Quantum mechanical and spectroscopic (FT-IR, FT-Raman, 1H NMR and UV) investigations of 2-(phenoxymethyl)benzimidazole

Article abstract of DOI:10.1016/j.saa.2014.01.068

The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of 2-(phenoxymethyl)benzimidazole have been investigated experimentally and theoretically using Gaussian09 software package. The energy and oscillator streng

Full text of DOI:10.1016/j.saa.2014.01.068

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 12–24
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
1
Quantum mechanical and spectroscopic (FT-IR, FT-Raman, H NMR
and UV) investigations of 2-(phenoxymethyl)benzimidazole
Y. Shyma Mary a,b, , P.J. Jojo , C. Yohannan Panicker , Christian Van Alsenoy , Sanaz Ataei , Ilkay Yildiz
⇑
b
c
d
e
f
a
Department of Physics, Bharathiar University, Coimbatore, Tamil Nadu, India
Department Physics, Fatima Mata National College, Kollam, Kerala, India
Department of Physics, TKM College of Arts and Science, Kollam, Kerala, India
Department of Chemistry, University of Antwerp, B2610 Antwerp, Belgium
Ankara University, Institute of Biotechnology, 06100 Tandogan, Ankara, Turkey
Ankara University, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, 06100 Tandogan, Ankara, Turkey
b
c
d
e
f
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
ꢀ
ꢀ
IR, Raman spectra and NBO analysis
were reported.
The wavenumbers are calculated
theoretically using Gaussian09
software.
ꢀ
ꢀ
The wavenumbers are assigned using
PED analysis.
The geometrical parameters are in
agreement with that of similar
compounds.
a r t i c l e i n f o
a b s t r a c t
Article history:
The optimized molecular structure, vibrational frequencies, corresponding vibrational assignments of
-(phenoxymethyl)benzimidazole have been investigated experimentally and theoretically using
Received 17 October 2013
Received in revised form 21 December 2013
Accepted 8 January 2014
2
Gaussian09 software package. The energy and oscillator strength calculated by time dependent density
functional theory results almost compliments with experimental findings. Gauge-including atomic
Available online 24 January 2014
1
orbital H NMR chemical shifts calculations were carried out and compared with experimental data.
The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. The stability
of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed
using NBO analysis. Molecular Electrostatic Potential was performed by the DFT method and the
infrared intensities and Raman activities have also been reported. Mulliken’s net charges have been
calculated and compared with the atomic natural charges. First hyperpolarizability is calculated in order
to find its role in non-linear optics.
Keywords:
FT-IR
FT-Raman
Benzimidazole
Hyperpolarizability
PED
Ó 2014 Elsevier B.V. All rights reserved.
Introduction
[8] as well as casein kinase-2 and -5 [9]. Despite a numerous at-
tempts to develop new structural prototype in the search for more
Benzimidazole and its derivatives take part in several biological
processes. They show pharmaceutical activity [1–7], such as
lowering of blood sugar level, inhibition of phosphodiesterase-5
effective antimicrobials, the benzimidazoles still remain as one of
the most versatile class of compounds against microbes [10–17]
and, therefore, are useful substructures for further molecular
exploration. The chemistry and biological profiles of various
pharmacophores of 1N-substituted and 2-substituted benzimidaz-
oles derivatives have been worked out in detail [18–29].
Benzimidazole-containing heterocyclic moieties have found
⇑
Corresponding author at: Department of Physics, Bharathiar University,
Coimbatore, Tamil Nadu, India. Tel.: +91 9995901472.
E-mail address: yshymamary@rediffmail.com (Y.S. Mary).
1
386-1425/$ - see front matter Ó 2014 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2014.01.068

Y.S. Mary et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 12–24
13
extensive use in agriculture [30]. The benzimidazole scaffold is an
accepted pharmacophore and represents an important synthetic
precursor in new drug discovery [31–38]. Yildiz-Oren et al. [39]
synthesized 2-(phenoxymethyl)benzimidazole according to the
protocol reported by King and Acheson [40] for the evaluation of
microbiological activity. The minimum inhibitory concentrations
(
MIC) of the title compound against Staphylococcus aureus, Strepto-
coccus faecalis, Bacillus subtilis as Gram-positive and Escherichia coli,
Klebsiella pneumoniae, Pseudomonas aeruginosa as Gram negative
bacteria were obtained by using twofold serial dilution technique
and compared to ampicillin, amoxycillin, tetracycline, streptomy-
cin, clotrimazole and haloprogin as standard drugs. According to
this study, the title structure was found to be moderately potent
either against S. aureus, S. faecalis, B. subtilis E. coli, K. pneumoniae,
Scheme 1. Synthetic pathway of 2-(phenoxymethyl)benzimidazole.
15 ml 6 N HCl. At the end of the reaction period, the mixture was
neutralized with excess of NaHCO . The collected precipitate
washed with water, dried in vacuum, purified by flash chromatog-
raphy, eluting with CHCl and re-crystallized by using EtOH-H O.
3
P. aeruginosa (MIC values of 25, 50, 25, 50, 25, 50 lg/mL, respec-
tively). Besides, this compound showed more potent than the
3
2
standart drug streptomycine against S. faecalis. Moreover,
mp: 159–161 °C, yield 94%, reaction temperature 100 °C. Elemental
analysis: C% 75.00 (calculated), 74.76 (found); H% 5.35 (calculated),
5.31 (found); N% 12.50 (calculated), 12.58 (found).
2
-(phenoxymethyl)benzimidazole exhibited significant antibacte-
rial activity with MIC values of 25 g/mL for the Gram-negative
l
enterobacter P. aeruginosa, which is effective in nosocomial infec-
tions and often resistant to antibiotic therapy, providing higher
potencies than the compared standard drugs. Considering the
enormous biological importance, 2-(phenoxymethyl)benzimid-
azole is re-synthesized and the detailed experimental and theoret-
ical normal Raman spectroscopy, and FTIR spectra are reported in
the present work. Ab initio quantum mechanical method is at pres-
ent widely used for simulating IR spectrum. Such simulations are
indispensable tools to perform normal coordinate analysis so that
modern vibrational spectroscopy is unimaginable without involv-
ing them and time-dependent DFT (TD-DFT) calculations have also
been used for the analysis of the electronic spectrum and spectro-
scopic properties. The energies, degrees of hybridization, popula-
The FT-IR spectrum (Fig. 1) was recorded using KBr pellets on a
DR/Jasco FT-IR 6300 spectrometer. The FT-Raman spectrum (Fig. 2)
was obtained on a Bruker RFS 100/s, Germany. For excitation of the
spectrum the emission of Nd:YAG laser was used, excitation wave-
length 1064 nm, maximal power 150 mW, measurement on solid
1
sample. H NMR spectra were obtained with a Bruker AC 80 MHz
spectrometer and TMS was used as an internal standard.
Computational details
Calculations of the title compound are carried out with Gauss-
ꢁ
ꢁ
ian09 program [43] using the HF/6-31G , B3LYP/6-31G and
B3LYP/SDD basis sets to predict the molecular structure and vibra-
tional wavenumbers. Molecular geometry was fully optimized by
Berny’s optimization algorithm using redundant internal coordi-
nates. Harmonic vibrational wavenumbers are calculated using
the analytic second derivatives to confirm the convergence to min-
ima on the potential surface. The wavenumber values computed at
the Hartree–Fock level contain known systematic errors due to the
negligence of electron correlation [44]. We therefore, have used the
tions of the lone electron pairs of oxygen, energies of their
ꢁ
interaction with the anti bonding
p
orbital of the benzene ring,
electron density (ED) distributions and E(2) energies have been
calculated by NBO analysis using DFT method to give clear evi-
dence of stabilization originating from the hyper conjugation of
various intra-molecular interactions. In the present work, IR,
1
Raman spectra, H NMR parameters and UV–Vis spectrum of
2
-(phenoxymethyl)benzimidazole are reported both experimen-
ꢁ
tally and theoretically. The HOMO and LUMO analysis have been
used to elucidate information regarding charge transfer within
the molecule. There has been growing interest in using organic
materials for nonlinear optical (NLO) devices, functioning as
second harmonic generators, frequency converters, electro-optical
modulators, etc. because of the large second order electric suscep-
tibilities of organic materials. Since the second order electric
susceptibility is related to first hyperpolarizability, the search for
organic chromophores with large first hyperpolarizability is fully
justified. The organic compounds showing high hyperpolarizability
are those containing an electron donating group or an electron
withdrawing group interacting through a system of conjugated
double bonds. In this case, the electron withdrawing group AOPh
is present in the title compound.
scaling factor value of 0.8929 for HF/6-31G basis set. The DFT
hybrid B3LYP functional and SDD methods tend to overestimate
the fundamental modes; therefore scaling factor of 0.9613 has to
be used for obtaining a considerably better agreement with exper-
imental data [44]. The Stuttagart/Dresden effective core potential
basis set (SDD) [45] was chosen particularly because of its advan-
tage of doing faster calculations with relatively better accuracy and
structures [46]. Then frequency calculations were employed to
confirm the structure as minimum points in energy. Parameters
corresponding to optimized geometry (SDD) of the title compound
(Fig. 3) are given in Table S1 as Supporting material. The absence of
imaginary wavenumbers on the calculated vibrational spectrum
confirms that the structure deduced corresponds to minimum
energy. The assignments of the calculated wavenumbers are aided
by the animation option of GAUSSVIEW program, which gives a
visual presentation of the vibrational modes [47]. The potential
energy distribution (PED) is calculated with the help of GAR2PED
Experimental details
1
software package [48]. The H NMR data were obtained from the
ꢁ
The title compound was prepared involving the reaction of
o-phenylenediamine with phenoxyacetic acid in the presence of
dehydrating agents in one step procedure as shown in Scheme
DFT method using basis set 6-31G . The characterization of excited
states and electronic transitions were performed using the
time-dependent DFT method (TDB3LYP) on their correspondingly
optimized ground state geometries. We used the time-dependent
density functional theory (TD-DFT), which is found to be an
accurate method for evaluating the low-lying excited states of mol-
ecules and has been thoroughly applied to solve physical and
chemical problems. Vertical excitation energies were computed
1[39,41]. During the synthesis of 2-(phenoxymethyl)benzimid-
azole aqueous hydrochloric acid was used as the condensation
reagent according to well-known Philips’ method [42]. A mixture
of phenoxyacetic acid (10 mmol) and o-phenylenediamine
(
10 mmol) was boiled under reflux with stirring for 2.5 h in

1
4
Y.S. Mary et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 12–24
Fig. 1. FT-IR spectrum of 2-(phenoxymethyl)benzimidazole.
Fig. 2. FT-Raman spectrum of 2-(phenoxymethyl)benzimidazole.
Fig. 3. Optimized geometry (SDD) of 2-(phenoxymethyl)benzimidazole.
ꢂ1
for the first 30 singlet excited states, in order to reproduce the
experimental electronic spectra. Potential energy surface scan
studies have been carried out to understand the stability of planar
and non-planar structures of the molecule.
bands [49–52] are expected in the range 1672–1566 cm . Saxena
ꢂ1
et al. [50] reported a value 1608 cm for polybenzodithiazole and
Klots and Collier [53] reported a value of 1517 cm for benzoxaz-
ꢂ1
ole as
t
C@N stretching mode. Yang et al. [54] reported a band at
ꢂ1
1
626 cm in the IR spectrum as
t
C@N for the oxazole ring. For
C@N mode at
1522 cm , 1523 cm in IR and 1517 cm in Raman which is in
the title compound, the SDD calculations give
t
ꢂ1
ꢂ1
ꢂ1
Results and discussion
agreement with reported literature [55].
IR and Raman spectra
In aromatic compounds the
t
NH appears in the region
ꢂ1
3
400 ± 40 cm [56]. For the title compound the SDD calculation
ꢂ1
The observed IR and Raman bands, calculated (scaled) wave-
numbers and assignments are given in Table 1. The C@N stretching
give a value of 3546 cm
for this tNH mode and a band is
ꢂ1
observed in the IR spectrum at 3547 cm . NAH group show bands

Y.S. Mary et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 12–24
15
Table 1
Vibrational assignments of 2-(phenoxymethyl)benzimidazole.
ꢁ
ꢁ
HF/6-31G
B3LYP/6-31G
B3LYP/SDD
IR
Raman assignments
t
IR
I
R
A
t
IR
I
R
A
t
IR
I
R
A
t
t
–
3
3
3
3
3
3
3
3
3
2
2
2
1
526
040
037
035
025
023
010
010
001
998
924
878
635
129.14
0.16
59.15
272.64
6.22
3552
3114
3108
3108
3098
3096
3083
3083
3075
3072
29,621
2919
1619
84.07
2.31
6.37
27.82
35.87
29.94
14.56
12.69
2.05
88.26
3546
3116
3108
3107
3099
3098
3084
3082
3074
3071
2978
2925
1609
97.08
3.51
91.85
3547
3174
–
–
–
3094
–
–
–
–
–
–
–
–
–
t
t
t
t
t
t
t
t
t
t
t
t
t
t
t
NH(99)
219.41
292.03
16.59
82.22
126.69
117.72
127.16
43.66
50.82
59.82
243.55
5.05
316.34
243.46
6.47
CHII(99)
CHI(94)
CHII(93)
CHII(99)
CHI(97)
CHI(97)
CHII(100)
CHII(91)
CHI(96)
16.19
17.28
39.15
30.02
16.36
13.01
1.40
1.28
17.91
9.08
22.69
24.49
33.70
29.09
13.34
10.39
2.51
208.15
80.22
111.41
109.41
115.75
43.22
50.40
51.89
136.42
5.09
41.82
78.60
93.19
104.88
30.26
35.63
45.19
256.50
4.73
–
–
3075
3066
2981
2935
1628
0.61
0.67
3056
2968
2912
1620
19.25
13.16
9.54
19.29
18.58
7.29
asCH
CH
2
(100)
(100)
s
2
22.14
PhI(57),
PhII(15)
PhII(67),
1614
1600
1595
1571
1503
1491
1487
1460
1455
1419
94.91
25.39
1.79
21.27
16.13
40.47
113.24
3.09
1598
1584
1579
1531
1497
1484
1481
1457
1442
1395
66.05
31.97
0.35
16.89
30.82
50.82
153.10
7.99
1588
1572
1569
1522
1469
1458
1455
1428
1420
1384
84.33
31.36
0.41
19.61
42.76
50.37
168.60
8.23
1594
–
1590
–
dCHII(13)
PhII(54),
dCHII(11)
t
1543
1523
1493
–
1568
1517
1480
1457
1449
–
t
t
t
t
PhI(56),
C@N(23)
C@N(54),
PhI(17)
94.62
79.35
45.03
8.68
58.12
34.79
73.80
0.55
56.75
20.10
401.28
16.95
5.81
dCH
dCHII(23)
PhII(58),
dCHII(25)
PhI(50),
dCHI(33)
PhII(53),
dCHII(23)
PhI(63),
dCHI(20)
CN(12),
dCH (54),
2
(50),
7.56
21.08
18.39
2.39
10.43
9.93
t
9.64
1442
–
t
5.56
2.06
3.33
2.11
t
27.64
112.63
10.81
1.32
17.62
76.41
29.39
2.89
27.36
64.05
32.11
2.91
1400
–
1425
1370
t
t
2
dNH(12),
dCHI(10)
1365
1342
1328
1289
1252
1238
1226
1224
1222
1194
139.39
0.70
5.01
1.34
1364
1341
1336
1314
1303
1251
1219
1212
1191
1189
20.01
105.12
2.89
19.17
8.39
1357
1338
1323
1303
1286
1241
1205
1202
1187
1181
27.79
91.89
20.95
2.06
13.10
5.61
1357
1335
1315
1292
1270
1249
1216
1199
–
–
1336
1314
1301
1272
1242
1219
1199
–
tPhI(50),
dCHI(16)
dNH(47),
t
t
PhII(21)
PhII(42),
51.23
1.03
13.02
17.12
21.66
62.34
11.81
21.38
2.55
3.05
5.09
dCHII(29)
dCHII(48),
dPhII(21)
0.56
1.81
0.52
263.89
81.85
5.76
10.37
30.51
357.18
14.35
2.91
2.69
16.97
28.94
314.07
72.86
1.39
3.03
t
t
t
CN(46),
PhI(43)
CN(38),
85.16
4.34
102.74
3.06
dCHI(41)
dCH (46),
2
dCHII(26)
dNH(18),
31.66
102.54
21.87
38.36
13.80
7.89
26.77
11.43
10.66
t
t
CN(52)
COC(55),
dNH(18)
dNH(23),
9.91
58.19
35.87
–
1176
t
CN(28),
dPhI(18)
1
1
178
147
4.34
3.83
5.63
1.33
1182
1172
13.99
12.10
5.05
3.94
1167
1155
23.99
10.03
5.26
2.75
1169
1152
–
1154
dCHII(75)
dCHII(80),
t
PhII(12)
dCHI(77),
PhI(16)
dCHI(52),
1146
1111
1077
8.28
0.27
9.08
11.11
0.71
1159
1112
1083
2.61
0.77
8.99
17.43
13.10
1.61
1145
1095
1068
1.99
2.65
13.78
11.17
1.07
–
1107
1077
1120
1109
1084
t
t
t
PhI(32)
PhI(38),
13.19
14.95
dCHII(30),
dCHI(32)
dCHII(57),
dCHI(18)
1
1
1
048
038
038
1.51
0.11
0.59
0.85
5.08
1023
1022
1011
19.44
0.07
10.61
0.87
1012
1007
996
0.09
38.71
14.19
0.38
13.13
30.85
1020
1007
998
1026
–
t
PhII(51),
dCHII(22)
dPhII(27),
dPhI(42)
75.16
113.87
19.05
997
(
continued on next page)

1
6
Y.S. Mary et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 12–24
Table 1 (continued)
ꢁ
ꢁ
HF/6-31G
B3LYP/6-31G
B3LYP/SDD
IR
Raman assignments
t
IR
I
R
A
t
IR
I
R
A
t
IR
I
R
A
t
t
–
1
037
019
017
007
0.02
0.01
1.58
4.53
0.98
0.25
4.24
1003
21.03
6.29
35.96
991
0.76
0.27
–
–
–
–
–
–
–
–
–
c
CHII(81),
s
PhII(15)
COC(51),
dPhII(22)
CHI(87),
PhI(11)
dPhII(42),
1
1
1
989
982
974
21.68
0.34
988
982
972
13.69
0.02
23.26
0.25
t
0.39
c
s
54.98
32.57
0.65
0.68
37.75
t
c
t
PhII(14)
CHII(90)
COC(18),
9
9
94
89
6.01
2.06
0.09
16.97
972
953
0.01
0.01
0.09
0.41
968
960
0.05
20.78
0.08
1.51
–
958
959
2
dCH (52)
9
9
81
43
8.76
18.25
4.03
1.82
929
889
2.81
8.48
0.44
2.74
944
898
4.90
9.57
1.07
0.15
921
902
–
902
c
c
CHI(91)
CHII(77),
s
PhII(13)
8
99
88
0.28
1.76
1.86
885
853
2.58
0.01
1.85
3.58
870
862
1.83
0.04
1.59
0.98
878
841
879
864
dPhI(61),
dRingIII(11)
8
1.64
c
CHI(74),
s
PhI(11)
8
8
64
21
0.05
29.63
2.83
3.86
820
819
0.02
9.92
4.55
1.25
825
808
0.20
7.07
0.01
4.56
814
–
830
811
c
t
CHII(99)
PhI(30),
dRingIII(34)
8
08
6.11
35.59
809
13.59
41.92
795
17.51
42.97
783
785
tPhII(16),
dPhII(28),
dCCO(19)
7
89
85
1.39
2.66
0.07
757
754
8.86
2.48
0.30
771
758
9.05
0.98
0.07
–
–
s
s
c
PhI(52),
RingIII(31)
CHII(57),
7
199.51
105.51
147.55
769
759
s
PhII(21),
c
c
CO(16)
CHI(78)
7
7
82
07
68.58
33.54
0.94
1.26
750
709
58.48
2.69
2.63
5.04
757
697
78.73
3.67
0.28
5.74
749
–
749
690
dRingIII(33),
dPhI(32)
7
06
2.99
5.87
689
19.79
0.94
687
37.14
0.17
687
–
sPhII(69),
c
c
CHII(20)
NH(95)
6
6
85
56
50.51
80.80
4.72
1.19
648
647
19.42
97.18
2.62
1.55
668
650
84.64
0.01
0.31
2.55
–
652
670
654
s
RingIII(52),
c
CC(23)
6
24
0.26
3.14
622
0.37
3.20
609
0.42
10.93
613
619
dRingIII(42),
dPhI(35)
6
5
22
98
0.72
0.53
10.82
2.06
619
597
0.31
0.82
10.49
2.47
608
584
0.62
0.50
7.99
4.52
–
589
–
581
dPhII(85)
dPhII(41),
dPhI(28)
5
89
15
4.18
5.51
0.04
0.64
578
508
0.61
2.09
0.07
3.54
577
501
0.92
0.08
5.32
–
545
–
s
s
PhI(65),
RingIII(18)
5
12.56
507
dCC(21),
dPhI(21),
dCOC(29)
5
5
4
05
04
47
16.74
0.63
4.18
1.64
0.53
505
501
432
15.34
4.85
4.08
1.87
0.42
0.52
499
498
433
10.59
4.29
8.28
0.24
0.77
0.56
–
487
426
491
491
442
c
CO(41),
s
PhII(40)
dPhII(39),
dPhI(33)
6.34
s
s
s
PhI(58),
RingIII(28)
PhII(84)
4
24
03
0.03
5.05
0.16
2.38
415
405
0.03
4.89
0.14
2.69
410
401
0.06
5.37
0.07
3.42
413
405
–
398
4
dCO(43),
dPhI(28)
3
17
0.15
0.55
306
0.13
0.26
311
0.11
0.08
–
314
cCC(31),
s
s
s
s
PhI(27),
RingIII(16)
PhI(69),
2
2
2
1
1
59
40
36
66
45
5.29
1.09
0.95
2.24
10.67
3.99
0.92
0.58
0.67
2.90
2.99
0.79
4.42
8.91
0.26
0.78
252
238
232
170
142
74
3.49
0.69
0.75
2.11
8.35
1.86
1.03
0.09
0.80
2.95
2.56
0.72
4.32
9.99
0.41
0.51
249
236
229
168
149
80
4.33
0.86
0.17
2.16
11.27
1.76
1.11
0.04
0.64
3.53
1.97
0.90
2.66
9.20
0.42
0.28
–
–
–
–
–
–
–
–
255
238
–
RingIII(22)
dCC(38),
dPhI(28)
s
s
dCO(53),
dCC(15)
s
s
s
s
PhII(57),
CC(15)
173
144
96
RingIII(34),
CC(29),
CO(69),
CC(10)
cCC(16)
6
5
2
9
6
9
58
58
65
dCC(51),
dCO(26)
sCC(82)
28
31
–

Y.S. Mary et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 12–24
17
Table 1 (continued)
ꢁ
ꢁ
HF/6-31G
B3LYP/6-31G
B3LYP/SDD
IR
Raman assignments
t
IR
I
R
A
t
IR
I
R
A
t
IR
I
R
A
t
t
–
1
5
3.04
1.26
10
4.09
2.02
18
3.99
1.36
–
–
s
c
c
CC(61),
NH(15),
CC(14)
t
– stretching; d – in-plane deformation;
c
– out-of-plane deformation;
s
– torsion; as – asymmetric; s – symmetric; PhI – di-substituted benzene ring; PhII – mono
– IR intensity; R – Raman activity.
substituted benzene ring; RingIII – benzimidazole ring; potential energy distribution (%) is given in brackets in the assignment column; IR
I
A
ꢂ1
ꢂ1
at 1510–1500, 1350–1250 and 740–730 cm [57]. According to
IR spectrum and at 3066, 3075 cm in the Raman spectrum are as-
signed as the CAH modes of the benzene rings.
literature, if NAH is a part of a closed ring [57,58] the CANAH
deformation band is absent in the region 1510–1500 cm . For
t
ꢂ1
Since the identification of all the normal modes of vibration of
large molecules is not trivial, we tried to simplify the problem by
considering each molecule as substituted benzene. Such an idea
has already been successfully utilized by several workers for the
vibrational assignments of molecules containing multiple homo
and hetero aromatic rings [67–71]. In the following discussion,
the mono-substituted and di-substituted phenyl rings are desig-
nated as rings PhII and PhI, respectively and benzimidazole as ring-
III. The modes in the two phenyl rings will differ in wavenumber
and the magnitude of splitting will depend on the strength of inter-
actions between different parts (internal coordinates) of the two
rings. For some modes, this splitting is so small that they may be
considered as quasi-degenerate and for the other modes a signifi-
cant amount of splitting is observed. Such observations have al-
ready been reported [67–69,72].
the title compound the CANAH deformation band is observed at
ꢂ1
ꢂ1
1
336 cm in the Raman spectrum, 1335 cm in the IR spectrum
ꢂ1
and at 1338 cm theoretically (SDD). The out of plane NH defor-
ꢂ1
mation is expected in the region 650 ± 50 cm [56] and the band
ꢂ1
ꢂ1
at 670 cm in the Raman spectrum and at 668 cm theoretically
SDD) are assigned as this mode. Minitha et al. [59] reported NH
NH at 535 cm . Panicker
et al. reported the out-of-plane bending mode of NH at 746 cm
theoretically [60]. Kim et al. reported [61] NH deformation bands
at 549, 1484 cm in the Raman spectrum and at 556, 1495 cm
theoretically for benzimidazole and Malek et al. [62] reported
modes at 1394, 680 cm theoretically as NH deformation.
(
t
ꢂ1
ꢂ1
ꢂ1
at 3469 cm , dNH at 1300 cm and
c
ꢂ1
,
ꢂ1
ꢂ1
ꢂ1
Primary aromatic amines with nitrogen directly on the ring ab-
sorb strongly at 1330–1260 cm due to stretching of the phenyl
ꢂ1
carbon–nitrogen bond [63]. Sandhyarani et al. [64] reported
t
CN
The benzene ring possesses six ring stretching vibrations, of
which the four with the highest wavenumbers (occurring respec-
ꢂ1
at 1318 cm for 2-mercaptobenzothiazole. For the title compound
ꢂ1
ꢂ1
t
1
(
CN are assigned at 1270, 1249, 1199 cm in the IR spectrum,
tively near 1600, 1580, 1490 and 1440 cm ) are good group vibra-
ꢂ1
ꢂ1
272, 1242, 1199 cm in the Raman spectrum and the calculated
SDD) values are 1286, 1241, 1202 cm . These modes are not pure
tions. In the absence of ring conjugation, the band near 1580 cm
ꢂ1
ꢂ1
is usually weaker than that at 1600 cm . The fifth ring stretching
vibration is active near 1355 ± 35 cm , a region which overlaps
ꢂ1
but contain a significant contribution from other modes. For 5-ni-
tro-2-(4-nitrobenzyl) benzoxazole, CAN stretching vibrations are
strongly with that of the CH in-plane deformation and the intensity
is in general, low or medium [56,73]. The sixth ring stretching
vibration or ring breathing mode appears as a weak band near
ꢂ1
observed in the region at 1228–1195 cm
modes are reported at 1268, 1220, 1151 cm
benzimidazolium salts by Malek et al. [62].
[55]. CN stretching
ꢂ1
theoretically for
ꢂ1
1000 cm in mono-substituted benzenes [56].
ꢂ1
For the title compound, as expected the asymmetric CAOAC
For the title compound, the bands observed at 1594, 1315 cm
ꢂ1
ꢂ1
stretching vibration is assigned at 1187 cm and the symmetric
in the IR and 1590, 1457, 1314 cm in the Raman spectrum are as-
ꢂ1
ꢂ1
stretching mode at 988 cm (SDD) theoretically [51]. The CAOAC
signed as
tPhII modes with 1588, 1572, 1458, 1428, 1323 cm as
ꢂ1
stretching modes are reported at 1250 and 1073 cm for 2-merc-
SDD values. For the title compound, PED analysis gives the ring
ꢂ1
patobenzoxazole [65]. Bhagyasree et al. [55] reported CAOAC
breathing mode of PhII at 1007 cm [74]. For the phenyl ring
ꢂ1
stretching modes at 1144, 1063 (IR), 1146, 1066 (Raman) and at
PhI, the bands observed at 1620, 1543, 1442, 1400, 1270 cm in
ꢂ1
ꢂ1
1
153, 1079 cm theoretically (SDD).
the IR spectrum and at 1628, 1568, 1449, 1425, 1272 cm in the
The vibrations of the CH
symmetric stretch CH , scissoring vibration dCH
region 2945 ± 45, 2885 ± 45 and 1445 ± 35 cm
2
group, the asymmetric stretch
t
asCH
2
,
Raman spectrum were assigned as
t
PhI. Also SDD calculations give
ꢂ1
t
s
2
2
, appear in the
these modes at 1609, 1569, 1455, 1420, 1286 cm , which are in
agreement with literature [56]. In ortho substitution the ring
breathing mode has three frequency intervals according to
whether both substituents are heavy, or one of them is heavy while
the other is light, or both of them are light. In the first case the
ꢂ1
,
respectively
ꢂ1
[
56,63]. The SDD calculations give
t
asCH
2
at 2978 cm and
t
s
CH
2
ꢂ1
ꢂ1
at 2925 cm . The bands observed at 2968, 2912 cm (IR) and
2
ꢂ1
981, 2935 cm (Raman) are assigned as asymmetric and sym-
ꢂ1
metric CH
2
modes, respectively. In the present case, the band ob-
interval is 1100–1130, in the second case 1020–1070 cm , while
ꢂ1
ꢂ1
served at 1493 cm
in the IR, 1480 in Raman spectrum and
. Bands
twisting and wagging vibrations are
in the third case it is between 630 and 780 cm [73]. The bands
ꢂ1
ꢂ1
ꢂ1
1
469 cm (SDD) are assigned as the scissoring mode of CH
2
observed at 1077 cm in the IR spectrum, 1084 cm in the Ra-
ꢂ1
of hydrocarbons due to CH
observed in the region 1180–1390 cm [51,63]. The CH
2
man spectrum and at 1068 cm (SDD) is assigned as the ring
ꢂ1
2
wagging
breathing mode for PhI ring in the present case.
ꢂ1
and twisting modes are assigned at 1384 and 1205 cm (SDD),
The CH in-plane bending for the phenyl rings are expected
ꢂ1
ꢂ1
ꢂ1
1
216 cm (IR), 1370, 1219 cm (Raman) respectively. The band
above 1000 cm [56] and bands observed at 1077, 1107, 1249
ꢂ1
calculated at 960 cm is assigned as the rocking mode of CH
2
.
(IR), 1084, 1109, 1120, 1242 (Raman) and 1020, 1077, 1152,
1169, 1292 (IR), 1026, 1084, 1154, 1301 cm (Raman) are as-
ꢂ1
The existence of one or more aromatic rings in a structure is
normally readily determined from the CAH and C@CAC ring re-
lated vibrations. The CAH stretching occurs above 3000 cm and
is typically exhibited as a multiplicity of weak to moderate bands,
signed as in-plane CH modes for the rings PhI and PhII, respec-
tively. The corresponding calculated values (SDD) are 1068, 1095,
1145, 1241 for PhI and 1012, 1068, 1155, 1167, 1303 cm for PhII
ꢂ1
ꢂ1
compared with the aliphatic CAH stretch [66]. In the present case,
rings. The CH out-of-plane deformations [74] are observed be-
tween 1000 and 700 cm . Generally, the CAH out-of-plane defor-
mations with the highest wavenumbers have a weaker intensity
ꢂ1
the SDD calculations give
t
CAH modes in the range of 3071–
ꢂ1
ꢂ1
3
116 cm . The bands observed at 3056, 3094, 3174 cm in the

1
8
Y.S. Mary et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 12–24
Table 2
Second-order perturbation theory analysis of Fock matrix in NBO basis corresponding to the intra molecular bonds of the title compound.
E(2)a
E(j) ꢂ E(i)
b
F(i,j)c
Donor (i)
Type
ED/e
Acceptor (j)
Type
ED/e
ꢁ
C1AC2
–
r
–
1.98
–
C1AC6
C2AC3
r
0.02
0.02
0.03
0.48
0.31
0.01
0.01
0.01
0.01
0.02
0.01
0.01
0.01
0.04
0.03
0.02
0.04
0.02
0.01
0.02
0.01
0.02
0.33
0.31
0.35
0.02
0.02
0.03
0.04
0.02
0.01
0.01
0.02
0.02
0.03
0.02
0.02
0.02
0.33
0.48
0.02
0.04
0.01
0.02
0.02
0.02
0.48
0.02
0.01
0.02
0.03
0.35
0.05
0.35
0.05
0.01
0.02
0.02
0.02
0.01
0.01
0.32
0.33
0.01
0.03
0.01
0.01
0.01
0.03
0.03
0.02
0.01
0.02
0.02
2.50
3.39
6.89
20.10
17.50
2.63
2.40
2.62
2.35
3.69
3.52
2.61
2.12
4.68
2.48
3.44
4.06
4.63
2.45
3.84
2.24
4.14
18.87
18.87
14.21
2.35
2.48
3.91
3.71
2.35
2.59
2.25
2.48
2.30
1.09
2.53
3.01
5.44
20.44
18.88
3.62
4.18
3.63
3.60
4.81
2.16
17.07
4.76
2.33
2.48
2.19
3.67
2.19
3.66
2.19
2.91
2.27
4.44
2.81
1.56
1.86
17.44
20.96
2.69
4.24
2.22
2.55
2.15
3.24
5.04
2.68
2.21
3.80
3.33
1.25
1.26
1.11
0.27
0.29
1.25
1.14
1.26
1.16
1.09
1.10
1.29
1.19
1.24
1.13
1.09
1.06
1.25
1.14
1.26
1.15
1.13
0.28
0.29
0.25
1.37
1.39
1.21
1.22
1.13
1.28
1.17
1.32
1.34
1.16
1.24
1.27
1.12
0.27
0.26
1.07
1.04
1.09
1.10
1.43
1.30
0.33
1.39
1.23
1.12
0.97
0.54
0.96
0.54
0.96
1.34
1.36
1.28
1.29
1.18
1.18
0.29
0.29
0.93
1.26
1.17
1.28
1.18
1.25
0.99
1.27
1.17
1.09
1.11
0.05
0.06
0.08
0.07
0.06
0.05
0.05
0.05
0.05
0.06
0.06
0.05
0.05
0.07
0.05
0.06
0.06
0.07
0.05
0.06
0.05
0.06
0.07
0.07
0.05
0.05
0.05
0.06
0.06
0.05
0.05
0.05
0.05
0.05
0.08
0.05
0.06
0.07
0.07
0.07
0.06
0.06
0.06
0.06
0.07
0.05
0.07
0.07
0.05
0.05
0.04
0.04
0.04
0.04
0.04
0.06
0.05
0.07
0.06
0.04
0.04
0.06
0.07
0.05
0.07
0.05
0.05
0.05
0.06
0.06
0.05
0.05
0.06
0.05
–
–
–
p
–
r
–
–
–
r
–
r
–
–
–
r
–
r
–
–
–
–
p
–
–
r
–
–
r
–
–
–
r
–
–
r
–
–
p
–
r
–
r
–
–
1.73
–
1.98
–
–
–
1.98
–
1.98
–
–
–
1.98
–
1.97
–
–
–
–
1.60
–
–
1.98
–
–
1.98
–
–
–
1.98
–
–
1.98
–
–
1.71
–
1.98
–
1.98
–
C3AN11
C3AC4
C5AC6
C1AC2
C2AH7
C5AC6
C5AH8
C2AC3
C5AC6
C1AC2
C1AH29
C3AC4
C3AN11
C1AC6
C3AC4
C2AC3
C2AH7
C4AC5
C5AH8
N11AH27
C1AC2
C5AC6
N10AC12
C2AC3
C4AC5
C12AC13
C3AC4
C4AN10
C5AC6
C6AH9
C2AC3
C4AC5
C12AC13
C1AC6
C4AC5
C4AN10
C1AC2
C3AC4
C1AC6
C3AC4
C1AC2
–
p
–
r
–
–
–
r
–
ꢁ
C1AC2
–
C1AC6
–
–
–
C1AH29
–
C2AC3
–
–
–
C2AH7
–
C3AC4
–
–
–
–
C3AC4
–
–
C3AN11
–
–
C4AC5
–
–
–
C4AN10
–
–
C5AC6
–
–
C5AC6
–
C5AH8
–
C6AH9
–
N10AC12
–
N10AC12
N11AC12
N11AH27
C12AC13
ꢁ
ꢁ
ꢁ
r
–
–
–
r
–
ꢁ
ꢁ
r
–
–
–
–
p
–
–
r
–
–
ꢁ
ꢁ
ꢁ
r
–
–
–
r
–
–
r
–
–
p
–
r
–
r
–
r
–
r
p
r
r
–
r
–
p
–
r
–
p
–
–
–
r
–
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
C4AC5
C4AC5
N11AH27
C3AC4
C2AC3
ꢁ
r
–
1.98
–
ꢁ
r
p
r
r
–
r
–
p
–
r
–
p
–
–
–
r
–
r
–
–
–
–
r
–
–
–
1.88
1.99
1.99
1.98
–
1.98
–
1.98
–
1.99
–
1.98
–
–
–
1.68
–
1.97
–
–
–
–
1.97
–
–
–
ꢁ
ꢁ
N10AC12
C4AN10
C16AO26
N10AC12
N11AC12
N10AC12
N11AC12
N10AC12
C16AC18
C16AC18
C17AC19
C17AH20
C18AH22
C18AC21
C19AC23
C13AO26
C16AC17
C17AH20
C18AC21
C21AH25
C16AC17
C16AO26
C19AC23
C23AH28
C16AC18
C19AC23
ꢁ
–
ꢁ
C13AH14
–
C13AH15
–
C13AO26
–
C16AC17
–
ꢁ
ꢁ
ꢁ
–
–
ꢁ
C16AC17
–
C16AC18
–
–
–
–
C17AC19
–
–
–
C17AH20
–
ꢁ
r
–
–
–
–
ꢁ
r
–
–
–
r
–
ꢁ
r
–
1.98
–

Y.S. Mary et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 12–24
19
Table 2 (continued)
Donor (i)
b
F(i,j)c
Type
ED/e
Acceptor (j)
Type
ED/e
E(2)a
E(j) ꢂ E(i)
ꢁ
C18AC21
–
–
–
C18AC19
–
C18AH22
–
C19AC23
–
–
–
C19AC23
–
C19AH24
C21AC23
r
–
–
–
p
–
r
–
r
–
–
–
p
–
r
r
–
–
–
r
–
r
–
n
–
n
–
n
n
–
–
1.98
–
–
–
1.70
–
1.98
–
1.98
–
–
–
1.68
–
1.98
1.98
–
–
–
1.98
–
1.98
–
C16AC18
C16AO26
C21AC23
C23AH28
C16AC17
C19AC23
C16AC17
C21AC23
C17AC19
C17AH20
C21AC23
C21AH25
C16AC17
C18AC21
C16AC17
C18AC21
C18AH22
C19AC23
C19AH24
C16AC18
C19AC23
C17AC19
C18AC21
C3AC4
r
0.02
0.03
0.02
0.01
0.39
0.33
0.03
0.02
0.02
0.01
0.02
0.01
0.39
0.32
0.03
0.01
0.01
0.02
0.01
0.02
0.02
0.02
0.01
0.04
0.05
0.48
0.35
0.03
0.02
0.02
0.39
2.75
3.95
2.66
2.19
22.37
17.98
4.10
4.43
2.71
2.24
2.61
2.28
18.45
21.88
3.80
2.70
2.41
2.62
2.36
3.77
3.41
3.66
3.46
5.82
10.11
33.25
50.13
2.76
4.55
4.55
26.25
1.26
0.99
1.26
1.17
0.26
0.28
1.08
1.09
1.26
1.16
1.26
1.16
0.26
0.27
1.08
1.27
1.16
1.26
1.16
1.08
1.10
1.09
1.10
0.87
0.76
0.29
0.27
1.45
0.74
0.74
0.33
0.05
0.06
0.05
0.05
0.07
0.06
0.06
0.06
0.05
0.05
0.05
0.05
0.06
0.07
0.06
0.05
0.05
0.05
0.05
0.06
0.06
0.06
0.06
0.06
0.08
0.09
0.11
0.06
0.05
0.05
0.09
–
–
–
ꢁ
p
–
r
ꢁ
–
r
ꢁ
–
–
–
ꢁ
p
–
r
r
ꢁ
ꢁ
–
–
–
–
–
–
ꢁ
C21AH25
–
C23AH28
–
LP(1)N10
–
LP(1)N11
–
LP(1)O26
LP(2)O26
–
–
r
–
r
ꢁ
–
r
ꢁ
1.93
–
1.61
–
1.96
1.87
–
N11AC12
C3AC4
–
p
ꢁ
N10AC12
C16AC17
C13AH14
C13AH15
C16AC17
–
r
r
ꢁ
ꢁ
–
p
ꢁ
–
a
E(2) means energy of hyperconjugative interactions (stabilization energy).
Energy difference between donor and acceptor i and j NBO orbitals.
F(i,j) is the Fock matrix element between i and j NBO orbitals.
b
c
than those at lower wavenumbers. The out-of-plane CH deforma-
structure of 2-(phenoxymethyl)benzoimidazole was determined
by using Gaussian09 program. The optimized geometry is summa-
rized in Table S1. From Table S1, it is clearly seen that the dihedral
ꢂ1
tion at 769 cm
and the out-of-plane ring deformation at
ꢂ1
6
87 cm in the IR spectrum form a pair of strong bands character-
istics of mono-substituted benzene derivative [56,75]. In the pres-
angles C
6 5 4 4 1 2 3
AC AC AN10 and C AN10AC12AC13, C AC AC AN11, C2-
ꢂ1
ent case bands at 902, 814, 769 cm
in the IR, at 902, 830,
AC AN11AC12 are 180°. This indicates that the benzene ring I
3
ꢂ1
ꢂ1
7
59 cm in Raman and at 991, 968, 898, 825, 758 cm by SDD
and the benzimidazole ring moieties of the title compound are pla-
nar as in the case of 2-amino-6-methylbenzothiazole [76]. For 2-
are assigned as CH out-of-plane deformations for PhII ring. In the
case of 1,2-disubstituted benzenes, a strong absorption in the re-
amino-6-methylbenzothiazole [76] the bond lengths
4 5
C AC ,
ꢂ1
gion 755 ± 35 cm is observed and is due to
c
CH, which is as-
C
4
AC , C AC , C AN10, are respectively, 1.4145, 1.4333, 1.4066,
3
3
2
4
ꢂ1
signed at 749 cm
in the IR spectrum [66]. For the title
1.4110 Å. The corresponding values for the title compound are
1.4076, 1.4311, 1.405, 1.4127 Å. The SDD calculations give the
bond angles C AC AN10, C AN10AC12, C AN11AC12, N10AC12AN11
3 4 4 3
ꢂ1
ꢂ1
compound modes obtained at 982, 944, 862, 757 cm by theory
ꢂ1
(
SDD) with 921, 841, 749 cm in IR and 864, 749 cm in Raman
spectra are assigned as the CH out-of-plane deformations for PhI
ring. The substituent sensitive modes of the rings are also identi-
fied and assigned (Table 1).
as 109.9, 105.0, 107.3 and 113.1° for the title compound. These val-
ues are in agreement with the bond angles reported for 2-amino-6-
methylbenzothiazole [76] and for 2-amino-4-ethylbenzothiazole
[
C
77]. For 2- amino-4-methylbenzothiazole [77] the bond lengths
AC , C12AN10, C AN10 are 1.3916, 1.2962, 1.4173 Å, respectively.
Purkayastha and Chattopadhyay [78] reported N10AC12, N10AC
Optimized geometry
3
4
4
4
A detailed potential energy surface (PES) scan on dihedral an-
gles N10AC12AC13AO26, C12AC13AO26AC16 have been performed
at B3LYP/6-31G(d) level to reveal all possible conformations of 2-
bond lengths as 1.3270, 1.400 Å for benzothiazole and 1.3503,
1.407 Å for benzimidazole compounds. For the title compound
we have obtained these values are 1.3305 and 1.4127 Å. The car-
bon–carbon bond lengths in the phenyl ring PhI lie between
1.4041 and 1.4311 Å while for phenyl ring PhII, the range is
1.4033–1.4113 Å. The CH bond length lies between 1.0859 and
1.0874 Å for PhI and 1.0852–1.0873 Å for PhII. These changes in
bond lengths for the title compound can be attributed to the con-
jugation of the phenyl ring. Here for the title compound, benzene is
a regular hexagon with bond lengths somewhere in between the
normal values for a single (1.54 Å) and a double (1.33 Å) bond [79].
For the title compound, the bonds C12AN10 = 1.3305 show typ-
(
phenoxymethyl)benzimidazole. The PES scan was carried out by
minimizing the potential energy in all geometrical parameters by
changing the torsion angle at every 10° for 180° rotation around
the bond. The results obtained in PES scan study by varying the tor-
2
sion perturbation around the CH bonds are plotted in Figs. S1 and
S2 (Supporting information). For the N10AC12AC13AO26 rotation,
the minimum energy was obtained at ꢂ180.0° in the potential en-
ergy curve of energy ꢂ725.44703 Hartrees. For the C12AC13AO26-
AC16 rotation, the minimum energy occurs at 180.0° in the
potential energy curve of energy ꢂ725.4470.
ical double bond characteristics. However, C
AN11 = 1.3992 Å, C12AN11 = 1.3881 Å bond length are shorter
than the normal CAN single bond length of about 1.48 Å. The
4
AN10 = 1.4127 Å,
To the best of our knowledge, no X-ray crystallographic data of
this molecule has yet been established. The optimized molecular
C
3

2
0
Y.S. Mary et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 12–24
shortening of the CAN bonds reveal the effects of resonance in this
part of the molecule [80] and this situation can be attributed to the
difference in hybridization of the different carbon atoms.
q
E
i
? donor orbital occupancy;
, E ? diagonal elements;
i
j
F
ij ? the off diagonal NBO Fock matrix element.
Lifshitz et al. [81] reported the bond lengths for N10AC12, C
3 2
AC ,
C
1
1
4
AC , C AC , and N10AC as 1.291, 1.374, 1.39, 1.4, 1.403 and
.401 Å. The corresponding values in the present case are 1.3305,
.405, 1.4076, 1.4311, 1.4127 Å. Corresponding values are reported
5
3
4
4
In NBO analysis large E(2) value shows the intensive interaction
between electron-donors and electron-acceptors and greater the
extent of conjugation of the whole system, the possible intensive
interactions are given in Table 2. The second-order perturbation
theory analysis of Fock matrix in NBO basis shows strong intra
as 1.2753, 1.3492, 1.359, 1.3768, 1.3879, 1.3784, 1.3892 Å [82] and
.2727, 1.347, 1.3594, 1.3884, 1.3777, 1.3776, 1.3903 Å [49]. The
bond lengths C AN10, N10AC12 and C AC are found to be 1.3436,
.3804 and 1.3827 Å for mercaptobenzoxazole [65]. For the title
1
4
3
4
molecular hyper conjugative interactions of p electrons. The intra
1
molecular hyper conjugative interactions are formed by the orbital
ꢁ
compound these values are respectively 1.4127, 1.3305, 1.4311 Å.
overlap between n(O) and
p
(CAC) bond orbital which results in ICT
causing stabilization of the system. The strong intra molecular
First hyperplarizability
hyper conjugative interaction of C16AC17 from of n
2
(O26) ?
ꢁ
p
(C16AC17) which increases ED (0.39e) that weakens the respective
ꢂ1
Nonlinear optics deals with the interaction of applied electro-
magnetic fields in various materials to generate new electromag-
netic fields, altered in wavenumber, phase, or other physical
properties [83]. Organic molecules able to manipulate photonic sig-
nals efficiently are of importance in technologies such as optical
communication, optical computing, and dynamic image processing
bonds leading to stabilization of 26.25 kcal mol . Also another
intra molecular hyper conjugative interactions are formed by the
ꢁ
orbital overlap between n(N) and
p
(NAC) bond orbital which
results in ICT causing stabilization of the system. The strong intra
molecular hyper conjugative interaction of N10AC12 from of
ꢁ
1
n (N11) ?
p
(N10AC12) which increases ED (0.35e) that weakens
ꢂ1
[
84,85]. In this context, the dynamic first hyperpolarizability of the
the respective bonds leading to stabilization of 50.13 kcal mol
.
title compound is also calculated in the present study. First hyper-
polarizability is a third rank tensor that can be described by a
These interactions are observed as an increase in electron density
(ED) in CAC, NAC anti-bonding orbital that weakens the respective
bonds.
The increased electron density at the oxygen atoms leads to the
elongation of respective bond length and a lowering of the corre-
3
ꢃ 3 ꢃ 3 matrix. The 27 components of the 3D matrix can be re-
duced to 10 components due to the Kleinman symmetry [86]. The
components of beta are defined as the coefficients in the Taylor ser-
ies expansion of the energy in the external electric field. When the
electric field is weak and homogeneous, this expansion becomes
sponding stretching wavenumber. The electron density (ED) is
ꢁ
transferred from the n(O), n(N) to the anti-bonding
p
orbital of
the CAC, NAC explaining both the elongation and the red shift.
X
X
X
X
1
2
1
6
1
24
i
i
j
i
j
k
i j k l
E¼E
0
ꢂ
liF ꢂ
a
ijF F ꢂ
b F F F ꢂ
cijklF F F F þꢄꢄꢄ
The ACH O stretching modes can be used as a good probe for eval-
ijk
2
i
ij
ijk
ijkl
uating the bonding configuration around the corresponding atoms
and the electronic distribution of the benzene molecule. Hence the
i
where E
0
is the energy of the unperturbed molecule, F is the field at
2
-(phenoxymethyl)benzimidazole structure is stabilized by these
orbital interactions. The NBO analysis also describes the bonding
in terms of the natural hybrid orbital n (O26), which occupy a high-
er energy orbital (ꢂ0.32017 a.u.) with considerable p-character
100.00%) and low occupation number (1.86649 a.u.) and the other
(O26) occupy a lower energy orbital (ꢂ0.56367) with p-character
58.92%) and high occupation number (1.96434 a.u.). Also n (N11),
the origin,
i
l , aij, bijk and cijkl are the components of dipole moment,
polarizability, the first hyper polarizabilities, and second hyperpo-
larizibilities, respectively. The calculated first hyperpolarizability
2
ꢂ30
of the title compound is 2.34 ꢃ 10
esu, which comparable with
(
n
(
the reported values of similar derivatives [87] and which is 18.00
1
ꢂ30
times that of the standard NLO material urea (0.13 ꢃ 10
esu)
1
[
88]. We conclude that the title compound is an attractive object
which occupy a higher energy orbital (ꢂ0.26494 a.u.) with consid-
for future studies of nonlinear optical properties.
erable p-character (100.00%) and low occupation number
(
(
(
1
1.61117 a.u.) and the other n (N10) occupy a lower energy orbital
NBO analysis
ꢂ0.34026) with p-character (66.51%) and high occupation number
1.92659 a.u.). Thus, a very close to pure p-type lone pair orbital
The natural bond orbital (NBO) calculations were performed
using NBO 3.1 program [89] as implemented in the Gaussian09
package at the DFT/B3LYP level in order to understand various sec-
ond-order interactions between the filled orbital of one subsystem
and vacant orbital of another subsystem, which is a measure of the
inter molecular delocalization or hyper conjugation. NBO analysis
provides the most accurate possible ‘natural Lewis structure’ pic-
ture of ‘j’ because all orbital details are mathematically chosen to
include the highest possible percentage of the electron density. A
useful aspect of the NBO method is that it gives information about
interactions of both filled and virtual orbital spaces that could en-
hance the analysis of intra and inter molecular interactions.
The second-order Fock-matrix was carried out to evaluate the
donor–acceptor interactions in the NBO basis. The interactions re-
sult in a loss of occupancy from the localized NBO of the idealized
Lewis structure into an empty non-Lewis orbital. For each donor (i)
and acceptor (j) the stabilization energy (E2) associated with the
delocalization i ? j is determined as
ꢁ
participates in the electron donation to the
n
n
r
(CAC) orbital for
ꢁ
ꢁ
ꢁ
ꢁ
2
(O26) ?
(N10) ?
r
r
(CAC) and
r
(NAC) orbital for n
1
(N11) ?
r
(NAC),
1
(NAC) interactions in the compound. The results are
tabulated in Table 3.
Mulliken charges and Molecular Electrostatic Potential
The calculation of atomic charges plays an important role in the
application of quantum mechanical calculations to molecular sys-
tems. Mulliken charges are calculated by determining the electron
population of each atom as defined in the basis functions. The
charge distributions calculated by the Mulliken [90] and NBO
methods for the equilibrium geometry of 2-(phenoxymethyl)benz-
imidazole are given in Table S2 (Supporting material). The charge
distribution on the molecule has an important influence on the
vibrational spectra. In 2-(phenoxymethyl)benzimidazole, the
Mulliken atomic charge of the carbon atoms in the neighborhood
3 4
of C , C , C12, C16 become more positive, shows the direction of
delocalization and shows that the natural atomic charges are more
sensitive to the changes in the molecular structure than Mulliken’s
net charges. The results are represented in Fig. S3 (Supporting
2
ðFi;j
Þ
Eð2Þ ¼
D
Eij ¼ qi
ðE
j
ꢂ E
i
Þ

Y.S. Mary et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 12–24
21
Table 3
NBO results showing the formation of Lewis and non-Lewis orbitals.
Bond(AAB)
ED/energy
EDA%
EDB%
NBO
0.7024(sp1 )C
s%
p%
64.80
.84
.82
r
C1AC2
1.97573
ꢂ0.68572
1.72789
49.34
–
48.98
–
50.14
–
48.46
–
51.03
–
49.88
–
38.42
–
51.13
–
42.07
–
50.28
–
48.75
–
57.93
–
58.61
–
62.20
–
50.06
–
32.19
–
50.26
–
47.53
–
50.67
–
32.16
–
50.64
–
50.34
–
51.69
–
50.20
–
50.66
–
51.02
–
49.86
–
51.54
–
48.97
–
50.12
–
61.58
–
48.87
–
57.93
–
49.72
–
51.25
–
42.07
–
41.39
–
37.8
–
49.94
–
67.81
–
49.74
–
52.47
–
49.33
–
67.84
–
49.36
–
49.66
–
48.31
–
49.80
–
35.20
35.75
0.00
1
–
+0.7118 (sp )C
64.25
100.0
100.0
64.81
65.16
66.20
60.04
67.07
67.55
100.0
100.0
73.05
65.12
61.36
65.87
71.33
68.89
64.53
64.57
100.0
100.0
64.59
65.93
100.0
100.0
66.32
70.34
63.75
70.85
81.05
73.32
61.38
66.03
100.0
100.0
62.45
66.08
76.34
67.77
64.20
65.25
64.13
64.98
100.0
100.0
64.46
64.99
100.0
100.0
64.78
65.23
66.51
–
0.6999(sp1 )C
.00
pC1AC2
1.00
–
ꢂ0.24455
+0.7143(sp )C
0.7081(sp1 )C
0.00
.84
r
–
r
–
r
–
C1AC6
C2AC3
C3AC4
1.98049
35.19
34.84
33.80
39.96
32.93
32.45
0.00
1
.87
ꢂ0.67402
1.97583
+0.7061(sp )C
0.6961(sp1 )C
.96
1
.50
ꢂ0.70631
+0.7179(sp )C
0.7143(sp2 )C
.04
1.96899
2
.08
ꢂ0.67221
1.60257
+0.6998(sp )C
0.7062(sp1 )C
.00
pC3AC4
1.00
–
ꢂ0.24485
+0.7080(sp )C
0.6199(sp2 )C
0.00
.71
r
–
r
–
C3AN11
C4AC5
1.98380
26.95
34.88
38.64
34.13
28.67
31.11
35.47
35.43
0.00
1
.87
ꢂ0.79917
1.96660
+0.7847(sp )N
0.7150(sp1 )C
.59
1
.93
ꢂ0.69048
+0.6991(sp )C
0.6486(sp2 )C
.49
r
–
r
–
C4AN10
C5AC6
1.97651
2
.21
ꢂ0.74842
1.97755
+0.7611(sp )N
0.7091(sp1 )C
.82
1.82
ꢂ0.68230
+0.7051(sp )C
0.6982(sp1 )C
.00
pC5AC6
1.71464
1
.00
–
ꢂ0.23830
1.98424
+0.7159(sp )C
0.00
0.7611(sp1 )N
.82
35.41
34.07
0.00
r
N10AC12
1
.93
–
ꢂ0.84684
+0.6486(sp )C
0.7656(sp1 )N
.00
pN10AC12
1.88015
1
.00
–
ꢂ0.30334
1.98725
+0.6433(sp )C
0.00
0.7887(sp1 )N
.97
33.68
29.66
36.25
29.15
18.95
26.68
38.62
33.97
0.00
r
–
r
–
r
–
r
–
N11AC12
C12AC13
C13AO26
C16AC17
2
.37
ꢂ0.81353
+0.6148(sp )C
0.7076(sp1 )C
.76
1.97985
2
.43
ꢂ0.68000
1.98962
+0.7066(sp )C
0.5673(sp4 )C
.28
2
.75
ꢂ0.80877
+0.8235(sp )O
0.7090(sp1 )C
.59
1.97971
1
.94
ꢂ0.72021
1.67651
+0.7053(sp )C
0.6894(sp1 )C
.00
pC16AC17
1
.00
–
ꢂ0.26698
+0.7244(sp )C
0.7118(sp1 )C
0.00
.66
r
–
r
–
r
–
r
–
C16AC18
C16AO26
C17AC19
C18AC21
1.97428
37.55
33.92
23.66
32.23
35.80
34.75
35.87
35.02
0.00
1
.95
ꢂ0.70950
1.99132
+0.7024(sp )C
0.5671(sp3 )C
.23
2
.10
ꢂ0.88792
+0.8237(sp )O
0.7116(sp1 )C
.79
1.97455
1
.88
ꢂ0.69612
1.97626
+0.7026(sp )C
0.7095(sp1 )C
.779
1.86
ꢂ0.69965
+0.7047(sp )C
0.7190(sp1 )C
.00
pC18AC21
1.69757
1
.00
–
ꢂ0.25426
1.98067
+0.6951(sp )C
0.00
0.7085(sp1 )C
.81
35.54
35.01
0.00
r
C19AC23
1.86
–
ꢂ0.69617
+0.7057(sp )C
0.6972(sp1 )C
.00
pC19AC23
1.68202
48.61
–
50.17
51.39
–
49.83
1
.00
–
ꢂ0.25090
1.98036
+0.7169(sp )C
0.00
0.7083(sp1 )C
.84
35.22
34.77
33.49
–
0.00
–
41.08
–
0.00
r
C21AC23
1
.88
–
ꢂ0.69173
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
+0.7059(sp )C
1
1
1
1
.99
.00
.43
.00
n1N10
–
n1N11
–
n1O26
–
n2O26
–
1.92659
sp
–
sp
–
sp
–
sp
–
ꢂ0.34026
1.61117
100.0
–
58.92
–
100.0
–
ꢂ0.26494
1.96434
ꢂ0.56367
1.86649
ꢂ0.32017
–
material). Also we done a comparison of Mulliken charges obtained
by different basic sets and tabulated it in Table S3 (Supporting
material) in order to assess the sensitivity of the calculated charges
to changes in (i) the choice of the basis set; (ii) the choice of the
quantum mechanical method. The results can, however, better be
represented in graphical form as shown in Fig. S4 (Supporting
material). We have observed a change in the charge distribution
by changing different basis sets.
‘‘recognition’’ of one molecule by another, as in drug-receptor,
and enzyme-substrate interactions, because it is through their
potentials that the two species first ‘‘see’’ each other [93,94]. To
predict reactive sites of electrophilic and nucleophilic attacks for
the investigated molecule, MEP at the B3LYP/6-31G(d,p) optimized
geometry was calculated. The negative (red and yellow1) regions of
MEP were related to electrophilic reactivity and the positive (blue)
regions to nucleophilic reactivity (Fig. 4). From the MEP it is evident
MEP is related to the ED and is a very useful descriptor in under-
standing sites for electrophilic and nucleophilic reactions as well as
hydrogen bonding interactions [91,92]. The electrostatic potential
V(r) is also well suited for analyzing processes based on the
1
For interpretation of color in Fig. 4, the reader is referred to the web version of
this article.

2
2
Y.S. Mary et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 12–24
tion spectrum in vacuum was performed. TD-DFT calculation is
capable of describing the spectral features of 2-(phenoxy-
methyl)benzimidazole because of the qualitative agreement of line
shape and relative strength as compared with experiment. The
absorption spectra of organic compounds stem from the ground-
to-excited state vibrational transition of electrons. The intense
band in the UV range of the electronic absorption spectrum is ob-
served at 280 nm, which is indicating the presence of AOPh entity
in the compound. The calculated six lowest-energy transitions of
the molecule from TD-DFT method and the observed electronic
transitions are listed in Table 5. From the table the calculated
energy transitions are red shifted from the experimental value,
because these bands are observed in gas phase without considering
the solvent effect.
Fig. 4. Molecular Electrostatic Potential calculated at B3LYP/SDD level.
HOMO and LUMO are the very important parameters for quan-
tum chemistry. The conjugated molecules are characterized by a
highest occupied molecular orbital–lowest unoccupied molecular
orbital (HOMO–LUMO) separation, which is the result of a signifi-
cant degree of ICT from the end-capping electron-donor groups to
Table 4
Experimental and calculated 1H NMR parameters (with respect to TMS).
Proton
r
TMS
r
calc.
d(r
TMS
ꢂ
r
calc.
)
Exp. dppm
H7
H8
H9
32.7711
25.0344
25.0101
25.2600
27.3373
27.3370
25.8637
25.4320
25.1317
25.1421
23.3079
25.4570
25.2517
7.7367
7.761
7.661
7.602
7.517
5.316
5.313
6.955
7.339
7.552
7.550
9.512
7.317
7.552
the efficient electron-acceptor groups through
The strong charge transfer interaction through p
bridge results in substantial ground state donor–acceptor mixing
and the appearance of a charge transfer band in the electronic
absorption spectrum. Therefore, an ED transfer occurs from the
p
-conjugated path.
-conjugated
–
–
–
–
–
–
–
–
–
–
–
7.5111
5.4338
5.4341
6.9074
7.3391
7.6394
7.629
9.4632
7.3141
7.5194
H14
H15
H20
H22
H24
H25
H27
H28
H29
Table 5
Calculated electronic absorption spectrum of using TD-DFT/B3LYP/SDD.
Excitation
CI expansion
Energy
coefficient
Wavelength
(nm)
Oscillator
strength (f)
(
eV)
Calculated
Expt.
Excited State 1
that the negative charge covers the ACH
region is over the methoxyl group. The more electro negativity
methoxy makes it the most reactive part in the molecule.
2
OA group and the positive
58 ? 60
0.52516
0.19018
0.11162
0.19449
ꢂ0.34041
5.0052
247.71
280
–
–
–
–
0.1053
58 ? 61
58 ? 63
59 ? 60
59 ? 63
–
–
–
–
–
–
–
–
–
–
–
–
1
H NMR spectrum
Excited State 2
56 ? 62
57 ? 60
57 ? 61
58 ? 60
0.16412
0.19818
ꢂ0.14689
ꢂ0.19048
0.13579
0.54882
ꢂ0.11583
5.04521
245.75
275
–
–
–
–
0.0559
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
The experimental spectrum data of 2-(phenoxymethyl)benz-
imidazole in DMSO with TMS as internal standard is obtained at
4
00 MHz and is displayed in Table 4. The absolute isotropic chem-
58 ? 63
59 ? 60
ical shielding of 2-(phenoxymethyl)benzimidazole was calculated
by B3LYP/GIAO model [95]. Relative chemical shifts were then
–
–
59 ? 61
estimated by using the corresponding TMS shielding:
calculated in advance at the same theoretical level as this article.
Numerical values of chemical shift
together with calculated values of calc.(TMS), are reported in
r
calc.(TMS)
Excited State 3
56 ? 62
57 ? 60
57 ? 61
58 ? 61
0.28405
0.34847
5.0824
243.95
271
–
–
–
–
0.0665
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
d
calc.
=
r
calc.(TMS) ꢂ
r
calc.
ꢂ0.33750
r
0.17621
Table 4. It could be seen from Table 4 that chemical shift was in
agreement with the experimental 1H NMR data. Thus, the results
showed that the predicted proton chemical shifts were in good
agreement with the experimental data for 2-(phenoxymethyl)
benzimidazole.
58 ? 63
ꢂ0.10953
ꢂ0.25591
ꢂ0.15964
5
5
9 ? 60
9 ? 61
–
–
Excited State 4
57 ? 60
58 ? 60
58 ? 61
58 ? 63
59 ? 61
0.17195
ꢂ0.13442
0.10425
0.11023
0.62198
5.1337
241.51
260
–
–
–
–
0.0054
–
–
–
–
–
–
–
–
–
–
–
–
Electronic absorption spectra
Excited State 5
Electronic transitions are usually classified according to the
57 ? 60
57 ? 61
58 ? 60
ꢂ0.38773
ꢂ0.13865
ꢂ0.19916
0.51220
5.2076
238.08
235
–
–
0.0022
orbital engaged or to specific parts of the molecule involved. Com-
–
–
–
–
–
–
–
–
–
ꢁ
mon types of electronic transitions in organic compounds are
p–p
,
ꢁ
ꢁ
n–
p
and
p
(acceptor)–
p
(donor). The UV–visible bands in 2-(phen-
58 ? 61
–
oxymethyl)benzimidazole are observed at 280, 275, 271, 260, 235
Excited State 6
ꢁ
and 228 nm. Observed band at 228 nm is due to the
p–p
. The less
56 ? 62
57 ? 60
57 ? 61
58 ? 60
ꢂ0.11042
5.2980
234.02
228
–
–
–
–
0.0261
intense band centered at 271 nm is due to the partly forbidden
0.31655
0.46781
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
ꢁ
n–p
transition from HOMO to LUMO. The more intense band ob-
ꢁ
ꢂ0.17185
served at 280 nm belonged to the dipole-allowed
p–p
transition.
58 ? 61
9 ? 61
0.29847
In order to understand the electronic transitions of 2-(phenoxy-
methyl)benzimidazole, TD-DFT calculation on electronic absorp-
5
ꢂ0.11388
–

Y.S. Mary et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 12–24
23
References
[
[
[
[
[
1] R.L. Lombardy, F.A. Tanious, K. Ramachandran, R.R. Tidwell, W.D. Wilson, J.
Med. Chem. 39 (1996) 1452–1462.
2] M.J. Tebbe, W.A. Spitzer, F. Victor, S.C. Miller, C.C. Lee, T.R. Sattelberg, E.
McKinney, J.C. Tang, J. Med. Chem. 40 (1997) 3937–3946.
3] A.R. Porcari, R.V. Devivar, L.S. Kucera, J.C. Drach, L.B. Townsend, J. Med. Chem.
41 (1998) 1252–1262.
4] T.C. Kuhler, M. Swanson, V. Shcherbuchin, H. Larsson, B. Mellgard, J.E. Sjostrom,
J. Med. Chem. 41 (1998) 1777–1788.
5] I. Tapia, L. Alonso-Cires, P.L. Lopez-Tudanca, R. Mosquera, L. Labeaga, A.
Innerarity, A. Orjales, J. Med. Chem. 42 (1999) 2870–2880.
[
[
6] J.J. Chen, Y. Wie, J.C. Drach, L.C. Townsend, J. Med. Chem. 43 (2000) 2449–2456.
7] A.W. White, R. Almassy, A.H. Calvert, N.J. Curtin, R.J. Griffin, Z. Hostomsky, K.
Maegley, D.R. Newell, S. Srinivasan, B.T. Golding, J. Med. Chem. 43 (2000)
4
084–4097.
8] W. Roth, D. Spangenberg, C. Janzen, A. Westphal, M. Schmitt, Chem. Phys. 248
1999) 17–25.
9] E. Jalviste, A. Treshchalov, Chem. Phys. 172 (1993) 325–338.
[
[
(
[
[
10] B.C. Bishop, E.T.J. Chelton, A.S. Jones, Biochem. Pharmacol. 13 (1964) 751–754.
11] N.S. Habib, R. Soliman, F.A. Ashoura, M. El-Taiebi, Pharmazie 52 (1997) 746–
7
49.
12] I. Oren, O. Temiz, I. Yalcin, E. Sener, A. Akin, N. Altanlar, Eur. J. Pharm. Sci. 7
1998) 153–160.
13] H. Goker, M. Tuncbilek, S. Suzen, C. Kus, N. Altanlar, Arch. Pharm. Pharm. Med.
Chem. 334 (2001) 148–152.
[
[
[
[
[
(
14] H. Goker, C. Kus, D.W. Boykin, S. Yildiz, N. Altanlar, Bioorg. Med. Chem. 10
(
2002) 2589–2596.
15] N.S. Pawar, D.S. Dalal, S.R. Shimpi, P.P. Mahulikar, Eur. J. Pharm. Sci. 21 (2004)
15–118.
16] B.G. Mohammad, M.A. Hussein, A.A. Abdel-Alim, M. Hashem, Arch. Pharm. Res.
9 (2006) 26–33.
Fig. 5. HOMO, LUMO plots of 2-(phenoxymethyl)benzimidazole.
1
more aromatic part of the
p-conjugated system in the electron-
donor side to its electron-withdrawing part. The atomic orbital
components of the frontier molecular orbital are shown in Fig. 5.
The HOMO–LUMO energy gap value is found to be 3.916 eV, which
is responsible for the bioactive property of the compound
2
[17] S.D. Vaidya, B.V.S. Kumar, R.V. Kumar, U.N. Bhise, U.C. Mashelkar, J. Heterocycl.
Chem. 44 (2007) 685–691.
[
[
18] P.N. Preston, Chem. Rev. 74 (1974) 279–314.
19] R. Dubey, S. Abuzar, S. Sharma, R.K. Chatterjee, J.C. Katiyar, J. Med. Chem. 28
(1985) 1748–1750.
2
-(phenoxymethyl)benzimidazole [96].
[
[
20] E.S. Lazer, M.R. Matteo, G.J. Possanza, J. Med. Chem. 30 (1987) 726–729.
21] H. Nakano, T. Inoue, N. Kawasaki, H. Miyataka, H. Matsumoto, T. Taguchi, N.
Inagaki, H. Nagai, T. Satoh, Chem. Pharm. Bull. 47 (1999) 1573–1578.
22] A.H. El-Masry, H.H. Fahmy, S.H.A. Abdelwahed, Molecules 5 (2000) 1429–
Conclusion
The geometry optimizations have been carried out using HF and
DFT levels and are in agreement with the reported values. The nor-
mal modes are assigned by PED calculations. The simultaneous acti-
vation of the phenyl ring stretching modes in IR and Raman spectra
can be interpreted as the evidence of intra molecular charge trans-
fer between the donor and the acceptor group via conjugated ring
path, which is responsible for hyperpolarizability enhancement,
[
1438.
[23] M. Castelli, M. Malagoli, L. Lupo, T.R. Riccomi, C. Casolari, C. Cermelli, A. Zanca,
G. Baggio, Pharm. Toxicol. 88 (2001) 67–74.
[
[
24] D.G. Joshi, H.B. Oza, H.H. Parekh, Ind. J. Heterocycl. Chem. 11 (2001) 145–148.
25] Z. Kazimierczuk, J.A. Upcroft, P. Upcroft, A. Gorska, B. Starosciak, A. Laudy, Acta
Biochim. Polon. 49 (2002) 185–195.
[
[
[
[
26] N.M. Goudgaon, V. Dhondiba, A. Vijayalaxmi, Ind. J. Heterocycl. Chem. 13
(
2004) 271–272.
27] H. Goker, S. Ozden, S. Yildiz, D.W. Boykin, Eur. J. Med. Chem. 40 (2005) 1062–
1069.
28] R.V. Kumar, K.R. Gopal, K.V.S.R.S. Kumar, J. Heterocycl. Chem. 42 (2005) 1405–
1408.
29] K. Starcevic, M. Kralj, K. Ester, I. Sabol, M. Grce, K. Pavelic, G. Karminski-
Zamola, Bioorg. Med. Chem. 15 (2007) 4419–4426.
leading to non-linear optical activity. The NBO analysis confirms
ꢁ
the ICT formed by the orbital overlap between n(O) and
p
(CAC),
ꢁ
n(N) and
p
(NAC). A very close to pure p-type lone pair orbital
ꢁ
participates in the electron donation to the
r
(CAC) orbital for
[30] H. Wenmian, F. Jian, Z. Zhengzhi, Biol. Trace Element Res. 64 (1998) 27–35.
[31] J. Cheng, J. Xie, X. Luo, Bioorg. Med. Chem. Lett. 15 (2005) 267–269.
ꢁ
ꢁ
ꢁ
ꢁ
n
n
2
(O26) ?
(N10) ?
r
r
(CAC) and
r
(NAC) orbital for n
1
(N11) ?
r
(NAC),
[
32] Y. He, J. Yang, B. Wu, L. Risen, E.E. Swayze, Bioorg. Med. Chem. Lett. 14 (2004)
217–1220.
1
(NAC) interaction in the molecule. Overall, the TD-DFT
1
calculations on the molecule provided deep insight into their elec-
tronic structures and properties. GIAO-NMR calculations provided
chemical shift values that were in excellent agreement with exper-
imental data. In addition, the calculated UV–Vis results are all in
good agreement with the experimental data. The lowering of
HOMO–LUMO band gap supports bioactive property of the
molecule. MEP predicts the most reactive part in the molecule.
[33] M.A. Ismail, R. Brun, T. Wenzler, F.A. Tanious, W.D. Wilson, D.W. Boykin,
Bioorg. Med. Chem. 12 (2004) 5405–5413.
[
34] H. Nakano, T. Inoue, N. Kawasaki, H. Miyataka, H. Matsumoto, T. Taguchi, N.
Inagaki, H. Nagai, T. Satoh, Bioorg. Med. Chem. 8 (2000) 373–380.
[35] R. Marquis, J. Sheng, T. Nguyen, J. Baldeck, J. Olsson, Arch. Oral Biol. 51 (2006)
015–1023.
1
[
36] A.T. Mavrova, K.K. Anichina, D.I. Vuchev, J.A. Tsenov, P.S. Denkova, M.S.
Kondeva, M.K. Micheva, Eur. J. Med. Chem. 41 (2006) 1412–1420.
[37] S.O. P odunavac-Kuzmonovic, V.M. Leovac, N.U. Perisic-Janjic, J. Rogan, J. Balaz,
J. Serb, Chem. Soc. 64 (1999) 381–384.
[
38] M. Boiani, M. Gonzalez, Mini Rev. Med. Chem. 5 (2005) 409–424.
[39] I. Yildiz-Oren, I. Yalcin, E. Aki-Sener, N. Ucarturk, Eur. J. Med. Chem. 39 (2004)
91–298.
Acknowledgments
2
[
[
40] F.E. King, R.M. Acheson, J. Chem. Soc. (1949) 1396–1400.
41] I. Yalcin, E. Sener, T. Ozden, S. Ozden, A. Akin, Eur. J. Med. Chem. 25 (1990)
705–708.
S.A. and I.Y. would like to thank the Research Fund of Ankara
University (Grant No. 12B3336002) for the financial support in this
research. The authors are thankful to University of Antwerp for ac-
cess to the university’s CalcUA Supercomputer Cluster.
[
[
42] M.A. Phillips, J. Chem. Soc. (1928) 2393–2399.
43] Gaussian 09, Revision B.01, M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E.
Scuseria, M.A. Robb, J.R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G.A.
Petersson, H. Nakatsuji, M. Caricato, X. Li, H.P. Hratchian, A.F. Izmaylov, J.
Bloino, G. Zheng, J.L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J.
Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J.A.
Montgomery Jr., J.E. Peralta, F. Ogliaro, M. Bearpark, J.J. Heyd, E. Brothers, K.N.
Kudin, V.N. Staroverov, T. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A.
Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J.M. Millam, M.
Klene, J.E. Knox, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E.
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2014.01.068.

2
4
Y.S. Mary et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 125 (2014) 12–24
Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, R.L.
[68] M. Kaur, Y.S. Mary, H.T. Varghese, C.Y. Panicker, H.S. Yathirajan, M.S.
Siddegowda, C. Van Alsenoy, Spectrochim. Acta 98 (2012) 91–99.
[69] V.S. Madhavan, Y.S. Mary, H.T. Varghese, C.Y. Panicker, S. Mathew, C. Van
Alsenoy, J. Vinsova, Spectrochim. Acta 89 (2012) 308–316.
[70] T. Joseph, H.T. Varghese, C.Y. Panicker, T. Thiemann, K. Viswanathan, C. Van
Alsenoy, J. Mol. Struct. 1005 (2011) 17–24.
[71] Y.S. Mary, C.Y. Panicker, H.T. Varghese, K. Raju, T.E. Bolelli, I. Yildiz, C.M.
Granadeiro, H.I.S. Nogueira, J. Mol. Struct. 994 (2011) 223–231.
[72] H.T. Varghese, C.Y. Panicker, V.S. Madhavan, S. Mathew, J. Vinsova, C. Van
Alsenoy, J. Raman Spectrosc. 40 (2009) 1211–1223.
Martin, K. Morokuma, V.G. Zakrzewski, G.A. Voth, P. Salvador, J.J. Dannenberg,
S. Dapprich, A.D. Daniels, O. Farkas, J.B. Foresman, J.V. Ortiz, J. Cioslowski, D.J.
Fox, Gaussian Inc., Wallingford, CT, 2010.
[
44] J.B. Foresman, in: E. Frisch (Ed.), Exploring Chemistry with Electronic Structure
Methods: A Guide to Using Gaussian, Gaussian Inc., Pittsburg, PA, 1996.
45] P.J. Hay, W.R. Wadt, J. Chem. Phys. 82 (1985) 270–283.
46] J.Y. Zhao, Y. Zhang, L.G. Zhu, J. Mol. Struct. Theochem. 671 (2004) 179–187.
47] GaussView, Version 5, R. Dennington, T. Keith, J. Millam, Semichem Inc.,
Shawnee Mission KS, 2009.
[
[
[
[
48] J.M.L. Martin, C. Van Alsenoy, GAR2PED, A Program to Obtain a Potential
Energy Distribution from a Gaussian Archive Record, University of Antwerp,
Belgium, 2007.
49] P.L. Anto, C.Y. Panicker, H.T. Varghese, D. Philip, O. Temiz-Arpaci, B. Tekiner-
Gulbas, I. Yildiz, Spectrochim. Acta 67 (2007) 744–749.
[73] G. Varsanyi, Assignments of Vibrational Spectra of Seven Hundred Benzene
Derivatives, John Wiley and Sons Inc., New York, 1974.
[74] C.Y. Panicker, H.T. Varghese, K.R. Ambujakshan, S. Mathew, S. Ganguli, A.K.
Nanda, C. Van Alsenoy, Y.S. Mary, J. Mol. Struct. 963 (2010) 137–144.
[75] S. Higuchi, H. Tsuyama, S. Tanaka, H. Kamada, Spectrochim. Acta 30 (1974)
463–477.
[76] J. Chowdhury, J. Sarkar, R. De, M. Ghosh, G.B. Talapatra, Chem. Phys. 330 (2006)
172–183.
[77] J. Sarkar, J. Chowdhury, M. Ghosh, R. De, G.B. Talapatra, J. Phys. Chem. 109B
(2005) 22536–22544.
[
[
[
[
50] R. Saxena, L.D. Kandpal, G.N. Mathur, J. Polym. Sci. A: Polym. Chem. 40 (2002)
3
959–3966.
51] R.M. Silverstein, G.C. Bassler, T.C. Morril, Spectrometric Identification of
Organic Compounds, fifth ed., John Wiley and Sons Inc., Singapore, 1991.
52] K. Nakamoto, Infrared and Raman spectrum of Inorganic and Coordination
Compounds, fifth ed., John Wiley and Sons Inc., New York, 1997.
53] T.D. Klots, W.B. Collier, Spectrochim. Acta 51A (1995) 1291–1316.
54] G. Yang, S. Matsuzono, E. Koyama, H. Tokuhisa, K. Hiratani, Macromolecules 34
[78] P. Purkayastha, N. Chattopadhyay, Phys. Chem. Chem. Phys. 2 (2000) 203–210.
[79] P. Sykes, A Guide Book to Mechanism in Organic Chemistry, sixth ed., Pearson
Education, India, 2004.
[
[
(
2001) 6545–6547.
[80] H. Arslan, U. Florke, N. Kulcu, G. Binzet, Spectrochim. Acta 68A (2007) 1347–
1355.
[81] A. Lifshitz, C. Tamburu, A. Suslensky, F. Dubnikova, J. Phys. Chem. A 110 (2006)
4607–4613.
[82] K.R. Ambujakshan, V.S. Madhavan, H.T. Varghese, C.Y. Panicker, O. Temiz-
Arpaci, B. Tekiner-Gulbas, I. Yildiz, Spectrochim. Acta, Part A: Mol. Biomol.
Spectrosc. 69 (2008) 782–788.
[
[
[
55] J.B. Bhagyasree, H.T. Varghese, C.Y. Panicker, J. Samuel, C. Van Alsenoy, K.
Bolelli, I. Yildiz, E. Aki, Spectrochim. Acta 102 (2013) 99–113.
56] N.P.G. Roeges, A Guide to the Complete Interpretation of Infrared Spectra of
Organic Structures, John Wiley and Sons Inc., New York, 1994.
57] G. Socrates, Infrared Characteristic Group Frequencies, John Wiley and Sons,
New York, 1981.
[
[
58] A. Spire, M. Barthes, H. Kallouai, G. De Nunzio, Physics D 137 (2000) 392–396.
59] R. Minitha, Y.S. Mary, H.T. Varghese, C.Y. Panicker, R. Ravindran, K. Raju, V.M.
Nair, J. Mol. Struct. 985 (2011) 316–322.
[83] Y.R. Shen, The Principles of Nonlinear Optics, Wiley, New York, 1984.
[84] P.V. Kolinsky, Opt. Eng. 31 (1992) 1676–1684.
[85] D.F. Eaton, Science 253 (1991) 281–287.
[
[
[
[
[
60] C.Y. Panicker, H.T. Varghese, V.S. Madhavan, S. Mathew, J. Vinsova, C. Van
Alsenoy, Y.S. Mary, Y.S. Mary, J. Raman Spectrosc. 40 (2009) 2176–2186.
61] M.S. Kim, M.K. Kim, C.J. Lee, Y.M. Jung, M.S. Lee, Bull. Korean Chem. Soc. 30
[86] D.A. Kleinman, Phys. Rev. 126 (1962) 1977–1979.
[87] L.N. Kuleshova, M.Y. Antipin, V.N. Khrustalev, D.V. Gusev, G.V. Grintselev-
Knyazev, E.S. Bobrikova, Cryst. Rep. 48 (2003) 594–601.
[88] C. Adant, M. Dupuis, J.L. Bredas, Int. J. Quantum Chem. 56 (1995) 497–507.
[89] NBO Version 3.1, E.D. Glendening, A.E. Reed, J.E .Carpenter, F. Weinhold.
[90] R.S. Mulliken, J. Chem. Phys. 23 (1955) 1833–1840.
[91] E. Scrocco, J. Tomasi, Adv. Quantum Chem. 11 (1978) 115–193.
[92] F.J. Luque, J.M. Lopez, M. Orozco, Theor. Chem. Acc. 103 (2000) 343–345.
[93] P. Politzer, J.S. Murray, in: D.L. Beveridge, R. Lavery (Eds.), Theoretical
Biochemistry and Molecular Biophysics: A Comprehensive Survey, vol. 2,
Protein, Adenine Press, Schenectady, NY, 1991 (Chapter 13).
[94] E. Scrocco, J. Tomasi, Top. Curr. Chem. 42 (1973) 95–170.
[95] K. Wolinski, J.F. Hinton, P. Pulay, J. Am. Chem. Soc. 112 (1990) 8251–8260.
[96] A. Lakshmi, V. Balachandran, J. Mol. Struct. 1033 (2013) 40–50.
(
2009) 2930–2934.
62] K. Malek, A. Puc, G. Schroeder, V.I. Rybachenko, L.M. Proniewich, Chem. Phys.
27 (2006) 439–451.
3
63] N.B. Colthup, L.H. Daly, S.E. Wiberly, Introduction to Infrared and Raman
Spectroscopy, second ed., Academic Press, New York, 1975.
64] N. Sandhyarani, G. Skanth, S. Berchmanns, V. Yegnaraman, T. Pradeep, J. Colloid
Interface Sci. 209 (1999) 154–161.
65] A. Bigotto, B. Pergolese, J. Raman Spectrosc. 32 (2001) 953–959.
66] J. Coates, in: R.A. Meyers (Ed.), Interpretation of Infrared Spectra, A Practical
Approach, John Wiley and Sons Inc., Chichester, 2000.
[
[
[
67] A. Raj, Y.S. Mary, C.Y. Panicker, H.T. Varghese, K. Raju, Spectrochim. Acta 113
(
2013) 23–36.