Synthesis and mesomorphic behavior of calamitic liquid crystals with a biphenyl moiety

Article abstract of DOI:10.1080/15421406.2013.867228

A new mesogenic homologous series having a biphenyl moiety has been synthesized by condensing 4-hydroxy-4′-nitrobiphenyl- and methoxy-substituted 4-n-alkoxy cinnamoyl chlorides, and their liquid crystalline properties have been studied. All the members of the series are enantiotropic liquid crystals. The methyl to n-pentyl derivatives exhibit both Smectic A (SmA) and Nematic (N) phases; the higher members, starting with the n-hexyl derivative show only a SmA phase. The plot of transition temperatures versus number of carbon atoms in the alkoxy chain exhibits zig-zag pattern for Sm-N and NIsotropic (Iso) transition temperature curves. The average thermal stability is compared with other related homologous series. The introduction of polar nitro group increases significant intermolecular force of attraction which stabilizes the molecular orientation. This results into the increase in the thermal stability of the system.

Full text of DOI:10.1080/15421406.2013.867228

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Synthesis and Mesomorphic Behavior of
Calamitic Liquid Crystals with a Biphenyl
Moiety
R. C. Tandela & Nilesh K. Patela
a Department of Chemistry, The M.S. University of Baroda,
Vadodara, Gujarat 390 002, India
Published online: 27 May 2014.
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To cite this article: R. C. Tandel & Nilesh K. Patel (2014) Synthesis and Mesomorphic Behavior of
Calamitic Liquid Crystals with a Biphenyl Moiety, Molecular Crystals and Liquid Crystals, 593:1,
114-125, DOI: 10.1080/15421406.2013.867228
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Mol. Cryst. Liq. Cryst., Vol. 593: pp. 114–125, 2014
Copyright © Taylor & Francis Group, LLC
ISSN: 1542-1406 print/1563-5287 online
DOI: 10.1080/15421406.2013.867228
Synthesis and Mesomorphic Behavior of Calamitic
Liquid Crystals with a Biphenyl Moiety
R. C. TANDEL∗ AND NILESH K. PATEL
Department of Chemistry, The M.S. University of Baroda, Vadodara, Gujarat
390 002, India
A new mesogenic homologous series having a biphenyl moiety has been synthesized by
condensing 4-hydroxy-4ꢀ-nitrobiphenyl- and methoxy-substituted 4-n-alkoxy cinnamoyl
chlorides, and their liquid crystalline properties have been studied. All the members of
the series are enantiotropic liquid crystals. The methyl to n-pentyl derivatives exhibit
both Smectic A (SmA) and Nematic (N) phases; the higher members, starting with the
n-hexyl derivative show only a SmA phase. The plot of transition temperatures versus
number of carbon atoms in the alkoxy chain exhibits zig-zag pattern for Sm-N and N-
Isotropic (Iso) transition temperature curves. The average thermal stability is compared
with other related homologous series. The introduction of polar nitro group increases
significant intermolecular force of attraction which stabilizes the molecular orientation.
This results into the increase in the thermal stability of the system.
Keywords Biphenyl moiety; calamitic liquid crystals; cinnamates; nematic; smectic
1. Introduction
Liquid crystalline materials have been studied for several decades in electrical, optical, and
life sciences fields not only for scientific interests but also for their practical applications.
Formation of liquid crystalline phases relies on mesogenic groups having either calamitic-
or disc-like shapes. These basic molecular structures can be further modified giving rise to
controlled structural features of the mesophases. The calamitic liquid crystals can form two
main classes of liquid crystal phases, the nematic and smectic phases. The mesomorphic
properties of these materials can largely be influenced by various substituents. This can
influence the melting points, the mesophase types, the dielectric properties, etc.
Linearity, rigidity, and polarizability are also important factors for a molecule to display
liquid crystalline properties [1]. Different aromatic moieties have been used as rigid core
in synthesizing liquid crystals. Biphenyl can be seen as rigid core of many mesogenic
compounds and liquid crystalline [2] or semi-crystalline aromatic polymers [3]. Moreover,
since biphenyl is a molecule interesting and fascinating itself, it has been the object, over
many years, of many studies, both experimental [4–6] and theoretical [7, 8]. Such interest
is mainly due to its relatively simple structure and to the strong conformational dependence
of the molecule on the phase of the material.
Biphenyl derivatives are important in the formation of ferroelectric and anti-
ferroelectric liquid crystals [9–13]. Furthermore, biphenyl derivatives are able to undergo
∗Address correspondence to R. C. Tandel, Department of Chemistry, The M.S. University of
Baroda, Vadodara, GJ 390 002, India. E-mail: tandelcy@yahoo.com
114

Synthesis and Mesomorphic Behavior of Calamitic LCs
115
functionalization reactions, providing access to a variety of compounds [14–25]. Mostly 4,
4ꢀ-substituted biphenyl derivatives exhibit one or more smectic phases and extraordinarily
high clearing temperatures. Kelly et al. reported 4-arylpyridinium salts using different 4, 4ꢀ
substituted biphenyls [26]. Givenchy and co-workers have designed 4, 4ꢀ biphenyl deriva-
tives incorporating a perfluorinated segment and an allylic part as precursors of highly
fluorinated polymers [27]. Hentrich et al. have synthesized symmetrical and asymmetrical
bolaamphiphiles [28] and concluded that bolaamphiphiles are significantly stabilized by
the introduction of a rigid biphenylene unit. Nishiyama and co-workers have investigated
chiral trimeric compounds possessing three biphenyl mesogenic cores connected by flexible
alkyl spacers [29]. They compared the molecular structure and the mesomorphic properties
of these trimers with those of the related dimeric and monomeric systems. Marcelis et al.
[30] have reported liquid crystalline dimers consisting of an aromatic unit and a cholesteryl
mesogenic unit joined via flexible spacers. To the best of our knowledge, liquid crystalline
compounds having a biphenyl moiety with a nitro substituent are very rare. The present
investigation was carried out with a view to study the effect of cinnamoyl linkage and
nitrobiphenyl moiety on the mesomorphic properties of such molecules.
2. Experimental
2.1. Instrumentation
The synthetic route adopted for the series of mesogens is given in the Fig. 1. All synthe-
sized compounds were purified by column chromatography on silica gel (60–120 mesh).
The purity of the samples was checked by thin-layer chromatography. The chemical struc-
tures of the compounds were determined by standard spectroscopic methods. IR spectra
were determined for KBr pellets, using a Perkin Elmer-RX1 spectrophotometer. 1H NMR
spectra was recorded on a Bruker 400 MHz spectrometer using tetramethylsilane (TMS) as
internal reference standard. Liquid crystalline properties were investigated using Leica DM
2500P polarizing optical microscope provided with a Linkam heating stage. The transition
temperatures were confirmed by Differential Scanning Calorimeter on Mettler Toledo –
DSC 822 system which was calibrated using indium as a standard.
2.2. Synthesis and Characterization
2.2.1. Trans-4-n-alkoxy-3-methoxycinnamoyl Chlorides (2). A mixture of 4-hydroxy-3-
methoxycinnamic acid [31,32] (4.85 g, 0.025 mol), alkyl iodide, or bromide (0.03 mol),
potassium hydroxide (3.5 g, 0.062 mol), and ethanol (50 ml) was refluxed for 4 to 5 hr. After
being cooled, the mixture was poured into a stirred mixture of concentrated hydrochloric
acid (25 mL) and ice cold water (50 mL). The product was then filtered off, washed with
water, dried, and recrystallized from ethanol until constant melting points were obtained.
Purity of the compounds are checked by TLC and characterized by spectral data. The
melting points are summarized in Table 1.
n-butoxy derivative: IR (KBr): 2594–2956 cm−1 –O H stretch broad band super-
imposed upon C H stretch, 2880, 2827 cm−1 –C H stretch, 1683 cm−1 >C O stretch,
1260 cm−1 C O stretch, 979 cm−1 strong = C H bending.
1H NMR (CDCl3, δ, ppm): 0.98–1.02 (t, 3H, CH3), 1.49–1.55 (m, 2H, CH2), 1.83–1.88
(m, 2H, CH2), 3.92 (s, 3H, OCH3), 4.06–4.10 (t, 2H, OCH2), 6.31–6.35 (d, 1H, = CH ),

116
R. C. Tandel and N. K. Patel
6.88–6.90 (d, 1H, Ar CH), 7.09–7.10 (d, 1H, Ar CH), 7.12–7.14 (dd, 1H, Ar CH),
7.73–7.77 (d, 1H, CH ).
The acids were converted into their acid chlorides by treating them with thionyl chloride
on water bath till evolution of hydrochloric acid ceased. The excess of thionyl chloride was
distilled off. The crude product was used immediately in the next reaction without further
purification.
MeO
HO
MeO
HO
malonic acid
CH=CH-COOH
CHO
piperidine,
pyridine
1
2
(i) R-Br, KOH, EtOH
(ii) SOCl2, Pyridine
MeO
RO
CH=CH-COCl
benzoyl chloride
pyridine
HO
COO
3
fuming HNO3
acetic acid
COO
NO2
4
5
KOH
EtOH
NO2
HO
(2), pyridine
MeO
RO
CH=CH COO
NO2
Series I
Figure 1. Synthetic route to series I. Note: R = n-CnH2n+1, n = 1 to 8, 10, 12, 14, 16 and 18.

Synthesis and Mesomorphic Behavior of Calamitic LCs
117
Table 1. Melting points (◦C) of trans-4ꢀ-n-alkoxy-3ꢀ-methoxycinnamic acid (5)
Comp. No.
1
1
2
2
3
3
4
4
5
5
6
6
7
7
8
8
9
10 11 12 13
R = -CnH2n+1
10 12 14 16 18
M.p. (◦C)
181 178 163 149 132 125 120 105 103 104 105 107 107
2.2.2. 4-(Benzoyloxy) Biphenyl (3) [33]. 4-Hydroxy biphenyl (0.1 mol) was dissolved in
50 mL of dry pyridine and was added slowly with stirring to cold benzoyl chloride (0.1 mol)
contained in a round bottom flask. The mixture was heated on a water-bath for 30 min and
was allowed to cool up to room temperature. It was acidified with cold 1:1 hydrochloric
acid and precipitates obtained were filtered, washed with water, and dried. The ester was
crystallized from ethanol to yield 87% product. Melting Point: 150◦C.
2.2.3. 4-(Benzoyloxy)-4ꢀ-nitrobiphenyl (4) [33]. 4-(Benzoyloxy) biphenyl (0.145 mol) was
taken in round bottom flask, 310 mL of glacial acetic acid was added in the flask and it
was heated up to 80 to 90◦C. 100 mL fuming nitric acid was added slowly in such a way
that the temperature remained between 80 and 90◦C. After complete addition, the reaction
mixture was cooled to room temperature. The solid separated was filtered and washed with
water and methanol. The product was crystallized from glacial acetic acid to yield 51% of
product. Melting Point: 210◦C.
2.2.4. 4-Hydroxy-4ꢀ-nitrobiphenyl (5) [33]. 4-Benzoyloxy-4ꢀ-nitrobiphenyl (0.18 mol)
was taken in round bottom flask, 300 ml of ethanol was added to it and it was heated
to reflux. An aqueous solution of potassium hydroxide (40 g of KOH in 100 mL of water)
was then added dropwise at reflux. After complete addition, the mixture was further refluxed
for 30 min and cooled overnight. Next day, blue crystals of potassium salt were filtered,
washed with tetrahydrofuran until wash was colorless. Pure 4-hydroxy-4ꢀnitrobiphenyl was
obtained by dissolving the salt in minimum amount of boiling water and adding 1:1 hy-
drochloric acid until acidic pH was obtained. The yellow solid was filtered, washed with
water, dried, and crystallized from ethanol. Melting Point: 203◦C.
2.2.5. 4ꢀ-nitro Biphenyl-4-yl-(2E)-3-(4-butoxy-3-methoxyphenyl)-prop-2-enoate (Series I).
The respective 4-n-alkoxy-3-methoxycinnamoyl chloride (0.01 mol) was dissolved in about
5 mL of dry pyridine. The solution of compound 5 (0.01 mol) in 10 mL of dry pyridine
was added slowly to a cold solution of the above acid chloride. The mixture was heated
on a water bath for about half an hour and was allowed to stand overnight. It was acidified
with cold 1:1 hydrochloric acid. Precipitates were filtered and washed with water followed
by diluted sodium hydroxide solution and water. The residue was purified by column
chromatography on silica gel with mixture of ethyl acetate and petroleum ether (10:90) as
an eluent.
n-butoxy derivative: IR (KBr): 2958, 2872 cm−1 C H stretch, 1697 cm−1 >C O
stretch, 1602 cm−1 olefinic C C-stretch, 1295 cm−1 C O stretch, 1504 cm−1 NO2
asymmetric stretch, 1348 cm−1 NO2 symmetric stretch, 1209 cm−1 C N stretch, 1654,
1414, 1395 cm−1 ring breathing vibrations of C H bending.
1H NMR (CDCl3, δ, ppm): 1.01–1.03 (t, 3H, CH3), 1.52–1.58 (m, 2H, CH2), 1.90–1.98
(m, 2H, CH2), 4.02 (s, 3H, OCH3), 4.13–4.17 (t, 2H, OCH2), 6.33–6.37 (d, 1H, = CH ),
6.69–6.91 (d, 1H, Ar CH), 7.25–7.27 (dd, 1H, Ar CH), 7.34–7.36 (d, 1H, Ar CH),

118
R. C. Tandel and N. K. Patel
Table 2. Phase transition temperatures of series I compounds
Transition temperatures (◦C)
Sr. no.
R = n-alkyl group
Cr
SmA
N
I
1
2
3
4
5
6
7
8
9
10
11
12
13
Methyl
Ethyl
Propyl
Butyl
Pentyl
Hexyl
Heptyl
Octyl
·
·
·
·
·
·
·
·
·
·
·
·
·
169.0
171.0
174.0
185.0
163.9
174.1
185.0
182.2
181.1
181.0
175.9
177.4
171.0
·
·
·
·
·
·
·
·
·
·
·
·
·
187.0
194.5
195.0
211.0
196.5
—
—
—
—
—
·
199.0
210.0
205.0
222.3
210.0
213.2
227.0
229.5
231.0
229.3
221.8
216.0
198.2
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·
·
—
—
—
—
—
—
—
—
Decyl
Dodecyl
Tetradecyl
Hexadecyl
Octadecyl
—
—
—
7.42–7.44 (d, 2H, Ar CH), 7.57–7.61 (d, 1H, CH ), 7.70–7.72 (d, 2H, Ar CH),
7.76–7.78 (d, 2H, Ar CH), 8.33–8.35 (d, 2H, Ar CH).
3. Results and Discussion
The number of homologous series [34, 35] with biphenyl moiety is reported in literature.
Most of these series have terminal a cyano group in the moiety. Low melting mesogenic
cyano biphenyl compounds gave impetus for applications [1]. Gray [34] mentioned that
terminal nitro group normally imparts yellow color hence they did not pursue it further.
However, terminal nitro group has provided some interesting new mesogens. The effect of
Solid-Mesophase
SmA-Nematic
N/SmA-Iso
250
240
230
220
210
200
190
180
170
160
150
4
7
8
10
12
16
14
3
6
2
18
1
5
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18
No. of CarbonAtoms in Alkoxy Chain
Figure 2. Plot of transition temperatures (◦C) versus number of carbon atoms in the alkoxy chain.

Synthesis and Mesomorphic Behavior of Calamitic LCs
119
Table 3. Average thermal stabilities (◦C) of series I, A and B compounds
Series
I
A
B
N/SmA – Iso
(C1-C18)
216.3
180.9
243.0
SmA - N
196.8(C1–C5)
148.1(C7–C14)
195.6(C4–C8)
Commencement
of SmA
C1
C7
C4
mesophase
MeO
RO
CH=CH-COO
CH=CH-COO
NO2
(I)
RO
(A)
(B)
RO
COO
NO2
Figure 3. Comparative geometry of series I, A, and B compounds.
Figure 4. Representative DSC thermograms of n-butyloxy derivative at heating rate of 5◦C min−1
.

120
R. C. Tandel and N. K. Patel
Table 4. Calorimetric data
Peak temps.
R-n-alkyl
group
Transition
state
(microscopic
Sr. No.
1
reading) (◦C)
ꢀH kJ/mole
Butyl
K-SmA
SmA-N
N-Iso
K-SmA
SmA-N
N-Iso
K-SmA
SmA-Iso
K-SmA
SmA-Iso
185.2 (185.0)
211.5 (211.0)
222.7 (222.3)
164.5 (163.9)
197.1 (196.5)
210.0 (210.0)
174.8 (174.1)
212.5 (213.2)
185.7 (185.0)
227.7 (227.0)
10.45
5.12
1.83
10.68
4.71
1.84
19.27
9.07
18.58
7.22
2
Pentyl
3
4
Hexyl
Heptyl
terminal nitro group on the commencement of smectic mesophase is quite interesting. It
was thought quite interesting to synthesize and study the mesogenic properties of biphenyl
derivatives having terminal nitro group.
Thirteen homologues were synthesized by condensing 4-n-alkoxy-3-methoxy cin-
namoyl chlorides with 4-hydroxy-4ꢀ-nitrobiphenyl. All the homologues have enantiotropic
mesophases. The methyl to n-pentyl derivatives exhibit both SmA and N phases; the higher
members, starting with the n-hexyl derivative show only SmA phase. Series I was syn-
thesized by the route shown in Fig. 1. The transition temperatures are summarized in
Table 2. Gray [36] and Major and Baumgartner [37] have suggested that the addition of
each methylene unit simultaneously increase the overall polarizability of the molecules and
Figure 5. Representative DSC thermograms of n-pentyloxy derivative at heating rate of 5◦C min−1
.

Synthesis and Mesomorphic Behavior of Calamitic LCs
121
Figure 6. Representative DSC thermograms of n-hexyloxy derivative at heating rate of 3◦C min−1
.
the lateral intermolecular attraction. The lower homologues are SmA and N, the separation
of aromatic nuclei is at minimum and the terminal cohesions are strongest. As we ascend
the series, only SmA phase commences because as the alkyl chain length increases, the
lateral cohesive forces are also increase and the molecules align themselves in the layer
structure. Hence with increase in the alkyl chain length, the Smectogenic character should
predominate at the expense of nematic mesophase. Therefore in series I, at certain chain
length of alkyl group, nematic mesophase would be observed and system would exhibit
pure SmA phase. At this stage, SmA mesophase will directly pass into isotropic liquid stage
presumably because the terminal intermolecular attractions are inadequate to maintain the
Figure 7. Representative DSC thermograms of n-heptyloxy derivative at heating rate of 5◦C min−1
.

122
R. C. Tandel and N. K. Patel
Figure 8. Polarized optical microphotographs of homologue 05 (a) Smectic A (focal conic texture)
liquid crystalline phase at 189.3◦C on heating; (b) Nematic (thread like texture) liquid crystalline
phase at 204.6◦C on heating.

Synthesis and Mesomorphic Behavior of Calamitic LCs
123
parallel molecular orientation which is required for the normal nematogenic homologous
series.
The plot of transition temperatures versus number of carbon atoms in the alkoxy chain
is given in Fig. 2. The SmA-N and N-Iso transition temperature curves exhibit zig-zag
pattern in a lower derivatives (up to C5) of series. The N-Iso transition temperature curve
raises steeply up to C10 derivative and then fall down up to the last member of the series.
There is a close relationship between liquid crystalline properties and molecular con-
stitution of organic compounds, hence the thermal stability; a measure of liquid crystalline
properties can be correlated with the molecular constitution of the compounds.
The average thermal stabilities of different mesogenic homologous series are compared
and recorded in Table 3.
Comparison of molecular structure of present series I with reported Series:
1. Biphenyl-4-Trans-p-n-Alkoxycinnamates; Series: A [38]
2. 4(4ꢀꢀ-n-Alkoxy benzoyloxy)-4ꢀ-nitrobiphenyls; Series: B [39]
The geometry of these series is given in Fig. 3. The average isotropic thermal stabilities
of series I is higher than those of series A. Series I and series A have the same molecular
geometry except the terminal and lateral substituents. Series I have lateral methoxy and
terminal nitro substituent. Introduction of lateral methoxy is expected to be deterrent
to the thermal stability of the system but the presence of polar nitro group increases
significant intermolecular force of attraction, which stabilizes the molecular orientation. It
also increases the length and polarizability of the molecules. This results into the increase
in the thermal stability of the system [36]. Hence thermal stability of the series I is higher
compare to series A. The difference between the thermal stabilities of series I and A is of
the order of 35◦C. This shows potential effect of a terminal nitro group on the mesomorphic
property of homologous series.
The Nematic thermal stabilities of series I and of series B are almost the same.
They differ only in central linkage and lateral substituent at one end of the molecule.
Methoxy group joined to phenyl ring at ortho position would have steric effect compared
to the molecules of series B. However, the ortho methoxy group would not have fullest
breadth increasing effect. Series B has a biphenyl nucleus and an ester linkage which could
contribute appreciably to the polarizability of the molecule in the direction of molecular axis,
thereby enhancing thermal cohesions. This would give higher nematic–isotropic transition
temperatures than series I.
The mesogens were screened by DSC method and calorimetric data are recorded in
Table 4. Figures 4–7 shows DSC thermograms for n-butoxy to n-heptyloxy derivatives,
respectively. n-Hexyloxy derivative was scanned at the heating rate of 3◦C min−1, rest of
the derivatives were scanned at the heating rate of 5◦C min−1 In the present study, SmA
.
and nematic mesophases are inferred from the textures observed under Leica DM 2500P
polarizing optical microscope provided with a Linkam heating stage (Fig. 8).
4. Conclusions
All the compounds of the series show mesomorphic properties. The methyl to n-pentyl
derivatives exhibit both SmA and N phases; the higher members, starting with the n-hexyl
derivative show only SmA phases. The plot of transition temperatures versus number of
carbon atoms in the alkoxy chain exhibits zig-zag pattern for SmA-N and N-Isotropic
transition temperature curves. Lateral methoxy group is deterrent to mesomorphic proper-
ties while polar nitro group increases significant intermolecular force of attraction, which

124
R. C. Tandel and N. K. Patel
stabilizes the molecular orientation. This results into the increase in the thermal stability of
the system.
Acknowledgments
The authors are grateful to Prof. N.D. Kulkarni, Head, Department of Chemistry, The
M.S. University of Baroda, Vadodara, for taking interest in the work and providing nec-
essary facilities. One of the authors (N.K.P.) is thankful to UGC, New Delhi, for financial
assistance.
References
[1] Collings, P. J. et al (1997). Introduction to Liquid Crystals Chemistry and Physics, Taylor and
Francis: London, UK.
[2] Chen, R. H. (2011). Liquid Crystal Displays: Fundamental Physics and Technology, Wiley:
New Jersey, USA.
[3] Kovacic, P., & Jones, M. B. (1987). Chem. Rev., 87, 357–379.
[4] Bree, A., & Edelson, M. (1977). Chem. Phys. Lett., 46, 500–504.
[5] Barich, D. H., Pugmire, R. J., Grant, D. M., & Iuliucci, R. J. (2001). J. Phys. Chem. A, 105,
6780–6784.
[6] Eaton, V. J., & Steele, D. (1973). J. Chem. Soc. Faraday Trans. II., 69, 1601–1608.
[7] Cacelli, I., & Prampolini, G. (2001). J. Phys. Chem. A, 107, 8665–8670.
[8] Johansson, M. P., & Olsen, J. (2008). J. Chem. Theory Comput., 4, 1460–1471.
[9] Xu, Z.-S., Lemieux, R. P., Natansohn, A., Rochon, P., & Shashidhar, R. (1999). Liq. Cryst., 26,
351–359.
[10] Guillermain, C., & Gallot, B. (2002). Liq. Cryst., 29, 141–153.
[11] Chen, Y., & Wu, W.-J. (1998). Liq. Cryst., 25, 309–318.
[12] Jeon, Y. J., Lee, J. C., & Shivkumar, B. (1999). Liq. Cryst., 26, 1129–1133.
[13] Kumar, P. A., & Pisipati, V. G. K. M. (2001). Mol. Cryst. Liq. Cryst., 365, 147–160.
[14] Sauer, S. et al. (2009). Liq. Cryst., 36, 275–299.
[15] Cheng, Z. et al. (2011). Liq. Cryst., 38, 9–15.
[16] Li, A.-K., Yang, S.-S., Jean, W.-Y., & Hsu, C.-S. (2000). Chem. Mater., 12, 2741–2744.
[17] Bezborodov, V., Lapanik, V., Sasnouski, G., & Haase, W. (2006). Ferroelectrics, 343, 49–58.
[18] Be´nyei, G. Y. et al. Liq. Cryst., 32, 197–205.
[19] Murthy, H. N. S., & Sadashiva, B. K. (2002). Liq. Cryst., 29, 1223–1234.
[20] Reddy, R. A., & Sadashiva, B. K. (2002). Liq. Cryst., 29, 1365–1367.
[21] Kobayashi, K., & Yoshizawa, A. (2007). Liq. Cryst., 34, 1455–1462.
[22] Gilani, A. G., Tajalli, H., & Vahedi, A. (2009). Liq. Cryst., 36, 347–352.
[23] Celebre, G., De Luca, G., & Longeri, M. (2010). Liq. Cryst., 37, 923–933.
[24] Liu, C.-Y., Huang, C.-H., Cheng, P.-S., & Tsai, W.-L. (2012). J. Chin. Chem. Soc., 59, 81–86.
[25] Lemieux, R. P. (2001). Acc. Chem. Res., 34, 845–853.
[26] Kelly, C. J. et al. (2001). J. Heterocyclic. Chem., 38, 11–12.
[27] Taffin de Givenchy, E., Guittard, F., Cailler, L., Munuera, J., & Geribaldi, S. (2005). Mol. Cryst.
Liq. Cryst., 436, 237–246.
[28] Hentrich, F., Tschierske, C., Diele, S., & Sauer, C. (1994). J. Mater. Chem., 4, 1547–1558.
[29] Nishiyama, I., Yamamoto, J., Goodby, J. W., & Yokoyama, H. (2003). J. Mater. Chem., 13,
2429–2435.
[30] Marcelis, A. T. M., Koudijs, A., & Sudho¨lter, E. J. R. (2000). Liq. Cryst., 27, 1515–1523.
[31] Pearl, I. A., & Beyer, D. L. (1951). J. Org. Chem., 16, 216–220.
[32] Robinson, R., & Shinoda, J. (1925). J. Chem. Soc. Trans., 127, 1973–1980.
[33] Ou, S. H. et al. (1993). Macromolecules, 26, 7263–7273.
[34] Gray, G. W. (1975). J. Physique Colloq., 36, C1-337-C1-347.

Synthesis and Mesomorphic Behavior of Calamitic LCs
125
[35] Gray, G. W., Horrison, K. J., & Nash, J. A. (1974). Stable, low melting nematogens of positive
dielectric anisotropy for display devices. In: Ordered Fluids and Liquid Crystals, Porter, R. S.
and Johnson, J. F. (Eds.), Plenum Press: New York, 2, 617–643.
[36] Gray, G. W. (1962). Molecular Structure and the Properties of Liquid Crystals, Academic Press:
London, UK.
[37] Major, W., & Baumgartner, G. (1952). Z. Naturforsch, 7a, 172–175.
[38] Dave, J. S., & Vora, R. A. (1974). Mol. Cryst. Liq. Cryst., 28, 269–273.
[39] Vora, R. A., & Teckchandani, V. R. (1990). Paper presented at the Thirteenth International
Liquid Crystal Conference: Vancouver, Canada, July 22–27.