Structural, photoluminescence, physical, optical limiting, and hirshfeld surface analysis of polymorphic chlorophenyl organic chalcone derivative for optoelectronic applications

Article abstract of DOI:10.1016/j.molstruc.2021.130053

The polymorphic molecule of (E)-1-(thiophen-2-yl)-3-(4-chlorophenyl) prop-2-en-1-one (2AT4C) was synthesized and grown its single crystals using slow evaporation solution growth technique. The molecular geometry and its structural deviations are studied u

Full text of DOI:10.1016/j.molstruc.2021.130053

Journal of Molecular Structure 1232 (2021) 130053
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstr
Structural, photoluminescence, physical, optical limiting, and hirshfeld
surface analysis of polymorphic chlorophenyl organic chalcone
derivative for optoelectronic applications
a,∗
b
c
d
Haleshappa D , Raghavendra Bairy , Jayarama A , Ching Kheng Quah ,
e
f
Huey Chong Kwong , Parutagouda Shankaragouda Patil
a
Department of PG Physics, Sri Dharmasthala Manjunatheshwara College (Autonomous), Ujire 574240, India
Department of Physics, NMAMIT, Nitte, Karkala 574110, India
b
c
d
e
f
Department of Physics, Alva’s Institute of Engineering and Technology, Moodbidri 574225, India
X-ray Crystallography Units, School of Physics, Universiti Sains Malaysia, Penang, USM 11800, Malaysia
School of Chemical Sciences, Universiti Sains Malaysia, Penang, USM 11800, Malaysia
Department of Physics, K.L.E. Institute of Technology, Opposite to Airport, Gokul, Hubli 580030, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The polymorphic molecule of (E)-1-(thiophen-2-yl)-3-(4-chlorophenyl) prop-2-en-1-one (2AT4C) was syn-
thesized and grown its single crystals using slow evaporation solution growth technique. The molecular
geometry and its structural deviations are studied using single crystal x-ray diffraction method. Further,
for the 2AT4C molecule, the intermolecular interactions and the percentage of interactions using 2D fin-
gerprint plots were analyzed by Hirshfeld surface analysis. The FT-IR and FT-Raman spectroscopic tech-
niques confirm the presence of bonding, stability of coordination compounds, and material validation. The
physical properties of 2AT4C crystal have been discussed using simultaneous TG/DTA/DSC thermal anal-
ysis and the vicker’s microhardness test. Their physical stability in terms of melting point and vicker’s
Received 7 December 2020
Revised 27 January 2021
Accepted 28 January 2021
Available online 4 February 2021
Keywords:
Polymorphism
Photoluminescence
Microhardness
NLO parameters
Optical limiting
Single crystal XRD
2
hardness number was found to be 131.02 °C and Hv=21kg/mm respectively. PL studies project the blue
light emission (378 nm) property of the grown crystal and UV-visible spectroscopic study reveals the
wide optical transparency in the entire visible region with an optical band gap 3.47 eV. The third order
nonlinear optical parameters such as nonlinear absorption coefficient, nonlinear refractive index, optical
susceptibility, and optical limiting threshold were measured using z-scan technique under CW regime.
The outstanding results of the various measures are confirms the potentiality of 2AT4C crystal for non-
linear and optoelectronic device applications.
©
2021 Elsevier B.V. All rights reserved.
1
. Introduction
tical possessions. In the field of medicine and photonics, a two-
photon absorption system is strongly desired [6,7]. However, be-
fore now, the ample amount of research was done on inorganic
materials, the researchers are able to classify their better physi-
cal characteristics, and they have demonstrated the inadequacy of
optical non-linearity problem that leads to the limitation in use of
electronic devices applications. The researchers have begun to con-
centrate on alternative materials to meet the requirement in order
to solve the above issue, so new material research comes into play
with organic materials such as crystalline films, self-assembled
multi-layer films, polymers and single crystals because their NLO
output potential is significantly higher than that of inorganic ma-
terials [8–10]. The most important criterion to be retained in the
NLO application domain for a material is high second and third
order NLO response, thermal and temporal stability, and proces-
sibility [11]. In particular, the research relied on third order non-
Currently, researchers are most intrigued by research in the
field of non-linear optical materials due to their excellent third-
order non-linearity, admitting that, the nonlinear optical (NLO)
materials were extensively considered as a pledging material in the
contemporary application domain viz optoelectronic devices, pho-
tonics, communication devices, and data processing [1–3], which
would afford the context for optical systems as well as photody-
namic therapy [4,5]. The forthcoming photonic engineering is re-
liant on the synthesis, design and the characterization of the ma-
terial unveiling, in particular second and third order nonlinear op-
∗
Corresponding author at: Department of PG Physics, Sri Dharmasthala Manju-
natheshwara College (Autonomous), Ujire, Karnataka 574240, India.
E-mail address: halesh.phy@gmail.com (H. D).
https://doi.org/10.1016/j.molstruc.2021.130053
0
022-2860/© 2021 Elsevier B.V. All rights reserved.

H. D, R. Bairy, J. A et al.
Journal of Molecular Structure 1232 (2021) 130053
linear optical parameters; especially positive nonlinear absorption
coefficient due to strong two photon absorption (TPA) and reverse
saturation absorption mechanism, negative nonlinear refractive in-
dex due to self-defocusing behavior of the nonlinear optical system
and greater third order optical susceptibility for all optical switch-
ing and limiting applications [1,12]. Organic molecules can be tai-
lored by substituting strong electron accepter and donor entities
in order to modify their optical nonlinearities through appropriate
structures of organic systems on the molecular level by means of
modern synthetic chemistry [13]. Recent investigations have shown
that derivatives of chalcone are excellent potential materials for
advanced NLO applications where they are coupled with materi-
als in a suitable approach. The effect of assimilating the functional
groups is attaining light localization that contributes to improved
NLO activity [3].
linker. In the present report, we have studied the polymorphic
nature of (E)-1-(thiophen-2-yl)-3-(4-chlorophenyl)prop-2-en-1-one
(2AT4C) derivative along with Hirshfeld surface analysis, photolu-
minescence, microhardness, third-order NLO susceptibility (χ(3)
)
and optical limiting property.
2. Experimental procedure and characterization
The polymorphic chlorophenyl chalcone derivative 2AT4C was
synthesized by following the Claisen–Schimidt condensation re-
action method [25]. The 2-acetylthiophene, 4-chlorobenzaldehyde,
and 5 ml (20% concentration) of NaOH non-aqueous solution is
mixed in a methanol solvent subsequently the mixture was stirred
for three hours in order to complete of the reaction. The synthe-
sized crude product was further filtered. The synthesis scheme of
the title compound (2AT4C) is shown in Fig. 1. In order to se-
lect a suitable solvent for single crystal growth, the extracted com-
pound was examined under the solubility test in different solvents
[26,27]. Acetone was identified as the solvent for single crystal
growth because of the moderate solubility rate. The synthesized
2AT4C compound was dissolved in an acetone solution, and the
non-aqueous solution was held in a dust free environment for sin-
gle crystal growth by means of slow evaporation solution growth
process by removing the dust particles through filtration [26,27].
After eight days, small nucleated crystals were observed and al-
lowed for well sized crystals to develop. The harvested 2AT4C
crystals (Fig. 2) are further marked by both destructive and non-
destructive processes.
Organic materials are extremely versatile in computer and
telecommunication technologies due to their integral high nonlin-
earity, synthetic versatility, and the ability to modify their prop-
erties by functional substitutions. Important rudiments relevant to
their future NLO applications are currently organic crystals with re-
silient third-order nonlinear optical absorption. Organic thiophen-
integrated molecules have attracted a lot of scientific and techni-
cal interest, especially because organic materials themselves have
been improved in the NLO response [14–16]. Organic NLO crystals
with aromatic rings have taken a great deal in the last few decades
because of their high non-linearity, fast response, and versatility
to tailor the aromatic molecules, while at the same time restrict-
ing the use of their devices, due to their weak physicochemical
strength, low mechanical strength and the cleavage trend. These
materials must imply an ability to show third-order NLO proper-
ties for a wide range of NLO applications when operating at 532
nm wavelength.
Both destructive and non-destructive experimental techniques
were used to characterize the grown single crystals of 2AT4C in
the present work. The synthesized 2AT4C derivative was tested
for elemental analysis, in order to validate the percentage com-
position of the elements present in 2AT4C using the Elementar
Vario EL III CHNS analyzer [27]. The 2AT4C compound functional
groups have been verified by FTIR and FT Raman spectral analysis.
The FT-IR spectra of the synthesized compound was collected in
Over the past two decades, so many researchers have mea-
sured the nonlinear optical susceptibility of different chalcone-
related materials and established the nonlinear susceptibility of
−22
(m/V ) 2 in these molecules [18]. The central problem in the
10
the region 400-4000 cm 1 on Avatar 370 FT-IR spectrometer fitted
−
design of new materials is realizing the role of the crystal struc-
ture in evaluating the physical properties of solids. Several poly-
morphic compounds were identified, in which the low tempera-
ture (LT) and high temperature (HT) phases can be stabilized at
ambient temperature based on the heat processing [19]. The abil-
ity of a substance to follow more than one crystal structure and
maintain the chemical composition offers a special opportunity to
research relations between crystal symmetry and different physi-
cal properties. In oligothiophene, a polymorphism might not only
occur from the backbone organization, as well as from the con-
formational changes of the pendant side chain, despite efforts of
chemically modified functional groups [20–22]. It is generally ac-
cepted that different crystal polymorphs and different conform-
ers may also have dissimilar spectral and NLO properties [11,23].
In light of variations in crystal packing of the same molecule, it
is crucial to analyze how the NLO properties are influenced by
these different crystal forms. Moreover, the use of alternative crys-
tallization process approaches such as zone melting, sublimation,
and solution crystallization has been shown to yield more NLO
effective compounds only [11]. Thiophene grounded chlorophenyl
chalcone derivatives are well known organic crystals which have
crystallized from its non-aqueous solution in different polymor-
phic forms in particular alpha (1α) and 2AT4C thiophene derivative
with KBr pellet technique using Thermo Nicolet and a DTGS de-
tector with 4 cm 1 resolution. Meanwhile, the FT-Raman spectrum
of 2AT4C was recorded in powder form using the BRUKER RFS 27
Stand-alone FT-Raman Spectrometer in the region 200-4000 cm-1
−
with 2 cm 1 resolution. The grown 2AT4C single was examined for
their structural information using BRUKER APEX II DUO CCD sin-
gle crystal X-ray diffractometer. The structural data of 2AT4C was
−
collected by irradiating the well-collimated Mo-Kα radiation with
wavelength 0.71 A˚ with the help of ϕ and ω scans [27]. The Cam-
bridge Crystallographic Data Centre with CCDC deposition num-
bers of 1834336 has been deposited with crystallographic data of
the recorded structures. Crystal data, data collection, and struc-
ture refinement details are summarized. The thermal characteris-
tics of the 2AT4C were carried out under a heating rate of 10 °C
per min in the temperature range 25 and 500°C using SDT Q600
V20.9 Build 20 simultaneous thermal analyzer. In device manufac-
turing, the hardness of the material plays a major role. In view of
the fact that CLEMAX- Digital microhardness tester MATSUZANWA-
Japan has been used to assess the crystal microhardness. The pho-
toluminescence analysis was carried out for the grown crystal in a
solution form by using JY FLUOROLOG-3 Spectrofluorometer in the
range of 300-450 nm with an excitation wavelength 310 nm. The
linear optical absorption and transmittance spectra was collected
in solution form in the wavelength range of 200-800 nm using Shi-
madzu 1800 UV–Vis–NIR spectrophotometer. The third-order NLO
characterization was performed using the standard Z-scan tech-
nique under continuous wave regime (Diode pumped solid state
laser). The experiment was carried out with an output power of
200 mW and wavelength 532 nm. The 1 mm pathway sample
crystallizes in centrosymmetric space groups P2 /c with different
1
lattice parameters. In recent years, the π-conjugated chlorophenyl
molecules with delocalized π -electron cloud organic derivatives
have been recognized as a class of organic materials in concern
of NLO applications due to their excellent NLO activity [3,24].
The possible charge transfer can takes place due to the interac-
tion between chlorophenyl and thiophene rings through carbonyl
2

H. D, R. Bairy, J. A et al.
Journal of Molecular Structure 1232 (2021) 130053
Fig. 1. Synthesis scheme of 2AT4C compound.
Table 2
FT-IR and FT-Raman vibrational assignments of 2AT4C.
IR (cm 1)
−
Raman (cm
−1
)
Assignments
3
1
1
1
1
9
-
080
647
586
409
088
76
3074
1642
1584
1408, 1413
1091
974
aromatic C–H stretching vibrations
C=O stretching vibrations
C=C stretching vibrations
C=C aromatic stretching vibrations
C–H aromatic stretching vibrations
CH=CH stretching vibrations
C–S stretching vibrations
862
8
09, 726
663
C=O in plane bending vibrations
Table 3
Crystallographic data and structure refinement for 2AT4C.
Compound
2AT4C
CCDC Number
1834336
Chemical formula
Molecular Weight
Crystal system, space group
C13H9ClOS
248.71
Monoclinic, P21/c
Temperature (K)
296
a, b, c ( A˚ )
6.0182 (12), 10.175 (2), 19.008 (4)
β (°)
94.194 (3)
V ( A˚ 3
)
1160.8 (4)
Z
4
Radiation type
Mo Kα
0.48
μ (mm 1)
−
Fig. 2. The grown single crystals of 2AT4C.
Crystal size (mm)
Diffractometer
0.49 × 0.41 × 0.18
Bruker APEX II DUO CCD
area-detector
Multi-scan SADABS
0.717, 0.779
Table 1
Percentage composition of 2AT4C compound.
Absorption correction
Tmin, Tmax
The percentage composition of the elements
No. of measured, independent 25375, 2671, 2192
Elements →
Carbon
Hydrogen
Oxygen
Sulphur
and
observed [I > 2_(I)] reflections
Experimental
Computed
61.98
62.78
3.71
3.65
6.39
6.43
12.71
12.89
Rint
0.027
sin θ/λ)max ( A˚ 1)
−
(
0.650
R[F2 > 2σ(F )], wR(F ), S
2
2
0.066, 0.210, 1.13
No. of reflections
2671
No. of parameters
No. of restraints
145
loaded quartz corvette was exposed to the intense laser beam, and
then the sample was scanned through a 286 mm focal length lens
along the Z-direction through the focus of the beam. The beam size
0
H-atom treatment
H-atom parameters constrained
0.78, -0.46
max, ꢀρmin (e A˚
−3
)
ꢀρ
7
−2
(
ω =38.74μm) and beam intensity (I = 8.48 × 10 Wm ) are
R1, wR2 [I > 2σ(I)]
0.065, 0.190
0
0
measured at the focus point (Z = 0).
R1, wR2 [all data]
0.077, 0.210
3. Results and discussions
limits. Therefore the CHNS analysis confirms the formation 2AT4C
chalcone derivative in the appropriate stoichiometric proportion.
The vibrational spectral analysis highlights some of the key in-
formation related to the existence of bonding, consistency of coor-
dination compounds and material confirmation. The recorded FT-
IR and FT-Raman spectra of 2AT4C compound are shown in Figs. 3
3
.1. CHNS, FT-IR and FT-Raman studies
The elemental analysis was carried out in order to measure
the percentage composition of synthesized 2AT4C elements, such
as carbon, hydrogen, nitrogen, and sulfur. The experimental results
and computed percentage compositions of carbon, nitrogen hydro-
gen, and sulfur of the synthesized compound 2AT4C are presented
in Table 1 and are closely interrelated within the allowable error
−
1
and 4 respectively. The weak characteristic peak at 3080 cm
in
IR spectra and at 3074 cm 1 in Raman spectra are assigned to aro-
−
matic C-H stretching vibrations of CH3 group that are most familiar
3

H. D, R. Bairy, J. A et al.
Journal of Molecular Structure 1232 (2021) 130053
Fig. 3. FT-IR Spectra of 2AT4C.
Fig. 4. FT-Raman Spectra of 2AT4C.
observation in chalcone derivatives. The strong vibrations are no-
conformation for both 1α and 2AT4C can be described by three
degree of freedom, which are the torsion angles between the thio-
phenyl ring and the carbonyl group S1–C4–C5–O1 (τ1); between
the carbonyl group and the olefinic double bond O1–C5–C6–C7
(τ2); and between the olefinic double bond 4-chlorophenyl ring
C6–C7–C8–C9 (τ3) (Table 4). In 1α, the aromatic rings are almost
coplanar with the adjacent carbonyl and olefinic double bond, as
τ1 and τ3 are 2.23˚ and 4.17˚, respectively. But, in 2AT4C τ1 and
τ3 are slightly twisted and settled at 7.82˚ and 7.92˚ separately.
Although the carbonyl double bond and olefinic double bond are
in s-cis conformation for both compounds, but τ2 in compound
ticed at 1586 cm 1 (IR) and 1584 cm (Raman) which are resem-
−
−1
ble to the C=C stretching vibrations in chlorophenyl ring [28]. The
−
1
strong peak at 1647 cm in the IR spectra reveals the C=O vibra-
tions of the carbonyl group [28]. The significant vibrational assign-
ments of FT-IR and FT-Raman of 2AT4C compound are recorded in
Table 2. The presence of functional groups, existence of chemical
bonding and molecular structure of the compound was verified by
all the subsequent observed vibrations.
3
.2. Structural information
1
α is deviated sparsely from the planarity (τ2 = 10.04˚); as τ2 in
compound 2AT4C is almost planar (τ2 = 4.66˚). In the overlay dia-
gram (Fig. 6), the skeleton of both the molecules is framed in terms
of molecular orientations and their deviations related to the vari-
ous angles of torsion (τ1, τ2, and τ3). The corresponding atoms of
the individual torsions are addressed in the previous paragraph. In
spite of the deviated torsion angels, aromatic rings for both com-
pounds are almost on the same plane as the dihedral angle for
the thiophenyl and 4-chlorophenyl rings are 6.35˚ (1α) and 6.67˚
As we know, the process in which various crystal structures are
demonstrated by the same chemical compound is polymorphism.
The first reported crystal structure of (E)-3-(4-chlorophenyl)-1-
(
thiophen-2-yl)prop-2-en-1-one (1α) [29]crystallized in the cen-
˚
trosymmetric monoclinic space group P2 /c [a = 5.7023 (3) A,
1
˚
˚
b = 13.3576 (8) A, c = 14.7017 (10) A, β = 96.735 (4)˚, Z = 4,
˚
Z’ = 1 and V = 1112.09 (12) A; Cambridge Structural Database
[
29]. In this article, we report the second polymorphic form of (E)-
(
2AT4C) individually. Altogether, the molecule of 2AT4C deviated
1
-(thiophen-2-yl)-3-(4-chlorophenyl) prop-2-en-1-one (2AT4C) and
only slightly from that of 1α, as indicated by a r.m.s. deviation of
compared its crystallography properties with those of 1α. Similar
to 1α, 2AT4C also crystallized in the centrosymmetric monoclinic
˚
0
.1694 A (excluding all H atoms) (Fig. 6).
The supramolecular analysis of both previously reported
space group P2 /c with different unit cell parameter (Table 3). The
1
[
29] polymorph (1α) and 2AT4C polymorph reveals the several
asymmetric unit of 1α and 2AT4C consist of a unique molecule
which constructed by a thiophen-2-yl ring, a 4-chlorophenyl ring
and a prop-2-en-1-one connecting bridge (Fig. 5). The structural
intermolecular interactions and there were no classical hydrogen
connections in both the polymorphs, so the intramolecular short
4

H. D, R. Bairy, J. A et al.
Journal of Molecular Structure 1232 (2021) 130053
Fig. 5. Molecular structure of 2AT4C with 30% probability displacement ellipsoids.
Fig. 6. An overlay representation for the molecules of 1α (red) and 2AT4C (blue). (For interpretation of the references to color in this figure legend, the reader is referred to
the web version of this article.).
Table 4
Selected torsional and dihedral angles (°) for compounds (1α [29] and 2AT4C)
Dihedral
1 represents the dihedral angle between the mean planes of thiophenyl and 4-
chlorophenyl rings.
Compound
S1–C4–C5–O1, (τ1)
O1−C5–C6–C7, (τ2)
C6−C7–C8–C9, (τ3)
Dihedral 1
1
2
α [29]
2.23
7.82
10.04
4.66
4.17
7.92
6.35
6.67
∗
AT4C
Table 5
Hydrogen-bond geometry.
D–H···A
D–H
H···A
D···A
D–H···A
Symmetry codes
∗
˚
2.56 A
˚
2.584 A˚
˚
C1–H1A···O1(2AT4C)
0.93 A
0.93 A˚
3.485(5) A
3.388(1) A˚
171 ˚
(–x),(1/2+y),(1/2–z)
(1–x),(1/2+y),(1/2–z)
C13–H13A···O1(1α)[29]
145.08 ˚
˚
for the realization of molecular projections and the associated 2D
fingerprint plots with high surface resolution for the investigated
compound through crystallographic information file. In order to
ascertain the intermolecular interactions along with the packag-
ing of the molecules within the structure, the dnorm plots with
color scales between -0.145 au (blue) and 1.042 au (red) and two-
dimensional fingerprint plots were plotted [31,32]. By using a red-
blue-white color outline, dnorm surface plots have been visualized
into the Hirshfeld surface, red spot portrays short contacts with
negative dnorm value, and blue region reflects long contacts with
positive dnorm value whereas white region represents contacts with
a dnorm value of zero around the sum of van der Waals separation
S···O contact (2.93 A) stabilizes the molecular conformation. The
crystal packing of the previously reported [29] polymorph (1α) is
fused through weak intermolecular C–H···O and π···π interactions.
In case of 1α polymorph the molecules are connected via C13–
H13A···O1 hydrogen bond forms a parallel head to tail dimer along
˚
c-axis (Fig. 7) with bond length H13A···O1=2.584 (1) A C13···O1=
˚
3
.388(1) A and angle between C13···H13···O1= 145.08 ˚. In the crys-
tal of 2AT4C, the molecules are connected by intermolecular C1–
H1A···O1 hydrogen bonds (Table 5) into a zig-zag chain parallel to
˚
b-axis (Fig. 8) With bond length H1A···O1=2.56 A C1···O1= 3.485
˚
A and angle between C1···H1A···O1= 171 ˚.
[
33]. In addition, TONTO has been used to measure electrostatic
3
.3. Hirshfeld surface analysis
potential, and a red and blue outline is applied to the electrostatic
potential analysis, since red shade spots the negative electrostatic
potential assists as hydrogen acceptor potential and the blue shade
vision represents the positive electrostatic potential assists as hy-
Hirshfeld Surface Analysis is a graphical tool for the visualiza-
tion of various intermolecular interactions in a three-dimensional
pictorial form. The Crystal Explorer 3.1 Software [30,31] was used
5

H. D, R. Bairy, J. A et al.
Journal of Molecular Structure 1232 (2021) 130053
Fig. 7. Intermolecular C–H···O hydrogen bond of 1α molecule forms a parallel head to tail dimer along c-axis.
Fig. 8. Intermolecular O–H···O hydrogen bond representation of 2AT4C molecule through partial packing diagram.
drogen donor potential. The ball and stick model, dnorm surface
plots and electrostatic potential plots of 2AT4C are presented in
Fig. 9. The H···H and H···C/C···H contacts are the greatest inhabited
contact and contribute 30.1% and 15.9% of the total intermolecu-
lar contacts (Fig. 10). However, H···H and H···C/C···H contacts ap-
pear to be a side-ways approach as the landfills of the pseudo-
(Fig. 11a) correspond to the C1−H1A···O1 hydrogen bonds. The in-
terpretation is validated by the associated electrostatic potential
plots, whereas O1 atom is a hydrogen acceptor with negative elec-
trostatic potential (red region, Fig. 11b). This C−H···O hydrogen
˚
bond appear as sharp spikes at de + d ≈ 2.4 A on the 2D finger-
i
print plots (Fig. 8). The percentage of contribution of H···Cl/Cl···H,
C···C and H···S/S···H contacts to the Hirshfeld surface are 12.2%,
9.7% and 9.1%, respectively for 2AT4C (Fig. 10). The absence of di-
˚
˚
reflected peak are shown at de ≈ d ≈ 2.4 A and de + d ≈ 3.0 A,
i
i
respectively. The red spots over the dnorm surface plots for 2AT4C
6

H. D, R. Bairy, J. A et al.
Journal of Molecular Structure 1232 (2021) 130053
Fig. 9. dnorm and electrostatic potential mapping in compound 2AT4C.
rect H···Cl/Cl···H and H···S/S···H interaction in the crystal structure
decomposition of the sample. A sharp peak corresponding to DSC
curve at 131.02°C in the thermogram indicates the melting point of
the compound. In both DTA and DSC curves no exothermic or en-
dothermic spikes are identified before the melting point this char-
acter of the sample implies the thermal stability of the crystal and
there is no phase transition before the melt.
of 2AT4C is indicated by the long range peaks of those contact
˚
which appear at the de + di ≈ 2.9-3.0 A. The high C···C contacts
contribution and the appearance of distinctive “triangle” engrossed
˚
at de ≈ d ≈ 3.6 A of the 2D fingerprint plots indicated the ex-
i
istence of intermolecular π···π interaction. In addition, the inter-
molecular π···π interaction are illustrated as red and blue “trian-
gle” on the shape-index surface (Fig. 12a) and uniform regions on
the curvedness surface (Fig 12b). The contribution percentages of
other intermolecular contacts are less than 10% in the Hirshfeld
surface mapping.
In the design of devices, the hardness of the material plays a
substantial role. Consequently, for the applied load (5–50 g) the
surface mechanical properties of the grown crystals were carried
out and vicker’s hardness number was calculated using the formula
[18]
ꢀ
ꢁ
P
d
Hv = 1.8544
kg
2
.
(1)
2
3
.4. Thermal and microhardness studies of 2AT4C crystal
mm
where, ’Hv’ → is the vicker’s hardness number
The data collected from the simultaneous TGA, DTA, and DSC
’
P’ → is the applied load
thermal analysis are depicted in Fig. 13. Initially, the reported ther-
mogram of the 2AT4C crystal is analyzed to understand the per-
centage of sample mass reduction at different temperatures associ-
ated with thermal stability and crystal decomposition. The exother-
mic peak of the DTA curve at 287°C, referring to the TG curve
weight loss, shows that the loss was due to the evaporation and
’
d’ → is the diagonal length of the impression.
It is easily noticed that the hardness number initially decreases
with load in the vicker’s microhardness plot (Fig. 14) and saturates
above 25 g of the applied load. The fractures began to appear at
the load of 25 g and extreme fractures across the indenter were
7

H. D, R. Bairy, J. A et al.
Journal of Molecular Structure 1232 (2021) 130053
Fig. 10. The 2-D fingerprint plots of 2AT4C.
8

H. D, R. Bairy, J. A et al.
Journal of Molecular Structure 1232 (2021) 130053
identified at 50 g load due to the release of the inner stress initi-
ated locally by indentation. The vicker’s microhardness number for
the grown 2AT4Ccrystal was found to be 21 kg/mm2 and we com-
pared the hardness value of 2AT4C crystal with the earlier reported
NLO crystals in literature [18].
3
.5. Linear optical studies
The absorption and transmittance spectra of 2AT4C were re-
ported in Fig. 15. The 2AT4C single crystal showed ample transmis-
sion in the entire visible and infra-red setting and the lower cut-
off wavelength for the 2AT4C crystal was found to be 364 nm. The
2
AT4C crystal transmission is responsible for increased crystalline
perfection. Many of the organic compounds shows the absorption
in the range 200-600 nm based on transition of an electrons from
∗
∗
n–π or π–π excited state. The maximum absorption peak ob-
∗
served at 322 nm are being assigned to the transition of n–π can
be attributed to excitation in the aromatic ring and C = O group
[34,35]. The optical band gap was measured for the 2AT4C crystal
using the Tauc’s equation [36]
2
(
αhϑ) = A(hϑ − Eg).
(2)
where ‘α’ is the absorption coefficient [27], ‘A’ is the band edge
constant and Eg is the optical band gap. The optical energy band
gap of the crystal 2AT4C was measured by the Tauc’s plot (Fig. 16)
(
αhϑ)2 v /s Eg and the band gap value was found to be 3.47 eV.
The value of obtained optical band gap and wide transparency in
the entire visible and IR region may be helpful for the NLO appli-
cation.
The measurement of photoluminescence is an indigenous non-
destructive and influential method of determining both the crys-
talline quality of a system and its fine exciton structure [37,38].
Photoluminescence in single crystals is a process in which light of
unique intensity excites the electronic states of system and releases
the excitation energy as light. The energy of photons represents the
range of energy states present in the irradiate media. The photolu-
minescence spectrum (Fig. 17) was recorded in the range of 260-
Fig. 11. The outset of C1–H1A···O1 hydrogen bond interactions through the (a)
dnorm and (b) electrostatic potential maps.
5
50 nm at room temperature with an excitation wavelength of 260
nm for the grown 2AT4C single crystal. A broad emission peak was
observed at 378 nm in the PL spectra this emission authorizes that
the 2AT4C crystals have a blue light emission under the excitation.
The widening of the emission band is attributed to inter-molecular
interactions.
3
.6. Third-order nonlinear optical studies
In order to investigate the nonlinear absorption (NLA) proper-
ties of the reported material the open aperture Z-scan experiment
was performed on a 2AT4C single crystal at a laser output power
of 200mW with a laser beam wavelength of 532 nm [12]. Prac-
tically, the intense laser beam is directed to the cuvette which
contains the sample through a lens in this technique. The sam-
ple loaded cuvette is translated around the focal region and vari-
ations in the pattern of far-field intensity are controlled. As the
sample was passed through the focal point, the normalized trans-
mittance of the sample without aperture was measured in the far
field, while the sample comprising media shows the signature of
nonlinear absorption. This enables us to define the NLA coefficient
(
β) of the irradiated system. The open aperture (OA) curve of the
sample 2AT4C is shown in Fig. 18. In this case the transmission
has an intensity-based absorption effect, and is symmetrical with
regard to focus (z = 0), where it has the minimal transmission.
The configuration of the OA curve of 2AT4C sample proposes the
significant two photon absorption [39–42]. The method of NLA cal-
culations are referred from our previously reported articles [14,27]
and the calculated values of the NLA coefficient (β) [12,18], and
Fig. 12. The Hirshfeld surface mapped over (a) shape-index and (b) curvedness for
2AT4C.
9

H. D, R. Bairy, J. A et al.
Journal of Molecular Structure 1232 (2021) 130053
Fig. 13. Thermogram of 2AT4C crystal.
Fig. 15. UV-Visible spectra of 2AT4C crystal.
Fig. 14. Load dependence Vicker’s hardness number plot of 2AT4C crystal.
eled theoretically with experimental data which yields the value of
−
9
2
−
3.220 × 10 cm /W for the nonlinear refractive index (n ); this
the imaginary part of the third-order nonlinear optical susceptibil-
ity χ (3) [3,43] of the 2AT4C sample are tabulated in Table 4. The
2
high order value of n could be the consequence of self-defocusing
2
mechanism in the sample. The method of theoretical modeling of
closed aperture curve and the related calculation of NLR are fol-
lowed by our recently published articles [12,18], meanwhile the
calculated results of the real part of third-order nonlinear opti-
cal susceptibility χ (3) [44] and the nonlinear refractive index n2
theoretical fit for the experimental data of the sample (2AT4C) en-
−
5
dorses the outstanding value of NLA coefficient ‘β = 5.320 × 10
cm/W’ this might be a consequence of light localization behavior
in the photonic structure.
To understand further insight into the nonlinear refraction of
the material the experimentally extracted closed aperture data was
used to comprehend the sign and magnitude of the nonlinear re-
fractive index of the sample 2AT4C through the plotted closed
aperture curve [27,44]. The plotted closed aperture curve of the
sample was shown in Fig. 19 and the peak valley module of the
curve reveals the negative non-linear refractive index (NLR) due
to the self-defocusing effect of the sample [43]. The existence of
self-defocusing effect in any of the optical medium could be an
advantage in concern of NLO applications particularly for photonic
and optoelectronic devices. The closed aperture curve was mod-
[
27,44] of the 2AT4C sample are recorded in Table 6. The obtained
third order NLO coefficients of the 2AT4C crystal are compared in
Table 6 with the previously reported literature crystals.
3.7. Optical limiting
In order to appraise the optical limiting activity of 2AT4C crys-
tal the optical limiting studies were inferred from the same open
aperture Z-scan data. The extracted optical limiting curve which is
plotted as input fluence versus normalized transmittance is pre-
10

H. D, R. Bairy, J. A et al.
Journal of Molecular Structure 1232 (2021) 130053
Table 6
Third-order NLO coefficients of 2AT4C.
∗
NLO Parameters
2AT4C
APTP [17]
TPTP [17]
CTDMP [18]
4’ Methoxy [39]
5
−9
−9
−9
−9
NLA (β)
5.320 × 10− cm/W
1.43 × 10 cm/W
2.463 × 10 cm/W
3.057 × 10 cm/W
2.65 × 10 cm/W
−
9
2
−11
−13
−11
−13
−11
−11
(esu)
NLR (n2)
−3.220 × 10 cm /W
−0.54 × 10
(esu)
−1.54 × 10
(esu)
(esu)
−1.532 × 10
(esu)
−1.502 × 10
−13
(esu)
Third-Order Susceptibility Im [χ(3)]
1.135 × 10 esu
−7
0.22 × 10
(esu)
−13
0.379 × 10
0.47 × 10
−13
(esu)
0.411 × 10
Third-Order Susceptibility Re [χ(3)]
1.211 × 10 esu
−7
−0.583 × 10 (esu)
−1.647 × 10 (esu)
−13
−1.642 × 10 (esu)
−13
−0.619 × 10 (esu)
−13
Third-Order Susceptibility [χ(3)
]
1.660 × 10 esu
−7
-
-
-
-
-
-
-
-
2
Limiting threshold
2.674 kJ/cm
Fig. 16. Optical band gap representation of 2AT4C crystal using Tauc’s plot.
Fig. 18. Open aperture curve of 2AT4C crystal.
Fig. 17. Photoluminescence spectrum of 2AT4C.
Fig. 19. Closed aperture curve of 2AT4C crystal.
sented in Fig. 20. A material should possess a significant op-
tical limiting property for retaining in the photonic and opto-
electronic application domain. It is useful for the protection of hu-
man eyes, optical sensors and optical components against extreme
laser pulses [43,45]. The open aperture (OA) z-scan studies of the
sample 2AT4C shows a reverse saturation absorption mechanism
attributed to strong two photon absorption [12,14]. The optical lim-
iting threshold is an important concept in OL science. It is well
known that it is predicted that perhaps the lower optical limiting
kJ/cm2 and later slight deviation was noticed at the transmittance
for higher incident fluences. The optical limiting threshold of the
2
sample at a 0.01 mol concentration is 2.674 kJ/cm . The diminu-
tion in normalized transmittance with increased fluence was also
reported by Hein et al. [46] for the OL behavior of thiophene
oligomers, where it was endorsed to instantaneous two-photon ab-
sorption. Thus, the optical limiting response of the reported crystal
specifies that the 2AT4C crystal is being proposed even as possible
material for optical limiting devices.
(
OL) threshold would offer a decent optical limiting response. It
is clearly observed from the optical limiting curve that the irradi-
ated optical medium performs linear up to incident fluence of 2.1
11

H. D, R. Bairy, J. A et al.
Journal of Molecular Structure 1232 (2021) 130053
Resources, Writing
-
review
&
editing. Jayarama A: Super-
vision, Validation, Writing
-
review editing. Ching Kheng
&
Quah: Resources. Huey Chong Kwong: Data curation, Software.
Parutagouda Shankaragouda Patil: Resources.
Acknowledgment
The authors express their appreciation to Principal Dr.
Satheeshchandra S, Sri Dharmasthala Manjunatheshwara College
(
Autonomous) Ujire, for their support for the research. CKQ thanks
Malaysian Government and Universiti Sains Malaysia for Funda-
mental Research Grant Scheme (FRGS) (203/PFIZIK/6711899). The
authors also thank TG / DTA / DSC thermal analysis facilities, DST-
PURSE Lab, Mangalore University Mangalagangotri-574199 India.
The authors are thankful to FT-IR facility, STIC, Cochin, Kerala, In-
dia.
Supplementary materials
Supplementary material associated with this article can be
found, in the online version, at doi:10.1016/j.molstruc.2021.130053.
Fig. 20. Optical limiting plot of 2AT4C.
References
4. Conlusions
[1] P.N. Prasad, D.J. Williams, Introduction to Nonlinear Optical Effects in Organic
The synthesized chlorophenyl chalcone derivative 2AT4C was
Molecules and Polymers, Wiley, New York, 1991.
used to grow the single crystals using the solution slow evapora-
tion technique. Using the standard single crystal XRD technique,
the polymorphic existence of the 2AT4C single crystal was ana-
lyzed including molecular structural geometry and structural de-
viations. 2AT4C crystal has been found to persist in a monoclinic
[2] A.N. Prabhu, A. Jayarama, K.S. Bhat, V. Upadhyaya, J. Mol. Struct. 1031 (2013)
9–84.
7
[
3] A N Prabhu, V. Upadhyaya, A. Jayarama, K.S. Bhat, Third-order NLO property
of thienyl chalcone derivative : physicochemical analysis and crystal structure
determination, Mol. Cryst. Liq. Cryst. 637 (2016) 76–86.
[
4] S. Anandan, S. Manoharan, N.K.S. Narendran, T.C.S. Girisun, A.M. Asiri,
Donor-acceptor substituted thiophene dyes for enhanced nonlinear optical
limiting, Opt. Mater. 85 (2018) 18–25.
crystal system with a centrosymmetric symmetry under P2 /c
1
space group but with different lattice parameters. The degree of
the molecular interaction in the crystalline state was analyzed us-
ing HSA, and the percentage of interactions in the 2AT4C molecule
was confirmed by 2D fingerprint plots. The third order NLO stud-
ies revealed that the 2AT4C crystal has reverse saturation absorp-
tion and self defocusing nature with positive NLA coefficient (β
[5] Y.1 Shen, A.J. Shuhendler, D. Ye, J.J. Xu, H.Y. Chen, Two-photon excitation
na- noparticles for photodynamic therapy, Chem. Soc. Rev. 45 (24) (2016)
6725–6741.
[
6] P. Sangeetha, et al., Crystal growth, spectroscopic, optical, thermal and hirsh-
feld surface analysis of glycinium hydrogen fumarate glycine solvate mono-
hydrate (GHFGSM): a third harmonic nonlinear optical organic crystal, J. Mol.
Struct. 1213 (2020) 128187.
[7] A. Azarpour, S. Sharifi, F. Rakhshanizadeh, Nonlinear optical properties of
crocin: from bulk solvent to nano-confined droplet, J. Mol. Liq. 252 (2018)
−5
−9
2
=
5.32 × 10 cm/W) and negetive NLR (n2 =-3.22 × 10 cm /W).
2
79–288.
8] M.M. Waldrop, “The emerging science at the edge of order and chaos”, 259
1993), p. 456.
As a consequence of the reverse saturation absorption mechanism
attributed to strong two photon absorption, the 2AT4C crystal ex-
ibits an excelent optical limiting activity with a limiting threshold
[
(
[9] H.S. Nalwa, S. Miyata (Eds.), Nonlinear Optics of Organic Molecules and Poly-
mers, CRC Press, Boca Raton, 1997.
2
of 2.674 kJ / cm . The linear optical properties of 2AT4C crystal
[
10] M.C. Kuzyk, C.W. Dirk (Eds.), Characterization Techniques and Tabulations for
Organic Nonlinear Optical Materials, Marcel Dekker, Inc, New York, 1998.
have been studied using UV-Visible and Photoluminescence spec-
troscopic techniques. The grown crystal permorms the wide opti-
cal tranparency in the entire visible and IR region along with the
optical band gap 3.47 eV. The Photoluminescence characteristic af-
fords information of blue light emission property by emitting light
of 378 nm when the sample was excited at 260 nm. The physi-
cal properties of the 2AT4C crystal was deliberated using thermal
analysis and vicker’s microhardness test. The physical streangth in-
[
11] T.V. Timofeeva, V.N. Nesterov, R.D. Clark, B. Penn, D. Frazier, M.Y. Antipin, Sys-
tematic study of polymorphism in crystalline non-linear optical materials, J.
Mol. Struct. 647 (2013) 181–202.
[
12] A. Ekbote, P.S. Patil, S.R. Maidur, T.S. Chia, C.K. Quah, Structure and
nonlinear optical properties of (E)-1-(4-aminophenyl)-3-(3-chlorophenyl)
prop-2-en-1-one: a promising new D-π-A-π-D type chalcone derivative crys-
tal for nonlinear optical devices, J. Mol. Struct. 1129 (2017) 239–247.
[
13] S.R. Prabhu, A. Jayarama, K. Chandrasekharan, V. Upadhyaya, S.W. Ng, Synthe-
sis, growth, structural characterization, Hirshfeld analysis and nonlinear optical
studies of a methyl substituted chalcone, J. Mol. Struct. 1136 (2017) 244–252.
2
terms of vicker’s hardness number was found to be Hv=21kg/mm
[
14] D. Haleshappa, A. Jayarama, R. Bairy, S. Acharya, P.S. Patil, Second and third or-
der nonlinear optical studies of a novel thiophene substituted chalcone deriva-
tive, Phys. B Condens. Matter 555 (2019) 125–132.
[15] A. Irfan, A.G. Al-Sehemi, A.R. Chaudhry, S. Muhammad, How methoxy groups
change nature of the thiophene based heterocyclic chalcones from p-channel
to ambipolar transport semiconducting materials, J. King Saud Univ.–Sci. 30
(2018) 458–465.
and the 2AT4C crystal is thermally stable up to 131.02 °C. The
above outlined futures could endorse the gravity of the reported
crystal in the field of optoelctronics.
Declaration of Competing Interest
[
16] A.J. Kiran, K. Chandrasekharan, S.R. Nooji, H.D. Shashikala, G. Umesh, B. Kallu-
raya, χ(3) Measurements and optical limiting in dibenzylideneacetone and its
derivatives, Chem. Phys. 324 (2006) 699–704.
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared to
influence the work reported in this paper.
[
17] H.J. Ravindra, K. Chandrashekaran, W.T.A. Harrison, S.M. Dharmaprakash, Struc-
ture and NLO property relationship in a novel chalcone co-crystal, Appl. Phys.
B 94 (2009) 503–511.
[
18] A.N. Prabhu, V. Upadhyaya, A. Jayarama, K. Subrahmanya Bhat, Synthesis,
growth and characterization of π conjugated organic nonlinear optical chal-
cone derivative, Mater. Chem. Phys. 138 (2013) 179–185.
CRediT authorship contribution statement
[
19] M. Mihalik, et al., Structure phase transitions of polymorphic compounds
with layered crystal structures: the REIr2Si2 case, Intermetallics 19 (2011)
1622–1626.
Haleshappa D: Conceptualization, Investigation, Data cura-
tion, Methodology, Writing - original draft. Raghavendra Bairy:
12

H. D, R. Bairy, J. A et al.
Journal of Molecular Structure 1232 (2021) 130053
[
20] S.J. Kang, S. Song, C. Liu, D.Y. Kim, Y.Y. Noh, Evolution in crystal structure
and electrical performance of thiophene-based polymer field effect transistors:
a remarkable difference between thermal and solvent vapor annealing, Org.
Electron. 15 (2014) 1972–1982.
[34] Crasta Vincent, V. Ravindrachary, R.F. Bhajantri, R. Gonsalves, J. Cryst. Growth
267 (2004) 129.
[35] V. Renuka, B.K. Revathi, D.R. Jonathan, M.K. Priya, P.S. Asirvatham, Synthe-
sis, growth and characterization of a new NLO active chalcone derivative -
4-chloro-N-{3-[(2E)-3-(methoxyphenyl)prop-2-enoyl]phenyl}benzamide mono-
hydrate, J. Mol. Struct. 176 (2019) 838–846.
[
21] H. Pan, P. Liu, Y. Li, Y. Wu, B.S. Ong, S. Zhu, G. Xu, Adv. Mater. 19 (2007)
240–3243.
22] A.J. Cruz-Cabeza, J. Bernstein, Conformational polymorphism, Chem. Rev. 114
2014) 2170–2191.
3
[
[
[36] J. Tauc, R Grigorovici, A. Vancu, Optical properties and electronic structure of
amorphous germanium, Phys. Status Solidi 15 (1966) 627–637.
[37] L. Kumari, W.Z. Li, Synthesis, structure and optical properties of zinc oxide
hexagonal microprisms, Cryst. Res. Technol. 45 (3) (2010) 311–315.
[38] D. Shanthi, P. Selvarajan, S. Perumal, Growth, linear optical constants and pho-
toluminescence characteristics of beta-alaninium picrate (BAP) crystals, Optik,
127 (2016) 3192–3199.
(
23] M. Danko, A. Andics, C. Kosa, P. Hrdlovic, D. Vegh, Spectral properties of chal-
cone containing triphenylamino structural unit in solution and in polymer ma-
trices, Dyes Pigment 92 (2012) 1257–1265.
[
[
[
24] P. Srinivasan, T. Kanagasekaran, R. Gopalakrishnan, Cryst. Growth Des. 8 (2008)
2340–2345.
25] D.N. Dhar, The Chemistry of Chalcones and Related Compounds, Wiley, New
York, 1981.
[39] H.J. Ravindra, A. John kiran, K. Chandrasekharan, H.D. Shashikala,
S.M. Dharmaprakash, Third order nonlinear optical properties and optical
limiting in donor/acceptor substituted 4-methoxy chalcone derivatives, Appl.
Phys. B 88 (2007) 105–110.
26] P.C. Rajesh Kumar, V. Ravindrachary, K. Janardhana, B. Poojary, Structural and
optical properties of a new chalcone single crystal, J. Cryst. Growth 354 (2012)
1
82–187.
[40] R.A. Ganeev, A.I. Ryasnyanskii, M.K. Kodirov, S.R. Kamalov, T. Usmanov, Non-
linear refraction and nonlinear absorption of various media, Opt. Spectrosc. 93
(2002) 789.
[
27] D Haleshappa, C.K. Quah, H.C. Kwong, P.S. Patil, A Jayarama, Investigation of
structural, physical, linear, and nonlinear optical properties of two novel thio-
phene centred D-π-A type push-pull organic derivatives for nonlinear optical
applications, J. Mol. Struct. 1220 (2020) 128763.
[41] M. Yin, H.P. Li, S.H. Tang, W. Ji, Determination of nonlinear absorption and re-
fraction by single Z-scan method, Appl. Phys. B 70 (2000) 587.
[42] R.A. Ganeev, A.I. Ryasnyanskii, M.K. Kodirov, S. Kamalov, T. Usmanov, Opt.
Spectrosc. 93 (2002) 789.
[43] D. Haleshappa, A. Jayarama, C. Kheng, H. Chong, A novel bromo-substituted
thiophene based centrosymmetric crystals : thermal, mechanical, and third or-
der NLO properties for the optical limiting applications, Phys. B Condens. Mat-
ter 585 (2020) 412083.
[44] R Shivaraj, R Jithendra, P.S. Patil, T. Chia, C.K. Quah, Structural characterizations,
Hirshfeld surface analyses, and third-order nonlinear optical properties of two
novel chalcone derivatives, Opt. Mater. 75 (2018) 580–594.
[45] A. Ekbote, P.S. Patil, S.R. Maidur, T.S. Chia, C.K. Quah, Structural, third-order
optical nonlinearities and figures of merit of (E)-1-(3-substituted phenyl)-3-(4-
fluorophenyl) prop-2-en-1-one under CW regime: new chalcone derivatives for
optical limiting applications, Dyes Pigments 139 (2017) 720–729.
[46] J. Hein, H. Bergner, M. Lenzner, S. Rentsch, Determination of real and imagi-
nary part of χ(3) of thiophene oligomers using the z-scan technique”, Chem.
Phys. 179 (1994) 543–548.
[
[
[
[
28] S.M. Dharmaprakash, H. Fun, C. Kheng, Structure – property relation and third
order nonlinear optical absorption study of a new organic crystal, Opt. Mater.
4
9 (2015) 279–285.
29] H.K. Fun, S.R.
E)-3-(4-Chloro-phen-yl)-1-(2-thien-yl)prop-2-en-1-one,
Sect. E Struct. Rep. Online 64 (2008) 8.
Jebas,
P.S.
Patil,
S.M.
Dharmaprakash,
Acta Crystallogr.
(
30] S.K. Wolff, D.J. Grimwood, J.J. Mac Kimon, M.J. Turner, D. Jayatilaka, A.M. Spack-
man, Crystal Explorer Ver. 3.1, University of Western Australia, Perth, Australia,
2013.
31] M.A. Spackman, D. Jayatilaka, CrystEngComm 11 (2009) 19–32.
[
32] A. Parkin, G. Barr, W. Dong, C.J. Gilmore, D. Jayatilaka, J.J. McKinnon,
M.A. Spackman, C.C. Wilson, CrystEngComm 9 (2007) 648–652.
[
33] T. Chandra Shekhara Shetty, et al., Crystal structure, Hirshfeld and
third-order
nonlinear
optical
properties
of
3-(4-dimethylamino)
phenyl)-1-(4-methoxyphenyl) prop-2-en-1-one:
a
potential material for
optical limiting applications, Opt. Mater. 86 (2018) 138–147.
13