Vibrational, NMR and UV-Visible spectroscopic investigation, VCD and NLO studies on Benzophenone thiosemicarbazone using computational calculations

Article abstract of DOI:10.1016/j.molstruc.2016.01.046

In order to explore the unbelievable NLO property of prepared Benzophenone thiosemicarbazone (BPTSC), the experimental and theoretical investigation has been made. The theoretical calculations were made using RHF and CAM-B3LYP methods at 6-311++G(d,p) bas

Full text of DOI:10.1016/j.molstruc.2016.01.046

Accepted Manuscript
Vibrational, NMR and UV-Visible spectroscopic investigation, VCD and NLO studies
on Benzophenone thiosemicarbazone using computational calculations
N. Moorthy, Ph.D Scholar, P.C. Jobe Prabakar, S. Ramalingam, S. Periandy, K.
Parasuraman
PII:
S0022-2860(16)30046-1
10.1016/j.molstruc.2016.01.046
MOLSTR 22162
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 1 October 2015
Revised Date: 18 January 2016
Accepted Date: 18 January 2016
Please cite this article as: N. Moorthy, P.C.J. Prabakar, S. Ramalingam, S. Periandy, K. Parasuraman,
Vibrational, NMR and UV-Visible spectroscopic investigation, VCD and NLO studies on Benzophenone
thiosemicarbazone using computational calculations, Journal of Molecular Structure (2016), doi:
10.1016/j.molstruc.2016.01.046.
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Graphical Abstract
Generally, the evaluation of UV/Vis spectrum is providing the information regarding the
structure and whether the organic molecule has optical and NLO properties were enabled or not.
The calculated energy gap of the molecule was found to be in semiconducting region and their
excitation was also assigned to n → π* transition and belongs to quartz ultraviolet region. The
hyperpolarizability function of the compound was found to be higher than urea and it ensures
that the present compound possessing good NLO properties. In this present compound, NLO
mechanism was induced further more due to the presence thiosemicarbazone groups.

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Vibrational, NMR and UV-Visible spectroscopic investigation, VCD and NLO studies on
Benzophenone thiosemicarbazone using computational calculations
a
b
c*
d
e
N. Moorthy , P.C. Jobe Prabakar , S. Ramalingam , S. Periandy , K. Parasuraman
a
Ph.D Scholar, Department of Physics, T.B.M.L. College, Porayar, Tamilnadu, India.
b
Department of Physics, T.B.M.L. College, Porayar, Tamilnadu, India.
c
Department of Physics, A.V.C College, Mayiladuthurai, Tamilnadu, India.
d
Department of Physics, Tagore Govt. Arts college, Puducherry, India.
e
Department of Physics, Poompuhar College, Melaiyur, Tamilnadu, India.
Abstract
In order to explore the unbelievable NLO property of prepared Benzophenone
thiosemicarbazone (BPTSC), the experimental and theoretical investigation has been made. The
theoretical calculations were made using RHF and CAM-B3LYP methods at 6-311++G(d,p)
basis set. The title compound contains C=S ligand which helps to improve the second harmonic
generation (SHG) efficiency. The molecule has been examined in terms of the vibrational,
electronic and optical properties. The entire molecular behavior was studied by their fundamental
IR and Raman wavenumbers and was compared with the theoretical aspect. The molecular
chirality has been studied by performing vibrational circular dichroism (circularly polarized
infrared radiation). The Mulliken charge levels of the compound ensure the perturbation of
atomic charges according to the ligand. The molecular interaction of frontier orbitals emphasizes
the modification of chemical properties of the compound through the reaction path. The
enormous amount of NLO activity was induced by the Benzophenone in thiosemicarbazone. The
Gibbs free energy was evaluated at different temperature and from which the enhancement of
chemical stability was stressed. The VCD spectrum was simulated and the optical dichroism of
the compound has been analyzed.
1

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Key words: benzophenone thiosemicarbazone, perturbation, Gibbs free energy, C=S ligand,
VCD.
*
Corresponding author: ramalingam.physics@gmail.com
Tel./Fax: +91 04364 225367
1
. Introduction
The thiosemicarbazone is a biologically active compound and it is well-known in
pharmaceutical field for the fight against microbial and parasitic syndromes. The
thiosemicarbazone is analog of a semicarbazone in which the sulfur atom would be replaced the
oxygen atom. It is a key function to induce the antimicrobial activity in the compound which
normally provides higher biological activity compared to semicarbazone [1-2]. Naturally, the
multiple variety of biological implications such as antitumor, antifungal, antibacterial,
antiparasitic and antiviral properties have been obtained by their ligands and has been receiving
considerable attention due to important chemical and pharmacological properties [3-8]. On the
other hand, recent studies shown that, the symmetrical positioning of electron rich atoms such as
C, N and S in thiosemicarbazone ligand has much attention in the co-ordination chemistry since
their nonlinear optical activities [9]. Recent works [10-11] demonstrated that, the extensive
electron delocalization in the thiosemicarbazone moiety helps better NLO performance for the
free thiosemicarbazone ligands.
Simultaneously, the Benzophenone, due to the non symmetric centre of molecular structure,
it has taken excellent second order non-linear optical and birefringence effect [12-13].
Benzophenone is a potential organic NLO material with first-rate optical, electro-mechanical
properties. It has large NLO susceptibilities and short cut-off wavelengths up to deep UV region
[14] and due to its non hygroscopic nature; it is a best alternate material for urea [15-16].
Benzophenone is an aromatic ketone (diphenyl ketone) in which contains there are more number
of hydrogen bonds with high degree of symmetry. This is the main reason for inducing optical
property. After condensation reaction with thiosemicarbazide, the diphenyl ketone group (C=O)
at para position in between two phenyl ring is the main root to form imine group C=N which
leads the higher order symmetry by π-bond delocalization electron clouds and this is main source
to the compound attain high degree of incomparable NLO activity. One of the main criteria for
nonlinear optical crystals exhibits interactive in the field of SHG efficiency and great potential
2

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industrial value in applications in various fields like optoelectronic, optical frequency
conversion, high density optical data storage and optical switching, laser fusion systems modern
communication technology, optical computing, and optical information processing.
After the vigilant viewing of literature, no vibrational spectroscopic studies and quantum
chemical computational analysis on the title compound have been carried out. Therefore the
present review focuses on and discusses the important properties of Benzophenone
thiosemicarbazone compound as NLO materials have concerned much more attention for their
better NLO coefficients, vibrational and electronic, charge transfer interaction, stable physico-
chemical properties, NBO and MEP aided by HF and density functional theory (DFT)
computations.
2
. Experimental method
2
.1. Preparation of Benzophenone thiosemicarbazone
The Organic crystal of Benzophenone thiosemicarbazone was prepared by standard
procedure [10, 17]. In the hot solution of thiosemicarbazide and benzaldehyde, an appropriate
amount of methanol was added by drop by drop during thirty minutes. The mixture was
thoroughly stirred and refluxed for four hours. Then it was filtered the concentrates under
reduced pressure. The concentrate is allowed for slow evaporation at room temperature. The
crystals were collected by filtration and washed with cold ethanol and dried. The grown crystals
were purified by repeated- re crystallization. The formation of benzaldehyde thiosemicarbazone
complex was shown in Figure 1.
2
.2. Spectroscopic measurements of FT-IR, FT-Raman, NMR and UV-Visible spectra
•
•
FT-IR, FT-Raman spectra were recorded in Bruker RFS 27 spectrometer.
1
13
The H and C NMR spectral data was obtained from BRUKER 300 FT-NMR
spectrometer.
3
. Computational profile
3

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The HF and DFT quantum computational calculations of BPTSC were performed by
using Gaussian 09 program package [18]. The optimized geometry was detected by performing
the scanning process. The calculated optimized parameters by HF and CAM-B3LYP methods
with 6-311++G(d,p) level without fascinating the molecular symmetry limit were presented in
the Table 1. The fundamental harmonic vibrational frequency and vcd of the compound have
been computed by the same level. The electronic absorption spectra obtained from frontier
molecular orbitals gives an estimation of the band gap of the complex molecular system were
calculated at CAM-B3LYP/6-311++G(d,p) level to understand the intramolecular delocalization
or hyper-conjugation which exposes the details of chemical reaction path within the molecule.
1
3
1
The C and H NMR chemical shifts of BPTSC were simulated in gas and solvent phase
DMSO and chloroform) at GIAO approach at B3LYP/6-311G++(2d,p) level. The natural bond
(
orbital (NBO) analysis was performed by using Gaussian 09 program and the transitions among
different bonding and antibonding orbitals were presented. Moreover the MEP calculation has
been made using the CAM-B3LYP/6-311++G(d,p) method and their charge levels were
represented by different colors to explore that the reactive sites of the title molecule were
evaluated. The thermodynamic functions (the heat capacity, entropy, enthalpy and Gibbs free
energy) were calculated for the temperature region 100-1000K from the vibrational wavenumber
calculations of the title compound. The VCD spectrum was calculated at CAM-B3LYP/6-
3
11++G(d,p) level of calculation.
4
4
. Results and discussion
.1. Molecular geometry deformation analysis
The present molecular system; Benzophenone-thiosemicarbazone belongs to C group of
S
symmetry and consists of 31 atoms displayed in three groups. This compound contains three
hexagonal ring in which one was semi ring, made up of thiosemicarbazone group. The crystal
appearance of the present compound was presented in the Figure 2. According to the Cartesian
coordinate, the thiosemicarbazone group was placed in x axis, two benzene rings were situated in
y and z axes respectively. This view showed that, three groups of atoms about the imine group
were symmetrically dislocated in three different molecular axes. All those groups were making
semi centro symmetric molecule which will lead the molecule optically active. Normally, when
4

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the ring substituted, the entire hexagonal pattern is distorted [19]. Here, there were two benzene
rings coupled with the substitutional groups and both were linked via C of the
thiosemicarbazone. Those two rings were not only distorted and also twisted in two different
planes, in order to full fill the existence of attractive and repulsive forces between different
groups of atoms.
The fracture of the benzene rings was evidenced from the stretching bonds at the place of
substitutional groups. In the first ring, the bonds C2-C3 and C4-C5 were 0.008Ǻ elongated than
other bonds in the ring. In the second ring, C14-C16 and C15-C18 were 0.014Ǻ drawn out than
other bonds in that ring. The C-C bonds in the second ring was more distorted than first ring due
to the reason that, the first ring was 0.016Ǻ more away from the substitutional groups. Usually,
the bond length of C=N is 1.287Ǻ [20] where as in this case, that bond length was 0.006Ǻ
extended further due to the link of azine (N-N) group. The observed C-S bond length was nearly
equal to the calculated value. There was effective extension (0.010Ǻ) found in bond length N-H
of NH than NH . The bond angle (C27-N29-H31) of thiosemicarbazone group making semicircle
2
was nearly equal to the bond angle (C13-C14-C16) of top moiety of benzene ring. This view
proves one part of the substitution (thiosemicarbazone group) being formed as ring in the
molecule. The bond angle C12-N24-N25 (119.69º) also making semicircle ring. Thus, the title
molecule has number of rings which was main reason for the molecule was optically active. The
bond angle C13-C12-N24 was 5.79º less than bond angle C3-C12-N24 between two rings since
both were placed in different planes.
4
.2. Mulliken charge distribution analysis
The Benzophenone is consist of two benzene rings in which the charge level distribution is
depends upon the hexagonal ring carbons. When thiosemicarbazone is fused with
Benzophenone, the Mulliken charge levels were redistributed and positive and negative charges
were altered with respect to the weak and strong bonds. The Mulliken charge levels of the
molecule with different interactions were shown in Figure 3. The charge population was
indicated in the Table 2. Usually, the negative Mulliken populated over the highly
electronegative atoms which splits the positive charges among hydrogen atoms.
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In this case, the atom C12 was placed at the center, in order to hold up three segments of
molecular groups symmetrically. According to the orbital overlapping, most of the negative
charges were divided towards C12 atom and becomes more negative (-0.815) population
(appeared as red). This orientation of negative charges on C12 causing the connected carbons of
two phenyl rings more positive (green). Whereas N in the thiosemicarbazone chain was
populated negatively, this was less than C of two phenyl ring. This was mainly due to π-bond
electron delocalization between C and N. In the first phenyl ring, the weak interaction appeared
between CC of the ring. But in the second ring, one strong interaction was found and the rest
were weak. This was due to the high value of electronegativity of 14C (-1.00). Therefore, the
physical and chemical properties injected through the carbon in the ring. The atoms 12C (as
center), 3C, 24C and 24N were making triangle and symmetric top. The shape of molecule and
the charge level arrangement in the crystal lattice leads the high degree of optical phonon
momentum. This is the main cause for the compound was being optically active.
4
.3. Vibrational assignments
Though the molecule was composed with different symmetrical elements of groups, the
S
entire molecule positioned in different planes and belongs to C group of symmetry. The
molecule was divided in to 31 atoms and has 87 fundamental modes of vibrations were found
which were IR and Raman active and obey the mutual exclusion principle. The entire
fundamental modes split-up in to in plane and out plane vibrations which are represented by A′
and Aʺ respectively.
Г87=Ʃ(59 A′+28 Aʺ)
The observed wavenumbers along with scaled values were depicted in the Table 3 and
the equivalent FT-IR and FT-Raman spectra were described in the Figures 4 and 5 respectively.
The assigned pragmatic fundamental modes were verified along with the characteristics region of
group frequencies. The entire observed modes were controlled by their attractive and repulsive
forces existed among the bonds.
4
.3.1. C-H vibrations
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The main part of present compound was phenyl rings in which there were ten C-H bonds
appeared around the ring and both the rings were sighted in two different planes. They were
placed without any influence of substitutions in the molecule. Usually, C-H bonds in the benzene
-1
ring were being stretched in the region of 3100-3000 cm without any distortion [21-23]. If
molecule has more than three C-H bonds, the corresponding C-H vibrations will be found as
umbrella pattern with weak to medium intensity [24]. Accordingly, in this work, the C-H
stretching vibrational signals were observed at 3100, 3090, 3080, 3060, 3050, 3030, 2960, 2940,
-1
-1
2
930 and 2920 cm . In the region of 3100-3000 cm , the entire IR bands were very weak
whereas all Raman bands were strong. There were strong bands appeared below the observed
-1
region 3000 cm . From this view it was found that, some of the vibrations have much suppressed
and hold back little below the characteristic region. This was mainly due to the corresponding C-
H bonds were located nearby substitutional site.
In benzene related derivatives, the C-H in plane bending vibrations usually occurs in the
-1
region 1300-1000 cm [25]. In this case, the C-H in plane bending peaks were observed at 1095,
-1
1
090, 1080, 1070, 1040, 1030, 1020, 1000, 920 and 910 cm . Most of the bands were very weak
and the majority of the bands were found at the end of the expected region as expected. It was
important to note that, two of the peaks moved down below the characteristic region which was
due to the influence of ligand. Normally, the substituted benzene showed their out of plane
-1
bending in their region 1000-730 cm [26]. The C-H out of plane bending vibrations have been
-1
observed at 790, 780, 770, 760, 755, 750, 740, 720, 710 and 700 cm . Except three vibrational
bands, all were observed within the expected limit. Similar to the in plane vibrational bands, part
of peaks distorted and get down under the expected region. From the C-H vibrations, it was
identified that, some of the vibrational modes affected due to the composition of ligand with
those bonds. In addition to that, suppression of vibrational bands means the physical and
chemical properties of the affected elements were changed according to the dominated group of
atoms.
4
.3.2. N-H vibrations
Generally, in the amino group substituted molecule, the N-H vibrations will be the crown of
the vibrational bands and dominating other vibrations. In this molecule, three N-H bonds were
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present and their vibrations were active as expected. Regularly, hetero aromatics having an N-H
-1
group show its stretching absorption in the region 3500-3200 cm [27]. The position of
absorption of N-H vibration in the region depends upon the nature of hydrogen bonding and the
substitutional consequence [28]. Here, thiosemicarbazone contains three N-H bonds and the
corresponding stretching vibrations were found with strong intensity at 3480, 3350 and 3290
-1
cm . Because of the domination character of this group, the observed N-H stretching vibrations
have not affected and also out of three, two such vibrations were identified as asymmetric.
The amino group bending vibrations are very important since these vibrations emphasize the
mixing of other vibrations and fundamental modes control identifier. Usually, the N-H scissoring
-1
(
in plane bending vibrations) are falling in the region 1610-1630 cm , the rocking modes are
-1
assigned in the range 1100-1200 cm and the wagging and twisting (out of plane bending)
-1
vibrations are normally observed in the wavenumber region 1150-900 cm [29-30].
-1
Consequently, the in plane bending was found at 1185, 1170 and 1160 cm and the out of plane
-1
bending modes were observed at 860, 850 and 800 cm . The N-H bending vibrations should be
observed exactly within the limited region and dominate (control the fundamental modes of base
molecule) other group vibrations. But here, the N-H in plane bending was found in the expected
area whereas out of plane bending vibrations were moved away from the characteristic region of
the spectrum. Actually, it was suppressed much instead of suppress other vibrations. This is due
to the fascination of hetero nuclear bond C=S in the chain.
4
.3.3. CC vibrations
The present compound has di phenyl ring where except linkage point, there was no
attachment of ligand. In this case, six C=C and C-C stretching vibrations were to be obtained
without any distortion in the observed region. The benzene related derivatives showed
-1
vibrational absorption in the region 1650-1450 cm due to the CC stretching [31-32]. Here, the
-1
C=C stretching vibrations were found at 1590, 1570, 1500, 1460, 1450 and 1440 cm . The C-C
-1
stretching vibrations were established at 1390, 1380, 1320, 1300, 1290 and 1270 cm . The C=C
stretching vibrations have not affected due to the strong force constant while the entire C-C
stretching moved down rigorously due to the attachment with the thiocarbazone chain. The CCC
-1
in plane breathing modes appeared at 630, 620, 580, 570 and 560 cm . The corresponding out of
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-1
plane ring breathing modes observed at 540, 530, 500, 490, 465 and 460 cm . These bending
vibrational peaks absolutely inhibited well below the observed region. From these vibrations, it
was noteworthy that, except some, all the CC vibrational fundamentals distorted from their
characteristic region. This view clearly showed that, the ring vibrations get influenced by other
ligand vibrations. This means that, the chemical and optical properties of the phenyl ring was
altered in favour of thiosemicarbazone element.
The C-C stretching vibrations of CC linkage (out of the ring) were observed at 1150 and
-1
1
140 cm . These vibrational bands should be observed below the region of the ring CC
stretching region. In this case, similar trend was observed and the C was coupled with N making
imine group which also the cause of negative movement of such vibrations. The analogous in
-1
plane and out of plane bending were observed at 550 and 450 cm respectively.
4
.3.4. C=N and C-N vibrations
Usually, the heteronuclear bonds such as C=N, C-N and C=S having strong dipole
moment and force constant, therefore, their stretching vibrations appeared strongly in IR
spectrum while weak bands in Raman spectrum. So, the identification and assignment of these
vibrations is an easy task. Though, C=N bond was placed at the complicated position in the
chain, its normal degree of freedom was important to recognize the creation of imine group in
the chain which will lead to form new molecular properties. The corresponding stretching
-1
vibration is observed in the region 1600-1490 cm [33]. The stretching of C=N of this compound
-1
was identified with very strong intensity at 1600 cm in both IR and Raman spectra. This strong
appearance of the imine group ensured its presence. Another significant work is to assign C-N
vibrations since this bond link thiosemicarbazone group. For all time, the C-N stretching
-1
vibration is assigned in the region 1380 - 1160 cm [34-35]. In this work, the C-N stretching
-1
vibrations were observed at 1120 and 1110 cm . The corresponding in plane and out of plane
-1
deformations have been found at 420, 400 and 105, 100 cm respectively. The entire vibrations
fall down below the observed limit which was due to the further substitution in the ring.
4
.3.5. C=S and N-N vibrations
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The thiosemicarbazone emphasize its presence by the absorption of IR radiation in the
-1
region 1570-1395 cm due to the C=S stretching vibration [36]. In this thiosemicarbazone, the
-1
C=S stretching peak was found with medium intensity at 1490 cm and their in plane bending
-1
was observed at 320 cm . These vibrations have been found within the accessible region. Instead
of that, their peak intensity was affected by the near pressure.
The core bond of azine group was N-N and it was very important this compound since it
transfers the entire properties of thiosemicarbazone to major molecule. Generally, the azine bond
-1
N-N stretching vibration was found around 1080 cm [34]. The N-N stretching vibration was
-1
strongly observed at 1080 cm . The consequent in plane and out of plane bending modes was
-1
observed at 695 and 290 cm respectively. The acquired vibrational bands were precisely
harmonized with the literature and ensure the role of azine group in the semiconducting
properties of the compound.
4
.4. NMR confinement
In order to get the chemical information of the molecular components of the compound,
the NMR spectral data was calculated at B3LYP method with 6-311++G(d,p) level on the basis
of GIAO method and the chemical shifts of the compound are reported in ppm relative to TMS
1
13
for H and C NMR spectra which were presented in Tables 4 and the corresponding spectra
were shown in Figure 6. The carbons and hydrogens were situated in different environment with
different elements which makes the molecule complicated. The isotropic chemical shift of the
elements(C and H) usually explicated the unknown chemical properties the complicated
compound. In general, the chemical shifts of carbon is depends upon the bonded atoms and their
chemical environment in the compound. The isotropic chemical shifts in aromatic compounds
are universally observed in the region of 100-160 ppm [37]. The chemical shift corresponding to
the base and ligand group direct the reliable interpretation of chemical properties. Usually, the
chemical shift of aliphatic chain is constantly behind the aromatic compound [38]. Symmetry
also makes atoms equivalent in molecules. If group of atoms are in some identical locations
relative to a plane of symmetry in a molecule, they are equivalent [39-40].
The NMR signals are divided into domain of peaks with respect the diamagnetic
equivalence of carbon and hydrogen atoms. The observed chemical shift of carbons of the phenyl
1
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ring; C1, C2, C3, C4, C5, C6, C13, C14, C15, C16, C18 and C20 were limited in the region 130-
1
36ppm. The chemical shift of carbons in the ring was observed above 130 ppm and was quite
normal. In the case of carbon; C3 and C13, at which the ligand was substituted, the calculated
chemical shift was more than other carbons since further breaking of the proton shield. The
carbons C12 and C27 in the thiosemicarbazone chain showed high degree of chemical shift (143
and 213 ppm) which was greater than other carbons. This is mainly due to the random breaking
of proton shield by Sulphur and amine groups. Thus, the chemical properties of the ligand groups
were inserted in to the compound via such carbons.
The hydrogen atoms were existed in the molecule in three different environments upon
which the chemical shift of the atoms was classified. Here, the phenyl ring hydrogens showed
the fluctuated chemical shift. The H8, H9 and H19 were showed the higher chemical shift than
rest of others in the ring since further influence of thiosemicarbazone ligand. The hydrogens of
amine group were separated entirely and particularly, the chemical shift of H26 was more than
H30 and H31 due to the parametric synchronization of electronegative atoms in the chain. Thus,
some of the hydrogens in the ring and ligand were participated in the alternation of the chemical
properties of the compound.
4
.5. Frontier molecular analysis - Electronic properties
Usually, the chemical reactions and resonance can be explained by interactions (overlap)
between frontier molecular orbitals and also used to explain the structure and reactivity of
molecules. The 3D diagram of the frontier molecular orbitals, in IR and UV-Visible region for
title compound were displayed in Figures 7 and 8 respectively. The title molecule was composed
by three molecular segments where two phenyl rings and thiosemicarbazone chain. The
symmetrical link was intersected by C of the chain. In LUMO, there were so many empty
orbitals appeared in which two phenyl rings have been connected by overlapping of σ and π
bonds among 13C, 12C, 3C, 4C and 5C. Two separate π bond interaction empty orbitals were
found on C15-C18 and C4-C5 bonds. The σ-bond interaction was taking place between C-H, C-
C, N-H, C-N bonds separately in the chain and the ring eventually. In the case of, HOMO, the
delta (δ) bond interaction appeared in C14-C13-C15 and C16-C20-C18 of top and base moiety of
the ring.
1
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The π- bond interaction was observed on C=N of the chain and σ-bond interaction lobes
found on C-N, N-H, C-H and C-S bonds. From this interaction, it was noted that, the empty
orbitals was mainly located in ring and N-H bonds whereas the filled orbitals was observed on
thiosemicarbazone chain and C-C-C of the ring. The electron transitions were happened between
those HOMO and LUMO and thus the compound has been stabilized. Here, the irrespective of
HOMO and LUMO, the σ and π orbital lobs were interlinked and the electron clouds were
shared their spatial orbitals and also spent their time in the place of link. During that time, the
analogous physical and chemical properties mutually shared between the ring (benzene) and
ligand (thiosemicarbazone). The charge levels were fluctuated due to the electron cloud sharing
and were evidenced in the Mulliken charge analysis. The band gap of the present compound was
found to be 3.866 eV which was moderate for electronic properties.
4
.6. Optical properties analysis
The observation of data of the electronic structure of present compound has explained the
optoelectronic character from which it can be identified that whether the compound optically
active or not. The electronic energy excitation of the present molecule were calculated at the
B3LYP/6-311++G(d,p) level using the TD-DFT approach in gas phase and with the solvent of
DMSO and Chloroform. The calculated excitation energies, oscillator strength (f) and
wavelength (λ) and spectral assignments are given in Table 5.
The range of UV-Visible from 200 to 380 nm is the portion of the spectrum normally
covered by the term ultraviolet. The atmospheric is transparent in this region and quarts optics is
generally active in this region [41]. The excitation of electrons from p & d orbitals, π-orbitals and
particularly π conjugated systems occurs above 200 nm and gives rise to readily accessible and
informative spectra. The compound under study is a semiconductor which was designed for the
purpose of opto electronic. In this case, the collective vibrational called opto-electronic transition
was observed in the region 300-360 nm with minimum energy gap of 3.44 eV. These transitions
have been assigned to n → σ* and n → π* for gas phase. In the solvent phases, there was no
considerable disparity found. But, the energy gap of the present compound was expanded up by
the solvent effect. Though, the entire transitions have been belonging to Quartz ultraviolet region
and the entire assignment restricted with B-band category in between UV and visible region, the
1
2

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NLO component was found to be active in the molecule. The molecular orbital lobe interaction
in UV-Visible is appeared in the Figure 8.
4
.7.Molecular electrostatic potential (MEP) maps
The molecular electrostatic potential is nothing but the existence of interaction energy
between the negative and positive charge distribution of a molecule. The molecular interaction
energy was calculated by using the equation
M
Qi
V(r ) =
1
∑

r − r 
j=1
1
j


If the charge distribution continuous over the compound, the MEP is then given by equation at
any instant
ρ
(r)
V (r ) =
dr
]
1
∫[
r1 − r
The MEP is highly informative concerning the protonic and electronic charge distribution
of a given molecule. It is mainly used for optical polarization interactions analysis analogous to
the crystalline state. It is also used for topographical analysis of the electronic structure and
molecular reactivity pattern of the composite materials.
Molecular electrostatic potential view was framed at B3LYP/6-311++G(d,p) level in
which the entire molecular interactive zones can be viewed. The potential energy interaction
between proton and electron fields is classified from high frequency (blue) region to higher
wavelength (red) region which designated that, the charge dislocation between electrophilic and
nucleophilic boundaries. In a molecule, charges are polarized rigorously in negative and positive
terminals, and there are significant differences in electron and proton density due to the doping
of substitution in base compound. The rich electro negativity region was indicated by affluent
red and positive (proton region) almost entirely blue.
1
3

ACCEPTED MANUSCRIPT
The two extreme ends of charge distribution was represented by the color code in the range
between -4.332 a.u. (genuine red faded to yellow) to 4.332 a.u. (genuine blue faded to green) and
it was shown in Figure 9. Generally, the negative region is mainly localized over the portion of
highly electronegative atoms. In this compound, only one significant electronegative atom
(Sulphur) was found. The negative domain was observed around sulphur atom of
thiosemicarbazone group. A rich positive region was identified on NH group of same
2
thiosemicarbazone group which indicated a possible site for nucleophilic attack. The neutral
region was found around two benzene rings where there was neither concentrated positive or
negative atoms. From this observation, it was obvious that, two reactive regions of the compound
located on same molecular group and thiosemicarbazone group was the main reason for the
molecule having active optical properties.
4
.8. NLO activity analysis
In nonlinear optics, the hyperpolarizabilities have much attention since their importance
for new materials and devices [42]. Nonlinear optical processes in π-electron organic systems
have attracted considerable interest because their understanding has also led to new theoretical
insight [43]. In this aspect, it was trusted that a systematic investigation of polarizabilities and
second hyperpolarizabilities furnishes new information and better understanding of these
properties.
The total hyperpolarizability (β) and its partial components of hyperpolarizability β , β and
x
y
β of present compound along with polarizabilities µ , αtotal, and ꢀα were reported in Table 6.
z
0
The calculated value of dipole moment of present compound was found to be 6.81 Debye which
was very high when compared with separate Benzophenone and thiosemicarbazone (3.66 and
4
.05 Debye respectively). The average polarizabilities of Benzophenone and thiosemicarbazone
were 162.24 and 59.65 esu respectively. The anisotropy of the Polarizability of the same
compounds was found to be 198.40 and 63.01 esu respectively. Whereas the calculated average
-24
−24
Polarizability and anisotropy of the Polarizability is 469.78 x10 esu and 318.53 x10 esu,
respectively. When thiosemicarbazone was added with Benzophenone, the entire polarizability
1
4

ACCEPTED MANUSCRIPT
parameters of BPTSC were increased much. In this case, the magnitude of first order
Polarizability found high which reflect the high optical characteristics of the compound.
−
30
In this present molecule, the hyperpolarizability (β) is 577.62 X 10 esu which was found
to be higher than standard value of urea. The title molecule, in crystal form, was able to produce
second order harmonic generation with two and three fold frequency. In this work, two separate
molecular groups were fused to form resultant molecule. The addition of thiosemicarbazone with
Benzophenone group enhanced the optical parameters and thus the NLO properties was tuned up
in the present compound; BPTSC. From this result, it was observed that, the molecular
hyperpolarizability was active and dynamic and the present compound can be used to prepare
NLO material for photonics technology.
4
.9. NBO profile
Usually, the Natural bond orbital (NBO) analysis is carried out to explain the dislocation
of electron density among the bonds by making in phase and out of phase interactions involved
in molecular systems. The NBO data was derived by computing natural Lewis structure of
orbitals. The interaction between both filled and unfilled orbital lobes elucidate the intra and
inter-molecular interactions. The second order perturbation theory of the Fock matrix was carried
out to evaluate a loss of occupancy from the idealized Lewis orbital to an empty non-Lewis
orbital (donor bonds (i) and acceptor bonds (j)) [44-45].
(
2)
The better E value is more intensive which is the interaction between proton-electron
donors and acceptor. The more donation tendency of donors to acceptors was greater the extent
of conjugation of the whole system than normal. The NBO data of the compound has been taken
out at B3LYP/6-311++G(d,p) level and the results were tabulated in Table 7. Several donor–
acceptor interactions have been observed for the present compound and among the strongly
occupied NBOs, the most important delocalization sites are in the π system and in the lone pairs
(n) of the sulphur and carbon atoms.
1
5

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The strong intermolecular hyper conjugative interactions were formed by orbital overlap
between bonding and antibonding systems. The σ-σ* overlapping was found between C1-C2 of
the phenyl ring and C-H bonds of the same ring as well as particularly, C3-C12 of the chain.
The hyper conjugation of π -π* also taking place between ring and chain. Thus the interaction
occurred between ring and chain means the properties of the chain was completely transferred to
ring. The σ -σ* orbital transition arise from C12-C13 bond to C27-S28 via C18-C20 and N25-
H26 (anti bond). In this way, the electron clouds oscillated between ring and chain and the
physical and chemical properties transported from ring and chain vice versa. Similarly, the π -π*
transition was found from C12 - N24 to C3 - C12 and C12 - C13. The σ -σ* strong interaction of
another phenyl ring was identified between C3 - C4 and C18 - C20-C27 - S28 and π -π* lobe
overlapping was observed between C5 - C6 and C12 - C13, C12 - N24, N24 - N25 and C27 -
S28. Therefore, the new properties were created by σ -σ* and π -π* interactions observed
between base and ligand of the compound.
4
.10. Thermodynamical analysis
The thermodynamic functions of the present compound with different temperatures were
calculated at B3LYP/6-311++G(d,p) level and were depicted in the Table 8. The entropy,
specific heat capacity and enthalpy were varied with respect to temperature in positive
coefficient basis. The temperature from 100K to 1000K, the variation of the parameters was
linear and sustained up to the maximum temperature. This view showed the consistent chemical
stability of the present compound. Similarly, the Gibbs free energy was found to be linear with
respect to temperature. The chemical reaction can feasibly occur when the Gibbs free energy of
the molecular system decreases. This means that, when ꢀG is negative or less than zero, the
chemical reaction is continued. If it is positive, the reaction is stopped. In this case, the Gibbs
energy was found be still negative up to 1000K and it was concluded that, the present compound
was chemically strong and active.
4
.11. Chemical properties
Usually, the the chemical applications can be identified from the Chemical properties of
the compounds. It is useful for recognizing the substance for the particular purpose. It was very
1
6

ACCEPTED MANUSCRIPT
important to know whether this compound is able to have rich potential for doping and starting
material for semiconductor application. Accordingly, the chemical hardness and potential,
electronegativity and Electrophilicity index were calculated and presented in Table 9.
The chemical hardness is an estimation of the chemical stability which is also
thermodynamic stability of the chemical substance. The chemical hardness of the present compound
was found to be 1.933 which was reasonable magnitude. Therefore, the present compound has
much chemical stability. Here, the ligand thiosemicarbazone group enriched the chemical
stability and rigidity character. So the present compound retains its useful properties on the
timescale of its expected doping utility.
The Electronegativity is a chemical property which explains the propensity of a molecule
or a functional group that interact the electron clouds towards it [46]. Usually, the
electronegativity is associated with different functional groups in the base compound. In this
case, the congregation of electronegativity was found to be 3.90 which was high and the property
of chemical bonds in the title molecule was changed from covalent to ionic. This was due to the
addition of thiosemicarbazone and imine group along with phenyl ring.
Electrophilicity index is a factor which is used to measure the energy lowering due to
maximal electron flow between ionization potential and electron affinity. As in the Table 9, the
Electrophilicity index was found to be 4.01 which ensured that the energy transition between
HOMO+1 and LUMO-1 than HOMO to LUMO. This view clearly showed that, the band gap of
the present compound was within the limit. The dipole moment is another important electronic
property of the chemical compound which is the ability of electrical and optical polarization of a
substance. The large dipole moment leads the compound; very strong intermolecular
interactions. The calculated dipole moment value for the present compound was 6.81 Debye. It
was comparatively very high and the present molecule was being highly polar where the strong
intermolecular interactions induced generally.
4
.12. VCD analysis
Vibrational circular dichroism (VCD) is an electro-magneto-optic effect and associated
with spectroscopic technique which detects differences in attenuation of left and right circularly
1
7

ACCEPTED MANUSCRIPT
polarized light passing through the compound. It is the extension of circular
dichroism spectroscopy into the IR and near infrared region [47]. Since VCD is sensitive to the
mutual orientation of distinct ligand groups in a molecule, it provides three-dimensional
structural information. It is a powerful technique which was used for the identification of
absolute configurations of the organic molecules [48-49]. VCD is the coupling of optical activity
to infrared vibrational spectroscopy. More specifically, VCD spectra are vibrational difference
spectra with respect to left and right circularly polarized IR and light radiations. The essence of
VCD is to combine the stereo chemical sensitivity of natural optical activity with the rich
structural content of vibrational spectroscopy. The result of a VCD measurement is the
combination of two vibrational spectra; VCD and its parent infrared spectrum. These can used
together to deduce information regarding elucidation of biologically and optically significant
molecules.
The VCD spectrum and enantiomers of the present molecule was depicted in Figure 10.
In this case, the spectrum was originated from zero and the intensity of the absorption was
elevated in positive and negative sides due to the left and right circular polarization. The
absorption intensity is usually unequal on both sides of the VCD spectrum, in this case, the
probability of amalgamation was found to be high in right side. Both the linear and circular
vibrational polarization bands belong to middle IR region which corresponding to the C=N,
C=C, C=S, C-C, N-N and C-N stretching vibrations and N-H and C-H in plane bending
wavenumbers. All such vibrational bands stated that, the functional groups were active which
encourage the inducement of the NLO applications. This vibrational dichroism was illustrated in
detail the active optical properties of the compound.
5
. Conclusion
In order to explore the NLO activity of the present compound; Benzophenone
thiosemicarbazone, this research attempt has been made make use of experimental and
theoretical investigation. In this work, the crystal was grown and characterized by executing
experimental spectroscopic (FT-IR, FT-Raman and NMR) analyses and theoretical studies (FT-
IR, FT-Raman, NMR, UV-Visible and VCD). The theoretical calculations have been carried out
using B3LYP/6-311G++G(d,p). The obtained results were found to be coherent and the entire
analyses explored the presence of efficient optical semiconducting properties and NLO activity
1
8

ACCEPTED MANUSCRIPT
of the present compound. The vibrational analysis confirmed the presence of ligand by observing
IR and Raman bands in suitable region of spectra. From the investigation, it was concluded that,
the combination of two phenyl rings along with the thiosemicarbazone group shape up the NLO
application in the compound.
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Figure captions
Figure 1: Molecular formation of Benzophenone thiosemicarbazone.
Figure 2: Crystal view in (111) plane and semicircle formation of thiosemicarbazone group.
Figure 2.1: XRD diagram of Benzophenone thiosemicarbazone.
Figure 3: Mulliken Charge Distribution in the compound.
Figure 4: Experimental and calculated FT-IR spectra of Benzophenone thiosemicarbazone.
Figure 5: Experimental and calculated FT-Raman spectra of Benzophenone thiosemicarbazone.
1
3
1
Figure 6: Experimental and simulated C and H NMR spectra of Benzophenone.
thiosemicarbazone
Figure 7: Frontier molecular orbital in IR region.
Figure 8: Frontier molecular orbital in UV-Visible region.
Figure 9: MEP display of Benzophenone thiosemicarbazone.
Figure 10: VCD spectra of Benzophenone thiosemicarbazone
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Table 1: Optimized parameters of Benzophenone-thiosemicarbazone
DFT/ CAM-
HF/
Bond Parameters
B3LYP
Experimental
6
-311++G(d,p)
6
-311++G(d,p)
Bond Lengths(Å)
C1-C2
C1-C6
C1-H7
C2-C3
C2-H8
C3-C4
C3-C12
C4-C5
C4-H9
1.384
1.386
1.075
1.389
1.075
1.389
1.500
1.385
1.075
1.384
1.075
1.075
1.492
1.261
1.389
1.393
1.386
1.074
1.381
1.073
1.383
1.075
1.387
1.075
1.391
1.392
1.084
1.401
1.084
1.401
1.497
1.393
1.084
1.394
1.084
1.084
1.481
1.292
1.403
1.404
1.393
1.082
1.389
1.083
1.393
1.084
1.394
1.085
-
-
-
-
-
-
-
-
-
-
-
-
C5-C6
C5-H10
C6-H11
C12-C13
C12-N24
C13-C14
C13-C15
C14-C16
C14-H17
C15-C18
C15-H19
C16-C20
C16-H21
C18-C20
C18-H22
-
1.287
-
-
-
-
-
-
-
-
-
-

ACCEPTED MANUSCRIPT
C20-H23
N24-N25
N25-H26
N25-C27
C27-S28
C27-N29
N29-H30
N29-H31
1.075
1.354
0.996
1.345
1.682
1.329
0.991
0.993
1.084
-
1.384
-
1.346
1.669
1.326
-
1.355
1.015
1.373
1.675
1.347
1.006
1.009
-
Bond Angles (˚)
C2-C1-C6
C2-C1-H7
C6-C1-H7
C1-C2-C3
C1-C2-H8
C3-C2-H8
C2-C3-C4
C2-C3-C12
C4-C3-C12
C3-C4-C5
C3-C4-H9
C5-C4-H9
C4-C5-C6
C4-C5-H10
C6-C5-H10
C1-C6-C5
C1-C6-H11
C5-C6-H11
C3-C12-C13
C3-C12-N24
120.1004
119.7648
120.1347
120.2657
119.9238
119.8105
119.4018
120.0206
120.5769
120.2714
119.8751
119.8536
120.0607
119.7287
120.2101
119.8962
120.0517
120.0521
118.8033
123.9507
120.161
119.732
120.105
120.429
120.040
119.530
119.039
120.256
120.703
120.415
119.687
119.894
120.127
119.703
120.169
119.824
120.096
120.079
119.365
123.211
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-

ACCEPTED MANUSCRIPT
C13-C12-N24
C12-C13-C14
C12-C13-C15
C14-C13-C15
C13-C14-C16
C13-C14-H17
C16-C14-H17
C13-C15-C18
C13-C15-H19
C18-C15-H19
C14-C16-C20
C14-C16-H21
C20-C16-H21
C15-C18-C20
C15-C18-H22
C20-C18-H22
C16-C20-C18
C16-C20-H23
C18-C20-H23
C12-N24-N25
N24-N25-H26
N24-N25-C27
H26-N25-C27
N25-C27-S28
N25-C27-N29
S28-C27-N29
C27-N29-H30
C27-N29-H31
H30-N29-H31
117.2449
120.6405
120.5018
118.8568
120.5568
120.0989
119.3427
120.5249
119.4125
120.0597
120.1696
119.6367
120.1936
120.2267
119.7094
120.0626
119.6573
120.1953
120.1461
119.9892
121.8182
120.9731
117.0827
120.1899
116.6052
123.2038
117.9771
120.9729
121.0237
117.421
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
120.597
120.925
118.476
120.705
119.748
119.543
120.669
119.037
120.289
120.263
119.615
120.120
120.344
119.668
119.984
119.536
120.252
120.209
119.692
122.205
121.254
116.533
120.248
115.228
124.5232
118.2765
120.1568
121.5046
-
-
-
-
115.1
119.5
-
117.5
-
122.9
-
-
-

ACCEPTED MANUSCRIPT
Dihedral Angles (˚)
C6-C1-C2-C3
C6-C1-C2-H8
H7-C1-C2-C3
H7-C1-C2-H8
C2-C1-C6-C5
C2-C1-C6-H11
H7-C1-C6-C5
H7-C1-C6-H11
C1-C2-C3-C4
C1-C2-C3-C12
H8-C2-C3-C4
H8-C2-C3-C12
C2-C3-C4-C5
C2-C3-C4-H9
C12-C3-C4-C5
C12-C3-C4-H9
C2-C3-C12-C13
C2-C3-C12-N24
C4-C3-C12-C13
C4-C3-C12-N24
C3-C4-C5-C6
C3-C4-C5-H10
H9-C4-C5-C6
H9-C4-C5-H10
C4-C5-C6-C1
C4-C5-C6-H11
H10-C5-C6-C1
H10-C5-C6-H11
-0.6956
179.3523
179.4066
-0.5454
-0.5196
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
179.547
179.526
-0.406
0.2123
-179.837
-179.833
0.117
0.2698
-179.8373
-179.8328
0.0601
0.5961
0.366
-179.701
-179.4518
0.2512
-179.31
-179.70
0.617
-0.0754
0.088
179.8982
-179.7766
0.197
-67.6808
111.9205
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ACCEPTED MANUSCRIPT
C3-C12-C13-C14
C3-C12-C13-C15
N24-C12-C13-C14
N24-C12-C13-C15
C3-C12-N24-N25
C13-C12-N24-N25
C12-C13-C14-C16
C12-C13-C14-H17
C15-C13-C14-C16
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C12-C13-C15-C18
C12-C13-C15-H19
C14-C13-C15-C18
C14-C13-C15-H19
C13-C14-C16-C20
C13-C14-C16-H21
H17-C14-C16-C20
H17-C14-C16-H21
C13-C15-C18-C20
C13-C15-C18-H22
H19-C15-C18-C20
H19-C15-C18-H22
C14-C16-C20-C18
C14-C16-C20-H23
H21-C16-C20-C18
H21-C16-C20-H23
C15-C18-C20-C16
C15-C18-C20-H23
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ACCEPTED MANUSCRIPT
H22-C18-C20-H23
C12-N24-N25-H26
C12-N24-N25-H27
N24-N25-H27-S28
N24-N25-H27-N29
H26-N25-H27-S28
H26-N25-H27-N29
N25-H27-N29-H30
N25-H27-N29-H31
S28-H27-N29-H30
S28-H27-N29-H31
0.3567
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