Crystal structure and third order nonlinear optical studies on 2-phenylbenzimidazolium-p-toulenesulphonate

Article abstract of DOI:10.13005/ojc/340116

A new third order nonlinear optical single crystal of 2-phenylbenzimidazolium-p-toulenesulphonate (PBITS) was grown by the solvent evaporation technique using methanol as a solvent. The single crystal XRD analysis reveals that crystals belong to the triclinic system. An NMR and FTIR study confirms the formation and vibrational analysis present in the compound. UV-Vis absorption studies were also carried out for the crystal. Nonlinear refractive index (n₂), absorption coefficient (β) and third order nonlinear optical susceptibility ((χ⁽³⁾)) of the crystals were evaluated by Z-Scan studies.

Full text of DOI:10.13005/ojc/340116

ISSN: 0970-020 X
CODEN: OJCHEG
2018, Vol. 34, No.(1):
Pg. 143-151
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
www.orientjchem.org
Crystal Structure and Third Order Nonlinear Optical Studies
on 2-phenylbenzimidazolium-p-toulenesulphonate
C.SUDHAKAR1,2, M.SARAVANABHAVAN3 , M.SEKAR2*, B.BABU4 and J.CHANDRASEKARAN4
1Research Center, Bharathiar University, Coimbatore – 641 046, India.
2Post-Graduate and Research Department of Chemistry, Sri Ramakrishna Mission Vidyalaya College
of Arts and Science, Coimbatore – 641 020, Tamil Nadu, India.
3Department of Chemistry, Dr. N.G.P. Institute of Technology, Coimbatore -641048, Tamil Nadu, India.
4Post-Graduate and Research Department of Physics, Sri Ramakrishna Mission Vidyalaya College of
Arts and Science, Coimbatore – 641 020, Tamil Nadu, India.
*Corresponding author E-mail: drmsbavan@gmail.com
http://dx.doi.org/10.13005/ojc/340116
(Received: June 01, 2017; Accepted: August 25, 2017)
ABSTRACT
A new third order nonlinear optical single crystal of 2-phenylbenzimidazolium-p-
toulenesulphonate (PBITS) was grown by the solvent evaporation technique using methanol as a
solvent. The single crystal XRD analysis reveals that crystals belong to the triclinic system. An
NMR and FTIR study confirms the formation and vibrational analysis present in the compound.
UV-Vis absorption studies were also carried out for the crystal. Nonlinear refractive index (n2),
(3)
absorption coefficient (β) and third order nonlinear optical susceptibility ((χ )) of the crystals were
evaluated by Z-Scan studies.
Keyword: Crystal, 2-phenylbenzimidazolium-p-toulenesulphonate (PBITS), Crystal XRD,
NMR and FTIR study.
INTRODUCTION
its vital applications in areas of optical switching,
optical data storage for the developing technologies
in telecommunications, frequency mixing, optical
parametric oscillation, optical bi-stability, optical
logic gates, laser radiation protection, optical image
processing, under water communication,
biomedical and signal processing analysis etc1-5.
A fascinating new field of research termed
“nonlinear” optics was introduced to the scientific
and engineering community after the invention of
laser. Nonlinear optics has arisen as one of the
most attractive fields of current research in view of
This is an
Open Access article licensed under a Creative Commons Attribution-NonCommercial-ShareAlike
4.0 International License (https://creativecommons.org/licenses/by-nc-sa/4.0/ ), which permits unrestricted
NonCommercial use, distribution and reproduction in any medium, provided the original work is properly cited.

144
Organic NLO single crystals are very efficient for Materials and instrumentation
SEKAR et al., Orient. J. Chem., Vol. 34(1), 143-151 (2018)
THz generation and high signal to noise ratios
All the chemicals were purchased from
detection due to their large nonlinear optical Sigma-Aldrich in the highest purity available.
susceptibilities and ultrafast response times6,7. It has Solvents were purified and dried according to the
been understood that the second-order and standard procedure. Single crystal X-ray diffraction
third-order molecular nonlinearity can be enhanced data of PBITS compound was collected at room
by large delocalized π-electron systems with strong temperature on a Bruker Diffractometer equipped
donor and acceptor groups8-10. Based on these with a fine focused sealed tube. The unit cell
specifies in the present investigation donor–acceptor parameters were determined and the data
based crystals of 2-phenylbenzimidazolium-p- collections of PBITSwas performed using a
toulenesulphonate has been grown by the slow graphite-mono chromate Mo Kα (λ = 0.71073 Å)
evaporation technique andits structural, optical, and radiation by ϕ and ω scans. The structure of the
third order nonlinear optical properties were compound was solved by direct method using
discussed in detail.
SHELXS-97, which revealed the position of all non-
hydrogen atoms, and was refined by full-matrix least
squares on F2 (SHELXL-97)11. All non-hydrogen
atoms were refined anisotropically, while the
EXPERIMENTAL
Material synthesis and growth of pbitssingle crystal hydrogen atoms were placed in calculated positions
Equimolar ratio of p-toluenesulphonic acid and refined as riding atoms. The electronic
in methanol and 2-phenylbenzimidazole in absorption spectrum was measured in methanol
methanol were prepared at room temperature, using SHIMADZU 1601 UV-Vis spectrophotometer
mixed and stirred well for about 3 h to get clear in the range of 200-600 nm. In order to confirm the
solution. This solution was filtered using Whatmann functional groups of the crystal was subjected to
41 filter paper and kept aside unperturbed in a FT-IR spectral analysis by Perkin Elmer FT-IR 8000
dust-free room for the growth of single crystals. Well spectrophotometer in the range of 4000-400 cm-1
defined, transparent crystals were collected at the using the KBr pellets method. To confirm the
end of 6th day. The collected crystals were molecular structure of the compound the 1H and 13
C
recrystallized using dry methanol to get good quality NMR spectra were recorded employing a Bruker
crystals. The reaction scheme and the chemical AV III 400 MHz spectrometerin deuterated dimethyl
structure were illustrated.
sulfoxide as solvent using TMS as an internal
standard. The nonlinear optical measurements
were carried out by using single beam Z-scan
technique with a He-Ne laser operated at a repetition
rate of 1 kHz and at the wavelength of 632 nm.
SO3H
H
N
N
2-PHENYLBENZIMIDAZOLE
CH3
RESULTS AND DISCUSSIONS
P-TOLUENE
SULPHONIC
ACID
Methanol
3 hours stirrer
Single crystal XRD analysis
From X-ray diffraction studies, it is known
H
N
that the crystal belongs to the triclinic system with
the space group of P-1 and the lattice parameters
are a = 8.2912(5)Å, b = 9.7197(6)Å, c = 11.4293(9)Å
= 82.311(4)o, β =89.626(3)o, γ= 77.915(3)o. The
crystal data and details of the data collection and
the structure refinement are given in Table. 1. The
bond length and bond angles of PBITS crystal are
given in Table 2 and 3 respectively. Fig. 1 shows
the ORTEP view of the molecule drawn at 50%
probability thermal displacement ellipsoids with the
atom numbering scheme. The packing arrangement
NH+
-
SO3
CH3
2-PHENYLBENZIMIDAZOLIUM-P-TOLUENESULPHONATE
Scheme 1. Synthesis of 2-phenylbenzimidazolium-
p-toulenesulphonate

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SEKAR et al., Orient. J. Chem., Vol. 34(1), 143-151 (2018)
of the molecule viewed down a, b and c axis are
shown in Fig. 1.a, b, and c respectively.From
molecular structure of PBITS, we could see that
there is an intermolecular hydrogen bonding between
N-H group of 2-phenylbenz imidazoliniumcation
and P-toluenesulphonate anion. The N-atom of the
2-phenyl benzimdazole cation forms N-H........O
hydrogen bonds with the O atom of the 2-phenyl
sulphonate anion. In the title compound the C=NH
group of the 2-phenylbenzimidazole residue is
engaged in the strong hydrogen bonding with
the P-toluenesulphonatesulphonate anion. The
selected bond distance and angles are shown in
Table4 respectively. The molecule is stabilized by
C-H.......O bifurcated hydrogen bonds. All
non-hydrogen atoms were refined anisotropically
and the hydrogen atoms were placed in geometric
positions and refined as riding atoms except for
those bound to oxygen and nitrogen, which were
freely refined.
Fig. 1. ORTEP diagram of PBITS
NMR spectral analysis
The 1H NMR spectrum of the PBITS single
The 13C NMR spectrum of the PBITS
single crystal was recorded employing a Brucker
400 MHz spectrometer using TMS as the internal
reference standard. The 13C NMR spectrum of the
PBITS is depicted in Fig. 3. In the downfield carbon
signal at δ 154.25 is correspond to the C7 carbon
of 2-phenylbenzimidazole moiety. The carbon
signal at δ 150.22 is belongs to the C14 carbon of
p-toluenesulphonicacid moiety. The carbon signal
at δ 143.41 is correspond to the C5carbon of
p-toluenesulphonicacid moiety. The carbon signal
at δ 138.63 is belongs to the C4 carbon of
2-phenylbenzimidazole moiety. The sharp and
intense signal at δ 137.06 is due to the C15 and C20
carbons of the same kind in the p-toluenesulphonicacid
moiety. The carbon signal at δ 134.94 is correspond
to the C8and C11 carbons of 2phenylbenzimidazole
moiety. The sharp and intense signal at δ 133.20
is due to the C9 and C13 carbons of the same kind
in the2-phenylbenzimidazole moiety. The carbon
signal at δ 131.28 is belongs to the C10 and C12
crystal was recorded employing a Brucker 400 MHz
spectrometer using TMS as the internal reference
1
standard. The H NMR spectrum of the PBITS is
depicted in Fig. 2.The singlet peak observed at δ
2.298 has been assigned to three protons of the
methyl group in the 2-phenylbenzoimidazolium
p-toluenesulphonate. The doublet peak centred at
δ 7.146 (J = 8 Hz) is due to the C19 and C16
protons of the same kind in aromatic ring of
2-phenylbenzoimidazolium-p-toluenesulphonate.
Another doublet peak centred at δ 8.226(J =6.8 Hz)
is due to the C15 and C20 protons of the same kind in
aromatic ring of 2phenylbenzoimidazolium-p-
toluenesulphonate. The multiplet peak centred at δ
7.901-7.572 is due to the C1, C2, C3, C4, C9, C10, C11,
C12 and C13 protons of the same kind of the
aromatic ring of 2-phenylbenzoimidazolium-p-
toluenesulphonate. The NH proton appeared as
singlet at δ 5.4.

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SEKAR et al., Orient. J. Chem., Vol. 34(1), 143-151 (2018)
carbon of 2-phenylbenzimidazole moiety. The toluenesulphonicacid moiety. The sharp and
carbon signal at δ 130.74 is correspond to the C16 intense signal at δ 119.36 is due to the C17 carbon of
and C19 carbon of 2-phenylbenzimidazole moiety. the same kind in the 2-phenylbenzimidazole moiety.
The sharp and intense signal at δ 128.31 is due to The carbon signal at δ 26.02 is correspond to the
the C2 and C3 carbons of the same kind in the p- methyl carbon of 2-phenylbenzimidazole moiety.
Fig. 2. 1H NMR spectrum of PBITS
Fig. 3. 13C NMR spectrum ofPBITS

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SEKAR et al., Orient. J. Chem., Vol. 34(1), 143-151 (2018)
FT-IR SPECTRAL STUDIES
The FT-IR spectrum of PBITS crystal was
recorded employing a Perkin Elmer FT-IR
spectrometer using KBr pellet technique in the
range 4000-400 cm-1 and the FT-IR spectrum of
PBITScrystal is depicted in Fig. 4.The recorded FT-
IR spectrum was analyzed to ascertain the functional
groups presented in the compound. The formation
of the PBITSduring the reaction between p-
toluenesulphonicacid and 2-phenylbenzimidazole
strongly evident by the presence of the main
characteristic infrared band present in the crystal.
The formation of PBITS is evident by the presence
of most prominent group in PBITScrystal such as
N-H, C-H, C=N, C-N and SO2 groups. The band
observed at 3336 cm-1 is due to the N-H symmetric
stretching vibration. The aromatic C-H stretching
vibration is observed at 3062 cm-1, 2930 cm-1 and
2853 cm-1. The band observed at 1634 cm-1 is
indicate the presence of C=N group in the PBITS
molecule. The aromatic C-H bending vibration is
observed at 1457 cm-1.The band 1396 cm-1 indicates
the presence of C-N stretching vibration in the
molecule. The sharp band observed at1166 cm-1
indicates the presence of aromatic SO2 symmetric
stretching vibration.
Fig. 4. FT-IR spectrum of PBITS
Electronic absorption spectroscopic studies
The UV-Visible absorption spectrum of
PBITS crystal was recorded employing a systronics
make double beam spectrophotometer 2202 in a
range from 200 to 600 nm using DMSO as solvent
and the spectrum shown in Fig. 5. From the
spectrum, it is observed that the compound exhibits
two characteristics absorption bands.The bands at
about 296.0 and 329.6 nm are assigned to π→π∗
transition of the title compound. Also the absence
of absorption in the region between 330nm to 600
nm makes the crystal suitable for optical
applications7,12
Table. 1: Crystal data and structure refinement for PBITS
.
Empirical formula
C20 H18 N2 O3 S
Formula weight
Temperature
366.42
296(2) K
Wavelength
Crystal system, space group
Unit cell dimensions
0.71073Å
Triclinic, P-1
a = 8.2912(5) Å , alpha = 82.311(4) deg
b = 9.7197(6) Å , beta = 89.626(3) deg
c = 11.4293(9)Å, gamma = 77.915(3) deg
892.33(10) A3
Volume
Z, Calculated density
Absorption coefficient
F(000)
2, 1.364 Mg/m3
0.204 mm-1
384
Crystal size
Theta range for data collection
Limiting indices
0.35 x 0.30 x 0.25 mm
1.80 to 28.36 deg.
-11<=h<=8, -12<=k<=11,-15<=l<=15
6971 / 4272 [R(int) = 0.0167]
95.90%
Reflections collected / unique
Completeness to theta = 28.36
Absorption correction
Max. and min. Transmission
Refinement method
Data / restraints / parameters
Goodness-of-fit on F^2
Final R indices [I>2sigma(I)]
R indices (all data)
Semi-empirical from equivalents
0.9508 and 0.9320
Full-matrix least-squares on F2
4272 / 0 / 236
1.071
R1 = 0.0543, wR2 = 0.1481
R1 = 0.0670, wR2 = 0.1642
0.643 and -0.471 e.A-3
Largest diff. peak and hole

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SEKAR et al., Orient. J. Chem., Vol. 34(1), 143-151 (2018)
Table. 2: Bond lengths [Å] forPBITS
S(1)-O(2)
1.4383(17)
1.4562(15)
1.4584(16)
1.772(2)
1.325(3)
1.397(3)
0.86
S(1)-O(3)
S(1)-O(1)
S(1)-C(14)
N(1)-C(7)
N(1)-C(5)
N(1)-H(1N1)
N(2)-C(7)
1.328(3)
1.389(3)
0.86
N(2)-C(6)
Fig. 5. Electronic absorption spectrum of PBITS
N(2)-H(2N2)
C(3)-C(4)
1.383(4)
1.410(4)
0.93
C(3)-C(2)
C(3)-H(3)
C(4)-C(5)
1.380(3)
0.93
C(4)-H(4)
C(5)-C(6)
C(7)-C(8)
C(8)-C(9)
C(8)-C(13)
C(9)-C(10)
C(9)-H(6)
1.378(3)
1.475(3)
1.398(3)
1.399(3)
1.368(4)
0.93
C(10)-C(11)
C(10)-H(10)
C(11)-C(12)
C(11)-H(11)
C(2)-C(1)
1.364(4)
0.93
1.363(4)
0.93
1.364(4)
0.93
C(2)-H(2)
Fig. 6(a). Normalized transmittance with open aperture
C(1)-C(6)
C(1)-H(1)
1.379(3)
0.93
C(13)-C(12)
C(13)-H(13)
C(12)-H(12)
C(14)-C(20)
C(14)-C(15)
C(15)-C(16)
C(15)-H(15)
C(16)-C(17)
C(16)-H(16)
C(17)-C(19)
C(17)-C(18)
C(18)-H(18A)
C(18)-H(18B)
C(18)-H(18C)
C(20)-C(19)
C(20)-H(20)
C(19)-H(19)
1.369(4)
0.93
0.93
1.381(3)
1.384(3)
1.379(3)
0.93
1.383(3)
0.93
1.384(4)
1.510(4)
0.96
0.96
0.96
1.385(4)
0.93
0.93
6(b) Normalized transmittance with closed aperture

149
SEKAR et al., Orient. J. Chem., Vol. 34(1), 143-151 (2018)
Table. 3: Bond angles [Å] forPBITS
C(12)-C(13)-C(8)
C(12)-C(13)-H(13)
C(8)-C(13)-H(13)
C(11)-C(12)-C(13)
C(11)-C(12)-H(12)
C(13)-C(12)-H(12)
C(20)-C(14)-C(15)
C(20)-C(14)-S(1)
119.5(2)
120.3
O(2)-S(1)-O(3)
O(2)-S(1)-O(1)
O(3)-S(1)-O(1)
O(2)-S(1)-C(14)
O(3)-S(1)-C(14)
O(1)-S(1)-C(14)
C(7)-N(1)-C(5)
C(7)-N(1)-H(1N1)
C(5)-N(1)-H(1N1)
C(7)-N(2)-C(6)
C(7)-N(2)-H(2N2)
C(6)-N(2)-H(2N2)
C(4)-C(3)-C(2)
C(4)-C(3)-H(3)
C(2)-C(3)-H(3)
C(5)-C(4)-C(3)
114.48(11)
114.15(12)
110.06(10)
106.17(11)
105.48(10)
105.63(9)
108.24(18)
125.9
125.9
108.24(18)
125.9
125.9
121.1(2)
119.4
120.3
11.1(2)
119.4
119.4
119.2(2)
120.99(17)
119.78(16)
120.4(2)
119.8
C(15)-C(14)-S(1)
C(16)-C(15)-C(14)
C(16)-C(15)-H(15)
C(14)-C(15)-H(15)
C(15)-C(16)-C(17)
C(15)-C(16)-H(16)
C(17)-C(16)-H(16)
C(16)-C(17)-C(19)
C(16)-C(17)-C(18)
C(19)-C(17)-C(18)
C(17)-C(18)-H(18A)
C(17)-C(18)-H(18B)
H(18A)-C(18)-H(18B)
C(17)-C(18)-H(18C)
H(18A)-C(18)-H(18C)
H(18B)-C(18)-H(18C)
C(14)-C(20)-C(19)
C(14)-C(20)-H(20)
C(19)-C(20)-H(20)
C(17)-C(19)-C(20)
C(17)-C(19)-H(19)
C(20)-C(19)-H(19)
119.8
121.0(2)
119.5
119.5
119.4
118.2(2)
120.5(2)
121.3(2)
109.5
115.9(2)
C(5)-C(4)-H(4)
C(3)-C(4)-H(4)
C(6)-C(5)-C(4)
C(6)-C(5)-N(1)
C(4)-C(5)-N(1)
N(1)-C(7)-N(2)
N(1)-C(7)-C(8)
N(2)-C(7)-C(8)
C(9)-C(8)-C(13)
C(9)-C(8)-C(7)
C(13)-C(8)-C(7)
C(10)-C(9)-C(8)
C(10)-C(9)-H(6)
C(8)-C(9)-H(6)
C(11)-C(10)-C(9)
C(11)-C(10)-H(10)
C(9)-C(10)-H(10)
C(12)-C(11)-C(10)
C(12)-C(11)-H(11)
C(10)-C(11)-H(11)
C(1)-C(2)-C(3)
C(1)-C(2)-H(2)
C(3)-C(2)-H(2)
C(2)-C(1)-C(6)
C(2)-C(1)-H(1)
C(6)-C(1)-H(1)
C(5)-C(6)-C(1)
C(5)-C(6)-N(2)
C(1)-C(6)-N(2)
122.1
122.1
109.5
122.6(2)
106.4(2)
131.0(2)
110.2(2)
124.95(19)
124.81(19)
118.8(2)
120.9(2)
120.3(2)
119.9(2)
120.0
109.5
109.5
109.5
109.5
119.9(2)
120.1
120.1
121.3(2)
119.3
119.3
Z-scan studies
120.0
The Z-scan is a well-known experimental
technique to measure the intensity dependent third
order nonlinear susceptibility of the materials13,14
120.7(2)
119.6
.
119.6
The open and closed aperture Z-scan configurations
are used to investigate the nonlinear absorption
coefficient β and nonlinear refractive index n2.
Fig 6a shows the normalized transmittance (T) with
a closed aperture as a function of the distance z
along the lens axis in the far field.The Fig.6(b) shows
the normalized transmittance with open aperture
as a function of the distance z along the lens axis in
the far field. The nonlinear refractive index (n2) of
the crystal was calculated using the standard
relations given below:
120.0(2)
120.0
120.0
122.1(3)
119.0
119.0
116.4(2)
121.8
121.8
121.9(2)
106.9(2)
131.2(2)
(1)

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SEKAR et al., Orient. J. Chem., Vol. 34(1), 143-151 (2018)
where ΔTp-v is the difference between the
(6)
normalized peak and valley transmittance and S is
the linear transmittance of the aperture. The
nonlinear refractive index (n2) and nonlinear
absorption coefficient (β) are given by,
where ε0 is the vacuum permittivity, n0 is
the linear refractive index of the sample and c is the
velocity of light in vacuum.Thus, we can easily obtain
the absolute value of χ(3) using the following
formula
(2)
(3)
(7)
where k is the wave number k = 2p/λ and
As seen from the closed aperture Z scan
curve, the prefocal transmittance valley is followed
by the post focal peak, which is the positive
nonlinearity15. The calculated value of the nonlinear
(4)
with
defined as the peak intensity within the refractive index (n2) is 6.40149 10-8 cm2/W. The value
of the nonlinear absorption coefficient (β) estimated
sample, where Leffis the thickness of the sample
and α is the linear absorption coefficient. The real
and imaginary parts of the third order nonlinear
susceptibility χ(3) are defined as
from the open aperture Z-scan curve is 2.4603 x
10-4 cm/W. The third order susceptibility of PBITS is
1.3061 x 10-7 esu. As the material has a positive
refractive index, it results in self-focusing nature of
the material, which is an essential property for all
optical switching devices16.
(5)
Table. 4: Hydrogen bonds for PBITS
d(H..A) <DHA
1.82 170
D-H…A
d(D-H)
d(D..A)
Symmetry
N1—H1N1…O1
N2—H2N2…O3
C9—H6…O1
C16—H16…O2
C20—H20…O2
0.860
0.860
0.930
0.930
0.930
2.674
2.691
3.450
3.410
2.892
x, y, z+1
x,-1+y,1+z
x,y,1+z
1.87
2.56
2.54
2.51
160
160
156
105
-1+x,y,z
CONCLUSIONS
that the crystal belongs to the triclinic system with
the space group of P-1. UV-Visible absorption
New bright, transparent organic spectrum confirms the suitability of the title crystal
compound, PBITS was synthesized and crystal for various optical applications. The molecular
crown by slow evaporation solution growth method structure of the compound was confirmed by the FT-
at room temperature. The material synthesized IR, 1H and 13C NMR spectral studies.Z-scan studies
characterized by various analytical, spectroscopic reveal the self-focusing nature of the material, which
and single crystal XRD studies. From X-ray is a vital property for all optical switching and optical
diffraction studies, PBITS single crystal is observed limiting applications.
REFERENCES
1.
2.
Babu, B.;Chandrasekaran, J.;Thirumurugan,
R.;Jayaramakrishnan, V.;Anitha,K.;J. Mater. 3.
Sci: Mater. Electron., 2017, 28, 1124.
T.;Mefleh, A.;Benet, S.;Opt.Mater., 2000, 15,51.
Subhashini,V.; Ponnusamy,S. ;Muthamizhchelvan,
C.; Spectrochim. Acta Part A., 2012, 87, 265.
Saravana Kumar, G.;Murugakoothan,
Majchrowski, A.;Kityk, I.V.;£ukasiewicz, 4.

151
SEKAR et al., Orient. J. Chem., Vol. 34(1), 143-151 (2018)
P. ;Optik., 2015, 126,68.
MartinBrittoDhas, S.A.;Natarajan,S.;Opt.
Commun., 2008, 281, 457.
10.
11.
12.
13.
14.
Mohana, J.;Ahila, G.;DivyaBharathi, M.;
Anbalagan, G.;J. Cryst. Growth., 2016, 450, 181.
Sheldrick, G.M.;SHELXL97 and SHELXS97,
University of Gottingen, Germany., 1997, 327.
Babu,B.; Chandrasekaran, J.; Balaprabhakaran,
S.;Optik., 2014,125,3005.
Sheik-Bahae, M.;Said, A.A.;Van Stryland
E.W.;Opt. Lett.,1989,17, 955.
Sheik-Bahae, M.;Said, A.A.;Wei, T.H.;Hagan,
D.J.;Van Stryland,E.W.; IEEE J. Quan.
Elect.,1990, 26, 760.
5.
6.
Peramaiyan, G.;Pandi, P.;Sornamurthy,
B.M.;Bhagavannarayana, G.;Mohan Kumar,
R.;Spectrochim. Acta Part A., 2012, 95, 310.
Thirupugalmani, K.; Karthick, S.; Shanmugam,
G.; Kannan, V.; Sridhar, B.;Nehru, K.;
Brahadeeswaran, S.; Opt. Mater. 2015., 49, 158.
Chemla, D.S.;Zyss, J.;Nonlinear Optical
Properties of Organic molecules and crystals,
1-2, Academic Press, Orlando, New York,
1987.
7.
8.
15.
16.
Gomez, S.L.;Cuppo, F.L.S.;FigueriredoNeto,
A.M.;Braz. J. Phys.,2003, 33, 813.
Sheik, M. David, C.H.; Hagan, D.J.; VanStryland,
E.W.;IEEE J. Quan. Elect., 1991, 27, 1296.
9.
Suresh, M.; Asath Bahadur S.; and Athimoolam,
S. J.; J. Mol. Struct. 2016., 1112, 63.