Structural and femtosecond third-order nonlinear optical properties of electron donor – acceptor substituted chalcones: An experimental and computational approach

Article abstract of DOI:10.1016/j.molstruc.2020.128523

Structural and third-order nonlinear optical (NLO) properties of two D-π-A-π-A [ (2E)-3-(3-chlorophenyl)-1-(3-nitrophenyl)prop-2-en-1-one (3C3NC) and (2E)-3-(4-fluorophenyl)-1-(4-nitrophenyl)prop-2-en-1-one (FNC)] and one D-π-A-π-D [(2E)-1-(9-anthryl)-3-(

Full text of DOI:10.1016/j.molstruc.2020.128523

Journal Pre-proof
Structural and femtosecond third-order nonlinear optical properties of electron donor –
Acceptor substituted chalcones: An experimental and computational approach
Parutagouda Shankaragouda Patil, Neelamma B. Gummagol, Anusha Ekbote, Qin Ai
Wong, Ching Kheng Quah, Mohd Shkir, Shivaraj R. Maidur, S. Venugopal Rao
PII:
S0022-2860(20)30848-6
DOI:
https://doi.org/10.1016/j.molstruc.2020.128523
MOLSTR 128523
Reference:
To appear in: Journal of Molecular Structure
Received Date: 22 April 2020
Revised Date: 22 May 2020
Accepted Date: 22 May 2020
Please cite this article as: P.S. Patil, N.B. Gummagol, A. Ekbote, Q.A. Wong, C.K. Quah, M. Shkir, S.R.
Maidur, S.V. Rao, Structural and femtosecond third-order nonlinear optical properties of electron donor
– Acceptor substituted chalcones: An experimental and computational approach, Journal of Molecular
Structure (2020), doi: https://doi.org/10.1016/j.molstruc.2020.128523.
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Credit Author Statement
Parutagouda Shankaragouda Patil: Conceptualization, Writing - Original Draft,
Reviewing and Editing, Supervision Neelamma B. Gummagol: Investigation, Data
analysis and Gaussian calculations Anusha Ekbote: Material synthesis and characterization
Qin Ai Wong and Ching Kheng Quah: Solved the single crystal structures and drafted
the manuscript Mohd Shkir: Gaussian calculations Shivaraj R. Maidur: Performed the
Z-scan experiment S. Venugopal Rao: Resources, Writing- Reviewing and Editing,
Supervision.
Page 1 of 1

Graphical abstract
Normalized open aperture (left side) and closed aperture (right side) Z-scan curves of FNC
The molecular electrostatic potential (MEP) map of 3C3NC, FNC and FANC molecules

Structural and Femtosecond Third-Order Nonlinear Optical
Properties of Electron Donor – Acceptor Substituted Chalcones:
An Experimental and Computational Approach
Parutagouda Shankaragouda Patil a,*, Neelamma B. Gummagol a,
Anusha Ekbote a, b, Qin Ai Wong c, Ching Kheng Quah c, Mohd Shkir d,
Shivaraj R. Maidur a, S. Venugopal Rao e
a Department of Physics, K.L.E. Institute of Technology, Opposite Airport,
Gokul, Hubballi 580 030, Karnataka, India
b Department of Physics, KLS's Gogte Institute of Technology,
Udyambag, Belagavi, 590010, Karnataka, India
c X-ray Crystallography Unit, School of Physics,
Universiti Sains Malaysia, 11800 Penang, Malaysia
dAdvanced Functional Materials and Optoelectronic Laboratory (AFMOL),
Department of Physics, Faculty of Science, King Khalid University,
P.O. Box. 9004, Abha 61413, Saudi Arabia
e Advanced Centre of Research in High Energy Materials (ACRHEM), University of
Hyderabad, Hyderabad 500046, India
*Corresponding author. Tel.:+91 836 2232681; Fax: +91 836 2330688.
E-mail address: pspatilcrystal@gmail.com, pspatil@kleit.ac.in (Dr. P. S. Patil)
Abstract
Structural and third-order nonlinear optical (NLO) properties of two D-π-A-π-A [ (2E)-3-(3-
chlorophenyl)-1-(3-nitrophenyl)prop-2-en-1-one (3C3NC) and (2E)-3-(4-fluorophenyl)-1-
(4-nitrophenyl)prop-2-en-1-one (FNC)] and one D-π-A-π-D [(2E)-1-(9-anthryl)-3-(4-
fluorophenyl) prop-2-en-1-one (FANC)] type chalcone derivatives were investigated by
experimentally as well as theoretically. All the three chalcones are centrosymmetric (CS) and
crystallized in P21/c space group. In crystal packing, all compounds exhibit C—H···O
hydrogen bonds and π···π interactions. From UV–Vis–NIR absorption spectra, the cut-off
wavelength and optical band gaps of the chalcones were evaluated. The thermal stability and
the melting point of the chalcones were determined from the TGA/DTA techniques. The
Page 1 of 39

ultrafast third-order NLO properties of the three chalcones in solution (0.01M) were
evaluated by Z-scan technique using femtosecond (fs) pulses from Ti: Sapphire laser (∼150
fs, 80 MHz, 800 nm). Third-order nonlinear absorption (NLA) coefficient (β ~ 10-9 cmW-1),
nonlinear refraction (NLR) index (n2~10-14 cm2W-1), susceptibility (χ(3) ~ 10-12 esu) and
molecular hyperpolarizability (γh ~ 10-31 esu) were unambiguously determined. The chalcones
satisfy the condition to observe reverse saturable absorption (RSA) mechanism (σex > σg).
Further, the larger values of σex/σg (~2-3) indicate that the chalcones would exhibit
remarkable optical limiting property. The estimated optical limiting (OL) threshold values are
in the order of μJ/cm2. Further, all the chalcones have satisfied the one-photon and two-
photon figures of merit conditions (W >1 and T <1) for the optical switching applications. In
addition to experimental findings, the optimized geometry, HOMO-LUMO energy gap, NLO
parameters such as
electronic dipole moment, polarizability, first and second
hyperpolarizabilities of all the three chalcones were determined theoretically (DFT) for
different wavelength at B3LYP/6-311+G(d,p) basic set. The experimentally determined
second-order susceptibilities (Z-scan technique) are reasonably in agreement with the
computational values (TD-DFT). The MEP surface revealed that the 3C3NC, FNC and
FANC molecules have some potential sites for electrophilic and nucleophilic attack. The
experimental and computational NLO data clearly suggest that the nonlinearity of chalcone
molecules greatly depends on the electron donor and acceptor strengths of the substituents.
Further, all the chalcones are potential materials for optical limiting and optical switching
applications.
Keywords: Chalcone derivatives; Single crystal XRD; Nonlinear optical materials; Z-scan
technique; Optical limiting; DFT
1. Introduction
The chalcones (1, 3-diphenyl-2-propen-1-ones) belong to the family of flavonoids and can be
used as a starting material for synthesis of more complex molecules having biological
properties [1]. Chalcone derivatives are abundant in edible plants and possess antibacterial,
anti-inflammatory, anti-histaminic, anticancer, anti-gout, antifungal and antiviral properties
[2-6]. In addition, chalcones substituted with proper strong electron donor (D) and acceptor
(A) on either side of phenyl rings exhibit second and third-order nonlinear optical properties
due to delocalization of its π conjugated electrons in the structure [7-13]. Organic materials
with second and third-order NLO properties having ultrafast nonlinearities, high chemical,
Page 2 of 39

thermal and physical stabilities are needed for practical applications [12–15]. Several
researchers designed and synthesized D–A–D, A–D–A, D–π–D, A–π–A, D-π-A, D–π–A–π–
D and A–π–D–π–A types organic molecules to get large optical nonlinearity, complete
transparency in visible wavelength region, high thermal stability and laser damage threshold
[13, 14]. In such molecules, the order of nonlinearity depends on how efficiently
intramolecular charge transfer (ICT) takes place from donor to acceptor.
Ultrafast optical nonlinear materials are extensively utilized in technologies for optical
computing and optical communication [14-16]. Nowadays, the experimental and theoretical
investigations are the preferred approach to study NLO properties of materials [17–18]. The
theoretical NLO studies are very important to know the structure-property relationships of
materials, which provide relevant information for the engineering of new molecules of
interest [19, 20]. It is evident from literature that the calculations of relevant parameters by
using diverse theoretical models helps in designing of new novel NLO materials for practical
applications [21–26]. Hence, the quantum chemical computational approach is useful in
determination of relevant and necessary molecular properties. In continuation of our research
in nonlinear optics, we report the experimental and computational study on structural, linear
and third-order NLO properties of
two D-π-A-π-A [(2E)-3-(3-chlorophenyl)-1-(3-
nitrophenyl)prop-2-en-1-one (3C3NC) and (2E)-3-(4-fluorophenyl)-1-(4-nitrophenyl)prop-
2-en-1-one (FNC)] and one D-π-A-π-D [(2E)-1-(9-anthryl)-3-(4-fluorophenyl) prop-2-en-1-
one (FANC)] types chalcones for future applications in NLO devices. These chalcones were
synthesised, crystallized by solution growth technique and crystal structures were determined
by single crystal XRD method. The other useful properties such as linear optical properties
(transparency in the visible region and energy gap) and thermal stability (TG/DTA) were also
studied. The experimentally determined third-order susceptibilities (femtosecond Z-scan
technique) were compared with computational values (TDDFT). Our work shows that these
chalcone derivatives exhibit superior NLO responses.
2. Experimental
2.1. Synthesis and crystallization
All chemicals were purchased from Sigma–Aldrich and used without further purification
unless otherwise noted. Among the several synthetic procedures described by the scientific
community for chalcone derivatives, Claisen-Schmidt condensation is the simplest reaction
Page 3 of 39

method, cost-effective, and highly versatile [1]. In the present study, all the three chalcone
derivatives were synthesized by the condensation reaction of corresponding substituted
aldehyde (10 mM) with substituted acetophenone (10 mM) in the present of a catalytic
quantity of aqueous NaOH (5 ml, 10%). After 2–4 hours of vigorous stirring at room
temperature, the reaction mixtures were poured into ice-cold water (500 ml). The resultant
products were filtered, washed with water and recrystallized repeatedly from acetone to get
3C3NC, FNC and FANC pure chalcones of 82%, 78% and 80% yield, respectively (Fig. 1).
Single crystals of good optical quality for XRD data collections were grown by slow
evaporation technique at ambient temperature.
Fig. 1. Molecular structures of synthesized 3C3NC, FNC and FANC chalcones.
2.2. Characterisation
Crystal structure of 3C3NC, FNC and FANC was determined by single crystal XRD data
analysis. X-ray measurements were performed using Bruker APEX II DUO CCD area
detector diffractometer, employing graphite-monochromated Mo Kα radiation (0.71073 Å)
with φ and ω scans, operated at room temperature. The collected raw data was reduced by
using SAINT program [27]. The SADABS program [27] was used for empirical absorption
correction. The structure was solved by direct methods and refined by full-matrix least-
squares methods on F2 by using SHELXTL software package [28, 29]. All non-hydrogen
atoms were refined with anisotropic displacement coefficients. All hydrogen atoms were
Page 4 of 39

positioned geometrically and assigned isotropic displacement coefficients with a riding
model, Uiso (H) = 1.2 × Ueq (C). Molecular structures and crystallographic figures were drawn
using Mercury program [30], interactive Molecular Graphics program XP [28] and OLEX2
program [31]. PLATON [32] was used to prepare the publication materials and determine
hydrogen bonding parameters.
The synthesized three chalcone molecules were thermally analyzed using TGA/DTA analyzer
(SDT Q 600) in the temperature range 0 - 1000 °C at a heating rate of 10 °C /min in nitrogen
atmosphere. Linear optical properties of these chalcones were determined by recording
absorption spectrum using Hitachi Double-Beam Spectrophotometer UH5300 and the optical
band gaps by Tauc’s plots.
The third-order NLO properties were determined by using the femtosecond Z-scan technique
[33]. The Re[χ(3)] and Im[χ(3)] part of the third-order susceptibility are proportional to NLR
(n2) and the NLA coefficient (β) of the material, respectively. The n2 and β can be determined
from the closed aperture (CA) and open aperture (OA) Z-scan experimental data analysis.
The CA and OA experiments were performed using femtosecond (~150 fs) Ti: Sapphire laser
pulses at a wavelength of 800 nm (80 MHz). The beam waist radius ω0 and the corresponding
ꢄ
Rayleigh range ꢀꢁ = ꢂꢃꢁ /ꢅ are measured to be ~25 µm and ~2.54 mm, respectively. The
sample in the dimethylformamide (DMF) solution at concentration 0.01 M in a 1-mm wide
optical cell was translated across the focal region (+Z to -Z) along the axial direction. In the
CA Z-scan (Sꢀ=ꢀ0.40), the transmission of the beam through an aperture placed in the far field
was measured using photo detector. In an OA Z-scan (Sꢀ=ꢀ1), entire transmittance of the beam
was collected through a suitable lens. The pure NLR is extracted by dividing the CA data by
OA data. The measurements on the pure solvent (DMF) in a cuvette were also performed,
validating that the measured results/data originated from the material only.
3. Computational procedure
To optimize the geometries and estimate the various parameters of 3C3NC, FNC and FANC
molecules, we have employed the Gaussian16 [34] and Gamess [35, 36], whereas the
visualization was carried out using Gauss view 6 [37]. The DFT/CAM-B3LYP/6-31G**
basis set was selected to optimize geometries for all three molecules without any symmetry
constraint. The CIF of single crystal XRD measurements was taken as input file for geometry
Page 5 of 39

optimization. The optimized molecular geometries of 3C3NC, FNC and FANC molecules at
CAM-B3LYP/6-31G** level of theory are shown in Fig. 2. The optimized geometries are in
well agreement to the experimental finding obtained from single crystal XRD. The bond
length values of major bonds are noticed to be H7···O4 (2.410 Å) in 3C3NC, H17···O2
(2.390 Å) and H23···O2 (2.404 Å) in FNC and H28···O2 (2.516 Å) and H5···O2 (2.587 Å)
in FANC molecules, which are in close agreement to experimental data (Table 2).
(a)
(b)
FNC
3C3NC
(c)
FANC
Fig. 2. Optimized molecular geometry of (a) 3C3NC, (b) FNC and (c) FANC at CAM-
B3LYP/6-31G(d,p) level of theory.
The optimized structures have been used to obtain linear and NLO parameters by time
dependent density functional theory (TD-DFT). For the estimation of linear optical and NLO
properties, the CAM-B3LYP model is employed at 6-31G** basis set. The NLO parameters
such as the electronic dipole moment (μ), total average polarizability (αtot), anisotropy of
polarizability (Δα), static first hyperpolarizability (β0) and total first hyperpolarizability (βtot)
were determined using the following relations.
Total dipole moment by:
Page 6 of 39

ꢌ
ꢍ
ꢄ
ꢄ
ꢄ
ꢆꢇꢈꢇ = (ꢆꢉ + ꢆꢊ + ꢆꢋ )
(1)
Total polarizability by:
1
ꢎꢇꢈꢇ
=
(ꢎꢉꢉ + ꢎꢊꢊ + ꢎꢋꢋ)
(2)
3
Anisotropy of polarizability by:
1
ꢄ
ꢐꢑꢎꢉꢉ − ꢎꢊꢊꢒꢄ + ꢑꢎꢊꢊ − ꢎꢋꢋꢒ + ꢎꢋꢋ − ꢎꢉꢉ ꢄ + 6ꢎꢉꢋꢓ
(3)
ꢄ
ꢏ
(
)
∆ꢎ =
2
√
The components of first hyperpolarizability by using the following relation:
ꢑꢔꢕꢘꢘ + 2ꢔꢘꢕꢕꢒ
ꢔꢕ = ꢔꢕꢕꢕ + ꢖ ꢗ
ꢙ
(4)
3
ꢕꢚꢘ
By means of x, y, z components, βtot can be obtained by:
ꢄ
ꢄ
ꢄ
ꢏ
ꢔꢇꢈꢇ
=
ꢑꢔꢉ + ꢔꢊ + ꢔꢋ ꢒ
(5)
where βx, βy and βz are:
βx = (βxxx + βxxy + βxyy)
βy = (βyyy+ βxxz+ βyyz)
βz = (βxzz+ βyzz+βzzz)
hence, the ꢔꢇꢈꢇ is:
ꢔꢇꢈꢇ
ꢏ
=
ꢐꢑꢔꢉꢉꢉ + ꢔꢉꢉꢊ + ꢔꢉꢊꢊꢒꢄ + ꢑꢔꢊꢊꢊ + ꢔꢉꢉꢋ + ꢔꢊꢊꢋꢒꢄ + ꢑꢔꢉꢋꢋ + ꢔꢊꢋꢋ + ꢔꢋꢋꢋꢒꢄꢓ
(6)
Furthermore, TDHF/6-31G** method was used to obtain second and third-order NLO
parameters by Gamess program. Only frequency dependent first hyperpolarizability (-2ω;
ω,ω), and second-hyperpolarizability (-3ω;ω,ω,ω) values were estimated at ω=0.04282 a.u
(1064 nm) and 0.05695 a.u. (800 nm), one-to-one by means of second (SHG) and third
(THG) harmonic generation sets of TDHF process. The mean isotropic second
hyperpolarizability (‹γ›) values were determined by the equation,
ꢜ
〈 〉
ꢛ = ꢞꢛꢉꢉꢉꢉ + ꢛꢊꢊꢊꢊ + ꢛꢋꢋꢋꢋ 2ꢑꢛꢉꢉꢊꢊ + ꢛꢉꢉꢋꢋ + ꢛꢊꢊꢋꢋꢒꢟ
(7)
ꢝ
Page 7 of 39

The conversion of above components from au and to esu can be done as 1 au = 0.00864×10-30
esu for β, and 1 au=0.000504×10-36 esu for γ.
4. Results and discussions
4.1. Single crystal X-ray diffraction
Details of crystal parameters, data collection and structure refinements are given in Table 1.
The crystal structures of 3C3NC, FNC and FANC were determined by using X-ray
diffraction method and their asymmetric units are shown in Fig. 3. All compounds consist of
an enone group and an aryl halide group (i.e. chlorobenzene and fluorobenzene). Compounds
3C3NC and FNC comprise a nitrobenzene ring but an anthracene ring system for compound
FANC. All compounds crystallize in monoclinic crystal system with space group P21/c. They
adopt trans configuration with respect to the olefinic double bond (3C3NC: C7—C8═C9—
C10 = 179.2(3)°, FANC: C15—C16═C17—C18 = 179.1(6)° and FNC: C7—C8═C9—C10
= 179.9(2)°). The enone moiety (O1═C7—C8═C9) of 3C3NC and FNC adopt s-cis
conformation, whereas the enone moiety (O1═C15—C16═C17) of FANC adopt s-trans
conformation. The dihedral angles between two benzene rings of 3C3NC and FNC are
0.82(16)° and 4.40(9)°, respectively, which indicate both molecules are approximately planar
and are closely related to the reported structures [38]. The molecule 3C3NC, excluding all
hydrogen and halogen atoms deviates only slightly from that of FNC, as indicated by an
RMS deviation of 0.0716 Å (Fig. 4). The anthracene ring system (C1—C14) is almost planar
with a maximum deviation at atom C2 being 0.032(5) Å. This ring system is almost
perpendicular with the terminal phenyl ring (C18—C23) with the dihedral angle of 82.1(2)°.
The least-squares plane through the enone moiety with a maximum deviation of 0.020(7) Å at
atom C16, is almost planar with the phenyl ring and is almost perpendicular with the
anthracene ring system with the dihedral angles of 2.0º and 83.39º, respectively. Structure
FANC is closely related to reported structures [39, 40].
In the crystal packing, all compounds exhibit C—H···O hydrogen bonds and π···π
interactions (Table 2). The packing of the molecules 3C3NC is depicted in Fig. 5, showing
the intermolecular C5—H5A···O3 hydrogen bond connects the neighbouring molecules into
chains running down the [201]. In the packing of the molecules of FANC (Fig. 6), atom O1
acts as a bifurcated acceptor, linking the adjacent molecules via intermolecular C17—
ꢜ( )
H17A···O1 and C23—H23A···O1 hydrogen bonds to form ꢠꢄ 6 ring motifs [41]. These sets
Page 8 of 39

of ring motif lead to the formation of chains propagating along the c-axis. In crystal FNC
(Fig. 7), two adjacent molecules are arranged into centrosymmetric dimers via pair of C15—
H15A···O1 hydrogen bonds with ꢠꢄꢄ(14) ring motif. The inversion dimers are linked by
intermolecular C2—H2A···F1 hydrogen bonds into infinite chains, propagating along to b-
axis (orange dashed boxed area in Fig. 7). Each chain is arranged in operation of 2ꢜ screw
axes along b-axis to the neighbouring antiparallel chain and connected into two-dimensional
sheet via C11—H11A···O2 hydrogen bonds. The chains of 3C3NC and FANC are further
consolidated by weak π···π interactions, involving the centroids of Cg1···Cg1 (C1−C6
phenyl rings) and Cg2···Cg2 (C10−C15 phenyl rings) in 3C3NC (Fig. 8) and Cg3···Cg3
(C18−C23 phenyl rings) and Cg4···Cg4 (C1/C6−C8/C13/C14 central rings of the anthracene
ring system) in FANC (Fig. 9), with distances being 3.848, 3.779 and 3.891 Å, respectively.
For crystal FNC, successive sheets are stacked along the a-axis and stabilized by π···π
interactions with Cg5···Cg5 = 3.890 Å (C1−C6 phenyl rings) and Cg6···Cg6 = 3.890 Å
(C10−C15 phenyl rings), as shown in Fig. 10. A more comprehensive crystallographic study
of FNC structure can be obtained from our previous work [42].
(a)
(b)
FNC
3C3NC
(c)
FANC
Fig. 3. ORTEP diagrams of asymmetric unit of (a) 3C3NC, (b) FNC and (c) FANC shown in
50% probability displacement ellipsoids with labels for non-hydrogen atoms.
Page 9 of 39

Fig. 4. Overlaid diagram of structures 3C3NC (blue) and FNC (yellow) shown in 50%
probability displacement ellipsoids
Fig. 5. The packing of the molecules of 3C3NC, viewed along the a-axis. Blue dashed lines
represent the intermolecular C5—H5A···O3 hydrogen bonds, linking the adjacent molecules
to form chain running down the [201]. H-atoms not involving in the packing of the molecules
have been omitted for clarity.
Page 10 of 39

Fig. 6. The packing of the molecules of FANC, showing the chains running along the c-axis.
Blue dashed lines represent the hydrogen bonds. H-atoms not involving in the packing of the
molecules have been omitted for clarity.
Fig. 7. The packing of the molecules of FNC, showing a two-dimensional sheet parallel to
(104). Black dashed lines represent the intermolecular hydrogen bonds. Orange dashed boxed
area encloses one hydrogen-bonded chain which propagating along b-axis.
Page 11 of 39

Fig. 8. Green and red dashed lines represent weak π···π interactions of the molecules
3C3NC. Red and green dots represent the centroids of Cg1 (C1−C6 phenyl rings) and Cg2
(C10−C15 phenyl rings).
Fig. 9. Green dashed lines represent weak π···π interactions of the molecules FANC. Red
dots represent the centroids of Cg3 (C18−C23 phenyl rings), whereas purple dots represent
the centroids of the central of Cg4 (C1/C6−C8/C13/C14 central rings of the anthracene ring
system).
Page 12 of 39

Fig. 10. Orange dashed lines represent weak π···π interactions (Cg5···Cg5 and Cg6···Cg6) of
the molecules FNC.
Page 13 of 39

Table 1. Crystallographic data and structure refinement for 3C3NC, FNC and FANC
chalcones.
Crystal data
CCDC number
Chemical formula
Mr
3C3NC
1562559
C15H10ClNO3
287.69
FNC
1036743
C15H10FNO3
271.24
FANC
1562558
C23H15FO
326.35
Crystal system
space group
Temperature (K)
a (Å)
b (Å)
c (Å)
β (°)
V (Å3)
Z
Dcalc (g cm-3)
Radiation, λ (Å)
µ (mm−1)
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/c
296
296
296
3.8477 (15)
29.199 (11)
11.372 (5)
91.784 (7)
1277.0 (9)
4
3.8895 (5)
13.2454 (17)
24.193 (3)
91.993 (2)
1245.6 (3)
4
1.446
Mo Kα, 0.71073
0.11
13.992 (5)
11.295 (4)
11.242 (4)
111.410 (4)
1654.1 (1)
4
1.496
Mo Kα, 0.71073
0.31
1.311
Mo Kα, 0.71073
0.09
Crystal size (mm)
0.34 × 0.33 × 0.11
0.39 × 0.29 × 0.19
0.28 × 0.19 × 0.13
Data collection
Absorption
Multi-scan
Multi-scan
Multi-scan
correction
(SADABS; Bruker, 2009) (SADABS; Bruker, 2009) (SADABS; Bruker, 2009)
Tmin, Tmax
0.716, 0.876
9617
0.862, 0.945
16906
0.858, 0.977
20692
Measured reflections
Unique reflections
Observed reflections
[I > 2σ(I)]
3357
2553
3091
1588
1873
1371
Rint
0.059
0.681
0.033
0.626
0.114
0.606
(sin θ/λ)max (Å−1)
Refinement
Goodness of fit on
F2
R[F2 > 2σ(F2)],
wR(F2)
1.05
1.07
1.14
0.081, 0.184
0.049, 0.127
0.096, 0.221
No. of reflections
No. of parameters
3357
181
2553
181
3091
226
H-atom parameters
constrained
0.20, −0.19
H-atom parameters
constrained
0.17, -0.17
H-atom parameters
constrained
0.33, −0.13
H-atom treatment
Δρmax, Δρmin (e Å−3)
Page 14 of 39

Table 2. Hydrogen-bond geometry (Å, º)
D—H···A
3C3NC
d(D—H) d(H···A) d(D···A) d(D—H···A) Symmetry code
C5—H5A···O3
FNC
0.93
0.93
2.59
3.508 (5) 167
x−1, −y+3/2, z−1/2
C2—H2A···F1
2.53
2.58
2.44
3.188 (2) 128
3.489 (2) 165
3.333 (2) 161
x, y−1, z
C11—H11A···O2 0.93
C15—H15A···O1 0.93
FANC
−x+2, y+1/2, −z+1/2
−x, −y+1, −z+1
C17—H17A···O1 0.93
C23—H23A···O1 0.93
2.42
2.46
3.265 (6) 151
3.307 (7) 151
x, −y+1/2, z+1/2
x, −y+1/2, z+1/2
4.2. Linear optical properties
The UV-vis linear absorption spectrum of 3C3NC, FNC and FANC chalcones are shown in
Fig. 11. The intense absorption peak observed at 311nm, 301 nm, and 311 nm for 3C3NC,
FANC and FNC chalcones, respectively. This peak is due to the transition of a lowest
unoccupied orbital electron (n) to the π* excited states. The cut-off wavelengths for
absorption are observed at 355 nm, 428 nm and 379 nm for 3C3NC, FNC and FANC
chalcones, respectively. All the chalcones are optically transparent in the entire visible
wavelength region and absorb the light only in the UV wavelength region. Hence, NLO
properties of these chalcones can be studied in visible wavelength region. Optical band gap of
all the chalcones were determined from Tauc’s plots (Fig. 11. –Inset plot) [43]. The
calculated energy band gaps from Tauc’s plots are 3.77 eV, 3.56 eV and 3.9 eV for 3C3NC,
FNC and FANC chalcones, respectively.
Page 15 of 39

Fig.11. UV-Vis-NIR absorption spectra of 3C3NC, FNC and FANC chalcones. Inset is
Tauc’s plot. A.U stands for arbitrary units
Page 16 of 39

4.3. Molecular electrostatic potential (MEP) surface
The computed MEP maps for 3C3NC, FNC and FANC molecules at the B3LYP/6-
311G++(d,p) level of theory are depicted in Fig. 12. The MEP surface revealed that the
3C3NC, FNC and FANC molecules have some potential regions for electrophilic and
nucleophilic attack. The oxygen atoms are negative potential sites (red regions), showing the
electrophilic sites where as the positive potential sites (blue regions) are around the nitrogen
and hydrogen atoms in all the molecules indicating the nucleophilic sites. Zero potential areas
are represented with green color.
(a)
(b)
(c)
Fig. 12.The molecular electrostatic potential map of (a) 3C3NC, (b) FNC and (c) FANC
molecules
Page 17 of 39

4.4. HOMO-LUMO and GCRD analyses
The HOMO and LUMO difference in energy gives an idea about the chemical stability of
molecules. As it’s known that if the molecule possesses high energy gap it will come under
stiffer material category. The HOMO and LUMO orbitals energy values determined through
CAM-B3LYP/6-31G** are -6.068, -7.102, -7.183 eV and -2.312, -3.564, -3.238 eV for
3C3NC, FNC and FANC molecules, correspondingly. The HOMO-LUMO gap values for
3C3NC, FNC and FANC chalcones are 3.75, 3.53 and 3.94 eV with hardness 1.87, 1.76 and
1.97 eV (Table 3). These values show that all molecules possess good stability, however
FANC chalcone possess higher compare to other two chalcones.
HOMO, HOMO-1, and LUMO, LUMO+1 orbitals are presented in Fig. 14 along with their
corresponding energy values computed at CAM-B3LYP/6-31G** level of theory (Table 3). It
can be seen in the figure that HOMO is confined only on one side of the molecule of 3C3NC
and FANC and completely on FNC. However, LUMO is confined on the whole molecule of
3C3NC and FNC and only on 4-fluoro substituted phenyl ring of FNC. This shows a clear
charge transfer from HOMO to LUMO in all studied chalcones. The global chemical
reactivity descriptors (GCRD) parameters, hardness (η), chemical potential (µ), softness (S),
electronegativity (χ) and electrophilicity index (ω) for all the three chalcones were also
estimated (Table 3) owing to their strong relations with properties of molecules [44, 45].
These values signify that the studied chalcones possess better stability.
Table 3 The energy values of frontier molecular orbitals (FMOs), energy difference and
GCRD
Molecules
3C3NC
FNC
FANC
a.u.
eV
a.u.
eV
a.u.
eV
Orbitals
-0.223
-0.245
-0.085
-0.033
0.138
0.212
0.069
-0.154
7.246
0.154
0.171
-6.068
-6.668
-2.312
-0.897
3.755
5.768
1.877
-4.190
0.266
4.190
4.676
-0.261
-0.281
-0.131
-0.096
0.130
0.185
0.065
-0.196
7.692
0.196
0.295
-7.102
-7.646
-3.564
-2.612
3.537
5.034
1.765
-5.333
0.282
5.333
8.041
-0.264
-0.279
-0.119
-0.104
0.145
0.175
0.072
-0.191
6.896
0.191
0.252
-7.183
EHOMO
-7.591
-3.238
-2.829
3.945
4.761
1.972
-5.210
0.253
5.210
6.881
EHOMO-1
ELUMO
ELUMO+1
ΔEHOMO –LUMO
ΔEHOMO–1− LUMO+1
η
μ
s
χ
ω
Page 18 of 39

Fig.13. HOMO-LUMO and HOMO-1-LUMO+1 plot for (a) 3C3NC, (b) FNC and (c)
FANC molecule.
Page 19 of 39

4.5. Thermal analysis
Materials with high thermal stability are needed for NLO device applications. A sharp
irreversible endothermic peak in DTA curves observed at 169 °C, 209 °C and 121 °C (Fig.14)
corresponding to the melting point of 3C3NC, FNC and FANC chalcones, respectively. The
observed sharp peak in DTA curves of all the three chalcones confirms the good crystallinity
(Fig. 14). In addition, these compounds are stable up to their melting points as there is no
phase transition and weight loss in TGA curves before these peaks. At higher temperature
(>300 °C), the observed major weight loss of the compounds is attributed by the fast
decomposition of volatile constituents with the compounds. The endothermic peaks at 326
°C, 311 °C and 350 °C in DTA are also in confirmation with the decomposition of 3C3NC,
FNC and FANC, respectively as observed in TGA curve. In FNC, the less intense
exothermic peak observed at 650 ℃, well above the decomposition temperature is due the
oxidation of the chalcone derivative. Thereafter, the sample disappears and only residues left
above the oxidation temperature.
Page 20 of 39

Fig.14. TGA/DTA curves of 3C3NC, FNC and FANC chalcones
Page 21 of 39

4.7. Nonlinear Optical Studies
4.7.1. Third-order nonlinearity
In open aperture (OA) Z-scan curves (Fig. 15 - left side), the decrease in the normalized
transmittance near to the focus point (Z=0) indicates the reverse saturation absorption (RSA).
From the OA curve, the NLA coefficient (β) can be determined by fitting the experimental
data with the equation [12],
βIꢁLꢡꢢꢢ
2 2 (1 + ꢀꢄ/ꢀꢄ)
(8)
T(Z) = 1 −
√
ꢁ
where, T(z) is the transmittance, I0 is the intensity at the focus and Leff
=
(1 − ꢣꢤꢥꢦꢧ ꢩ) ꢎꢁ) is the effective length of the sample. The calculated values of β are in the
ꢨ
⁄
range 0.78 – 7.5x10-9 cm/W for all the chalcones (Table 4).
The imaginary part of the third-order NLO susceptibility χ(3) related to β can be determined
from the relation,
cꢄnꢄꢁ
240πꢄω
( )
ꢫ
(
)
( ⁄ )
m W
χꢪ esu =
β
(9)
where, n0 is the linear refraction index and c is the velocity of light in vacuum and ω is the
( )
ꢯ
angular frequency of the light field. The estimated values of ꢬꢭꢮ of the chalcones are in
the order of 10-13 esu (Table 4).
The closed aperture Z-scan curves of three chalcones are depicted Fig.15 (right side). The
characteristic of CA curves exhibiting pre-focal-peak and post-focal-valley indicating
negative nonlinear refractive index for all the chalcones. The difference in normalized
transmittance between the peak and valley (ΔTpv) is related to the induced phase distortion
Δϕ0 through the relation,
∆ꢰ = 0.406(1 − ꢳ)ꢁ.ꢄꢝ ∆ꢴꢁ
|
|
(10)
ꢱꢲ
where, S (=0.4) is the aperture linear transmittance. To obtain the NLR coefficient n2, the
closed aperture curves were fitted by the formula,
(4ꢵ∆ϕꢁ)
[(ꢵꢄ + 1)(ꢵꢄ + 9)]
( )
T Z =
(11)
where, X=Z/Z0 and Δϕ0 is the on-axis nonlinear phase shift. By measuring Δϕ0 from the CA
graphs, the magnitude of third-order NLR n2 can be easily calculated by using the
Page 22 of 39

relation ∆ꢶꢁ = ꢷꢸꢄꢹꢁꢺꢻꢼꢼ. The magnitude of n2 for all the chalcones are found to be in the
order 10-14 cm2W-1 (Table 4). The real part of third-order NLO susceptibility χ (3) in terms of
the NLR coefficient n2 is given by,
cnꢄꢁ
120πꢄ
( )
χꢽꢫ esu =
nꢄ
(mꢄ/W)
(12)
(
)
The absolute third-order susceptibility χ(3) , which is the sum of real and imaginary
susceptibilities, can be evaluated by using the relation,
ꢾ(ꢫ) = χꢽ(ꢫ) + iχ(ꢪꢫ)
(13)
The obtained χ(3) for the all the synthesized chalcones are in the order of 10-12 esu (Table 4).
The second hyperpolarizability (γh) which has a direct relation with the third-order
susceptibility χ(3) can be determined by using the relation,
(ꣁ)
ꣀ
(14)
ꢛꢿ =
ꢍ
꣄
⁄
[(ꢜ ꢫ)(ꣂ ꣃ ꢄ)] ꣅ
ꢨ
where, n0 is the linear refraction index and N is the number of molecules in per cm3. The
obtained γh values for the chalcones are found to be in the order ~10-31 esu (Table 4).
The ground state absorption cross section σg can be calculated by the relation,
꣆꣇ = ꢎꢁ/N C × 10ꢦꢫ
(15)
where, N is the Avogadro’s number and C is the concentration of the solution in mol/L. The
values of σg obtained for the chalcones are in the order ~10-16 cm2 (Table 4). Further, the
excited state absorption cross section σex can be calculated by the following relation,
꣍
ꢨ
ln[1 +
]
ꢍ
ꢜꣃꢉ
T =
꣍
ꢨ
(16)
(
)
ꢍ
ꢜꣃꢉ
ꢄ
⁄
Where, ꢤ = ꣈/꣈°, ꣉° = ꢎ°꣆ꢻꢉ꣊°ꢺꢻꢼꢼ/2ħ꣋ , ꣊ = 2꣌ ꢂꢃ is the is the fluence of the laser at
°
°
the focus. The values of σex obtained for chalcones are in the order 10-15 cm2 (Table 4). The
calculated values of σex and σg are in agreement with observed RSA (σex > σg)
The ratio of σex/ σg is the figure of merit (FOM) for the material to possess optical limiting
property (OL) [46, 47]. The larger value of the ratio leads to the better OL behaviour. In the
case of RSA, this ratio would be greater than one (σex/ σg >1) whereas in SA the ratio would
Page 23 of 39

be less than one (σex/ σg < 1). In the present study, all the three chalcones are found to have
greater than one. This clearly indicates that the chalcones would exhibit remarkable OL
property.
Fig.15. Normalized open aperture (left side) and closed aperture (right side) Z-scan curves of
3C3NC, FNC and FANC chalcones.
Page 24 of 39

Table 4 Third-order NLO parameters of 3C3NC, FNC and FANC chalcones
Re χ(3) Im χ(3) ꣎ꢮ(ꢯ)
꣎
(e.s.u)
x 10-12
γh
σg
σex
1P
2P
OL
n2
β
α0
(cm-1)
Chalcone
(cm2W-1 (cmW-1) (e.s.u) (e.s.u)
x 10-14
(esu) (cm2)
x 10-31 x 10-16 x 10-15 (a.u.) (a.u.)
(cm2) (W)
(T)
)
(μJ/
cm2)
x 10-9 x 10-12 x 10-13
43.68 - 9.54
44.5 - 21.47
1.1
7.5
5.44
12.25 27.24
10.89 2.83
3.99
5.45
12.55
10.89
2.25
5.18
4.49
4.34
4.42
4.47
0.81 0.45
47
5.57
3C3NC
FNC
0.9
0.8
0.99
0.87
20.9 6.38
23.5 6.59
45.0
-19.09
0.78
FANC
The determined NLO coefficients n2, β and χ(3) of three chalcones have been compared with
some of the reported chalcones and other class of materials determined by Z-scan technique
under fs laser pulses (Table 5). In the present study, the femtosecond (150 fs) NLO
coefficients n2, β and χ(3) of chalcones at 800 nm are found to be in the order ~10-14 cm2/W,
~10-9 cm/W and ~10-12 esu, respectively. The NLO coefficients of the studied three chalcones
are comparable with some of reported chalcones and some of other class of materials (Table
5). It is important to note here that even though the NLO measurements were performed with
fs pulses, the high repetition rate (80 MHz) will consequently lead to thermal effects in the
nonlinearities measured. The pure electronic nonlinearities can only be obtained with fs, kHz
pulses and those will be taken up in future.
Table 5 Comparison of NLO parameters with the reported chalcones and other classes of
materials by femtosecond Z-scan technique.
n2
(10-16cm2/W)
9.7
β
(10-12 cm/W)
8.7
χ(3)
(10-14 esu)
131
Sample
Laser Parameters
Ref.
3TC Chalcone
780 nm; 130 fs; 1kHz
780 nm; 350 fs; 1kHz
780 nm; 130 fs; 1kHz
[48]
2,4,5 TN Chalcone
DMFC chalcone
13.6
-
22.5
13.1
4.45x103 [49]
-
1.9
[50]
[51]
[52]
[53]
[54]
-8.2x103
-3x103
19
Silicon nanoparticles
β and γ BBO nanorods
Perovskite nanocrystals
CsPbI3 (NCs)
680 nm;150fs; 80MHz
800 nm;150fs; 80MHz
800 nm; 70 fs; 1kHz
21x103
1.8x103
32
2x103
4.3x104
-
-1.8x103
68
787 nm; 386 fs; 1kHz
800 nm; 150 fs; 80 MHz
800nm; 150fs; 80MHz
800nm; 150fs; 80MHz
- 9.54 x102
-21.47 x102
-19.09 x102
1.1 x103
7.5x103
0.78 x103
5.45 x102 Present
12.55x102 Present
10.89 x102 Present
3C3NC chalcone
FNC chalcone
FANC chalcone
Page 25 of 39

4.6.2. Optical limiting
Optical limiting (OL) is the control of harmful intense irradiation of laser light, while
permitting the transmission of low energy laser light under ambient conditions. Good OL
materials possess a linear transmittance at low intensities and it becomes constant above the
threshold intensity [55]. In the present study, OL capability of the chalcones is analyzed using
OA data. The observed NLA which basically originates from TPA process can be used for
OL applications. Fig. 16 shows OL curve for all the three samples. The limiting threshold
was calculated at 50% of the linear transmittance and found to be 5.57, 6.38 and 6.59 μJ/ cm2
for 3C3NC, FNC and FANC, respectively (Table 4).
Fig. 16. Optical limiting behaviour of 0.01M DMF solution of 3C3NC, FNC and FANC
chalcone derivatives at 800 nm wavelength
Page 26 of 39

4.6.3. Optical switching
For all-optical switching applications, the chalcones should satisfy the one photon (W) and
two-photon (T) figures of merit (FOM) conditions. The one-photon and two-photon FOM
mainly depends on the linear (α) and two-photon (β) absorption coefficients, respectively
through the relations,
꣏ = ꢸꢄꢹ/ꢎꢅ
ꢰ = ꢔꢅ/ꢸꢄ
(17)
(18)
According to the requirements, the materials must satisfy conditions of W >1 and T <1 [56].
The two-photon FOM T should be less than 1 for low loss optical switching. The calculated
FOM for the chalcone derivatives are given in Table 5. All the chalcones have satisfied the
required conditions for one-photon and two-photon FOM i.e. W >1 and T< 1. Therefore, the
chalcones 3C3NC, FNC and FANC are suitable materials for all-optical switching
applications.
4.6.4. Computational nonlinear optical studies
The fundamental procedure behind polarizability and hyperpolarizability is well-explained by
Kleinman et. al., [57]. These parameters were determined using the well-known relations at
CAM-B3LYP/6-31G** theory (Table 6 and 7). The static first hyperpolarizability (β0) was
ꢫ
estimated by ꢔꢁ = ꢔꢇꢈꢇ in both a.u and esu units (Table 7). For converting from a.u. to esu,
ꢝ
we have used for α, 1 a.u. = 0.1482×10-24 esu and for β, 1 a.u. = 0.008629×10-30 esu [58,59].
The μtot and βtot values for 3C3NC molecule are 5.5 and 12 times bigger compare to urea
molecule (μurea= 1.3732D and βurea= 0.3728×10−30 esu) [58, 59], correspondingly. The μtot and
βtot values for FNC molecule are 3.5 and 40 times bigger compare to urea molecule (μUrea
=
1.3732D and βurea= 0.3728×10−30 esu) and for FANC molecule are 2.6 and 9.5 times [58,59],
correspondingly. These results indicate that the FNC molecule possess higher first
hyperpolarizability compare to 3C3NC and FANC molecule. However, these values for
currently studies molecules are comparable to previous reports on diverse kind of materials
[58, 60-66].
Page 27 of 39