Computational studies of 1,2-disubstituted benzimidazole derivatives

Article abstract of DOI:10.1016/j.saa.2012.05.085

Some 1,2-disubstituted benzimidazole derivatives (1-6) have been synthesized and characterized by mass, ¹H, ¹³C NMR and elemental analysis. XRD analysis was carried out for 1-(4-methylbenzyl)-2-p- tolyl-1H-benzo[d]imidazole. Calculat

Full text of DOI:10.1016/j.saa.2012.05.085

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 131–136
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Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Computational studies of 1,2-disubstituted benzimidazole derivatives
⇑
J. Jayabharathi , V. Thanikachalam, K. Jayamoorthy, M. Venkatesh Perumal
Department of Chemistry, Annamalai University, Annamalainagar 608 002, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
"
"
"
"
Steric interaction must be reduced in
order to obtain larger b values.
NBO analysis elucidates the
delocalization within the molecule.
Probable charge transfer (CD) taking
place inside the chromophore.
Charge distribution was calculated
by NBO and Mulliken methods.
0
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 May 2012
Received in revised form 18 May 2012
Accepted 29 May 2012
Available online 6 June 2012
Some 1,2-disubstituted benzimidazole derivatives (1–6) have been synthesized and characterized by
1
13
mass, H, C NMR and elemental analysis. XRD analysis was carried out for 1-(4-methylbenzyl)-2-p-
tolyl-1H-benzo[d]imidazole. Calculated bond lengths, bond angles and thus dihedral angles are found
to be slightly higher than that of X-ray diffraction values of its experimental data. The charge distribution
has been calculated from the atomic charges by non-linear optical (NLO) and natural bond orbital (NBO)
analyses have been calculated by ab initio method. Since the synthesized 1,2-disubstituted benzimid-
Keywords:
AIM
DFT
NLO
NBO
azole derivatives have the largest
g 0
l b value and can be used as potential NLO materials. Analysis of
the molecular electrostatic potential (MEP) energy surface exploited the region for non-covalent interac-
tions in the molecule. Atom in molecule analysis (AIM) was carried out to show the presence of bond crit-
ical points (BCPs).
XRD
MEP
Ó 2012 Elsevier B.V. All rights reserved.
Introduction
centrated on molecules with donor–acceptor
p
-conjugation (D-
p-
A) and deals with the substituent effects on the degree of
p-conju-
Benzimidazole based chromophores have received increasing
attention due to their distinctive linear, non-linear optical proper-
ties and also due to their excellent thermal stability in guest–host
systems [1]. The imidazole ring can be easily tailored to accommo-
date functional groups, which allows the covalent incorporation of
the NLO chromophores into polyamides leading to NLO side chain
gation, steric hindrance and the hyperpolarizability of the sub-
stances [4]. Nowadays there is an insufficient understanding for
designing optimal NLO materials, even certain classes of D-
p-A
compounds were theoretically studied [5]. Not only the push–pull
effect in D-
of the push–pull quotient (
detected [6]. Thus,
p
-A compounds quantified, but also a linear dependence
⁄
p
/
p
) on molar hyperpolarizability were
⁄
polymers [2]. Most
p-conjugated systems play a major role in
p
/p
is a sensitive parameter of the donor–
determining second-order NLO response [3]. Searching organic
acceptor quality of compounds for potential NLO applications.
materials with non-linear optical (NLO) properties is usually con-
Our approach is to design newly -conjugated benzimidazole
p
derivatives to use as materials in material chemistry [7,8]. Hence
there is considerable interest in the synthesis of new materials
with optical non-linearity by virtue of their potential use in device
⇑
Corresponding author. Tel.: +91 9443940735.
E-mail address: jtchalam2005@yahoo.co.in (J. Jayabharathi).
1
386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.05.085

1
32
J. Jayabharathi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 131–136
applications related to telecommunications, optical computing,
optical storage, and optical information processing [9–12]. Herein
we report the synthesis and theoretical studies of some benzimid-
azole derivatives (1–6).
For each donor (i) and acceptor (j), the stabilization energy E(2)
associated with the delocalization i ? j is estimated as
2
Fði; jÞ
Eð2Þ ¼
D
E
ij ¼ qi
ð4Þ
e
j
ꢁ
e
i
where q
i
is the donor orbital occupancy,
e
i
and
e
j
are diagonal ele-
Experimental
ments and F(i,j) is the off diagonal NBO Fock matrix element [15].
The larger the E(2)value, the more intensive is the interaction be-
tween electron donors and electron acceptors, i.e., the more donat-
ing tendency from electron donors to electron acceptors and the
greater the extent of charge transfer or conjugation of the whole
system.
Spectral measurements
NMR spectra were recorded on Bruker 400 MHz NMR spectrom-
eter. Mass spectrum was recorded using Agilant 1100 Mass
spectrometer.
General procedure for the synthesis of ligands
Non-linear optical measurements
A mixture of corresponding aldehyde (2 mmol), o-phenylenedi-
amine (1 mmol) and ammonium acetate (2.5 mmol) has been re-
fluxed at 80 °C in ethanol for appropriate time. The reaction was
monitored by TLC and purified by column chromatography using
petroleum ether: ethyl acetate (9:1) as the eluent.
The non-linear optical conversion efficiencies were parted using
a modified set up of Kurtz and Perry. A Q-switched Nd: YAG laser
beam of wavelength of 1064 nm was used with an input power of
4
.1 mJ/pulse width of 10 ns, scattering geometry 90°, the repetition
rate being 10 Hz, monochromater Jobin Youon Triax 550, slit width
.5 mm, focal length of focusing lens 20 cm, PMT model number
XP2262B used in Philips photonics, power supply for PMT is
.81 KU/mA with oscilloscope Jektronix TDS 3052B.
0
Results and discussion
1
1,2-Disubstituted benzimidazole: X-ray analysis
Computational details
1
-(4-Methyl benzyl)-2-p-tolyl-1H-benzo[d]imidazole [16] is a
ꢀ
triclinic crystal. It crystallizes in the space group P1. The cell dimen-
sions are a = 9.6610 Å, b = 10.2900 Å, c = 17.7271 Å. ORTEP diagram
of 5 (Fig. 1) shows that the benzimidazole ring is essentially planar.
The dihedral angles between the planes of the benzimidazole and
the benzene rings of the 4-methylbenzyl and the p-tolyl groups
are 76.64(3)° and 46.87(4)°, respectively, in molecule A. The corre-
sponding values in molecule B are 86.31(2)° and 39.14(4)°. The dihe-
dral angle between the planes of the two benzene rings is 73.73(3)°
and 80.69(4)° in molecules A and B, respectively. Optimization of 5
have been performed by DFT at B3LYP/6-31G(d,p) using Gaussian-
Quantum mechanical calculations were used to carry out the
optimized geometry, NLO, NBO and HOMO–LUMO analysis with
Gaussian-03 program using the Becke3–Lee–Yang–Parr (B3LYP)
functional supplemented with the standard 6-31G(d,p) basis set
[
13]. As the first step of our DFT calculation for NLO, NBO and
HOMO–LUMO analysis, the geometry taken from the starting
structures were optimized and then, the electric dipole moment
l
and b tensor components of the studied compounds were calcu-
lated, which has been found to be more than adequate for obtain-
ing reliable trends in the first hyperpolarizability values.
We have reported the btot (total first hyperpolarizability) for the
investigated molecules and the components of the first hyperpo-
larizability can be calculated using equation:
0
3. All these XRD data are in good agreement with the theoretical
values (Table 1). However, from the theoretical values it can be
found that most of the optimized bond lengths, bond angles and
dihedral angles are slightly higher than that of XRD values. These
deviations can be attributed to the fact that the theoretical calcula-
tions were aimed at the isolated molecule in the gaseous phase and
the XRD results were aimed at the molecule in the solid state.
X
bi ¼ biii þ 1=3 ðbijj þ bjij þ bjjiÞ
ð1Þ
i–j
Using the x, y and z components, the magnitude of the first
hyperpolarizability tensor can be calculated by
The key twist, designated as
a have been examined. a is used to
indicate the twist of benzimidazole ring from the aromatic six-
membered ring at C-2. The twist originates from the interaction
of substituent at benzyl rig attached nitrogen of the benzimidazole
with the substituent at C-2. The present structural information al-
lows us to further explore the correlation between structural fea-
tures and fluorescent property. When the two adjacent aromatic
species are in a coplanar geometry, the p-orbitals from the C–C
bond connecting the two species will have maximal overlapping
and the two rings will have a rigid and partial delocalized conjuga-
tion, as the result, the bond is no longer a pure single bond, as evi-
dent from the X-ray data.
2
x
2
y
2
1=2
btot ¼ ðb þ b þ b Þ
ð2Þ
z
The complete equation for calculating the magnitude of first
hyperpolarizability from Gaussian-03 output is given as follows:
2
2
btot ¼ ½ðbxxx þ b þ bxzzÞ þ ðb þ byzz þ byxxÞ þ ðb þ bzxx
xyy
yyy
zzz
2
1=2
þ bzyyÞ ꢀ
ð3Þ
All the electric dipole moment and the first hyperpolarizabili-
ties are calculated by taking the Cartesian coordinate system (x,
y, z) = (0, 0, 0) at own center of mass of the compounds.
Second harmonic generation (SHG) studies of 1,2-disubstituted
benzimidazole derivatives
Natural bond orbital (NBO) analysis
NBO analysis have been performed on the molecule at the DFT/
B3LYP/6-31G(d,p) level in order to elucidate the intramolecular,
rehybridization and delocalization of electron density within the
molecule. The second order Fock matrix was carried out to evalu-
ate the donor–acceptor interactions in the NBO analysis [14]. The
interactions result in a loss of occupancy from the localized NBO
of the idealized Lewis structure into an empty non-Lewis orbital.
Second harmonic signals of 45 (1), 47 (2), 51 (3), 46 (4), 54 (5)
and 52 (6) mV was obtained for 1,2-disubstituted benzimidazole
derivatives by an input energy of 4.1 mJ/pulse. But the standard
KDP crystal gave a SHG signal of 110 mV/pulse for the same input
energy. The second order non-linear efficiency will vary with the
particle size of the powder sample [17]. Higher efficiencies are
achieved by optimizing the phase matching [18]. On a molecular

J. Jayabharathi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 131–136
133
Fig. 1. ORTEP diagram of 5 with 30% probability.
Table 1
Selected bond lengths (Å), bond angles (°) and torsional angles (°) of 5.
Bond lengths (Å)
Experimental XRD (Å)
Bond angles (°)
Experimental XRD (°)
Torsional angles (°)
Experimental XRD (°)
N1A–C2A
N1A–C8A
N1A–C1A
N3A–C2A
N3A–C9A
N1B–C2B
N1B–C8B
N1B–C1B
N3B–C2B
N3B–C9B
C1A–C11A
C2A–C21A
C7A–C8A
C8A–C9A
C14A–C17A
C24A–C27A
1.3782(1.4972)
1.3833(1.4584)
1.4537(1.4700)
1.3163(1.3671)
1.3881(1.4606)
1.3795(1.4972)
1.3863(1.4584)
1.4550(1.4700)
1.3174(1.3671)
1.3866(1.4606)
1.5135(1.5400)
1.4729(1.5400)
1.3921(1.3862)
1.3999(1.4763)
1.5089(1.5400)
1.5078(1.5400)
C2A–N1A–C8A
C2A–N1A–C1A
C8A–N1A–C1A
C2A–N3A–C9A
C2B–N1B–C8B
C2B–N1B–C1B
C8B–N1B–C1B
C2B–N3B–C9B
N1A–C1A–C11A
N3A–C2A–N1A
N3A–C2A–C21A
N1A–C2A–C21A
N1A–C8A–C3A
N1A–C8A–C9A
N3A–C9A–C4A
N3A–C9A–C8A
106.23(101.69)
128.33(113.71)
124.79(113.33)
104.77(105.49)
106.27(101.69)
129.32(113.71)
123.98(113.33)
105.12(105.41)
115.07(109.47)
113.25(113.53)
123.44(123.23)
123.30(123.24)
131.76(130.72)
103.49(108.25)
129.91(130.69)
C2A–N1A–C1A–C11A
C8A–N1A–C1A–C11A
C9A–N3A–C2A–N1A
C9A–N3A–C2A–C21A
C8A–N1A–C2A–N3A
C1A–N1A–C2A–N3A
C8A–N1A–C2A–C21A
C1A–N1A–C2A–C21A
C9A–C4A–C5A–C6A
C2A–N1A–C8A–C7A
C1A–N1A–C8A–C7A
C2A–N1A–C8A–C9A
C1A–N1A–C8A–C9A
C6A–C7A–C8A–N1A
C2B–N1B–C1B–C11B
C8B–N1B–C1B–C11B
C9B–N3B–C2B–N1B
C9B–N3B–C2B–C21B
C8B–N1B–C2B–N3B
C1B–N1B–C2B–N3B
C8B–N1B–C2B–C21B
C1B–N1B–C2B–C21B
C9B–C4B–C5B–C6B
C2B–N1B–C8B–C7B
C1B–N1B–C8B–C7B
C2B–N1B–C8B–C9B
C1B–N1B–C8B–C9B
C6B–C7B–C8B–N1B
109.45(ꢁ177.75)
ꢁ81.12(ꢁ62.25)
ꢁ0.02(ꢁ13.69)
ꢁ178.71(165.91)
0.59(17.54)
171.55(139.72)
179.28(ꢁ162.06)
ꢁ9.75(ꢁ39.88)
0.1(ꢁ0.1581)
178.45(166.15)
7.08(43.71)
ꢁ0.88(13.70)
ꢁ172.25(136.15)
179.75(176.19)
108.10(ꢁ177.75)
ꢁ79.66(ꢁ62.25)
ꢁ0.86(ꢁ13.69)
177.35(165.91)
1.24(17.54)
110.26(108.25)
173.85(139.72)
ꢁ176.90(162.06)
ꢁ4.29(ꢁ39.88)
0.25(ꢁ0.1581)
176.39(166.15)
3.28(43.71)
ꢁ1.05(ꢁ13.70)
ꢁ174.15(ꢁ136.15)
177.76(176.19)
Values within the parenthesis corresponds to theoretical values.
scale, the extent of charge transfer (CT) across the NLO chromo-
phore determines the level of SHG output, the greater the CT and
the larger the SHG output.
activity. The ultimate goal in the design of polar materials is to pre-
pare compounds which have their molecular dipole moments
aligned in the same direction [19].
Theoretical investigation plays an important role in under-
standing the structure–property relationship, which is able to as-
sist in designing novel NLO chormophores. The electrostatic first
Comparison of lb
0
hyperpolarizability (b) and dipole moment (
chromophore have been calculated by using Gaussian 03 package
20]. From Table 2, it is found that the 1,2-disubstituted benzimid-
azole derivatives show larger values, which is attributed to
the positive contribution of their conjugation.
l) of the imidazole
The overall polarity of the synthesized 1,2-disubstituted benz-
imidazole derivatives was small when their dipole moment aligned
in a parallel fashion (Fig. 2) .When the electric field is removed, the
parallel alignment of the molecular dipole moments begins to
deteriorate and eventually the imidazole derivative loses its NLO
[
g 0
l b

1
34
J. Jayabharathi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 131–136
component cannot be zero and these are dipolar component. Since
most of the practical applications for second order NLO chromoph-
ores are based on their dipolar components, this strategy is more
appropriate for designing highly efficient NLO chromophores.
Natural bond orbital (NBO) analysis
NBO analysis have been performed for 1,2-disubstituted benz-
imidazole derivatives at the DFT/B3LYP/6-31++G(d,p) level in order
to elucidate the intramolecular, hybridization and delocalization of
electron density within the molecule. The importance of hypercon-
jugative interaction and electron density transfer (EDT) from lone
pair electrons to the antibonding orbital has been analyzed [22].
Several donor–acceptor interactions are observed for the 1,2-
disubstituted benzimidazole derivatives and among the strongly
occupied NBOs, the most important delocalization sites are in the
Fig. 2. Orientation of dipole moments.
Octupolar and dipolar components of 1,2-disubstituted benzimidazole
derivatives
The 1,2-disubstituted benzimidazole derivatives possess a more
appropriate ratio of off-diagonal versus diagonal b tensorial com-
ponent (r = bxyy/bxxx) which reflects the inplane non-linearity
p
system and in the lone pairs (n) of the oxygen, fluorine and nitro-
gen atoms. The system shows some contribution to the delocal-
r
anisotropy and the largest
l
b
o
values. The difference of the bxyy/bxxx
ization, and the important contributions to the delocalization
corresponds to the donor–acceptor interactions are C3–C4 ? C1–
C2, C3–C4 ? C7–N15, C7–N15 ? C1–C2, C8–C10 ? C9–C11, C9–
C11 ? C12–C13, C12–C13 ? C9–C11, C19–C28 ? C20–C22, C20–
C22 ? C19–C21, LP N14 ? C2–C3 and LP N14 ? C7–N15. The
charge distribution of 1,2-disubstituted benzimidazole derivatives
was calculated from the atomic charges by NLO and NBO analysis
(Fig. 3). These two methods predict the same trend, i.e., among the
nitrogen atoms N14 and N15, N14 is considered as more basic site
[23]. The charge distribution shows that the more negative charge
is concentrated on N15 atom whereas the partial positive charge
resides at hydrogens. When compared to nitrogen atoms (N14
and N15), fluorine atom are less electronegative in 1,2-disubsti-
tuted benzimidazole derivatives and among the nitrogen atoms
N14 is considered as more basic site [24].
ratios can be well understood by analyzing their relative molecular
orbital properties. The r values of 1,2-disubstituted benzimidazole
derivatives are 0.0579 (1), ꢁ0.0125 (2), ꢁ0.2037 (3), 0.0772 (4),
ꢁ
0.0800 (5), ꢁ0.2275 (6). The electrostatic first hyperpolarizabili-
0
ties (b ) and dipole moment (l) of the chromophores have been
investigated theoretically. These observed results can be explained
by the reduced planarity in such chromophores caused by the ste-
ric interaction azomethine nitrogen atom. Hence, the steric inter-
action must be reduced in order to obtain larger b
0
values.
2
D
The b tensor [21] can be decomposed in a sum of dipolar ( b)
J¼1
2
D
and octupolar ( b) tensorial components, and the ratio of these
J¼3
two components strongly depends on their ‘r’ ratios. Complying
with the Pythagorean theory and the projection closure condition,
the octupolar and dipolar components of the b tensor can be de-
scribed as:
Molecular electrostatic potential map (MEP) and electronic properties
2
D
2
2
jj bjj ¼ ð3=4Þ½ðbxxx þ bxyyÞ þ ½ðb þ byxxÞ ꢀ
ð5Þ
ð6Þ
J¼1
yyy
2D
2
2
MEP surface diagram (Fig. S4) is used to understand the reactive
behaviour of a molecule, in that negative regions can be regarded
as nucleophilic centres, whereas the positive regions are potential
electrophilic sites. The MEP map of benzimidazole derivatives
clearly suggests that the nitrogen and fluorine atoms represent
jj bjj ¼ ð1=4Þ½ðbxxx ꢁ 3b Þ þ ½ðb þ byxxÞ ꢀ
J¼1
xyy
yyy
h
i
2
D
q2D ¼ jj bjj is convenient to compare the
2D
The parameter
q
J¼1
relative magnitudes of the octupolar and dipolar components of b.
2D
The observed positive small
q
value reveals that the biii
Table 2
Electric dipole moment (
l
), polarizability (
a
) and hyperpolarisability (b) of 1–6.
Parameter
1
2
3
4
5
6
l
l
l
l
x
ꢁ0.5692
ꢁ0.0512
1.2996
ꢁ0.0409
0.4719
0.5524
0.1465
ꢁ3.5160
1.0010
ꢁ2.3685
156.3882
7.9576
ꢁ169.1891
ꢁ3.2932
10.4458
ꢁ162.7973
ꢁ86.7455
7.2463
ꢁ69.4471
ꢁ1.4761
15.2006
42.6434
0.8119
ꢁ0.8743
ꢁ0.4619
0.5048
ꢁ0.8314
293.5637
28.8191
154.5733
6.6294
ꢁ11.4693
221.6728
3.3088
ꢁ708.3375
ꢁ223.2285
ꢁ54.7116
ꢁ80.5413
52.4268
0.1707
ꢁ3.4644
1.2082
0.0572
ꢁ1.5617
ꢁ1.6511
3.1556
y
z
tot
0.6792
0.9834
ꢁ2.0855
a
a
a
a
a
a
a
xx
xy
yy
xz
yz
287.4093
ꢁ1.6580
155.8577
ꢁ1.5185
ꢁ40.6877
227.8743
3.3154
ꢁ608.3990
52.6782
ꢁ35.2133
ꢁ51.1884
ꢁ62.6401
44.8590
46.2349
ꢁ6.6788
2.1320
309.7633
ꢁ53.0280
131.2507
28.3731
ꢁ1.3015
249.4627
3.4109
ꢁ383.9197
52.4608
4.8141
18.1350
ꢁ47.5325
17.2619
43.6417
ꢁ53.8138
63.1668
ꢁ29.2103
39.2501
38.5985
ꢁ117.2774
4.1861
ꢁ120.8744
0.6590
ꢁ137.9645
ꢁ1.2303
ꢁ0.4711
ꢁ144.0098
ꢁ1.9723
ꢁ44.3386
ꢁ39.2493
3.5490
ꢁ152.7575
11.5158
2.0492
zz
ꢁ151.0374
ꢁ2.0978
111.2710
ꢁ3.5024
ꢁ25.3174
10.9727
ꢁ35.3616
ꢁ34.4533
ꢁ16.6196
ꢁ13.9812
ꢁ18.5493
3.9319
tot ꢂ 10ꢁ
23
b
b
b
b
b
b
b
b
b
b
b
xxx
xxy
xyy
yyy
xxz
xyz
yyz
xzz
yzz
13.1731
5.1746
4.9552
7.5525
ꢁ21.1557
ꢁ11.6743
79.8413
ꢁ2.9465
14.0433
18.7322
ꢁ18.2658
ꢁ0.6432
4.5697
ꢁ29.9926
ꢁ7.6853
ꢁ16.4025
3.6761
6.2666
ꢁ14.8424
zzz
82.9746
56.4751
38.3579
ꢁ
31
tot ꢂ 10
74.0178
61.5384
7.5372
23.7844
ꢁ
31
l
ꢂ b
0
ꢂ 10
ꢁ9.5301

J. Jayabharathi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 131–136
135
Fig. 3. Mulliken charge distribution of 1–6 using NLO and NBO methods.
the most negative potential region. The hydrogen atoms bear the
maximum brunt of positive charge. The predominance of green re-
gion in the MEP surfaces corresponds to a potential halfway be-
tween the two extremes red and dark blue color.
DFT calculations, it was concluded that molecules of higher hyper-
polarizability have larger dipole moments used as potential NLO
molecules. The MEP map of benzimidazole derivatives clearly sug-
gests that the nitrogen, bromine and fluorine atoms represent the
most negative potential region. The hydrogen atoms bear the max-
imum brunt of positive charge. From AIM analysis the presence of
bond critical points (BCPs) of the intramolecular bonds and their
energies was evaluated.
Atoms in molecules analysis of 4
The AIM analysis was used to determine the presence of bond
critical points (BCPs) of the intramolecular bonds and to evaluate
their energies. The most often used criteria of the existence of
hydrogen bonding interactions are the electron density r(rc) and
the Laplacian of the electron density V2r(rc) at the BCPs. These
parameters for the intramolecular along with the lengths and an-
gles of the corresponding hydrogen bonds in the studied molecules
are 2.012 Å, 127.8°, respectively. There is good correlation between
the r(rc) and V2r(rc) values. Positive values of Laplacian V 2r(rc)
Acknowledgments
One of the authors Prof. J. Jayabharathi is thankful to DST [No.
SR/S1/IC-73/2010], UGC (F.No. 36-21/2008 (SR)) and DRDO (NRB-
2
13/MAT/10-11) for providing funds to this research study.
Appendix A. Supplementary data
(
2.001) indicative of depletion of electronic charge along the bond
path, which is characteristic of closed shell interactions such as
hydrogen bonds.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2012.05.085.
Conclusion
References
In this paper we have reported benzimidazole based chromoph-
[
1] E.M. Across, K.M. White, R.S. Moshrefzadeh, C.V. Francis, Macromolecules 28
1995) 2526.
2] X.R. Bu, H. Li, D.V. Derveer, E.A. Mintz, Tetrahedron Lett. 37 (1996) 7331.
ores as potential NLO materials. The presence of
a twist in this
(
benzimidazole drops the fluorescence quantum yield. The ob-
served dipole moment and hyperpolarisability can be explained
by the reduced planarity caused by the steric interaction in nitro-
gen atom attached to benzyl ring. Hence, the steric interaction
[
[3] C.W. Dirk, H.E. Katz, M.L. Schilling, L.A. King, Chem. Mater. 2 (1990) 700.
[
[
[
4] K. Mahanalingam, M. Nethaji, P.K. Das, J. Mol. Struct. 378 (1996) 177–188.
5] R. Koch, J.J. Finnerty, T. Bruhn, J. Phys. Org. Chem. 21 (2008) 954–962.
6] E. Kleinpeter, A. Koch, B. Mikhova, B.A. Stamboliyska, T.M. Kolev, Tetrahedron
Lett. 49 (2008) 1323–1327.
0
must be reduced in order to obtain larger b values. From the

1
36
J. Jayabharathi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 97 (2012) 131–136
[
7] C.R. Moylan, R.D. Miller, R.J. Twieg, K.M. Betterton, V.Y. Lee, T.J. Matray, C.
Nguyen, Chem. Mater. 5 (1993) 1499.
8] M. Ammamm, P. Bauerle, Org. Biomol. Chem. 3 (2005) 4143.
9] S.R. Marder, J.E. Sohn, G.D. Stucky (Eds.), Materials for non-linear optics:
chemical perspectives. In: ACS Symposium Series, vol. 455, American Chemical
Society, Washington, DC, 1991.
[20] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
J.A. Montgomery, T. Vreven Jr., K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, P.
Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O.
Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K.
Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S.
Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J.
Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L.
Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M.
Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A.
Pople, Gaussian 03, Revision C.02, Gaussian, Inc., Wallingford, CT, 2004.
[21] S.F. Tayyari, S. Laleh, Z.M. Tekyeh, M.Z. Tabrizi, Y.A. Wang, H. Rahemi, Mol.
Struct. 827 (2007) 176–187.
[
[
[
[
10] J. Messier, F. Kajzar, P. Prasad (Eds.), Organic Molecules for Non-linear Optics
and Photonics, Kluwer Academic, Dordrecht, 1991.
11] L.R. Dalton, A.W. Harper, R. Ghosn, W.H. Steir, M. Ziari, H. Fetterman, Y. Shi,
R.V. Mustacich, A.K.Y. Jen, K.J. Shea, Chem. Mater. 7 (1995) 1060.
12] R.G. Benning, J. Mater. Chem. 5 (1995) 365.
13] M. Szafran, A. Komasa, E.B. Adamska, J. Mol. Struct. 827 (2007) 101–107.
14] L. Padmaja, C. Ravikumar, D. Sajan, I. Hubert Joe, V.S. Jayakumar, G.R. Pettit, O.
Faurskov Neilsen, J. Raman Spectrosc. 40 (2009) 419–428.
[
[
[
[
[
[
15] C. Ravikumar, I. Hubert Joe, V.S. Jayakumar, Chem. Phys. Lett. 460 (2008) 552–
5
58.
16] S. Rosepriya, A. Thiruvalluvar, K. Jayamoorthy, J. Jayabharathi, Antony Linden,
Acta Crystallogr. E 67 (2011) o3519.
17] Y. Porter, K.M. OK, N.S.P. Bhuvanesh, P.S. Halasyamani, Chem. Mater. 13 (2001)
[22] J. Marshal, Ind. J. Phys. 7213 (1988) 659–661.
[23] P. Wang, P. Zhu, W. Wu, H. Kang, C. Ye, Phys. Chem. Chem. Phys. 1 (1999)
3519–3525.
1
910–1915.
[24] G. Wang, F. Lian, Z. Xie, G. Su, L. Wang, X. Jing, F. Wang, Synth. Met. 131 (2002)
1–5.
[
[
18] M. Narayana Bhat, S.M. Dharmaprakash, J. Cryst. Growth 236 (2002) 376–380.
19] D. Steiger, C. Ahlbrandt, R. Glaser, J. Phys. Chem. B 102 (1998) 4257–4260.