Growth, crystalline perfection and characterization of benzophenone oxime crystal

Article abstract of DOI:10.1016/j.saa.2012.02.070

Single crystals of benzophenone oxime (BPO) have been grown by slow evaporation solution growth technique from ethanol at room temperature. The single crystal X-ray diffraction study reveals that the crystal belongs to monoclinic system and cell parameter

Full text of DOI:10.1016/j.saa.2012.02.070

Spectrochimica Acta Part A 92 (2012) 207–211
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Growth, crystalline perfection and characterization of benzophenone
oxime crystal
a
a
a
b
c
M. Rajasekar , K. Muthu , V. Meenatchi , G. Bhagavannarayana , C.K. Mahadevan ,
a,∗
SP. Meenakshisundaram
Department of Chemistry, Annamalai University, Annamalainagar 608 002, India
Crystal Growth & X-ray Analysis Activity, CSIR-NPL, New Delhi 110 012, India
Physics Research Centre, S.T. Hindu College, Nagercoil 629002, India
a
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Single crystals of benzophenone oxime (BPO) have been grown by slow evaporation solution growth
Received 1 December 2011
Received in revised form 10 February 2012
Accepted 17 February 2012
technique from ethanol at room temperature. The single crystal X-ray diffraction study reveals that the
crystal belongs to monoclinic system and cell parameters are, a = 9.459 A˚ , b = 8.383 A˚ , c = 26.690 A˚ , v= 2115
A˚ and ˇ = 92.807 . The structure and the crystallinity of the materials were further confirmed by powder
3
◦
X-ray diffraction analysis. The various functional groups present in the molecule are confirmed by FT-IR
analysis. The TG/DSC studies reveal the purity of the material and the crystals are transparent in the entire
visible region having a lower optical cut-off at ∼300 nm. The crystalline perfection was evaluated by high-
resolution X-ray diffraction (HRXRD). The crystal is further characterized by Kurtz powder technique,
dielectric studies and microhardness analysis.
Keywords:
Organic compound
High resolution X-ray diffraction
Single crystal growth
FT-IR
Dielectric properties
© 2012 Elsevier B.V. All rights reserved.
1
. Introduction
Oximes of carbonyl compounds are important because of their
properties of benzophenone oxime have not been reported so far to
the best of our knowledge. In the present study, BPO was purified
and grown as a single crystal using solution growth technique and
the grown crystals were characterized by various techniques.
use in the purification and characterization of carbonyl compounds
and also their use in organic synthesis as intermediates and medic-
inal chemistry [1–4]. Different oximes and their metal complexes
have shown versatile bioactivity as chelating therapy agents, as
drugs and as inhibitors of enzymes [5]. The bulk growth and
properties of benzophenone, substituted benzophenone and its
derivatives [6–16] have been extensively studied. The second har-
monic generation efficiencies of some benzophenone derivatives
2. Experimental
2.1. Synthesis and crystal growth
The BPO was synthesized according to the reported method [19]
with an yield of ∼90%. The product was purified by repeated recrys-
◦
tallization from hot rectified spirit (m.p. ∼ 146 C).
are reported by Frazier et al. [17] and Cockerham et al. [18]. The
growth, crystalline perfection, thermal, mechanical and dielectric
BPO single crystals were grown using slow evaporation solu-
tion growth technique at room temperature. A saturated solution
of BPO in ethanol was prepared and the solution stirred for 2–3 h
at room temperature to obtain a homogeneous solution. A beaker
containing BPO solution was tightly covered with a thin poly-
thene sheet to control the evaporation rate of the solvent and kept
∗ Corresponding author. Tel.: +91 4144 221670.
E-mail address: aumats2009@gmail.com (SP. Meenakshisundaram).
1
386-1425/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2012.02.070

2
08
M. Rajasekar et al. / Spectrochimica Acta Part A 92 (2012) 207–211
Fig. 1. Photographs of as-grown BPO crystals.
Fig. 2. Powder XRD patterns of BPO crystal.
undisturbed in a dust free environment. Numerous tiny crystals
were formed at the bottom of the container due to spontaneous
nucleation. Macroscopic defect-free crystals of BPO were harvested
after 4 days after attaining a suitable size and shape. The pho-
tographs of the as-grown BPO crystals are shown in Fig. 1.
out. A multicrystal X-ray diffractometer developed at National
Physical Laboratory (NPL), New Delhi [21] was used to record high-
resolution rocking or diffraction curves (DCs). In this system, a fine
focus (0.4 mm × 8 mm; 2 kW Mo) X-ray source energized by a well-
stabilized Philips X-ray generator (PW 1743) was employed. The
well-collimated and monochromated MoK␣1 beam obtained from
the three monochromator Si crystals set in dispersive (+, −, −) con-
figuration has been used as the exploring X-ray beam. The diffracted
intensity is measured by using a scintillation counter. The DCs were
recorded by changing the glancing angle (angle between the inci-
dent X-ray beam and the surface of the specimen) around the Bragg
diffraction peak position ꢁB (taken zero as reference point) starting
from a suitable arbitrary glancing angle (ꢁ). The detector was kept at
the same angular position 2ꢁB with wide opening for its slit, the so-
called ω scan [22]. Before recording the diffraction curve, to remove
the non-crystallized solute atoms remained on the surface of the
crystal and also to ensure the surface planarity, the specimens were
first lapped and chemically etched in a non-preferential etchant of
water and acetone mixture in 1:2 volume ratio.
3
. Results and discussion
3.1. Single crystal X-ray diffraction
The as-grown benzophenone oxime crystals were subjected to
single crystal X-ray diffraction analysis using Bruker AXS (Kappa
Apex II) X-ray diffractometer with MoK␣ radiation (ꢀ = 0.71073 A˚ )
to determine unit cell dimensions. The grown crystal is found to
crystallize in the monoclinic system with space group P2 /n. The
1
obtained unit cell parameters are listed in Table 1 and the unit cell
parameters are in good agreement with the reported values [20].
3.2. Powder X-ray diffraction analysis
Fig. 3 shows the high resolution X-ray diffraction curve recorded
for (0 2 0) diffracting planes using MoK␣1 radiation for a typical BPO
single crystal specimen in symmetrical Bragg geometry. On careful
observation, the curve does not seem to be a single peak. The solid
line (convoluted curve) is well fitted with the experimental points
represented by the filled circles. On deconvolution of the diffrac-
tion curve, it is clear that the curve contains an additional peak
As-grown BPO crystal was finely powdered and subjected to
powder XRD analysis using a Philips Xpert Pro Triple-axis X-ray
diffractometer at room temperature using a wavelength of 1.540 A˚
◦
and a step size of 0.008 . The samples were examined with CuK␣
◦
◦
radiation in a 2ꢁ range of 10 –70 . At room temperature all the
observed reflections were indexed. The indexed powder XRD pat-
tern of the as-grown BPO crystal is shown Fig. 2. The well defined
Bragg’s peaks at specific 2ꢁ angles show good crystallinity of the
materials.
ꢀ
ꢀ
which is 320 away from the higher intensity peak. The additional
3.3. High-resolution X-ray diffraction analysis
To evaluate the crystalline perfection of the specimen crys-
tals, high-resolution X-ray diffraction (HRXRD) analysis was carried
Table 1
Single crystal XRD data for as-grown BPO crystal.
Parameters
Reported valuea
Present study
a ( A˚ )
b ( A˚ )
9.466
8.369
26.71
90
92.89
90
9.459
8.383
26.690
90
92.807
90
c ( A˚ )
◦
˛
( )
◦
ˇ ( )
◦
ꢂ ( )
Volume ( A˚ 3
System
)
2113
Monoclinic
2115
Monoclinic
a
Ref. [20].
Fig. 3. HRXRD curves recorded for BPO crystal.

M. Rajasekar et al. / Spectrochimica Acta Part A 92 (2012) 207–211
209
Fig. 4. FT-IR spectrum of BPO crystal.
Fig. 5. UV–vis spectrum of BPO crystal.
peak corresponds to an internal structural low angle boundary. For
a better understanding, the schematic of a structural grain bound-
ary is given as the inset of Fig. 3. As seen in the inset two regions
of the crystal are misoriented by a finite angle say ˛, known as
tilt angle. Tilt angle may be defined as the misorientation angle
between the two crystalline regions on both sides of the structural
grain boundary. The two regions may be perfect. If the value of ˛
Table 2
UV cut-off (ꢀmax) benzophenone and its derivatives.
System
UV cut-off
(nm)
Reference
Benzophenone
∼391
∼340
∼280
∼300
[6]
[10]
[11]
ꢀ
ꢀ
is ≤1 , we may call it as very low angle boundary. If ˛ > 1 but less
than a deg, we call it as low angle boundary. For more details of such
structural grain boundaries including their effect on physical prop-
erties, reference is made available elsewhere [22,23]. The angular
separation between the two peaks gives the tilt angle ˛ which is
Benzophenone hydrazone
Benzophenone semicarbazone
Benzophenone oxime
Present study
BPO crystal and some other benzophenone derivatives are given in
Table 2.
ꢀ
ꢀ
3
20 for the specimen crystal as seen in the figure. The FWHM (full
width at half maximum) of the main peak and the low angle bound-
ꢀ
ꢀ
ary are respectively 430 and 760 . These relatively higher values
reveal the fact that both the regions of the crystal are not that per-
fect. These types of structural defects are probably generated in the
crystals due to mechanical/thermal fluctuations occurred during
the growth process and/or also due to fast growth [24]. It may be
mentioned here that such minute defects could be detected with
well resolved peaks in the diffraction curve only because of the
high-resolution of the diffractometer, characterized by very low
values of wavelength spread i.e. ꢃꢀ/ꢀ and horizontal divergence
for the exploring or incident beam, which are respectively around
3
.6. Mechanical studies
The crystal with 2 mm thickness was used for microhardness
measurements using Reichert 4000E Ultramicrohardness tester.
Vickers microhardness number Hv was calculated using the rela-
2
tion, Hv = 1.8544(P/d ) kg/mm, where P is the applied load, d is
the diagonal length of the indentation impression and 1.8544 is
a constant factor for the diamond pyramid. The hardness number
increases with increase of load (Fig. 6). The relation between load
n
−
5
ꢀꢀ
P and indentation length d is represented by Meyer’s law P = Ad ,
1
0
and much less than 3 of the multicrystal X-ray diffractometer
where n is the Meyer index of work hardening exponent and A is
constant for a given material. Since the value of n is greater than 2,
the hardness of the material is found to increase with the increase
of load confirming the prediction of Onitsch [25]. The n value of
used in the present studies.
3.4. FT-IR analysis
The FT-IR spectrum was recorded for BPO crystal using
an AVATAR 330 FTIR by KBr pellet technique in the range
−
1
1
of 400–4000 cm
3
(Fig. 4). An absorption band in the region
−
000–3100 cm is due to C H stretching frequency of aromatic
−1
ring. The band at 1490 cm is due to C C stretching frequency of
aromatic ring. The broad band appeared at 3250 cm is due to OH
stretching frequency of benzophenone oxime.
−
1
3.5. Optical studies
Optical absorption spectrum of the grown benzophenone oxime
single crystal was recorded in the wavelength region from 100 to
200 nm using Perkin-Elmer Lambda 35 UV–vis spectrophotome-
1
ter. The as-grown benzophenone oxime single crystal was polished
and the good transparent single crystal with 2 mm thickness was
used for the optical studies. The spectrum (Fig. 5) shows that the
absorption is minimum in the entire visible region and cut-off
wavelength is around ∼300 nm. The UV cut-off wavelengths of the
2
Fig. 6. The plot of Vickers hardness number (kg/mm ) vs load (g) for BPO crystal.

2
10
M. Rajasekar et al. / Spectrochimica Acta Part A 92 (2012) 207–211
Fig. 7. TG/DSC curve of BPO crystal.
as-grown BPO crystal is 5.74 and the crystal belongs to the soft
material category.
3.7. Thermal studies
The TG/DSC analysis of BPO crystal was carried out between 20
◦
and 800 C in the nitrogen atmosphere (Fig. 7). It shows that there
is no physically adsorbed water in the molecular structure of the
◦
crystal. TG curve illustrates a single stage weight loss ∼200 to 300 C
due to decomposition of BPO into fragments and their subsequent
◦
volatilization. In DSC, a sharp endothermic peak at ∼149 C is due
to the melting point of the material and it was confirmed by using
◦
Sigma instrument melting point apparatus (146 C). A high intense
◦
exothermic peak appearing close to ∼200 C is matching with the
major weight loss in TG curve. The sharpness of the endothermic
peak shows good degree of crystallinity and purity of the as-grown
crystal.
3.8. Dielectric properties
Dielectric measurements were carried out by the parallel plate
capacitor method as a function of temperature for various fre-
quencies using a Precision LCR meter (AGILENT 4284 A model).
Fig. 8(a)–(c) is the plots of dielectric constant (εr), dielectric loss
Fig. 8. (a) Plot of dielectric constant vs temperature (K) for BPO crystal. (b) Plot of
dielectric loss vs temperature (K) for BPO crystal. (c) Plot of AC electrical conductivity
vs temperature (K) for BPO crystal.
(
tan ı) and AC conductivity (ꢄac) versus temperature at different
frequencies. It can be seen that dielectric parameters, viz. dielec-
tric constant, dielectric loss and AC conductivity increase with the
increase in temperature. The εr and tan ı values decrease with
increase in frequency while ꢄac increases with increase in fre-
quency. The dielectric constant of material is generally composed
of four different types of contributions like ionic, electronic, orien-
tational and space charge polarizations. The large value of dielectric
constant at low frequencies may be due to contribution of all these
polarizations. The decreased dielectric constant at higher frequen-
cies could be due to the reduction in the space charge polarization.
Space charge polarization is generally active at lower frequen-
cies and high temperatures indicating the purity and perfection
of the grown crystal [26]. The increase in conductivity could be
attributed to reduction in the space charge polarization at higher
frequencies [27]. In the present study, dielectric constant varying
proportionally with temperature is essentially due to the tempera-
ture variation of the polarizability [28]. The low εr value dielectric
materials have potential applications in microelectronic industries.
a uniform particle size of 125–150 ␮m and then packed in a micro
capillary of uniform bore and exposed to laser radiation. Contrary
to earlier reports [18] no green light emission is observed. This
is in tune with the single crystal XRD observations of this spec-
imen crystallizing in a centrosymmetric space group [20]. It has
been established that benzophenone oxime is a dimer and the cen-
trosymmetry could be due to this structural arrangement. A pseudo
symmetrical dimer, held together in the crystal by van der Waals
interactions, is formed by means of O H· · ·N hydrogen bonds. Con-
trary to the belief that the hydrogen bonding generally leading
to noncentrosymmetric structures, the NLO inactivity of ben-
zophenone oxime has been experimentally observed. It has been
reported that benzophenone [7], benzophenone hydrazone [10],
Table 3
SHG output of benzophenone and its derivatives.
System
SHG efficiency
Reference
Benzophenone
Benzophenone hydrazone
Benzophenone
3 times higher than KDP
10 times higher than KDP
(Green light emission)
[7]
[10]
[11]
3.9. Second harmonic generation (SHG) efficiency
The SHG test on the crystal as performed by Kurtz powder
semicarbazone
Benzophenone
thiosemicarbazone
Benzophenone oxime
0.52 times that of Urea
[13]
SHG method [29]. An Nd:YAG laser with a modulated radiation of
064 nm was used as the optical source and directed on the pow-
dered sample through a filter. The grown crystals were ground to
1
(No green light emission)
Present study

M. Rajasekar et al. / Spectrochimica Acta Part A 92 (2012) 207–211
211
benzophenone semicarbazone [11] and benzophenone thiosemi-
carbazone [13] exhibit SHG emitting a green light on exposure to
064 nm Nd:YAG laser (Table 3). In these crystals there is a favor-
able molecular arrangement facilitating nonlinearity.
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Single crystals of benzophenone oxime (BPO) were grown from
their ethanol solution using slow evaporation solution growth tech-
nique for the first time. The product formation was qualitatively
confirmed by FT-IR. The powder X-ray diffraction and HRXRD stud-
ies reveal the structure and crystalline perfection of the grown
crystal. The additional peaks in HRXRD indicate the formation of
low angle structural grain boundaries. Thermal analysis confirms
no decomposition of the crystal up to the melting point. The opti-
cal absorption shows excellent transmission in the entire visible
region. The dielectric constant, dielectric loss and AC conductiv-
ity establish a normal behavior. Mechanical study on the crystals
confirms the hardness behavior of the material. Studies reveal that
this crystal is a promising material for the device fabrications in
microelectronic industries.
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Acknowledgement
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One of the authors, K. Muthu is thankful to CSIR, New Delhi, for
the award of a Senior Research Fellowship.
1
[
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