Synthesis, spectroscopic (FT-IR, FT-Raman, UV and NMR) and computational studies on 3t-pentyl-2r,6c-diphenylpiperidin-4-one semicarbazone

Article abstract of DOI:10.1016/j.saa.2015.03.117

The structural and spectroscopic studies of 3t-pentyl-2r,6c-diphenylpiperidin-4-one semicarbazone (PDPOSC) were made by adopting B3LYP/HF levels theory using 6-311++G(d,p) basis set. The FT-IR and Raman spectra were recorded in solid phase, the fundamenta

Full text of DOI:10.1016/j.saa.2015.03.117

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
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Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, spectroscopic (FT-IR, FT-Raman, UV and NMR) and
computational studies on 3t-pentyl-2r,6c-diphenylpiperidin-4-one
semicarbazone
a
b
M. Arockia doss a, S. Savithiri a, G. Rajarajan a, , V. Thanikachalam , H. Saleem
⇑
a Department of Chemistry, Annamalai University, Annamalainagar 608 002, India
b Department of Physics, Annamalai University, Annamalainagar 608 002, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
ꢀ
ꢀ
Conformational analysis.
Ab initio HF and DFT calculations.
Tentative assignments are made
based on the TED values.
ꢀ
The theoretical UV–visible spectrum
has a good concordance with the
experimental one.
ꢀ
The calculated 1H and 13C chemicals
shifts are in good agreement with the
experimental ones.
a r t i c l e i n f o
a b s t r a c t
Article history:
The structural and spectroscopic studies of 3t-pentyl-2r,6c-diphenylpiperidin-4-one semicarbazone
(PDPOSC) were made by adopting B3LYP/HF levels theory using 6-311++G(d,p) basis set. The FT-IR and
Raman spectra were recorded in solid phase, the fundamental vibrations were assigned on the basis of
the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics
(SQM) method and PQS program. DFT method indicates that B3LYP is superior to HF method for molecu-
lar vibrational analysis. UV–vis spectrum of the compound was recorded in different solvents in the
region of 200–800 nm and the electronic properties such as excitation energies, oscillator strength, wave-
lengths, HOMO and LUMO energies were evaluated by time-dependent DFT (TD-DFT) approach. The
polarizability and first order hyperpolarizability of the title molecule were calculated and interpreted.
The hyperconjugative interaction energy (E(2)) and electron densities of donor (i) and acceptor (j) bonds
were calculated using NBO analysis. In addition, MEP and atomic charges of carbon, nitrogen and oxygen
were calculated using B3LYP/6-311++G(d,p) level theory. Moreover, thermodynamic properties of the
title compound were calculated by B3LYP/HF, levels using 6-311++G(d,p) basis set. The 1H and 13C
nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the gauge
independent atomic orbital (GIAO) method and compared with experimental results.
Received 15 August 2014
Received in revised form 11 March 2015
Accepted 27 March 2015
Available online 3 April 2015
Keywords:
Semicarbazone
HOMO–LUMO
NBO
NLO
NMR
Ó 2015 Elsevier B.V. All rights reserved.
Introduction
having piperidin-4-one nucleus have aroused great interest in
the past and also in recent years due to their biological activities
Piperidine ring is one of the important structural entities among
heterocyclic molecules [1]. Attention has been focused on struc-
ture–activity relationship of such compounds. Primarily systems
like antiviral [2], antitumor [3], antiinflammatory [4], central ner-
vous system [5], anticancer [6] and antibacterial activity [7].
Piperidines with substituents at C3 and C5 have increased biologi-
cal activity compared to other piperidines. Non-linear optical
(NLO) materials play a vital role in the field of fiber optic commu-
nications and optical signal process. In the last two decades,
⇑
Corresponding author. Tel.: +91 9444147388.
E-mail address: rajarajang70@gmail.com (G. Rajarajan).
http://dx.doi.org/10.1016/j.saa.2015.03.117
1386-1425/Ó 2015 Elsevier B.V. All rights reserved.

190
M. Arockia doss et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
intensive research has shown that organic crystals also exhibit
nonlinear optical efficiencies which are of greater magnitude than
those of inorganic materials. Semicarbazones and thiosemicar-
bazone of substituted heterocyclic organic compounds, ketones
and acetophenones were reported to be potential organic NLO
[8–10] materials.
Computational details
The combination of vibrational spectroscopy with quantum
chemical calculations is effective for understanding the fundamen-
tal modes of vibrations of compounds. The structural characteris-
tics, stability, thermodynamic properties of the compound under
investigation are determined by B3LYP and HF levels theories,
using 6-311++G (d,p) basis set in Gaussian 03W program [14].
The optimized structural parameters were used in the vibrational
frequency calculations resulting in IR and Raman frequencies along
with intensities and Raman depolarization ratios, thermodynamic
properties and energies of the optimized structures. The vibra-
tional modes were allotted on the premise of TED analysis using
SQM program [15]. HF and DFT hybrid B3LYP functional methods
tend to overestimate the fundamental modes and hence the scaling
factors 0.9608 and 0.9051 [16] have been uniformly applied to the
B3LYP and HF methods, respectively.
To investigate the reactive sites of the title molecule, the molecu-
lar electrostatic potential was evaluated. Moreover, in order to show
nonlinear optical (NLO) activity of PDPOSC molecule, the dipole
moment, linear polarizability and first order hyperpolarizability
were obtained from molecular polarizabilities based on theoretical
calculations. The electronic properties, such as HOMO–LUMO ener-
gies were calculated using TD-DFT/6-311++G(d,p) based on the
optimized structure in gas phase and in solvents (methanol and
chloroform). NBO [14] analysis was carried out so as to elucidate
inter- and intramolecular interactions in the title molecule.
Raman intensities were calculated by the procedure described in
literature [17].
Now a days NIR-FT-Raman spectrographic analysis combined
with quantum chemical computations are employed as an effective
tool in the vibrational analysis of biological compounds [11,12] and
natural products, since fluorescence-free Raman spectra and the
computed results can help unambiguous identification of vibra-
tional modes and also as the bonding and structural features of
complex organic molecular systems. The present study aimed at
to investigate the molecular structural properties, vibrational and
energetic data of PDPOSC, in gas phase, due to its pharmaceutical
importance. The ground and the excited state properties of the title
molecule are calculated using DFT/B3LYP and HF levels of theories
using 6-311++G(d,p) basis set. As vibrational and electronic spec-
troscopic studies provide very useful information about the struc-
ture and conformation of the molecules if used in synergy with
quantum chemical calculations, to obtain a complete description
of molecular dynamics, vibrational wavenumber calculation along
with the normal mode analysis has been administered at the DFT/
HF level theories. The investigation of geometry, dipole moment,
polarizability, first static hyperpolarizability, along with the
molecular electrostatic potential surface will lead to better under-
standing of the structural and spectral characteristics of the com-
pound chosen for study.
Experimental details
Results and discussion
Synthesis of 3t-pentyl-2r,6c-diphenylpiperidin-4-one semicarbazone
Conformational analysis
3t-pentyl-2r,6c-diphenylpiperidin-4-one was synthesized as
per the procedure described in literature [13]. Semicarbazone
derivative of 3t-pentyl-2r,6c-diphenylpiperidin-4-one was pre-
pared by the reaction of the ketone with semicarbazide hydrochlo-
In piperidone derivatives the most stable conformer is the chair
form [18–20]. The semicarbazone analogue has rotatable bonds,
and so several conformers (Fig. S1) are possible for PDPOSC.
These structures were subjected to more accurate computations
using B3LYP/6-311++G(d,p) and the ground state energy, energy
difference and dipole moment of conformers are presented in
Table 1.
From the calculated energies the conformer 1 is found to be
more stable. In order to explain conformational flexibility of the
stable conformer, the energy profile as a function of H–C–C–C tor-
sional angle is shown in Fig. 1. All the geometrical parameters were
at the same time relaxed throughout the calculations whereas the
H–C–C–C torsional angle was varied in steps of 10°. The torsional
potential surface of molecule was obtained by using semi-empiri-
cal (Austin Model, AM1) methodology. As can be seen from Fig. 1,
the foremost conformer is with 180° (and ꢁ180°) torsional angle
(H37–C35–C3–C4). A local minima was obtained for 10°. The opti-
mized geometry of the molecule is coplanar.
ride. To
a solution of 3t-pentyl-2r,6c-diphenylpiperidin-4-one
(0.01 mol) in 45 mL methanol and few drops of conc. HCl were
added. Then, semicarbazide (previously dissolved in 20 mL metha-
nol) solution (0.01 mol) was added drop wise with stirring. The
reaction mixture was refluxed for 3 h on a heating mantle. After
cooling, the solid product was filtered off and recrystallized from
20 mL methanol. Yield 75%; m.p.: 154 (°C); MF: C23H30N4O;
Elemental analysis: Calcd (%): C, 72.98; H, 7.99; N, 14.80; found
(%): C, 72.93; H, 7.70; N, 14.89.
Spectral measurements
The FT-IR spectrum of the synthesised piperidone semicar-
bazone was measured in the range 4000–500 cmꢁ1 in AVATAR-
330 FT-IR spectrometer (Thermo Nicolet) using KBr (pellet form)
in the Department of Chemistry, Annamalai University,
Annamalainagar. The FT-Raman spectrum of PDPOSC has been
recorded using 1064 nm line Nd:YAG laser with excitation wave-
length of 1064 nm in the region 100–4000 cmꢁ1 on a thermo
Electron corporation model Nexus 670 spectrophotometer
equipped with FT-Raman module accessory. The FT-Raman spec-
trum was taken at Central Electro Chemical Research Institute,
Karaikudi, Tamilnadu. Microanalyses were performed on
VarioMicro V2.2.0 CHN analyser. 1H NMR spectrum was recorded
at 400 MHz and 13C NMR spectrum at 100 MHz on a BRUKER
model using CDCl3 as solvent. Tetramethylsilane (TMS) was used
as internal reference for all NMR spectra, with chemical shifts
reported in d units (parts per million) relative to the standard.
Molecular geometry
The optimized structural parameters such as bond lengths,
bond and dihedral angles of PDPOSC were determined at B3LYP/
HF level theories with 6-311++G(d,p) basis set and are presented
in Table S1 in accordance with the atom numbering scheme of
the molecule shown in Fig. 2. To the best of our knowledge, no sin-
gle crystal X-ray crystallographic data of PDPOSC has yet been
reported. However, the theoretical results obtained are almost
comparable with closely related molecules such as 3t-pentyl-
2r,6c-diphenylpiperidine-4-one [21] and (E)-2-(hexan-2-yli-
dene)hydrazinecarboxamide [22].

M. Arockia doss et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
191
Table 1
Calculated energies and energy differences of possible conformers of the PDPOSC by DFT (B3LYP/6-311++G(d, p)) method.
Conformers
Energy
Energy differences
(Hartree)
Dipole moment
(Hartree)
(kcal/mol)
(kcal/mol)
(Debye)
Conf-1
Conf-2
Conf-3
Conf-4
Conf-5
Conf-6
Conf-7
Conf-8
ꢁ1189.05932
ꢁ1189.04865
ꢁ1189.04831
ꢁ1189.04665
ꢁ1189.04249
ꢁ1189.04065
ꢁ1189.03097
ꢁ1188.78092
ꢁ746146.61
ꢁ746139.92
ꢁ746139.7
ꢁ746138.66
ꢁ746136.05
ꢁ746134.9
ꢁ746128.82
ꢁ745971.92
0
0
4.52
4.50
3.97
4.49
4.79
4.27
5.77
4.01
ꢁ0.0106688
ꢁ0.0110072
ꢁ0.0126688
ꢁ0.0168298
ꢁ0.0186688
ꢁ0.0283503
ꢁ0.2783955
ꢁ6.6948
ꢁ6.9071
ꢁ7.9498
ꢁ10.561
ꢁ11.715
ꢁ17.79
ꢁ174.7
is ꢂ1 Å. The predicted bond length lies between 1.0887–1.0986 Å
(B3LYP) and 1.0797–1.0892 Å (HF) for heterocyclic ring. The aver-
age bond distance of C1–N12 and C5–N12 are 1.471 and 1.461 Å by
B3LYP and HF, respectively in which B3LYP value is in line with
literature value 1.471 Å [21]. The N52–C53–O58 and N54–C53–
O58 angles are found to be 120.04 and 125.33° (B3LYP) and
120.07 and 124.19° (HF). Difference within the values are as a
result of inter- and intramolecular hydrogen bonding. The length-
ening of N54–H56 bond by about 0.138 Å/B3LYP and 0.121 Å/HF
and shortening of C53–O58 bond by about 0.031 Å (B3LYP) and
0.033 Å (HF) indicate the possibility of N54–H56. . .O58 hydrogen
bonding. Piperidine ring essentially adopts chair conformation,
with all substituents equatorial as evident from the torsional
angles N12–C1–C2–C3 = ꢁ54.21, ꢁ55.70 and ꢁ51.99 and N12–
C5–C4–C3 = 51.26°, 52.43° and 54.81° by B3LYP, HF and XRD,
respectively. In the molecular optimized structure, the semicar-
bazone analogue is nearly planar with the dihedral angle (N51–
N52–C53–N54) 11.23° (B3LYP) and 17.77° (HF) and adopts an E
configuration with respect to the C3@N51 bond.
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-200
-150
-100
-50
0
50
100
150
200
Dihedral Angle (Degree)
Fig. 1. Potential energy surface scan of PDPOSC with dihedral angle H37–C35–C3–
C4.
Vibrational analysis
The calculated C–C bond distance in the piperidine ring is in the
range 1.511–1.567 Å by HF/6-311++G(d,p) nearly coincides with
experimental value 1.550–1.56 Å [21]. The C–C mean bond lengths
of the benzene rings are 1.3949 (B3LYP) and 1.3862 Å (HF). The
computed value by HF/6-311++G(d,p) shows excellent agreement
with XRD value 1.388 Å. Literature value for C–H bond distance
The FT-IR and FT-Raman spectra of PDPOSC are shown in
Figs. S2 and S3. The observed and calculated frequencies by
B3LYP and HF levels using 6-311++G(d,p) basis set along with their
relative intensities, probable assignments and total energy dis-
tribution (TED) of the compound are summarized in Table 2 .
Fig. 2. Optimized geometry of PDPOSC with atoms numbering calculated by B3LYP/6-311++G(d,p).

192
M. Arockia doss et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
N–H vibrations
Aromatic C–H vibrations
It is stated that in amines, the N–H [23] stretching vibrations
occur in the region 3500–3300 cmꢁ1. With the above reference,
the vibrational frequency observed at 3461 cmꢁ1 in the infrared
spectrum is assigned to the –NH2 stretching mode, the correspond-
ing computed value matches at 3453 and 3509 cmꢁ1 by B3LYP and
HF, respectively (mode no.: 167). Moreover the N–H stretching
vibration appears as pure mode at the mode numbers 166 and
165 as calculated 3448 and 3421 cmꢁ1 and 3477 and 3433 cmꢁ1
by B3LYP and HF, respectively. The TED corresponding to this
vibration contributes to about 99%. The in-plane bending mode
of H–N–H is 1353 cmꢁ1 in FT-IR and 1522 cmꢁ1 in FT-Raman, these
vibrations are in line with the calculated values 1356, 1524 cmꢁ1
(mode nos: 117,132) in B3LYP level theory.
For simplicity, modes of vibrations of aromatic compounds is
considered separately as C–H or ring C–C vibrations. However, as
with any complex molecule, vibrational interactions happen and
these levels just show the predominant vibration. Substituted ben-
zenes have large number of sensitive bands, i.e., bands whose posi-
tion is significantly influenced by the mass and electronic
properties, mesomeric or inductive effect of the substituent. As
indicated in literature [29,30], in infrared spectra, most aromatic
compounds have peaks in the region 2900–3100 cmꢁ1, these are
because of the stretching vibrations of the ring C–H bands. In the
present study, the FT-IR bands identified at 3062, 3023 cmꢁ1 and
the FT-Raman 3060 cmꢁ1 are assigned to C–H stretching vibrations
of PDPOSC. In B3LYP and HF methods the value lies in the range of
3064–3026 cmꢁ1 and 3033–2997 cmꢁ1 (mode no.: 162–155),
respectively.
C@O, C@N, C–N vibrations
The FT-IR band at 1455 cmꢁ1 and the FT-Raman band 1213 cmꢁ1
are assigned to C–H in-plane bending vibrations of title molecule.
The theoretically computed frequencies for the vibrations showed
at 1469, 1466, 1442, 1426, 1419, 1300, 1297,1214 cmꢁ1 and 1503,
1497, 1467, 1455, 1452, 1328, 1323,1227 cmꢁ1 (mode nos.: 131,
130, 125, 121, 120, 109, 108, 100) by B3LYP and HF methods for
the C–H in-plane bending, respectively. A result from theoretical
wavenumber C–H out-of-plane bending vibrations of the PDPOSC
are appeared at 972, 948, 894, 827, 825, 717, 712, 688 cmꢁ1 and
995, 981, 922, 859, 844, 740, 726, 700 cmꢁ1 (mode nos: 73, 70,
64, 59, 58, 52, 51, 48) by B3LYP and HF methods, respectively.
These C–H out-of-plane bending vibrations are finding well sup-
ported by the TED values.
The C@O [24] stretching lies in the spectral range 1750–
1860 cmꢁ1 and is very intense in the infrared and moderately
active in Raman. In PDPOSC, the carbonyl stretching frequency is
observed in the high frequency region as a very strong band at
1691 cmꢁ1 in IR and medium band at 1685 cmꢁ1 in Raman spec-
trum and the same band computed by 1695/B3LYP and
1713 cmꢁ1/HF (mode no.: 137) level theory. The TED analysis
shows 72% of contribution. In 3-methyl-2,6-diphenylpiperidin-
4-ylidine semicarbazide, the carbonyl stretching frequency is
observed as a very strong band at 1695 cmꢁ1 in IR [23]. The C–N
extending wavenumber is noticeably troublesome as there are
issues in distinguishing these wavenumbers from other different
vibrations. Dhandapani et al. [23] assigned C–N stretching absorp-
tion in the region 1603 cmꢁ1 in 3-methyl-2,6-diphenylpiperidin-
4-ylidine semicarbazide. In the present work, the C–N band
observed at 1649 cmꢁ1 in FT-IR spectrum (1600 cmꢁ1 in
FT-Raman), whereas the theoretically computed value of C–N
stretching vibration is 1650 cmꢁ1/B3LYP and 1655 cmꢁ1/HF (mode
no.: 136), respectively. The B3LYP value is in concurrence with
experimental observation and its TED value 78%. In the present
investigation, the C–N bending vibration observed at 1444 and
1442 cmꢁ1 /B3LYP and 1475 and 1467 cmꢁ1/HF (mode no.: 127
and 125), respectively. In benzamide, the band observed at
1368 cmꢁ1 is assigned to C–N stretching [25], in Benzotriazole
C–C vibrations
The ring C@C and C–C stretching vibrations, known as semicir-
cle stretching usually happen in the region 1400–1625 cmꢁ1 [30–
32]. Hence in the present study, the FT-IR bands at 1578, 1024,
1002 cmꢁ1 and the FT-Raman bands at 1580, 1207, 1174, 985,
890 cmꢁ1 are assigned to C–C vibrations of PDPOSC and the
corresponding calculated values are 1581, 1208, 1179, 1024,
1004, 982, 893 cmꢁ1 and 1624, 1207, 1183, 1026, 1014, 1011,
914 cmꢁ1(mode nos.:135, 99, 96, 81, 78, 76, 63) in B3LYP and HF
level theories, respectively.
The bands observed at 616, 512, 439 cmꢁ1 in FT-IR and 590,
282 cmꢁ1 in FT-Raman spectra have been intended to C–C in-plane
and out-of-plane bending modes. The calculated bending modes
are found at 611, 589, 504, 440, 287 cmꢁ1 (mode nos: 45, 43, 37,
32, 23) in B3LYP/6-311++G(d,p) are assigned to C–C in-plane and
out-of-plane bending vibrations, respectively.
[26] the C–N stretching bands are found at 1307 and 1382 cmꢁ1
.
The theoretically computed wavenumber falls in the region
1350–1207 cmꢁ1 for PDPOSC molecule. The TED corresponding to
the vibrations is ꢂ30% mixed with the stretching vibration as
shown in Table 2.
In order to investigate the performance and vibrational
wavenumbers of title compound, the root mean square value
(RMS) was calculated between calculated wavenumbers and
observed wavenumbers (Fig. S4a and b). RMS values of wavenum-
bers were evaluated using the following expression [33].
Methyl and methylene group vibrations
PDPOSC under consideration possesses a CH3 group in the side
chain. C–H stretching in CH3 occurs at lower frequencies than
those of aromatic ring (3100–3000 cmꢁ1). The asymmetric C–H
stretching mode of CH3 is expected at 2870 cmꢁ1 [27,28]. In the
present study, the C–H asymmetric stretching vibration appears
as medium to weak bands at 2955 cmꢁ1 in FT-IR. The theoretically
predicted value by B3LYP method 2960 cmꢁ1 (mode no.: 151)
shows good concurrence with the experimental observations. The
C–H symmetric stretching vibration is seen in FT-IR at 2927,
2856 cmꢁ1 and in FT-Raman at 2930 cmꢁ1. The C–H symmetric
stretching mode predicted by B3LYP method shows the range from
2927–2870 cmꢁ1 and by HF method shows the range from 2939–
2840 cmꢁ1 (mode nos.: 149–139). These vibrations are supported
by TED values (10–84%).
rffiffiffiffiffiffiffiffiffiffiffi
n
ꢀ
ꢁ
X
2
1
RMS ¼
mci alc
ꢁ
mej xp
n ꢁ 1
i
For IR
m
m
cal = 1.00251mexp ꢁ 2.10131 (R2 = 0.99996) by DFT method
cal = 0.99739
m
exp + 18.18323 (R2 = 0.99978) by HF method
For Raman
m
m
cal = 1.00142
cal = 0.99427
m
m
exp + 2.64209 (R2 = 0.99988) by DFT method
exp + 26.6118 (R2 = 0.99971) by HF method

M. Arockia doss et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
193
Table 2
Observed and calculated wavenumbers (cmꢁ1) and TED assignments for PDPOSC.
Mode no
Observed
Scaled frequenciesa (cmꢁ1
)
Intensities
TEDP10%c
frequencies(cmꢁ1
)
FT-IR
FT-Raman
B3LYP/6-311++G(d,p) HF/6-311++G(d,p)
IR
Ramanb
1
2
13
18
11
15
0.18
0.19
20.96
100
C
s
C1-C2-N12-C3(45)
C15-C13-C5-N12(21) +
C5(20)
s
C3-C2-C4-C5(15) + sC1-N12-C4-
3
4
26
29
25
35
0.02
0.10
59.8
52.53
s
C26-C24-C1-N12(14) +
s
s
C2-C35-C38-c41(32)
C3-N51-N52-C53(12) + sC3-C2-
sC15-C13-C5-N12(24) +
C4-C5(10) +
sC1-N12-C5-C13(18)
5
6
41
47
39
45
0.61
0.93
12.63
32.88
sC15-C13-C5-N12(10) + sC26-C24-C1-N12(17)
bC2-C35-C38(11) + bC35-C38-C41(13) +
N12(11)
s
C15-C13-C5-
C2-
7
49
49
0.77
20.48
s
N51-N52-C53-N154(16) +
s
s
C3-C2-C35-C38(12) +
s
C35-C38-c41(16)
8
9
10
57
61
70
57
64
74
1.37
0.20
0.36
15.24
22.33
5.72
sN51-N52-C53-N154(23) +
C35-C38-C41-C44(14)
bC3-N51-N52(10) + sC26-C24-C1-N12(27)
sN51-N52-C53-N154(19) +
s
C1-N12-C5-C13(21) +
C
C1-
C24-C26-C25(14)
11
12
91
117
99
119
0.35
0.60
18.45
2.45
s
C3-N51-N52-C53(31) +
s
C35-C38-C41-C44(18)
bC53-N52-N51(12) + bC3-N51-N52(22) + sC35-C38-C41-
C44(10)
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
124
139
158
164
169
197
214
230
244
280
287
299
335
341
365
383
124
149
155
169
179
201
212
227
239
277
285
293
313
342
358
386
0.38
1.06
1.04
0.58
0.21
5.25
1.33
0.51
0.03
0.34
3.59
8.72
41.36
33.53
1.93
4.72
1.82
7.93
3.61
8.28
4.9
3.91
0.01
1.28
2.69
5.65
1.14
4.73
s
C38-C41-C44-C47(41) +
bC35-C38-C41(13) + C15-C13-C5-N12(10)
bC1-C24-C26(20) + C1-C2-C12-C24(15)
C3-C2-C35-C38(28)
sC2-C35-C38-c41(12)
s
C
s
165w
282w
bN52-C53-N54(16) +
bC53-N52-N51(17)
bC5-C13-C15(14) + bC1-C2-C35(12) + bC2-C1-N12(20)
bC5-C13-C15(18) + bC1-C2-C35(13)
sC27-C25-C31-C29(44)
sH48-C47-C44-C41(42) + sH50-C47-C44-C41(38)
bC41-C44-C47(14)
bC1-C24-C26(11)
sC4-C3-N51-N52(21)
bC1-C2-C35(14) +
bC1-C2-C35(13) +
CN54-H55-C53-H46(34)
bC41-C44-C47(12) + bC35-C38-C41(18) + CC35-C1-C3-
C
C
N54-H55-C53-H46(16)
N54-H55-C53-H46(16)
133.76 3.85
6.14
3.62
C2(12)
29
30
31
32
33
391
399
403
440
447
404
411
411
444
453
28.26
0.12
1.80
6.83
7.01
2.44
0.12
0.15
0.81
0.16
bC2-C3-C4(15)
sC26-C29-C27-C31(30) +
sC15-C18-C16-C20(29) +
sC15-C18-C16-C20(14) +
s
s
C27-C25-C31-C29(44)
C16-C14-C20-C18(37)
439m
512m
CC3-C13-C15-C14(15)
bN52-C53-N54(10) + bC41-C44-C47(12) + bC2-C35-
C38(12) + bC38-C41-C44(19)
34
35
36
37
38
39
40
41
452
465
485
504
518
533
549
571
466
471
490
512
529
543
558
587
95.81
2.64
1.43
1.43
9.64
25.86
35.72
24.74
1.48
0.42
0.85
1.1
0.95
1.89
0.6
sH57-N52-C53-N54(55) +
C
N54-H55-C53-H46(13)
bC13-C5-N12(15) +
bC2-C3-N51(19)
bC14-C13-C15(18)
CC5-C13-C15-C14(11)
C
C1-C24-C26-C25(14)
sH57-N52-C53-N54(19) + CH55-N54-C53-N52(41)
C
H55-N54-C53-N52(14)
3.36
bN52-C53-N54(12) +
C4-C3(20)
C
N12-C1-C5-H11(41) +
CN51-C2-
42
43
44
45
46
47
48
579
589
610
611
625
670
688
597
610
613
614
634
697
700
17.39
29.22
0.07
0.29
8.30
1.96
1.24
2.03
3.24
2.51
0.56
0.25
bN52-C53-N54(16) +
bC2-C3-N51(22)
bC26-C29-C31(46) + bC25-C27-C31(21)
bC15-C18-C20(46) + bC14-C16-C20(22)
bC2-C3-N51(10) + bC27-C31-C29(12)
C
N12-C1-C5-H11(13)
590w
676w
616w
697s
758s
42.98
42.57
C
C
N12-C1-C5-H11(31)
H17-C14-C16-C20(11) +
s
C13-C15-C20-C18(43) +
s
C15-
C27-
H43-
C18-C16-C20(14) +
sC16-C14-C20-C18(20)
49
50
51
689
708
712
704
709
726
30.59
6.76
7.42
0.47
0.26
2.32
sC24-C26-C31-C29(49) + C26-C29-C27-C31(16) + s
s
C25-C31-C29(18)
s
H36-C35-C38-H39(10) +
C41-C44-C47(15) + H43-C41-C44-H45(27)
C5-C13 (11) + bC16-C20-C18(19) + C15-C13-C18-
H19(11)
sH42-C41-C44-C47(13) + s
s
m
C
52
53
54
55
717
731
733
750
740
750
771
780
72.70
21.48
1.70
1.09
0.11
1.63
0.34
C
C
C20-C16-C18-H23(11) + bC2-C3-C4(16)
O58-H52-N54-C53(88)
sH36-C35-C38-H39(20)
16.58
C
C26-C24-C29-C30(17) +
C
C26-C24-C29-
H30(18) +
C25(12)
s
H30-C26-C29-H33(13) + C1-C24-C26-
C
56
57
776
807
789
820
5.40
5.71
4.92
2.04
bC27-C31-C29(12)
H48-C47-C44-C41(10)
s
(continued on next page)

194
M. Arockia doss et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
Table 2 (continued)
Mode no
Observed
frequencies(cmꢁ1
Scaled frequenciesa (cmꢁ1
)
Intensities
TEDP10%c
)
FT-IR
FT-Raman
B3LYP/6-311++G(d,p) HF/6-311++G(d,p)
IR
Ramanb
58
59
60
61
62
825
827
836
860
880
844
859
861
866
900
0.29
0.34
10.10
1.95
5.38
0.24
0.23
0.28
1.43
2.44
C
C
C26-C24-C29-H30(46) +
H17-C14-C16-C20(34) +
C
C
H32-C27-C25-C24(46)
C15-C13-C18-H19(45)
m
m
C2-C3 (17)
C44-C47 (17) +
m
C41-C44 (20) + bH48-C47-C44(18)
H33-C29-C31-H34(10) + sH28-
s
H30-C26-C29-H33(13) +
C25-C27-H32(11)
C4-C5 (10)
H17-C14-C16-C20(11) +
C4-C5 (28)
H17-C14-C16-C20(10) +
s
63
64
65
66
67
68
69
70
890w
893
894
901
907
928
942
944
948
914
922
931
938
955
962
980
981
4.45
0.61
8.91
4.38
26.15
12.65
0.05
1.19
4.25
0.77
1.04
0.61
1.81
0.74
0.06
0.03
m
C
m
C
C
C20-C16-C18-H23(10)
C20-C16-C18-H23(10)
C
m
s
C
N54-C53 (38) +
H30-C26-C29-H33(43) +
H17-C14-C16-C20(11) +
H22(53) + C20-C16-C18-H23(19)
H33-C29-C31-H34(47)
m
N52-C53 (17)
H28-C25-C27-H32(43)
H19-C15-C18-
945m
s
s
C
71
72
73
74
965
969
972
978
989
994
995
997
1.31
4.66
1.25
0.21
0.51
1.44
0.6
s
s
s
H17-C14-C16-H21(10) +
H17-C14-C16-H21(57) +
s
C
H33-C29-C31-H34(11)
C20-C16-C18-H23(13)
10.65
bC15-C18-C20(20) + bC16-C20-C18(19) + bC14-C16-
C20(25)
75
978
1007
2.67
7.37
bC26-C29-C31(18) + bC27-C31-C29(18) + bC25-C27-
C31(25)
76
77
78
79
985w
982
991
1004
1011
1011
1014
1014
1017
5.84
2.94
2.74
2.79
0.46
1.72
1.46
4.55
m
m
m
m
C44-C47 (34) +
N12-C1 (13)
C35-C38 (36)
C29-C31 (19) +
m
C38-C41 (22)
1002w
1024m
m
C27-C31 (24) + bH33-C29-
C31(10) + bC25-C27-C31(10)
80
81
82
83
84
85
86
87
88
89
90
91
1012
1024
1036
1054
1060
1069
1080
1084
1102
1107
1131
1135
1024
1026
1058
1061
1065
1082
1083
1094
1099
1112
1130
1134
12.51
0.67
4.31
2.37
1.4
0.35
0.26
0.75
1.47
0.13
0.92
0.9
m
m
m
m
m
m
m
m
m
C18-C20 (17) +
C44-C47 (21) +
C35-C38 (10) +
C15-C18 (12) +
C35-C38 (16) + bC25-C27-C31(21)
C2-C35 (11) + bH55-N54-C53(21)
N12-C5 (13)
mC16-C20 (22)
mC38-C41 (33) +
mC2-C35 (25)
mN12-C5 (11)
m
C41-C44 (33)
15.85
14.03
24.95
13.66
25.57
13.36
30.29
23.87
9.84
1092m
1142w
C4-C5 (18) + bC16-C20-C18(11)
N51-N52 (23)
3.24
0.76
m
C5-C13 (12) + bH8-C4-C3(15)
1.86
bH21-C16-C20(26) + bH22-C18-C20(11) + bH22-C18-
C20(33)
bH32-C27-C25(18) + bH33-C29-C31(21) + bH33-C29-
C31(37)
bH17-C14-C13(17) + bH19-C15-C18(21) + bH21-C16-
C20(10) + bH22-C18-C20(24)
bH30-C26-C29(19) + bH32-C27-C25(19) + bH33-C29-
C31(17) + bH28-C25-C27(20)
92
93
94
1137
1156
1159
1152
1171
1173
0.06
0.8
10.86
1.02
1.26
0.89
95
96
97
1167
1179
1180
1183
1183
1201
53.80
33.12
2.80
7.28
2.81
2.7
bH28-C25-C27(14)
mC1-C24 (13)
bC4-C5-N12(10) + sH9-C4-C3-C2(29) + CC5-C4-C13-
1174w
H10(12)
98
99
100
1192
1208
1214
1203
1207
1227
9.96
33.30
1.12
2.62
2.31
0.55
bH8-C4-C3(15) + bH10-C5-C13(35)
mC1-C24 (10)
bH17-C14-C13(11) + bH19-C15-C18(13) + bH30-C26-
1207m
1213m
C29(15)
101
102
103
1220
1239
1261
1238
1245
1273
5.88
9.32
4.36
0.3
1.77
0.57
bH28-C25-C27(16) +
C24-C26 (11)
bH36-C35-C38(10) + bH45-C44-C47(11) + sH42-C41-C44-
sH36-C35-C38-H39(14)
m
H46(22)
104
105
106
1269
1277
1285
1285
1297
1304
4.66
8.86
0.84
1.08
0.75
4.02
m
C16-C20 (13) +
mC13-C15 (22)
bH45-C44-C47(26)
bH39-C38-C35(12) + bH42-C41-C44(40) + bH45-C44-
C47(12)
107
108
1291
1297
1308
1323
5.30
1.14
1.21
0.55
bH10-C5-C13(13)
m
C25-C27(10) + bH17-C14-C13(10) + bH19-C15-
C18(10) + bH30-C26-C29(10) + bH28-C25-C27(12)
bH17-C14-C13(11) + bH19-C15-C18(12)
bH36-C35-C38(23) + bH39-C38-C35(19)
109
110
111
1300
1304
1306
1328
1336
1348
4.51
0.11
18.07
1.17
1.37
1.25
bH10-C5-C13(13) + sH7-C1-C24-C26(24) + sH8-C4-C3-
C2(12)
112
113
114
115
1318
1325
1334
1346
1350
1362
1375
1388
11.55
26.76
15.28
2.34
1.59
1.43
0.46
0.09
C
s
C5-C4-C13-H10 (22)
H7-C1-C24-C26(12) +
bH7-C1-C24(26) + C5-C4-C13-H10 (28)
H36-C35-C38-H40(12) + H42-C41-C44-C47(25) +
C41-C44-C47(21)
CC2-C1-C3-H6(34)
1330w
C
s
s
sH43-

M. Arockia doss et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
195
Table 2 (continued)
Mode no
Observed
frequencies(cmꢁ1
Scaled frequenciesa (cmꢁ1
)
Intensities
TEDP10%c
)
FT-IR
FT-Raman
B3LYP/6-311++G(d,p) HF/6-311++G(d,p)
IR
Ramanb
0.63
116
117
1350
1356
1396
1400
67.36
C
C2-C1-C3-H6 (14) +
C35-C38-H41(11)
N54-C53 (14) + mN52-C53 (13) + bH55-N54-H56
sH36-C35-C38-H41(10) + sH37-
1353m
169.56 0.26
m
(10) + bH55-N54-C53(12) + bN52-N53-O58(10)
118
119
120
1360
1403
1419
1407
1442
1452
9.71
148.13 1.11
6.81
2.00
0.14
bH48-C47-C44(34) + bH49-C47-C50(51)
m
m
N52-C53 (12) + bH57-N52-N51(52)
C15-C18 (12) + C14-C16 (12) + bH21-C16-
0.36
0.43
m
C20(12) + bH22-C18-C20(11) + bH23-C20-C16(24)
C26-C29(11) + C25-C27(10) + bH33-C29-
C31(10) + bH34-C31-C29(22)
121
1426
1455
m
m
122
123
124
125
1430
1431
1434
1442
1458
1461
1461
1467
9.01
24.85
0.40
4.33
3.1
bH8-C4-H9(27) + bH42-C41-H43(36) + bH45-C44-H46(22)
bH8-C4-H9(45) + bH42-C41-H43(19) + bH45-C44-H46(10)
bH39-C38-H40(40) + bH45-C45-H46(24)
bH11-N12-C1(15) + bH36-C35-H37(12) + bH39-C38-
H40(22) + bH49-C47-H50(11)
1.75
0.16
2.3
126
1443
1472
5.69
1.77
bH48-C47-H49(63) +
C47-C44-C41(11)
bH11-N12-C1(47)
bH36-C35-H37(19) + bH45-C44-H46(31) + bH49-C47-
H50(14)
sH49-C47-C44-C41(14)+) + sH50-
127
128
1444
1452
1475
1485
16.64
2.22
0.4
0.32
129
130
131
1461
1466
1469
1488
1497
1503
7.61
18.15
7.39
0.31
0.15
0.17
bH36-C35-H37(45) + bH39-C38-H40(14) + bH42-C41-
H43(12)
bH17-C14-C13(13) + bH19-C15-C18(19) + bH21-C16-
C20(17) + bH22-C18-C20(16)
bH30-C26-C29(15) + bH32-C27-C25(19) + bH33-C29-
C31(17) + bH28-C25-C27(18)
1455s
132
133
134
135
1522m
1524
1560
1563
1581
1544
1598
1601
1624
298.30 2.58
bH55-N54-H56(84)
0.74
1.99
7.98
1.08
0.8
4.08
m
m
m
C18-C20(31) +
C29-C31(19) +
C15-C18(19) +
m
m
m
C13-C15(26)+) + bC14-C16-C20(26)
C24-C26(27) + bC25-C27-C31(11)
C14-C16(16) +
1578m 1580m
1649w 1600m
m
m
C16-C20(10) + bC14-
C13-C15(11)
136
137
138
139
140
141
142
1650
1695
1733
2870
2877
2879
2887
1655
1713
1767
2840
2841
2845
2849
2.73
5.27
m
m
m
m
m
m
m
N51-C3(78) +
O58-C53(72)
C26-C29(17) +
m
N54-C53(10)
C25-C27(18) +
1691s
1685s
12.46
28.29
464.72 2.44
m
C25-C24(12)
1.63
3.18
4.25
1.06
2.1
C2-H6(72) +
C2-H6(19) +
m
m
C35-H36(26)
C35-H36(43) + mC38-H39(26)
0.56
4.96
0.93
C41-H42(43) +
C35-H36(13) +
m
m
C38-H39(27)
C38-H39(27) +
m
m
m
m
C44-H45(24) +
C44-H46(32)
C44-H45(19) +
C47-H48(18) +
m
C44-
H46(24)
143
144
145
2892
2894
2902
2855
2856
2861
55.74
13.76
12.13
2.27
2
4.58
m
m
m
C38-H39(20) +
C4-H8(18) +
C41-H42(17) +
m
C38-H39(27) +
2856m
m
C5-H10(71)
C41-H43(11) +
C47-H50(19)
m
m
m
C47-
C47-
H49(10) +
m
146
2902
2866
41.53
3.35
m
C41-H42(15) +
m
C44-H45(14) +
H49(26) +
m
C47-H50(18)
147
148
149
2907
2912
2927
2880
2881
2939
52.93
47.59
35.22
11.02
0.26
0.38
m
m
m
C4-H8(65) +
C1-H7(84)
C41-H42(21) +
mC5-H10(23)
2927m 2930m
2955w
m
C41-H43(16) +
m
m
C44-H45(26) +
C47-H50(13)
m
C44-
H46(24)
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
2942
2960
2965
2974
2996
3026
3035
3037
3043
3046
3054
3056
3064
3065
3198
3421
3448
3453
3579
2940
2965
2970
2975
2980
2997
3001
3003
3011
3013
3022
3026
3033
3048
3211
3433
3477
3509
3599
7.22
2.57
1.23
3.75
0.65
2.33
0.96
1.38
1.3
3.73
3.07
1.97
2.18
5.37
10.36
4.36
1.68
1.61
3.13
1.09
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
m
C35-H37(80) +
C47-H49(45) +
C47-H48(72) +
C38-H40(80)
C4-H9(93)
mC38-H40(10)
mC47-H50(45)
mC47-H49(13) +
49.39
43.39
41.26
22.44
11.11
0.93
2.31
9.91
6.44
25.37
30.91
20.58
17.56
5.81
3023m
C27-H32(13) +
C16-H21(26) +
C27-H32(53) +
C27-H32(10) +
C26-H30(27) +
C26-H30(15) +
C27-H32(38) +
C27-H32(20) +
C27-H32(20) +
C14-H17(87)
N12-H11(99)
N54-H55(35) +
N55-H57(95)
N54-H55(65) +
m
m
m
m
m
m
m
m
m
C25-H28(84)
C18-H22(36) +
C29-H33(31) +
C16-H21(49) +
C27-H32(24) +
C27-H32(41) +
C16-H21(13) +
C18-H22(26) +
C29-H33(28) +
mC20-H23(31)
mC31-H34(11)
mC18-H22(11)
mC31-H34(40)
mC29-H33(38)
mC20-H23(45)
mC20-H23(21)
mC31-H34(45)
3062m 3060s
3196m
2.16
33.49
18.94
82.01
m
m
N54-H56(64)
N54-H56(34)
3461s
s – strong, m – medium, w – weak.
a – Scale factor: 0.9608-B3LYP/6-311++G(d,p),0.9051-(HF/6-311++G(d,p).
b – Relative Raman intensities calculated by equation and normalized to 100.
c – m: stretching; b – in-plane bending: C – out-of-plane bending: s – torsion: TED: Total energy distribution.

196
M. Arockia doss et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
C25–C27 ? C24–C26 bonds revealed that the maximum hypercon-
jugative interaction energy E(2) in both the phenyl rings are having
lesser electron densities than bonds. The above interactions are
The RMS error of the observed Raman bands, IR bands and the
scaled wavenumbers are found to be 21.56, 22.24 (HF) and 19.98,
9.92 (B3LYP), respectively. It clearly shows that the calculated fre-
quencies by B3LYP/6-311++G(d,p) method is tally with experimen-
tal frequencies.
r
observed as an increase in electron density (ED) in C–C anti bond-
ing orbital that weakens the respective donor bonds. The
intramolecular hyperconjugative interactions are formed by the
orbital overlap between n(N) and p⁄(C–N) bond and n(N) and
p⁄(N–O) bond orbital which results in ICT causing stabilization of
the system. The strong intra-molecular hyperconjugative interac-
tion of C3-N51 from N52 of n1(N52) ? C3–N51 which increases
ED (0.19e) and that weakens the respective bonds leading to
stabilization of 121.29 kJ molꢁ1. The higher ED value with lower
E(2) energy which causes lesser interaction and hence it shifts the
vibrational frequencies from the actual frequency range. It is evi-
dent that C3–N51 (1.956 e) bond stretching vibration appears at
1650 and 1655 cmꢁ1 by B3LYP and HF, respectively (mode no.
136). These vibrations are higher from the normal C-N bond
stretching (1300 cmꢁ1) [38]. Also there is another hyper conjuga-
tive interaction observed in n1(N54) ? p⁄ C3-O58 bond, having
ED (0.30e) with a stabilization of 118.62 kJ molꢁ1. These interac-
tions are observed as an increase in electron density (ED) in C–N
and C–O anti-bonding orbitals that weakens the respective bonds.
The electron density (ED) is transferred from the n(N) to the anti-
bonding p⁄ orbital of the C–N and C–O bonds. The n2(O58) orbital
interacts with N52–C53 and C53–N54 antibonding orbital that
NBO analysis
A useful aspect of the NBO method is that it gives information
about the interactions in both filled and virtual orbital spaces that
could enhance the analysis of intra- and inter molecular interac-
tions. The second-order Fock matrix was carried out to evaluate
the donor–acceptor interactions in the NBO analysis [34]. The
interactions result 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 E(2)
associated with the delocalization i ꢁ j is estimated as
2
Fði; jÞ
Eð2Þ
¼ Eij ¼ q
D
i ej
ꢁ
ei
Where qi is the donor orbital occupancy, ei and ej are diagonal
elements and F(i, j) is the off diagonal NBO Fock matrix element.
Natural bond orbital analysis provides an efficient method for
studying intra- and intermolecular binding and interaction among
bonds, and also provides a convenient basis for investigating
charge transfer or conjugative interaction in molecular systems.
Some electron donor orbital, acceptor orbital and the interacting
stabilization energy resulted from the second-order micro-distur-
bance theory are reported [35,36]. The larger the E(2) value, the
more interaction between electron donors and electron acceptors,
i.e. the more donating tendency from electron donors to electron
acceptors and the greater the extent of conjugation of the whole
system. NBO analysis has been performed on the molecule at the
DFT/B3LYP level using 6-311++G(d,p) basis set in order to elucidate
the intramolecular, re-hybridization and delocalization of electron
density within the molecule.
leads to give stabilization energy of 103.64 and 93.93 kJ molꢁ1
,
respectively. Electron density and delocalization energy of
PDPOSC are given in Table 3.
Mulliken charge analysis
Charge distribution on a molecule has a significant influence of
the vibrational spectra. The Mulliken population analysis of
PDPOSC was done using B3LYP/6-311++G(d,p) basis set and the
data are listed in Table S2. The Mulliken atomic charges are shown
in Fig. 3.
The more positive charge on C53 (0.4869) carbon atom is due to
the highly electronegative nitrogen and oxygen attached to that
carbon atom. This is caused by the –I effect of nitrogen and oxygen
atoms. The high negative charge at O58 (–0.3947) and a positive
charge at C53, suggest that charge delocalization occurs in the
entire molecule.
The second-order perturbation theory analysis of Fock matrix in
NBO basis shows strong intramolecular hyperconjugative interac-
tions of
p
electrons. The intra-molecular hyperconjugative interac-
tions is due to the overlap between
p
(C–C) and p⁄ (C–C) orbitals,
which results in intramolecular charge transfer appearing in the
molecular system [37]. It is evident from our calculation that the
E
(2) energy of
p
C29–C31 versus p ⁄C25–C27 is about 88.16 kJ/mol,
Molecular electrostatic potential
and their electron densities are 1.66 and 0.33e, respectively.
Similarly, the
p
–
p⁄ interaction of C13–C14 ? C16–C20,
The molecular electrostatic potential (MEP) are related to the
electron density and may be a helpful descriptor in understanding
C15ꢁC18 ? C13–C14, C16ꢁC20 ? C15–C18, C24–C26 ? C29–C31,
Table 3
Second order perturbation theory analysis of Fock matrix in NBO for PDPOSC.
Type
Donor (i)
ED/e
Acceptor (j)
ED/e
E(2) (kJ/mol)
Ej-Ei (a.u.)
Fi,j (a.u.)
p
p
p
p
p
p
p
p
–
–
–
–
–
–
–
–
p⁄
r⁄
p⁄
p⁄
p⁄
p⁄
p⁄
p⁄
C13–C14
C3–N51
1.65059
1.95584
1.67350
1.97911
1.65545
1.67636
1.66446
C16–C20
C1 – C2
C13–C14
C15–C18
C29–C31
C24–C26
C24–C26
C25–C27
C1–C2
0.01720
0.05332
0.34235
0.33139
0.32464
0.33810
0.33810
0.32731
0.05332
0.03932
0.04683
0.03047
0.19208
0.29940
0.29940
0.08122
0.06546
88.07
8.12
0.28
0.66
0.29
0.28
0.28
0.29
0.29
0.28
0.62
0.63
0.77
0.78
0.29
0.41
0.41
0.65
0.69
0.069
0.032
0.069
0.069
0.069
0.070
0.067
0.069
0.066
0.064
0.093
0.074
0.084
0.094
0.098
0.116
0.114
C15–C18
C16–C20
C24–C26
C25–C27
C29–C31
85.40
87.65
88.12
87.70
82.59
88.16
36.78
32.84
58.74
36.07
121.29
112.68
118.62
103.64
93.93
n–r⁄
n–r⁄
n–r⁄
n–r⁄
n–p⁄
n–p⁄
n–p⁄
n–r⁄
n–r⁄
LP (1) N12
LP (1) N51
LP (1) N52
1.90811
1.91529
1.71725
C4–C5
C2–C3
N52–H57
C3–N51
C53–O58
C53–O58
N52–C53
C53–N54
LP (1) N54
LP (2) O58
1.79024
1.84819

M. Arockia doss et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
197
and also to explain several types of reactions in conjugated sys-
tems [42]. The total energy, energy gap and dipole moment affect
0.4
0.2
the stability of
a molecule. The conjugated molecules are
characterized by a highest occupied molecular orbital-lowest
unoccupied molecular orbital (HOMO–LUMO) separation, which
is the result of a significant degree of intermolecular charge trans-
fer (ICT) from the end-capping electron-donor to the electron defi-
cient acceptor group through pi-conjugated path. The energy gap
between the HOMO and LUMO molecular orbitals is a critical
parameter in determining molecular electrical transport properties
because it is a measure of electron conductivity. So as to evaluate
energetic behavior of the title compound, we have carried out
calculations in gas, methanol and chloroform solvents. According
to the investigation of FMO energy levels of the title compound,
we noticed that the corresponding electronic transfers happened
between HOMO and LUMO + 1 and HOMO ꢁ LUMO. 3D plots of
the HOMO and LUMO orbitals computed at TD-B3LYP/6-
311++G(d,p) level PDPOSC molecule, in gas phase, methanol and
chloroform are illustrated in Fig. 5. The positive phase is red and
the negative one is green. It is clear from the figure that, the
HOMO lying at ꢁ5.901, ꢁ5.906 and ꢁ5.870 eV in methanol, chloro-
form and gas phase, respectively and it is located mainly over the
piperidine ring and semicarbazone group. LUMO lying at ꢁ0.767,
ꢁ0.593 and ꢁ0.547 eV in methanol, chloroform and gas phase,
respectively and it is located in phenyl group attached at C1 posi-
tion of piperidone moiety. The value of energy gap between the
HOMO–LUMO is 5.134, 5.313 and 5.320 eV in methanol, chloro-
form and gas phase, respectively. The energy gap of HOMO–
LUMO explains the eventual charge transfer interactions that take
place within the molecule. Furthermore, in going from solvent
phase to gas phase, the increasing value of the energy gap makes
the molecule more stable [43].
0.0
C1 C2 C3 C4 C5 N12 C13 C14 C15 C16 C18 C20 C24 C25 C26 C27 C29 C31 C35 C38 C41 C44 C47 N51 N52 C53 N54 O58
Atoms
-0.2
-0.4
Fig. 3. The atomic charge plot of PDPOSC.
The dipole moment is another important electronic property in
a molecule. For example higher the dipole moment, the stronger
will be the intermolecular interactions. The calculated dipole
moment values are given in Table S3. Based on predicted dipole
moment values, it is found that, in going to the solvent phase from
(6.214 D in methanol) from gas phase (4.540 D), the dipole
moment value decreases (Table S3) which indicates that polarity
of solvent influences the dipole moment of the studied molecule.
The values of electronegativity, chemical hardness, softness and
electrophilicity index are also given in Table S3.
Fig. 4. Molecular electrostatic potential of PDPOSC.
sites for electrophilic and nucleophilic attacks and also hydrogen-
bonding interactions [39–41]. To predict reactive sites for elec-
trophilic and nucleophilic attack for the title molecule, MEP was
calculated by applying the DFT/B3LYP method and 6-311++G(d,p)
basis set for the optimized geometry. The negative (red) regions
of MEP were associated with electrophilic reactivity and the posi-
tive (blue) regions to nucleophilic reactivity as shown in Fig. 4.
The MEP of the N atom (N51) and oxygen (O58) of PDPOSC is
shown by red and yellow colors appearing below and on top of
molecular plane of N51and O58 atoms and that represent the high
electron region. Potential will increase with the order red < orange
and the colour code of the map is within the range between
ꢁ0.0683 a.u. (deepest red) and 0.0306 a.u. (deepest blue), where
blue indicates the strongest attraction and red indicates the stron-
gest repulsion within the molecule.
Ultraviolet spectral analysis
The electronic spectra of the title compound in methanol and
chloroform solvents were recorded and shown in Fig. S5. There is
no absorption band around 400 and 1000 nm. The absence of
absorption in the visible region in the case semicarbazone makes
them suitable candidate for NLO property. [44,45]. As seen from
Fig. S5, electronic absorption spectra showed two bands at 269.5
and 252.5 nm for chloroform at 284.0 and 245.0 nm for methanol.
Electronic absorption spectra were calculated using the TD-DFT
method based on the B3LYP/6-311++G(d,p) level optimized struc-
ture in gas phase. The calculated results are listed in Table 4 along
with the experimental absorption spectral data. For TD-DFT
calculations, the theoretical absorption bands are predicted at
272.01, 262.40 and 253.85 nm in gas phase, at 267.87, 255.69
and 251.82 nm in chloroform and 267.90, 255.65 and 252.95 nm
in methanol. The band at 284.5 nm (Chloroform) and 269.5 nm
(methanol) are assigned to n–p⁄ transition.
Analysis of frontier molecular orbitals
TD-DFT has been most widely used to compute the energy of
molecules with high accuracy and low computational cost.
Molecular orbitals and their properties like energy are very useful
to the physicists and chemists and their frontier electron density is
used for predicting the most reactive position in pi-electron system
The band at 252.5 nm (Chloroform) and 245.0 nm (methanol)
are assigned to p–
p⁄ transition. The solvent in which the absorbing
species is dissolved also has an effect on the spectrum of the spe-
cies. Peaks resulting from n–p⁄ transitions are shifted to shorter

198
M. Arockia doss et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
Fig. 5. Molecular orbitals and energies for the HOMO and LUMO in (a) gas phase, (b) methanol and (c) chloroform.
Table 4
R
Experimental absorption bands and TD-DFT calculated energy transition, visible absorption wavelengths (k) and oscillator strengths ( ) for PDPOSC.
Gas phase
Chloroform
Expt.
Methanol
Expt.
Assignment Gas phase
Major
R
R
R
Energy
transition (eV)
k (nm)
Energy
transition (eV)
k (nm)
Energy
transition (eV)
k (nm)
contributiona
4.5581
4.7251
4.8841
272.01 0.0678 4.6285
262.40 0.0140 4.8490
253.85 0.0138 4.9235
267.87 0.1245 269.50 4.6280
255.69 0.0108 252.5
251.82 0.0043
267.90 0.1161 284.0 n–p⁄
255.65 0.0066 245.0
H ? L (93%)
H ? L + 1(95%)
H ? L + 2(94%)
4.8497
4.9016
p
p
?
?
p⁄
p⁄
252.95 0.0020
aH: HOMO, L: LUMO.
Table 5
wavelengths (blue shift) with increasing solvent polarity. This
emerges from increased solvation of the lone pair, which brings
down the energy of the n orbital. Normally (but not always), the
The mean polarizability (esu), anisotropy polarizability (esu) and first
hyperpolarizability (esu) of PDPOSC.
reverse (i.e. red shift) is seen for
p–
p⁄ transitions. This is brought
NLO behavior
B3LYP
6-311++G(d,p)
HF
6-311++G(d,p)
about by attractive polarisation forces between the solvent and
absorber, which decrease the energy levels of both the excited
and unexcited states. This effect is greater for the excited state,
and so the energy difference between the excited and unexcited
states are slightly reduced – resulting in a small red shift. This
effect also influences n–p⁄ transitions but is overshadowed by
the blue shift resulting from solvation of lone pairs. The main con-
tributions of the transitions were designated with the help of
SWizard program [46]. In gas phase, the maximum absorption
wavelength corresponds to the electronic transition from the
HOMO–LUMO with 93% contribution, the transition on HOMO–
LUMO + 1 with 95% and the transition HOMO–LUMO + 2 with 94%.
Mean polarizabilty (
Anisotropy of the polarizabilty (Da)
First order polarizabilty (bo)
a
)
24.995 ꢄ 10ꢁ24
4.40614 ꢄ 10ꢁ24
6.5662 ꢄ 10ꢁ31
25.193 ꢄ 10ꢁ24
4.80778 ꢄ 10ꢁ24
6.68409 ꢄ 10ꢁ31
calculating the magnitude of the total static dipole moment (
mean polarizabilty ( tot) and mean hyperpolarizability (bo), using
the x, y, z components from Gaussian 03W output are as follows:
l),
a
l
¼ ðl2x
þ
ly2
þ
l2z Þ1=2
1
3
atot
¼
ð
axx
þ
ayy
þ
azz
Þ
Non-linear optical effects
Non-linear optical (NLO) effects arise from the interactions of
electromagnetic fields in various media to produce new fields
altered in phase, frequency, amplitude or other propagation char-
acteristics from the incident fields [47]. NLO is at the forefront of
current research because of its importance in providing the key
functions of frequency shifting, optical modulation, optical switch-
ing, optical logic and optical memory for the emerging technolo-
gies in areas such as telecommunications, signal processing and
optical interconnections [48–50]. The complete equations for
1
2
2
2
axxÞ þ6ða2xy
þ
a2yz
þ
a2xzÞꢃ1=2
pffiffiffi
D
a
¼
½ðaxx
ꢁ
ayyÞ þðayy
ꢁ
azzÞ þðazz
ꢁ
2
1=2
2
2
2
b0 ¼ ½ðbxxx þbxyy þbxzzÞ þðbyyy þbyzz þbyxxÞ þðbzzz þbzxx þbzyyÞ ꢃ
The linear polarizability (atot) and first-order hyperpolarizabil-
ity (btot) of the title compound were calculated by the B3LYP and
HF levels using 6-311++G(d,p) basis set. The calculated mean linear

M. Arockia doss et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
199
Table 6
polarizability (atot) and the mean first hyperpolarizability (btot)
The experimental and calculated 1H and 13C NMR chemical shifts (ppm) of PDPOSC.
values are 24.995 ꢄ 10ꢁ24, 25.193 ꢄ 10ꢁ24 and 6.5662 ꢄ 10ꢁ31
,
6.6884 ꢄ 10ꢁ31 in B3LYP and HF levels theories, respectively and
the values are presented in Table 5. Total hyperpolarizability of
the molecule is approximately two times greater than those of urea
[51] and 17 times greater than 3-hydroxy-2-naphthoic acid hydra-
zide [52]. Narayan et al. [53] reported hyperpolarizablities of 5-ni-
tro-2-furaldehyde semicarbazone less than that of urea. The above
results show that PDPOSC can be best material for NLO
applications.
Atom B3LYP
6-311G+(2d,p)
Experiment Atom B3LYP
6-311G+(2d,p)
Experiment
C1
C2
C3
C4
69.70
62.99
150.2
48.71
67.98
50.06
151.56
36.29
60.97
H7
H6
H8
H9
3.87
3.61
2.48
2.11
2.90
3.88
1.39
7.53
7.45
7.4
7.37
7.35
7.33
7.31
7.3
7.29
7.28
8.22
5.00
6.15
1.61
1.65
1.04
1.05
1.06
1.41
1.09
1.13
0.77
0.80
0.78
2.58
2.83
3.34
4.67
1.48
8.16
7.61
7.64
7.57
7.54
7.66
7.53
7.72
7.65
7.6
7.42
4.50
5.52
1.17
1.18
0.51
0.65
0.76
0.96
0.80
1
C5
64.98
H10
H11
H17
H19
H21
H22
H23
H28
H30
H32
H33
H34
H57
H55
H56
H36
H37
H39
H40
H42
H43
H45
H46
H49
H48
H50
C13
C14
C15
C16
C18
C20
C24
C25
C26
C27
C29
C31
C53
C35
C38
C41
C44
C47
146.33
133.27
132.45
133.38
132.51
131.52
151.29
130.57
134.9
134.04
134.29
132.76
160.18
33.29
142.54
128.48
127.83
128.7
128.05
126.71
143.21
128.62
128.3
127.89
126.81
126.63
158.07
26.94
NMR
The experimental and theoretical values for 1H and 13C NMR of
PDPOSC are given in Table 6. The NMR spectra were recorded in
CDCl3 and presented in Figs. 6 and 7. The theoretical chemical shift
values were calculated by GAIO method using B3LYP/6-
311G+(2d,p) level theory. The two downfield signals (3.88 ppm
doublet of doublet and 3.61 ppm doublet) are assigned to H10
and H7, respectively. The signal at 2.90 ppm, doublet of doublet
is due to the H9 proton. Consequently, the signals at 2.48 and
2.11 ppm are due to H6 and H8, respectively. The most downfield
singlet at 8.22 ppm is assigned to NH proton of semicarbazone
group and the two downfield signals at 6.15 and 5.0 ppm are due
to NH2 protons of semicarbazone group. The aryl protons signal,
around 7.26–7.54 ppm is a multiplet which is due to aromatic pro-
tons in phenyl ring carbons at C1 and C5. The multiplets around the
region 0.80–1.61 ppm are assigned to the methylene protons of
36.71
37.95
22.50
15.79
31.64
32.26
22.50
14.07
0.64
0.98
0.71
Fig. 6. 1H NMR spectrum of PDPOSC.

200
M. Arockia doss et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
Fig. 7. 13C NMR spectrum of PDPOSC.
Fig. 8. The linear regression between the experimental and theoretical (a) 1H and (b) 13C chemical shifts of PDPOSC.
pentyl side chain at C2. The upfield triplet at 0.77 ppm is assigned
to methyl proton of pentyl side chain.
due to neighboring electronegative N51. The signal around 67.98
and 60.97 ppm are due to benzylic carbons at C1 and C5 and the
remaining signals at 50.06 and 36.29 ppm are due to C2 and C4 car-
bons, respectively. The most downfield signal around 158.07 ppm
is assigned to C@O carbon of semicarbazone group. The predicted
chemical shift values are in good agreement with the experimental
values.
Signals of aromatic carbons were observed in the range of
126.63–143.21 ppm. The upfield signals around 14.07 ppm is
assigned to C47 and other upfield signals in the region 22.5–
32.26 ppm are assigned to four methylene carbons of pentyl side
chain at C2. The downfield signal at 151.56 ppm is assigned to C3

M. Arockia doss et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
201
Table 7
from the theoretical harmonic frequencies and listed in Table S4.
From Table S4, it can be seen that these thermodynamic functions
are increasing with temperature ranging from 100 to 1000 K due to
the fact that the molecular vibrational intensities increase with
temperature [54]. The correlation equations between heat capac-
ity, entropy, enthalpy changes and temperatures were fitted by
quadratic formulas and the corresponding fitting factors (R2) for
these thermodynamic properties are 0.9999, 0.9988 and 0.9990,
respectively. The corresponding fitting equations are as follows
and the correlation graphics are shown in Fig 9a and b.
Calculated thermodynamic parameters of PDPOSC employing HF/ B3LYP/6-
311++G(d,p).
parameter
B3LYP
6-311++G(d,p)
HF
6-311++G(d,p)
Total energy (a.u.)
ꢁ1189.04210
ꢁ1181.35579
Zero point energy (kcal molꢁ1
Rotational constants (GHz)
)
312.51490
334.34195
0.21090
0.12092
0.08890
0.20326
0.12582
0.08940
Entropy (cal molꢁ1 kꢁ1
Total
Translational
Rotational
)
187.23
43.68
36.20
180.69
43.68
36.19
Cp = 301.48 + 1.716T ꢁ 3.187 ꢄ 10ꢁ4 T2 (R2 = 0.9999)
S = 0.90103 + 1.730T ꢁ 6.66805 ꢄ 10ꢁ4 T2 (R2 = 0.9988)
H = ꢁ16.42 + 0.16555T + 5.04889 ꢄ 10ꢁ4 T2 (R2 = 0.999)
Vibrational
107.34
100.81
The above data can be used to compute other thermodynamic
energies according to the well known relationships of thermody-
namic functions and to predict directions of chemical reactions
[55].
The linear regression between the experimental and theoretical
1H and 13C NMR Chemical shifts of PDPOSC are represented in
Fig. 8a and b.
In the present study, the following linear relationships were
obtained for 13C and 1H chemical shifts.
For 13C
Conclusions
dcal = 1.0533dexp ꢁ 0.24887 (R2 = 0.99099)
For 1H;
Overall, the piperidone ring is found to adopt chair con-
formation with equatorial orientation of substituents.
Comparison of calculated and experimental vibrational spectral
data show that the B3LYP/6-311++G(d,p) method gave comparable
data, while HF/6-311++G(d,p) method gave data positively
deviated and the optimized geometrical parameters show the
lengthening of N54–H56 bond and shortening of C53–O58 bond
due to the possibility of N54–H56. . .O58 hydrogen bonding. The
NBO analysis obviously illustrates the stability of the molecular
structure that arises from conjugative interactions, charge delocal-
isation and E(2) energies confirm the occurrence of intra-molecular
charge transfer. Negative regions are associated with N51 and O58
atoms. Thus, it is predicted that the oxygen atom will be preferred
electrophilic site. Positive regions are located on the carbon atom
with a value around +0.487 a.u. indicating possible site for nucle-
ophilic attack. The electronic transitions and states were investi-
gated computationally by the application of TD-DFT theory and
show good agreement with the experimental UV–vis absorption
results. The calculated first hyperpolarizability of PDPOSC is two
times greater than that of urea and so in future can be used as
NLO material. A comparison of theoretical NMR spectra with the
corresponding experimental ones shows a good agreement.
dcal = 0.981dexp + 7.0549 (R2 = 0.99805)
Correlation coefficients of 13C NMR and 1H NMR were determined
as 0.99099 and 0.99805, respectively for PDPOSC.
Thermodynamic analysis
The thermodynamic parameters such as zero-point vibrational
energy, thermal energy, rotational constants and entropy of the
compound have also been computed by B3LYP and HF methods
with 6-311++G(d,p) basis set and are presented in Table 7. In the
present investigation, the total energy as well as the zero-point
vibrational energy of PDPOSC increases at room temperature and
different methods also presented. Among the two methods,
B3LYP/6-311++G(d,p) shows minimum total energy (ꢁ1189.0421
a.u) for the title compound.
The statistical thermodynamic functions like heat capacity (Cp),
entropy (S) and enthalpy changes (DH) for PDPOSC were obtained
Fig. 9. (a) variation of entropy and heat capacity with temperature (b) variation of enthalpy with temperature.

202
M. Arockia doss et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 189–202
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One of the authors, Dr. G. Rajarajan is thankful to UGC [F. No.
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