 244(5.14), 219(5.06).
2.3. Synthesis of complexes 1 and 2
General procedure: To a stirred solution of 1 equiv of Hmbm dissolved in anhydrous DME
(0.15 M) (e.g. 0.2 g in 10 mL), 0.5 equiv of the appropriate metal salt was added. The solution
was stirred at room temperature for 72 h for 1 and 48 h for 2. The resulting solid was recov-
ered by filtration and washed with cold DME (3 × 5 mL) and then dried in air. Suitable crystals
for X-ray diffraction were collected by slow evaporation at rt from a concentrated CH3CN
solution.
2.3.1. Synthesis of diacetatobis(1-methyl-1H-benzo[d]imidazol-2yl)methanol)
cobalt(II) [Co(Hmbm)2(OAc)2] (1)
0.2 g of Hmbm and 0.112 g of Co(OAc)2 in 10 mL of DME gave 0.134 g (44%) of the title
compound as pink crystals; M.p. > 260 °C; Anal. Calcd. for C22H26CoN4O6 (%): C, 52.70; H, 5.23;

314
A. BENHASSINE ET AL.
N, 11.17. Found: C, 53.19; H, 5.31; N, 11.59; FT-IR (4000–500 cm−1): 3409, 2929, 2353, 1631,
1415, 1334, 1238, 1060, 744, 659; UV–vis (MeOH) (λmax, nm (logε, M−1 cm−1) in MeOH):
284(5.33), 276(5.30), 269(5.25), 254(5.33), 218(5.24).
2.3.2. Synthesis of diaquabis(1-methyl-1H-benzo[d]imidazol-2yl)methanol) cobalt(II)
chloride [Co(Hmbm)2(H2O)2]Cl2 (2)
0.2 g of Hmbm and 0.147 g of CoCl2·6H2O in 10 mL of DME gave 0.155 g (52%) of 2. Blue
crystals; M.p. 171–173 °C; Anal. Calcd. for C18H24CoCl2N4O4 (%): C, 44.10; H, 4.93; N, 11.43.
Found: C, 44.15; H, 5.04; N, 11.50; FT-IR (4000–500 cm−1): 3406, 3224, 3028, 2353, 1631, 1535,
1446, 1334, 1238, 1037, 941, 709; UV–vis (MeOH) (λmax, nm (logε, M−1 cm−1): 285(5.26),
276(5.33), 270(5.29), 255(5.37), 218(5.37).
2.4. Crystallographic analyses
X-ray data were collected with a Bruker APEX II diffractometer equipped with a CCD area
detector at 150 K with a graphite-monochromated MoKα radiation, λ = 0.71073 Å. The crystal
was coated with Paratone oil and was mounted on loops for data collection. All refinements
were done by full-matrix least-squares on F2 using the SHELX-97 program and absorption
corrections were performed using SADABS [29–33]. The DIAMOND package and ORTEP-3
for Windows programs were used for generating figures of structures [34, 35]. Crystal data,
structure refinement parameters, some selected geometrical parameters, some intra and
intermolecular interactions hydrogen bonds, C–H…π and π–π stacking for 1 and 2 are listed
in Tables 1–4.
2.5. Electronic spectra
In the UV–vis experiments, the absorbance of Hmbm (as reference sample) and metal com-
plexes were measured at rt in methanol solution at c = 10−5 M. ε (molar extinction coefficient)
was determined as follows:
A
ꢀ =
× c(M)
L(cm)
where A is the absorbance, L is the thickness of cell, and c the molar concentration.
2.6. In vitro antioxidant activity
The in vitro antioxidant activity of the free ligand and its Co(II) complexes was evaluated
using the DPPH (2,2-diphenyl-1-picrylhydrazil) free radical scavenging method, as described
in a previous paper [27]. To 3 mL of a DPPH free radical solution in MeOH (0.1 mM), 1 mL of
each test sample and standard (Asc: ascorbic acid) in methanolic solution was added at a
concentration of 100 μg/mL. The absorbance was measured at t = 0 min, 30 min, 3 h, and
24 h incubation in the dark at room temperature with a UV–visible spectrophotometer oper-
ating at λ = 517 nm. All sample tests were performed in triplicate and the results are expressed
as mean standard deviation (SD). Percentage inhibition of DPPH free radical (I%) was cal-
culated using the following equation:

JOURNAL OF COORDINATION CHEMISTRY
315
Abs Control − Abs Sample
I(%) =
× 100
Abs Control
Table 1. Crystal data and structure refinement parameters for complexes 1 and 2.
1
2
empirical formula
formula weight
C22h26Con4o6
C18h24Con4o4, 2Cl−
501.4
490.24
t (K)
Wavelength (Å)
150
λ = 70,103
Crystal system
space group
triclinic
Pī
triclinic
Pī
a (Å)
b (Å)
c (Å)
α (°)
β (°)
7.88238(8)
8.8916(9)
9.4686(9)
107.423(4)
109.813(4)
102.834(5)
551.46(10)
1
7.2796(2)
8.7097(2)
9.4966(2)
69.212(10)
72.505(10)
74.418(10)
527.92(2)
1
γ (°)
V (Å3)
Z
absorption coefficient (mm−1
)
0.826
1.51
1.098
1.542
dcalc (mg·m−3
)
θ (°)
0.987
8235
2463
0.991
6592
2379
measured reflections
independent reflections
absorption correction
tmin = 0.677
tmax = 0.758
tmin = 0.631
tmax = 0.757
refinement method
Rint
full-matrix least-squares on F2
0.025
0.024
0.033
0.088
1.052
0.312
−0.294
R[F2 > 2σ(F2)]
wR(F2)
0.034
0.091
1.074
0.569
−0.319
Goodness-of-fit on F2
Δρmax (eÅ−3
)
)
Δρmin (eÅ−3
Table 2. distances (Å) and angles (°) of hydrogen bond for 1 and 2.
D–H…A
d(D–H)
d(H…A)
d(D–A)
D–H–A
Symmetry
1
C1–h1a…o2
C11–h11a…o1
o3–h1o…o1
o3–h1o…o2
0.97
0.96
0.86(3)
0.86(3)
2.51
2.59
2.59(3)
1.67(3)
3.446(3)
3.539(3)
3.036(2)
2.526(2)
162
171
113(3)
172(3)
x, −1+y, z
−1−x, −y, −z
−x, −y, −z
−x, −y, −z
2
C1–h1b…Cl1
o1–h1o…Cl1
o1w–h1w…Cl1
o1w–h1w…Cl1
0.97
2.74
3.684(3)
3.082(2)
3.072(3)
3.107(2)
166
x, y, z
0.77(3)
0.79(4)
0.74(4)
2.33(3)
2.29(3)
2.39(4)
167(3)
167(3)
164(4)
1−x, 1−y, −z
1−x, 1−y, −z
x, −1+y, z
Table 3. intermolecular and intramolecular interactions C–h…Cg (C–h…π; Å, °) operating in the crystal
structure of 1 and 2.
C–H…Cg
d(C–H)
d(H…Cg)
d(C–Cg)
C–H–Cg
Symmetry
1
C3–h3a…Cg2 (C4-C9)
2
C3–h3c…Cg3 (C4-C9)
0.97
0.97
2.94
2.91
3.639(3)
3.720(3)
131
143
−x, −y, 1−z
2−x, −y, 1−z

316
A. BENHASSINE ET AL.
Table 4. selected bond lengths (Å) and angles (°) for 1 and 2. experimental bond distances and angles
are given in parentheses.
1
2
B3LYP
CAM-B3LYP
B3LYP
CAM-B3LYP
Bond lengths (Å)
Co–n
1.909 (2.091)
1.829 (2.191)
1.926 (2.104)
–
1.956 (2.091)
2.200 (2.191)
1.960 (2.104)
–
1.923 (2.055)
1.961 (2.206)
–
1.989 (2.055)
2.006 (2.206)
–
Co–ooh
Co–ooCo
Co–oW
1.926 (2.078)
1.944 (2.078)
Bond angles (°)
n–Co–ooh
n–Co–ooCo
ooh–Co–ooCo
n–Co–oW
86.545 (87.55)
88.48 (92.45)
93.43 (90.08)
88.28 (87.55)
91.83 (92.45)
91.72 (90.08)
84.11 (78.25)
83.14 (78.25)
–
–
–
–
–
–
–
–
88.50 (92.10)
98.58 (94.36)
91.83 (92.10)
96.91 (94.36)
ooh–Co–oW
where Abs Control is the absorbance of DPPH radical + methanol and Abs Sample is the
absorbance of DPPH radical + test sample/standard Asc.
2.7. Computational methods
The theoretical study of the structure, electronic, and optical properties of 1 and 2 was carried
out in the framework of the density-functional theory (DFT) using the second generation
of type generalized gradient approximation (GGA), the global hybrid (B3LYP) [36] and the
range-separated hybrid (CAM-B3LYP) functional [37]. The latter include 65% of exact Hartree–
Fock exchange at long range. The Co atom was described through Stuttgart–Dresden effec-
tive core potential ECPs, designated as SDD. These energy-consistent ECPs are constructed
to reproduce experimental observables of a single atom, such as ionization potentials and
excitation energies, within relativistic Dirac–Fock theory [38], and only the valence electrons
were treated explicitly, namely the electrons of shells n = 3 and 4. The 6–31G+(d) basis sets
were used for non-metal atoms (N,C,O) [39]. Further analysis of electronic and optical prop-
erties were performed by calculations of both vertical and adiabatic ionization potentials,
the natural population analysis [40, 41], and by the calculation of the visible-UV absorption
spectra in the framework ofTime-Dependent DFT (TD-DFT) [42, 43]. Excited states and charge
transfer character of electronic transitions were characterized by plotting the electron density
between the excited and ground states for the main peaks of natural transition orbitals
(NTOs) [44]. All calculations have been performed using the Gaussian 09 version E.01 suite
of programs [45].
3. Results and discussion
3.1. Synthesis
(1-Methyl-1H-benzo[d]imidazol-2-yl)methanol (Hmbm) was prepared from (1H-benzo[d]
imidazol-2-yl)methanol according to the procedure described by Popov et al. [46]. The syn-
thesis of Co(II) complexes 1 and 2 was carried out in dry DME at room temperature by
addition of the appropriate cobalt salt (1 equiv.) to 2 equiv. of Hmbm (Scheme 1). The syn-
thesized complexes are air stable with high melting points. The molecular structures of

JOURNAL OF COORDINATION CHEMISTRY
317
Scheme 1. synthesis of metal complexes 1 and 2.
complexes were characterized by IR and UV–vis spectroscopy, elemental analysis, and single
crystal X-ray diffraction analysis.
3.2. Crystal structure descriptions
Complexes 1 and 2 crystallize in the space group Pī with one crystallographically independ-
ent molecule per asymmetric unit (Table 1). The crystal structure of these complexes indicates
that in the mononuclear unit cell, two Hmbm are coordinated in bidentate mode to the
Co(II) ion through nitrogen and oxygen atoms, and one pair of carboxylate group or two
water molecules, displaying a six-membered ring around the divalent metal center in dis-
torted octahedral geometry. The Co(II) ion, located on an inversion center, is surrounded by
two Hmbm in the equatorial plane; the two axial positions are occupied by two carboxylic
oxygen atoms or two water molecules (Figure 1). In 1, the bond lengths are Co–N at 2.0785(17)
Å, Co–OOH at 2.1911(13) Å, and Co–OOCO at 2.1045(13) Å, while in 2 Co–N at 2.055(16) Å,
Co–OOH 2.206(15) Å, and Co–OW at 2.078(17) Å. The bond lengths of Co–X in 1 and 2 are
identical (Table 4). In 1, the bond angles OCOO1–Co–O3OH and N1–Co–O1OCO are 90.08(5)°
and 92.45(6)°, respectively, while in 2 O1W–Co–O3OH and N1–Co–O1W are 94.36(8)° and
92.10(7)°, respectively (Table 4). In 1 and 2, the bond angle values of N1–Co–N1, HOO3–Co–
O3OH, OCOO1–Co–O1OCO, and W1O–Co–O1 W are very close to 180°, due to the crystallographic
inversion center.
In 1, the crystal packing can be described as double layers in b = 0 and b = 1 planes along
the a axis (Figure 2(A)). The complex presents intermolecular C–H···O and intramolecular O-H···O
hydrogen bonds (Table 2). The crystal structure is supported by intermolecular Cg···Cg (π–π
stacking) interactions between phenyl–phenyl rings (Cg···Cg = 3.7391(15) Å) and phenyl–im-
idazole rings (3.8199(14) Å) (Table 3). A unique intermolecular interaction occurs, C3-H3a···Cg2
(C4-C9), with a distance C···Cg of 3.639(3) Å and a C–H···Cg angle of 131° (Table 3).
In the crystalline structure of 2, the cations and anions are arranged in layers parallel to
the (010) plane along the a axis (Figure 2(B)). The cations are bonded to the anions via an
O-H⋯Cl hydrogen bond and there are significant π–π stacking interactions between cation
layers with centroid–centroid distances in the range of 3.9115(16)–3.9114(16) Å between
imidazole and phenyl rings. The packing is also consolidated by a weak intermolecular inter-
action C3–H3c···Cg3 (C4–C9) with a distance of C···Cg is 3.720(3) Å and the C–H···Cg angle of
143° (Table 3).

318
A. BENHASSINE ET AL.

JOURNAL OF COORDINATION CHEMISTRY
319
Figure 2. (a) View of the crystal structure of 1 showing double layers in b = 0 and b = 1 plane along the
a axis. C–h···o and intramolecular o–h···o hydrogen bonds are shown as green dashed lines connecting
these layers. (B) View of the crystal structure of 2 showing double layers in zigzag along the a axis. o–h⋯Cl
hydrogen bonds are shown as blue dashed lines connecting these layers.
3.3. Spectroscopic studies
3.3.1. Infrared spectra
The υ(O–H) stretching frequency of the free ligand merged with peaks assigned to C–H
vibrations, appearing as a broadened and weak band in the range of 2800–3500 cm−1. A
broad and more intense peak centered around 3409 and 3406 cm−1 was attributed to υ(OH,
H-bonded) for 1 and to coordinated water molecules for 2. Bands at 3224, 3028, and 2819 cm−1
of 2 are due to υ(OH), υ(C–H aromatic) and υ(CH3/CH2), respectively. In 1 only the υ(CH3/CH2)
appears as a discernable weak band at 2939 cm−1. Upon coordination, the υ(C=N) (1639 cm−1
of the free ligand) was shifted to lower frequency at 1531 and 1500 cm−1 for 1 and 2, respec-
tively, indicating the coordination of the benzimidazole nitrogen atom to the metal ion [47].
The strong absorption band at 1007 cm−1, attributable to υ(C–O) of Hmbm, was shifted to
longer frequencies at 1060 and 1037 cm−1 for 1 and 2, respectively. This is further supported
by the upward shift to an extent of 16 cm−1 of the υ(C–O) stretching vibration as compared
to that of the ligand (υ(C–O) = 1222 cm−1). These variations of the υ(C–O) confirm the par-
ticipation of the oxygen atom in the coordination [47]. The peaks at 1454, 1415, and 1446 cm−1
are due to υ(CH3/CH2) bending vibrations of Hmbm, 1 and 2, respectively. In 1, the broad
band at 1535 cm-1 was ascribed to υ(C=O), while in 2, the broad band centered at 3406 cm−1
was attributed to coordinated water molecules [48–50]. Overlapped IR spectra of Hmbm, 1
and 2 are shown in Figure 3 and spectral data are given in Table 5.
3.3.2. UV–vis study
The ligand spectrum exhibited four absorption bands: strong band absorption (I) with a max-
imum at λ = 219 nm, and 3 broad bands at 244(II), 268(III), and 280(IV) nm. Upon complexation
with cobalt ion, the sharp absorption band (I) remains practically unaltered (λmax = 218 nm),
while the others bands shifted to slightly longer wavelengths (red-shifted) as II (245→253–
254 nm), III (268→270 nm), and IV (280→284–285 nm). A new broad band V appeared at
276 nm for 1 and 2, as a consequence of the coordination to the metal center. Furthermore,
the best evidence of the formation of cobalt(II) complexes was the broad charge transfer
band, as a strong hump at 534.8 and 530.8 nm for 1 and 2, respectively (see Figure 4, inset)
[51, 52]. Almost strict overlap of intra-ligand transitions shows that they are of the same
topology (Figure 4) [53, 54]. In addition, comparison of ε values (expressed in logε) between

320
A. BENHASSINE ET AL.
Figure 3. overlapped ir spectra of hmbm (blue), 1 (red), and 2 (green).
Table 5. Calculated and experimental (given in parentheses) vibrational frequencies (cm−1) for hmbm,
1 and 2.
Hmbm
1
2
Assignment
B3LYP
CAM-B3LYP
B3LYP
CAM-B3LYP
B3LYP
CAM-B3LYP
υ(C–h)
(stretching)
υ(C=Ν)
3043–3242
(2800–3500)
1666
3061–3252
(2800–3500)
1629
3068–3262
(2935)
1646
3084–3279
(2935)
1607
3215–3253
(3028)
1646
3200–3271
(3028)
1662
(stretching)
υ(C–Ο)
(stretching)
υ(C–Η3)
(1639)
1272
(1222)
1475
(1639)
1235
(1222)
1475
(1531)
1252
(1238)
1450
(1531)
1223
(1238)
1450
(1500)
1229
(1238)
1474
(1500)
1241
(1238)
1487
(stretching)
υ(C=Ο) (stretching)
(1454)
–
(1454)
–
(1415)
1547
(1535)
–
(1415)
1528
(1535)
–
(1446)
–
(1446)
–
υ(Η2Ο)
–
–
3350
3379
(stretching)
(3406)
(3406)
Figure 4. overlapped electronic spectra of hmbm, 1 and 2 (10−5 m) together with the insets (10-3 m), and
are colored for hmbm (blue), 1 (red), and 2 (green).

JOURNAL OF COORDINATION CHEMISTRY
321
complexes and the free ligand indicates significant and sometimes very important variations,
confirming the formation of the complexes [47]. The absorption bands are mostly in agree-
ment with π–π* transitions. Overlapped electronic spectra recorded in MeOH at 10−5 M (10−3 M
in insets) are shown in Figure 4 and spectral data are given in Table 6.
3.4. Computational details
3.4.1. Geometry parameters
The selected geometry parameters of 1 and 2 in the ground states were calculated using
B3LYP and CAM-B3LYP functional density and are in good agreement with the experiments
(Table 4). For example, the calculated Co-OOH bond distance with CAM-B3LYP in 1 is 2.200
Å, and it correlates nicely with experimental 2.191 Å. The calculated bond lengths at the
CAM-B3LYP and B3LYP levels are slightly shorter than the experimental values within 0.01–
0.245 Å. The calculated bond angles for the two complexes at the B3LYP and CAM-B3LYP
levels are similar to the experimental values with slight deviations within 0.27–5.86°.
According to this observation, the calculations and experiments are in a good accordance,
particularly with CAM-B3LYP level. Optimized Cartesian coordinates are collected in Table
S1 in SI.
3.4.2. Frontier molecular orbitals (FMOs)
The frontier molecular orbitals (FMOs) play an important role in the optical and electric
properties, particularly in UV–Vis spectroscopy. The energy gap between HOMO and LUMO
Table 6. the spin allowed singlet–singlet electronic transition calculated with td-dft method and the
assignments to the experimental absorption bands for 1 and 2 (experimental wavelengths are given in
parentheses).
B3LYP
CAM-B3LYP
λ(nm)
E (eV)
f
Major contribution
λ(nm)
E (eV)
f
Major contribution
1
Band i
215
(218)
250
5.77
4.94
0.019
h-5→l (39%)
h-6→l+1 (26%)
h-9→l+1 (58%)
h→l+2 (11%)
h-1→l+3 (3%)
h-9→l (32%)
217
(218)
243
5.70
4.94
0.187
0.055
h-9→l+2 (62%)
h-5→l+2 (2%)
h-8→l (60%)
h-9→l (20%)
Band ii
0.364
(254)
(254)
Band iii
Band iV
266
(269)
272
4.67
4.55
0.135
0.013
261
(269)
273
4.75
4.53
0.124
0.180
h-9→l+2 (5%)
h-5→l+2 (87%)
h-8→l+1 (59%)
h-5→l+1 (8%)
h→l (8%)
h-9→l+1 (58%)
h-7→l+1 (10%)
h-8→l (30%)
h-5→l+1 (68%)
h-8→l (30%)
(284)
(284)
Band V
276
(276)
4.48
0.012
h-9→l (56%)
h-8→l (32%)
286
(276)
4.32
0.026
2
Band i
219
(218)
255
(255)
(270)
5.65
4.84
–
0.240
0.173
–
h-7→l (72%)
h-3→l+4 (18%)
h-1→l+2 (63%)
h→l (8%)
225
(218)
234
(255)
250
(270)
275
(285)
285
5.50
5.30
4.95
4.50
4.34
0.510
0.440
0.004
0.006
0.088
h-1→l+3 (32%)
h→l+2 (50%)
h-3→l+3 (32%)
h-2→l+2 (38%)
h-3→l (84%)
h-1→l (3%)
h-5→l (46%)
h-1→l (35%)
h-5→l (45%)
h-1→l (38%)
Band ii
Band iii
Band iV
Band V
–
286
(285)
(276)
4.33
–
0.017
–
h-5→l+1 (38%)
h-3→l+1 (50%)
–
(276)

322
A. BENHASSINE ET AL.
is an indicator of the stability, the chemical reactivity, and the optical polarizability of a
molecule [55]. In order to have a better understanding on the optical behavior of these
cobalt-based complexes, the calculations were carried out in a solvent model. The ten impor-
tant orbital energies of 1 and 2 including LUMO+4 to HOMO−4 molecular orbitals were
calculated (Table S2 in SI). The contour plots and energy of selected frontier orbitals for 1
and 2 are reproduced in Figure 5.
As seen in Table S2, 2 has a lower HOMO energy (−12.84 eV) than 1 (−9.10 eV) in B3LYP
level, and in CAM-B3LYP level ((−12.75 eV) versus (−10.69 eV)). The HOMO orbital in 1 is made
up of d(Co) and more pronounced π(Hmbm) contributions than 2 that presents only pro-
nounced d(Co) (see Figure 5). The LUMO energy of 2 is lower than that of 1 in both B3LYP
((−7.11 eV) versus (−5.11 eV)) and CAM-B3LYP levels ((−8.90 eV) versus (−6.17 eV)). The LUMO
is made up of d(Co)+π*(OH2) for 2, while it is made up of d(Co)+π*(OAc) for 1. The MO dia-
grams (Figure 5) show that the LUMO displays the most significant metal character in both
structures and the major contribution in the HOMO originates from the ligand.
3.4.3. Vibrational analysis
Important absorption bands of IR spectra of Hmbm, 1 and 2 were calculated using the B3LYP
and CAM-B3LYP levels. The calculated C–H bands show similar results with B3LYP and CAM-
B3LYP and were observed in the ranges 3043–3252 and 3068–3279 cm−1 for Hmbm and 1,
respectively, while in 2 they are observed in the range 3200–3271 cm−1. The experimental
υ(C–O) stretching vibrations appear at 1222 and 1238 cm−1 for the ligand and complexes 1
and 2, respectively. These bands were calculated at 1235 and 1223 cm−1 for the Hmbm and
1, respectively, and at 1241 cm−1 for 2 with CAM-B3LYP. The peaks at 1454 (Hmbm), 1415 (1),
and 1446 cm−1 (2) belong to the υ(CH3/CH2) bending vibrations, and the calculated values
with CAM-B3LYP are 1475 and 1450 cm−1 for Hmbm and 1, respectively, and 1474 cm−1 for 2
with B3LYP.
Figure 5. Contour plots and energy of selected frontier orbitals for 1 and 2.

JOURNAL OF COORDINATION CHEMISTRY
323
The experimental υ(C=N) stretching vibration is 1639, 1531, and 1500 cm−1 for the ligand
and complexes 1 and 2, respectively, and the calculated frequency has been shown for
Hmbm at 1629 cm−1 with CAMB3LYP, and 1646 cm−1 for 1 and 2 with B3LYP level. In 1, the
peak at 1535 cm−1 attributable to υ(C=O) asymmetric stretching frequency occurs theoret-
ically at 1528 cm−1 with CAM-B3LYP. For 2, υ(H2O) stretching vibration occurs at higher fre-
quency at 3406 cm−1, and theoretical results corresponding to asymmetric and symmetric
vibration with CAM-B3LYP gave 3379 cm−1. The calculated vibrational frequencies are in
reasonable agreement with experimental data. Experimental and theoretical IR spectra of
1 and 2 are pictured in Figure S1 in SI, and major lines are summarized in Table 5 together
with the experimental values.
3.4.4. Electronic absorption spectra
Theoretical UV–vis absorption spectra of Hmbm, 1 and 2 using both B3LYP and CAM-B3LYP
density functional are in clear agreement with experimental results (see Figure S2 in SI). The
calculated excitation energies at the TD-DFT show that the ligand has a well-resolved exper-
imental absorption band (I) at 219 nm that originates in the first excited state transition and
is attributed to HOMO → LUMO with π–π* character; this band was calculated at 218 nm
(Figure 6). The transitions associated with excited states were described by a substantial list
of orbital transitions with coefficients that are similar in magnitude than experimental results.
A qualitative description of electronic excitations states was evidenced using the Natural
transition orbitals (NTOs) [44]. For orbital contribution, the analysis of natural transition
orbitals depicted in Figure 6 showed a spin allowed singlet–singlet electronic transition. An
almost pure one natural orbital to one natural orbital transition was detected. For example,
the natural orbital pairs contribute to the excitations for 68% at 272 nm and 87% at 261 nm
for 1 (Figure 6b) and 72% and 84% at 219 nm and 285 nm, respectively, for 2 (Figure 6c).
Calculated absorption wavelength λ (nm), excitation energy E (eV), oscillator strength (f),
and main transitions with their major contribution (in percentage) of 1 and 2 are illustrated
in Table 6.
Complex 1 shows an experimental absorption band at 218 nm which was calculated
at 215 nm and attributed to HOMO-7 → LUMO + 1 (Figure 6). Analysis on electronic
structure and NTOs calculation shows that this transition is originating from π (Hmbm)
orbitals to d(Co) charge transfer and assigned to ligand-metal charge transfer (LMCT).
In 2, this band was calculated at 221 nm with CAM-B3LYP, corresponding to HOMO-4
and LUMO + 4 transition character and was attributed to ligand-metal charge transfer
(LMCT), as clearly represented in Figure 6. The absorption band (II) of Hmbm at 244 nm
mainly involved the HOMO−1 to LUMO+1 transition state as an intra-ligand charge trans-
fer π–π* (Figure 6). According to Figure 6, the bands (II) to (V) of 1 and 2 obtained with
CAM-B3LYP have a charge transfer character because of the electron is transferred from
a molecular orbital involving an π orbital on Hmbm to d-type orbital on Co atom.
Consequently, these transitions correspond to a ligand-metal charge transfer (LMCT).
The influence of the long-range exchange interaction in CAM-B3LYP level gives a HOMO-
LUMO gap much more significant and accurate absorption spectra of cobalt-based com-
plexes. The excited states and charge transfer character of electronic transitions were
assigned to LMCT.

324
A. BENHASSINE ET AL.
Figure 6. Contour plots of the selected molecular orbitals transitions of hmbm, 1 and 2; (a) π–π* transition
of hmbm, (b) nto transitions of 1 in Cam-B3lyP levels, (c) nto transitions of 2 in B3lyP and Cam-B3lyP
levels.
3.4.5. Atomic charge analysis
Atomic charge distributions on atoms of the complexes and free ligand were calculated by
natural population analysis (NPA) in the gas phase using B3LYP and CAM-B3LYP functional.
The charge distribution results of near-neighboring atoms of the cobalt ion show that the
electron density of N and O atoms slightly increased with respect to that of the free ligand,
while the electron density of the cobalt cation significantly decreased. The formal charge of
cobalt is +2, and upon complexation it decreased to +0.787/+0.723 and +0.652/+0.890 in 1
and 2, respectively, using functional hybrids B3LYP/CAM-B3LYP, indicating charge transfer
from Hmbm to the cobalt ion (Table 7).

JOURNAL OF COORDINATION CHEMISTRY
325
Table 7. nPa atomic charge distribution for 1, 2, and hmbm.
1
2
Hmbm
CAM-B3LYP
Atom
B3LYP
CAM-B3LYP
B3LYP
CAM-B3LYP
B3LYP
Co
0.787
−0.616
−0.512
−0.432
0.723
−0.679
−0.540
−0.433
0.652
−0.668
−0.890
−0.354
0.890
−0.570
−0.849
−0.455
–
–
ooh
ooCo
n
−0.741
–
−0.484
−0.748
–
−0.496
Table 8. dPPh radical scavenging activity of hmbm, 1, 2, Co(oac)2, and CoCl2·6h2o.
% Inhibition of DPPH free radical*
Entry
Compound
0 min
30 min
3 h
24 h
1
2
3
4
1
11.63 5.04
1.87 0.96
19.87 3.64
1.45 1.45
1.86 2.01
83.33 1.22
27.60 1.73
3.10 1.00
24.80 3.40
2.25 1.77
2.46 0.09
84.87 1.18
24.23 3.11
7.93 3.24
29.07 2.96
2.77 0.89
3.07 0.67
82.47 3.02
22.67 1.01
16.32 4.74
23.23 4.23
4.32 2.65
2.34 3.48
81.96 0.82
2
hmbm
Co(oac)2
CoCl2·6h2o
5
ascorbic acid
*data are an average for triplicate determinations.
3.5. In vitro DPPH radical scavenging essay
The in vitro antioxidant activity of Hmbm and complexes 1 and 2 have been carried out by
the DPPH assay which measures the hydrogen donating ability or radical scavenging activity
of antioxidants to convert stable DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical to DPPH-H
(2,2-diphenyl-1-picrylhydrazine) or 2,2-diphenyl-1-picrylhydrazine radical. Ascorbic acid (Asc)
was used as a standard antioxidant. The results are summarized in Table 8, and the DPPH
activity profiles of the Co(II) complexes and Hmbm as well as CoCl2·6H2O and Co(OAc)2 are
shown in Figure S3 in SI.
As shown in Table 8, the instantaneous antioxidant activity of the free ligand was
19.87 3.64%. Upon coordination, it decreased to 11.63 5.04% for 1, and more significantly
for 2 (1.87 0.96% versus 19.87 3.64%). After 24 h of incubation, the antioxidant activity
of 1 increased from 11.63 5.04% to 22.67 1.01% (entry 1) and for 2 from 1.87 0.96% to
16.32 4.74% (entry 2). Thus, 1 has shown better antioxidant activity than 2, but very close
to that of the free ligand (23.23 4.23%). In summary, the tested compounds exhibited
relatively moderate antioxidant activities compared to the standard at the used concentra-
tion (c = 100 μg/mL). No significant antioxidant activity was observed with Co(OAc)2 and
CoCl2·6H2O, which exhibit an inhibition percentage lower than 5% at all incubation times
(entries 4 and 5). The DPPH radical scavenging ability of the synthesized compounds can be
ranked in the order ascorbic acid >> Hmbm ≥ 1 > 2 after 24 h of incubation.
4. Conclusion
Two Co(II) complexes derived from (1-methyl-1H-imidazol-2-yl)methanol (Hmbm) have been
synthesized and characterized by single-crystal X-ray crystallography, elemental analysis,
IR, and UV–vis spectroscopy. In these complexes, two molecules of Hmbm are coordinated
in bidentate mode to the Co(II) ion through the nitrogen and oxygen atoms, and the metal
is also bonded to one pair of carboxylate groups in 1, while it is bonded to two water

326
A. BENHASSINE ET AL.
molecules in 2. The six-coordinate compounds display distorted octahedral geometries. The
geometry parameters, ground state structures, frontier molecular orbitals, and optical prop-
erties of 1 and 2 were investigated by DFT and TD-DFT in B3LYP and CAM-B3LYP levels and
are in good agreement with experimental values. The occupied orbitals display a d(Co) pro-
nounced character, while the virtual orbitals display mostly π* (Hmbm) character for both
complexes. The antioxidant activity of the free ligand and its cobalt complexes against the
free DPPH radical scavenger at low concentration (100 μg/mL) showed moderate antioxidant
activities.
Supplementary information
Crystallographic data (excluding structure factors) have been deposited as supplementary
publication number CCDC 1443908 for 1 and 1443910 for 2. These data can be obtained
free of charge from the Cambridge Crystallographic Data Center via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this article can be found in the online
version.
Acknowledgements
A.B. thanks Dr. L. Ismaili at Laboratoire de Chimie Organique et Thérapeutique, Neurosciences intégra-
tives et cliniques EA 481, Université Bourgogne Franche-Comté, France, for elemental analyses, and Prof.
A. Zertal at Laboratoire TIPE (Techniques Innovantes de Préservation de l’Environnement), Université
des frères Mentouri-Constantine, Algeria, for the UV–vis recording.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by the MESRS (Ministère de l’Enseignement Supérieur et de la Recherche
Scientifique), Algeria.
References
[1] D. Sun, L.L. Han, S. Yuan, Y.K. Deng, M.Z. Xu, D.F. Sun. Cryst. Growth Des., 13, 377 (2013).
[2] I. Castillo, B.N. Sanchez-Eguia, P.R. Martnez-Alanis, V.M. Ugalde-Saldivar, M. Flores-Alamo.
Polyhedron, 85, 824 (2015).
[3] I. Castillo, A.C. Neira, E. Norlander, E. Zeglio. Inorg. Chem. Acta, 422, 152 (2014).
[4] W.W. Yang, Y.W. Zhong, S. Yoshikawa, J.-Y. Shao, S. Masaoka, K. Sakai, J. Yao, M. Haga. Inorg. Chem.,
51, 890 (2012).
[5] R. Loganarhan, S. Ramakrishnan, E. Suresh, A. Riyasdeen, M.A. Akbarsha, M. Palaniandavar. Inorg.
Chem., 51, 5512 (2012).
[6] P. Singla, V. Luxami, K. Paul. RSC Adv., 4, 12422 (2013).
[7] Y.B. Bai, A.L. Zhang, J.J. Tang, J.M. Gao. J. Agric. Food Chem., 61, 2789 (2013).
[8] S.B. Deepthi, P. Ramesh, R. Trivedi, S.K. Buddana, R.S. Prakasham. Inorg. Chim. Acta, 435, 200 (2015).
[9] Y. Yan, Z. Liu, J. Zhang, R. Xu, X. Hu, G. Liu. Bioorg. Med. Chem. Lett., 21, 4189 (2011).
[10] A. Kamal, M.P.N. Rao, P. Swapna, V. Srinivasulu, C. Bagul, A.B. Shaik, K. Mullagiri, J. Kovvuri, V.S.
Reddy, K. Vidyasagar, N. Nagesh. Org. Biomol. Chem., 12, 2370 (2014).

JOURNAL OF COORDINATION CHEMISTRY
327
[11] A. Kamal, S. Ponnampalli, M.V.P.S.Vishnuvardhan, M.P.N. Rao, K. Mullagiri,V.L. Nayak, B. Chandrakant.
Med. Chem. Comm., 5, 1644 (2014).
[12] A.P. Singh, N.K. Kaushik, A.K. Verma, G. Hundal, R. Gupta. Eur. J. Med. Chem., 44, 1607 (2009).
[13] K. Vasantha, G. Basavarajaswamy, M.V. Rai, P. Boja, V.R. Pai, N. Shruthi, M. Bhat. Bioorg. Med. Chem.
Lett., 25, 1420 (2015).
[14] M. Hanif, M.A.H. Nawaz, M.V. Babak, J. Iqbal, A. Roller, B.K. Keppler, C.G. Hartinger. Molecules, 19,
8080 (2014).
[15] A. Kumar, A. Kumar, R.K. Gupta, R.P. Paitandi, K.B. Singh, S.K. Trigun, M.S. Hundal, D.S. Pandey. J.
Organomet. Chem., 801, 68 (2016).
[16] X.B. Fu, Z.H. Lin, H.F. Liu, X.Y. Le. Spectrochim. Acta, Part A, 122, 22 (2014).
[17] S. Hirashima, T. Oka, K. Ikegashira, S. Noji, H. Yamanaka, Y. Hara, H. Goto, R. Mizojiri, Y. Niwa, T.
Noguchi, I. Ando, S. Ikeda, H. Hashimoto. Bioorg. Med. Chem. Lett., 17, 3181 (2007).
[18] T. Ishida, T. Suzuki, S. Hirashima, K. Mizutani, A. Yoshida, I. Ando, S. Ikeda, T. Adachi, H. Hashimoto.
Bioorg. Med. Chem. Lett., 16, 1859 (2006).
[19] F. Téllez, H. Lopez-Sandoval, S.E. Castillo-Blum, N. Barba-Behrens. ARKIVOC, V, 245, (2008).
[20] D. Luneau, P. Rey. Coord. Chem. Rev., 249, 2591 (2005).
[21] F. Téllez, A. Cruz, H. Lopez-Sandoval, I. Ramos-Garcia, R. Castillo-Sierra, B. Paz-Michel, N. Nöth, A.
Flores-Parra, R. Contreras. Eur. J. Org. Chem., 20, 4203 (2004).
[22] F. Téllez, N. Barba-Behrens, A. Flores-Parra, R. Contreras. Polyhedron, 22, 2481 (2004).
[23] F.J. Yoe-Reyes, S. Bernes, N. Barba-Behrens. Acta Crystallogr., E61, m875 (2005).
[24] H.Y. Gong, B.M. Rambo, W. Cho, V.M. Lynch, M. Oh, J.L. Sessler. Chem. Commun., 47, 5973 (2011).
[25] H. Boulebd, L. Ismaili, M. Bartolini, A. Bouraiou, V. Andrisano, H. Martin, A. Bonet, I. Moraleda, I.
Iriepa, M. Chioua, A. Belfaitah, J. Marco-Contelles. Molecules, 21, 400 (2016).
[26] M. Bouchouit, M.E.H. Said, M. Kara-Ali, S. Bouacida, H. Merazig, N. Kacem-Chaouche, A. Chibani,
B. Zouchoune, A. Belfaitah, A. Bouraiou. Polyhedron, 119, 248 (2016).
[27] H. Boulebd, S. Zama, I. Betaiche, A. Bouraiou, S. Bouacida, H. Merazig, A. Romero, M. Chioua, J.
Marco-Contelles, A. Belfaitah. Monatsh. Chem., 147, 2209 (2016).
[28] H. Boulebd, L. Ismaili, H. Martin, A. Bonet, M. Chioua, J. Marco-Contelles, A. Belfaitah. Future, Med.
Chem., 9, 8 (2017).
[29] G.M. Sheldrick. SHELXL-97., University of Göttingen, Göttingen, Germany, Program for the
Refinement of Crystal Structures (1997).
[30] M.C. Burla, R. Caliandro, M. Camalli, B. Carrozini, G.L. Cascarano, L. DeCaro, C.G. Polidori, R. Spagna.
J. Appl. Crystallogr., 38, 381 (2003).
[31] G.M. Sheldrick. Acta Cryst. A, 64, 112 (2008).
[32] L.J. Farrugia. J. Appl. Cryst., 45, 849 (2012).
[33] G.M. Sheldrick. SADABS Bruker AXS Inc., Madison, Wisconsin, USA (2002).
[34] K. Brandenburg, M. Berndt. DIAMOND., Crystal Impact, Bonn, Germany (2001).
[35] L.J. Farrugia. J. Appl. Cryst., 30, 565 (1997).
[36] A.D. Becke. J. Chem. Phys., 98, 1372 (1993).
[37] D. Yanai, D.P. Tew, N.C. Handy. Chem. Phys. Lett., 393, 51 (2004).
[38] A. Alkauskas, A. Baratoff, C. Bruder. J. Phys. Chem. A, 108, 6863 (2004).
[39] A.E. Reed, F. Weinhold. J. Chem. Phys., 78, 4066 (1983).
[40] A.E. Reed, R.B. Weinstock, F. Weinhold. J. Chem. Phys., 83, 735 (1985).
[41] E. Runge, E.K.U. Gross. Phys. Rev. Lett., 52, 997 (1984).
[42] M.E. Casida, Time-Dependent Density-Functional Response Theory for Molecules, in: Recent
Advances in Density Functional Methods. Part I, D.P. Chong (Ed.), World Scientific, Singapore (1995).
[43] R. van Leeuwen. Int. J. Mod. Phys. B, 15, 1969 (2001).
[44] R.L. Martin. J. Chem. Phys., 118, 4775 (2003).
[45] Gaussian 09, Revision E.01, Gaussian, Inc., Wallingford, CT (2009).
[46] I.I. Popov, V.N. Narezhnaya, A.A. Zubenko. Chem. Heterocycl. Compd., 14, 891 (1978).
[47] P.E. Ikechukwu, P.A. Ajibade. Molecules, 20, 9788 (2015).
[48] S. Munde, A.N. Jagdale, S.M. Jadhav, T.K. Chondhekar. J. Korean Chem. Soc., 53, 407 (2009).
[49] D.P. Shoemaker, C.W. Galand, Experiments in Physical Chemistry, Fifth Edn., McGraw-Hill Inter. Ed.,
New York, NY, USA (1989).

328
A. BENHASSINE ET AL.
[50] A.A. Osowole, G.A. Kolawole, O.E. Fagade. Synth. React. Inorg. Met.-Org. Nano-Met. Chem., 35, 829
(2005).
[51] S. Demir, A. Güder, T.K. Uazicilar, S. Çaglar, O. Büyükgüngör. Spectrochim. Acta, Part A, 150, 821
(2015).
[52] Z. Xinde, W. Chenggang, L. Zhiping. Synth. React. Inorg. Met. Org. Chem., 26, 955 (1996).
[53] K. Mounika, B. Ampama, J. Pragathi, C. Gyanakunarym. J. Sci. Res., 2, 513 (2010).
[54] R.A.A. Ammar, A.M.A. Alaghaz. Int. J. Electrochem. Sci., 8, 8686 (2013).
[55] A.M. Asiri, M. Karabacak, M. Kurt, K.A. Alamry. Spectrochim. Acta, Part A, 82, 444 (2011).