Synthesis, X-ray structure and theoretical investigation of 2-(2’-quinolyl)benzimidazole metal complexes

Article abstract of DOI:10.1007/s12039-016-1210-1

Synthesis, characterization and DFT analysis of 2-(1H-benzo[d]imidazol-2-yl)quinoline (BQ) and its cobalt and manganese coordination compounds {Co(DMF)(BQ) Cl ₂} and {Mn(DMF)(BQ) Cl ₂} have been described. The ligand, 2-(1H-benzo[d]imidazol-2-yl)quinoline (BQ) crystallizes in non-centrosymmetric monoclinic crystal system with cell parameters a = 12.9280(4) ?, b = 7.9429(3) ?, c = 25.8478(9) ?, α = γ=90^°,β=103.005(2)^°. {Co(DMF)(BQ)Cl ₂} and {Mn(DMF)(BQ)Cl ₂} crystallized in triclinic space group P-1. The metal(II) environment exhibits trigonal bipyramidal coordination. These complexes show presence of N–H …Cl, C–H..Cl hydrogen bonds and strong intramolecular C–H..O interactions. The structure parameters were calculated and they are in good agreement with those observed experimentally. Theoretically calculated frontier molecular orbitals (HOMO–LUMO) of the complexes and their energies indicate intermolecular charge transfer and delocalization of electron density within the molecule. [Figure not available: see fulltext.]

Full text of DOI:10.1007/s12039-016-1210-1

c
J. Chem. Sci. ꢀ Indian Academy of Sciences.
DOI 10.1007/s12039-016-1210-1
REGULAR ARTICLE
Synthesis, X-ray structure and theoretical investigation
of 2-(2’-quinolyl)benzimidazole metal complexes
FERIEL AOUATEF SAHKIa, LYAMINE MESSAADIAb, HOCINE MERAZIGa,
AISSA CHIBANIa, ABDELMALEK BOURAIOUa,∗ and SOFIANE BOUACIDAa,c
aUnité de Recherche de Chimie de l’Environnement et Moléculaire Structurale, Université des Frères
Mentouri, Constantine 25000, Algérie
bLaboratoire Énergétique Appliquée et Matériaux, Université de Jijel, 18000 Jijel, Algérie
cDépartement des sciences de la matière, Université Oum El Bouaghi, 04000, Oum El Bouaghi, Algérie
Email: bouraiou.abdelmalek@yahoo.fr
MS received 27 June 2016; revised 11 November 2016; accepted 15 November 2016
Abstract. Synthesis, characterization and DFT analysis of 2-(1H-benzo[d]imidazol-2-yl)quinoline (BQ) and
its cobalt and manganese coordination compounds {Co(DMF)(BQ) Cl2} and {Mn(DMF)(BQ) Cl2} have been
described. The ligand, 2-(1H-benzo[d]imidazol-2-yl)quinoline (BQ) crystallizes in non-centrosymmetric mon-
oclinic crystal system ◦with cell parameters a = 12.9280(4) Å, b = 7.9429(3) Å, c = 25.8478(9) Å, α = γ =
90◦, β = 103.005(2) . {Co(DMF)(BQ)Cl2} and {Mn(DMF)(BQ)Cl2} crystallized in triclinic space group
P-1. The metal(II) environment exhibits trigonal bipyramidal coordination. These complexes show presence of
N–H. . .Cl, C–H...Cl hydrogen bonds and strong intramolecular C–H...O interactions. The structure parameters
were calculated and they are in good agreement with those observed experimentally. Theoretically calculated
frontier molecular orbitals (HOMO–LUMO) of the complexes and their energies indicate intermolecular charge
transfer and delocalization of electron density within the molecule.
Keywords. Quinoline; benzimidazole; metal complexes; x-ray structure; electronic structure.
1. Introduction
2. Experimental
2.1 General considerations
Nitrogen-based ligands are extensively studied as
complexes with many metal ions such as cobalt and
manganese.1,2 Coordination complexes based on nitro-
gen donor chelate ligands and cobalt or manganese
ions, having a number of available oxidation states,
All chemicals, reagents and solvents were of analytical
grade, purchased and used as received. H-NMR and 13C-
1
NMR spectra were recorded on Bruker Avance DPX250
spectrometers. The melting point was determined using an
have attracted great attention because of their potential Electrothermal IA9100 digital melting point apparatus. UV
spectra were recorded on UV/VIS Spectrophotometer Opti-
zen 1220. IR spectra were recorded on Shimadzu FT/IR-
8201 PC spectrophotometer. Powder X-ray diffraction data
were collected on a PANalytical X’Pert PRO X-ray pow-
der diffractometer at room temperature. The 2θ scan range
was 5–60◦, with a step size of 0.007◦. Microanalysis was
performed in Perkin Elmer Elemental Analyzer 2400/II.
applications in various fields of human interest such as
antitumor,3,4 antiviral,5,6 antifungal and antibacterial7,8
and antioxidant9,10 drugs. In addition to the biolog-
ical importance, diverse catalytic11,12 and magnetic
properties13,14 of such compounds have been explored.
Following our previous works related to the use
of benzazole thioether as ligand for new coordination
complexes,15,16 we report herein new manganese and
cobalt complexes containing a polydentate ligand, by
combination of quinoline and benzimidazole fragments.
In addition, density functional theory calculations were
used for determining the electronic structures, geo-
metrical parameters, bonding analysis and reproducing
efficiently the experimental structures.
2.2 Synthesis of 2-(1H-benzo[d]imidazol-2-yl)
quinoline (BQ)
10 mmol of phenylene diamine was added to a suspension of
quinaldic acid (10 mmol) in 1 g of polyphosphoric acid. The
mixture was heated at 160◦C for 24 h. After completion of
the reaction, water was added and the precipitate that formed
was filtered, washed with H2O (2 × 50 mL). The residue
was suspended in 20 mL of NaOH (5 M), then filtered to
afford the desired product. Yield 92%; Yellow solid; M.p.:
∗For correspondence

Feriel Aouatef Sahki et al.
85–88◦C (Literature17: 93–95◦C); UV–Vis (MeOH,
2.5 Computational studies
λmax/nm): 286, 308, 322, 336, 350; IR (KBr, cm−1): 3047,
1654, 1596, 1566, 1500, 1411, 1319, 1238, 1141, 829, 748;
1H NMR (250.13 MHz, CDCl3) δ: 11.21 (s, 1H), 8.64–7.24
(m, 10H).
All the computational studies were carried out using the
Gaussian 09 package22 and the Gauss-View molecular
visualization program.23 Density functional theory (DFT)
methods using the combination of the Becke exchange
functional24 and the vp86 non-local correlation functional25
combined with the 6-31G (p, d) basis set were utilized to
determine the quantum chemical parameters for the title
2.3 Preparation of complexes
2.3a Preparation of {Co(DMF)(BQ)Cl2} (1): A solution
of 238 mg of CoCl2, 6H2O (1 mmol) and 245 mg (1 mmol)
of 2-(1H-benzo[d]imidazol-2-yl)quinoline (BQ) in 10 mL of
MeOH was stirred for 18 h at room temperature. The green
precipitate that formed was filtered and dried in vacuo. Yield
87%; M.p.: 205–210◦C; UV–Vis (MeOH, λmax/nm): 288,
310, 322, 336; IR (KBr, cm−1): 3409, 3070, 1593, 1504,
1434, 1326, 1153, 837, 752. Anal. calcd. (%) for Co(BQ)Cl2,
H2O (C16H13Cl2CoN3O): C 48.88, H 3.33, N 10.69, found
(%): C 48.93, H 3.28, N 10.81. The crude product was
recrystallized in DMF.
compounds, such as geometrical parameters, EHOMO, ELUMO
ꢀE (energy gap) and dipole moment (μ).
,
3. Results and Discussion
3.1 Synthesis
2-(1H -benzo[d]imidazol-2-yl)quinoline (BQ) was
synthesized following a literature procedure starting
from phenylene diamine and quinaldic acid.26 The
complexes 1 and 2 were prepared as description in
Scheme 1. The ligand (BQ) was stirred in MeOH with
MCl2 overnight at room temperature. The solid M(II)
complexes was filtered off and dried. These are very
stable in the air. The M(II) complexes are soluble in
DMF and DMSO but insoluble in water and other
organic solvents, such as methanol. To verify the phase
purity of the prepared complexes, the PXRD pattern
was recorded. The diffractograms indicated that both
complexes are pure phases. The obtained complexes
were recrystallized in DMF (Scheme 1).
2.3b Preparation of {Mn(DMF)(BQ)Cl2} (2): A solu-
tion of 198 mg of MnCl2, 4H2O (1 mmol) and 245 mg
(1 mmol) of 2-(1H-benzo[d]imidazol-2-yl)quinoline (BQ)
in 10 mL of MeOH was stirred at room temperature for
18 h. The light yellow precipitate that formed was filtered
and dried in vacuo. Yield 78%; M.p.: 210–213◦C; UV–Vis
(MeOH, λmax/nm): 288, 308, 322, 335; IR (KBr, cm−1):
3436, 3058, 1596, 1504, 1431, 1323, 1149, 837, 756. Anal.
calcd. (%) for Mn(BQ)2Cl2, MeOH (C33H26Cl2MnN6O):
C 61.12, H 4.04, N 12.96, found (%): C 61.40, H
3.91, N 13.57. The crude product was recrystallized
in DMF.
3.2 Crystal structures
2.4 X-ray crystallography
The ligand (BQ) and the two obtained complexes were
recrystallized and suitable crystals of BQ, 1 and 2 were
grown in DMF solution. It should be noted that dur-
ing the recrystallisation step, the DMF molecule coor-
dinates through O atoms to the metallic atom in both
M(II) complexes. The X-ray crystallographic analysis
confirmed their respective structures and the refined
X-ray crystal structures are shown in Figure 1. Crystal
data and structural details of the prepared complexes are
presented in Table 1.
The crystal was coated with Paratone oil and mounted
on loops for data collection. X-ray data were collected
with a Bruker Apex II CCD area detector diffractometer
with a graphite-monochromated Mo-Kα radiation source
(0.71073 Å) at 298 K. The reported structure was solved
by direct methods with SIR200218 to locate all the non-H
atoms which were refined anisotropically with SHELXL9719
using full-matrix least-squares on F2 procedure from within
the WinGX20 suite of software used to prepare the mate-
rial for publication. All absorption corrections were per-
formed with the SADABS program.21 All the H atoms were
placed in the calculated positions and constrained to ride on
their parent atoms, except for H atoms of water molecule
which were located in a difference map and their posi-
tions were refined isotropically with O–H distance restraints
of 0.85 (2) Å and with Uiso(H) = 1.2 Ueq(O). Crys-
tal data, structure refinement parameters, selected angles,
bond lengths and some intra- and intermolecular inter-
actions, hydrogen bonds for compounds BQ, {Co(DMF)
(BQ) Cl2} (1) and {Mn(DMF)(BQ)Cl2} (2) are listed in
Tables 1–3.
3.2a Crystal structure of ligand BQ: The ligand 2-
(1H-benzo[d]imidazol-2-yl)quinoline (BQ) crystallizes in
non-centrosymmetric monoclinic crystal system (space
group Cc). The asymmetric unit contains two co-
crystallized water molecules and two ligands, crystal-
lographically independent (molecules A and B). Each
molecule consists of a benzimidazole unit connected
to quinolyl moiety. The C–N bonds lengths values are,
N(1A)–C(1A) (1.379(5) Å), N(1A)–C(9A) (1.308(4) Å),
N(2A)–C(10A) (1.373(4)Å), N(2A)–C(11A) (1.371(5) Å),

Investigation of 2-(2’-quinolyl)benzimidazole metal complexes
Table 1. Crystallographic data and refinement parameters for BQ, complexes 1 and 2.
BQ
{Co(DMF)(BQ)Cl2} (1)
{Mn(DMF)(BQ)Cl2} (2)
Formula
C16H11N3, H2O
263.29
Prism, Colorless
Monoclinic
C c
C19H18Cl2 Co N4O
448.2
C19H18Cl2 Mn N4O
474.28
Prism, Colorless
Triclinic
Formula weight
Crystal habit, color
Crystal system
Space group
a (Å)
Prism, Blue
Triclinic
P -1
P -1
12.9280(4)
7.9429(3)
25.8478(9)
90
103.005(2)
90
8.5673(12)
10.7470(17)
12.1600(16)
103.071(13)
94.461(9)
112.97(2)
986.8(2)
8.6355(13)
10.8411(16)
12.1779(18)
104.473(7)
93.532(7)
113.324(6)
997.0(3)
b (Å)
c (Å)
α (◦)
β (◦)
γ (◦)
Volume (Å3)
Z, Zꢁ
2586.12(16)
4, 8
2, 2
1.508
1.157
458
2, 2
1.480
0.946
454
Density (calculated, g cm−3
)
1.352
0.088
1104
Absorption coefficient (mm−1
F(000)
)
Crystal size (mm)
0.08 × 0.13 × 0.15
3.23–30.54
14330
0.05 × 0.10 × 0.13
3.42–31.16
14863
0.09 × 0.14 × 0.19
3.40–36.23
36453
θ range for data collection (◦)
Reflections collected
Independent reflections
Rint
6562
0.0352
5839
0.0530
9496
0.0196
Reflections with I ≥ 2σ(I)
Number of parameters
Goodness-of-fit on F2
Final R indices [I ≥ 2σ(I)]
R indices [all data]
3757
373
0.984
0.0591
3334
246
1.052
0.0737
7273
246
1.029
0.0348
R1 = 0.1145,
wR2 = 0.1298,
0.381, −0.165
CCDC 1455171
R1 = 0.1380, wR2 = 0.1825,
R1 = 0.0963, wR2 = 0.1068
Largest difference peak and hole
(Å−3
CCDC deposition no.
1.185, −0.88
0.432, −0.248
)
CCDC 1469612
CCDC 1455172
Table 2. Distances (Å) and angles (◦) of hydrogen bond for BQ, complexes (1) and (2).
D–H. . .A
d(D–H) d(H. . .A) d(D–A) D–H–A
Symmetry
BQ
O1w–H1w. . .N1a
O1w–H2w. . .N3b
O2w–H3w. . .O1w
O2w–H3w. . .N1b
O1w–H4w. . .N3a
N2a–H21a. . .O2w
N2b–H21b. . .O1w
{Co(DMF)(BQ)Cl2} (1)
N3–H3n. . .Cl2
C12–H12. . .O21
C22–H22a. . .Cl1
{Mn(DMF)(BQ)Cl2} (2)
N3–H3n. . .Cl1
0.89(3)
0.86(3)
0.92(3)
0.92(3)
0.88(3)
0.86
2.24(4)
2.02(4)
2.50(4)
2.23(4)
1.94(4)
1.9500
1.9500
3.069(4)
2.808(4)
2.948(4)
3.035(4)
2.811(4)
2.766(4)
2.771(4)
156(3)
151(3)
110(3)
147(3)
169(4)
159.00
159.00
1/2+x,1/2+y,z
x,y,z
x,y,z
x,1+y,z
x,y,z
-1/2+x,-1/2+y,z
x,y,z
0.86
0.86
0.93
0.96
2.3300
2.5400
2.7200
3.160(5)
3.160(5)
3.643(9)
161.00
123.00
161.00
2-x,1-y,-z
x,y,z
2-x,2-y,1-z
0.86
0.93
0.96
0.96
2.3200
2.5700
2.7200
2.4400
3.149(1)
3.189(2)
3.633(2)
2.772(3)
160.00
124.00
160.00
100.00
1-x,1-y,-z
x,y,z
1-x,2-y,1-z
x,y,z
C12–H12. . .O21
C22–H22a. . .Cl2
C23–H23c. . .O21
N(3A)–C(10A) (1.308(4) Å), N(3A)–C(16A) (1.370 N(2B)–C(11B) (1.390(5)Å), N(3B)–C(10B) (1.317(4) Å),
(5) Å) (molecule A), N(1B)–C(1B) (1.379(5) Å), N N(3B)–C(16B) (1.397(5) Å) (molecule B), which indi-
(1B)–C(9B) (1.317(4) Å), N(2B)–C(10B) (1.347(5) Å), cate partial double bond character (Table 2). Bond

Feriel Aouatef Sahki et al.
Table 3. Selected bond lengths (Å) and angles (◦) for ligand BQ, complexes 1 and 2 with estimated standard deviations;
theoretical structure parameters obtained by bvp86/6-31G(d, p) are given in parentheses.
Bond length/Bond angle
C10-N2
BQ(A)
1.373(4)
1.308(4)
1.370(5)
1.477(5)
BQ(B)
{Co(DMF)(BQ)Cl2} (1)
{Mn(DMF)(BQ)Cl2} (2)
1.347(5)
(1.336)
1.317(4)
(1.309)
1.397(5)
(1.390)
1.465(5)
(1.487)
–
1.323(6)
(1.336)
1.354(6)
(1.346)
1.375(6)
(1.390)
1.467(6)
(1.487)
1.3249(13)
(1.327)
C10-N3
1.3488(13)
(1.3469)
1.3808(15)
(1.3909)
1.4685(14)
(1.487)
C16-N3
C9-C10
N1-M
2.275(4)
(2.275)
2.3781(9)
(2.388)
N2-M
–
–
–
–
2.042(4)
(2.009)
2.092(4)
(2.092)
2.2717(15)
(2.271)
2.3389(15)
(2.338)
2.1772(9)
(2.024)
2.1662(9)
(2.166)
2.4249(4)
(2.424)
2.3421(4)
(2.342)
M1-021
M-Cl1
M-Cl2
N1-C9-C10
N2-C10-N3
N1-M1-N2
N2-M1-Cl1
Cl1-M1-Cl2
116.8(3)
112.7(3)
116.1(3)
(124.2)
114.0(4)
(110.3)
–
112.8(4)
(113.3)
113.1(4)
(110.34)
75.94(14)
(75.94)
117.09(12)
(119.36)
118.82(6)
(118.81)
113.99(9)
(113.36)
112.48(9)
(110.65)
73.04(3)
(73.70)
117.02(3)
(119.42)
119.364(17)
(119.364)
–
–
Scheme 1. Synthesis of 1 and 2.
angles for N(1A)–C(9A)–C(10A) and for N(2A)– with water molecule via O-H. . .N and N-H. . .O
C(10A)–N(3A) are 116.8 (3)◦ and 112.7 (3)◦, respec- hydrogen bonding interactions resulting in the forma-
tively, and the bond angle N(2A)–C(10A)–C(9A) is tion of three dimensional network. Hydrogen bond
120.9 (3) Å (Table 1). Both molecules A and B are between amine moieties and water molecule form
almost planar and parallel which form a dihedral angle a chain with D11(2) graph set motif,27 when water
of 0.93(2)◦. The crystal packing can be described molecule acts as acceptor as well as donor. Additional
as alternating double layers in zigzag manner along hydrogen-bonding parameters are listed in Table 2.
the b axis (at b=0 and b=1/2) parallel to (010) The packing is consolidated by slipped π − π stack-
plane (Figure 2). These layers are connected together ing with centroid to centroid distance of 3.777(2) Å

Investigation of 2-(2’-quinolyl)benzimidazole metal complexes
Figure 1. Oak Ridge thermal ellipsoid plots (ORTEP) of the molecular structures of BQ,
{Co(DMF)(BQ) Cl2} (1), and {Mn(DMF)(BQ) Cl2} (2) in the crystal and atom numbering scheme
adopted (displacement ellipsoids at the 50% probability level; H atoms with arbitrary radii).
Figure 2. Diagram packing of BQ viewed along the a axis showing layers in
zigzag parallel to (010) plane which are connected with water molecule with
N–H...O and O–H...N hydrogen bonds.
2-(1H-benzo[d]imidazol-2-yl)quinoline (BQ) ligand,
two chloride ions and one coordinated DMF molecule
(Figure 1). Each complex contains one organic ligand
that contain two rings, N1, C1–C9 (quinoline ring) and
N2, N3, C10–C16 (benzimidazole ring).
The metal (II) environment exhibits Trigonal bipyra-
midal coordination. The bond lengths around the metal
centers are in the range of 2.042(4)–2.3781(13) Å
(N–M), 2.2717(15)–2.4249(4) Å (Cl–M), 1.237(7)–
1.2383(16) (O–M). Bond angles for N1–Co1–Cl1,
N1–Mn1–Cl1, Cl1–Co1–O21 and for Cl1–Mn1–O21
to 3.878(2) Å. All these interactions link the molecule
within the layers and also link layers together and
reinforce the cohesion of the organic structure.
3.2b Crystal structure of complexes {Co(DMF)(BQ)
Cl2} (1) and {Mn(DMF)(BQ) Cl2} (2): The com-
pounds 1 and 2 crystallized in triclinic space group
P-1. Selected bond distances and bond angles for both
compounds are listed in Tables 3 and 4. Both com-
plexes are five-coordinated (Figure 1, Table 1). The
metal ion is surrounded by two N-donor atoms of the

Feriel Aouatef Sahki et al.
Table 4. Calculated quantum chemical parameters of the BQ and complexes 1 and 2 calculated
at DFT at the bvp86/6-31G (d, p) level.
Parameters
BQ
{Co(DMF)(BQ)Cl2} (1) {Mn(DMF)(BQ)Cl2} (2)
Total energy (Hartree) −780.57620552
−3332.4023263
−4.569
−3100.6407187
−4.628
EHOMO(eV)
ELUMO(eV)
ꢀEH−L(eV)
μ (debye)
−5.0197
−2.736
2.283
−3.773
−3.556
0.796
8.6330
1.072
8.3973
4.5409
Figure 3. Diagram packing of 1 showing layers parallel to (1-10) plane and C–H...Cl interactions in black (R22(12)).
are 98.46(10)◦, 88.53 (2)◦, 97.32 (16)◦ and 90.64(3)◦, parameters such as bond length and bond angles
respectively. Bond lengths and angles are comparable found from the crystal structures are compared with
to those reported previously and are in the expected range.28,29 those of optimized geometries. Table 3 summarizes
The crystal packing for both complexes can be some selected geometrical parameters of the inves-
described as alternating layers parallel to (1–10) plane tigated compounds. In general, the obtained results
(Figures 3 and 4). In these layers, the arrangement were found to be in good agreement with experimen-
of each molecule induces strong π–π stacking inter- tal values, except some bond lengths, such as C9–C10
molecular interaction. The shortest centroid–centroid and N2-M (M=Co, Mn). For example, deviations
distances are 3.458(3) and 3.465(1) Å for Co and Mn between calculated and experimental N2-M bonds dis-
complex, respectively. Also these complexes present tances are 0.01 Åfor BQ(A), 0.022 Åfor BQ(B),
N–H. . .Cl and C–H...Cl hydrogen bonds forming chain 0.020 Å for complex 1 and 0.018 Å for complex 2,
and ring, respectively, with D11(2) and R22(12) graph respectively. However, for bond angles, we can see
set motif.27 Strong intramolecular interactions of C– that the variations are shorter and longer between the
H...O are found in the crystal packing. (Figures 3 and 4, experimental and optimized values due to intermolecu-
Table 2).
lar interactions by quinoline with the metal. Moreover,
we note that the experimental results belong to the solid
state and the theoretical calculations belong to the gas
phase.
3.3 Computational details
3.3a Geometrical structure: The optimized structure
parameters (bond lengths and angles) for title com- 3.3b Frontier molecular orbitals (HOMO–LUMO)
plexes were calculated using the density functional the- analysis: The optimization of molecular geometry of
ory (DFT)/ bvp86/6-31G (p, d) method. The structural title compounds in the gas phase was calculated in

Investigation of 2-(2’-quinolyl)benzimidazole metal complexes
Figure 4. Diagram of packing of 1 viewed along a axis showing N–H...Cl interactions in red (D11(2)).
Figure 5. Frontier molecular orbitals of compounds (a) ligand BQ, (b) complex
{Co(DMF)(BQ)Cl2} (1), and (c) complex {Mn(DMF)(BQ)Cl2} (2).
order to study the stability of the total energy and the chlorine (Cl), azote (N1, N21), oxygen (O21) and
the energy gap between the frontier molecular orbitals cobalt (Co) atoms, with contributions on the quinoline
(ꢀEH−L = EHOMO−ELUMO) using the density functional ring BQ(B). The LUMO is mostly centered in chlo-
theory (DFT) at bvp86/6-31G (d, p) level. The frontier rine (Cl), azote (N1, N21, N2, N3), oxygen (O21) and
orbital gap helps to characterize the chemical reactiv- cobalt (Co) atoms, with slight contribution of quino-
ity and kinetic stability of the molecules. A molecule line ring BQ(B). In the case of ligand BQ, the HOMO
with a small frontier orbital gap is more polarizable is delocalized almost over the whole π-conjugated sys-
and is generally associated with a high chemical reac- tem, while the LUMO, and is also delocalized over the
tivity, low kinetic stability and is also called as a soft whole molecule. The LUMO and HOMO energy gap
molecule.30 The HOMO represents ability to donate an for the complex 1 equal to 0.796 eV, which is lower than
electron and LUMO represents the ability to accept an that of complex 2 (1.072 eV) and ligand BQ (2.283 eV),
electron. Table 4 shows the total energy, ELUMO, EHOMO reflecting intermolecular charge transfer and delocal-
and ꢀEH−L energy gap of both complexes 1, 2 and ization of electron density within the molecule.31 There-
Ligand BQ. The calculations indicate that the com- fore, it is clear that the complex 1 is more reactive and
plex 1 has lower value of total energy and energy gap more polar than complex 2 and ligand BQ.
(ꢀEH−L) than complex 2. Therefore, complex 1 is more
reactive than 2. The 3D plots of the frontier molecu-
lar orbitals HOMO and LUMO for title compounds are
illustrated in Figure 5. As can be seen in Figure 5, the
HOMO for complexes 1 and 2 are mainly located over
4. Conclusions
In summary, this paper describes the synthesis, single
crystal X-ray diffraction analysis and DFT studies of

Feriel Aouatef Sahki et al.
metal complexes as antiviral agents J. Inorg. Biochem.
2-(2’-quinolyl)benzimidazole and Co and Mn complexes.
150 9
The complexes were synthesized using a simple
method. Single crystal X-ray diffraction analysis of
the studied complexes reveals a trigonal bipyramidal
coordination of the metal(II) environments. These com-
plexes present N–H. . .Cl, C–H...Cl and C–H...O inter-
actions in the crystal packing. The theoretical and
experimental bond lengths and angles are in good
agreement with each other. Theoretically calculated
frontier molecular orbitals (HOMO-LUMO) of both
complexes suggest intermolecular charge transfer and
delocalization of electron density within the molecule.
The accuracy of the results also predicts that the DFT
studies performed at bvp86/6-31G (p, d) level is an
appropriate quantum chemical method for reproducing
efficiently the experimental structures.
7. Maghami M, Farzaneh F, Simpson J, Ghiasi M and
Azarkish M 2015 Synthesis, crystal structure, antibacte-
rial activity and theoretical studies on a novel mononuclear
cobalt(II) complex based on 2,4,6-tris(2-pyridyl)-1,3,5-
triazine ligand J. Mol. Struct. 1093 24
8. Kani I, Atlier Ö and Güven K 2016 Mn(II) com-
plexes with bipyridine, phenanthroline and benzoic
acid: Biological and catalase-like activity J. Chem. Sci.
128 523
9. Dimiza F, Papadopoulos A N, Tangoulis V, Psycharis
V, Raptopoulou C P, Kessissoglou D P and Psomas G
2012 Biological evaluation of cobalt(II) complexes with
non-steroidal anti-inflammatory drug naproxen J. Inorg.
Biochem. 107 54
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Ambike V, Amatore C, Collignon G M, Lemaître F and
Policar C 2012 Evaluation of the anti-oxidant properties
of a SOD-mimic Mn-complex in activated macrophages
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Supplementary Information (SI)
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Ligand Conformation: Asymmetric Epoxidation Using
Achiral (Salen)manganese(III) Complex Synlett 783
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cally Active Aldiminato Cobalt(II) Complexes as Effi-
cient Catalysts for Enantioselective Cyclopropanation of
Styrenes with Diazoacetates Chem. Lett. 28 719
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and Ali M 2016 Synthesis, structure, catalytic and mag-
netic properties of a pyrazole based five coordinated
di-nuclear cobalt(II) complex Polyhedron 106 84
14. Yuan J, Wang X, Liu M-J and Kou H-Z 2016 Manganese
(III) complexes derived from 1-(2-hydroxybenzamido)
-2-((2-hydroxy-3-methoxybenzylidene)amino)ethane:
Synthesis, structure and magnetic properties Inorg.
Chim. Acta 449 69
Crystallographic information for all the compounds have
been deposited with the Cambridge crystallographic data
center, (CCDC) as supplementary publications CCDC
1455171, 1469612 and 1455172. The electronic Supplemen-
tary Information is available at www.ias.ac.in/chemsci.
Acknowledgements
We are grateful to the Ministère de l’Enseignement Supérieur
et de la Recherche Scientifique – Algérie (MESRS) for
financial support.
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