Synthesis, growth, structure and characterization of chalcone crystal: A novel organic NLO material

Article abstract of DOI:10.1016/j.molstruc.2016.02.099

Single crystals of a chalcone, (E)-3-(4-bromophenyl)-1-(2-hydroxyphenyl)prop-2-en-1-one (BHP), were grown by the slow evaporation solution growth technique. The structure is elucidated by single-crystal X-ray diffraction analysis and the crystal belongs t

Full text of DOI:10.1016/j.molstruc.2016.02.099

Accepted Manuscript
Synthesis, growth, structure and characterization of chalcone crystal: A novel organic
NLO material
R. Agilandeshwari, V. Meenatchi, S.P. Meenakshisundaram
PII:
S0022-2860(16)30193-4
10.1016/j.molstruc.2016.02.099
MOLSTR 22308
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 1 December 2015
Revised Date: 28 February 2016
Accepted Date: 29 February 2016
Please cite this article as: R. Agilandeshwari, V. Meenatchi, S. Meenakshisundaram, Synthesis, growth,
structure and characterization of chalcone crystal: A novel organic NLO material, Journal of Molecular
Structure (2016), doi: 10.1016/j.molstruc.2016.02.099.
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Graphical abstract

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Synthesis, growth, structure and characterization of chalcone crystal:
A novel organic NLO material
R. Agilandeshwaria, V. Meenatchia,b and SP. Meenakshisundarama
aDepartment of Chemistry, Annamalai University, Annamalainagar-608 002, Tamil Nadu, India.
bDepartment of Chemistry, Sri Vijay Vidyalaya College of Arts and Science (women),
Nallampalli, Dharmapuri - 636 807, Tamil Nadu
Abstract
Single crystals of a chalcone, (E)-3-(4-bromophenyl)-1-(2-hydroxyphenyl)prop-2-en-1-
one (BHP), were grown by the slow evaporation solution growth technique. The structure is
elucidated by single-crystal X-ray diffraction analysis and the crystal belongs to the monoclinic
system with noncentrosymmetric space group P21. Optical studies reveal that the absorption is
minimum in the visible region and the cut-off wavelength is at ~ 468 nm. The band-gap energy
was estimated by the application of the Kubelka–Munk algorithm. The powder X-ray diffraction
pattern reveals the good crystallinity of the as-grown specimen. The vibrational patterns in
FT–IR are used to identify the functional groups and thermal studies indicate the stability of the
material. The second harmonic generation efficiency (SHG), as estimated by Kurtz and Perry
powder technique, reveals the superior nonlinear optical character of this material. Hirshfeld
surface analysis is done to quantify the intermolecular interactions, responsible for developing a
nonlinear atmosphere. As-grown crystals were further characterized by SEM, NMR, mass
spectrometry and elemental analysis.
Corresponding author
Tel: 0091-4144-221670
Email: aumats2009@gmail.com
.

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Keywords
X–ray diffraction, Optical properties, Thermal analysis, Hydrogen bonding interactions, SHG
efficiency.
1. Introduction
Chalcones and their derivatives possess antioxidant, antibacterial, antifungal, antitumor and
anti–inflammatory properties [1–4]. Organic molecules exhibiting second–order nonlinear
optical (NLO) properties have been synthesized and designed for application in optical
communications, optical computing, data storage, harmonic generators, frequency mixing and
optical switching [5,6]. Among many organic NLO materials, chalcone derivatives are known
for their excellent blue light transmittance [9–11]. Recently, we have investigated the synthesis,
structure, growth and characterization of some chalcones [12-17]. Mostly they crystallize
centrosymmetrically and nonlinearity is not sustained at the macro level due to orientation and
packing. Interestingly, the title compound crystallizes in a polar space group. The growth,
structure, characterization and NLO response of (E)-3-(4-bromophenyl)-1-(2-hydroxy-
phenyl)prop-2-en-1-one (BHP) are reported in the present study.
2. Experiments
2.1. Synthesis
BHP was synthesized by Claisen–Schmidt condensation reaction [18]. The analytical grade
starting materials, p-bromo- benzaldehyde (Sigma Aldrich) and o-hydroxyacetophenone (Sigma
Aldrich) were used as such. 10 % sodium hydroxide solution was taken in a conical flask. A
mixture of p-bromobenzaldehyde (0.01 mol) and o-hydroxyacetophenone (0.01 mol) dissolved in
ethanol (50 ml) was added dropwise to the conical flask with vigorous stirring (Scheme 1).

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During the synthesis, the temperature was maintained between 20–25 °C. After completely
adding the aldehyde–ketone mixture, the solution was stirred for another 60 min. Then the
reaction mixture was poured in ice cold water and neutralized with dilute hydrochloric acid. The
separated product was then filtered and washed with excess of water and finally dried. The
synthesized crude sample was purified by successive recrystallizations from ethanol.
2.2. Crystal growth
The crystals were grown by the slow evaporation technique at room temperature. A
saturated solution of BHP was obtained by dissolving the sample in ethanol with continuous
stirring at room temperature. This solution was filtered using filter paper, slightly warmed and
allowed to evaporate very slowly. After about 7 days, good quality, transparent, needle shaped
pale yellow crystals started growing. The photographs of the needle shaped as–grown crystal are
shown in Fig. 1.
3. Results and Discussion
3.1 . FT-IR spectroscopy
FT–IR spectrum of as–grown specimen (Fig. 2) was recorded using AVATAR 330 FT–IR by
KBr pellet technique in the spectral range of 400–4000 cm-1. The sharp absorption band at
~1658 cm-1 is due to carbonyl stretching of α,β–unsaturated carbonyl group. The medium
intensity bands around ~2923 and ~2854 cm-1 are due to aliphatic C-H stretching vibrations. The
sharp absorption band at ~668 cm-1 is assigned to C-Br stretching vibration. The strong
absorption bands at ~1604 and ~1485 cm-1 are corresponding to C=C stretching vibration. The
observed FT–IR vibrational bands are listed in Table S1.

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3.2 . Powder X-ray diffraction analysis
BHP was finely powdered and subjected to powder XRD analysis using a Philips X’pert Pro
Triple-axis X–ray diffractometer at room temperature using a wavelength of 1.540 Å and a step
size of 0.008°. The samples were examined with Cu Kα radiation in 2θ range of 10–50°. The
indexed powder XRD pattern of as–grown specimen is shown in Fig. S1 along with simulated
one. The XRD profiles show that a sample is of single phase without any detectable impurity.
The well defined Bragg’s peaks at specific 2θ angles show high crystallinity of the material.
Most of the peak positions in powder method and simulated XRD pattern derived from single
crystal XRD coincide. Differences in mosaic spread of powder and single crystal patterns, and
preferred orientations of the sample possibly result in significant intensity variations, as
expected.
3.3. Thermal study
In order to test the thermal stability of BHP the thermogravimetric analysis (TG) and
differential thermal analysis (DTA) have been carried out simultaneously using NETZSCH STA
449F3 thermal analyzer in nitrogen atmosphere. The TG/DTA thermogram of the BHP is shown
in Fig. S2. Weight losses due to decomposition are observed at ~230 and 280 °C. An
endothermic transition at ~130 °C indicates the melting point of the specimen and it was
confirmed by using Sigma instrument (127–131 °C) melting point apparatus. The absence of
endo or exothermic transition below 130 °C indicates the crystal stability.

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3.4. Scanning electron microscopy (SEM)
The SEM images were taken at maginification values for 250X and 500X with maximum
values of 15 kV using a JEOL JSM 5610 LV scanning electron microscope. The SEM images
are shown in Fig. 3. Bar like shape with surface imperfections are observed.
3.5. Optical studies
Diffuse reflectance spectra of the samples were recorded in the region 200-800 nm using the
DRA-CA-30I accessory and converted to absorption spectra using the Kubelka–Munk function.
The UV-DRS spectrum was measured in the region of 200–800 nm. The optical reflection
spectrum (Fig. S3 see supplementary data) shows good reflectance in the visible region and the
lower cut–off wavelength is ~468 nm. The Kubelka – Munk theory [19] provides a correlation
between reflectance and concentration. From the Tauc plots, [F(R)hv] as a function of hv where
F(R) is Kubelka – Munk fuction, indirect and direct band gap energies of the specimen are
deduced as 2.69 and 2.89 eV respectively, as shown in Fig. 4.
3.6. Nuclear magnetic resonance (NMR) spectroscopy
1H NMR and 13C NMR spectra were recorded on BRUKER AVIII 400 MHz NMR
1
spectrometer operating at 400.13 MHz for H and 100.61 MHz for 13C using standard
parameters. BHP is dissolved in 0.5 ml of CDCl3 solvent and TMS (tetramethylsilane) was used
as an internal standard.
The 1H-NMR spectrum of BHP is shown in Fig. S4a (see supplementary data). There is
a sharp singlet at 12.77 ppm corresponding to OH proton of the phenolic group. The two

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doublets at 9.26 and 7.86 ppm are due to α,β-unsaturated proton of the aliphatic group. The
aromatic phenyl protons appeared in the range of 6.95-7.67 ppm corresponding to eight protons.
The 13C-NMR spectrum is shown in Fig. S4b (see supplementary data). The weak
signal at 193.5 ppm corresponds to the carbonyl carbon. The hydroxyl substituted carbon
appeared at 163.6 ppm. The signals at 144.0 and 118.9 ppm are due to α,β-unsaturated carbon.
The aromatic phenyl carbons appeared in the range of 118.7-136.6 ppm.
3.7. Mass spectrometry
Mass spectra were recorded on a LCMS-2010A Report spectrometer using electron
impact technique (Fig. S5) (see supplementary data). The molecular ion peak observed at
m/z = 303 [(M)+] is in good agreement with the calculated molecular weight. These observations
are well supported by single crystal XRD analysis.
3.8. Elemental analysis
Elemental data are collected by FLASH EA 1112 series of CHN analysis. BHP was
finely powdered and subjected to elemental analysis. The calculated values of carbon and
hydrogen coincide with experimental values (Fig. S6) (see supplementary data). Molecular
formula = C15H11BrO2; C = 59.43 (cal), 59.62 (exp); H= 3.66 (cal), 3.58 (exp).
3.9. Single crystal X-ray diffraction analysis
The structural analysis of BHP was carried out for a selected sample of approximately
0.25 x 0.16 x 0.10 mm3 using Bruker AXS (Kappa APEXII) X–ray diffractometer with
Mo Kα radiation (λ = 0.71073 Å). The structures were solved and refined by full matrix least
squares on F2 with WinGx software package utilizing SHELXS97 and SHELXL97 modules.

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It belongs to the monoclinic system with noncentro- symmetric space group P21 and the cell
parameters are, a = 6.9540 (6) Å, b = 4.0025 (3) Å, c = 22.8414 (18) Å, α = 90°, β = 94.768
(3)°, γ = 90°, V = 633.55 (9) Å3 and Z = 2. The ORTEP and packing diagram are shown in
Fig. 5 and the crystal data are listed in Table 1. The crystal stability and cohesion are
achieved by intermolecular C-HꢀꢀꢀO hydrogen bonds. Crystal packing diagram along ‘a’ and
‘b’ axis are shown as Figs. 6-7.
3.10. Hirschfield surface analysis
Hirshfeld surfaces are generated from the crystal data using the DFT method with 6-
31G(d) as basis set. The Hirshfeld surfaces of BHP are displayed in Fig. 8, showing surfaces that
have been mapped over a dnorm, de, di, shapeindex and curvedness [20-22]. The surfaces
representing the circular depressions (deep red) visible on the Hirshfeld surface are indicative of
hydrogen bonding contact spots due to O-H…O (7.5 %) interactions (Fig. 8a) and O…H
(7.5 %), H…O (6.5 %), H…H (41.2 %), Br…H (7.6 %) contacts (Fig. 8c). The deep red colour
spots in di (Fig. 8d) are strong interactions such as H…Br (4.1%), H…H (41.2 %) and H…O
(6.5 %). The shapeindex (Fig. 8b) surface indicates the electron density surface shape around the
molecular interactions. The small range of area and light color on the surface represents a weaker
and longer contact other than hydrogen bonds. The curvedness surface (Fig. 8e) indicates the
electron density surface curves around the molecular interactions. The surfaces in the crystal
packing along the b-axis (Fig. 9) clearly indicate the C-H…O interactions. Graphical images of
crystal voids, empty regions present in the crystal lattice packing along a, b and c axes are shown
in Fig. 10. The deformation density represents difference between the total electron density of a
molecule and the electron density of "neutral spherical unperturbed atoms" superimposed at the

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same of the molecule. Deformation density clearly explains the surface interaction energy of
every atom and bond present in the BHP as shown in Fig. 11.
3.11 Fingerprint analysis
Fingerprint plots [23] are generated from the crystal data using the DFT method with
6-31G(d) as basis set for evidencing and quantifying the intermolecular interaction patterns. The
O…H (7.5 %) interactions are represented by a spike in the bottom area (Fig. 12) whereas the
H…O (6.5 %) interactions by a spike in the top left region. Hydrogen-hydrogen interactions,
H…H (41.2 %) are very high compared to the other bonding interactions. Sharp curved spike at
the bottom right area indicates the Br…H (7.6 %) and top left corner with curved spike indicates
the H…Br (4.1 %). The finger print at the bottom right area represents C…H (6.0 %) interactions
and top right area represents H…C (4.0 %) interactions. The finger print at the top centre area
represents C…Br (1.1 %), Br…C (1.2 %), C…C (15.8 %), O…O (0.8 %), C…O (0.4 %), O…C
(0.4 %) and Br…Br (3.2 %) interactions. Strong interactions occupy more space and weak
interactions occupy less space in the fingerprint plot. The combination of de and di in the form of
a two-dimensional fingerprint plot provides a summary of intermolecular contacts in the crystal.
Relative contributions of various intermolecular interactions in BHP are shown in Fig. 13.
3.12 Second harmonic generation efficiency
In order to confirm the influence of the nonlinear optical properties of the as-grown
specimen, it was subjected to SHG test using Kurtz and Perry [24] technique. The output gives
relative nonlinear optical efficiencies of the measured specimens. The doubling of frequency
was confirmed by the green color of the output radiation of characteristic wavelength
532 nm. With an input beam energy of 5.70 mJ/pulse, KDP sample was used as reference

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material (I2ω =102 mV) and the powder SHG efficiency of BHP was found to be superior to that
of KDP (I2ω= 536 mV).
Large first-order hyperpolaraizability (β) of magnitude about 85 times that of urea, as
estimated by density functional theory (DFT) method with 6-31G(d,p) as the basis set and a
significant SHG- activity nearly five times that of KDP clearly substantiate the NLO response of
the chalcone. Higher the β, highest the charge transfer.
Organic molecules containing extended π-conjugation are characterized by large values of
the second harmonic generation efficiency showing significant NLO activity. The strong inter-
and intramolecular hydrogen bonding enhances charge transfer and it is responsible for nonlinear
optical character.
4. Conclusion
Transparent needle like crystals of (E)-3-(4-bromophenyl)-1-(2-hydroxyphenyl)prop-2-
en-1-one were grown in ethanol by the slow evaporation solution growth technique at room
temperature. The product formation was confirmed by FT–IR, NMR, LC–Mass, elemental
analysis and single crystal XRD analysis. The crystallographic data indicate that the specimen
crystallizes in the monoclinic system with noncentrosymmetric space group P21. TG/DTA study
reveals the purity of the sample and no decomposition is observed up to the melting point. The
analysis of the Hirshfeld surface derived fingerprint plots is shown to be an effective method to
identify and quantify various types of intermolecular interactions. A superior SHG-activity
clubbed with high β caused by inter- / intramolecular interactions and close packing prove this
chalcone as a promising NLO candidate.

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Supporting Information
CCDC 1043959 contains the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data request/cif. Supplementary information contains Powder X-ray
diffraction, thermal study, UV-DRS, NMR, LC-mass, elemental analysis and FT-IR table.
Acknowledgements
The authors thank the UGC-Networking Resource Centre, School of Chemistry,
University of Hyderabad, for providing characterization facility. One of the authors
Dr. V. Meenatchi expresses her sincere gratitude to Dr. R. Chandrasekar, Associate Professor,
for providing lab facilities in University of Hyderabad. The authors thank the Council of
Scientific and Industrial Research (CSIR), New Delhi, for financial support through research
grant No.03(1233)/12/EMR-II and Dr. V. Meenatchi is grateful to CSIR project for the award of
Research Associate (RA).
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Table 1. Crystal data and structure refinement for BHP
Empirical formula
Formula weight
Temperature
C15H11BrO2
303.15
296(2) K
Wavelength
0.71073 Å
Monoclinic, P21
Crystal system, space group
a = 6.9540(6) Å, α= 90°
Unit cell dimensions
b = 4.0025(3) Å, β = 94.768(3)°
c = 22.8414(18) Å, γ = 90°
Volume
633.55(9) Å3
Z, calculated density
Absorption coefficient
F(000)
2, 1.589 Mg/m3
3.234 mm-1
304
Crystal size
0.250 x 0.160 x 0.100 mm3
0.895 to 22.602 °.
-6 ≤ h ≤ 7, -4 ≤ k ≤ 3, -23 ≤ l ≤ 24
3211 / 1633 [R(int) = 0.0249]
99.7 %
Theta range for data collection
Limiting indices
Reflections collected/unique
Completeness to theta = 22.20
Absorption correction
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2sigma(I)]
R indices (all data)
None
Full-matrix least-squares on F2
1633 / 2 / 168
1.046
R1 = 0.0394, wR2 = 0.0953
R1 = 0.0464, wR2 = 0.0992
0.016(11)
Absolute structure parameter
Extinction coefficient
0.002(4)
Largest diff. peak and hole
0.678 and -0.566 e. Å-3

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Figure captions
Fig 1. Photographs of BHP.
Fig 2. FT–IR spectrum of BHP.
Fig 3. SEM images of BHP.
Fig 4. Tauc plot of BHP (a) direct and (b) indirect band gap energy.
Fig 5. (a) ORTEP (b) packing diagram of BHP.
Fig 6. Crystal packing diagram of BHP along ‘a’ axis.
Fig 7. Crystal packing diagram of BHP along ‘b’ axis.
Fig 8. Hirshfeld surfaces of BHP (a) dnorm (b) Shapeindex (c) de (d) di (e) curvedness.
Fig. 9. Hirshfeld surfaces: (a) dnorm in crystal packing with H-bond contacts, (b) Shapeindex in
crystal packing, (c) Curvedness in crystal packing, (d) de surface in crystal packing, and (e) di
surface in crystal packing.
Fig 10. (a) Crystal voids in packing along the a axis (b) Crystal voids in packing along the b axis
(c) Crystal voids in packing along the c axis.
Fig 11. (a) Deformation density and (b) hydrogen bonding interactions along with deformation
density of BHP.
Fig 12. Fingerprint plots representing quantity of molecular interactions of BHP.
Fig 13. Quantities of molecular interactions represented in a pie chart.

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Fig. 1

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100
80
60
40
20
4000
3000
2000
1000
Wavenumber (cm-1)
Fig. 2

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(a)
(b)
Fig. 3

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(a)
3
2
1
0
2.89 eV
1.5
2.0
2.5
3.0
1.5
1.0
0.5
0.0
(b)
2.69 eV
1.5
2.0
2.5
3.0
3.5
Photon energy (eV)
Fig. 4

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(a)
(b)
Fig. 5

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Fig. 6

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Fig. 7

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(b)
(a)
(d)
(c)
(e)
Fig. 8

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(b)
(c)
(a)
(e)
(d)
Fig. 9

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(a)
(b)
(c)
Fig. 10

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(a)
(b)
Fig. 11

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Fig. 12

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Fig. 13

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OH
CHO
OH
O
COCH3
10%NaOH
Ethanol
+
Br
Br
Scheme 1