Structural, vibrational, electronic, NMR, NLO and reactivity analyses of (3Z)-3-(2-oxo-2-phenylethylidene)-1,3-dihydro-2H-indol-2-one (OPEDI) by ab initio HF and DFT calculations

Article abstract of DOI:10.1016/j.saa.2013.01.044

This study represents the vibrational, electronic, NMR, NLO, reactivity and structural aspects of (3Z)-3-(2-oxo-2-phenylethylidene)-1,3-dihydro-2H-indol-2- one (OPEDI). A detailed interpretation of the FT-IR, FT-Raman, UV and NMR spectra were reported. Th

Full text of DOI:10.1016/j.saa.2013.01.044

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 334–346
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Structural, vibrational, electronic, NMR, NLO and reactivity analyses of
(3Z)-3-(2-oxo-2-phenylethylidene)-1,3-dihydro-2H-indol-2-one (OPEDI)
by ab initio HF and DFT calculations
b
C. Sridevi a, , G. Velraj
⇑
a Department of Physics, Sona College of Technology, Salem 636 005, Tamil Nadu, India
b Department of Physics, Periyar University, Salem 636 011, Tamil Nadu, India
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
This study represents the vibrational, electronic, NMR, NLO, reactivity and structural aspects of (3Z)- 3-
(2-oxo-2-phenylethylidene)-1,3-dihydro-2H-indol-2-one (OPEDI). Theoretical calculations were per-
formed by ab initio HF and density functional theory (DFT)/B3LYP method using 6-311++G(d,p) basis sets.
The stable isomer of OPEDI was calculated by PES scan. The electronic spectrum corresponding to elec-
"
The vibrational, electronic, NMR,
NLO and structural aspects of
(OPEDI) was studied.
PES scan results indicated that the
most stable isomer of OPEDI is Z
isomer.
OPEDI exhibited good NLO activity.
NMR chemical shifts and solvent
effects of OPEDI were studied.
"
tronic transitions are mainly p-
p⁄. NBO analysis and non linear optical activity (NLO) calculations shows
intramolecular charge transfer interactions taking place in OPEDI. The NMR results indicated that the
observed chemical shifts depend on solvent used.
"
"
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 July 2012
Received in revised form 22 December 2012
Accepted 10 January 2013
Available online 30 January 2013
This study represents the vibrational, electronic, NMR, NLO, reactivity and structural aspects of (3Z)-3-(2-
oxo-2-phenylethylidene)-1,3-dihydro-2H-indol-2-one (OPEDI). A detailed interpretation of the FT-IR, FT-
Raman, UV and NMR spectra were reported. Theoretical calculations were performed by ab initio HF and
density functional theory (DFT)/B3LYP method using 6-311++G(d,p) basis sets. The most preferred Z iso-
mer (cis-configuration) was confirmed through PES scan studies. The vibrational wavenumbers and
potential energy distribution (PED) of various normal modes were calculated. The lower frontier orbital
energy gap and high dipole moment of OPEDI illustrates the high reactivity. The stability and charge delo-
calization of the molecule was studied by natural bond orbital (NBO) analysis. OPEDI exhibited good non-
linear optical activity and was 13 times greater than that of urea. Molecular electrostatic potential (MEP)
was carried out for predicting the reactive sites. The NMR results indicated that the observed chemical
shifts depend not only on the structure of the molecule being studied, but also on the solvent used.
Ó 2013 Elsevier B.V. All rights reserved.
Keywords:
(3Z)-3-(2-oxo-2-phenylethylidene)-1,3-
dihydro-2H-indol-2-one
DFT
NLO
NBO
NMR
⇑
Corresponding author. Tel.: +91 427 4099794; fax: +91 427 4099888.
E-mail addresses: sriphysics1@gmail.com (C. Sridevi), gvelraj@yahoo.co.uk (G. Velraj).
1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.01.044

C. Sridevi, G. Velraj / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 334–346
335
Introduction
Spectrometer. The UV pattern was taken from a 10ꢀ5 molar solu-
tion of OPEDI dissolved in DMSO. Data was analyzed by UV PC per-
sonal spectroscopy software, version 3.91. 1H NMR and 13C NMR
spectra were recorded in DMSO-d6 using TMS as an internal stan-
dard on a BRUKER NMR spectrometer at 400 MHz and 100 MHz,
respectively.
Indoles and their derivatives are considered as an important
class of nitrogen containing heterocycles. Oxindole scaffolds are
found as a key structural sub-units in numerous bio-active natural
products and pharmaceutical compounds [1–5]. These scaffolds
play very important role as mediators in synthetic reactions, pri-
marily for preparing numerous heterocyclic compounds with
interesting biological activity [6]. As oxindoles exhibits unprece-
dented structural diversity and biological activities we show more
interest towards it [7,2]. They constitute a major class of naturally
occurring alkaloids, such as vincatine, mitraphylline, herbaline,
crassanine and voachalotin convolutamydines, donaxaridine and
melosatin [8]. In particular, isatin (1H-indole-2,3-dione) and its
derivatives show a variety of biological activities, such as inhibition
of monoamine oxidase, antibacterial, antifungal, antiviral and anti-
proliferative activities [9]. Copper(II), nickel(II) and zinc(II) isatin-
hydrazone complexes were identified as potential antitumor
agents [10]. Recently, some novel oxindoles were found to act as
HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs)
[11]. In addition, oxindoles are used extensively as a photographic
recording materials, liquid crystal displays, photosensitizers,
denaturating agents and ion-selective electrodes [9]. They also find
applications in hair dyes, dyes for plastic, synthetic and natural fi-
bers [9].
Literature is enriched with lots of work on synthesis of potent
substituted oxindole derivatives with diverse pharmacological
activities [12,13]. Detailed knowledge about the structure and
spectral behavior of oxindoles is a necessary prerequisite for
understanding its chemical and biological properties. Herein, we
describe our results on (3Z)-3-(2-oxo-2-phenylethylidene)-1,3-
dihydro-2H-indol-2-one (OPEDI) concerning the structural, vibra-
tional, electronic, NMR, NBO and reactivity analyses through spec-
tral measurements. To the best of our knowledge, this is the first
report on the computational study of OPEDI. Theoretical calcula-
tions were carried out by HF and DFT (B3LYP) with the use of 6-
311G++(d,p) basis sets. The calculated results were compared with
the experimental and the observed spectra were analyzed in detail.
Computational details
For meeting the requirements of both accuracy and computing
economy, theoretical methods and basis sets should be considered.
DFT has proved to be extremely useful in treating electronic struc-
ture of molecules. Initial geometry generated from standard geo-
metrical parameters was minimized without any constraint in
the potential energy surface at Hartree–Fock level, adopting the
standard 6-311++G(d,p) basis set. This geometry was then re-opti-
mized again at B3LYP level using 6-311++G(d,p) basis set for better
description. The entire set of calculation was performed on a Pen-
tium IV/3.06 GHz personal computer using the Gaussian 03 pro-
gram package [15]. Optimized structural parameters were used
in the vibrational frequency, electronic properties and isotropic
chemical shift calculations. The stability of the optimized geometry
was confirmed by frequency calculations, which gave positive val-
ues for all the obtained frequencies. Assignment of the calculated
wave numbers was aided by the animation option of the Gauss-
View 3.0™ graphical interface [16] and VEDA 4 program [17].
However, the vibrational frequency values computed at these lev-
els contain known systematic errors [18]. Therefore, it is custom-
ary to scale down the calculated harmonic frequencies in order
to improve the agreement with the experimental. The electronic
absorption energies were calculated in DMSO by TD-DFT method.
The natural bonding orbitals (NBOs) calculations [19] were per-
formed using NBO 3.1 program as implemented in the Gaussian
03W package at the DFT/B3LYP level. The second order Fock matrix
was carried out to evaluate the donor–acceptor interactions in the
NBO basis [20]. For each donor (i) and acceptor (j), the stabilization
energy E(2) associated with the delocalization i ? j is estimated as
2
Fði; jÞ
E2 ¼
D
Eij ¼ q
ð1Þ
i ej
ꢀ
ei
Experimental
The nuclear magnetic resonance (NMR) chemical shifts calcula-
tions were performed using Gauge-Included Atomic Orbital (GIAO)
method [21,22] at HF and B3LYP levels with 6-311++G(d,p) basis
sets and the 1H and 13C isotropic chemical shifts were referenced
to the corresponding values for TMS, which was calculated at the
same level of theory. The effect of solvent on the theoretical
NMR parameters was included using default IEF-PCM model pro-
vided by GAUSSIAN 03. Dimethylsulfoxide (DMSO) of dielectric
The compound (3Z)-3-(2-oxo-2-phenylethylidene)-1,3-dihy-
dro-2H-indol-2-one (OPEDI) was synthesized and purified accord-
ing to literature procedure [14]. To 1 g of isatin and 0.82 g
acetophenone in 20 mL of absolute alcohol and 2 drops of diethyl-
amine was added. The mixture was allowed to stand overnight at
room temperature. Yellow needles of 3-hydroxy-3-phenacyloxin-
dole formed was recrystallized from alcohol. Then, 3-hydroxy-3-
phenacyloxindole (1 g) and 17 mL of conc.HCl (or 17 ml of 20%
H2SO4) in 3 ml of ethyl alcohol was allowed to stand overnight
(or was heated for half an hour at 100 °C). Fine orange colored nee-
dles of 3-phenacylideneoxindole formed was recrystallized from
ethyl alcohol.
FT-IR spectrum of this compound was recorded in the region
4000–400 cmꢀ1 on Bruker Tensor-27 FTIR-Spectrometer using a
KBr pellet technique at a resolution of 1 cmꢀ1. FT-Raman measure-
ments were carried out on a Varian 7000 series FT-IR-Raman spec-
trometer equipped with a Varian UMA600 microscope (Stingray
system) which can be controlled by resolutions Pro™ software.
FT-Raman spectrum was recorded in the region 3500–100 cmꢀ1
with Nd:YAG laser (1064 nm excitation) operating at a scanning
speed of 90 spectra/s at 8 cmꢀ1 data point resolution. The ultravi-
olet absorption spectrum of OPEDI was examined in the range
200–800 nm using a Shimadzu UV-2401 PC, UV–Vis recording
constant (e
) 46.7 was used as solvent. Calculated 1H and 13C shield-
ing constants for TMS in DMSO solvent at HF and B3LYP levels are
32.59 and 199.9 and 31.82 and 182.4 respectively. To investigate
the reactive sites of the title compound, molecular electrostatic po-
tential computed on
311++G(d,p) method.
q(r) = 0.0004 a.u. surface by B3LYP/6-
Results and discussion
Molecular geometry
The molecular structure of OPEDI belongs to C1 point group
symmetry. The optimized molecular structure of the title molecule
shown in Fig. 1, was obtained using GAUSSIAN 03 program. The
optimized bond lengths, bond angles and torsional angles of OPEDI

336
C. Sridevi, G. Velraj / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 334–346
Fig. 1. The optimized structure of OPEDI.
are listed in Table 1. To the best of our knowledge, exact experi-
mental data on the geometrical parameters of OPEDI is not avail-
able in the literature. Therefore, the crystal data of a closely
related molecule such as (Z)-1-acetyl-3-[2-oxo-1-phenyl-2-(3-pyr-
idyl)ethylidene]indolin-2-one [23] is compared with that of the ti-
tle compound. The calculated values deviated slightly from the
experimental. These deviations may be attributed to the solid state
intermolecular interactions related to crystal packing effects.
The stable isomer of OPEDI was found to be Z (cis-isomer). The
oxindole ring system was planar as indicated from torsional angles
(C5AC4AC9AN1, C8AC9AC4AC3) of 180°. The phenyl ring was
twisted slightly out-of-plane from the oxindole ring, the torsional
angle of C3AC11AC12AC13 is ꢀ80°. It is interesting to note that
the bond lengths of N1AC2 and C2AO10 (oxindole amide group)
were 1.387 Å and 1.212 Å respectively, and this deviation from
the standard NAC and C@O value was due to delocalization of elec-
trons from N atom to the carbonyl group [24].
there will not be any relevant distribution. Fundamental modes
were assigned by comparing calculated values with the experi-
mental. The vibrational band assignments were made by using
both the animation option of GaussView 3.0 graphical interface
for Gaussian 03 [16] and VEDA 4 programs [17]. The calculated fre-
quencies were slightly higher than the observed values for the
majority of the normal modes. Two factors may be responsible
for the discrepancy between the experimental and computed spec-
tra. The first reason may be due to environmental factors and the
second reason is the fact that the experimental value is an anhar-
monic frequency while the calculated one is harmonic. As seen in
Table 2, the FT-IR and FT-Raman intensities of OPEDI are consistent
with the PED results. The experimental and theoretically predicted
FT-IR and FT-Raman spectra are shown in Figs. 3 and 4.
CAH vibrations
Generally, CAH stretching vibrations of aromatic and heteroar-
omatic structures occur around 3000 cmꢀ1 [28]. This permits the
ready identification of the structure. The bands are not much af-
fected in this region due to the nature and position of the substit-
uents. The CAH stretching peaks for the sp2 carbon C(11) appears
at values greater than 3000 cmꢀ1 (3050–3100 cmꢀ1). The benzene
ring CAH in-plane bending vibrations are usually weak and ob-
served in the region 1300–1000 cmꢀ1, while the CAH out-of-plane
bending vibrations lie in the region 900–650 cmꢀ1 [29]. The
stretching bands of OPEDI were observed at 3150 cmꢀ1 in FT-IR
and 3066 cmꢀ1 in FT-Raman spectrum and were also supported
by literature [30]. The calculated mode numbers (83-74) corre-
sponds to CAH stretching bands of pure modes since their PED
contribution is almost 99%. FT-IR and FT-Raman bands at
888 cmꢀ1 and 1145, 1157 cmꢀ1 are assigned to CAH out-of-plane
and CAH in-plane bending vibrations respectively. Computed val-
ues were in good agreement with the experimental and PED contri-
bution is 75%.
Conformational analysis
Potential energy surface scan studies have been carried out in
order to ascertain its cis form due to paucity in reliable experimen-
tal structural data and for the popular notation that the trans form
is more stable [25]. PES scan was done by varying the torsional per-
turbation around the ethylenic bond C3@C11 and the phenyl eth-
ylene bonds (C11AC12, C12AC13) with a step of 10° (Fig. 2). The
high energy domains were found at 10° and 350° with an energy
of ꢀ821.7339 Hartree. The low energy domains were located at
80° and 280° with an energy of ꢀ821.7461 Hartree. The high en-
ergy barriers may be due to the steric interaction between the
p
electrons of carbonyl group and phenyl ring. The low energy do-
mains may be due to the lack of steric interactions and confirms
stable configuration (cis isomer) of OPEDI.
Vibrational assignments
The vibrational frequency and approximate description of each
normal mode of OPEDI is summarized in Table 2. Vibrational fre-
quencies calculated at HF/6-311++G(d,p) and B3LYP/6-
311++G(d,p) level were scaled by 0.8929 [26] and 0.9623 [27]
respectively. The title compound belongs to C1 point group and
has 84 normal modes of fundamental vibrations. For C1 symmetry
NAH vibrations
The NAH stretching vibrations are weaker and sharper than
those of the alcohol OAH stretching and occur in the region
3500–3300 cmꢀ1 [31]. FT-IR band at 3448 cmꢀ1 is assigned to
NAH stretching vibration. NAH out-of-plane bending vibration of
secondary amines appears as a broad band near 800 cmꢀ1 [32]

C. Sridevi, G. Velraj / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 334–346
337
Table 1
Optimized and experimental geometric data for OPEDI in the ground state.
Table 1 (continued)
Parameters
Calculated
Experimental
[23]
Parameters
Calculated
Experimental
[23]
HF/6-
311++G(d,p)
B3LYP/6-
311++G(d,p)
HF/6-
B3LYP/6-
311++G(d,p)
311++G(d,p)
N1AC2AC3AC4
N1AC2AC3AC11
O10AC2AC3AC4
O10AC2AC3AC11
C2AC3AC4AC5
C2AC3AC4AC9
C11AC3AC4AC5
C11AC3AC4AC9
C2AC3AC11AC12
C4AC3AC11AC12
C3AC4AC5AC6
C9AC4AC5AC6
C3AC4AC9AN1
C3AC4AC9AC8
C5AC4AC9AN1
C5AC4AC9AC8
C4AC5AC6AC7
C5AC6AC7AC8
C6AC7AC8AC9
C7AC8AC9AN1
C7AC8AC9AC4
C3AC11AC12AC13
C3AC11AC12AO19
ꢀ0
ꢀ1
ꢀ180
178
ꢀ0
ꢀ179
1
ꢀ1
179
4
ꢀ174
ꢀ180
0
ꢀ0
180
180
ꢀ0
ꢀ0
ꢀ0
0
ꢀ6(11)
–
Bond lengths (Å)
N1AC2
N1AC9
N1AH20
C2AC3
C2AO10
C3AC4
C3AC11
C4AC5
C4AC9
C5AC6
C5AH21
C6AC7
ꢀ179
ꢀ180
1
1.368
1.394
0.993
1.508
1.187
1.474
1.320
1.378
1.394
1.390
1.075
1.385
1.074
1.390
1.075
1.376
1.075
1.511
1.078
1.494
1.188
1.387
1.392
1.386
1.074
1.383
1.075
1.388
1.075
1.380
1.075
1.073
1.387
1.399
1.008
1.512
1.212
1.466
1.340
1.389
1.409
1.397
1.084
1.396
1.083
1.398
1.084
1.386
1.083
1.509
1.087
1.488
1.217
1.399
1.401
1.392
1.083
1.393
1.084
1.396
1.084
1.388
1.084
1.083
–
176(11)
ꢀ7(17)
ꢀ171(11)
4(11)
–
1.429(14)
–
1.388(16)
–
1.461(14)
1.351(14)
1.392(17)
1.414(13)
1.388(16)
–
1.390(17)
–
1.392(17)
–
1.386(15)
–
ꢀ180
0
ꢀ1
179
4
ꢀ175
180
0
ꢀ170(11)
10(15)
ꢀ175(10)
177(11)
2(16)
ꢀ1(12)
ꢀ178(10)
175(9)
ꢀ1(16)
ꢀ1(17)
ꢀ0(18)
1(17)
ꢀ177(10)
ꢀ0(17)
ꢀ95(12)
91(13)
–
–
–
–
–
–
–
–
–
0
ꢀ180
180
ꢀ0
C6AH22
C7AC8
C7AH23
C8AC9
ꢀ0
ꢀ0
C8AH24
C11AC12
C11AH25
C12AC13
C12AO19
C13AC14
C13AC18
C14AC15
C14AH26
C15AC16
C15AH27
C16AC17
C16AH28
C17AC18
C17AH29
C18AH30
0
1.516(15)
–
1.484(15)
1.219(13)
ꢀ180
ꢀ180
0
0
ꢀ86
99
ꢀ80
105
ꢀ4
178
171
ꢀ7
ꢀ178
0
–
–
–
–
–
–
–
–
–
–
–
C11AC12AC13AC14 ꢀ0
C11AC12AC13AC18 ꢀ179
O19AC12AC13AC14 174
O19AC12AC13AC18 ꢀ5
C12AC13AC14AC15 ꢀ179
C18AC13AC14AC15
C12AC13AC18AC17 179
C14AC13AC18AC17
0
179
0
0
C13AC14AC15AC16 ꢀ0
ꢀ0
C14AC15AC16AC17
C15AC16AC17AC18
0
0
0
–
–
0
C16AC17AC18AC13 ꢀ0
ꢀ0
–
Bond angles (°)
C2AN1AC9
112
122
126
106
126
128
106
124
130
133
107
120
119
120
121
118
109
129
122
127
120
114
120
118
122
122
118
120
120
120
120
120
120
112
122
120
105
126
128
106
124
129
132
107
119
119
120
121
117
109
129
121
126
119
113
120
116
122
122
118
119
120
120
120
120
120
109(8)
C2AN1AH20
C9AN1AH20
N1AC2AC3
N1AC2AO10
C3AC2AO10
C2AC3AC4
C2AC3AC11
C4AC3AC11
C3AC4AC5
C3AC4AC9
C5AC4AC9
C4AC5AC6
C5AC6AC7
–
–
and the predicted frequencies are at 855 cmꢀ1 and 828 cmꢀ1
respectively.
106(9)
–
–
106(9)
–
–
–
108(9)
119(10)
119(10)
120(10)
121(10)
117(11)
109(9)
–
Ethylene group vibrations
The ethylene group vibrations are important, for investigating
the isomerisation. Ethylene C@C stretching of OPEDI was observed
as a strong band at 1624 cmꢀ1 in FT-Raman spectrum. CAH in-
plane and out-of-plane bending vibrations of the ethylene group
generally occurs in the region 1423–1328 and 946–740 cmꢀ1
respectively [25]. FT-Raman band at 1269 cmꢀ1 is assigned to
CAH in-plane bending vibration and the predicted value of
860 cmꢀ1 is assigned to CAH out-of-plane bending vibrations.
C6AC7AC8
C7AC8AC9
N1AC9AC4
N1AC9AC8
C4AC9AC8
121(10)
–
–
Phenyl ring vibrations
C3AC11AC12
C3AC11AH25
C12AC11AH25
C11AC12AC13
C11AC12AO19
C13AC12AO19
C12AC13AC14
C12AC13AC18
C14AC13AC18
C13AC14AC15
C14AC15AC16
C15AC16AC17
C16AC17AC18
C13AC18AC17
The ring C@C stretching vibrations usually occur in the region
1625–1430 cmꢀ1 [33]. For aromatic six-membered rings (e.g.) ben-
zenes, there are two or three bands in this region due to skeletal
vibrations, the strongest one at about 1500 cmꢀ1. In the present
work, benzene ring C@C stretch was observed at 1603 and
1604 cmꢀ1 in FT-IR and FT-Raman respectively. The calculated va-
lue for benzene ring stretch was found at 1598 cmꢀ1 and PED con-
tribution is 68%. FT-IR peaks at 680 and 726 cmꢀ1 are assigned to
CACAC in-plane-bending and out-of-plane bending vibrations
respectively. The computed values showed consistent agreement
with the experimental observations.
–
117(9)
120(9)
122(10)
121(9)
119(9)
–
–
–
–
–
–
Torsion angles (°)
C9AN1AC2AC3
C9AN1AC2AO10
C2AN1AC9AC4
C2AN1AC9AC8
Carbonyl vibrations
0
1
5(11)
ꢀ176(10)
ꢀ3(12)
–
180
ꢀ0
180
ꢀ178
The carbonyl C@O stretching vibrations are expected in the re-
gion 1715–1680 cmꢀ1 [34,35]. In the present study, we observe
two peaks for C@O stretching, keto carbonyl at 1712 cmꢀ1 in FT-
ꢀ1
179

338
C. Sridevi, G. Velraj / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 334–346
Fig. 2. Profile of potential energy surface for torsion around ethylene bridge.
Table 2
The observed FTIR, FT-Raman and calculated frequencies using HF/6-311++G and B3LYP/6-311++G for OPEDI.
Symmetry
species C1
HF/6-311++G(d,p)
B3LYP/6-311++G(d,p)
Experimental
Vibrational assignments
Scaled Freq
IIR
IRa (Å4/
Scaled freq
IIR
IRa (Å4/
FTIR
FTRaman
(cmꢀ1
(cmꢀ1
)
(kmmolꢀ1
)
amuꢀ1
)
(cmꢀ1
)
(kmmolꢀ1
)
amuꢀ1
)
(cmꢀ1
)
)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
63
69
93
2
1
0
1
0
1
2
0
4
4
9
3
1
0
1
0
3
13
4
9
4
5
6
1
1
2
4
3
2
1
2
2
4
0
1
1
6
4
5
2
26
33
40
86
91
2
1
0
1
0
0
4
1
7
5
10
9
3
0
2
2
25
42
17
21
7
7
8
0
1
1
10
3
1
0
4
5
4
1
2
1
3
6
6
1
m
x
NAC(33) + d CCC(12)
CCCC(68)
U CCCC(58)
x CCCC(68)
U CCCC(48)
U CCCC(68)
d CCC(16) + U CCCC(18)
U CCCC(22)
d CCC(52)
UCCCC(51)
m
m
123
125
170
188
201
244
284
329
372
399
419
438
447
467
486
507
562
127
147
190
216
262
311
345
369
395
409
414
473
477
480
506
CAC(16) + d NCO (37)
CAC(13) + d CCC(11)
CCCC(57)
x
d CCO(28) +
U CCCC(73)
U CCCC(26) +
U CCCC(16) +
d CCC(30) +
U HNCC(61)
d CCC(21) + UHNCC(24) +
NCCC(14)
m CAC(26)
x
x
CCCC(25)
CCCC(32)
x CCCC (12)
490w
493w
x
21
22
23
24
25
26
27
28
576
586
600
620
642
669
691
732
123
51
2
12
23
2
2
1
7
2
2
12
11
3
550
581
606
607
644
671
678
715
5
60
1
1
24
4
5
9
4
4
4
3
7
1
U CCCC(14)
U CCCC(28)
d CCC(48)
d CCC(86)
d CCC(70)
U HCCC(12) + UCCCC(48)
d CCC(37) + U HCCC(10)
576s
606m
12
6
38
12
680s
726s
U HCCC(16) + U CCCC(12) +
x
NCCC(15)

C. Sridevi, G. Velraj / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 334–346
339
Table 2 (continued)
Symmetry
species C1
HF/6-311++G(d,p)
B3LYP/6-311++G(d,p)
Experimental
Vibrational assignments
Scaled Freq
IIR
IRa (Å4/
Scaled freq
IIR
IRa (Å4/
FTIR
FTRaman
(cmꢀ1
)
(kmmolꢀ1
)
amuꢀ1
)
(cmꢀ1
)
(kmmolꢀ1
)
amuꢀ1
)
(cmꢀ1
)
(cmꢀ1
)
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
751
756
779
805
812
845
879
886
910
929
953
969
970
979
987
1001
1011
1019
1020
1027
1032
1064
1066
1127
1150
1156
1185
1187
1212
1226
1262
1305
1313
1373
1416
1433
1454
1464
14
97
60
42
18
10
1
1
4
39
0
2
2
25
1
0
0
4
0
8
25
5
11
12
1
6
2
14
1
0
14
53
56
0
727
728
756
767
786
828
830
855
860
907
913
933
942
959
973
978
1001
1004
1026
1063
1077
1132
1139
1143
1151
1172
1214
1216
1243
1268
1288
1301
1307
1361
1422
1440
1454
1462
63
38
12
21
5
1
1
11
24
1
2
11
0
0
1
1
27
2
21
2
35
50
1
191
18
5
70
196
45
21
15
1
112
25
16
105
1
4
13
24
7
7
2
U HCCC(33) + d CCC(10)
U HCCC(69) +
CCCC(12) +
U HCCC(11) +
OCNC(57)
x
m
x
NCCC (13)
CAC(10)
CCCC(19)
751s
752m
x
780w
x
d CCC(13) + U HCCN(28)
U HCCC(76)
U HCCN(46)
U HCCC(55)
U HCCC(77)
1
14
36
0
2
12
0
888m
891w
U HCCC(67)
U HCCC(16) +
x CCCC(10)
4
U HCCC(75) + U CCCC(17)
U HCCC(78) + U CCCC(12)
U HCCC(59) + U CCCC(12)
32
24
1
0
4
0
0
56
5
73
19
6
5
25
6
10
2
62
6
27
164
22
3
13
5
m
m
m
m
m
m
m
CAC(35) + d CCC(46)
CAC(44) + d HCC(12)
CAC(25) + d CCC(28)
CAC(36) + d HCC(14)
CAC(11) + d HCC(11)
CAC(27) + d HCC(25)
NAC(14) + d HCC(18)
999s
1002s
1010m
0
1012s
30
18
15
5
24
3
29
6
2
31
26
147
19
9
47
5
16
1
1089m
1115w
48
283
21
20
4
d HCC(65)
1145m
1157m
1165m
1215m
1219m
m
m
CAC(12) + d HCC(71)
CAC(19) + d HCC(68)
d HNC(37) +
m
NAC(13)
m
m
m
m
m
CAC(31) + d HNC(19)
CAC(40)
NAC(13) + d HCC(38)
NAC(35) + d HCC(21)
CAC(33) + d HCC(19)
5
1227vs
66
227
38
6
189
12
20
129
3
1269w
1288m
d HCC(58)
d HCC(56) +
m
CAC(33)
63
8
19
3
1330s
1403ms
m
CAC(40) + d HNC(13)
1404m
1458w
d HCC(53) +
d HCC(41) +
d HCC(48) +
m
m
m
CAC(19)
CAC(22)
CAC(10)
1458s
2
3
2
7
d HCC(52) + d CCC(18)+
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
CAC(11)
CAC(62) + d HCC(11)
CAC(57)
CAC (64) + d HCC(17)
CAC (68)
CAC (74)
CAO (88)
CAO (81)
CAH (100)
CAH (94)
CAH (97)
CAH (93)
CAH (89)
CAH (89)
CAH (97)
CAH (90)
CAH (93)
CAH (90)
NAH (100)
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
1542
1553
1573
1583
1588
1615
1646
2880
2894
2898
2905
2905
2915
2915
2924
2925
2933
3313
51
7
22
12
163
33
267
519
245
46
45
18
102
131
78
1558
1569
1576
1594
1628
1657
1723
3023
3045
3048
3054
3056
3064
3064
3072
3074
3081
3507
13
2
12
9
1562s
1566m
1577w
1604m
1624w
1647s
40
167
218
296
307
0
0
2
4
8
19
30
11
17
6
33
109
35
240
419
1
0
2
3
6
22
15
10
15
7
185
330
781
138
12
58
48
17
111
140
76
103
183
334
174
142
1603s
1653vs
1712s
75
166
274
134
108
3066 ms
3150s
3448 m
93
62
t
, stretching; d, in-plane bending; x, out of plane bending; U torsion.
IR and the amide carbonyl group at 1653 and 1647 cmꢀ1 in FT-IR
and FT-Raman spectrum respectively.
absorption wavelengths calculated by the TD(DFT)/B3LYP/6-
311++G(d,p) level and the experimental value, excitation energy,
oscillator strength and composition of the most significant singlet
excited states are listed in Table 3. All transitions were found to be
monodeterminantal. As can be seen from the figure, electronic
absorption spectrum of OPEDI shows two bands at 327 and
447 nm. From TD-DFT calculation, the theoretical absorption bands
are predicted at 326, 343 and 405 nm. HOMO and LUMO orbitals
Electronic properties
The electronic absorption spectrum of the title compound was
recorded in DMSO solvent within the range 200–800 nm and the
computed plot on the experimental is shown in Fig. 5. Electronic

340
C. Sridevi, G. Velraj / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 334–346
Fig. 3. Comparision of the calculated and experimental IR spectra of OPEDI.
for the title molecule is represented in Fig. 6. The frontier orbitals,
HOMO and LUMO determine the way a molecule interacts with
other species and helps to characterize the chemical reactivity
and kinetic stability of the molecule [36]. A molecule with a low
frontier orbital gap is more polarizable and will exhibit a signifi-
cant degree of ICT from the electron-donor to the electron-acceptor
stronger is the intermolecular interaction [38]. The lower frontier
orbital energy gap (
(6.596D) illustrates the high reactivity of OPEDI (Table 3).
D
E(HAL) = ꢀ3.73 eV) and high dipole moment
NBO analysis
groups through
p conjugated path [37]. As shown in Fig. 6, the
The natural bond orbital analysis provides an efficient method
for studying intra- and intermolecular bonding and interaction
among bonds, and also provides a convenient basis for investigat-
ing charge transfer or conjugative interaction in molecular systems
[39]. The larger the E(2) value, the more intensive is the interaction
between electron donor and electron acceptor, i.e. the more donat-
ing tendency from electron donor to electron acceptor and greater
the extent of conjugation of the whole system. Delocalization of
electron density between occupied Lewis-type (bond or lone pair)
NBO orbitals and formally unoccupied (antibond or Rydgberg) non-
Lewis NBO orbitals correspond to a stabilizing donor–acceptor
interaction. NBO analysis was performed on the title molecule
(OPEDI) at the B3LYP/6-311++G(d,p) level in order to elucidate
the delocalization of electron density within the molecule. Orbital
overlap between bonding n(LP1N1) and antibonding pꢁ(C2AO10),
pꢁ(C8AC9) orbital results in an intramolecular charge transfer
LUMO orbitals are distributed over the entire molecule. In contrast,
HOMO is located only on the oxindole ring, and consequently
HOMO ? LUMO transition implies electron density transfer from
the oxindole ring to the phenyl ring. This explains a significant de-
gree of intramolecular charge transfer from the electron-donor
groups to electron-acceptor groups through conjugated path. In
addition the lower frontier orbital gap (
D
E(HAL) = ꢀ3.73 eV) of
OPEDI indicates the eventual charge transfer interaction taking
place within the molecule. Molecular orbital coefficient analysis
showed that the frontier molecular orbital (FMOs) is composed
mainly of p-atomic orbitals. Hence, the electronic spectrum corre-
sponding to electronic transitions are mainly
p ?
pꢁ. The dipole
moment in a molecule is an important property that is mainly used
to study the intermolecular interactions involving the non bonded
type dipole–dipole interactions. The higher the dipole moment, the

C. Sridevi, G. Velraj / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 334–346
341
Fig. 4. Comparision of the calculated and experimental Raman spectra of OPEDI.
Fig. 5. Experimental vs. TD-DFT UV spectra of OPEDI.
(ICT) causing stabilization of the system. These interactions are ob-
served as an increase in electron density (ED) in C2AO10, C8AC9
anti-bonding orbital that weakens the respective bonds. The
second-order perturbation theory of the Fock matrix in the NBO
analysis shows strong intramolecular hyperconjugative interac-
tions, which are presented in Table 4. The most important interac-

342
C. Sridevi, G. Velraj / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 334–346
Table 3
Wavelength k (nm), excitation energies (eV), oscillator strength (f), absolute energies (Hartree), frontier orbital energies (eV), dipole moment (D) and composition of the most
significant singlet excited states for OPEDI at the B3LYP/6-311++G(d,p) level of theory.
Transition Experimental k
TD(DFT) method
MOs
(nm)
k
Excitation energy, E
Oscillator
(nm)
(eV)
strength, f
I
II
III
447
327
405
343
326
3.06
3.61
3.80
Etotal
EHOMO
ELUMO
0.039
0.047
0.046
ꢀ821.74605
ꢀ6.24
ꢀ2.50
ꢀ3.73
6.596
91%(H ? L)
56%(H ? L+1) + 24%(H1 ? L) + 8%(Hꢀ4 ? L)+2%(H-4 ? L + 1)
35%(H?L + 1) + 31%(H4 ? L) + 13%(Hꢀ1 ? L) + 9%(Hꢀ3 ? L) + 2%(Hꢀ5 ? L + 1)
D
E
Dipole moment
tion energies of n(LP1N1) ? pꢁ(C2AO10) and n(LP1N1) ? pꢁ(C8AC9)
are 223.93 and 157.32 kJ/mol respectively. This larger energy
shows the hyperconjugation interaction between the electron
donating group to the acceptor group in OPEDI.
LUMO PLOT
(First excited state)
Nonlinear optical effects
ELUMO = -6.24eV
NLO is at the forefront of current research because it provides
the key functions to frequency shifting, optical modulation, opti-
cal switching, optical logic, and optical memory for the emerging
technologies in areas such as telecommunications, signal pro-
cessing, and optical interconnections [40,41]. Many organic mol-
ecules, containing conjugated
p electrons characterized by large
values of molecular first hyperpolarizabilities were analyzed by
means of vibrational spectroscopy [42]. Even in the absence of
inversion symmetry, in most cases, the strongest bands in the
Raman are weak in the infrared and vice versa. But the intra-
molecular charge transfer from the donor to the acceptor group
through single-double bond conjugated path can induce large
variations of both the molecular dipole moment as well as
molecular polarizability, making IR and Raman activity strong
at the same time [43,44]. The ring CAC and C@O stretching
was found to be strong and simultaneously active both in FT-
IR and FT-Raman. Ring CAC stretching was observed at 1603
and 1604 cmꢀ1 in FT-IR and FT-Raman. Peaks at 1653 and
1647 cmꢀ1 was due to ring C@O stretching. Hence, the stretching
mode of OPEDI clearly points the charge transfer interaction be-
tween oxindole ring and phenyl ring through the ethylenic
Δ E = -3.73eV
EHOMO = -2.50eV
HOMO PLOT
(Ground state)
Fig. 6. Molecular orbital surfaces for the HOMO and LUMO of OPEDI.
Table 4
Second order perturbation theory analysis of Fock matrix in NBO basis.
Donor (i)
ED (e)
Acceptor (j)
ED (e)
E(2)a (kJ molꢀ1
)
E(i) ꢀ E(j)b (kJ molꢀ1
)
F(i,j)c (kJ molꢀ1
)
r
r
r
r
r
r
r
r
r
r
(C3AC4)
(C3AC11
(C4AC5)
(C4AC5)
(C5AC6)
(C7AC8)
(C8AC9)
1.9666
1.9777
1.9728
1.9728
1.9752
1.9753
1.9761
1.9778
1.9778
1.9634
1.9802
1.8495
1.8495
1.6640
1.6640
1.6640
1.6714
1.6714
rꢁ(C3AC11
rꢁ(C3AC4)
rꢁ(C3AC4)
rꢁ(C4AC9)
rꢁ(C3AC4)
)
0.0184
0.0314
0.0314
0.0293
0.0314
0.0256
0.0293
0.0314
0.0184
0.0795
0.1067
0.2828
0.3709
0.1067
0.3427
0.3778
0.3709
0.3778
20.46
20.21
19.41
18.7
21.71
26.19
20.59
20.21
12.09
28.53
16.48
66.9
51.88
54.06
75.4
92.01
89.33
71.46
3439.41
3281.88
3124.35
3281.88
3098.09
2940.56
3334.39
2966.82
3413.15
2441.72
1102.71
787.65
840.16
787.65
735.14
735.14
735.14
735.14
189.04
183.79
173.28
175.91
183.79
196.91
186.41
173.28
144.4
189.04
97.14
168.03
154.9
)
rꢁ(N1AC9)
rꢁC4AC9)
rꢁ(C3AC4)
(C11AC12
(C11AC12
)
)
)
rꢁ(C3AC11
rꢁ(C2AC3)
)
(C11AH25
(C2AO10
p
p
p
p
p
p
p
p
)
pꢁ(C3AC11
pꢁ(C2AO10
pꢁ(C4AC5)
)
)
(C3AC11
(C3AC11
(C4AC5)
(C4AC5)
(C4AC5)
(C6AC7)
(C6AC7)
)
)
pꢁ(C3AC11
pꢁ(C6AC7)
pꢁ(C8AC9)
pꢁ(C4AC5)
pꢁ(C8AC9)
)
154.9
168.03
186.41
183.79
162.78

C. Sridevi, G. Velraj / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 334–346
343
Table 4 (continued)
Donor (i)
ED (e)
Acceptor (j)
ED (e)
E(2)a (kJ molꢀ1
)
E(i) ꢀ E(j)b (kJ molꢀ1
787.65
761.4
1076.46
708.89
735.14
761.4
735.14
761.4
)
F(i,j)c (kJ molꢀ1
)
p
p
p
p
p
p
p
p
p
p
(C8AC9)
(C8AC9)
(C12AO19
1.6632
1.6632
1.9747
1.6312
1.6312
1.6312
1.6499
1.6499
1.6516
1.6516
1.6705
1.6705
1.9779
1.8451
1.8451
1.8706
1.8706
pꢁ(C4AC5)
pꢁ(C6AC7
0.3709
0.3427
0.3672
0.1409
0.3199
0.2812
0.3672
0.2812
0.3672
0.3199
0.2828
0.3778
0.0795
0.0804
0.0795
0.0614
0.0670
70.25
91.46
19.66
80.92
77.74
82.34
91.76
73.09
80.33
91.71
223.93
157.32
11.92
116.02
83.47
84.64
71.55
168.03
189.04
112.9
)
pꢁ(C13AC14
)
)
(C13AC14
(C13AC14
(C13AC14
(C15AC16
(C15AC16
(C17AC18
(C17AC18
)
)
pꢁ(C12AO19
181.16
170.66
181.16
186.41
170.66
173.28
183.79
294.06
249.42
131.28
328.19
273.05
275.68
262.55
pꢁ(C15AC16
pꢁ(C17AC18
pꢁ(C13AC14
pꢁ(C17AC18
pꢁ(C13AC14
pꢁ(C15AC16
)
)
)
)
)
)
)
)
)
)
)
735.14
735.14
761.4
n(LP1N1)
n(LP1N1)
n(LP1O10
n(LP2O10
n(LP2O10
n(LP2O19
n(LP2O19
pꢁ(C2AO10
pꢁ(C8AC9)
rꢁ(C2AC3)
)
761.4
)
)
)
)
)
2835.54
1785.34
1706.58
1732.83
1864.11
rꢁ(N1AC2)
rꢁ(C2AC3)
rꢁ(C11AC12
rꢁ(C12AC13
)
)
a
b
c
E(2) means energy of hyperconjugative interactions; cf. Eq. (1).
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.
Table 5
Table 6
Experimental and calculated 13C NMR chemical shifts (ppm) of OPEDI.
The first hyperpolarizability bijk and btot (ꢂ10ꢀ31 cm5/esu) values for OPEDI.
bxxx
bxxy
bxyy
byyy
bxxz
bxyz
byyz
bxzz
byzz
bzzz
btot
ꢀ0.6224
Carbon
HF/6-311++G(d,p)
B3LYP/6-311++G(d,p)
EXP
33.6900
ꢀ16.9680
ꢀ0.67746
ꢀ3.1296
3.4930
C2
C3
C4
C5
C6
C7
C8
C9
C11
C12
C13
C14
C15
C16
C17
C18
184.22
141.15
131.12
138.41
131.96
147.77
119.93
157.88
149.93
211.74
146.0
148.18
139.22
151.29
139.60
144.94
172.14
139.50
127.38
126.14
126.42
136.91
113.53
148.59
140.53
205.70
142.30
137.01
133.56
140.64
133.85
132.71
168.12
136.99
119.90
121.73
126.62
126.00
110.35
134.06
144.88
191.12
136.32
129.14
128.54
132.90
128.54
129.14
ꢀ1.2197
ꢀ12.1383
1.8645
14.5815
46.9563
Table 7
Experimental and calculated 1H NMR chemical shifts (ppm) of OPEDI.
Proton
HF/6-311++G(d,p)
B3LYP/6-311++G(d,p)
Exp.
H20
H21
H22
H23
H24
H25
H26
H27
H28
H29
H30
8.21
8.97
7.95
8.50
7.88
8.48
8.97
8.40
8.89
8.58
9.65
7.47
8.28
7.34
7.72
7.16
7.60
8.28
7.85
8.03
7.98
8.64
10.824
8.085
6.975
7.371
8.085
6.881
8.021
7.629
7.726
7.629
8.021
Fig. 7. Electrostatic potentials of OPEDI (B3LYP/6-311++G(d,p), 0.0004a.u., energy
values ꢀ35.1656 to +35.1656 kcal/mol); color coding: red (very negative), orange
(negative), yellow (slightly negative), green (neutral), turquoise (slightly positive),
light blue (positive), dark blue (very positive) (For interpretation of the references
to color in this figure legend, the reader is referred to the web version of the article).
Molecular electrostatic potential (MEP)
bridge. The
p-electron cloud movement from donor to acceptor
can make the molecule highly polarizable and the intra molecu-
lar charge transfer interaction must be responsible for the NLO
properties of OPEDI. The hyperpolarizability value btot calculated
by DFT/B3LYP/6-311++G(d,p) method based on the finite field
approach theory are listed in Table 5. The title compound dis-
plays excellent second order NLO property (btot = 46.95633 -
ꢂ 10ꢀ31 cm5/esu) and was 13 times the magnitude of urea (b
of urea is 3.7289 ꢂ 10ꢀ31 cm5/esu).
The electrostatic potential is used primarily for predicting reac-
tive sites and relative reactivities towards electrophilic attack, and
in studies of biological recognition and hydrogen bonding
interactions [45,46]. To predict reactive sites for electrophilic and
nucleophilic attack for the investigated molecule, the MEP at the
B3LYP/6-311++G(d,p) optimized geometry was calculated. The
negative (red and yellow) regions of the MEP are related to electro-
philic reactivity and the positive (blue) regions to nucleophilic

344
C. Sridevi, G. Velraj / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 334–346
Fig. 8. 1H NMR spectrum of OPEDI.
reactivity, as shown in Fig. 7. The electrostatic potential ranges
from ꢀ35.1656 to +35.1656 kcal/mol with dark blue denoting ex-
treme electron deficient regions (V(r) > 35.1656 kcal/mol) and red
denoting electron rich regions (V(r) < ꢀ35.1656 kcal/mol). As it
can be seen from the figure, negative region is mainly localized
over the oxygen atoms of the two carbonyl group indicating a pos-
sible site for electrophilic attack. The maximum positive region is
amide group (NAH20) appears at higher chemical shift of
10.82 ppm due to electronegative nitrogen atom. A peak at
6.89 ppm was due to olefinic hydrogen atom (H25). Multiplet sig-
nals at 8.02, 7.72 and 7.62 ppm indicates the presence of aromatic
hydrogen atoms (H28, H29 and H30) in the phenyl ring. The calcu-
lated 1H and 13C NMR chemical shifts of OPEDI were compared
with the experimental data. The predicted 1H chemical shift values
of DFT were in closer agreement with the experimental for most of
the protons, except for the polar NAH proton.
The observed chemical shifts, depend not only on the struc-
ture of the molecule being studied, but also on the interaction
of the molecule with the surrounding solvent. The solute–solvent
interactions are weak in nonpolar solvents (hydrocarbons) and
strong in polar solvents (e.g. acetone or dimethyl sulfoxide).
Whereas the solute–solvent interaction between polar solvent
and polar solute are likely to be stronger than polar solute and
tetramethylsilane (TMS, which is non polar) and hence the ob-
served chemical shift of the molecule of interest will be shifted.
However, hydrogen exchangeable groups seem to be affected
alot and have been provided useful applications in structure
determination. Solvents like deuterium oxide (D2O), benzene-d6
(C6D6), acetone-d6 (CD3COCD3) and DMSO-d6 (CD3SOCD3) have
localized on the amide (NAH) hydrogen with
a
value
of +35.1656 kcal/mol, indicating a possible site for nucleophilic at-
tack. These sites give information about the region from where the
compound can have intermolecular interactions.
NMR spectra
The experimental and theoretical values for 1H and 13C NMR of
the OPEDI are given in Tables 6 and 7. The NMR spectrum of OPEDI
was recorded in DMSO-d6 (Figs. 8 and 9) and the effect of solvent is
described in detail. The theoretical chemical shift values were cal-
culated by HF, DFT/B3LYP methods using 6-311++G(d,p) basis set.
In general, highly shielded protons appear downfield and vice ver-
sa. In 13C NMR spectrum, 14 different signals were observed and
were consistent with the structure on the basis of molecular geom-
etry. Signals for aromatic carbons were observed in the range 110–
145 ppm as expected. Carbonyl carbon C12 was observed down-
field at 191.1 ppm. A peak at 144.8 was due to olefinic carbon
(C11). Oxindole amide carbon C2 seems to be more deshielded
due to the presence of neighboring nitrogen and oxygen atoms
and is observed at higher chemical shift of 168.1 ppm. Peaks at
8.08, 7.37 and 6.97 ppm is due to the aromatic hydrogens (H24,
H23 and H22) in the oxindole ring. Hydrogen atom of an oxindole
p-electron functions and/or may serve as hydrogen bonding
partners, resulting in changes in the chemical shifts of certain
groups of protons [32,47].
In our present work, 1H NMR (for most of the protons) and 13C
spectrum seems to be unaffected, while the shift is larger for oxin-
dole amide (ANH) hydrogen atom. This is due to the strong hydro-
gen bonding of the polar group (ANH) to the sulfoxide oxygen,
which not only de-shields the amine proton, but also secures it

C. Sridevi, G. Velraj / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 334–346
345
Fig. 9. 13C NMR spectrum of OPEDI.
Table 8
Esolv of OPEDI in different solvents.
Conclusion
D
Vibrational, electronic, NMR, NLO, reactivity and structural as-
pects of (3Z)-3-(2-oxo-2-phenylethylidene)-1,3-dihydro-2H-in-
dol-2-one (OPEDI) were studied in detail using ab initio HF and
DFT methods and the results were also compared with the exper-
imental. PES scan calculations revealed that the most stable isomer
Environment
Energy (a.u)
DE
kcal/mol
kJ/mol
In vacuum
DMSO-d6
CDCl3
ꢀ821.746057
ꢀ821.774850
ꢀ821.766041
–
–
ꢀ18.07
ꢀ75.61
ꢀ12.54
ꢀ52.48
of OPEDI is
calculated and the most prominent transition corresponds to
pꢁ. The strong and simultaneous activity of ring C@C and
Z (cis isomer). The electronic transitions were
p
?
from very rapid exchange reactions that prevents the display of
spin–spin splitting.
The solvent effect was also studied by SCRF PCM model. The sta-
bility of OPEDI in two different solvents, namely CDCl3 and DMSO
C@O stretch modes of OPEDI explains the intramolecular charge
transfer interactions. The title compound exhibits excellent NLO
activity and was thirteen times the magnitude of urea. MEP pre-
dicts that the amide hydrogen and two carbonyl oxygens are the
most reactive sites for nucleophilic attack and electrophilic attack,
respectively. The higher chemical shift of oxindole amide (ANH)
hydrogen in NMR spectrum was due to the interaction of OPEDI
with the surrounding solvent (DMSO-d6). We hope our results will
be of assistance in the quest of the experimental and theoretical
evidence for the title molecule in reaction intermediates, nonlinear
optical and photoelectric materials and will also be helpful for the
design and synthesis of new materials.
(
D
Esolv) were calculated to characterize the strength of their
respective interaction with OPEDI. Esolv was calculated according
to Eq. (2) by means of the PCM method implemented in Gaussian
03 package [48].
D
D
Esolv ¼ EðsolnÞ ꢀ E
The results are summarized in Table 8.
ð2Þ
ðin vacuumÞ
D
Esolv of OPEDI in
DMSO-d6 is the largest, indicating the strong interaction is be-
tween OPEDI and DMSO-d6, while it is least strong in CDCl3. The
higher chemical shift of oxindole amide (ANH) hydrogen was
due to high affinity of DMSO-d6 with the OPEDI. This is also sup-
ported by our MEP results which predicts the oxindole amide
hydrogen to be the most reactive part of the molecule.
Acknowledgements
CS acknowledges Dr. G. Shanthi, Sona College of Technology,
Salem for her support and encouragement. The author is also

346
C. Sridevi, G. Velraj / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 107 (2013) 334–346
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thankful to Jawaharlal Nehru University, New Delhi and Annamalai
University, Chidambaram for the spectral facilities.
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