Molecular structure, linear optical, second and third-order nonlinear optical properties of two non-centrosymmetric thiophene-chalcone derivatives

Article abstract of DOI:10.1016/j.molstruc.2020.128901

Two chalcones, (2E)-1-(5-bromothiophen-2-yl)-3-(3-fluorophenyl) prop-2-en-1-one (3F5B2SC) and (2E)-1-(5-bromothiophen-2-yl)-3-(4-methoxyphenyl) prop-2-en-1-one (4M5B2SC) were synthesised and crystallized by slow evaporation solution growth technique to in

Full text of DOI:10.1016/j.molstruc.2020.128901

Journal Pre-proof
Molecular structure, linear optical, second and third-order nonlinear
optical properties of two non-centrosymmetric thiophene-chalcone
derivatives
Vasant S. Naik , Parutagouda Shankaragouda Patil , Qin Ai Wong ,
Ching Kheng Quah , Neelamma B. Gummagol , H.S. Jayanna
PII:
S0022-2860(20)31226-6
DOI:
Reference:
https://doi.org/10.1016/j.molstruc.2020.128901
MOLSTR 128901
To appear in:
Journal of Molecular Structure
Received date:
Revised date:
Accepted date:
10 May 2020
11 July 2020
13 July 2020
Please cite this article as: Vasant S. Naik , Parutagouda Shankaragouda Patil , Qin Ai Wong ,
Ching Kheng Quah , Neelamma B. Gummagol , H.S. Jayanna , Molecular structure, linear optical,
second and third-order nonlinear optical properties of two non-centrosymmetric thiophene-chalcone
derivatives, Journal of Molecular Structure (2020), doi: https://doi.org/10.1016/j.molstruc.2020.128901
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Highlights
 Two NLO active chalcones have been synthesised and optimised by DFT method.
 The molecular structures have been confirmed by experimental and theoretical methods.
 The transparency, energy gap are determined by experimental and calculation methods.
 The thermal stability, FMOs, MEP and NBO of the chalcone are studied.
 The optical limiting, second and third order NLO properties are determined.
 Dipole moment, polarizability and hyperpolarizability are compute theoretically.
Page 1 of 42

Molecular Structure, Linear Optical, Second and Third-Order
Nonlinear Optical Properties of Two Non-centrosymmetric
Thiophene‐Chalcone Derivatives
Vasant S. Naik a, b, Parutagouda Shankaragouda Patil c, *, Qin Ai Wong d, Ching
Kheng Quah d, Neelamma B. Gummagol c, H. S. Jayanna b,*
a Department of Physics, Government First Grade College, Kumta - 581 343, Karnataka, India
b Department of Physics, Kuvempu University, Shankaraghatta - 577 451, Karnataka, India
Department of Engineering Physics, K.L.E. Institute of Technology, Hubballi 580027, Karnataka, India
d X-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, Penang 11800, Malaysia
c
*Corresponding author, E-mail address: jayanna60@gmail.com (Prof. H. S. Jayanna)
pspatilcrystal@gmail.com (Dr. P. S. Patil)
Abstract
Two chalcones, (2E)-1-(5-bromothiophen-2-yl)-3-(3-fluorophenyl) prop-2-en-1-one (3F5B2SC) and (2E)-
1-(5-bromothiophen-2-yl)-3-(4-methoxyphenyl) prop-2-en-1-one (4M5B2SC) were synthesised and
crystallized by slow evaporation solution growth technique to investigate their structural, linear, thermal
and nonlinear optical properties. Initially, the structures of 3F5B2SC and 4M5B2SC were confirmed by
13
FT-IR and NMR (1H and C NMR) spectroscopic studies. Detail solid state structures of these grown
crystals were determined by single crystal XRD data. Both the chalcones are crystallized in the non-
centrosymmetric monoclinic crystal system. The thermal analysis (DSC, TGA, DTA and DTG) revealed
that 3F5B2SCand 4M5B2SC molecules are thermally stable upto their melting points for solid state
studies. The linear optical properties of these chalcones were studied in the UV-Vis-NIR region. The
estimated direct energy band gap of the molecules by Tauc’s plot (4.7 eV for 3F5B2SC and 4.2 eV for
4M5B2SC) are comparable with HOMO-LUMO gaps. The MEP and NBO of both molecules are studied
by DFT method. The second harmonic generation (SHG) efficiency of 4M5B2SC and 3F5B2SC
determined by Kurtz-Perry powder method is found to be 5.3 and 4.2 times that of urea, respectively.
Third-order NLO parameters, such as nonlinear absorption coefficient (β = ~10-4 cm/W), nonlinear
Page 2 of 42

refractive index (n2= ~10-9 cm2/W), susceptibility (χ(3)= ~ 10-7 esu) and molecular hyperpolarizability (γh =
~
10-27 esu) were determined unambiguously from Z-scan experimental data analysis. The molecules
exhibited optical limiting behaviour for continuous wave (CW) laser operating at 532 nm wavelength.
Computationally, the static and dynamic dipole moment, polarizability and hyperpolarizability were
determined by TD-DFT and TD-HF method. The obtained results suggest that the studied thiophene-
chalcones may be used in optical device as frequency generator, optical limiters and optical switches.
Keywords: Chalcone derivatives; Single crystal XRD; Nonlinear optical materials; Z-scan technique;
Optical limiting; Density functional theory.
1. Introduction
Non linear optical (NLO) materials are capturing the attention of material scientists because of their
potential applications in optical fields [1, 2]. Over the few decades organic, inorganic, organo metallic and
organic-inorganic hybrid materials have been explored for NLO applications [3, 4]. The realization of
suitable organic materials as NLO devices, they must constituent molecules with unique properties of
spatial arrangement of charge transfer chromophores and also outstanding optical and thermodynamic
endurance [5].
Chalcones consist of two aromatic rings, mainly benzene, thiophene, biphenyl and pyridine groups, are
linked by α, β unsaturated carbonyl system. Different electron donor/or acceptor substitution groups
attached to two aromatic rings at different position leads to change in the properties of these molecules [6-
9]. The numerous pharmacological activities of chalcone derivatives with electron rich thiophene
heterocyclic system are subjects of great interest for researchers [10-13]. In the last decade many
researchers have reported the chalcones, with bromo and sulphur atom especially in the form of thiophene
ring, due to its ability to form good quality crystals with moderately higher NLO properties [14-16]. In
recent years, chalcones with thiophene moiety have acquired considerable attention because of their
immense tendency to crystallise in non-centrosymmetric structures, exceptional second-order (Second
Harmonic Generation) and third-order (n2, β, χ(3), γh ) NLO properties [17-20].
The numerous applications of these chalcones in the different fields and change in the properties of
these chalcone with different structures inspire us to synthesise two novel chalcones (2E)-1-(5-
bromothiophen-2-yl)-3-(3-fluorophenyl)prop-2-en-1-one (3F5B2SC) and (2E)-1-(5-bromothiophen-2-yl)-
3-(4-methoxy phenyl)prop-2-en-1-one (4M5B2SC). We crystallised these two chalcones to find molecular
structures with the help of single crystal XRD data. The structure was further confirmed by experimental
and computed IR spectrum. The transparency in the visible region was determined using experimental and
Page 3 of 42

calculated UV-Vis-NIR spectrum. The optical energy gap was calculated using Tauc’s plot and HOMO-
LUMO plots. Thermal stability and melting point were estimated by DSC and DTA/DTG/TGA graphs.
The second order nonlinear optical properties were characterised and compared its efficiency with urea.
The third-order NLO properties and optical limiting were characterised by Z-scan technique and different
parameters were calculated. The NLO parameters dipole moment, polarizability and hyperpolarizabilty
were computed with DFT and TDHF methods.
2. Experimental
2.1. Synthesis and crystal growth of chalcones
The chalcones reported in this research article 3F5B2SCand 4M5B2SC were prepared by Claisen -
Schmidt condensation method [14, 19]. The given compounds were synthesised by using commercially
available AR grade reactants purchased from sigma Aldrich. Solution of 5-Bromo-2-acetylthiophene (0.01
mol) dissolved in methanol (20 ml) was mixed with for 3F5B2SC 3-fluorobenzaldehyde (0.01 mol)
dissolved in methanol (20 ml) and for 4M5B2SC 4-methoxybenzaldehyde (0.01 mol) dissolved in
methanol (20 ml). Dissolved mixture in the conical flask was set for the vigorous stirring using magnetic
stirrer and litle quantity of NaOH (5 ml, 20%) was added slowly to the mixture with burette. For the better
yield stirring the mixture for 4 hours and the ice-cold water (250 ml) was poured into the conical flask. The
conical flask was kept undisturbed for 24 hour. The product formed were filtered, repeatedly washed with
distilled water, dried and purified by repeated crystallization. The reaction mechanism is displayed in Fig.
1.
Fig.1. Synthesis of 3F5B2SC and 4M5B2SC chalcone derivatives.
The 3F5B2SC and 4M5B2SC samples were dissolved in acetone and a supersaturated solution
was obtained at ambient temperature. The prepared solutions were filtered and filtrate was collected in the
beaker. The beaker was warmed and kept undisturbed in the dust free laboratory environment. The beaker
top was closed with paper to avoid quick evaporation. The defect free and good quality seed crystals were
Page 4 of 42

selected for single crystal XRD analysis. The well known slow evaporation technique was used to grow
large size crystals from seed crystals [20]. The grown single crystals of 3F5B2SC and 4M5B2SC are
shown in Fig. 2.
(a)
(b)
Fig. 2. Single crystals of (a) 3F5B2SC and (b) 4M5B2SC.
2.2. Characterisation
Crystal structures of 3F5B2SC and 4M5B2SC were determined by single crystal X-ray diffraction
method at room temperature. Each single crystal was mounted on a glass fiber with epoxy cement. X-ray
measurement was carried out using Bruker APEX II DUO CCD area detector diffractometer with graphite-
monochromated Mo Kα radiation (0.71073 Å). The sample-to-detector distance is 5 cm. The collected raw
data were reduced by using SAINT program [21] and empirical absorption correction was applied by using
SADABS program [21]. Both structures were solved by direct methods and refined by full-matrix least-
squares techniques by using SHELXTL software package [22, 23]. All non-hydrogen atoms were refined
with anisotropic displacement coefficients. All hydrogen atoms were positioned geometrically and assigned
isotropic displacement coefficients with a riding model, Uiso (H) = 1.2 Ueq (C) or 1.5 Ueq (C). The methyl
group of 4M5B2SC was applied with a rotating group model (AFIX 137). The crystal 3F5B2SC was
refined as a 2-components inversion twin with structure parameter of 0.55 (2). Molecular graphics and
publications materials were prepared by Mercury [24] and PLATON [25]. The intermolecular interaction
energies [26] were calculated using Crystal Explorer version 17.5 [27] at HF/3-21G level of theory. Crystal
data, data collection and structure refinement details are summarized in Table 1.
Page 5 of 42

Table 1. Crystallographic data and structure refinement for 3F5B2SC and 4M5B2SC.
Compound
3F5B2SC
1897984
C13H8BrFOS
311.16
4M5B2SC
1897986
C14H11BrO2S
323.20
CCDC deposition number
Molecular formula
Molecular weight
Crystal system
Space group
a (Å)
Monoclinic
P21
Monoclinic
Pc
3.9815 (6)
10.7217 (15)
14.728 (2)
96.286 (2)
624.92 (16)
2
4.0500 (4)
16.0451 (15)
10.1569 (9)
96.114 (2)
656.27 (11)
2
b (Å)
c (Å)
β (°)
V (Å3)
Z
Dcalc (g cm-3)
Crystal dimensions (mm)
Crystal colour, shape
µ (mm-1)
1.654
1.636
0.39 × 0.37 × 0.14 0.41 × 0.19 × 0.16
Yellow, plate
3.45
Yellow, block
3.28
Radiation, λ (Å)
Tmin, Tmax
Mo Kα, 0.71073
0.129, 0.214
9732
Mo Kα, 0.71073
0.228, 0.282
7775
Measured reflections
hkl range
−5 ≤ h ≤ 5
−14 ≤ k ≤ 14
−19 ≤ l ≤ 19
1.4–28.1
−4 ≤ h ≤ 4
−19 ≤ k ≤ 19
−12 ≤ l ≤ 12
2.4–25.0
2247
θ limit (°)
Unique reflections
3035
Observed reflections [I > 2σ(I)] 2273
2150
Parameters
149
164
Goodness of fit on F2
R[F2 > 2σ(F2)], wR(F2)
1.04
1.06
0.059, 0.177
0.022, 0.054
The IR spectrum of the synthesised 3F5B2SC and 4M5B2SC chalcones were obtained from FT-IR
1
13
spectrometer (Nicolet 5700). The molecular structure was further verified by H and C NMR spectrum
using 400 MHz NMR spectrometer (JNM-ECZ4005, JOEL). Using UV-Vis-NIR spectrophotometer V670
Page 6 of 42

was used to record the absorption spectrum. The melting point and thermal proficiency were analysed
using Differential Scanning Calorimeter (DSC Q20) and TGA/DTA analyser (SDT Q600) at a heating rate
of 100C /min in nitrogen atmosphere. The classical powder technique developed by Kurtz - Perry [28] was
used to evaluate SHG conversion efficiency of these samples. The beam energy of the Nd:YAG laser
operating at 1064 nm with 3.7 mJ/pulse beam energy, pulse width of 10ns and a repetition frequency of
10Hz was applied to the upgraded microcrystalline powder samples 3F5B2SC and 4M5B2SC which were
tightly packed in a glass capillary.
The beam energy of the Nd: YAG laser operating at 1064 nm with 3.7 mJ/pulse beam energy, pulse
width of 10 ns and a repetition frequency of 10Hz was applied to the upgraded microcrystalline powder
samples 3F5B2SC and 4M5B2SC which were tightly packed in a glass capillary. The Z-scan experiment
was performed using a 532 nm and 200 mW continuous wave diode-pumped solid-state laser, which was
focused by a 28.6 cm focal length lens. The laser beam waist at the focus was measured to be 0.242 m,
the Rayleigh length was 3.46 mm and laser beam input intensity at the focus 2.14X108 W/m2.
2.3. Computational details
The 3F5B2SC and 4M5B2SC are theoretical studied with the help of Gaussian 09 [29] program
package and all the images and graphs are viewed by Gauss view 5.0 program [30]. The molecular
structures are optimized and further these optimized structures are used to compute FTIR and NMR (1H
and 13C) spectrum using B3LYP/6-311+G(d,p) by DFT method. The molecular electrostatic potential
(MEP) of both molecules are plotted using the same level of theory. The electronic absorption spectrum,
major contribution of electronic orbits in the electron transition, global chemical reactivity descriptor
(GCRD), HOMO-LHMO energies and energy gap are calculated with TD-DFT at same level of theory.
The NBO analysis is done with the help of NBO 5.0 Program included in the Gaussian 16. The nonlinear
optical parameters such as static dipole moment (μ), static and dynamic polarizability (α) and static and
dynamic first order hyperpolarizability (β) are calculated by B3LYP/6-311+G(d,p) method with DFT [31].
using Gaussian 09. The static and dynamic second order hyperpolarizability (γ) is calculated by time
dependent Hartree Fock theory (TDHF) with 6-31G method using GAMESS program package [32]. The
dipole moment, polarizability, first and second hyperpolarizability are computed using x, y and z
components are defined by [33, 34].
(1)
(2)
√
Page 7 of 42

(3)
(4)
(5)
√
√
√
3. Results and discussions
3.1. Single crystal X-ray diffraction
The asymmetric unit of 3F5B2SC and 4M5B2SC are shown in Fig. 3. Both compounds are
crystallized in the non-centrosymmetric monoclinic crystal system having different space group (P21 for
3F5B2SC and Pc for 4M5B2SC). The structure of both molecules meta-substituted fluoro group for
3F5B2SC and para-substituted methoxy group for 4M5B2SC closely resemble each other with molecule
overlay RMSD of 0.0584 Å and maximum deviation of 0.1161 Å. Both molecules exist in an trans
configuration with reference to their C6═C7 double bond as recorded by the C5—C6═C7—C8 torsion
angle of -177.1(8)° and -178.3(4)° for 3F5B2SC and 4M5B2SC, respectively. The thiophenyl ring
(S1/C1–C4) of 3F5B2SC and 4M5B2SC are almost co-planar to their corresponding phenyl ring (C8–
C13) with dihedral angles of 4.1(5)° and 3.4(2)°, respectively. The planarity of 4M5B2SC is marginally
greater than 3F5B2SC as signaled by its smaller RMS deviation of least-squares mean plane (excluding H
atoms), i.e. 0.0683 Å for 3F5B2SC and 0.0452 Å for 4M5B2SC.
Both compounds show one-dimensional structural similarity. The hydrogen bonded chains with
graph-set motifs are created via intermolecular C3—H3A···O1 hydrogen bonds (Table 2) in side by
side fashions. However, the C3—H3A···O1 hydrogen bonds in 3F5B2SC are considered as weak
intermolecular interaction due to its longer H···O distance of 2.69 Å. In crystal 3F5B2SC (Fig. 4a), in
addition these chains are connected into two-dimensional corrugated sheet, parallel to (101) plane via
Br1···F1 short contacts [d = 3.319(7) Å) which is shorter than the sum of van der Waals radii of bromine
and fluorine (3.32 Å)]. In crystal 4M5B2SC (Fig. 4b), the bromine atoms form short contact with oxygen
atom of methoxy groups [d = 3.219 (3) Å, which is shorter than the sum of van der Waals radii of Br and O
̅
(3.37 Å)], linking these hydrogen-bonded chains into two-dimensional linear sheet, parallel to plane.
Both crystal structures are consolidated by weak parallel-displaced π···π interactions [Cg1···Cg1 =
3.982(4) Å, Cg2···Cg2 = 3.982(7) Å and 3.981(7) Å in 3F5B2SC (Fig. 5a); Cg3···Cg3 = 4.050(3) Å and
Cg4···Cg4 = 4.050(3) Å in 4M5B2SC (Fig. 5b)] with symmetry code of -1+x, y, z and 1+ x, y, z. Cg1 and
Cg3 are centroid of S1/C1–C4 thiophenyl rings, Cg2 and Cg4 are centroid of C8–C13 phenyl rings.
Page 8 of 42

(a)
3F5B2SC
(b) 4M5B2SC
Fig. 3. ORTEP diagram of asymmetric unit of (a) 3F5B2SC and (b) 4M5B2SC shown in 50% probability
displacement ellipsoids with labels for non-hydrogen atoms.
Page 9 of 42

(a)
3F5B2SC
(b)
4M5B2SC
Fig. 4. Partial crystal packing of (a) 3F5B2SC and (b) 4M5B2SC viewed along a-axis shows a two-
dimensional layer with C—H···O hydrogen bonds (cyan lines) and Br···F/O short contacts (magenta lines).
Page 10 of 42

(a)
3F5B2SC
(b)
4M5B2SC
Fig. 5. Partial crystal packing of (a) 3F5B2SC and (b) 4M5B2SC, showing three separated layers in
contrast colours with intermolecular π···π interactions (purple dashed lines). Hydrogen atoms not involving
in the packing of the molecules have been omitted for clarity.
Table 2 Hydrogen-bond geometry (Å)
Compound D—H···A
D—H
0.93
H···A
2.69
D···A
D—H···A
128
Symmetry code
−x+2, y−1/2, −z+1
x+1, −y+1, z+1/2
C3—H3A···O1
C3—H3A···O1
3.345 (10)
3.416 (5)
3F5B2SC
4M5B2SC
0.93
2.54
158
Page 11 of 42

3.2. Geometry optimization and vibrational analysis
The vibrational analysis of molecules 3F5B2SC and 4M5B2SC are done by experimental IR spectrum
and computed IR spectrum of optimized structure. The geometry optimization of these molecules are done
by DFT. The optimized structures with labelled atomic symbols and numbers are displayed in Fig. 6. The
bond lengths, bond angles and dihedral angles of both chalcones calculated by DFT and experimental XRD
data are in close agreement.
3F5B2SC
4M5B2SC
Fig. 6. Geometry Optimized molecular structure of 3F5B2SC and 4M5B2SC using B3LYP/6-311+G (d, p)
level theory.
The recorded IR spectrums of the synthesised compounds and computed IR spectrum by DFT
method are shown in Fig. 7. The difference between experimental and computed vibrational modes is
observed. These small differences due to the experimental vibrations results are in solid phase but
theoretical calculations are in the gaseous phase. It is clear that unscaled wave numbers are higher than the
experimental wavenumber because of approximate nature of quantum mechanical method. The unscaled
wave numbers are scaled down by a uniform scaling factor 0.967 [35] and know the scaled and
experimental wave numbers are in close agreement. The comparison of experimental and calculated
vibrational assignment of 3F5B2SC and 4M5B2SC are shown in Tables 1S and 2S (see supplementary
information).
Phenyl ring vibrations
The wavenumber range of 3000-3120 cm-1 were reported for aromatic CH stretching modes [36]. The CH
stretching modes of 3F5B2SC molecule is calculated in the range 3100-3073 cm-1by DFT method and
observed experimental values in the range 3079-3057 cm-1. The CH stretching modes of 4M5B2SC is
computed in the 3105-3043 cm-1 range band observed experimental value in 3084-3057 cm-1 range by IR.
Page 12 of 42

The in-plane and out-of-plane CH bending were reported in the literature at wavenumber range 1300-1000
cm-1 and 1000-700 cm-1 [37]. In this present report CH in-plane bending modes of 3F5B2SC molecule is
calculated in the range 1471-1064 cm-1 (DFT) and 1445-1103 cm-1 (IR spectrum). The assigned
wavenumber range for CH in-plane bending modes of 4M5B2SC molecule is 1492-988 cm-1 and observed
IR experimental value 1492-974 cm-1. The 3F5B2SC molecule CH out-of-plane bending modes calculated
by DFT in the range 954-769 cm-1and experimental IR spectrum avenumber range 941-844 cm-1. The CH
out-of-plane bending modes of 3F5B2SC molecule is calculated in the range 945-414 cm-1 and observed
experimental value in the range 817-426 cm-1.Thecalculatedwave numbers range 1595-982 cm-1and
experimental wave numbers range 1617-989 cm-1 assigned to the 3F5B2SC molecule corresponds to the
aromatic CC stretching vibrations. The calculated wave numbers range 1594-1620 cm-1and experimental
wave numbers range 1611-1032 cm-1 assigned to the 4M5B2SC molecule corresponds to the aromatic CC
stretching vibrations. The CCC in-plane bending was reported in the range 1000–600 cm-1 [38]. The CCC
out-of-plane bending was repoted at 739 and 571 cm-1.The 3F5B2SC molecule CCC in-plane bending
modes calculated by DFT in the region 982-507 cm-1 and experimental IR spectrum values in the range
941-505cm-1. The computed and observed experimental CCC in-plane bending modes of 4M5B2SC
molecule is 988-565 cm-1 and 974-697 cm-1 range respectively.In the present work 3F5B2SC molecule
shows theoretical CCC out-of-plane bending vibrations at wave numbers656, 440 cm-1 and experimental
CCC out-of-plane bending vibrations at wave numbers667, 444 cm-1. The 4M5B2SC contributes
calculated CCC out-of-plane bending vibrations at wavenumber range 945-414 cm-1and is in agreement
with experimental values in the wavenumber range 739-426 cm-1.The calculated vibrations by DFT method
experimental IR spectrum are in good agreement.
Thiophene ring vibrations
The CH stretching vibrations were reported in the wavenumber region 3133-3076 cm-1 [39]. In this report
CH stretching modes of 3F5B2SC molecule calculated at wavenumber3118, 3105 cm-1by DFT method and
observed experimental value at3105 cm-1 with PED 100%. The CH stretching modes of 4M5B2SC
molecule is calculated at wavenumber 3118, 3104 cm-1 and observed IR value at 3100 cm-1. The CH in-
plane and out-of–plane bending vibrations were reported earlier in the wavenumber region 1260-960 cm-1
and 990-680 cm-1 [40] respectively. The 3F5B2SC shows theoretical CH in-plane bending vibrations in the
range 1508-1056 cm-1 and experimental vibrations are in the range 1486-1076 cm-1. The 4M5B2SC
contributes calculated CH in-plane bending vibrations at wavenumber range 1510-1055 cm-1 and is in
agreement with experimental values in the 1509-1032 cm-1. Here the present work 3F5B2SC molecule
shows theoretical out-of–plane CH bending vibrations at 868,779 and 539 cm-1 and experimental vibrations
are observed in the wave number 796 cm-1. The 4M5B2SC contributes calculated out-of–plane CH
bending vibrations at wavenumber 931, 777 and 540 cm-1 and is in agreement with experimental values in
Page 13 of 42

the wavenumber 926, 866 and 878 cm-1. The aromatic CC stretching was reported the range between 1650
and 1200 cm-1. The 3F5B2SC molecule CC stretching modes calculated by DFT in the region1508-1056
cm-1 and experimental values in the range 1486-1076 cm-1. The CC stretching bending modes of
4M5B2SC molecule is calculated in the range 1510-1055 cm-1 and observed experimental value in the
range 1509-1198 cm-1. The CCC in-plane bending was observed in the range 1000–600 cm-1. In this
present report calculated wave numbers in the range 1219-705cm-1and experimental wavenumber range
1103-723 cm-1corresponding to the CCC in-plane bending of 3F5B2SC molecule. The calculated wave
numbers in the range 1177-720cm-1and experimental wavenumber range 974-697cm-1corresponding to the
CCC in-plane bending of 3F5B2SC molecule. The calculated wave numbers at 868,539cm-1and
experimental wavenumber range 565cm-1corresponding to the CCC out-of-plane bending of 3F5B2SC
molecule. The calculated wave numbers in the range 866, 540cm-1and experimental wavenumber range
878cm-1corresponding to the CCC out-of-plane bending of 3F5B2SC molecule. The CS stretching
vibrations were reported at 700 and 622 cm-1 [41]. The molecule 3F5B2SC shows calculated CS stretching
at 965, 934, 718 and 657 cm-1 and 3F5B2SC molecule shows calculated CS stretching vibration at 931,
717 and 653 cm-1. The CS bending vibration calculated by DFT at 965, 779, 657 and453cm-1 for
4M5B2SC and for 3F5B2SC at 966, 866, 777, 697 and 653 cm-1. The experimental CS stretching and CS
bending vibrations obtained from IR spectrum for 3F5B2SC molecule in the range 989-444 cm-1and for
4M5B2SC molecule in the range 974-477cm-1. The calculated values obtained from DFT method and
experimental values obtained from FTIR spectrums are compared and indicates the experimental and
theoretical values are in close agreement [18, 41-42].
Carbonyl vibrations
The presence of carbonyl group (C=O) confirms the structure of the chalcones. The C=O stretching
vibration was reported in the region 1715-1600 cm-1 [43]. In this investigation C=O stretching vibration
at1649 cm-1 (DFT) and 1650cm-1(experimental)is assigned to 3F5B2SC and at 1641 cm-1 (DFT) and
1644cm-1(experimental) is assigned to 4M5B2SC.
Other vibrations
According to literature C=C stretching mode was at about 1600 cm-1 [37]. Here the C=C stretching
vibration in conjugation with C=O shows the vibration at 1582cm-1(calculated) and 1593cm-
1(experimental) for 3F5B2SC. The C=C stretching vibration in conjugation with C=O shows the vibration
at 1569 cm-1(calculated) and 1587cm-1(experimental) for 4M5B2SC.The molecules 3F5B2SCshows C-Br
(thiophene ring) stretching vibration at 934, 464cm-1 (DFT) and 463 cm-1 (experimental). The 3F5B2SC
molecule shows C-Br (thiophene ring) stretchingvibration931, 448cm-1 (DFT) and 926, 460cm-1
(experimental).The molecules 3F5B2SC shows C-F (benzene ring) stretching vibrations at 1221, 1122, 507
Page 14 of 42

cm-1 (DFT) and 1221, 505cm-1 (experimental). The molecules 3F5B2SC show C-F (benzene ring)
stretching vibrations at 464cm-1 (DFT) and 463 cm-1 (experimental).
Methoxy group vibrations
The methoxy group of 4M5B2SC has CH symmetric stretching vibrations at higher wavenumber range
3000-2925 cm-1 and CH asymmetric stretching vibration in the lower wavenumber range 2870-2825 cm-1
[44,45]. The experimental band at 3033 cm-1 and theoretical band at 3036 cm-1 alloted to symmetric
stretching vibrations whereas the experimental band at 3004, 2933 cm-1 and theoretical band at 2971, 2912
cm-1 alloted to asymmetric stretching vibrations. According to literature [46, 47] the bending vibrations of
methyl group are in the range 1465-1440 cm-1 and 1390-1370 cm-1 respectively. The in-plane CH bending
vibrations are at wavenumber 1453, 1444, 1427, 1163 cm-1 (theoretical) and 1463 and 1130 cm-1
(experimental). The CH3 out of plane modes along with inplane bending modes experimentally observed at
1463 and 1130 cm-1 and computed at 1453, 1444, 1163 and 1169 cm-1
Page 15 of 42

100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
3F5B2SC
4M5B2SC
-10
-10
4000 3500 3000 2500 2000 1500 1000 500
Wavenumber (cm-1)
4000 3500 3000 2500 2000 1500 1000 500
Wavenumber (cm-1)
0
200
0
3F5B2SC
4M5B2SC
200
400
600
400
600
800
1000
1200
1400
1600
1800
2000
800
1000
1200
4000 3500 3000 2500 2000 1500 1000 500
Wavenumber (cm-1)
4000 3500 3000 2500 2000 1500 1000 500
Wavenumber (cm-1)
Fig. 7. Comparison between experimental and theoretical (B3LYP/6-311+G(d,p)) IR spectrum..
Page 16 of 42

3.3. Proton and carbon NMR studies
Proton and carbon NMR spectrum of the compounds were taken by dissolving samples in
chloroform. The nuclear magnetic resonance (NMR) was calculated using gauge independent atomic
orbital (GIAO) at B3LYP/6-311+G (d, p). The standard chemical shift was observed with tetramethylsilane
(TMS) as reference material at B3LYP/6-311+G(2d,p) method. The experimental and theoretical (DFT)
peaks observed in the spectrum are compared (Figs. 8a and 8b). The protons and carbons present in both
structures are identified to confirm the molecular structure formation of both chalcones. The Table 3 shows
the co-relation between experimental and DFT chemical shift values, assigned to peak. The interaction
between neighboring nuclei and degeneracy from magnetic field applied leads to multiple peaks in the
experimental spectrum.
Theoretical
1H NMR
3F5B2SC
4M5B2SC
9
8
7
6
5
4
3
8.0
7.8
7.6
7.4
7.2
7.0
6.8
ppm
ppm
Experimental
1H NMR
4M5B2SC
3F5B2SC
7.8
7.6
7.4
7.2
7.0
6.8
ppm
8.0
7.8
7.6
7.4
ppm
7.2
7.0
6.8
7.0 6.8 6.6 6.4 6.2 6.0 5.8 5.6 5.4 5.2 5.0 4.8 4.6 4.4 4.2 4.0
ppm
Fig. 8a. Experimental and theoretical 1H NMR spectra of 3F5B2SC and 4M5B2SC.
Page 17 of 42

Theoretical 13C NMR
3F5B2SC
4M5B2SC
190
180
170
160
150
140
130
120
110
190 180 170 160 150 140 130 120 110 100 90 80 70 60 50
ppm
ppm
Experimental 13C NMR
4M5B2SC
3F5B2SC
180 170 160 150 140 130 120 110 100 90 80 70 60 50
180
170
160
150
140
130
120
110
ppm
ppm
Fig. 8b. Experimental and theoretical 13C NMR spectra of 3F5B2SC and 4M5B2SC.
Table 3.
The calculated and experimental chemical shifts of 3F5B2SC and 4M5B2SC.
3F5B2SC
Experimental
4M5B2SC
Experimental
Proton type
(1H)
Proton type
(1H)
DFT
DFT
5H
7.8997
7.8204
7.512
7.774
19H
8.022
7.929
7.539
7.479
7.248
7.106
6.936
6.643
4.013
3.601
3.6
7.807
21H
7.736
6H
7.767
9H
7.587, 7.578
7.366, 7.357
7.301
23H
7.576
25H
7.473
10H
7.561, 7.555
7.248
22H
7.4187
7.2843
7.1549
6.9713
4H
15H
7.263
26H
7.194, 7.189
7.156, 7.122,
6.925, 6.904
3.836
18H
7.143, 7.131
6.983
12H
11H
25H
21H
29H
3.71
22H
3.71
Carbon
Carbon type
3F5B2SC
4M5B2SC
Page 18 of 42

type (13C)
1C
DFT
Experimental
180.657
164.34
(13C)
1C
DFT
Experimental
180.793
181.96
172.67
161.5
182.48
169.1
16C
7C
17C
8C
161.983
164.062
161.887
146.911
143.194
136.879
136.803
162.69
157.81
148.19
140.94
133.95
132.82
131.11
130.84
122.89
115.71
111.83
55.19
158.313
12C
4C
159.62
147.4
13C
5C
158.303
147.448
13C
19C
10C
8C
142.82
134.54
134.11
131.74
125.03
124.05
121.93
120.02
15C
11C
14C
144.65, 144.535
131.744, 131.523
131.389, 131.245
130.469, 130.699
129.099, 127.327
122.45
137.156, 131.552 18C
14C
20C
17C
3C
126.412
124.759
121.379
121.76
9C
24C
3C
114.554
16C
20C
113.769
55.523, 55.235
3.4. Thermal studies
The DSC plot (Fig. 9) displays a sharp peak at 81°C for 3F5B2SC and 141°C for 4M5B2SC. These
sharp irreversible endothermic transitions produced reveal the melting point of the samples. The curves
indicate that both samples are in the same phase before reaching the melting point. The sharpness in the
peak produced by both samples indicates better crystalline nature and purity.
In the plotted TGA/DTG/DTA curves of these samples, peak produced by DTA curve is in good
agreement with peak observed by DSC curve confirms the exact melting point of these samples. In the
TGA curve, sample 3F5B2SC is stable upto temperature 240 0C and then weight loss is about 81.55%
upto the temperature 303 °C (Fig. 10a), 4M5B2SC is stable up to the temperature 276 °C and the
temperature changes in the region 276 to 317 °C, the weight loss observed is 95.42% (Fig. 10b). The
weight loss within these temperatures is due to evaporation and does not correspond to self-degradation
0
0
of the samples. The TGA and DTG curves coincide at 240 C (3F5B2SC) and 276 C (4M5B2SC)
0
shows stability of these compounds upto this temperature. The DTG curve exothermic peak at 277 C
(3F5B2SC) and 309 0C (4M5B2SC) indicates the weight loss due to evaporation and degradation. The
0
0
peak observed in the DTA curve at 277 C (3F5B2SC) and 309 C (4M5B2SC) is in agreement with
peak observed by DTG curve at the same temperature. These curves indicate that both the compounds
Page 19 of 42

are stable before the melting point and remain in the same phase [10]. The thermal stability of these
compounds prompts us that these chalcones can be used as a material for optical applications.
4
3
3F5B2SC
4M5B2SC
2
1
0
-1
-2
81 0C
141 0C
0
50
100 150 200 250 300
Temperature (0C)
Fig. 9. DSC curve of 3F5B2SC and 4M5B2SC chalcones
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
120
277 0C
0.6
3F5B2SC (a)
100
0.4
240 0C
80
60
40
20
0
TGA curve
DTA curve
DTG curve
0.2
0.0
303 0C
-0.2
-0.4
-0.6
-20
0
100 200 300 400 500 600 700 800 900 1000
Temperature (0C)
Page 20 of 42

0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
120
100
80
60
40
20
0
309 0C
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
4M5B2SC
(b)
TGA curve
DTA curve
DTG curve
276 0C
317 0C
-20
0
100 200 300 400 500 600 700 800 900 1000
Temperature (0C)
Fig. 10. TGA/DTA/DTG curve of (a) 3F5B2SC and (b) 4M5B2SC chalcones
3.5. Linear Optical properties and optical energy gap
The recorded experimental absorption curve of 3F5B2SC and 4M5B2SC are depicted in Fig. 11. The
maximum absorption observed at 242 and 329 nm for 3F5B2SC and 248 and 352 nm for 4M5B2SC are in
the UV region. The absorption peaks observed from the experimental graph is in close agreement with
theoretically calculated absorption peaks from DFT method. The calculated absorption peaks in the
gaseous phase are at 243 and 346 nm for 3F5B2SC and 260 and 366 nm for 4M5B2SC. These observed
peaks prove the n-π* and π-π * transitions and the existence of carbonyl group. In general transparency in
the visible region is a characteristic feature of these chalcones and can be used as a NLO material [11]. It is
clear from the figures that given samples have observed and calculated lower optical cut-off at 400 and 430
nm by 3F5B2SC and 420 and 450 nm by 4M5B2SC respectively and produces transparency in the
remaining region. The experimental and theoretical absorption peak and cut-off wavelength values are very
close. The experimental values taken in the liquid medium and computations in the gaseous phase leads to
difference in the values. The π-π * transition attributed to HOMO-LUMO transitions.
Page 21 of 42

2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
35000
30000
25000
20000
15000
10000
5000
0
1.2
1.0
0.8
0.6
0.4
0.2
0.0
35000
30000
25000
20000
15000
10000
5000
0
l
l
= 366 nm
= 352 nm
abs
abs
l
= 346 nm
abs
4M5B2SC
3F5B2SC
l
= 329 nm
abs
Absorption spectrum
Calculated
Absorption spectrum
Calculated
Experimental
Experimental
l
= 400 nm
cutoff
l
= 420 nm
cutoff
l
= 430 nm
cutoff
l
= 450 nm
cutoff
200
300
400
500
600
700
800
200
300
400
500
600
700
800
Wavelength (nm)
Wavelength (nm)
Fig. 11. Theoretical and experimental UV-Vis-NIR absorption spectra of 3F5B2SC and 4M5B2SC
Table 4.
The excitation wavelength, energies, oscillator strength and major contribution for transition in 3F5B2SC
and 4M5B2SC molecules.
The excitation
Electronic
Oscillator strengths Major contributions of
Samples
Energy (eV)
wavelength (nm) transitions
fo
HOMO-LUMO orbital
374.81
347.03
318.34
369.091
367.13
317.99
S0
S0
S0
S0
S0
S0
S1 3.308
0
H-2
H
L (97%)
L (99%)
L (90%)
L (97%)
L (98%)
L (93%)
S2 3.573
S3 3.894
S1 3.359
S2 3.377
S3 3.899
0.7547
0.0552
0
F5B2SC
H-1
H-2
H
0.8773
0.1028
M5B2SC
H-1
Page 22 of 42

The optical band gap (Eg) of 3F5B2SC and 4M5B2SC were estimated by experimental absorption
data. The following relation is used to estimate band: αhν = A (hν - Eg)1/2
The optical band energy gap (Eg) was estimated by data obtained from experimental absorption
spectrum. A graph of (αhν)2 vs hν was plotted to estimate the direct optical band energy gap (Eg) from
Tauc’s plot [48]. The slated straight line was extrapolated and intercepted hν-axis at (αhν)2=0 and the value
thus obtained is Eg= 4.7 eV for 3F5B2SC and 4.2 eV for 4M5B2SC. The band gap values thus obtained as
the intercept of the linear fit of (αhν)2 with the abscissa (Fig. 12).
200
3F5B2SC, Eg = 4.7 eV
4M5B2SC, Eg = 4.2 eV
150
100
50
0
-50
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
E (eV)
Fig. 12. Tauc’s plot of 3F5B2SC and 4M5B2SC.
3.6. HOMO-LUMO, GCRD and MEP
The FMOs 3D plots of 3F5B2SC and 3F5B2SC molecules are as dispalayed in Fig. 13. The HOMO
(highest occupied molecular orbital) which can be considered as outer most orbital containing electron and
acts as electron donor. The LUMO (lowest unoccupied molwcular orbital) which can be considered as
inner most orbital containing free electrors and acts as electron acceptor. The HOMO-LUMO energy
difference is called energy gap. The energy gap between HOMO-LUMO (ΔE=EH-EL) for 3F5B2SC is 3.96
eV and 3F5B2SC is 3.69 eV. The energy gap between HOMO-1 and LUMO+1 (ΔE=EH-1-EL+1) for
3F5B2SC is 5.44 eV and for 3F5B2SC is 5.47 eV. The lower value of the energy is responsible for high
reactivity, chemical stability and ability of the molecule to transfer large number of electrons through π-
conjugation from ground state HOMO to excited state LUMO within the molecule leads to high value of
polarizability and hyperpolarizability and molecule acts as NLO active. The small HOMO-LUMO energy
gap means molecule is soft; higher HOMO-LUMO energy gap means molecule is hard. The transition of
Page 23 of 42

electrons from ground state (S0) to various excitation states (Sn) i.e. electronic excitation energies at various
energy levels, oscillator strength and major percentage contributions are calculated and present in the Table
4. The excitation energy (S0 → S2) for 3F5B2SC is 3.573 eV and for 3F5B2SC is 3.377 eV which is in
agreement with experimental energy gap. The major contribution of electron transition (99% for 3F5B2SC
and 98% 3F5B2SC) is from the ground state to first excited sate corresponds to the HOMO to LUMO
transition.
4M5B2SC
3F5B2SC
LUMO
LUMO
ΔE= 3.69 eV
ΔE= 3.96 eV
HOMO
HOMO
Fig. 13. HOMO-LUMO plots of 3F5B2SC and 4M5B2SC
The global chemical reactivity descriptor (GCRD) parameters correlate the chemical stability and
structure of the molecule [49, 50]. The HOMO and LUMO energy values of molecules are utilised to
compute Ionization potential (I=-EH) and Electron affinity (A=-EL). The electro negativity, χ = (I+A)/2
value is opposite to chemical potential, µ = -(I+A)/2. The electronically stable systems have negative
chemical potential values. The 3F5B2SC and 4M5B2SC have negative chemical potential values -4.86
and -4.395 eV respectively. The negative value of chemical potential indicates that both molecules are
stable and does not decompose into its constituent elements. The positive sign of chemical potential
indicate the auto-ionisation of the molecule and that leads to lower its energy. The chemical hardness (η)
and chemical softness (S) of both molecules are calculated by η = (I-A)/2= (EL- EH)/2 and S=1/2η
Page 24 of 42

calculated. The chemical hardness of 3F5B2SC and 4M5B2SC are 1.98 and 1.84 eV respectively
which are higher and hence both molecules are chemically stable. The higher value of energy gap
HOMO-LUMO indicates large value of chemical hardness and small value of energy gap indicates
smaller value of chemical hardness. The higher value of chemical hardness indicates that both molecules
are hard and chemically stable. The smaller value of chemical hardness indicates molecule is soft and is
more polarisable, because small energy required for excitation. The electrophilicity index, ω =µ2/2η of
3F5B2SC and 4M5B2SC are 5.96 and 5.23 eV respectively and the value is moderate, these values
indicate strong energy transformation between HOMO and LUMO. The computed values (Table 5)
confirm that both the chalcones shows good chemical stability and chemical strength.
Table 5
Global chemical reactivity descriptor (GCRD) of 3F5B2SC and 4M5B2SC.
χ
ω
EH
EL
EH-1
EL+1
(eV)
ΔE= EH-
EL (eV)
-3.96
I
A
µ
η
S
Samples
(eV)
(eV)
(eV)
(eV)
6.84
6.24
(eV)
2.88
2.55
(eV)
-4.86
-4.39
(eV)
1.98
1.84
(eV-1)
0.25
0.27
(eV)
4.86
4.39
(eV)
5.96
5.23
-6.84 -2.88
-6.24 -2.55
-7.06 -1.62
-6.75 -1.28
3F5B2SC
4M5B2SC
-3.69
Molecular electrostatic potentials (MEP) 3D mapping predict the electrophonic and nucleophilic
attack of the molecule. The MEP predicts the molecular size, molecular shape, molecular charge transfer,
molecular interaction and large macroscopic properties of the molecules. The electrostatic potential on
constant electron density surface is studied by well known MEP plots overlap on the total electron density
using DFT method in the gaseous phase. In the plot red colour represents the atoms with negative potential
due to high electron density promoting the site for elecrophilic attack. The blue colour in the plot
corresponds to the atoms with positive potential due to low electron density promoting the site for
nucleophilic attack [51,52]. As in Fig. 14. 3F5B2SC molecule negative electrostatic potential are localized
over the carbonyl group and halogen fluorine of phenyl ring. The positive electrostatic potential localized
over the proton of the molecule. In the 4M5B2SC molecule negative electrostatic potential are localized
over the carbonyl group. The positive electrostatic potential localized over proton of the molecule.
Page 25 of 42

3F5B2SC
4M5B2SC
Fig. 14. MEP plots of 3F5B2SC and 4M5B2SC
3.7. Nonlinear Optical Studies
3.7.1. Second order nonlinear optical properties
The 3F5B2SC and 4M5B2SC crystallizes in non-centrosymmetric space group and therefore both
must produce SHG. The second harmonic wave (532 nm) generated from the samples and urea were
detected by photomultiplier tube and converted into electrical signal. The converted electrical signal was
displayed on the oscilloscope as output signal (amplitude in volts). The output signal voltage displayed on
the oscilloscope by 3F5B2SC (275.6 mV) and 4M5B2SC (218.4 mV) as well as reference urea (52 mV)
were note down. The SHG potency of 4M5B2SC and 3F5B2SC are 5.3 and 4.2 times the urea
respectively. The SHG efficiency of 4M5B2SC is higher than some of the reported NLO molecules [17,
19, 53]. In general, a material with high SHG efficiency should have extensive π conjugation chain with
noncentro symmetric nature. Both electron donating and accepting groups, play a major factor in increasing
this type of conjugation and leads to delocalization of electrons and increases the first order
hyperpolarizability.
3.7.2. Third order nonlinear optical properties
The sample dissolved in DMF solvent (0.01 M) translate along the Z-axis which is the direction of
laser beam. The transmitted laser beam was collected by photo detector with aperture (closed aperture) to
prove the self-defocusing [54] and without aperture (open aperture) to measure the saturable absorption.
Fig. 15 gives the closed and open experimental normalized curves of 3F5B2SC and 4M5B2SC. The value
of nonlinear phase shift   is calculated by fitting the closed aperture experimental curve with theoretical
2
2
curve obtained from the equationT (Z )  1  (4 X  ) [( X
here X= Z/Z0, Z0 and Z are the
 1)( X  9)]
,
Rayleigh length and distance of the sample from the focus respectively. The nonlinear refractive index [55]
Page 26 of 42

⁄
in the equation here, Leff is
can be calculated by substituting this obtained value of
 
effective thickness , Io is intensity of the beam at the focus and k is wave vector. The nonlinear absorption
coefficient β is computed by fitting the experimental open aperture using the formula ⁄
2
2 . T
, here ΔT is the peak value of open aperture.
I o .Leff
Graphically determined n2 and β are substituted in the corresponding equations to enumerate the
real, imaginary and absolute value of the third-order nonlinear optical susceptibility ( χ3 ) and also second
order hyperpolarizability ( [56] according to the following relations.
2

o c 2 n o
2
cm
W
 4
Re  3 (esu )  10
n 2 (
)

(1)
 o c 2 n o 2 l
cm
W
 2
Im  3 ( esu )  10
 (
)
2
4
(2)
(3)
(4)
1 / 2
3
2
2



(Re(  3 ))  (Im(  3 ))

3

Where, N is the density of molecules in cm-3. The term f is the local field factor. The ground state
absorption cross section (σg) and excited state absorption cross section (σex) in cm2 are also calculated as
suggested in the literature [57] tabulated in Table 6 along with other nonlinear parameters. The studies
show that in both samples excited state absorption cross section is greater than ground state absorption
cross section (σex>σg)and it proves the reverse saturable absorption (RSA).
(a)
(b)
1.20
1.15
1.10
1.05
1.00
0.95
0.90
0.85
0.80
1.02
1.00
0.98
0.96
0.94
0.92
0.90
0.88
3F5B2SC
0.01 M
532 nm
Expt. data
Tht. fit
3F5B2SC
0.01 M
532 nm
Expt. data
Tht. fit
 =0.94X10-4 cmW-1
= 0.72
n2= - 3.8X10-9 cm2W-1
Io=2.17X108 Wm-2
-50 -40 -30 -20 -10 0 10 20 30 40 50
Z (mm)
-50 -40 -30 -20 -10 0 10 20 30 40 50
Z (mm)
Page 27 of 42

(c)
(d)
1.15
1.00
0.95
0.90
0.85
0.80
0.75
0.70
4M5B2SC
0.01 M
Expt. data
Tht. fit
1.10
1.05
1.00
0.95
0.90
0.85
532 nm
Expt.data
Tht. fit
4M5B2SC
0.01 M
532 nm
 =2.2X10-4 cmW-1
F = 0.51
n2= - 2.69X10-9 cm2W-1
I0=2.17X108Wm-2
-50 -40 -30 -20 -10 0 10 20 30 40 50
Z (mm)
-50 -40 -30 -20 -10 0 10 20 30 40 50
Z (mm)
Fig. 25. Open aperture (a & c) and closed aperture (b & d) Z-scan curve of 3F5B2SC and 4M5B2SC
chalcones.
Table 6
Third-order nonlinear parameters of 3F5B2SC and 4M5B2SC chalcones
n2
Chalcone (cm2 W-1)
x10-9
β
Reχ(3) Imχ(3)
χ(3)
γh
σg
σex
(cm W-1)
x10-4
0.94
2.2
(esu)
x10-7
1.43
0.98
(esu)
x10-7
0.26
0.64
(esu)
x10-7
1.46
1.17
(esu)
x10-27
3.91
3.18
(cm2)
x10-23
1.21
1.18
(cm2)
x10-20
0.76
2.13
2.07
1.42
3F5B2SC
4M5B2SC
Page 28 of 42

3.7.3. Computational Nonlinear optical studies
The microscopic origin of static and dynamic nonlinear behaviour at the molecular are studied
theoretically. The DFT and TD-HF theory is used to calculate tensor components of static dipole moment
(μtotal); static and dynamic polarizability (α); and static and dynamic hyperpolarizability (β and γ) at
different frequencies. The strong donor-acceptor configuration of the molecule results in large separation
between the charges and ground state dipole moment. The tensor components and total static dipole
moment is displayed in Table 7. The static dipole moment of the molecules 3F5B2SC and 4M5B2SC is
4.75 D and 5.35 D respectively. The static dipole moment of the molecules 3F5B2SC and 4M5B2SC is
3.5 and 3.9 times the urea respectively [18, 58].
Table 7
The electric dipole moment (μ) of 3F5B2SC and 4M5B2SC by DFT method .
Static dipole
Static dipole
Molecules
μx
μy
μz
moment (μtotal) a.u moment (μtotal) Debye
0.184007
1.826343
1.85825
0.000118 1.867338
0.000157 2.105539
4.75
5.35
3F5B2SC
4M5B2SC
-1.047744
The tensor x, y and z components of 3F5B2SC and 4M5B2SC molecules are used to obtain static
polarizability α(0; 0) at ω=0 and dynamic polarizability α(-ω; ω) at two different wavelengths are
computed ω=0.083790 (λ=544.16 nm), ω=0.042820 (λ=1064.8 nm) and are shown in the Table 8. The
static isotropic polarizability (α0) of 3F5B2SC and 4M5B2SC are 3.34X10-23 and 3.8X10-23 esu and static
anisotropic polarizability (Δα) of 3F5B2SC and 4M5B2SC are 3.81X10-23 and 4.65X10-23 esu respectively.
The static polarizability value of 4M5B2SC molecule is higher than 3F5B2SC. The dynamic polarizability
x, y and z components and also isotropic and anisotropic polarizability values are higher than static
polarizability values. Therefore polarizability depends on the incident frequencies. The dynamic
polarizability values decreases with increase in wavelength. The polarizability value is higher for
4M5B2SC compared to 3F5B2SC.
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