New halogenated chalcones: Synthesis, crystal structure, spectroscopic and theoretical analyses for third-order nonlinear optical properties

Article abstract of DOI:10.1016/j.molstruc.2019.05.122

The halogen chalcones have been prepared by a simple condensation reaction of 4-bromoacetophenone with different substituted halogen benzaldehydes by presence of catalyst of sodium hydroxide. The proposed structures were solved and refined by single cryst

Full text of DOI:10.1016/j.molstruc.2019.05.122

Accepted Manuscript
New halogenated chalcones: Synthesis, crystal structure, spectroscopic and
theoretical analyses for third-order nonlinear optical properties
Muhamad Fikri Zaini, Suhana Arshad, Kaliyaperumal Thanigaimani, Nuridayanti Che
Khalib, Dian Alwani Zainuri, Mundzir Abdullah, Ibrahim Abdul Razak
PII:
S0022-2860(19)30694-5
DOI:
https://doi.org/10.1016/j.molstruc.2019.05.122
MOLSTR 26629
Reference:
To appear in: Journal of Molecular Structure
Received Date: 22 February 2019
Revised Date: 15 May 2019
Accepted Date: 28 May 2019
Please cite this article as: M.F. Zaini, S. Arshad, K. Thanigaimani, N.C. Khalib, D.A. Zainuri, M.
Abdullah, I.A. Razak, New halogenated chalcones: Synthesis, crystal structure, spectroscopic and
theoretical analyses for third-order nonlinear optical properties, Journal of Molecular Structure (2019),
doi: https://doi.org/10.1016/j.molstruc.2019.05.122.
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Graphical Abstract
Four novel new halogenated chalcones are successfully synthesized and characterized
1
13
using IR, H and C NMR and UV-Vis methods. The compounds have been solved
and refined using X-ray single crystal diffraction data. The geometrical parameters
results are compared with density functional theory (DFT) method with B3LYP/6-
311G++ (d,p) level. The energy gaps are obtained for all compounds and the Mulliken
analysis was also theoretically computed. The nonlinear optical (NLO) analysis is
performed by calculating the third-order nonlinear polarizability.

ACCEPTED MANUSCRIPT
New halogenated chalcones: Synthesis, crystal structure, spectroscopic and
theoretical analyses for third-order nonlinear optical properties
Muhamad Fikri Zainia, Suhana Arshada, Kaliyaperumal Thanigaimanib,
Nuridayanti Che Khaliba, Dian Alwani Zainuria, Mundzir Abdullahc, Ibrahim
Abdul Razaka,*
a
X-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM,
Penang, Malaysia
b Department of Chemistry, Government Arts College, Trichy, Tamil Nadu, 620022, India
c
Institute of Nano Optoelectronics Research and Technology, Universiti Sains Malaysia, 11800
USM, Penang, Malaysia
*Author to whom correspondence should be addressed; E-Mail: arazaki@usm.my; Tel.: +604-
6535306; Fax: +604-6579150.
Abstract: The halogen chalcones have been prepared by a simple condensation reaction of 4-bromoacetophenone
with different substituted halogen benzaldehydes by presence of catalyst of sodium hydroxide. The proposed
structures were solved and refined by single crystal X-ray diffraction analysis and the optimized molecular structure
at the ground state were further performed using density functional theory (DFT) method with B3LYP/6-
311G++(d,p) basis set level. The supramolecular C—H···O, C—H···Cl and C—H···π hydrogen bonds and
halogen···halogen interactions observed stabilize and strengthen the crystal structure of the halogen chalcones. All
the newly synthesized compounds were characterized by spectroscopic methods including, FT-IR, 1H and 13C NMR
and UV-Visible. The experimental geometrical parameters were compared with the calculated TD-DFT, where the
values are in good agreement. All compounds exhibiting a good HOMO-LUMO energy gap values in a range of 4.0
and 4.2 eV. Additionally, Hirshfeld surfaces analysis was used to quantify the intermolecular interactions and to
analyze intercontacts in the crystal structure. Results revealed mono-substitution molecules with ortho position will
give a high impact on electronic dipole moment, thus offering a better quality NLO properties of the compounds.
Keywords: Halogen chalcones, Crystal structure, Hirshfeld surface, DFT, Nonlinear optical property
1. Introduction
Chalcones are natural or synthetic compounds belonging to the flavonoid family with widespread
distribution in vegetables, fruits and spices and are present in a variety of plant species [1] Chemically, they consist
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of open-chain flavonoids in which two aromatic rings are joined by a three carbon α,β-unsaturated carbonyl system.
Chalcones have been reported to possess many pharmacological activities [2] including anti-inflammatory [3],
antituberculosis [4], antifungal [5], anticancer [6, 7] , analgesic, antipyretic, antioxidant [8, 9], antibacterial, anti-
HIV [10, 11], antimalarial [12, 13], antiprotozoal activities [14], antimutagenic, antitumorigenic [15] and
antileishmanial [16, 17] properties. Many chalcones have been described for their high anti-malarial activity [18].
Recently, many organic crystals have also been found to be capable of showing strong third-order nonlinear
optical (NLO) properties. Chalcone have been subjected to extensive study with regards to their potential
applications in optical communications, data processing, optical switching and optical power limiting [19-21]. The
essential feature for large NLO responses in organic molecules arises from highly delocalized π-electron systems
and the strength of substituent groups in terms of their donor (D) or acceptor (A) nature [22]. Recently, many
researchers work on halogens to study the chemical and physical properties of organic materials in accordance to the
nonlinear optical characteristics. The introduction of halogen atom can modify physical and optical properties along
with chemical reactivity of organic compounds. The high NLO responses can be found mostly in organic molecules
possessing an electron donor (D) group and an electron acceptor (A) group which promotes the charge-transfer
process [23, 24]. For instance, the chalcone derivatives representing D-π-A configuration [25-27], suggest promising
candidates for NLO applications due to the existence of intramolecular charge transfer between the electron donor
and acceptor groups in the molecule. However, in this research work, we modify the structure design at both ends
capped with electron acceptor groups (A-π-A).
The density functional theory (DFT) that has been tremendously used is effective in explicating the
structural and electronic properties in subclass of materials. Many studies [28, 29] have been performed by DFT on
various organic compounds and chalcones correlated with experimental reports showing an outstanding performance
in dipole moment, average polarizability, anisotropic polarizability and first hyperpolarizability. The present studies
[30, 31] investigates efficient NLO materials, which may induce the interest of scientific community by exploring
their potential in utilization for optical device applications.
The crystal structures of closely related chalcones, viz. 1,3-bis(4-bromophenyl)prop-2-en-1-one [32], 1-(4-
bromophenyl)-3-(4-chlorophenyl)-prop-2-en-1-one [33], (2E)-1-(4-bromophenyl)-3-(4-fluorophenyl)prop-2-en-1-
one [34], 1-(4-bromophenyl)-3-(2,4-dichlorophenyl)-prop-2-en-1-one [35], 3-(3-bromophenyl)-1-(4-bromophenyl)-
prop-2-en-1-one
[36],
1-(4-bromophenyl)-3-(2-chloro-6-fluorophenyl)prop-2-en-1-one
[37],
(2E)-1-(4-
bromophenyl)-3-(4-nitrophenyl)-prop-2-en-1-one [38], 1-(4-bromophenyl)-3-(4-methylphenyl)prop-2-en-1-one [39]
and (E)-1-(4-bromophenyl)-3-(napthalen-2-yl)prop-2-en-1-one [40] have been reported. In continuation of halogen
chalcones research [41-43], we synthesized and report herein the new crystal structure of halogen substituted
chalcone analogues with 4-bromoacetophenone moiety using the conventional base-catalyzed Claisen-Schmidt
condensation. The molecular structure and spectroscopic properties were investigated by single crystal XRD,
1
infrared (IR), H and 13C Nuclear Magnetic Resonance (NMR) and UV-Visible analyses. In addition, the density
functional theory (DFT) at B3LYP methods in 6-311G++(d,p) basis set were employed to predict the structural
parameters of the compound in the gas phase. To confirm the existence of the intermolecular interactions, the
Hirshfeld surface analysis was performed and described. Besides, the Mulliken studies are also reported to
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determine the electronic charge potential and the third-order nonlinear optical susceptibility are discussed to
evaluate its optical properties.
2. Methodology
2.1 Synthesis and crystal growth
A mixture of 4-bromoacetophenone (0.01mol) and a halogen-substituted benzaldehyde (0.01mol) was
dissolved in methanol (20 mL). Catalytic amount of 20% NaOH (5 ml) was added to the solution dropwise with
vigorous stirring. The reaction mixture was stirred for about 5–6 hours at room temperature. The resultant crude
products were filtered, washed successively with distilled water and recrystallized from acetone to get the
corresponding chalcones (Scheme 1). Crystals suitable for X-ray diffraction studies were obtained by the slow
evaporation technique using acetone solvent. The yellow crystals of different shaped for all compounds are shown in
Fig. 1.
2.2 Spectroscopy analysis
The sample of chalcone was analyzed using Fourier transform infrared (FT-IR) with a PerkinElmer
Spectrum GX Frontier Spectrophotometer using KBr pellet and the spectrum was recorded in the frequency range of
4000-400 cm-1 region. 1H-NMR and 13C-NMR spectra were recorded at 500 and 125 MHz, respectively, in DMSO-
d6, on Bruker 500MHz Avance III spectrometer. The chemical shifts are reported in parts per million (ppm)
downfield from internal tetramethylsilane (TMS). UV-Visible absorption spectrum was recorded using SHIMADZU
UV-1800 Spectrophotometer in the wavelength range of 200-800 nm in acetonitrile (CH3CN) solution with quartz
cell of 1.0 cm path length.
(E)-1-(4-bromophenyl)-3-(2-chloro-4-fluorophenyl)prop-2-en-1-one [1]: Solvent for growing crystals:
acetone; Yield: 65%; IR (FT-IR Spectrometer with KBr pellets, cm−1): 3072 (Ar-H), 1663 (C=O), 1583 (−CH=CH–
), 1214 (C−F), 859 (C−Cl), 548 (C−Br). 1H NMR [500 MHz, DMSO, δ(ppm)]: 8.01 (d, 2H, Ph, J = 9.9 Hz), 7.88 (d,
2H, Ph, J = 10.2 Hz), 7.74 (s, 1H, Ph), 7.63 (d, 1H, –CH=CH–, J = 8.8 Hz), 7.38 (d, 1H, –CH=CH–, J = 8.5 Hz),
7.18 (d, 1H, Ph, J = 2.6 Hz), 7.06 (d, 1H, Ph, J = 2.6 Hz). 13C NMR [125 MHz, DMSO; δ(ppm)]: 187.9 (C=O),
136.4 (HC=CH), 121.6 (HC=CH), 163.9, 161.9, 161.7, 138.8, 137.8, 135.5, 131.7, 130.6, 130.4, 129.9, 129.7, 128.9,
127.4, 124.1, 117.2, 115.2, 114.4 (Ar, CH). CCDC No.: 1013205.
(E)-1-(4-bromophenyl)-3-(4-chloro-3-fluorophenyl)prop-2-en-1-one [2]: Solvent for growing crystals:
acetone; Yield: 68%; IR (FT-IR Spectrometer with KBr pellets, cm−1): 3081 (Ar-H), 1660 (C=O), 1584 (–CH=CH–
), 1212 (C−F), 831 (C−Cl), 528 (C−Br). 1H NMR [500 MHz, DMSO, δ(ppm)]: 8.09 (d, 2H, Ph, J = 1.9 Hz), 7.81 (d,
1H, –CH=CH–, J = 8.6 Hz), 7.77 (d, 2H, Ph, J = 1.9 Hz), 7.73-7.71 (m, 2H, Ph), 7.69 (d, 1H, –CH=CH–, J = 8.2
Hz), 7.56 (s, 1H, Ph). 13C NMR [125 MHz, DMSO; δ(ppm)]: 188.0 (C=O), 141.9 (HC=CH), 121.5 (HC=CH),
158.4, 156.4, 136.2, 135.9, 131.9, 131.7, 131.0, 129.9, 127.5, 126.6, 123.6, 116.2 (Ar, CH). CCDC No.: 1013209.
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(E)-1-(4-bromophenyl)-3-(3-chlorophenyl)prop-2-en-1-one [3]: Solvent for growing crystals: acetone;
Yield: 68%; IR (FT-IR Spectrometer with KBr pellets, cm−1): 3077 (Ar-H), 1662 (C=O), 1582 (–CH=CH–), 825
1
(C−Cl), 524 (C−Br). H NMR [500 MHz, DMSO, δ(ppm)]: 8.12 (d, 2H, Ph, J = 7.7 Hz), 8.06 (d, 2H, Ph, J = 11.4
Hz), 7.77 (d, 1H, –CH=CH–, J = 8.4 Hz), 7.68 (s, 1H, Ph), 7.48 (d, 1H, –CH=CH–, J = 6.7 Hz), 7.47-7.45 (m, 2H,
Ph). 13C NMR [125 MHz, DMSO; δ (ppm)]: 188.9 (C=O), 143.5 (HC=CH), 123.9 (HC=CH), 137.6, 137.1, 134.6,
132.6, 131.5, 131.1, 128.8, 128.3 (Ar, CH). CCDC No.: 1013206.
(E)-1-(4-bromophenyl)-3-(2-fluorophenyl)prop-2-en-1-one [4]: Solvent for growing crystals: acetone;
Yield: 67%; IR (FT-IR Spectrometer with KBr pellets, cm−1): 3092 (Ar-H), 1662 (C=O), 1589 (–CH=CH–), 1218
(C−F), 547 (C−Br). 1H NMR [500 MHz, DMSO, δ(ppm)]: 8.08 (d, 2H, Ph, J = 8.6 Hz), 7.78 (d, 2H, Ph, J = 8.6 Hz),
7.71 (d, 1H, –CH=CH, J = 8.6 Hz), 7.54-7.50 (m, 4H, Ph), 7.31 (d, 1H, –CH=CH–, J = 7.9 Hz). 13C NMR [125
MHz, DMSO; δ (ppm)]: 188.0 (C=O), 136.2 (HC=CH), 123.6 (HC=CH), 161.9, 159.9, 135.5, 135.4, 132.8, 132.7,
131.8, 131.7, 130.5, 129.9, 129.1, 127.5, 127.3, 124.9, 124.8, 122.2, 122.1, 116.1, 115.9 (Ar, CH). CCDC No.:
1013725.
2.3 Single crystal X-ray diffraction analysis
X-ray analysis of a suitable single crystal was performed on Bruker SMART Apex II Duo CCD area-
detector diffractometers using MoKα radiation (λ = 0.71073 Å). Data collection was performed by the APEX2
software [44], whereas the cell refinement and data reduction were performed by the SAINT software [44]. The
crystal structures were solved by Direct Method using the program SHELXTL [45] and were refined by full-matrix
least squares technique on F2 using anisotropic displacement parameters by SHELXTL [45]. Absorption correction
was applied to the final crystal data using the SADABS software [44]. All geometrical calculations were carried out
using the program PLATON [46]. The molecular graphics were drawn using SHELXTL [45] and Mercury program
[47]. Anisotropic thermal factors were assigned to all non-hydrogen atoms. In these compounds, all the hydrogen
atoms were positioned geometrically and were refined using a riding model, with isotropic displacement parameters
set to 1.2 times the equivalent isotropic U values of the parent carbon atoms. In the final refinement, the most
disagreeable reflections were omitted [In 1: 2 5 7, 0 1 1, 1 3 5, 1 3 4, 2 5 8, 1 0 11, 2 5 4 and 2 4 10; in 2: 1 3 2, -2 -4
5, 1 0 1, 3 3 2 and 1 -2 2; in 3: -2 1 3 and 0 0 1; in 4: 1 0 0, 1 2 1, 0 0 8, 0 2 0, -3 0 6 and -5 2 4]. Details of the data
collections condition and the parameters of refinement process are given in Table 1.
2.4 DFT Calculations
In computational procedures, the starting geometries of the compounds were taken from X-ray refinement
data. The optimization of the molecular geometries leading to energy minima was achieved using the DFT [Becke’s
non-local three parameter exchange and Lee-Yang-Parr’s correlation functional (B3LYP)] with the 6-311++G(d,p)
basis set as implemented in the GAUSSIAN 09 program package [48]. The time dependent density functional theory
(TD-DFT) at 6-311G++(d,p) have been used to determine HOMO-LUMO energies, absorption wavelengths λmax of
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the electronic transitions and were compared with the experimental UV absorption spectra. The Mulliken and
ground state dipole moment had been computed further with the same level of theory which is B3LYP/6-
311G++(d,p) to investigate the strength of push-pull molecules configuration of the compounds.
2.5 Hirshfeld Surface Analysis
The Hirshfeld surface and the related 2-D fingerprint plots for the title compound crystal structures were
performed utilizing Crystal Explorer 3.1 [49]. The Hirshfeld surface is given the close interaction in 3-D image in
crystal structure which is summarized in a 2-D fingerprint plot. This analysis approaches a graphical tool for
visualization and understanding of intermolecular interaction. The distance from hirshfeld surface to the nearest
atoms outside and inside the surface are represent as di and de respectively. For the distance from the surface to the
nearest atom interior to the surface is known as di, while de represents the distance from the surface to the nearest
atom exterior to the surface [50, 51]. The blue color is referring to the low frequency of occurrence of (di, de) pair
and the grey color is the outline of the full fingerprint [52].
2.6 Nonlinear optical property (Z-scan)
The refractive index, n of the samples was measured using a digital refractometer (DR201-95, KRUSS).
The linear absorption coefficient, α of all samples were obtained from the absorbance UV-VIS spectra in acetonitrile
as the solvent. The Z-scan technique uses computation of intensity-dependent transmission which primarily to
investigate the nonlinear optical properties in detecting both nonlinear refraction (NLR) and nonlinear absorption
(NLA) simultaneously. The z-scan setup is shown in Fig. 2.
The excitation laser used is a continuous-wave frequency doubled diode pumped solid state (DPSS) laser
(Coherent Verdi-V5). The detector used is silicon amplified photodetector PDA55, Thorlabs) with adjustable gain.
With a converging lens of f = 20 cm, the radius of the Gaussian beam-spot at focal point was measured via a laser
beam profiler (Beam Master) to be 23 ꢀm. The sample was contained in a quartz cuvette with a path length of 1 mm
which was mounted into a precision motorized stage (LTS-300, Thorlabs). The sample path length is much smaller
than the Rayleigh length at 3.12 mm, which essential prerequisite for z-scan thin sample analysis. The phenomena
that contribute to NLR and NLA responses can be studied and further characterized from closed z-scan and open z-
scan curves, respectively.
The peak followed by a valley-normalized transmittance obtained from the closed aperture Z-scan is
defined as ꢁTP-V which is given as TP −TV. The variation of this quantity as a function of |ꢁφ0| is given by ꢁTP-V
=
0.406(1 − S)0.25|ꢁφ0| is on the on-axis phase shift at the focus, S is the aperture linear transmittance with r0 denoting
2
2
the aperture radius (S = 1 − exp(−2r0 /ω0 ), and ω0 denoting the beam radius at the aperture in the linear regime.
Then, the nonlinear refractive index, n2 is given by,
∆
ϕ0λ
(1)
n2 =
2
π
I0Leff
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[1− exp(−αL)]
where λ is the laser wavelength, I0 is the intensity of the laser beam at focus z = 0, Leff
=
, Leff is the
α
effective thickness of the sample, α is the linear absorption coefficient and L is the thickness of the sample. The
nonlinear absorption coefficient, β can be estimated from the open aperture Z-scan data. The normalized
transmittance for the open aperture condition is given by,
∞
[−q0 (z)]m
T (z, s =1) =
(2)
3
∑
2
(m +1)
m=0
2
β
I0Leff
K
ω0
or q0(z) < 1, where q0(z) =
,
zR
=
is the diffraction length of the beam and ω0 is the beam waist radius
2
2





1+ z
2 
z
R
at the focal point and k = 2π/λ is the wave vector.
3. Results and Discussion
3.1 Fourier transform infrared spectroscopy (FTIR) analysis
The IR spectra for all synthesized chalcones obtained from the two reactants; 4-bromoacetophenone and
substituted halogen benzaldehydes are clearly observed from the high shifting absorption band of the stretching
carbonyl group. The wavenumber of the C=O stretch due to carbonyl group mainly depends of the bond strength,
which in turn depends upon inductive, conjugative, steric effects and lone pair of electrons on oxygen [53]. The
carbonyl (C=O) stretching vibration is expected in the region of 1680-1750 cm-1 [53, 54]. In this study, the strong
wavenumbers of the stretching carbonyl group (C=O) are found to be in between 1660-1664 cm-1. The assignment is
also in good agreement with the literature values [55, 56].
The IR band observed at 1581-1589 cm-1 indicates the presence of the C8=C9 stretching vibration. The IR
bands corresponding to asymmetric and symmetric aromatic −CH stretching vibrations are observed at 3072-3092
cm-1. The C−H stretching mode occurs above 3000 cm-1 and is typically exhibited as a multiplicity of weak to
moderate bands [57]. From the previous reported C-H stretching frequencies, the wavenumber appears in the range
of 3000-3125 cm-1 [58].
The substitution of heavy atoms fluorine and chlorine in the phenyl ring significantly affect the normal
vibration modes of the ring. C−X [X=F, Cl and Br] absorption occurs in the broad region between 1234 and 492 cm-
1, depending on the configuration and conformation of the compound [59]. The position of the bands is influenced
by neighboring atoms and groups. The smaller the halide atom, the greater the influence of the neighbor [60]. The
C-F stretching vibration of fluoro-substituted aromatic rings are found over a wide frequency range in the
vibrational spectra at 1000-1360 cm-1 due to easy change in the vibrational wavenumbers by adjacent atoms or
groups [61, 62]. The C-Cl stretching vibration is observed in the range of 688.14-563.50 cm-1 in FTIR spectrum
being in good agreement with literature [63] where generally the C−Cl wavenumber was obtained in the region 850-
550 cm-1 [64]. In addition, the stretching C–Br frequencies are also found in the IR spectra which are within the
range of 524-548 cm-1. Xiao et al. [65] designated the band at 526 cm−1 is correspond to the C–Br stretching
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mode. The region where the bands appear depending on the type of aromatic rings as well as the substituents present
on the ring.
3.2 Nuclear Magnetic Resonance (NMR) spectra analysis
The chemical shift analysis is done using Nuclear Magnetic Resonance (NMR) spectroscopy that helps to
determine the content and purity of the compound. The parameters such as chemical shifts, multiplicities and
1
electronic effect of all the chalcones are obtained from high resolution H and 13C NMR spectra. In chalcones, the
1
H-
α
and H-
β
protons occur as two doublets in the ranges of 6.7-7.4 ppm (H-
α
) and 7.3-7.7 ppm (H-
β
) in the H
NMR spectra [66] which correspond to the trans double-bond configuration which is commonly found in naturally
occurring chalcones [67]. In this study, the corresponding values are within the range of 7.31-7.69 ppm (H- ) and
7.63-7.81 ppm (H- ). The of Cα and Cβ hydrogen atoms are found to be slightly shifted which is due to the
α
β
δ
conjugation effect with the carbonyl group and aromatic rings [68] where the studied compounds consist of highly
electronegativity halogenated substituent elements. Additionally, the presence of weak intramolecular
C9−H9A···O1 hydrogen bond in the molecular structure, shifting the
δH-β values higher than the δH-α. In general,
the aromatic protons usually appear in the range of = 6.9-8.0 ppm, depending on the type of aromatic ring and
δ
based on the electronic effects of the substituent present on the ring. Rajesh Kumar et al. in their reported structure
of chalcone stated that the aromatic proton chemical shifts of the substituted 2,3,5-trichlorophenyl are 8.114 and
7.721 ppm [69]. The aromatic proton chemical shifts of all chalcones in this report are found in the range of 8.12-
7.43 ppm.
For 13C NMR, the carbonyl carbon of the chalcones appears at the chemical shift (
δ) values ranging from
188.6 to 194.6 ppm [70]. The carbonyl groups are found at the most de-shielded area (188.9-187.9 ppm) compared
to other carbon atoms because of the environment factor and the increasing of electronegativity from oxygen atom.
The
between
are in the normal ranges.
α
- and
β
-carbon atoms with respect to the carbonyl group (−OC−CH=CH−) give rise to characteristic signals in
δC8 = 121.5-123.9 ppm and
δ
C9 = 136.2-143.5 ppm, respectively. All other carbon chemical shift ( ) values
δ
3.3 Molecular and optimized structural analysis
The molecular structure and optimized structure of the compounds 1, 2, 3 and 4 with assigned atom-
numbering scheme are presented in Fig. 3 (a) and Fig. 3 (b), respectively. All the new halogen chalcones containing
similar bromo-substituent unit at para position of phenyl ring (R1) and different substituents at the phenyl ring (R2).
Two halogen chalcones namely (E)-1-(4-bromophenyl)-3-(2-chloro-4-fluorophenyl)prop-2-en-1-one (1) and (E)-1-
(4-bromophenyl)-3-(4-chloro-3-fluorophenyl)prop-2-en-1-one (2) are isomers consisting fluoro and chloro
substituent units at ortho-para and para-meta position, respectively. Meanwhile, another two halogen chalcones (E)-
1-(4-bromophenyl)-3-(3-chlorophenyl)prop-2-en-1-one (3) and (E)-1-(4-bromophenyl)-3-(2-fluorophenyl)prop-2-
en-1-one (4) consist of different substituent units, meta-chloro and ortho-fluoro, respectively. These compounds
correspond to the acceptor-pi-acceptor (A-
π
-A) intermolecular charge transfer system, where all halogen atoms
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represent electron acceptor. The crystal structure
and P21/c space group, respectively. On the other hand, both compound
P-1 space group. Interestingly, the asymmetric unit of compounds contains two crystallographically independent
1
and
4
crystallize in monoclinic system with P21/n space group
2
and crystallize in triclinic system with
3
3
molecules, A and B while the other compounds comprise one molecule. The optimized structure were performed by
DFT at B3LYP/6-311G++(d,p) basis set and the geometrical parameters was listed in Table 2. All bond lengths and
angles of the optimized structure are compared to the experimental values and both results are unexceptional and fall
within the expected ranges.
The enone moiety (O1/C7-C9) of all compounds exist in s-cis configurations with respect to their C7=O1
and C8=C9 [bond distances of 1.214 (10) Å in
(5) Å in and 1.302 (12) Å in ; 1.335 (3) Å in
double bonds (Table 2). The 4-bromophenyl moiety (Br1/C1-C6) of compound
chloro-4-fluorophenyl)but-3-en-2-one planarity [Cl1/F1/O1/C10-C15; maximum deviation: 0.086 (8) Å at O1] at the
C6—C7 bond with the C1—C6—C7—C8 torsion angle being 172.7 (9)°. Meanwhile, for the compound , the
1
; 1.228 (2) Å in
2
; 1.223 (4) Å in
(A), 1.323 (5) Å in
deviates slightly from the (E)-4-(2-
3
(A), 1.204 (5) Å in
3 (B); 1.210
4
1
2; 1.315 (5) Å in
3
3
(B); 1.319 (6) Å in 4]
1
4
bromo-substituent benzene ring (Br1/C1-C6) is slightly twisted at the C6—C7 bond from the mean plane of the (E)-
4-(2-fluorophenyl)but-3-en-2-one [O1/F1/C7-C15; maximum deviations: 0.171 (4) Å at atom O1] with the C1—
C6—C7—C8 torsion angle value of 17.2 (7)°. The corresponding torsion angles for DFT are -165.51° (
16.64° ( ). Furthermore, the compound is almost planar where the least-square plane through the enone group
[O1/C7-C9; maximum deviation: 0.0233 (16) Å at atom C7] makes dihedral angles of 8.55 (11)° and 8.04 (10)° with
the C1—C6 and C10—C15 benzene rings, respectively. Compound is also found to be almost planar where the
1) and
4
2
3
dihedral angles between the mean plane through the enone group [O1/C7-C9; maximum deviations: 0.040 (4) Å at
C7A and 0.018 (4) Å at C7B] with the terminal benzene rings C1—C6 and C10—C15 are 9.5 (3) and 6.2 (3)°,
respectively in molecule A and 2.7 (3) and 3.1 (3)°, respectively in molecule B. The dihedral angle between two C1-
C6 (R1) and C10-C15 (R2) phenyl rings for compound
being 15.36° ( ), 8.89° ( ), 6.30° ( ) (molecule A); 7.98° (
compound and exhibit a large dihedral angle as compared to the compound
would be diminishing the electronic effect between two phenyl rings through the enone moiety.
1
-
4
is portrayed in Fig. 3 (c). The dihedral angles formed
) (molecule B), and 25.85° ( ). It is found that,
and . The large dihedral angle
1
2
3
3
4
1
4
2
3
In the crystal packing of 1, the intermolecular C5—H5A···O1 hydrogen bonds (Table 3) link the molecules
into chains along the b-axis as shown in Fig. 4 (a). In addition, the halogen···halogen interactions (Table 4) between
the bromine and fluorine atoms of C—Br···F (-3/2+x,3/2-y,-1/2+z) [Br···F = 3.215 (6) Å] and C—F···Br
(3/2+x,3/2-y,1/2+z) [F···Br = 3.215 (6) Å] are also observed in the crystal packing where the Van der Walls radii of
F and Br atoms are 1.47 and 1.86 Å, respectively [71]. These interactions further bridge the chains into a two-
dimensional sheet parallel to bc-plane. In compound
2, the molecules are linked by intermolecular C11—
2
H11A···O1 (-x+1, -y+1, -z) hydrogen bond (Fig. 4 (b); Table 3) into cyclic centrosymmetric R2 (14) dimers [72]. In
the crystal structure of
two dimensional layers parallel to the ac-plane (Fig. 4 (c)). These layers are further inter-connected into a three-
dimensional network via C1A—H1AA···Cl1A (-x+1, -y+2, -z) hydrogen bonds. The crystal packing of compound
3, molecules A and B are interlinked via three C—H···O hydrogen bonds (Table 3) to form
4
is stabilized by intermolecular C1—H1A···O1 (x, -y+3/2, z+1/2) hydrogen bonds (Table 3), forming one-
8

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dimensional chain running along the c-axis (Fig. 4 (d)). The short Br1···Br1 (-x,1/2+y,3/2-z) (Table 4) contacts
[contact distance: 3.6196 (9) Å] less than the sum of Van der Walls radii of Br (1.86 Å) which is 3.72 Å [73]are also
observed, forming a one-dimensional zig-zag chain along the b-axis (Fig. 4 (d)). The formation of chains via C—
H···O and Br···Br interactions connect the molecules into a two-dimensional layer parallel to the bc-plane and
further stabilize the crystal structure. Furthermore, the presence of this Br···Br contacts is due to the greater
polarizability and high electronegativity of Br atoms.
3.4 UV-Vis spectral and frontier molecular orbitals (FMO) analysis
The UV-vis absorption spectra of compounds 1-4 was recorded using 1800 Shimadzu UV-vis
spectrophotometer in acetonitrile (CH3CN) solution. The spectra and their respective frontier molecular orbital are
presented in Fig. 5. The corresponding data are summarized in Table 5. The most part of the absorption
spectroscopy of organic are based on the transitions of n or
range of 200-700 nm [74]. As can be seen from the UV-Vis spectra (Fig. 5), all compounds indicate comparable
spectra with the strong absorption maximum (
max) at 300-320 nm are correspond to the n-π* transition which
π
electrons to the π* excited state which happens in the
λ
attribute to the excitation in the aromatic ring and C=O group [75]. All compounds have a lower optical cut-off at
340-350 nm which are transparent in the entire visible region and the absorption takes place in the UV range. The
absence of the absorptions in the visible region shows the potential of all compounds to act as nonlinear optical
materials [76]. The UV spectra showed similar patterns, but different intensity of the peaks depending on the
substituents of the halogens group [77]. From the UV spectra, the maximum absorption wavelength is implied in the
−1
mathematical equation
where h is the Planck constant and c is the speed of light to calculate the energy
Eg = hc
λ
max
gap for each compounds. The experimental energy gap calculated from the UV spectra are found in the range of 3.9
to 4.1 eV as presented in Table 5.
HOMO and LUMO energies are important parameters for quantum chemistry. The electronic transition
between frontier molecular orbitals HOMO LUMO are usually corresponds to the maximum absorption wavelength.
The conjugated molecules are characterized by a highest occupied molecular orbital-lowest unoccupied molecular
orbital (HOMO-LUMO) separation, which is the result of a significant degree of ICT (Intramolecular Charge
Transfer) from the end-capping electron-donor groups to the efficient electron-acceptor groups through π-conjugated
path [24]. The difference in energy between these two frontier orbitals known as HOMO LUMO gap is associated to
the electronic charge transfer interaction which occurred within the molecule. Results from the TD-DFT at B3LYP
6-311 basis set level showing the energy gap of all compounds 1-4 are found in the range of 4.0 eV to 4.1 eV. These
values are in close agreement with the Eg value calculated using the mathematical expression. At HOMO state, the
orbitals are localized mainly over the phenyl ring R2 and enone chain, while LUMO orbitals localized over the
entire molecules, illustrated in the inset of Fig. 5.
3.5 Mulliken and ground state molecular dipole moment
9

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The electronic molecular dipole moment signifies the electron movement in a molecule sometimes called
as push-pull polarization system. The total dipole moment along with their individual components for four
compounds have been summarized in Table 6. The dipole moment magnitude depends on the orientation and
position of halogen substituent units. Previous study reported that when both substituents are electron pushing, the
para product has the least dipole moment and ortho products has the highest dipole moment [24]. The representation
of electronic dipole moment based on charge population analysis for all compound is illustrated in Fig. 6. It is found
that, the compound
longest vector arrow while the compound
0.68D as represented by the shortest vector. In addition, compound
highest dipole moment with magnitude vector of 3.47D and followed by the compound
4
with o-F at the phenyl ring showed the greatest dipole moment of 4.61D identified by the
with m,p-F,Cl substitution showing the lowest dipole magnitude of
with m-Cl substitution signifies the second
with 2.98D. This trend of
2
3
1
dipole moment magnitude is clearly due to the orientation of halogen substitution at different position and the
influence of the number of halogen substituent unit. Single substitution indicates a higher total dipole moment
compared to multi-substitution. Even though the UV spectral and FMO analysis of compound
2
exhibit more active
and 3,
NLO, the orientation of the o and m substitutions result in the higher dipole moment as seen in compound
4
respectively. Therefore, the large dipole moment leads to a better nonlinear response of the organic compound.
3.6 Hirshfeld surface analysis
The Hirshfeld surface has proven in discerning the differences of intermolecular interactions and obtaining
the quantitatively of 2-D fingerprint plot percentage on intermolecular interactions [50, 78]. Each molecule in the
asymmetric unit of a crystal structure gives the unique Hirshfeld surface and hence made percentage contributions of
intermolecular contacts. The Hirshfeld surface of the title chalcones was analyzed to clarify the nature of the
intermolecular interactions which is illustrated in Fig. 7 showing the surfaces that have been mapped over dnorm. The
surfaces are shown as transparent to allow visualization of the chalcones moiety with neighbouring molecules. As
expected, the dnorm surfaces of Fig. 7 reveal the close contacts of hydrogen bond donors and acceptor with the large
circular depression (red bright) and as evident for other close contacts such as halogen···halogen interactions
(compound
the bright red area (Fig. 7).
2-D fingerprint plots from Hirshfeld surface analysis of these four chalcones have been calculated to gain
1). The dominant C—H···O interactions in the chalcones are evident in the Hirshfeld surface plots by
the quantitative data on the percentage contributions of C···H/H···C and O···H/H···O intermolecular contacts on the
molecules. For each chalcones, the fingerprint corresponds to its classical hydrogen bond behavior. The overall 2-D
fingerprint plot delineated into C···H/H···C and O···H/H···O intermolecular contacts are illustrated in Fig. 8.
Fingerprint plots can emphasize atom pair close contacts. It enables separation of contributions from different
interaction types, which overlap in the full fingerprint (Fig. 8 left). The C···H/H···C close contacts are observed at
11.9% in compound
1
, 20.1% in compound
2
, 23.1% in compound
3 and 17.6% in compound 4. The O···H/H···O
intermolecular interactions for compounds
1–4 appear as spikes in the 2-D fingerprint plots (Fig. 8 right). The
10

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O···H/H···O intermolecular interactions showing two narrow spikes provide the evidence for C—H···O non-
classical hydrogen [52].
3.7 Nonlinear optics (NLO) property
The z-scan measurements were performed using the reported method [24] to study the third-order nonlinear
response of the compounds. The close-aperture z-scan profiles of the compounds are shown in Fig. 9. In close-
aperture z-scan, the sample which has been contained in a 1 mm quartz cuvette is moved through the tightly focused
along the z-axis of the beam. The scan was carried out at 4.1, 8.3, 12.4 and 16.5 kW/cm2. All the samples show a
transmittance profile with a peak followed by valley which suggest the self-defocusing effect (negative nonlinear
refractive index, n2). Considering that in the case of CW laser, the major sources of NLR was originated from non-
local excitation region due to the thermal nonlinearity effects. The spatial variations were induced because of the
non-uniform temperature distribution within the instantaneous beam waist. Consequently, severe phase distortion of
the propagating beam occurs, which act as a thermal lensing. This is supported by the peak to valley z separation
calculated to be higher than 1.7 zR.
The normalized transmittance in Fig. 9 is fitted using equation from z-scan theory to obtain the sign and the
magnitude of n2 [24]. The values of n2 of the compounds at different excitation intensity are given in Table 7 which
is in the order of 10-9 cm2/W. The intensity-dependent n2 in Table 7 shows that the absolute value of n2 generally
enhances with the increase in the excitation intensity. These different NLR behavior of such compounds can be
attributed to the intrinsic properties at the molecular level. The nature of the
(D-A) translate into the occurrence of intramolecular charge transfer (ICT).
π-bonding tail and the donor to acceptor
Conclusions
The third order nonlinear optical properties of all the halogen-substituted chalcone derivatives were
successfully investigated by Z-scan technique. All compounds were synthesized in good yield and characterized by
IR, 1H NMR, 13C NMR, UV-Visible and single crystal X-ray diffraction analyses. The theoretical and experimental
geometrical parameter results show a good agreement. All the presented crystal structures show that the
intermolecular forces play a major role in the supramolecular arrangement of the crystal structure. The presence of
intramolecular C—H···O hydrogen bonds in all the chalcone derivatives stabilizes the individual molecular
structure. Intermolecular C—H···O (in
1-
4
) and C—H···Cl (in
3) hydrogen bonds observed formed a
supramolecular assembly of molecular structures. Additionally, in compound
1
and , the crystal packing is further
4
stabilized by halogen···halogen [Br…F & Br…Br] contacts. These supramolecular arrangements transform the
halogen substituted chalcones into a 1-D and 2-D supramolecular network. Furthermore, the Hirshfeld surface
analysis with fingerprint plots reveals the relatively weak intermolecular interactions of these chalcone compounds
which are dominated by C…H and O…H interactions dominate the fingerprint plots. The energy gap values
11

ACCEPTED MANUSCRIPT
obtained from the experimental and theoretical calculations are in close range (~4.0 eV) and shows the good
electronic charge transfer within the molecules. The large dipole moment indicates that the organic compounds
possess a good NLO response. However, the orientation of the substitution’s unit at ortho position triggered an
excellent static dipole magnitude as compared to the meta and para position. It was observed from the closed
aperture z-scan that the samples exhibit good transmittance profile and self-defocusing effect where the excitation
intensity is in order of 10-9 cm2/W. This NLR behavior could contribute to intrinsic properties thus exploiting the
development of photonics devices.
Acknowledgements
The authors thank the Malaysian Government and Universiti Sains Malaysia (USM) for the research
facilities, the Research University (RUI) Grant No: 1001.PFIZIK.8011081 and the Fundamental Research Grant
Scheme (FRGS) No. 203.PFIZIK.671106 to conduct this work.
Supplementary materials
This data CCDC: 1013205, 1013209, 1013206 and 1013725 can be obtained free of charge at
www.ccdc.cam.ac.uk.conts/retrieving.html/ or from the Cambridge Crystallographic Data Centre (CCDC), 12 Union
Road, Cambridge CB2 IEZ, UK; fax: +44(0) 1223-336033; e-mail: deposit@ccdc.cam.ac.uk.
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Fig. 1. The single crystals of compound (a) 1, (b) 2, (c) 3 and (d) 4.
Fig. 2. Z-scan technique.
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Fig. 3. (a) The crystal structure in ORTEP diagram with atom numbering schemes where the displacement ellipsoids
are drawn at the 50% probability level and (b) the optimized structure of respective compound (c) the dihedral
angles between two main planes.
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Fig. 4. (a)(b) Crystal packing showing the infinite C—H···O interactions forming a chain running along the b-axis
2
in compound 1 and 2, respectively. The hydrogen bonded R2 (14) ring motif is observed in the compound 2. (c)
supramolecular two-dimensional ac plane formed via C—H···O interaction and connected into a 3-D network via
C—H···Cl interaction in 3. (d) C—H···O hydrogen bonding patterns extending along b-axis in 4. H atoms not
involved in the crystal structure have been omitted for clarity.
19

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Fig. 5. UV-Vis absorption spectra of chalcones and their respective frontier molecular orbitals.
20

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Fig. 6. Hirshfeld surfaces mapped over dnorm showing hydrogen-bonding interactions (green dashline) with their
neighbouring molecules
21

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Fig. 7. 2-D fingerprint plots of the compounds 1-4: full (left) and relative contribution of atom pairs to the Hirshfeld
surface (C…H %) (middle) and (O…H %) (right).
22

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Fig. 8. The representation of relative orientation of electronic dipole moment vector (blue arrow) based on Mulliken
population analysis with color scheme for partial charges of all atoms in molecule.
23

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Fig. 9. Close-aperture z-scan profile of the compound (a) 1, (b) 2, (c) 3, and (d) 4. The theoretical fit lines are shown
in red.
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Table 1 Crystal data and structure refinement parameters.
Compounds
1
2
3
4
1013205
1013209
1013206
1013725
CCDC deposition
numbers
C15H9BrClFO
339.58
C15H9BrClFO
339.58
C15H10BrClO
321.59
C15H10BrFO
305.14
Molecular formula
Molecular weight
Monoclinic
P21/n
Triclinic
P-1
Triclinic
Monoclinic
P21/c
Crystal system
P-1
Space group
3.9598 (10)
11.705 (3)
29.831 (7)
90.00
5.4032 (3)
7.7034 (4)
15.6459 (8)
89.4510 (9)
89.511 (1)
87.930 (1)
650.75 (6)
2
5.7725 (5)
11.5622 (10)
20.9401 (18)
102.8460 (18)
96.4660 (19)
97.8840 (18)
1334.8 (2)
4
21.287 (3)
5.0068 (8)
12.3150 (18)
90.00
a/Å
b/Å
c/Å
α /°
90.582 (5)
90.00
96.536 (4)
90.00
β/°
γ/°
V/ Å3
1382.5 (6)
4
1304.0 (3)
4
Z
Dcalc/g cm−3
Crystal Dimensions /mm
ꢀ/mm−1
1.631
1.733
1.600
1.554
0.20×0.20×0.10 0.82×0.30×0.23 0.34×0.33×0.25
0.60×0.14×0.05
3.15
3.17
3.36
3.26
0.71073
672
0.71073
336
0.71073
640
0.71073
608
Radiation λ/Å
F(000)
0.566/0.743
9246
0.170/ 0.513
11458
0.408/0.500
27753
0.256/0.851
17997
Tmin/Tmax
Reflections measured
Ranges/indices (h, k, l)
h = −4→4
k = −13→13
l = −35→35
h = −6→7
k = −9→10
l = −20→20
h = −8→8
k = −16→16
l = −28→29
h = −27→27
k = −6→6
l = −16→16
2.2-25.0
2373
2.6-27.5
2951
1.8-30.2
7830
1.9-27.5
2996
θ limit /°
Unique reflections
1377
2842
4256
1678
Observed reflections
(I > 2σ(I))
172
172
325
163
Parameters
Goodness of fit on F2
R1, wR2 [I ≥ 2σ(I)]
Rint
1.07
1.09
1.06
1.03
0.081, 0.218
0.063
0.026, 0.077
0.024
0.059/0.210
0.028
0.051/0.154
0.071
0.61 and −0.37
1.63 and −0.43
1.16 and −1.05
0.77 and −0.38
Largest diff. peak and
hole, e/Å-3
2
2
For 1, w = 1/[σ2(Fo ) + (0.0735P)2 + 5.9781P], For 2, w = 1/[σ2(Fo ) + (0.0435P)2 + 0.4652P], For 3, w =
1/[σ2(Fo ) + (0.1042P)2 + 0.6416P], For 4, w = 1/[σ2(Fo ) + (0.0717P)2 + 0.6719P, where P = (Fo + 2Fc2)/3; [a] R
= Σ||Fo| – |Fc||/Σ|Fo|, [b] Rw = {wΣ(|Fo| – |Fc|)2/Σw|Fo|2}[7, 13]}1/2, [c] GOF = {Σw(|Fo| – |Fc|)2/(n–p)}1/2, where n is
the number of reflections and p the total number of parameters refined.
2
2
2
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Table 2 Selected bond lengths, bond angles and torsion angles for compounds 1-4.
Bonds
1
2
3
4
Exp (Å, °)
(A)
Exp (Å, °)
DFT
Exp (Å, °)
DFT
DFT
Exp (Å, °)
DFT
(B)
1.894 (9)
1.214 (10)
1.469 (12)
1.472 (13)
1.302 (12)
1.457 (13)
120.6 (8)
118.1 (9)
121.2 (8)
124.4 (9)
129.5 (9)
10.9 (13)
−165.7 (9)
−3.5 (15)
180.0 (9)
−177.4 (9)
−179.1 (10)
4.1 (16)
1.914
1.8935 (19)
1.228 (2)
1.913
1.893 (4)
1.223 (4)
1.487 (6)
1.477 (5)
1.315 (5)
1.462 (5)
119.9 (3)
120.3 (4)
119.8 (3)
121.6 (3)
127.8 (3)
179.4 (4)
0.1 (5)
1.892 (4)
1.204 (5)
1.493 (5)
1.483 (6)
1.323 (5)
1.461 (6)
119.6 (4)
119.4 (4)
120.9 (3)
122.0 (4)
126.8 (4)
1.914
1.890 (4)
1.210 (5)
1.483 (6)
1.467 (6)
1.319 (6)
1.450 (6)
120.1 (4)
120.9 (4)
119.0 (3)
122.0 (4)
127.1 (4)
−163.7 (5)
12.3 (7)
1.914
Br1—C3
1.223
1.223
1.223
1.223
O1—C7
1.501
1.498 (2)
1.501
1.502
1.503
C6—C7
1.486
1.480 (2)
1.485
1.485
1.484
C7—C8
1.345
1.335 (3)
1.345
1.345
1.345
C8—C9
1.462
1.464 (2)
1.461
1.463
1.460
C9—C10
119.920
121.304
118.772
120.320
126.328
13.743
-164.794
8.069
119.55 (16)
120.82 (16)
119.62 (15)
119.54 (16)
126.91 (16)
174.22 (19)
−6.8 (3)
119.887
121.222
118.885
120.279
127.776
166.152
-12.531
-4.854
175.972
179.009
177.848
-2.261
119.803
121.340
118.851
120.270
127.707
119.768
121.488
118.738
120.351
126.888
-164.290
14.314
5.757
O1—C7—C6
O1—C7—C8
C6—C7—C8
C9—C8—C7
C8—C9—C10
C1—C6—C7—O1
C5—C6—C7—O1
O1—C7—C8—C9
C6—C7—C8—C9
C7—C8—C9—C10
C8—C9—C10—C11
C8—C9—C10—C15
−176.1 (5) -165.267
3.7 (6)
13.413
4.988
5.6 (3)
−10.0 (6)
167.4 (4)
2.6 (7)
7.2 (8)
-172.683
-177.997
-160.041
20.966
−173.93 (17)
−178.70 (16)
−177.01 (18)
4.1 (3)
179.0 (4)
-175.898
-178.920
1.814
−173.7 (4)
−178.6 (4)
−177.0 (5)
4.4 (8)
-175.187
-178.686
-175.554
4.766
−178.7 (3) 178.1 (4)
−175.2 (4) 1.6 (7)
3.9 (6)
−177.3 (5) -178.342
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Table 3 Hydrogen bond metrics for compounds 1-4.
Bond
Bond length, (Å)
Angle
D—H···A
D—H···A, (°)
D—H
H···A
D···A
Compound 1
C5—H5A···O1i
0.93
2.58
3.251 (10)
3.263 (2)
129
156
Compound 2
C11—H11A···O1ii
Compound 3
0.93
2.39
C1A—H1AA···Cl1Aiii
C11A—H11A···O1Aiv
C13B—H13B···O1Av
C15B—H15B···O1Bvi
Compound 4
0.93
0.93
0.93
0.93
2.77
2.40
2.55
2.42
3.648 (5)
3.294 (5)
3.449 (5)
3.295 (5)
157
162
163
157
C1—H1A···O1vii
0.93
2.50
3.204 (5)
132
Symmetry code (i) −x+3/2, y+1/2, −z+1/2; (ii) −x+1, −y+1, −z; (iii) −x+1, −y+2, −z; (iv) −x+2, −y+1, −z; (v)
x−1, y, z; (vi) −x, −y+1, −z+1; (vii) x, −y+3/2, z+1/2.
Table 4 Halogen…halogen [I…J = F or Br] interactions.
X—I···J
Bond length,
I—J, (Å)
Angle,
X—I···J, (°)
C3—Br1···F1i
C13—F1···Br1ii
C3—Br1···Br1iii
3.215(6)
3.215(6)
3.6196(9)
173.1(3)
152.8(7)
163.47(12)
1
4
Symmetry code (i) -3/2+x,3/2-y,-1/2+z; (ii) 3/2+x,3/2-y,1/2+z; (iii) -x,1/2+y,3/2-z.
Van de Waals radii (Å) : F=1.47 ; Cl=1.76; Br=1.86.
Table 5 Spectral absorption and their respective molecular orbital of chalcones 1-4.
−1
λcw (nm)
λmax (nm)
State
transition
HOMO
(eV)
LUMO
(eV)
H-L gap
(eV)
Eg = hc
λ
max
(eV)
3.962
3.949
4.106
4.079
349
340
342
345
313
314
302
304
n-π*
n-π*
n-π*
n-π*
-6.975
-6.966
-6.966
-6.907
-2.861
-2.961
-2.859
-2.795
4.114
4.005
4.107
4.111
1
2
3
4
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Table 6 The calculated dipole moments (Debye) of compounds 1-4 at B3LYP/6-3111G++(d,p) level of theory.
ꢀx
ꢀy
ꢀz
ꢀtot
(D)
-0.37
-0.63
-0.38
2.04
-2.96
-0.19
-3.44
-4.13
0.03
0.20
0.23
-0.24
2.98
0.68
3.47
4.61
1
2
3
4
Table 7 Nonlinear refractive index of 1-4
1
2
3
4
Intensity (kW/cm2)
n2 (x 10-9 cm2/W)
4.1
8.3
-6.724 ± 0.494
-7.472 ± 0.276
-8.532 ± 0.241
-8.238 ± 2.104
-3.338 ± 0.462
-5.080 ± 0.325
-4.652 ± 0.155
-4.873 ± 0.220
-2.690 ± 0.339
-2.719 ± 0.189
-3.176 ± 0.142
-
-7.376 ± 0.433
-8.202 ± 0.256
-8.373 ± 0.300
-8.307 ± 0.253
12.4
16.5
Scheme 1. Synthesis of halogen chalcone analogues.
28