Synthesis, characterization and computational studies of (2E)-1-(5-chlorothiophen-2-yl)-3-(2,3,4-trimethoxyphenyl)prop-2-en-1-one
1. Synthesis, molecular structure, spectroscopic characterization
and quantum chemical calculation studies of (2E)-1-(5-chlorothiophen-
2-yl)-3-(2,3,4-trimethoxyphenyl)prop-2-en-1-one
C.S. Chidan Kumar a,b
, K. Govindarasu c,⇑
, Hoong-Kun Fun a,d
, E. Kavitha c
, Siddegowda Chandraju e,1
,
Ching Kheng Quah a
a
X-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM Penang, Malaysia
b
Department of Engineering Chemistry, Alva’s Institute of Engineering & Technology, Mijar, Moodbidri 574225, Mangalore (D.K.), Karnataka, India
c
Department of Physics (Engg.), Annamalai University, Annamalainagar 608 002, India
d
Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia
e
Department of Sugar Technology and Chemistry, Sir M. Visvesvaraya PG Center, University of Mysore, Tubinakere 571402, Karnataka, India
h i g h l i g h t s
The single crystal XRD and FT-Raman
analysis of title compound were
reported.
UV–Vis spectra were recorded and
compared with calculated values.
Thermodynamic functions also
calculated.
DFT method was used to predict the
structural and spectroscopic
parameters.
g r a p h i c a l a b s t r a c t
a r t i c l e i n f o
Article history:
Received 8 November 2014
Received in revised form 15 December 2014
Accepted 15 December 2014
Available online 29 December 2014
Keywords:
XRD
FTIR
FT-Raman
UV
NBO
NLO
a b s t r a c t
High quality single crystal of efficient novel nonlinear optical (NLO) chalcone derivative (2E)-1-(5-chlo-
rothiophen-2-yl)-3-(2,3,4-trimethoxyphenyl)prop-2-en-1-one crystal has been grown and its structure
has been characterized by Fourier Transform Infrared (4000–400 cmÀ1
), Fourier Transform Raman
(3500–50 cmÀ1
) and single-crystal X-ray diffraction techniques. The vibrational wavenumbers were com-
puted using Density Functional Theory (DFT) and are assigned with the help of potential energy distribu-
tion (PED) method. The geometrical parameters of the title compound obtained from X-ray diffraction
(XRD) studies are compared with the calculated (DFT) values using 6-31G(d,p) basis set. Stability of
the molecule, hyperconjugative interactions, charge delocalization and intramolecular hydrogen bond
has been analyzed by using natural bond orbital (NBO) analysis. Electronic structures were discussed
by Time Dependent Density Functional Theory (TD-DFT) and the relocation of the electron density was
determined. Nonlinear optical (NLO) properties were also investigated. The Time Dependent Density
Functional Theory (TD-DFT) method has been used to calculate energies, oscillator strengths of electronic
singlet–singlet transitions and the absorption wavelengths. The Higher occupied molecular orbital
(HOMO) and the Lower unoccupied molecular orbital (LUMO) analysis are used to determine the charge
http://dx.doi.org/10.1016/j.molstruc.2014.12.052
0022-2860/Published by Elsevier B.V.
⇑ Corresponding author. Tel.: +91 9659598584.
E-mail addresses: kgsphysics_2013@yahoo.in (K. Govindarasu), chandraju1@yahoo.com (S. Chandraju).
1
Additional corresponding author.
Journal of Molecular Structure 1085 (2015) 63–77
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
2. transfer within the molecule. Comprehensive theoretical and experimental structural studies on the mol-
ecule have been carried out by FT-IR, FT-Raman and Ultra Violet–visible spectrometry (UV–Vis).
Published by Elsevier B.V.
Introduction
Chalcones are important constituents of many natural products.
They are abundant in edible plants where they are considered to be
the precursors of flavonoids and isoflavonoids. There is growing
interest in the pharmacological potential of chalcones which con-
stitutes an important group of natural and synthetic products that
have been screened for a wide range of pharmacological activities
such as antibacterial [1], antitumor [2], anti-inflammatory [3],
antifungal [4] and antioxidant properties [5]. Quick development
in the field of photonics has increased the demand for new NLO
materials. The development of optical devices, such as photonic
integrated circuitry, optical data storage and optical information
processing, depends on the design of efficient NLO materials [6].
In this context, simple organic materials like chalcones can be
attractive due to their versatile design strategy, easy crystal
growth, ultrafast and large optical nonlinearities and high laser
damage resistance [7]. Chalcones readily crystallize because of
their intermolecular hydrogen bonding. The same property has
been shown to be responsible for its biological activity. However,
halogen containing chalcones are of special interest in drug design
process because of the raising importance of halogen bond contri-
bution in target recognition process. Crystal structure conforma-
tion of small molecule has always been the choice for binding
energy calculations in docking studies.
Our title molecule consists of one thiophene ring and one phe-
nyl ring; these two rings are bonded through C@C bridge. It has the
following properties; Appearance: Yellow color solid; Molecular
formula: C16H15ClO4S; Molecular weight: 338.79 g/mol. The com-
pound crystallizes in the monoclinic, space group P21/c with the
unit cell parameters a = 7.9342 (3) Å, b = 12.6490 (4) Å,
c = 15.3527 (5) Å and b = 99.8486 (°). The C@C bond of the central
enone group adopts an E configuration. Title compound consist of
two rings connected through a conjugation bridge. By substituting
suitable electron donor (OCH3) or acceptor (Cl) groups on the ends
of this conjugated structure the asymmetric electronic distribution
in either or both ground and excited states can be enhanced
leading to an increased optical nonlinearity [8].
Different research groups [9–12] have reported the synthesis of
novel thiophene chalcones. These chalcones were characterized by
IR and NMR and they were also evaluated for antimicrobial activity.
Recently we have reported our previous paper [13] Synthesis,
molecular structure, FT-IR, Raman, XRD and theoretical investiga-
tions of (2E)-1-(5-chlorothiophen-2-yl)-3-(naphthalen-2-yl)prop-
2-en-1-one. Many researchers have reported chalcones containing
sulfur either as a part of heteroaryl ring (thiophene) or as a side
chain (thiomethyl group). Tomar et al. have reported the synthesis
and antimicrobial activity of chalcones containing the 2,5-dichloro-
thiophene moiety [9]. Ranganathan et al. have reported the
synthesis and antimicrobial studies of some of the 5-chloro-2-
acetylthiophene chalcones [14]. X-ray crystal structure studies of
5-chlorothiophene chalcone analogues [15] were reported by our
research group.
With the aid of above seen literatures, it is clear that there is no
quantum mechanical study on this title molecule which has
motivated us to do a detailed quantum mechanical analysis for
understanding the vibrational modes, HOMO–LUMO and thermo-
dynamic properties of the title compound. Therefore, in the present
study, it is planned to have a combine experimental and theoretical
investigation of FT-IR, FT-Raman and UV–Vis spectra. Electronic
absorption spectra of the title compound were predicted by using
time-dependent Density Functional Theory (TD-DFT) [16–18] in
the calculation of electronic excitation energies for gas and solu-
tion phases. The optimized geometrical parameters of the title
compound has been calculated utilizing B3LYP/6-31G(d,p) basis
set, these calculated parameters were compared with XRD values.
In addition to, we have also planned to illuminate theoretical
determination of the NLO and NBO analysis of the title compound
by using Density Functional Theory (DFT) with B3LYP/6-31G(d,p)
basis set. In addition, the ionization potential, electron affinity,
electrophilicity index, chemical potential, electronegativity, hard-
ness and softness are determined.
Experimental
Instrumentation
FT-FIR spectra of the title compound were recorded by KBr pel-
let technique in the region of 4000–400 cmÀ1
with Bruker Optik
GmbH FT-IR spectrometer. The spectrum was recorded at the room
temperature, with scanning speed of 10 cmÀ1
, and spectral resolu-
tion: 4 cmÀ1
. FT-Raman spectrum of the title compound was
recorded using 1064 nm line of Nd:YAG laser as excitation wave-
length in the region 3500–50 cmÀ1
on a BRUKER RFS 27: FT-Raman
Spectrometer equipped with FT-Raman molecule accessory. The
spectral resolution was set to 2 cmÀ1
in back scattering mode.
The laser output was kept at 100 mW for the solid sample. The
ultraviolet absorption spectra of Title molecule were examined in
the range 200–800 nm using Cary 500 UV–VIS–NIR spectrometer.
The UV pattern is taken from a 10–5 M solution of DMPE, dissolved
in DMSO solvent. The FTIR and UV–Vis spectral measurements
were carried out at Saint Joseph College, Tiruchirappalli and FT-
Raman spectral measurement was carried out at Indian Institute
of Technology (IIT), Chennai, India.
X-ray crystal structure analysis
A yellow, block shaped single crystal of the title compound (I),
with dimensions of 0.84 mm  0.29 mm  0.26 mm was selected
and mounted on a Bruker APEX-II CCD diffractometer with a
fine-focus sealed tube graphite-monochromated Mo Ka radiation
(k = 0.71073 Å) at 100 K in the range of 2.6 6 h 6 32.6°. The data
were processed with SAINT and corrected for absorption using
SADABS [19]. A total of 28,936 reflections were collected, of which
2675 were independent and 2446 reflections with I 2r(I). The
structure was solved by direct method using the program SHELXTL
[20] and was refined by full-matrix least squares technique on F2
using anisotropic displacement parameters for all non-hydrogen
atoms. All the hydrogen atoms were positioned geometrically
[CAH = 0.95–98 Å] and refined using riding model with isotropic
displacement parameters set to 1.2 or 1.5 (methyl group) times
the equivalent isotropic U values of the parent carbon atoms. A
rotating group model was used for methyl groups. The final full-
matrix least squares refinement gave R = 0.048 and wR = 0.164
(w = 1/[r2
(Fo
2
) + (0.1051P)2
+ 1.0593P] where P = (Fo
2
+ 2Fc
2
)/3,
S = 1.18, (D/r)max = 0.001, Dqmax = 0.55 e ÅÀ3
and Dqmin =
À0.48 e ÅÀ3
. A summary of crystal data and parameters for struc-
ture refinement details are given in Table 1. Crystallographic data
64 C.S. Chidan Kumar et al. / Journal of Molecular Structure 1085 (2015) 63–77
3. has been deposited at the Cambridge Crystallographic Data Centre.
CCDC No: 1,023,489 contain the supplementary crystallographic
data for this paper. Copies of the data can be obtained free of
charge on application to the CCDC, 12 Union Road, Cambridge
CB2 IEZ, UK. Fax: +44 (0)1223 336033 or e-mail: deposit@ccdc.
cam.ac.uk.
Synthesis
The reagents and solvents for the synthesis were obtained from
the Aldrich Chemical Co., and were used without additional purifi-
cation. The synthesis was carried out as per the procedure reported
earlier [21–23]. 2-Acetyl-5-chlorothiophene [23] (0.01 mol) and
2,3,4-trimethoxybenzaldehyde (0.01 mol) was dissolved in 20 ml
methanol. A catalytic amount of NaOH was added to the solution
drop-wise with vigorous stirring. The reaction mixture was stirred
for about 5–6 h at room temperature. The progress of the reaction
was monitored by TLC. The formed crude products were filtered,
washed successively with distilled water and recrystallized from
ethanol to get the title chalcone. Crystals suitable for X-ray diffrac-
tion studies were obtained from acetone solution by slow evapora-
tion technique at room temperature. Melting point (390–392 K)
was determined by Stuart Scientific (UK) apparatus. The purity of
the compound was confirmed by thin layer chromatography using
Merck silica gel 60 F254 coated aluminum plates. Synthetic
scheme of (2E)-1-(5-chlorothiophen-2-yl)-3-(2,3,4-trimethoxy-
phenyl)prop-2-en-1-one is shown in Fig. 1.
Computational details
All the computations were performed using Gaussian 09 pro-
gram package [24] and Gauss View [25] was used for visualization
of the structure and simulation of the vibrational spectra. For all
the computations, the title molecule in Cs symmetry were opti-
mized using B3LYP functional in conjunction with the 6-31G(d,p)
basis set in the gas phase. Harmonic vibrational frequencies and
their corresponding vibrational intensities, scaled by 0.9608
[26,27], were also computed using the same functional and basis
set. The fundamental normal modes were assigned. Potential
energy distribution (PED) calculations were carried out by the
VEDA 4 (Vibrational Energy Distribution Analysis) as described
earlier [28]. The calculated IR spectrum, plotted using the pure
Lorentzian band shape with a band width of FWHM of 10 cmÀ1
has been compared with the experimental FT-IR spectrum and is
found to be well comparable to that of the spectral data obtained
by DFT/B3LYP method. The natural bonding orbital (NBO) calcula-
tions [29] were performed using Gaussian 09 [25] package at the
same level in order to understand various second order
interactions between the filled orbitals of one subsystem and
vacant orbitals of another subsystem, which is a measure of the
intermolecular delocalization or hyper conjugation. UV–Vis spec-
tra, electronic transitions, vertical excitation energies, absorbance
and oscillator strengths were computed with the time-dependent
DFT method. The changes in the thermodynamic functions (the
heat capacity, entropy, and enthalpy) were investigated for the dif-
ferent temperatures from the vibrational frequency calculations of
molecule. The electronic properties such as HOMO and LUMO
energies were determined by TD-DFT approach.
Prediction of Raman intensities
The Raman activities (Si) calculated by Gaussian 09 program
[25] have been converted to relative Raman intensities (IR
). The
theoretical Raman intensity (IR
), which simulates the measured
Raman spectrum, is given by the equation [30,31]:
IR
i ¼ Cðm0 À miÞ4
mÀ1
i BÀ1
i Si ð1Þ
where Bi is a temperature factor which accounts for the intensity
contribution of excited vibrational states, and is represented by
the Boltzman distribution:
Bi ¼ 1 À ðexp Àhmic=kTÞ ð2Þ
In Eq. (1) m0 is the frequency of the laser excitation line (in this
work, we have used the excitation frequency m0 = 9398.5 cmÀ1
,
which corresponds to the wavelength of 1064 nm of a Nd:YAG
laser), mi is the frequency of normal mode (cmÀ1
), while Si is the
Raman scattering activity of the normal mode Qi. Ii
R
is given in arbi-
trary units (C is a constant equal to 10À12
). In Eq. (2) h, k, c, and T are
Planck and Boltzman constants, speed of light and temperature in
Kelvin, respectively. Thus, the presented theoretical Raman intensi-
ties have been computed assuming Bi equal to 1. The theoretical
Raman spectra have been calculated by the Raint program [32].
Results and discussion
Conformational stability-PES Scan analysis
In order to investigate the possible conformations of title com-
pound, potential energy scans were performed for the dihedral
angles T(C21AO18AC15AC14) at the B3LYP/6-31G level of theory.
The scans were obtained by minimizing the potential energy in all
geometrical parameters by varying the torsion angles at a step of
10° in the range of 0–360° rotation around the bond. The variation
of potential energy as a function of dihedral angle for all the four
bonds is illustrated in Fig. 2. The optimized geometry of the mole-
cule under study is confirmed to be located at the local true min-
ima on potential energy surface, as the calculated vibrational
spectra contains no imaginary wavenumber. The conformational
energy profile shows one maxima near 180° (À1776.99 Hartree)
and one local minima (stable conformers) observed at 0° or 360°
(À1777.90 Hartree) and for T (C21AO18AC15AC14). Further
results are based on the most stable conformer of title molecule
to clarify molecular structure and assignments of vibrational
spectra.
Table 1
Crystal data and parameters for structure refinement of the title compound.
Compound (I)
CCDC 1,023,489
Molecular formula C16H15ClO4S
Molecular weight 338.79
Crystal system Monoclinic
Space group P21/c
a (Å) 7.9342 (3)
b (Å) 12.6490 (4)
c (Å) 15.3527 (5)
a (°) 90.00
b (°) 99.8486 (17)
c (°) 90.00
V (Å3
) 1518.09 (9)
Z 4
Dcalc (g cmÀ3
) 1.482
Crystal dimensions (mm) 0.84 Â 0.29 Â 0.26
l (mmÀ1
) 0.40
Radiation k (Å) 0.71073
Reflections measured 28,936
Ranges/indices (h, k, l) À9, 9; À15, 15; À18, 18
h limit (°) 2.6–32.6
Unique reflections 4675
Observed reflections (I 2r(I)) 2446
Parameters 202
Goodness of fit on F2
1.18
R1, wR2 (I P 2r(I)) 0.048, 0.164
C.S. Chidan Kumar et al. / Journal of Molecular Structure 1085 (2015) 63–77 65
4. Structural analysis
The optimized molecular structure of the compound with atom
numbering scheme adopted in the computations is shown in Fig. 3.
The molecular structure of the title compound DMPE, scheme
drawn at 50% probability displacement ellipsoid is depicted in
(XRD ORTEP diagram) Fig. 4.
Bond lengths
Some of the experimental and theoretical (optimized) geomet-
ric parameters (bond lengths, bond and dihedral angles) are listed
in Table 1. The aromatic rings of the title compound are somewhat
irregular and the spread of the CAC bond distance is 1.389–1.419 Å
(DFT), 1.380–1.412 Å (XRD) for phenyl ring and 1.372–1.420 Å
(DFT), 1.358–1.413 Å (XRD) for thiophene ring. The CACl bond
length 1.732 Å (DFT), 1.723 Å (XRD) is in agreement with the CACl
bond length given by Chidan Kumar et al. [13]. As can be seen in
Table 2a, the average bond distances calculated by DFT method
for OACaromatic (1.367 Å) and for OACmethyl (1.430 Å) for the syn-
thesized chalcone agree well with the data reported in the litera-
ture, [33]. As oxygen is more electronegative than carbon, the
electrons in the C@O bond are drawn toward the oxygen. This
means that carbonyl compounds are polar and have substantial
dipole moments. The C@O bond is short 1.223 Å (DFT)/1.234 Å
(XRD). The CAH bond length of the benzene ring is almost equal
to 1.083 Å (DFT)/0.950 Å (XRD). On the other hand, small incre-
ment occurs in methyl group CAH bond lengths are shown in
Table 2a. The CAH bond length of the thiophene ring is C3AH23/
C4AH24 = 1.083 Å by DFT, 0.950 Å by XRD for the title compound
is good agreement with reported literature [13]. From Table 2a,
in the thiophene ring C2@C3, C4@C5, C3AC4, C2AS1 and S1AC5
bond lengths have been calculated at 1.372 Å, 1.378 Å, 1.420 Å,
1.736 Å and 1.751 Å, respectively by using B3LYP method. These
values correlate very well with XRD values.
Bond angles
Analysing the bond angle of aromatic ring of title molecule, one
can observe that the geometry of the benzene ring is seen to be rel-
atively perturbed due to the presence of different substituents.
With the electron donating and withdrawing substituents on the
benzene ring, the symmetry of the ring is distorted, yielding vari-
ation in bond angles at the point of substitution and at the ortho
and meta positions as well. With the electron donating (methoxy)
NaOH Methanol/RT
O
O
OO
SCl O
S
O
Cl
O
O
O
CH3
CH3
CH3
(2E)-1-(5-chlorothiophen-2-yl)-3-(2,3,4-trimethoxyphenyl)prop-2-en-1-one
2-Acetyl-5-chlorothiophene 2,3,4-trimethoxybenzaldehyde
+
Fig. 1. Synthetic scheme of (2E)-1-(5-chlorothiophen-2-yl)-3-(2,3,4-trimethoxyphenyl)prop-2-en-1-one.
-50 0 50 100 150 200 250 300 350 400
-1778.0
-1777.8
-1777.6
-1777.4
-1777.2
-1777.0
-1776.8
-1776.6
-1776.4
RELATIVEENERGY(HARTREE)
C21-O18-C15-C14 DIHEDRAL ANGLE (º)
Fig. 2. Dihedral angle-relative energy curves of the title compound by B3LYP/6-
31G(d,p) level of theory.
66 C.S. Chidan Kumar et al. / Journal of Molecular Structure 1085 (2015) 63–77
5. substituents on the benzene ring, the symmetry of the ring is
distorted, yielding ring angles smaller than (120°) at the points
of substitution [34]. Due to the electron donating effect of methoxy
group, it is observed that the bond angles at the point of
substitution C13AC14AC15 = 119.45° (DFT)/119.4° (XRD) and
C14AC15AC16 = 120.05° (DFT)/120.0° (XRD) and C10AC16A
C15 = 121.07° (DFT)/120.7° (XRD) these bond angle values very
good agreement for reported literature data [35]. The bond angles
C2AS1AC5 and C2AC3AS1 bond angles were calculated at 90.38°
and 113.30° by DFT method observed at 90.28° and 113.72° by
XRD. These angles have been reported at 91.7° and 111.8° by
Karabacak et al. [36].
Dihedral/torsion angles
The dihedral angle between the thiophene and benzene rings is
11.01° (12) suggesting a slightly twisted conformation of the mol-
ecule. The trans configuration of the C8@C9 double bond in the
central enone group is confirmed by the C6AC8@C9AC10 torsion
angle of 178.5 (2)°. The relative conformation of the two double
bonds O7@C6 and C8@C9, is s-cisoid with a torsion angle of
O7AC6AC8AC9 is 4.9° (4) observed by XRD 0.72° calculated by
DFT method. The methoxy groups attached at C16 and C15 atoms
respectively are twisted from the mean plane of the phenyl
(C10AC12) ring which is defined by the C20AO17AC16AC10 and
C21AO18AC15AC16 torsion angles of À127.2° (2) (XRD)/111.73°
(DFT) and À120.4° (2) (XRD)/À115.6° (DFT) respectively, while
the methoxy group attached to C14 is nearly planar to the bound
benzene ring with the C22AO19AC14AC15 torsion angle of
173.5° (19) (XRD)/179.60° (DFT). Two intramolecular CAHÁ Á ÁO
hydrogen bonds (Table 2b) generate S(6) ring motifs [37] as shown
in Fig. 4. In the crystal structure, the molecules are connected into
chains in head-to-tail fashion via strong intermolecular CAHÁÁÁO
hydrogen bonds (Table 2b) extending along ac direction. Adjacent
molecules of these chains are further connected into infinite chain
extending along c axis via short OÁ Á ÁCl contacts of 3.041 Å (Fig. 5).
The molecular packing is stabilized by weak CAHÁ Á Áp interactions
(Table 2b) involving the centroid of the S1/C4AC5 thiophene ring.
The bond length and bond angles agree with the literature values
and are comparable with those reported earlier [38–42]. The title
compound crystallizes in Monoclinic space group P21/c with the
unit cell dimensions a = 7.9342 (3) Å, b = 12.6490 (4) Å,
c = 15.3527 (5) Å, V = 1518.09 (9) Å3
. B3LYP method provides satis-
factory evidence for the prediction of vibrational wavenumbers
and structural parameters.
Vibrational assignments
All the experimental and theoretical vibrational frequencies for
the synthesized compound, along with corresponding vibrational
assignments and intensities are given in Table 3. The experimental
and simulated IR and Raman spectra are depicted in Figs. 6 and 7.
Our title compound consist of 37 atoms having 105 normal modes
of vibrations and it belongs to Cs point group symmetry, all these
vibrations are distributed as 37 stretching, 34 in-plane and 34 tor-
sional vibrations. PED analysis has also been carried out. The
assignments of vibrational modes for the investigated isomers
have been provided by VEDA4. All the calculated modes are num-
bered from the largest to the smallest frequency within each fun-
damental wave number.
In order to investigate the performance of vibrational wave-
numbers of the title compound, the root mean square (RMS) value
between the calculated and observed wavenumbers were calcu-
lated. The RMS values of wavenumbers were calculated using the
following expression [43].
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
1
n À 1
Xn
i
ðvcal
i À vexp
n Þ
2
v
u
u
t
Fig. 3. Optimized molecular structure and atomic numbering of title compound.
Fig. 4. Molecular view of title compound, showing 30% probability displacement
ellipsoids and atom labeling scheme.
C.S. Chidan Kumar et al. / Journal of Molecular Structure 1085 (2015) 63–77 67
7. where n is the number of the experimental or calculated data The
RMS error of the observed IR bands is found to be 30.14 for HF
and 5.27 for DFT methods, respectively. The small differences
between experimental and calculated vibrational modes are
observed. This is due to the fact that experimental results belong
to solid phase and theoretical calculations belong to gaseous phase.
DFT vibrational unscaled wavenumbers are known to be higher
than the experimental wavenumbers partly because of the neglect
of unharmonicity and partly because of the approximate nature of
the quantum mechanical methods, they were scaled down by a uni-
form scaling factor of 0.9608 [27] and the scaled wavenumbers in
general show good agreement with experimental ones.
Benzene ring vibrations
In polysubstituted benzenes, the aromatic CH stretching modes
[44,45] absorb weakly to moderately between 3000 and
3120 cmÀ1
. In our present work the DFT calculations give bands
at 3102 and 3077 cmÀ1
are assigned aromatic CH stretching modes
with 100% and 93% contributions, respectively. The in-plane and
out-of-plane CH bending vibrations of the substituted benzene
derivatives are expected in the wavenumber region 1300–
1000 cmÀ1
and 1000–700 cmÀ1
[46]. For the title molecule CH in-
plane bending vibrations are computed at 1271 cmÀ1
and
1186 cmÀ1
by DFT method. According to literature [47], for tetra-
substituted benzenes, a band is seen in 850–840 cmÀ1
due to
out-of-plane CH deformation and in the present case this modes
appears at 784 cmÀ1
in FTIR and 895 cmÀ1
in FT-Raman spectra.
The theoretically predicted wavenumbers at 895 cmÀ1
and
780 cmÀ1
are assigned as out-of-plane CH deformation of the ben-
zene ring. The experimental values are good agreement with theo-
retical values. The aromatic carbon–carbon stretching vibration
occurs in the region 1650–1200 cmÀ1
[46]. All substituted deriva-
tives have bands in this region that vary in position and intensity
with the nature and position of substituent. In the present work,
the wavenumbers observed in the FTIR spectrum at 1576 and
1492 cmÀ1
and 1572 and 1295 cmÀ1
in the FT-Raman spectrum
are identified as carbon–carbon stretching vibrations. The com-
puted wavenumbers at 1570, 1481, 1297, 1284 and 1271 cmÀ1
are assigned as CC stretching vibrations. For the title compound
the ring breathing mode is absent in the IR spectrum and the
DFT calculations give this mode at 1006 cmÀ1
which is good agree-
ment with literature [48]. The CCC in plane bending bands always
occurs between the value 1000–600 cmÀ1
[49]. In our case CCC in
plane bending bands observed weak band at 811 and 703 cmÀ1
in
FT-Raman spectrum. They are calculated at 814 and 700 cmÀ1
by
DFT method. The computed wavenumbers at 739 and 571 cmÀ1
are identified as CCCC out-of plane bending vibrations (mode
nos.: 64 and 72).
Thiophene ring vibrations
The CH modes are somewhat more affected by the state and
environment of the molecule, especially those of CH stretchings
at 3133–3076 cmÀ1
[50]. For the present molecule, the CH stretch-
ing vibrations are observed at 3140 cmÀ1
FT-IR spectra and com-
puted at 3117 and 3101 cmÀ1
by DFT method. The observed
wavenumber 3140 cmÀ1
is shifted 23 cmÀ1
from the computed
wavenumber at 3117 cmÀ1
. This may be due to C3AH23ÁÁÁO7 inter
molecular interaction between CH group of the thiophene ring and
carbonyl group of the molecule in crystal packing (see Fig. 5).The
bond lengths C3AH23 = 0.95 Å and H23Á Á ÁO7 = 2.38 Å and
C3AO7 = 3.301 Å and bond angle C3AH23ÁÁÁO7 = 164° calculated
by XRD and are presented in Table 2b. CH stretching modes of
the thiophene ring was pure modes (mode nos.: 1 and 3), the
PED column exactly contributes to 100% for these modes. The CH
in-plane bending vibrations of thiophene usually assign in the
region of 1260–960 cmÀ1
while the CH out-of-plane bending
modes generally assign in the region of 900–680 cmÀ1
[51,52]. In
the present work, the bands are observed at 942 and 1042 cmÀ1
in FTIR and 949 and 1057 cmÀ1
in FT-Raman spectrum, have been
identified to CH in plane bending vibrations. The computed wave-
numbers for these CH in plane bending modes are 959, 1058 and
1196 cmÀ1
shows good agreement with experimental findings.
Table 2b
Hydrogen-bond geometry (Å, °).
DAHÁ Á ÁA DAH HÁ Á ÁA DÁ Á ÁA DAHÁ Á ÁA
C3AH23Á Á ÁO7i 0.95 2.38 3.301 (3) 164
C20AH29Á Á ÁO18 0.98 2.44 2.942 (3) 111
C21AH33Á Á ÁO19 0.98 2.26 2.903 (3) 122
C(20)AH(30)Á Á ÁCg(1)ii 0.98 2.90 2.88 135
Symmetry codes: (i) x, Ày + 1/2, z À 1/2; (ii) x, Ày + 1/2, z À 3/2.
Fig. 5. Crystal packing of the title compound (I) viewed along b axis, showing intermolecular CAHÁ Á ÁO hydrogen bonding interactions and OÁ Á ÁCl short contacts as dotted
lines. H atoms not involved in hydrogen bonding are omitted for clarity.
C.S. Chidan Kumar et al. / Journal of Molecular Structure 1085 (2015) 63–77 69
9. The theoretically predicted wavenumbers at 775 cmÀ1
and
860 cmÀ1
by DFT method are assigned for CH out-of-plane bend-
ing. In this compound, the CC stretching vibrations were observed
at 1418 cmÀ1
in both FTIR and FT-Raman spectrum. The predicted
values at 1523, 1417 and 1306 cmÀ1
are identified as CC stretching
vibrations. All the stretching vibrations are found in the expected
range and are in good agreement with the literature values
[50,53]. The CCC inplane bending vibrations observed at
717 cmÀ1
in FT-IR spectrum and it is also calculated at 713 and
350 cmÀ1
by DFT method. The computed wavenumbers at 543
and 259 cmÀ1
by DFT method are assigned to CCCC out-off plane
bending vibrations of the thiophene ring. The CS stretch vibrations
were observed at 711 (R), 678 (R), 656 (IR) cmÀ1
and these modes
were computed at 721 and 664 cmÀ1
. These vibrations are also
reported in the literature [52,54]. In the present work CS stretch
vibrations were observed at 703 cmÀ1
in FT-Raman spectra and
computed wavenumbers at 700 and 622 cmÀ1
by DFT method have
been assigned as CS stretching vibrations of the thiophene ring.
The in-plane CS bending vibrations observed at 717 cmÀ1
in FT-
IR spectra and 657 cmÀ1
in FT-Raman spectra and it is also com-
puted at 713 and 655 cmÀ1
by DFT method. The in-plane CS bend-
ing vibrations also correlate very well with experimental
observations. The above conclusions are in good agreement with
related compounds [55,56].
Methoxy group vibrations
The wavenumbers of the vibrational modes of the methoxy
group are known to be influenced by a variety of interesting
interaction such as electronic effects, inter molecular hydrogen
bonding [57] and Fermi resonance. Electronic effects such as back
donation and induction mainly caused by the presence of oxygen
atom adjacent to CH3 group; can shift the position of CH stretching
modes [58,59]. The CH asymmetric and symmetric stretching
vibrations appear in the range 3000–2925 cmÀ1
and 2870–
2825 cmÀ1
[60,58]. The blue-shifting of methyl stretching modes
is due to electronic effects resulting from the interaction of the
methyl group with the aromatic ring system from lone pair of oxy-
gen atoms to the antibonding r⁄
CAH) bonds [61]. In case of title
molecule, asymmetric and symmetric vibrations of CH3 group have
been calculated in the range from 3034 to 2967 cmÀ1
and 2917 to
2904 cmÀ1
respectively by B3LYP method. The CH asymmetric
stretching vibrations observed at 2973 cmÀ1
in FT-IR and
3032 cmÀ1
in FT-Raman spectrum. The CH symmetric stretching
vibration observed at 2935 cmÀ1
in FT-IR spectrum. The calculated
symmetric stretching vibrations at 2917 cmÀ1
and 2913 cmÀ1
by
DFT method is shifted by 47 cmÀ1
and 43 cmÀ1
respectively, this
may be due to C20AH29Á Á ÁO18 and C21AH33Á Á ÁO19 intra molecu-
lar hydrogen bonding systems respectively. Two bending vibra-
tions can occur within a methyl group. With methyl esters the
overlap of the regions in which methyl asymmetric deformations
are active (1460 ± 25 and 1450 ± 15 cmÀ1
) is quite strong, which
leads to many coinciding wavenumbers [44]. This is obvious, not
only for the asymmetric deformations, but also for the symmetric
deformations [44] mostly displayed in the range 1380 ± 45 cmÀ1
.
The DFT calculations give 1465, 1458, 1456, 1447, 1444, 1438
and 1433, 1421, 1396 cmÀ1
as asymmetric (scissoring type) and
Table 3 (continued)
Mode nos. Experimental wavenumbers/cmÀ1
Theoretical wavenumbers/cmÀ1
PED (P10%) with assignments
B3LYP/6-31G(d,p)
FT-IR FT-Raman Unscaled Scaled a
IIR
b
IRA
72 594 571 0.6 0.1 cCCCC (48) ben.ring
73 565 543 0.0 0.0 sHCCC (22) th.ring + cCCCC(66) th.ring
74 501w 503w 526 505 0.3 0.6 tCl11C2(21)+ dCCC (11) ben.ring
75 518 498 2.8 1.7 dCCC (52) ben.ring
76 500 481 8.3 1.0 dC14C15O18(37)
77 479 460 0.6 0.2 sC2C3C4C 5(82)
78 442w 463 445 0.9 4.6 dC6C5S1(20) + cC6C8C 9C10(30)
79 408 392 0.3 0.1 dCCC (12) ben.ring + dC20O17C16 (30)+ sCCCC (19) ben.ring
80 380vw 396 381 0.2 0.4 dC14O19C22 (19) + sCCCC (16) ben.ring
81 379 364 0.2 0.1 dC22O19C14 (14) + sCCCC (26) ben.ring
82 364 350 2.7 0.2 tCl11C12(12) + dCCC (13) th.ring
83 337 324 0.4 0.1 dC10C16O17 (51)
84 291 280 1.6 1.2 dC5C6C8 (63)
85 273w 284 273 1.5 1.2 dC15O18C 21(44)
86 269 259 0.1 0.5 cCCCC (74) th.ring
87 258 248 0.1 0.4 sH37C22O19C14 (48)
88 253 243 0.3 0.3 dC15C14O19 (12) + dC6C8C9 (15) + sH36C22O19C 14(24)
89 204w 212 204 0.5 0.7 dC9C10C16 (23) + sC6C8C9C10 (15)
90 200 192 0.0 0.2 dC15O18C21 (12) + sC5C6C8C9 (19)
91 181w 186 178 0.6 0.4 sH30C20O17C 16 (16)
92 166 159 0.0 0.1 dC14C15O18 (10) + sH32C21O18C15 (80)
93 156 150 0.0 0.3 sH31C20O17C16 (65)
94 146 140 0.0 0.3 dC6C8C 9(42)
95 135 129 0.2 0.7 sC5C6C8C9 (58)
96 122 118 0.1 0.1 dC8C9C10 (36)
97 116 111 0.3 0.5 dC5C6C 8(12) + sCCCC (10) ben.ring + sC10C16O17C 20(16)
98 101 97 0.2 0.1 sC5C6C8C9 (70)
99 81w 82 78 0.8 1.2 sC10C14O17C20 (58)
100 74 71 0.2 0.4 sC10C16O17C20 (37) + cO18C15C14C10(33)
101 56 53 0.1 0.3 sC6C8C9C10 (58)
102 39 38 0.3 1.3 dC5C8C 10(34) + sC14C15O18C21 (34)
103 32 30 0.2 0.7 dCCC (26) + sCCOC (37)
104 27w 26 25 0.1 5.5 sC5C4C3C 2(74)
105 14 13 0.1 2.9 sCCCC (81)
m – stretching; d – in-plane bending; c – out-of-plane bending; s – torsion; q – rocking; w – weak; s – strong; vs – very strong; vw – very weak.
A
IIR – IR Intensity (K mmolÀ1
).
b
IRa – Raman intensity (Arb units) (intensity normalized to 100%).
C.S. Chidan Kumar et al. / Journal of Molecular Structure 1085 (2015) 63–77 71
10. symmetric (butterfly type) CH3 deformations for the title
compound. Experimentally CH3 asymmetric deformation vibration
is observed at 1460 cmÀ1
in the IR spectrum. The observed wave-
number at 1449 cmÀ1
in FT-IR and 1449 cmÀ1
by DFT method have
been identified as twisting type deformation of the CH3 group. The
methyl rocking wavenumbers are expected in the regions [44]
1100 ± 95 and 1080 ± 80 cmÀ1
. The bands calculated at 1162 and
1127 cmÀ1
and observed at 1126 cmÀ1
(Raman) are assigned as
rocking modes of the methyl groups. The theoretically predicted
wavenumber at 1129 cmÀ1
by DFT method have been identified
as wagging mode of the methyl group. A methoxy group attached
to an aromatic ring give #s CAOAC in the range 1310–1110 cmÀ1
and #as CAOAC in the range [44,58] 1050–1010 cmÀ1
. In our pres-
ent work #s CAOAC vibrations calculated wavenumbers at 1212,
1186 cmÀ1
by DFT method. The #as CAOAC vibrations observed
medium FTIR band at 1095 cmÀ1
and calculated at 1093, 1006
and 891 cmÀ1
by DFT method. Klimentova et al. [62] reported
the asymmetric and symmetric CAOAC stretching vibrations in
the range, 1214–1196 cmÀ1
and 1093–1097 cmÀ1
.
Carbonyl vibrations
The wavenumber of the C@O stretch due to carbonyl group
mainly depends on the bond strength, which in turn depends upon
inductive, conjugative, steric effects and lone pair of electron on
oxygen. C@O stretching vibration is expected in the range 1715–
1600 cmÀ1
[44]. In the present case very strong C@O experimental
band is observed at 1638 cmÀ1
in the IR spectrum 1656 cmÀ1
in
FT-Raman spectrum and the theoretically calculated values are
1654 cmÀ1
(DFT). The observed band 703 cmÀ1
in Raman spectrum
can be assigned to the carbonyl group wagging mode. This is in
agreement with the literature data [54]. The predicted value at
700 cmÀ1
is in good agreement with experimental data. The out-
of-plane C@O deformations are expected in the regions
595 ± 85 cmÀ1
, respectively [44]. These bands are assigned at
823 cmÀ1
in the IR spectrum and at 834 cmÀ1
by DFT.
Other vibrations
According to Socrates [47] the C@C stretching is expected
around 1600 cmÀ1
when conjugated with C@O group. For the title
compound, the bands observed at 1576 cmÀ1
in the IR spectrum
and at 1572 cmÀ1
in FT-Raman spectrum and at 1570 cmÀ1
theo-
retically are assigned as enone group C@C stretching mode. The
C@C in-plane bending band of enone group were assigned in our
previous work [13] at 553 (R), 552 (IR) cmÀ1
whereas the out-of-
plane bending modes of enone group were assigned at 464 (R),
447 (IR) cmÀ1
. In our present work C@C out-of-plane bending
vibrations are observed at 442 cmÀ1
in FT-Raman spectrum and
445 cmÀ1
. The calculated wavenumber at 622 cmÀ1
by DFT method
have been identified as in-plane bending vibration of enone group.
The IR and Raman bands at 505 and 516 cmÀ1
correspond to CCl
stretching mode which corresponds to the literature data [63].
For our title molecule CCl stretching vibrations are observed at
501 cmÀ1
in FTIR spectra and 503 cmÀ1
in FT-Raman spectrum
and calculated wavenumber at 505 cmÀ1
by DFT method. Vibra-
tional modes in the low wavenumber region of the spectrum con-
tain contributions of several internal coordinates and their
assignment is a reduction approximation to one of two of the inter-
nal coordinates. All other vibrations are collected in Table 3.
4000 3500 3000 2500 2000 1500 1000 500
100
80
60
40
20
0
480
665
772
834
934
9881034
1095
12111241
1295
1418
1480
1572
1656
2917
30023032
3101
B3LYP/6-31G(d,p)
4000 3500 3000 2500 2000 1500 1000 500
0
10
20
30
40
50
60
70
80
90
100
3885
3782
3662
3271
3140
3069
29732935
2834
2581
2398
21062057
1992
1816
1727
1638
1576
149214601418
1258
109510421015979942
823784
717689
632
501
Wavenumber (cm-1
)
Experimental
Transmission(%)IRintensity(arb.units)
Fig. 6. Comparison of theoretical B3LYP/6-31G(d,p) and experimental FT-IR spectra
for title compound.
3500 3000 2500 2000 1500 1000 500 0
0.0
0.2
0.4
0.6
0.8
1.0
27
81
181204
273
380
442
503
657703
811
895
949988
1057
11261157
1241
1295
14181449
1572
1656
3032
Ramanintensity(arb.units)
Experimental
3500 3000 2500 2000 1500 1000 500 0
0.0
0.5
1.0
1.5
2.0
2.5
30983071
3003
2940
1638
1572
14631424
1302125812231183
1098
975
830
724680
521491458425
70
Ramanintensity(arb.units)
Wavenumber (cm-1
)
Wavenumber (cm-1
)
B3lyp/6-31G(d,p)
Fig. 7. Comparison of theoretical B3LYP/6-31G(d,p) and experimental FT-Raman
spectra for title compound.
72 C.S. Chidan Kumar et al. / Journal of Molecular Structure 1085 (2015) 63–77
11. Natural bond orbital (NBO) analysis
The natural bond orbital (NBO) calculations were performed
using NBO 3.1 program [29] as implemented in the Gaussian 09
package at the DFT level in order to understand various second
order interactions between the filled orbital of one subsystem
and vacant orbital of another subsystem, which is a measure of
the intermolecular delocalization or hyper-conjugation. In the
NBO analysis, the electronic wave functions are interpreted in
terms of a set of Lewis and a set of non-Lewis localized orbital
[64]. For each donor (i) and acceptor (j), the stabilization energy
E(2) associated with the delocalization i ? j is estimated as
E2 ¼ DEij ¼ qi
Fði; jÞ
2
ej À ei
Some electron donor orbital, acceptor orbital and the interacting
stabilization energy resulted from the second-order-micro distur-
bance theory, 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 reported [65,66]. In NBO analysis large E(2) value shows
the intensive interaction between electron-donors and electron-
acceptors and greater the extent of conjugation of the whole sys-
tem, the possible intensive interactions are given in Table 4. The
second-order perturbation theory analysis of Fock matrix in NBO
basis shows strong intra-molecular hyper-conjugative interactions
of electrons. The intra-molecular hyper-conjugative interactions
(C20AH29Á Á ÁO18) are formed by the orbital overlap between LP
(1)O18 ? r⁄
(C20AH29) bond orbital which results in ICT causing
stabilization of the system, resulting stabilization energy of about
0.63 kJ molÀ1
. Another intra-molecular hyper-conjugative
(C20AH29Á Á ÁO18) interactions are formed by the orbital overlap
between O19 and r⁄
(C21AH33) bond orbital which results in ICT
causing stabilization of the system, resulting stabilization energy
of about 5.36 kJ molÀ1
. The intra molecular hyperconjugative inter-
action of (C2AC3) ? p⁄
(C4AC5) which increases ED (0.336 e) that
weakens the respective bonds leading to stabilization of
15.37 kJ molÀ1
. The intra-molecular hyper-conjugative interaction
between lone pair electron of Cl1 ? p⁄
(C2AC3) which increases
ED (1.959e) that weakens the respective bonds leading to stabiliza-
tion of 13.98 kJ molÀ1
. The interaction between lone pair LP(2)O7
with r⁄
(C6AC8) and r⁄
(C5AC6) results in a stabilization energy
of 19.10 and 9.04 kJ molÀ1
respectively. The important interactions
in the title molecule having p⁄
(C2AC3) ? p⁄
(C4AC5) with that of
antibonding results the stabilization of 135.92 kJ molÀ1
. The hyper-
conjugative interaction between antibonding of p⁄
(-
C10AC12) ? p⁄
(C8AC9) resulting stabilization energy of about
108.23 kJ molÀ1
. The maximum energies occurs from p⁄
(C13AC14)
to antibonding p⁄
(C10AC12) with delocalization energy
259.93 kJ molÀ1
. The increased electron density at the oxygen, chlo-
rine atoms leads to the elongation of respective bond length and a
lowering of the corresponding stretching wavenumber. The elec-
tron density (ED) is transferred from the n(Cl) to the anti-bonding
p⁄
orbital of the CAC, n(O) to r⁄
(CAC), p⁄
(CAC) explaining both
the elongation and the red shift [67]. The CACl, C@O, OACH3
stretching modes can be used as a good probe for evaluating the
bonding configuration around the corresponding atoms and the
electronic distribution of the benzene molecule. Hence the title
compound is stabilized by these orbital interactions (see Table 4).
Nonlinear optical properties
The nonlinear optical activity provides the key functions for fre-
quency shifting, optical modulation, optical switching and optical
logic for the developing technologies in areas such as communica-
tion, signal processing and optical interconnections. Nonlinear
optics deals with the interaction of applied electromagnetic fields
in various materials to generate new electromagnetic fields,
altered in wavenumber, phase or other physical properties [68].
Quantum chemical calculations have been shown to be useful in
the description of the relationship between the electronic structure
of the systems and its NLO response [69]. The computational
approach allows the determination of molecular NLO properties
as an inexpensive way to design molecules by analyzing their
potential before synthesis and to determine high-order hyperpo-
larizability tensors of molecules. The static polarizability (a) and
the hyper polarizability (b) and the electric dipole moment (l) of
the title compound are calculated by finite field method using
6-31G(d,p) basis set. To calculate all the electric dipole moments
and the first hyper polarizabilities for the isolated molecule, the
origin of the Cartesian coordinate system (x, y, z) = (0, 0, 0) was
chosen at own center of mass of title compound.
In discussing nonlinear optical properties, the polarization of
the molecule by an external radiation field is often approximated
as the creation of an induced dipole moment by an external electric
field. Under the weak polarization condition, we can use a Taylor
series expansion in the electric field components to demonstrate
the dipolar interaction with the external radiation electric field.
The first static hyperpolarizability (bo) and its related properties
(b, ao and Da) have been calculated using B3LYP/6-31G(d,p) level
based on finite field approach. In the presence of an applied electric
field, the energy of a system is a function of the electric field and
the first hyperpolarizability is a third rank tensor that can be
described by a 3 Â 3 Â 3 matrix. The 27 components of the 3D
matrix can be reduced to 10 components because of the Kleinman
symmetry [70]. The matrix can be given in the lower tetrahedral
format. It is obvious that the lower part of the 3 Â 3 Â 3 matrices
is a tetrahedral. The components of b are defined as the coefficients
in the Taylor series expansion of the energy in the external electric
field. When the external electric field is weak and homogeneous,
this expansion is given below:
E ¼ Eo À laFa À 1=2aabFaFb À 1=6babcFaFbFc þ . . . . . .
where Eo
is the energy of the unperturbed molecules, Fa is the field
at the origin, la, aab and babc are the components of dipole moment,
polarizability and first hyperpolarizability, respectively.
The total static dipole moment l, the mean polarizability ao, the
anisotropy of the polarizability Da and the mean first hyperpolar-
izability bo, using the x, y and z components are defined as:
Dipole moment is
l ¼ l2
x þ l2
y þ l2
z
1=2
Static polarizability is
a0 ¼ axx þ ayy þ azz
À Á
=3
Total polarizability is
Da ¼ 2À1=2
axx À ayy
À Á2
þ ayy À azz
À Á2
þ azz À axxð Þ2
þ 6a2
xz
h i1=2
First order hyperpolarizability is
b ¼ b2
x þ b2
y þ b2
z
1=2
where
bx ¼ bxxx þ bxyy þ bxzz
À Á
by ¼ byyy þ byzz þ byxx
À Á
bz ¼ bzzz þ bzxx þ bzyy
À Á
C.S. Chidan Kumar et al. / Journal of Molecular Structure 1085 (2015) 63–77 73
12. b ¼ ½ bxxx þbxyy þbxzz
À Á2
þ byyy þbyzz þbyxx
À Á2
þ bzzz þbzxx þbzyy
À Á2
Š
1=2
Since the values of the polarizabilities (a) and hyperpolarizability
(b) of the Gaussian 09 output are reported in atomic units (a.u.),
the calculated values have been converted into electrostatic units
(esu) (for a: 1 a.u. = 0.1482 Â 10À24
esu; for b: 1 a.u. = 8.639 Â
10À33
esu). The mean polarizability ao and total polarizability Da
of our title molecule are 37.2445 Â 10À24
esu and 46.6828 Â 10À24
esu respectively. The total molecular dipole moment and first order
hyperpolarizability are 2.6585 Debye and 32.21 Â 10À30
esu,
respectively and are depicted in Table 5. Total dipole moment of
title molecule is approximately two times greater than that of urea
and first order hyperpolarizability is 90 times greater than that of
urea (l and b of urea are 1.3732 Debye and 0.3728 Â 10À30
esu
[71]). This result indicates the good nonlinearity of the title
molecule.
Electronic properties
UV–Vis spectral analysis
Time dependent DFT method is able to find accurate absorption
wavelengths at a relatively small computing time which corre-
sponds to vertical electronic transitions computed on the ground
state geometry, especially in the study of solvent effect [72]; thus
TD-DFT method is used with B3LYP function and 6-31G(d,p) basis
set for vertical excitation energy of electronic spectra. On the basis
of fully optimized ground-state structure of title molecule, TD-DFT/
B3LYP/6-31G(d,p) calculations of vertical excitation energies, oscil-
lator strength and absorption wavelength have been done. These
calculations have been carried out considering the effect of
methanol and ethanol as solvents. Typically, according to Frank–
Condon principle, the maximum absorption peak (max)
corresponds in the UV–Visible spectrum to vertical excitation. Cal-
culations of the molecular orbital geometry show that the visible
Table 4
Second order perturbation theory analysis of Fock matrix in NBO basis for (2E)-1-(5-chlorothiophen-2-yl)-3-(2,3,4-trimethoxyphenyl)prop-2-en-1-one.
Donor (i) ED (i)(e) Acceptor (j) ED (j)(e) E(2)a
kJ molÀ1
E(j)–E(i)b
a.u. F(i,j)c
a.u.
p(C2AC3) 1.843 p⁄
(C4AC5) 0.336 15.37 0.31 0.065
p(C4AC5) 1.805 p⁄
(C2AC3) 0.359 15.64 0.27 0.061
p⁄
(C6AO7) 0.251 19.43 0.30 0.069
p(C8AC9) 1.833 p⁄
(C6AO7) 0.251 22.99 0.28 0.074
p⁄
(C10AC12) 0.409 10.45 0.29 0.053
p(C10AC12) 1.637 p⁄
(C8AC9) 0.125 15.29 0.30 0.064
p⁄
(C12AC13) 0.421 17.88 0.27 0.062
p⁄
(C15AC16) 0.371 22.71 0.27 0.070
p(C13AC14) 1.642 p⁄
(C10AC12) 0.409 23.28 0.29 0.075
p⁄
(C15AC16) 0.371 16.61 0.29 0.062
p(C15AC16) 1.681 p⁄
(C10AC12) 0.408 15.59 0.30 0.062
p⁄
(C13AC14) 0.421 20.01 0.28 0.073
LP (2)S1 1.613 p⁄
(C2AC3) 0.359 24.55 0.24 0.070
p⁄
(C4AC5) 0.335 21.05 0.26 0.067
LP (2)O7 1.880 r⁄
(C5AC6) 0.062 19.04 0.70 0.105
r⁄
(C6AC8) 0.057 19.10 0.71 0.106
LP (3) Cl11 1.921 p⁄
(C2AC3) 0.359 13.98 0.32 0.065
LP (2)O19 1.829 p⁄
(C13AC14) 0.421 31.76 0.34 0.099
p⁄
(C2AC3) 0.359 p⁄
(C4AC5) 0.335 135.92 0.02 0.076
p⁄
(C6AO7) 0.251 p⁄
(C8AC9) 0.125 50.39 0.02 0.072
p⁄
(C10AC12) 0.409 p⁄
(C8AC9) 0.125 108.23 0.02 0.074
p⁄
(C13AC14) 0.421 p⁄
(C10AC12) 0.409 259.93 0.01 0.082
LP (1)O18 0.019 r⁄
(C20AH29) 1.928 0.63 1.03 0.023
LP (2)O19 0.018 r⁄
(C21AH33) 1.928 5.36 0.75 0.057
LP (3) Cl11 1.959 p⁄
(C2AC3) 0.359 13.98 0.32 0.065
ED means electron density.
a
E(2) means energy of hyper conjugative interactions.
b
Energy difference between donor and acceptor i and j NBO orbitals.
c
F(i,j) is the Fock matrix element between i and j NBO orbitals.
Table 5
The electric dipole moment, polarizability and first order hyperpolarizability of (2E)-1-(5-chlorothiophen-2-yl)-3-(2,3,4-trimethoxyphenyl)prop-2-en-1-one by B3LYP/6-31G(d,p)
method.
Dipole moment, l (Debye) Polarizability a First order hyperpolarizability b
Parameter Value (DB) Parameter a.u. esu (Â10À24
) Parameter a.u. esu (Â10À33
)
lx 2.5866 axx 378.0457 56.02637 bxxx À4030.1621 À34816.6
ly À0.0368 axy À5.5801 À0.82697 bxxy À18.5949 À160.641
lz 0.6133 ayy 97.1133 14.39219 bxyy 17.0703 147.4703
l 2.6585 axz 94.6671 14.02966 byyy 6.7948 58.70028
ayz À0.8363 À0.12394 bxxz 1110.2811 9591.718
azz 278.7874 41.31629 bxyz 9.8502 85.09588
ao 251.3154 37.2445 byyz À31.7904 À274.637
Da 314.9988 46.6828 bxzz 311.4803 2690.878
byzz À8.0560 À69.5958
bzzz À631.7168 À5457.4
btot 3728.5229 32210.7093
b = (32.21 Â 1030
esu)
74 C.S. Chidan Kumar et al. / Journal of Molecular Structure 1085 (2015) 63–77
13. absorption maxima of this molecule correspond to the electron
transition between frontier orbitals such as translation from
HOMO to LUMO. The calculated absorption maxima values have
been found to be 388.29, 355.53 and 337.34 nm in DMSO solvents
and 252.50, 239.32, 243.61 nm in gas phase at B3LYP/6-31G(d,p)
method these excitations correspond to p–p⁄
transition, which is
good agreement with observed maxima values DMSO at
284.87 nm shown in Table 6. In general the occupied orbitals have
p character while unoccupied ones have pÃ
character. The transi-
tion is mainly due to the transition HOMO–LUMO that is the
p ! pÃ
transition predicted. The absorption band at (388.29 nm)
corresponds to the transition from the ground to the second
excited state in DMSO solvent. It is mainly described by one elec-
tron excitation from the highest occupied molecular orbital
(HOMO) to the lowest unoccupied molecular orbital (LUMO). This
calculation (for vertical transition) agrees well with experimentally
observed band at (284.87 nm) for DMSO solvents. The experimen-
tal UV–Visible spectrum (DMSO) of the title compound is shown in
Fig. 8.
Frontier molecular orbital analysis
The most important frontier molecular orbital (FMO) such as
highest occupied molecular orbital (HOMO) and lowest unoccu-
pied molecular orbital (LUMO) plays a crucial part in the chemical
stability of the molecule [73]. The HOMO represents the ability to
donate an electron and LUMO represents the ability of accept an
electron. The energy gap between HOMO and LUMO also
determines the chemical reactivity, optical polarizability and
chemical hardness–softness of a molecule [73]. A molecule with
a small frontier orbital gap is more polarizable and is generally
associated with a high chemical reactivity, low kinetic stability
and is also termed as soft molecule [74]. Here, four important
molecular orbitals (MOs) were examined: the second highest and
highest occupied MOs and the lowest and the second lowest unoc-
cupied MOs which are denoted as HOMOÀ1, HOMO, LUMO and
LUMO+1, respectively. The plots of highest occupied molecular
orbitals (HOMOs) and lowest unoccupied molecular orbitals
(LUMOs) are shown in Fig. 9. In order to evaluate the energetic
Table 6
Comparison of experimental and calculated absorption wavelength (k, nm), excitation
energies (E, eV) and oscillator strength (f) of (2E)-1-(5-chlorothiophen-2-yl)-3-(2,3,4-
trimethoxyphenyl)prop-2-en-1-one.
TD-DFT/B3LYP/6-31G(d,p) Experimental
k (nm) E (eV) f (a.u.) Major contributes k (nm) Abs
DMSO
388.29 3.1931 0.8864 H ? L
355.53 3.4873 0.0009 HÀ3 ? L
337.34 3.6754 0.0522 HÀ2 ? L, HÀ1 ? L 284.87 3.0187
Gas phase
373.27 3.3216 0.0016 HÀ3 ? L
362.73 3.4181 0.7721 HÀ1 ? L, H ? L
322.76 3.8414 0.0478 HÀ2 ? L, HÀ1 ? L, H ? L+2
200 300 400 500 600 700 800
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
285
Absorbance
Wavenumber (nm)
Experimental uv spectrum
Fig. 8. The UV–Visible spectrum (DMSO) of the title compound.
ELUMO+1 = -0.8145eV
ELUMO = -2.1192eV
EHOMO = -5.8389eV
EHOMO-1= 6.4335eV
∆E=3.7197eV ∆E=5.6190
Fig. 9. The atomic orbital compositions of the frontier molecular orbital for the title
compound.
Table 7
Thermodynamic properties at different temperatures at the B3LYP/6-31G(d,p) level
for (2E)-1-(5-chlorothiophen-2-yl)-3-(2,3,4-trimethoxyphenyl)prop-2-en-1-one.
T (K) S0
m (J molÀ1
KÀ1
) C0
p,m (J molÀ1
KÀ1
) DH0
m (kJ molÀ1
)
100.00 433.67 170.49 10.58
200.00 582.12 266.19 32.54
298.15 704.95 354.7 63.03
300.00 707.15 356.34 63.69
400.00 821.43 440.45 103.61
500.00 927.65 511.86 151.34
600.00 1026.29 569.92 205.54
700.00 1117.8 616.96 264.96
800.00 1202.78 655.48 328.65
900.00 1281.89 687.42 395.84
1000.00 1355.74 714.18 465.96
C.S. Chidan Kumar et al. / Journal of Molecular Structure 1085 (2015) 63–77 75
14. behavior of the title compound, the energies of four important
molecular orbitals of title compound: the second highest and high-
est occupied MO’s (HOMO and HOMOÀ1), the lowest and the sec-
ond lowest unoccupied MO’s (LUMO and LUMO+1) were calculated
using B3LYP/6-31G(d,p) and are presented in Fig. 9. It is clear from
the figure that the both HOMO and LUMO is located over the ben-
zene and thiophene rings. The calculated energy values of the
HOMO and HOMOÀ1 are À5.8389 eV and 6.4335 eV. Similarly
the LUMO and LUMO+1 energy values are À2.1192 eV and
À0.8145 eV. The energy gap between HOMO and LUMO indicates
the molecular chemical stability. In this molecule, the value of
energy separation between the HOMO and LUMO is 3.7197 eV
and HOMOÀ1 and LUMO+1 is 5.6190 eV respectively.
By using HOMO and LUMO energy values for a molecule, the
global chemical reactivity descriptors of molecules such as hard-
ness (g), chemical potential (l), softness (S), electronegativity (v)
and electrophilicity index (x) have been defined [75,76]. On the
basis of EHOMO and ELUMO, these are calculated using the below
equations.
Using Koopman’s theorem [77] for closed-shell molecules,
The hardness of the molecule is
g ¼ ðI À AÞ=2
The chemical potential of the molecule is
l ¼ ÀðI þ AÞ=2
The electro negativity of the molecule is
v ¼ ðI þ AÞ=2
The electrophilicity index of the molecule is
x ¼ l2
=2g
where A is the ionization potential and I is the electron affinity of
the molecule. I and A can be expressed through HOMO and LUMO
orbital energies as I = ÀEHOMO and A = ÀELUMO. The calculated values
of the hardness, electronegativity, chemical potential, and electro-
philicity index of our molecule in gas phase is 1.85985, 3.9705,
3.9705 and 4.2564 respectively.
Thermodynamic properties
The thermodynamic functions viz, heat capacities at constant
pressure (Cp,m), entropies (Sm) and enthalpy changes (Hm) for the
title compound were evaluated from the theoretical harmonic
frequencies obtained from B3LYP/6-31G(d,p) method in the tem-
perature range 100–1000 K and listed in Table 7, it can be observed
that these thermodynamic parameters increase with rise of tem-
perature due to the fact that the molecular vibrational intensities
increase with temperature [78]. The correlation equations between
heat capacity, entropy, enthalpy changes and temperatures are fit-
ted by quadratic formula. The correlation graphics of temperature
dependence of thermodynamic functions for title molecule is
shown in Fig. 10.
Conclusion
(2E)-1-(5-chlorothiophen-2-yl)-3-(2,3,4-trimethoxyphenyl)prop-
2-en-1-one compound was synthesized and characterized by IR,
FT-Raman, and X-ray single-crystal diffraction. The compound
crystallizes in monoclinic space group P21/c and the conformation
about the C@C bond of the central enone group is E. The crystal
structure is stabilized by two intramolecular and one intermolecu-
lar CAHÁ Á ÁO type hydrogen bonds and one CAHÁ Á Áp interaction.
The theoretical calculations carried out by DFT. The significant dif-
ferences between experimental and calculated results of IR and FT-
Raman can be explained by the existence of CAHÁ Á ÁO type intra
and intermolecular hydrogen bonds in the crystal structure. Also,
the theoretical molecular structure was determined using the
Density Functional Theory with the hybrid functional B3LYP in
combination with 6-31G(d,p) basis set, where the geometrical
parameters were compared with X-ray diffraction results, showed
a good correlation between experimental and theoretical values.
The detailed vibrational analysis of the molecule showed a good
agreement with the experimental data. Any differences observed
between the experimental and computed values may be due to
the fact that the computations were performed for a single mole-
cule in the gas phase, whereas the experimental values in the solid
phase were recorded in the presence of intermolecular interac-
tions. A computation of the first hyperpolarizability indicates that
the compound may be a good candidate as a NLO material. It is
worth to note that the compound has a large dipole moment
(2.66 Debye) and this is an essential criteria for drug-receptor
interaction. Stability of the molecule arising from hyperconjugative
interaction and charge delocalization has been analyzed using NBO
analysis. Vibrational and NBO analysis confirms the formation of
hydrogen bond by the orbital overlap between LP (1) O18 ? r⁄
(-
C20AH29) and O19 ? r⁄
(C21AH33) which results intramolecular
charge transfer (ICT), results in stabilization of the hydrogen
bonded CAHÁ Á ÁO system. The UV spectrum was measured in DMSO
solution and results are compared with theoretical results. The
energies of important MO’s and the kmax of the compound were also
determined from TD-DFT method. The calculated HOMO and
LUMO along with their plot have been presented for understanding
of charge transfer occurring within the molecule. Based on the fre-
quencies scaled and the principle of statistic thermodynamics,
thermodynamic properties ranging from 100 to 1000 K were
obtained and it is obvious that, the gradients of C0
p and S0
m to
the temperature decrease, but that of DH0
m increases, as the tem-
perature increases.
Acknowledgements
CSCK thanks to Universiti Sains Malaysia (USM) for a postdoc-
toral research fellowship. CSCK, HKF and CKQ thank Malaysian
Government and USM for Research University Individual Grant
(Synthesis, Characterization And Nonlinear Optical Properties Of
Novel Chalcone Compounds). The authors extend their apprecia-
tion to The Deanship of Scientific Research at King Saud University
for the research group project No. RGP VPP-207.
0 200 400 600 800 1000
0
200
400
600
800
1000
1200
1400
S0
m
(Jmol-1
K-1
),C0
p,m
(Jmol-1
K-1
)and
H0
m
(KJmol-1
)
Temperature (K)
(S0
m
(J mol-1
K-1
))
C0
p,m
(J mol-1
K-1
)
H0
m
(KJ mol-1
) R2
=0.989
R2
=0.961
R2
=0.979
Fig. 10. Correlation graphs of thermodynamic properties at different temperature
for title compound.
76 C.S. Chidan Kumar et al. / Journal of Molecular Structure 1085 (2015) 63–77
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Published by Elsevier B.V.
Introduction
Chalcones are important constituents of many natural products.
They are abundant in edible plants where they are considered to be
the precursors of flavonoids and isoflavonoids. There is growing
interest in the pharmacological potential of chalcones which con-
stitutes an important group of natural and synthetic products that
have been screened for a wide range of pharmacological activities
such as antibacterial [1], antitumor [2], anti-inflammatory [3],
antifungal [4] and antioxidant properties [5]. Quick development
in the field of photonics has increased the demand for new NLO
materials. The development of optical devices, such as photonic
integrated circuitry, optical data storage and optical information
processing, depends on the design of efficient NLO materials [6].
In this context, simple organic materials like chalcones can be
attractive due to their versatile design strategy, easy crystal
growth, ultrafast and large optical nonlinearities and high laser
damage resistance [7]. Chalcones readily crystallize because of
their intermolecular hydrogen bonding. The same property has
been shown to be responsible for its biological activity. However,
halogen containing chalcones are of special interest in drug design
process because of the raising importance of halogen bond contri-
bution in target recognition process. Crystal structure conforma-
tion of small molecule has always been the choice for binding
energy calculations in docking studies.
Our title molecule consists of one thiophene ring and one phe-
nyl ring; these two rings are bonded through C@C bridge. It has the
following properties; Appearance: Yellow color solid; Molecular
formula: C16H15ClO4S; Molecular weight: 338.79 g/mol. The com-
pound crystallizes in the monoclinic, space group P21/c with the
unit cell parameters a = 7.9342 (3) Å, b = 12.6490 (4) Å,
c = 15.3527 (5) Å and b = 99.8486 (°). The C@C bond of the central
enone group adopts an E configuration. Title compound consist of
two rings connected through a conjugation bridge. By substituting
suitable electron donor (OCH3) or acceptor (Cl) groups on the ends
of this conjugated structure the asymmetric electronic distribution
in either or both ground and excited states can be enhanced
leading to an increased optical nonlinearity [8].
Different research groups [9–12] have reported the synthesis of
novel thiophene chalcones. These chalcones were characterized by
IR and NMR and they were also evaluated for antimicrobial activity.
Recently we have reported our previous paper [13] Synthesis,
molecular structure, FT-IR, Raman, XRD and theoretical investiga-
tions of (2E)-1-(5-chlorothiophen-2-yl)-3-(naphthalen-2-yl)prop-
2-en-1-one. Many researchers have reported chalcones containing
sulfur either as a part of heteroaryl ring (thiophene) or as a side
chain (thiomethyl group). Tomar et al. have reported the synthesis
and antimicrobial activity of chalcones containing the 2,5-dichloro-
thiophene moiety [9]. Ranganathan et al. have reported the
synthesis and antimicrobial studies of some of the 5-chloro-2-
acetylthiophene chalcones [14]. X-ray crystal structure studies of
5-chlorothiophene chalcone analogues [15] were reported by our
research group.
With the aid of above seen literatures, it is clear that there is no
quantum mechanical study on this title molecule which has
motivated us to do a detailed quantum mechanical analysis for
understanding the vibrational modes, HOMO–LUMO and thermo-
dynamic properties of the title compound. Therefore, in the present
study, it is planned to have a combine experimental and theoretical
investigation of FT-IR, FT-Raman and UV–Vis spectra. Electronic
absorption spectra of the title compound were predicted by using
time-dependent Density Functional Theory (TD-DFT) [16–18] in
the calculation of electronic excitation energies for gas and solu-
tion phases. The optimized geometrical parameters of the title
compound has been calculated utilizing B3LYP/6-31G(d,p) basis
set, these calculated parameters were compared with XRD values.
In addition to, we have also planned to illuminate theoretical
determination of the NLO and NBO analysis of the title compound
by using Density Functional Theory (DFT) with B3LYP/6-31G(d,p)
basis set. In addition, the ionization potential, electron affinity,
electrophilicity index, chemical potential, electronegativity, hard-
ness and softness are determined.
Experimental
Instrumentation
FT-FIR spectra of the title compound were recorded by KBr pel-
let technique in the region of 4000–400 cmÀ1
with Bruker Optik
GmbH FT-IR spectrometer. The spectrum was recorded at the room
temperature, with scanning speed of 10 cmÀ1
, and spectral resolu-
tion: 4 cmÀ1
. FT-Raman spectrum of the title compound was
recorded using 1064 nm line of Nd:YAG laser as excitation wave-
length in the region 3500–50 cmÀ1
on a BRUKER RFS 27: FT-Raman
Spectrometer equipped with FT-Raman molecule accessory. The
spectral resolution was set to 2 cmÀ1
in back scattering mode.
The laser output was kept at 100 mW for the solid sample. The
ultraviolet absorption spectra of Title molecule were examined in
the range 200–800 nm using Cary 500 UV–VIS–NIR spectrometer.
The UV pattern is taken from a 10–5 M solution of DMPE, dissolved
in DMSO solvent. The FTIR and UV–Vis spectral measurements
were carried out at Saint Joseph College, Tiruchirappalli and FT-
Raman spectral measurement was carried out at Indian Institute
of Technology (IIT), Chennai, India.
X-ray crystal structure analysis
A yellow, block shaped single crystal of the title compound (I),
with dimensions of 0.84 mm  0.29 mm  0.26 mm was selected
and mounted on a Bruker APEX-II CCD diffractometer with a
fine-focus sealed tube graphite-monochromated Mo Ka radiation
(k = 0.71073 Å) at 100 K in the range of 2.6 6 h 6 32.6°. The data
were processed with SAINT and corrected for absorption using
SADABS [19]. A total of 28,936 reflections were collected, of which
2675 were independent and 2446 reflections with I 2r(I). The
structure was solved by direct method using the program SHELXTL
[20] and was refined by full-matrix least squares technique on F2
using anisotropic displacement parameters for all non-hydrogen
atoms. All the hydrogen atoms were positioned geometrically
[CAH = 0.95–98 Å] and refined using riding model with isotropic
displacement parameters set to 1.2 or 1.5 (methyl group) times
the equivalent isotropic U values of the parent carbon atoms. A
rotating group model was used for methyl groups. The final full-
matrix least squares refinement gave R = 0.048 and wR = 0.164
(w = 1/[r2
(Fo
2
) + (0.1051P)2
+ 1.0593P] where P = (Fo
2
+ 2Fc
2
)/3,
S = 1.18, (D/r)max = 0.001, Dqmax = 0.55 e ÅÀ3
and Dqmin =
À0.48 e ÅÀ3
. A summary of crystal data and parameters for struc-
ture refinement details are given in Table 1. Crystallographic data
64 C.S. Chidan Kumar et al. / Journal of Molecular Structure 1085 (2015) 63–77](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)