Growth, optical, luminescence, thermal and mechanical behavior of an organic single crystal: 3-Acetyl-2-methyl-4-phenylquinolin-1-ium chloride

Article abstract of DOI:10.1016/j.saa.2013.12.041

A single crystal of 3-acetyl-2-methyl-4-phenylquinolin-1-ium chloride has grown by slow evaporation solution growth technique using ethanol as solvent. The structural, thermal, optical and mechanical property has studied for the grown crystal. Single crystal XRD revealed that the crystal belongs to monoclinic system with space group P2₁/c. The presences of Functional groups in the crystallized material have confirmed using the FTIR vibrational spectrum. The optical absorbance spectrum recorded from 190 to 1100 nm shows the cut-off wavelength occurs at 371 nm. The material shows its transparency in the entire region of the visible spectrum. The photoluminescence spectrum shows the ultraviolet and blue emission in the crystal. Thermogravimetric and differential thermal analysis reveal the thermal stability of the grown crystal. Etching study shows the grown mechanism and surface features of the crystal. Vickers microhardness studies have carried out on the (01-1) plane to understand the mechanical properties of the grown crystal. The hardness of the title compound increases on increasing the load. The Meyer's index number (n), and the stiffness constants for different loads has calculated and reported.

Full text of DOI:10.1016/j.saa.2013.12.041

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 78–84
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Growth, optical, luminescence, thermal and mechanical behavior
of an organic single crystal: 3-Acetyl-2-methyl-4-phenylquinolin-1-ium
chloride
b
b
M. Nirosha a, S. Kalainathan a, , S. Sarveswari , V. Vijayakumar
⇑
a Center for Crystal Growth, VIT University, Vellore 632 014, India
b Centre for Organic and Medicinal Chemistry, VIT University, Vellore 632 014, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
3A4MPQ have grown by slow
evaporation solution growth
technique.
ꢀ
The lattice parameters and
morphology have identified by single
crystal X-ray diffraction.
ꢀ
ꢀ
ꢀ
The cut-off wavelength has found to
be 371 nm.
The melting point of the material is
156°C, and it is stable up to 228°C.
Micro hardness and etching studies
have performed for the grown crystal.
a r t i c l e i n f o
a b s t r a c t
Article history:
A single crystal of 3-acetyl-2-methyl-4-phenylquinolin-1-ium chloride has grown by slow evaporation
solution growth technique using ethanol as solvent. The structural, thermal, optical and mechanical
property has studied for the grown crystal. Single crystal XRD revealed that the crystal belongs to mono-
clinic system with space group P21/c. The presences of Functional groups in the crystallized material have
confirmed using the FTIR vibrational spectrum. The optical absorbance spectrum recorded from 190 to
1100 nm shows the cut-off wavelength occurs at 371 nm. The material shows its transparency in the
entire region of the visible spectrum. The photoluminescence spectrum shows the ultraviolet and blue
emission in the crystal. Thermogravimetric and differential thermal analysis reveal the thermal stability
of the grown crystal. Etching study shows the grown mechanism and surface features of the crystal. Vick-
ers microhardness studies have carried out on the (01-1) plane to understand the mechanical properties
of the grown crystal. The hardness of the title compound increases on increasing the load. The Meyer’s
index number (n), and the stiffness constants for different loads has calculated and reported.
Ó 2013 Elsevier B.V. All rights reserved.
Received 12 September 2013
Received in revised form 18 November 2013
Accepted 5 December 2013
Available online 17 December 2013
Keywords:
Crystal growth
Optical properties
Thermo gravimetric analysis
Luminescence
Mechanical studies
Etching studies
Introduction
activities, biological activities, polymer chemistry, electronics and
optoelectronics etc. [1–3]. Quinoline derivatives have found to pos-
Quinolines constitute an important class of nitrogen containing
heterocyclic compounds due to their different application in
various areas. They find applications as pharmacological
sess significant activities in antimicrobial, antimalarial, anti HIV
and anticancer activities [4–7]. These kinds of nitrogen containing
heterocyclic compounds exhibit extraordinary optical-electric
properties in nonlinear optical fields and attract interest to their
electron-deficient nature which may be developed in organic
light-emitting diodes (OLEDs) and display technologies [8,9]. The
⇑
Corresponding author. Tel.: +91 416 2202350; fax: +91 416 2243092.
E-mail address: kalainathan@yahoo.com (S. Kalainathan).
1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.12.041

M. Nirosha et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 78–84
79
challenging goal of OLED has clearly connected to the commercial-
ization of full-color flat-panel displays. The OLEDs technology has a
large area of applications from small mobile phone displays to TV
and monitors. The research in OLEDs has become one of the most
exciting topics in the field of chemistry, physics and materials
science. Quinoline based molecules have suggested as electron
transport and hole blocking materials for electroluminescent
devices [10]. Recently Quinolines conjugated derivatives have gen-
erated considerable interest as blue emitting material [11,12]. In
this rapid growing field, some researchers focused on the synthetic
manipulation of quinoline derivatives with the aim of achieving
stable OLEDs with high brightness and external quantum
efficiency. Further improvement on the essential characteristics
needs a detailed knowledge concerning the fundamental electronic
and optical properties of organic molecules. In the present investi-
gation,
3-acetyl-2-methyl-4-phenylquinolin-1-ium
chloride
3A4MPQ has grown by slow evaporation solution growth method
and the structural, optical, thermal, mechanical; luminescence
and etching properties of the title compound have analyzed which
has closely related to optoelectronic applications.
Fig. 1. Solubility curve of 3A4MPQ.
Experiment
Synthesis
The material has synthesized by following the method of Kiran
et al. [13]. A mixture of 2-aminobenzophenone (0.01 M), acetyl
acetone (0.01 M) and a catalytic amount of concentrated HCl have
irradiated under 240 W for about 5 min. The resultant solid have
filtered, dried and purified by column chromatography using a
1:1 mixture of ethyl acetate and petroleum ether, and recrystal-
lized using ethanol.
Solubility
The solubility of 3A4MPQ has determined in the temperature
range 30–50 °C. This process has repeated for every 5 °C using an
ultra cryostat with accuracy of 0.01 °C. The concentration of the
solute has determined gravimetrically. The solubility for 30 °C
has determined by dissolving 3A4MPQ salt in 100 ml of ethanol ta-
ken in an air tight container maintained at the temperature with
continuous stirring of the solution. In the saturated solution, 5 ml
has pipetted out and then poured into a Petridish of known weight.
The amount of the salt present in 5 ml of the solution has mea-
sured by subtracting the empty beaker’s weight. From this, amount
of the salt present in 100 ml of the solution have found out. In the
same way, the amount of salt dissolved in 100 ml at 35, 40, 45,
Fig. 2a. Grown crystal of 3A4MPQ.
50 °C has determined. Fig.
1 shows the solubility curve of
3A4MPQ salt. From the solubility diagram, (Fig. 1) it has observed
that the solubility of the material increases with an increase in
temperature, exhibiting a high solubility gradient and positive
coefficient.
Fig. 2b. Molecular structure of 3A4MPQ.
Crystal growth
transparent single crystal of size 4 mm ꢁ 4 mm ꢁ 2 mm have
obtained in a period of 10 days. The photographs of the as grown
3A4MPQ crystal have shown in Fig. 2a respectively.
The single crystal of 3A4MPQ has grown using slow evaporation
technique at ambient temperature. The Purified salt has used for
growing bulk single crystals. A saturated solution has prepared at
room temperature by using ethanol as a solvent. The temperature
of the solution has risen by 5 °C above the room temperature in or-
der to obtain a homogeneous solution in ethanol. The filtered solu-
tion has risen by 3 °C above the room temperature. Defect free seed
crystal has introduced into the mother solution. The beaker
containing the saturated solution has optimally covered with
perforated sheet for controlled evaporation of the solvent. A
Characterization studies
The single crystal X-ray diffraction (XRD) analysis of 3A4MPQ
crystal have carried out using ENRAF NONIUS X-ray diffractometer
and its unit cell dimensions, and morphology has determined. The
purity and crystalline nature of 3A4MPQ compound has confirmed

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M. Nirosha et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 78–84
by recording powder X-ray diffraction pattern using a REICH SIEF-
ERT X-ray diffractometer employing Cu K (1.54058 Å) in the
a
range of 10–70° in the steps of 0.02°. The FTIR analysis of the
grown crystal has recorded in the range 400–4000 cmꢂ1. It has car-
ried out using FT-IR 4100 type-A spectrophotometer employing
KBr pellet technique at room temperature. The UV–vis spectrum
has recorded for the grown crystal using ELICO SL 218 double beam
UV–vis spectrophotometer, in the range 190–1100 nm. The ther-
mal analyses have carried out using a SDT Q600 V8 apparatus at
a heating rate of 10 °C/min in the temperature range 30–1000 °C
at nitrogen atmosphere. The PL spectrum have recorded using Jo-
bin Yvon-Spex spectrofluorometer (Fluorolog version 3: Model
FL3-11) at room temperature; 450 W high pressure xenon lamp
acts as an excitation source. Etch patterns have analyzed using a
Carl Zeiss metallurgical microscope (Axios kop 40 MAT) in the
reflection mode. Micro hardness studies have carried out with
Mututoyo MH-112 micro hardness tester using Vickers diamond
pyramidal indenter attached to a metallurgical microscope.
Fig. 4. Powder XRD pattern of 3A4MPQ.
presence of CAH bond present in the 1st ring (Fig. 2b) of the com-
pound. The peak observed at 536.21 cmꢂ1
,
709.80 cmꢂ1
,
Results and discussion
767.67 cmꢂ1 and 833.25 cmꢂ1 is due to the presence of the CAH
bond present in the second ring of the compound. The peak ob-
served at 3049.46 cmꢂ1 is due to the presence of CAH bond present
in the 3rd ring of the compound.
Single crystal X-ray diffraction
The grown crystals have subjected to single crystal X-ray dif-
fractometer with Mok
a radiation of wavelength k = 0.71073 Å is
UV–visible spectrum
to determine the unit cell dimensions and morphology. The lattice
parameters are a = 9.4056 Å, b = 8.5787 Å and c = 18.2538 Å with
space group symmetry P21/c. From the data, it has observed that
it belongs to monoclinic system. The observed lattice parameters
have found to be in good agreement with the reported values
[13]. The morphology of the grown crystal as shown in Fig. 3
The UV–vis–NIR spectrum gives information about the struc-
ture of the molecule. The absorption of UV and visible light in-
volves promotion of the electron in the
ground state to higher states [15]. The absorbance spectrum has
recorded for the 2 mm thickness crystal in the range 190–
1100 nm and it as shown in Fig. 6. The transmittance is high in
the visible region of the spectrum. There is no significant absorp-
tion in the range 372–1100 nm. The cut-off wavelength is
r and p orbital from the
Powder X-ray diffraction
The well defined Bragg’s peaks at particular 2 theta angles in the
powder XRD spectrum have shown in Fig. 4. The peaks have in-
dexed using APPLEMAN program from the 2 theta values.
371 nm. The peak observed at 371 nm is due to
p–
p* transition
contributed by the quinoline backbone. The low cut-off wave-
length and greater transparency in the visible region make it a suit-
able material for optoelectronic applications [16]. The optical
FTIR spectral analysis
absorption coefficient (
a) has calculated using the relation
a
¼ 2:3026ð1=TÞ=t
ð1Þ
FT-IR spectroscopy has used to identify the functional groups of
the synthesized compound and hence to elucidate its molecular
structure [14]. The recorded FTIR spectrum as shown in Fig. 5.
The peak observed at 1701.22 cmꢂ1 is due to the presence of
C@O of the compound. The presence of a methyl group (CH3) has
confirmed by the peak observed at 1390.68 cmꢂ1. The peak ob-
served at 1556.55 cmꢂ1 confirms the presence of secondary amine
NAH vibration. The presence of CAC bond has confirmed by the
where T is the transmittance and t, is the thickness of the crystal.
Optical band gap value has calculated from the transmission spec-
tra, and optical absorption coefficient (
has given by
a
) near the absorption edge
1=2
H
m
a
¼ Aðh
m
ꢂ EgÞ
ð2Þ
peak observed at 962.48 cmꢂ1
.
The peak observed at
where A is a constant, Eg is the optical band gap, h is the Planck’s
constant and the frequency of the incident photons. The band
gap can be calculated by plotting (
1838.16 cmꢂ1 1917.24 cmꢂ1, and 1973.18 cmꢂ1 are due to the
t
1/2
a
ht
)
vs. ht as shown in Fig. 7
and extrapolating the linear portion near the onset of the absorp-
tion edge to the energy axis. From the figure, the value of band
gap value has found to be 2.72 eV. The lower band gap of the title
material makes these compounds interesting for solar cell and pho-
tovoltaic devices [17,18].
TG/DTA studies
Thermogravimetric and Differential thermal analyses give
information regarding phase transition, water of crystallization
and different stages of decomposition of the crystal [19–20]. The
respective TGA/DTA trace for 3A4MPQ crystal has shown in
Fig. 8. TGA curve precisely shows there is no weight loss up to
228.63 °C. The Thermogram spectrum reveals that the significant
Fig. 3. Morphology diagram of 3A4MPQ.

M. Nirosha et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 78–84
81
100
%T
75
50
25
0
-25
4000
3000
2000
1500
1000
500
Fig. 5. FTIR spectrum of 3A4MPQ.
Fig. 8. Photoluminescence spectrum of 3A4MPQ.
Fig. 6. UV–visible absorbance spectrum of 3A4MPQ.
Fig. 9. TG/DTA spectrum of 3A4MPQ.
½
Fig. 7. Plot of h
t
vs. (a
h
t
)
.
DSC trace (Fig. 9) shows a sharp endothermic peak at 156 °C repre-
sents the melting point of the crystal. The sharpness of the peak
indicates the good degree of crystalline perfection of the sample.
weight loss starts at 228.63 °C, and it continues up to 250 °C. The
second stage of weight loss starts at 343.30 °C, and it continues
up to 379.57 °C. This is due to the loss of ionic Clꢂ along with the
methyl group of acetyl function in the molecule. In the DTA spec-
trum, an exothermic peak observed around 156.21 °C corresponds
to the melting temperature of the material. From the results of
thermal analysis, it has established that no transformation and
weight loss observed before 228 °C. Hence the material can be
exploited for any suitable applications up to 228 °C. The resulting
Photoluminescence
The Photoluminescence spectrum provides information of dif-
ferent energy states available between the valence band and con-
duction band responsible for radiative recombination [21]. The PL
intensity is most probably dependent on the crystallinity and

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M. Nirosha et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 78–84
Etching
The microstructure has revealed by a surface treatment using
an appropriate chemical reagent in a procedure termed etching
[24]. Chemical etching is a very simple and elegant technique to re-
veal the crystal defects and the crystal growth mechanism. Etching
technique helps to develop some features such as growth stria-
tions, etch spirals; rectangular etch pits etc., on the crystal surface.
The etching behavior of 3A4MPQ crystal have carried out by using
deionized water as an etchant at room temperature for etching
times of 30 s, 45 s and 60 s. The etch pits have observed at room
temperature for varying times. The specimen surface must first
be ground and polished to a smooth and mirror like finish. This
has accomplished by using successively finer abrasive papers and
powders. Etching studies has performed on as-grown (01-1) face.
Surface layer has removed by means of etching a fresh surface
appeared gave clear etch pits. Fig. 11(a) shows the surface of the
crystal before etching. It is clear from the image that the grown
crystal has a smooth surface. When etched with water for 30 s,
the pits have not observed. Further etching for 45 s produced a
greater number of small sized triangular pits as shown in
Fig. 11(b) When the etched with water for 60 s, the pattern
remains the same, but the size of the etch pits has slightly
increased which as shown in Fig. 11(c). From the etching studies,
it reveals that the observed etch pits are due to layer growth and
hence confirms the two-dimensional nucleation mechanism with
Fig. 10. DSC curve of 3A4MPQ.
structural perfection of the grown crystal. Fig. 10 represents the PL
spectrum of 3A4MPQ single crystal. The sample has excited at
370 nm. The emission spectrum has recorded between 380 and
650 nm. There are two categories of luminescent peaks in the spec-
tra. One category, ranging from 380 to 420 nm, has located in the
range of ultraviolet and violet light. The other consists of blue
luminescence ranging from 450 to 475 nm. The PL emission of
the title material may find their applications in ultraviolet and blue
organic light emitting diodes [22,23].
(a) Without etching
(b) etching 45s
(c) Etching 60s
Fig. 11. (a) Without etching, (b) 45 s etching and (c) 60 s etching.

M. Nirosha et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 78–84
83
fewer dislocations [25]. The calculated etch pit density value has
found to be 1.25 ꢁ 103 cmꢂ2. The generation of dislocations has
strongly correlated with the formation of inclusions in the crystals
[26,27]. These inclusions are due to variation in supersaturation
during the growth, non-uniform growth rates etc., are responsible
for the formation of inclusions.
Micro hardness studies
Hardness is a measure of resistance to plastic deformation. The
hardness of the material plays a significant role in device fabrica-
tion. The Hardness of the crystal carries information about the
crystal structure, yield strength and molecular bindings of the
material. Micro hardness studies have applied to understand with
plasticity of the substance [28]. Experiment has carried out with
Mututoyo MH-112 micro hardness tester using Vickers diamond
pyramidal indenter attached to a metallurgical microscope. Crystal
with flat and smooth faces free from any defects has chosen for the
static indentation tests. The indentations have made at room tem-
perature with a constant indentation time of 10 s. Vickers microh-
ardness test has carried out on (01-1) face of the grown crystal. The
surface has gently polished with water. Then the polished crystal
has correctly mounted on the base of the microscope and indented
gently by applying loads 10–50 g with a dwell time of 10 s. At least
five indentations have made on sample for each load. The indented
surface has examined under the microscope. The lengths of the two
diagonals of the indentations have measured by a calibrated
micrometer attached to the eyepiece of the microscope after
unloading. The average diagonal lengths measured at each time.
The Vickers microhardness number of the crystal Hv has calculated
using the formula.
Fig. 13. Plot of log p vs log d.
P
d2
H
¼ 1:8544
ð3Þ
v
where P is the load applied, and d is the mean diagonal length of the
indentation. Fig. 12 shows the plot between load (P) and (Hv) of
3A4MPQ single crystal. It is evident from the plot that the microh-
ardness value increases with the load shows the reverse indentation
size effect [29]. At higher loads above 50 g measurement has not ta-
ken further since cracks begin to occur. It is due to the release of
internal stresses generated locally by indentation [30]. Hence the
material can be used for the device below the applied load of
50 g. The Meyers index number has calculated from Meyer’s law
[31] which gives the relation between the load and indentation
diagonal length.
Fig. 14. Load vs. stiffness constant.
log p ¼ log k þ n log d
ð5Þ
where k is the material constant and n, is the Meyer’s index. The
plot of log p against log d is a straight line, and it as shown in
Fig. 13. The slope of the graph gives n, and it has found to be 2.41
respectively. Vickers hardness value should increase with the in-
crease of P if n > 2 and decrease in n < 2. The obtained value agrees
well with the experimental values. According to Onitsch [32] and
Hanneman [33], n should lie between 1 and 1.6 for harder materials
and above 1.6 for softer materials. Thus, 3M4APQ crystal belongs to
soft material category.
P ¼ kdn
ð4Þ
The elastic stiffness constant (C11) for different loads calculated
using Wooster’s empirical formula C11 = Hv7/4. It gives an idea
about the tightness of bonding between neighboring atoms [34].
Fig. 14 shows the stiffness constant with load, stiffness constant in-
creases with increasing load.
Conclusions
Single crystals of 3A4MPQ have grown by slow evaporation
solution growth technique. The lattice parameters have found by
single crystal X-ray diffraction technique. The FT-IR spectrum re-
veals the various functional groups present in the grown crystal.
Fig. 12. Plot of Load vs. Hv.

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