“Effect of the linking unit on the calamitic-shaped liquid crystal: a comparative study of two homologous series of benzoate and cinnamate linked compounds”

Article abstract of DOI:10.1080/15421406.2019.1652009

Two homologous series based on three linking groups have been synthesized and well characterized by elemental analyses and spectroscopic techniques such as Fourier transform infrared [FT-IR] and proton magnetic resonance magnetic resonance [¹H NMR] spectroscopy. The mesomorphic properties of these compounds were observed by using optical polarized microscopy (POM) and confirmed by differential scanning calorimetry (DSC) analysis. In this present investigation, we have synthesized two homologous series viz. (E)-4-(3-(4-(tetra decanoyloxy) phenyl) acryloyl) phenyl-4-n-alkoxy benzoate (Series-1) and 4-((E)-3-(4-(((E)-3-(4-n-alkoxy phenyl) acryloyl) oxy) phenyl)-3-oxo prop-1-en-1-yl) phenyl tetradecanoate (Series-2). Both of the series are differing with respect to the first linking group. All the homologous in following series displays LC properties on heating as well as cooling condition except first four homologous (C₁ to C₄) in series-1 and six homologous (C₁ to C₆) in series-2. To get more insights, the HOMO, LUMO studies are carried out which supports intramolecular charge transfer interactions in this class of mesogens.

Full text of DOI:10.1080/15421406.2019.1652009

Molecular Crystals and Liquid Crystals
ISSN: 1542-1406 (Print) 1563-5287 (Online) Journal homepage: https://www.tandfonline.com/loi/gmcl20
“Effect of the linking unit on the calamitic-
shaped liquid crystal: a comparative study of two
homologous series of benzoate and cinnamate
linked compounds”
Dinesh Kashyap, Sunil Patel, Varsha Prajapat, Vinay Sharma & Dilip Vasava
To cite this article: Dinesh Kashyap, Sunil Patel, Varsha Prajapat, Vinay Sharma & Dilip Vasava
(2019) “Effect of the linking unit on the calamitic-shaped liquid crystal: a comparative study of two
homologous series of benzoate and cinnamate linked compounds”, Molecular Crystals and Liquid
Crystals, 681:1, 58-70, DOI: 10.1080/15421406.2019.1652009
To link to this article: https://doi.org/10.1080/15421406.2019.1652009
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MOLECULAR CRYSTALS AND LIQUID CRYSTALS
2019, VOL. 681, NO. 1, 58–70
https://doi.org/10.1080/15421406.2019.1652009
“Effect of the linking unit on the calamitic-shaped liquid
crystal: a comparative study of two homologous series of
benzoate and cinnamate linked compounds”
Dinesh Kashyapa, Sunil Patela, Varsha Prajapatb, Vinay Sharmab , and
Dilip Vasavaa
aDepartment of Chemistry, School of Science, Gujarat University, Ahmedabad, Gujarat, India;
bDepartment of Chemistry, Faculty of Basic and Applied Science, Madhav University, Sirohi, India
KEYWORDS
ABSTRACT
Liquid crystals; SmC;
chalcone; nematic
Two homologous series based on three linking groups have been
synthesized and well characterized by elemental analyses and spec-
troscopic techniques such as Fourier transform infrared [FT-IR] and
proton magnetic resonance magnetic resonance [1H NMR] spectros-
copy. The mesomorphic properties of these compounds were
observed by using optical polarized microscopy (POM) and confirmed
by differential scanning calorimetry (DSC) analysis. In this present
investigation, we have synthesized two homologous series viz. (E)-4-
(3-(4-(tetra decanoyloxy) phenyl) acryloyl) phenyl-4-n-alkoxy benzoate
(Series-1) and 4-((E)-3-(4-(((E)-3-(4-n-alkoxy phenyl) acryloyl) oxy) phe-
nyl)-3-oxo prop-1-en-1-yl) phenyl tetradecanoate (Series-2). Both of
the series are differing with respect to the first linking group. All the
homologous in following series displays LC properties on heating as
well as cooling condition except first four homologous (C1 to C4) in
series-1 and six homologous (C1 to C6) in series-2. To get more
insights, the HOMO, LUMO studies are carried out which supports
intramolecular charge transfer interactions in this class of mesogens.
CONTACT Vinay Sharma
Science, Madhav University, Sirohi, India; Dilip Vasava
School of Science, Gujarat University, Ahmedabad, Gujarat, India.
vinaysharma3836@gmail.com
Department of Chemistry, Faculty of Basic and Applied
dilipvasava20@gmail.com Department of Chemistry,
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gmcl.
ß 2019 Taylor & Francis Group, LLC

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
59
1. Introduction
Thermotropic liquid crystals are an important class of self-organized molecular entities
which are in dynamic motion yet possessing a long range orientational order [1,2]. A
Thermotropic LC molecule consists a core, which is usually a linker rod like to link
aromatic ring by different linker units and tail part which are either straight alkyl or
alkoxy chains whose terminal unit is obviously a polar substituent to providing flexibil-
ity to stabilize the molecular alignment. Based on the type of the substituents and their
combinations, both nematic and smectic mesophases may be formed [3–5]. Study of
liquid crystalline state is a multidisciplinary subject and useful to mankind and various
industrial applications [6–9] due to its unique property to flow as liquid and optical
properties as crystals. The construction of liquid crystalline molecules is usually carried
out by adopting a covalent strategy [10].
A number of shaken, having reported to exhibit a broad spectrum of anti-bacterial, antifun-
gal, antiulcer, antimalarial, antitumor, anticancer, anti-inflammatory and antitubercular activ-
ity [11,12]. Remarkably, when shaken group is linked to another linking group it becomes
conductive to bring thermally stable mesophase. Liquid crystals in the nematic group are
most widely used in production of liquid crystal displays (LCD) mainly due to their unique
physical properties as well as a wide range of temperature [13]. In the literature studies, there
are several reports of mesogenic compounds having chalcone linkage group [14–19].
Chudghar and his co-workers reported a homologous series containing on ester-chal-
cone linkages [20]. Yeap et al. have also synthesized mesomorphic compounds contain-
ing on ester-chalcone linkage [21]. Thaker et al. reported homologous series based on
schiff base and chalconyl linking group [22]. Many homologous series based on single
chalcone linkage group were reported by Sharma et al. [23–25]. Earlier, Yellamaggad
et al. reported the bent-core unsymmetrical dimers in which cholesteryl ester and chal-
conyl moiety are present, which enhances the biaxiality and chirality of the system [26].
Later, Gallardo and his group reported polycatenar liquid crystals series based on bent
shaped chalcone and cyanopyridine based molecules [27]. Furthermore, S. Kumar et al.
reported chalcone based LCs compounds possessing a short alkyl chain at one end and
other end with varying chain lengths. These derivatives were reported to exhibit SmC,
SmA and nematic phase [28]. Sharma et al. reported various homologous series based
on chalconyl linking group [29–35]. Recently, Goodby et al. reported reviews based on
structure property relationship in low molar mass materials [36].
Thus, the main object of this present work to synthesized and studied the effect of
linking group and variable side chain on mesomorphic properties. Here, we have introduce
some new calamitic liquid crystal based on ester and vinyl ester linked with chalconyl
(-CO-CH ¼ CH-) group. We have compared the thermal stability of mesophase in both
series-1, -2. Furthermore, density functional theory (DFT) based HOMO, LUMO studies are
carried out which supports charge transfer interactions in presently synthesized LCs compounds.
2. Experimental
2.1. Materials
For present synthesized homologous series required materials: 4-hydroxy acetophenone,
Lauric acid, 4-hydroxy benzaldehyde, 4-hydroxy benzoic acid were purchased from

60
D. KASHYAP ET AL.
(S.R.L, Mumbai). N, N-dimethyl amino pyridine (DMAP) and Dicyclohexyl carbodii-
mide (DCC) was purchased from (Fluka Chemie, Switzerland). R-Br was purchased
from (S.R.L. Chemicals, Mumbai). The solvents were dried and purified by standard
method prior to use.
2.2. Measurements
Melting points were taken on Opti-Melt (Automated melting point system). The FT-IR
spectra were recorded as KBr pellet on Shimadzu in the range of 3800-600 cmꢀ1
.
Microanalysis was performed on a Perkin-Elmer PE 2400 CHN analyzer. The texture
images were studied with a Trinocular optical polarizing microscope (POM) equipped
with a heating plate and digital camera. 1H NMR was recorded on a 400 MHz in
Bruker Advance in the range of 0.5 ppm-16 ppm using CDCl3 solvent. The phase transi-
tion temperatures were measured using Shimadzu DSC-50 at heating and cooling rates
of 10 ꢁC minꢀ1. The texture image of nematic phase was determined by miscibility
method. Thermodynamic quantities enthalpy (DH) and entropy (DS ¼ DH/T) are quali-
tatively discussed. For the POM measurement, the newly synthesized compound is
sandwiched between glass slides and cover slip and heating and cooling rate is (2˚C/
min) respectively.
3. Result and discussion
The mesomorphic behavior of the present compounds was analyzed by using a
polarizing optical microscope (POM), differential scanning calorimetry (DSC), and high
temperature X-ray diffraction (XRD).
3.1. Synthesis and characterization
The synthetic route for the preparation of the target molecules is outlined in scheme 1
and scheme 2. The synthesis of 4-formyl phenyl tetradecanoate (1a) is prepared by
Steglich esterification reaction from 4-hydroxy benzaldehyde and tetradecanoic acid
[37]. Comp.3a is prepared by treating of camp. 1a with 4-hydroxy acetophenone in
ethanol [37]. Form FT-IR, the peak of at 1650 cmꢀ1confirm the presence of a ketone
group in chalcone. 4-n-alkoxy benzoic acid (3c) is prepared by reporting method [38].
4-n-alkoxy benzaldehyde (4a) is prepared by condensation of 4-hydroxy benzaldehyde
with various alkyl bromides (R-Br) in the presence of any. K2CO3 and dry acetone [39].
Trans 4-n-alkoxy cinnamic acid is prepared by knoevenagel condensation reaction
reported in literature [40]. The final target compounds of series-1 and series-2 were pre-
pared by modifying method using DCC and DMAP in dichloromethane for 24 hours. to
get the final compounds [36]. The resultant crude residue was purified by using column
chromatography on silica gel eluting with chloroform: methanol as eluent (4:2). FT-IR
results show a peak at 1730 to 1760 cmꢀ1 in the presence of two ester group and
1660 cm-1 for ketone group existence in present series-1 while in series-2, the peaks
arise at 1740 to 1750 cmꢀ1 and 1630 to 1660 cmꢀ1 which confirms the presence of ester

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
61
Scheme 1. (ia) DCC/DMAP, DCM, 48 hr. stirring (rt.); (iia) KOH, EtOH, 24 hr. stirring (rt); (iiia) MeOH,
conc.H2SO4, 1 hr. reflux; (iiib) R-Br, KOH, MeOH, 4 to 5 hr. reflux; (iiic) KOH, EtOH, 2 hr. reflux; (iva)
DCC/DMAP, DCM, 48 hr. stirring (rt); (iva) R-Br, Anhydrous K2CO3, dry acetone, reflux; (ivb) Malonic
acid, piperidine, pyridine, 1 to 2 hr. reflux.
1
group and The H NMR results also well supported to the corresponding structures of
comp.C1-I, C2-l, C6-l, C7-l, C3-ll, C5-ll, C7-ll, C12-ll and C14-ll are mention in ESI.
3.2. Mesomorphic behavior study
Here in the present study, we have synthesized novel liquid crystalline compounds hav-
ing two ester and chalcone as central linking group, joint via three phenyl rings and
variable side chain from small alkyl spacer (C1) to high alkyl spacer (C18) in alkoxy side

62
D. KASHYAP ET AL.
Scheme 2. (1) 3C, DCC/DMAP, DCM, 24 hr. stirring (rt.); (2) 4b, DCC/DMAP, DCM, 12 hr. stirring.
group (-OR) with the unchanged tetradecyl group at the right terminal side through
both of the series. A newly ester-chalcone-ester linking group based homologous series-
1 & series-2 were synthesized from condensation of 4-n-alkoxy benzoic acid (3c) and
Trans 4-n-alkoxy cinnamic acid (4b) with (E)-4-(3-(4-hydroxy phenyl)-3-oxoprop-1-en-
1-yl) phenyl tetradecanoate (2a) (chalcone) is synthesized and studied their mesogenic
properties. The thermotropic mesophase behavior of all newly synthesized compounds
was investigated by using a polarizing optical microscope (POM). The exact tempera-
ture of phase transition and associated enthalpy values were determined by differential
scanning calorimetry (DSC) analysis. The presence of SmC phase is confirmed by high
temperature XRD technique. We have prepared thirteen compounds in each series from
the lower member (C1) to higher member (C18). In series-1, comp. C1-l to C5-l and
comp.C1-ll to C6-ll in series-2 shows the non LCs property, whereas comp.C5-l to C18-l
in series-1 and comp.C7-ll to C18-LL shows enantiotropic nematic phase. Higher num-
bers of both the series show enantiotropic smectic C phase.
3.2.1. POM study
We have studied the effect varying alkoxy group and also the effect of linking group on
mesogenic property of liquid crystalline compounds. In the present study, we have pre-
pared two newly homologous series based on ester-chalcone and vinylester-chalcone
linking group. The transition temperature of present series-1 and series-2 are mentioned
in Table 1. Comp.C1 to C4 in series-1 and comp.C1 to C6 displays non liquid crystalline
properties and directly transform solid state to isotropic state without exhibiting LCs
properties. Higher member compounds in both series exhibited smectic C phase enan-
tiotropic manner while middle members of both the series show enantiotropic nematic
mesophase. Mesophase formation was found to be dependent on the number, position
and the molecular length of the side alkyl chain which alter the flexibility of molecules.
As shown in Table 1, present synthesized chalconyl-ester and chalconyl-vinylester series
shows a wide temperature range of marsupials.
The bar graph of series-1 and series-2 shows the phase behavior of Cr-SmC, Cr/
SmC-N and Cr/N-I transition are listed in Figure 1. It can be seen that, as series

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
63
Table 1. Transition temperature (ꢁC) and enthalpy (kJ molꢀ1) and entropy change (J kꢀ1molꢀ1) by
DSC measurement.
DH
DH
DS
DS
Comp.
Transition
Heating scan(ꢁC)
Cooling scan(ꢁC)
(kJmol-1)
(kJmol-1)
(Jk-1mol-1)
(Jk-1mol-1)
C1-l
C2-l
C3-l
C4-l
C5-l
Cr-I
Cr-I
Cr-I
Cr-I
Cr-N
N-I
Cr-N
N-I
Cr-N
N-I
Cr-N
N-I
Cr-SmC
SmC-N
N-I
Cr-SmC
SmC-N
N-I
Cr-SmC
SmC-N
N-I
Cr-SmC
SmC-N
N-I
Cr-SmC
SmC-N
N-I
Cr-I
Cr-I
Cr-I
Cr-I
Cr-I
Cr-I
Cr-N
N-I
Cr-N
N-I
Cr-N
N-I
Cr-SmC
SmC-N
N-I
Cr-SmC
SmC-N
N-I
Cr-SmC
SmC-N
N-I
161.1
155.4
154.8
153.4
139.5
148.9
137.5
144.6
129.6
143.5
124.3
139.8
108.1
121.3
130.4
102.2
120.2
130.1
95.01
103.8
124.1
93.72
107.4
123.5
79.21
101.7
110.2
193.5
183.5
183.3
173.9
171.4
169.8
151.6
166.9
141.6
162.8
139.5
156.6
124.21
138.92
148.9
115.2
135.1
140.6
110.6
127.4
139.3
105.6
121.8
130.6
159.3
153.8
152.5
149.5
136.9
147.6
135.4
142.5
128.7
142.4
121.5
136.6
110.1
119.9
132.6
106.6
123.7
133.8
91.92
101.3
126.4
91.67
106.8
119.8
80.54
97.02
112.4
189.4
188.6
186.7
177.3
173.7
172.3
154.7
169.4
143.5
165.9
131.4
159.8
122.90
134.52
150.2
117.6
138.7
142.6
108.1
129.3
141.5
109.1
123.6
134.1
7.54
8.65
6.75
5.45
6.75
11.32
5.65
9.86
6.64
12.43
6.75
14.65
5.82
13.24
6.31
4.81
14.95
9.42
3.32
9.54
4.93
6.87
12.75
9.56
1.98
12.83
7.92
6.56
8.65
9.45
8.54
9.65
7.54
2.76
4.65
6.98
9.87
7.86
12.65
5.74
12.01
3.74
8.73
13.04
5.52
10.45
12.83
9.01
7.32
20.21
7.21
3.56
5.35
7.54
6.43
5.78
9.87
3.65
10.43
5.64
9.76
4.64
8.97
1.42
8.54
5.67
3.92
4.63
7.85
5.01
10.83
6.42
3.87
9.45
6.86
4.03
14.94
6.78
5.35
5.87
5.98
6.54
8.75
6.98
5.21
8.64
6.43
8.96
6.54
9.76
9.01
10.56
6.87
7.82
8.43
7.42
8.21
10.45
6.54
4.42
9.75
5.67
0.0173
0.0192
0.0157
0.0127
0.0163
0.0268
0.0137
0.0236
0.0164
0.0298
0.0169
0.0354
0.0151
0.0335
0.0032
0.0128
0.0380
0.0233
0.0090
0.0253
0.0124
0.0187
0.0335
0.0241
0.0056
0.0342
0.0206
0.0140
0.0187
0.0205
0.0188
0.0214
0.0169
0.0064
0.0105
0.0249
0.0225
0.0190
0.0293
0.0144
0.0291
0.0088
0.0224
0.0319
0.0133
0.0272
0.0320
0.0218
0.0193
0.0512
0.0178
0.0082
0.0125
0.0177
0.0152
0.0141
0.0234
0.0089
0.0251
0.0140
0.0234
0.0117
0.0218
0.0037
0.0217
0.0213
0.0103
0.0116
0.0214
0.0137
0.0289
0.0142
0.0106
0.0248
0.0174
0.0113
0.0403
0.0213
0.0115
0.0128
0.0131
0.0146
0.0197
0.0158
0.0121
0.0197
0.0155
0.0206
0.0161
0.0228
0.0227
0.0259
0.0162
0.0200
0.0205
0.0175
0.0215
0.0259
0.0157
0.0115
0.0245
0.0138
C6-l
C7-l
C8-l
C10-l
C12-l
C14-l
C16-l
C18-l
C1-ll
C2-ll
C3-ll
C4-ll
C5-ll
C6-ll
C7-ll
C8-ll
C10-ll
C12-ll
C14-ll
C16-ll
C18-ll
Cr-SmC
SmC-N
N-I
(Cr-SmC ¼ solid crystal to SmC; SmC-N ¼ SmC to nematic; N-I ¼ nematic to isotropic transition)
increases from the lower member (C1) to higher member (C18), the isotropic tempera-
ture gradually decreases. The decreasing tendency in melting and clearing temperature
could be due to the lowering the vander waals interactions between aromatic phenyl
cores and also the flexibility due to the presence of long alkyl chain in alkoxy group at
left terminal part and also the presence of hexadecyl chain inbuilt with the ester group

64
D. KASHYAP ET AL.
Figure 1. Bar graph showing thermal behaviour of series-1 and Series-2.
at the right terminal side group [42]. Higher alkyl chain substituted compounds in both
the series form a lamellar packing type of arrangement of molecules to induce smectic
C mesophase.
3.2.2. Textural study
The crystalline compounds placed on a clear glass slide sheltered by coverslip were
heated to the isotropic state and heating and cooling rate is (2 ꢁC/min) respectively and
observing mesophase texture images. Microphotographs of the textures studied for com-
pounds C6-l, C14-l, C12-l, and C16-l is shown in Figure 2. Comp.C6-l display schlieren
type texture image of nematic phase at 134.0˚C on heating condition. Comp. C14-l
shows broken fan type, texture image of smectic C phase at 118.0˚C on cooling condi-
tion. Comp.C12-l exhibits broken fan type, texture image of smectic C phase at 108˚C
on heating, condition while comp.C16-ll display schlieren type texture image of nematic
phase at 124˚C on heating condition. It can be noted that, presence of mesophase in
present both series are enantiotropic type.
3.2.3. Comparative study
Figure 3 shows the geometrical structure of both the series which is generally calamitic
rod type. Both the series-1 and series-2 having three phenyl rings joint via three
linking groups and unchanged tetradecyl ester group while differ at the first linking
group with respect to each other. The presence of ester linking group favors the
formation of lamellar packing arrangement due to the dipole–dipole interaction
which eventually generated the smectic mesophase [43]. The presence of polar
flexible methylene parts in the variable alkoxy chain (-OR) and also presence of the
tetradecyl ester group at the right terminal part which increases the polarity and
flexibility of molecule to exhibit liquid crystalline property. The space-filling diagram
of both the series suggest the molecular length of series-2 is higher as compared to
series-1 due to the presence of ethylene group in cinemas linkage which is men-
tioned in Figure 4 respectively.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
65
Figure 2. Optical photomicrographs on cooling; (a) nematic (comp.C6-l) at 134˚C; (b) smectic C
(comp.C14-ll) at 118˚C; (C) smectic C (C12-l) at 108˚C; (d) nematic (comp.C16-ll) at 124˚C.
Figure 3. Geometrical shape of series-1 and series-2.
3.2.4. Frontier molecular orbital (FMO) distribution
The calculated frontier molecular orbital (FMO) distributions of comp.C6-l, comp.C3-l,
comp.C6-ll and comp.C3-ll are presented in Figure-S1 to Figure-S4. The energy differ-
ence between the HOMO and LUMO is termed as HOMO-LUMO gap which provide
the knowledge about the molecular length of conjugation and also the band gap level.
The theoretical band gaps for comp.C6-l, C3-l, C6-ll and C3-ll were found to be 5.05 eV,
5.06 eV, 5.03 eV and 5.04 eV respectively. The reactivity and stability of series-2 is higher
as compared to series-1 due to the presence of the small band gap. In series-1, close
examinations of these orbits reveal that the HOMO is predominantly localized on the
second phenyl ring inbuilt with a choking linkage group while the LUMO is mostly
concentrated on chalcone group inbuilt with two phenyl rings. Presence of varying

66
D. KASHYAP ET AL.
Figure 4. Space-filing diagram of (a) comp.C6 (series-1); (b) comp.C6 (series-2).
ꢁ
Table 2. Average thermal stability in C
Series
Series-1
Series-2
Cr-N
131.2 (C5-C8)
109.8 (C10-C18
147.5 (C7-C8)
130.2 (C12-C18
115.0 (C12-C18
SmC-N
Cr-SmC
N-I
)
)
)
98.6 (C10-C18
)
132.3 (C5-C18
)
148.5 (C7-C18)
(Cr-N ¼ solid to nematic; SmC-N ¼ smectic C to nematic; Cr-SmC ¼ solid to smectic C; N-I ¼ nematic to isotropic)
alkoxy side chain (-OR) and hexadecyl ester group in both terminal side shows some sig-
nificant influence on the HOMO and LUMO orbitals. Thus, it can be concluded that the
electronic properties of present synthesized compounds could have originated from the
phenylic-chalcone group in a series-1 and vinyl-ester contain phenolic chalcone in series-2.
3.2.5. Thermal stability and temperature range
Thermal stability of present novel synthesized series is listed in Table 2. From the Table
2, presently series display smectic C and nematic phase with good thermal stability.
SmC-I transition curve shows higher thermal stability as compared to other phase tran-
sition. Mesophase commences from C3 homologue in present both series. Temperature
range of mesophase in series-1 is higher as compare to series-2 respectively.
Figure 5 represents the proposed mechanism to indicate the arrangement of lamellar
packing in molecules to show SmC and on further heating transform into nematic
phase. In Figure 5, we have compared the structural arrangement of comp. C4 and C14
in which comp.C4 shows only smectic C phase while comp.C14 display only nematic
phase. Both of the compounds show mesophase on heating and cooling conditions. The
molecular length of comp.C14 is higher as compared to camp.C4 due to the presence of
long alkyl chain which increases the flexibility and polarity of molecule and does not
exist any lamellar packing type arrangement of molecules to exhibit smectic mesophase.
3.3. DSC analysis
The phase transition temperatures and enthalpies were measured by carrying out DSC
thermal analysis. All compounds are thermally stable as confirmed by the reproducibility

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
67
Figure 5. Propose mechanism of present series-1 and series-2.
of thermograms on several heating and cooling cycles. In Figure 6(a), comp.C10-l exhibits
three endothermic peaks at 108.1˚C, 121.3˚C and 130.4 ˚C on heating cycle, which corre-
sponds to the presence of crystal to smectic C and smectic C to nematic phase transition
while on cooling condition, it appears at 132.6 ˚C, 119.9 ˚C and 110.2 ˚C which was fur-
ther confirmed by POM analysis. Comp. C12-l shows three endothermic peaks at
102.2 ꢁC, 120.2˚C and 130.1 ˚C on heating cycle and on cooling cycle, it again appears at
106.2 ꢁC, 123.7˚C and 133.8˚C. Comp. C8-ll shows two endothermic peaks at 141.6 ˚C
and 162.8 ˚C on heating condition and again reappears at 143.5 ˚C and 165.9 ˚C on cool-
ing condition which confirm the results obtained by POM study. Comp.C14-ll exhibits
two endothermic peaks at 115.9 ꢁC and 135.1˚C on heating cycle and on cooling cycle,
these exothermic peaks traced at 117.62˚C and 138.07˚C to confirm the presence solid to
smectic C and smectic C to nematic phase transition. Comp.C18-ll shows three endother-
mic peaks at 105.6˚C, 121.8˚C and 130.6˚C in heating condition while on cooling condi-
tion; it trace at 109.18˚C, 123.63˚C and 135.01˚C. The phase transition temperatures,
enthalpy and entropy values for the present synthesized series are summarized in above
Table 1.
4. Conclusion
A new calamitic chalconyl ester derived LCs compounds based on three phenyl rings as
rigid core possessing three linking unit having lauryl side group at right end and other

68
D. KASHYAP ET AL.
Figure 6. DSC thermograms of compound (a) comp.C10-l; (b) comp.C12-l; (c) comp.C14-ll; (d)
comp.C18-ll on heating and cooling cycles.
end with a variable alkyl chain length in an alkoxy group (-OR). The liquid crystalline
properties of the synthesized mesogens are carried out by POM and DSC methods
which revealed the occurrence of enantiotropic nematic as well as the addition of smec-
tic C phase in comp. (C7 to C12). The lower member comp. (C1, C2) shows non liquid
crystalline nature due to the presence of short alkyl spacer in the right end alkoxy
group. Comp. (C3 to C6) shows only enantiotropic smectic C phase while comp. (C7 to
C12) shows smectic C and nematic phase with higher value of temperature range and
thermal stability. Comp. (C14 to C18) shows nematic phase without displaying any smec-
tic phase on heating and cooling condition. The group efficiency order derived on the
basis of (a) mesophase thermal stability, (b) early or late commencement of mesophase,
(c) Temperature range of mesophase. The HOMO-LUMO calculations indicated the
intermolecular charge transfer interactions and revealed the electronic properties of pre-
sent synthesized newly compounds were originated from second and third phenyl to
chalcone moiety.
Acknowledgement
Authors acknowledge thanks to Dr. N.K. Shah, Head of Chemistry department, School of
Science, Gujarat University, Ahmedabad for providing lab facility for carrying out this research.
Authors are also thankful to NFDD Centre for providing analytical and spectral services.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
69
ORCID
Vinay Sharma
http://orcid.org/0000-0003-4970-0676
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