Study of Molecular Structure, Mesomorphism and Their Relation with Molecular Rigidity-Flexibility

Article abstract of DOI:10.1080/15421406.2015.1106247

Entirely smectogenic novel chalconyl homologue derivatives of thermotropic liquid crystals (LC) have been synthesized with a view to understanding and establishing the effects of molecular structure on liquid crystal properties and the degree of liquid crystallinity. The homologous series consists of 12 (C₁ to C₁₆) homologues with absence of nematogenic character throughout the present series. The textures of smectic phase are fan shaped or batonnet type of smectic-A or of smectic-C. Phase transition temperatures and thermotropic data were determined by an optical polarizing microscope equipped with a heating stage. The smectic-isotropic (Sm-I) phase transition curve and the Cr-Sm transition curve behave in normal manner in the phase diagram. Analytical and spectral data confirm molecular structures of novel homologues. The average thermal stability for smectic is 139.42°C and the mesogenic phase length ranges from 3.5°C to 79.6°C. Mesogenic properties are compared with the structurally similar known series.

Full text of DOI:10.1080/15421406.2015.1106247

Molecular Crystals and Liquid Crystals
ISSN: 1542-1406 (Print) 1563-5287 (Online) Journal homepage: http://www.tandfonline.com/loi/gmcl20
Study of Molecular Structure, Mesomorphism and
Their Relation with Molecular Rigidity-Flexibility
V.C. Kotadiya, M.D. Khunt & U.C. Bhoya
To cite this article: V.C. Kotadiya, M.D. Khunt & U.C. Bhoya (2016) Study of Molecular Structure,
Mesomorphism and Their Relation with Molecular Rigidity-Flexibility, Molecular Crystals and
Liquid Crystals, 626:1, 45-57, DOI: 10.1080/15421406.2015.1106247
To link to this article: http://dx.doi.org/10.1080/15421406.2015.1106247
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Date: 31 March 2016, At: 14:28

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
, VOL. , –

http://dx.doi.org/./..
Study of Molecular Structure, Mesomorphism and Their
Relation with Molecular Rigidity-Flexibility
V.C. Kotadiya, M.D. Khunt, and U.C. Bhoya
Department of Chemistry, Saurashtra University, Rajkot, Gujarat, India
ABSTRACT
KEYWORD
Entirely smectogenic novel chalconyl homologue derivatives of ther-
motropic liquid crystals (LC) have been synthesized with a view to
understanding and establishing the effects of molecular structure on
liquid crystal properties and the degree of liquid crystallinity. The
homologous series consists of 12 (C to C ) homologues with absence
Liquid crystal; mesogenic;
nematogenic; smectic
1
16
of nematogenic character throughout the present series. The textures
of smectic phase are fan shaped or batonnet type of smectic-A or of
smectic-C. Phase transition temperatures and thermotropic data were
determined by an optical polarizing microscope equipped with a heat-
ing stage. The smectic–isotropic (Sm-I) phase transition curve and the
Cr-Sm transition curve behave in normal manner in the phase dia-
gram. Analytical and spectral data confirm molecular structures of novel
homologues. The average thermal stability for smectic is 139.42°C and
the mesogenic phase length ranges from 3.5°C to 79.6°C. Mesogenic
properties are compared with the structurally similar known series.
Introduction
The liquid crystalline (LC) state of a substance [1] has varying applications in either ther-
motropic LC or lyotropic LC especially for the chalconyl derivatives belonging to homol-
ogous series [2–7]. Therefore, the present investigation is planned to study the chalconyl
novel homologous series of LC substances with a view to understanding and establishing
the relation between LC properties and the molecular structure [8–,11(a)]. The study is
aimed to determine the LC state and the range of liquid crystallinity through an optical
polarizing microscope equipped with a heating stage and the phase behavior will be dis-
cussed and interpreted in terms of molecular rigidity and flexibility [11(b),12–15]. Several
homologous series of LCs have been reported previously [16–21]. The proposed investiga-
tion involves the synthesis of novel molecules, which consisted of three phenyl rings bridged
through -COO- and -CO-CH=CH- groups as well as -OR and -CH flexible terminal end
3
groups.
CONTACT U.C. Bhoya
Gujarat, India.
drucbhoya@sauuni.ernet.in
Department of Chemistry, Saurashtra University, Rajkot-,
©
 Taylor & Francis Group, LLC

4
6
V. C. KOTADIYA ET AL.
Scheme . Synthetic route to the novel series.
Experimental
Synthesis
4
-Hydroxy benzoic acid was alkylated using suitable alkylating agents (R–X) by the modi-
fied method of Dave and Vora [22]. Condensation of 4-methyl benzaldehyde and 4-hydroxy
ꢀ
acetophenon for the synthesis of α-4-hydroxy benzoyl β-4 -methyl phenyl ethylene was
effected by the usual conventional method [23]. A mixture of 4-n-alkoxy benzoic acids, α-
ꢀ
4
-hydroxy benzoyl-β-4 -methyl phenyl ethylene, 1,3-dicyclohexylcarbodiimide (DCC), 4-
ꢀ
dimethylaminopyridine (DMAP) in dichloromethane was used for the synthesis of α-4-(4 -
ꢀꢀ
n-Alkoxy benzoyloxy) benzoyl β-4 -methyl phenyl ethylenes [24]. The synthetic route to
the series is shown in Scheme 1. The final chalconyl derivatives were decomposed, filtered,
washed, dried and crystallized until constant transition temperatures obtained.
The chemicals 4-hydroxy benzoic acid, 4-hydroxy acetophenon, 4-methyl ben-
zaldehyde, alkyl bromide (R-Br), methanol, KOH, 1,3-dicyclohexylcarbodiimide, 4-
dimethylaminopyridine, dichloromethane, ethanol etc. were used as received except solvents,
which were dried, purified and distilled prior to use.
Characterization
The molecular structures were identified using various analytical techniques such as elemen-
1
13
tal analysis. (Table 1), H NMR spectra (Figs. 1 and 2), C NMR spectra (Figs. 3 and 4),
IR spectra (Figs. 5 and 6), and mass spectra (Figs. 7 and 8). Transition temperatures were

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
47
Table . Elemental analysis for () Methoxy () Ethyloxy () Propyloxy derivatives.
Elements%Found
H
Elements%Calculated
H
No. of C atoms
M. F.
C
O
C
O



C H O
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.




C H O
 
C H O

  

Figure . H MNR spectrum of hexyloxy derivative.

Figure . H MNR spectrum of octyloxy derivative.

4
8
V. C. KOTADIYA ET AL.

Figure . C spectrum of octyloxy derivative.
determined using an optical polarizing microscope equipped with a heating stage. Elemen-
tal analysis data obtained from the experimental Perkin Elmer PE 2400 CHN Analyzer-
Waltham, Massachusetts, U.S.A. system and IR data were recorded on SHIMATZU FTIR-
1
8
400 Spectrophotometer- Nishinokyou Kuwabara-cho, Nakagyo- Ku Kyoto, Japan. H NMR

Figure . C spectrum of decyloxy derivative.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
49
Figure . IR spectrum of butyloxy derivative.
spectra were recorded using BRUKER Avance-III (400 MHz) Spectrometer- Billerica, Mas-
sachusetts, U.S.A. using CDCl as a solvent. The molecular ion peak obtained from the exper-
3
imental EI-MS data were recorded by the help of Shimadzu GC-MS Model No. QP-2010,
Nishinokyou Kuwabara-cho, Nakagyo-Ku, Kyoto, Japan. All analytical data were matched
with the synthesized molecule and found to be satisfied. The liquid crystal behavior and the
type of textures were determined by a miscibility method on microscopic observations.
Figure . IR spectrum of heptyloxy derivative.

5
0
V. C. KOTADIYA ET AL.
Figure . Mass spectrum of pentyloxy derivative.
Figure . Mass spectrum of decyloxy derivative.
Analytical data
Spectral data
1
HNMR in ppm for hexayloxy derivative. 0.81–0.83 (t, 3H,-CH of –OC H group), 1.16–
3
6
13
1
1
6
.25 (m, 4H, polymethylene group of –OC H group), 1.37–1.39 (p, 2H, Ar-O-(CH ) -CH ),
6
13
2 2
2
.70–1.74 (p, 2H, Ar-O-(CH )-CH ), 2.29 (3H, s, Ar-CH ), 3.92–3.95 (t, 2H, Ar-O-CH ),
2
2
3
2
.87–6.89 (d, 2H, Ar-H), 7.12–7.16 (d, 2H, Ar-H), 7.24–7.26 (d, 2H, Ar-H), 7.38–7.42 (d, 1H,
chalcone), 7.44–7.47 (d, 2H, Ar-H), 7.70–8.01 (d, 4H, Ar-H). 8.04–8.06 (d, 1H, chalcone).The
NMR data are consistent with the molecular structure.
1
HNMR in ppm for octyloxy derivative. 0.81–0.83 (t, 3H,-CH of –OC H group), 1.22–
3
8
17
1
1
.26 (m, 8H, polymethylene group of –OC H group), 1.36–1.40 (p, 2H, Ar-O-(CH ) -CH ),
8
17
2 2
2
.71–1.78 (p, 2H, Ar-O-(CH )-CH ), 2.32 (3H, s, Ar-CH ), 3.95–3.98 (t, 2H, Ar-O-CH ),
2
2
3
2

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
51
6
.89–6.91 (d, 2H, Ar-H), 7.15–7.17 (d, 2H, Ar-H), 7.26–7.29 (d, 2H, Ar-H), 7.40–7.44 (d, 1H,
chalcone), 7.47–7.49 (d, 2H, Ar-H), 7.72–8.04 (d, 4H, Ar-H). 8.06–8.08 (d, 1H, chalcone). The
NMR data are consistent with the molecular structure.
1
3
CNMR(CDCl ) in ppm for octyloxy derivative. 14.15 (CH ), 21.60 (Ar-CH ) 22.96–31.93
3
3
3
(
(
CH ), 68.39 (OCH ), 121.01 (-CH=CH-C=O) 145.13 (-CH=CH-C=O) 114.40–163.80
2
2
Ar-C), 164.47 (>C=O), 189.46 (>C=O of Chalcone).
1
3
CNMR(CDCl ) in ppm for decyloxy derivative. 14.11 (CH ), 21.58 (Ar-CH ) 22.63–31.78
3
3
3
(
(
CH ), 68.39 (OCH ), 121.03 (-CH=CH-C=O) 145.11 (-CH=CH-C=O) 114.41–163.80
2
2
Ar-C), 164.45 (>C=O), 189.44 (>C=O of Chalcone).
−1
IR in cm (KBr) for butyloxy derivative. 3081 (m,=C-H Str. of Phenyl nucleus), 2939 & 2862
s, C-H aliphatic sym. & asym. str.), 1730 (s, Aromatic C=O Str.), 1654 (C=O Str. of chalcone),
(
1
600 (C=C Str. of vinyl gr. of chalcone & aromatic), 1508 (m, C-C aromatic str.), 1467 (m, C-H
bend alkanes), 1267–1068 (C-O-C Str. of alkoxy), 1163 (C-CO-C Str.) 808 (C-H oop. phenyl
ring), 761 (C-H oop. bending of phenyl ring). The IR data are consistent with the molecular
structure.
IR in cm 1 (KBr) for heptyloxy derivative. 3063 (m,=C-H Str. of Phenyl nucleus), 2916 &
−
2
854 (s, C-H aliphatic sym. & asym. str.), 1728 (s, Aromatic C=O Str.), 1658 (C=O Str. of
chalcone), 1600 (C=C Str. of vinyl gr.of chalcone & aromatic), 1510 (m, C-C aromatic str.),
1
465 (m, C-H bend alkanes), 1278–1070 (C-O-C Str. of alkoxy), 1168 (C-CO-C Str.) 842 (C-
H oop. phenyl ring), 758 (C-H oop. bending of phenyl ring). The IR data are consistent with
the molecular structure.
Where, s=strong, m=medium.
+
Mass spectra of pentyloxy derivative. m/z (rel.int%): 428 (M) , 191 (base peak, ester linkage
break), 121(p-hydroxy benzoic acid).
+
Mass spectra of decyloxy derivative. m/z (rel.int%): 237(M) , 237 (base peak, ester linkage
break), 121(p-hydroxy benzoic acid).
Texture determination by miscibility method
•
•
•
Butyloxy homologue: smectic-C
Octyloxy homologue : smectic-A
Decyloxy homologue: smectic-C
Results and discussion
4
4
-n-Alkoxy benzoic acids are dimeric, whose dimerization disappears by linking then with α-
ꢀ
-hydroxy benzoyl β-4 -methyl phenyl ethylene (m.p. 172–175°C, yield-74–78%). High order
of mesomorphic molecular arrangement stabilizes on linking common chalconyl hydroxyl
derivative with changing components of 4-n-alkoxy benzoic acids. All the members of the
chalconyl derivatives of novel homologous series are enantiotropically smectogenic with
absence of nematogenic property.

5
2
V. C. KOTADIYA ET AL.
Table . Transition temperatures in°C of series-.
Transition temperature in °C
Compound no.
R = n-alkyl group
Sm
N
Isotropic

Methyl
Ethyl
Propyl
Butyl
Pentyl
Hexyl
Heptyl
Octyl
Decyl
.
.
.
.
.
.
.
.
.
–
–
–
–
–
–
–
–
–
–
–
–
.
.
.
.
.
.
.
.
.














Dodecyl
Tetradecyl
Hexadecyloxy
.
.
.
.
.
.
Sm- Smectic: N- Nematic.
Figure . Phase behavior of series.
Transition temperatures (Table 2) are plotted versus the number of carbon atoms present
in n-alkyl chain of left n-alkoxy flexible polar end group to understand the phase behaviors
of series in its phase diagram (Fig. 9a) by drawing smooth transition curves Cr-Sm and Sm-
I, through like or related points. Cr-Sm transition curve adopted zigzag path of rising and
falling values as series is ascended with overall descending tendency. The Sm-I transition
curve exhibited odd-even effect up to the decyloxy(C ) homologue derivative. A Sm-I tran-
10
sition curve for odd members occupy lower position below a Sm-I transition curve for even
numbered homologue derivatives in usual manner. Both transition curves for odd and even
members, initially rises and passes through two maxima at pentyl (C ) and dodecyl (C )
5
12
homologue derivatives. Moreover both curves merge into each other at the decyloxy (C )
10
homologue and then continue as a single transition curve. Thus, Cr-Sm and Sm-I transition
curves behaved in normal manner. Thermal stability for smectic is 139.42°C and the smecto-
genic mesophase length ranges minimum of 3.5°C at the first (C ) homologue to a maximum
1
of 79.6°C at the butyloxy (C ) homologue. Thus, present novel series is smectogenic and mid-
4
dle ordered melting type. The mesogenic property from homologue to homologue varies in
present series, with changing molecular flexibility by -OR end group.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
53
The exhibition of higher ordered smectogenic character by all the members of the present
novel series may be attributed to the linking of chalconyl derivative with n-alkoxy benzoic
acids by esterification process, which increases molecular length, aromaticity, rigidity through
multiple bond of -CH=CH- unit, permanent dipole moment across the longer molecular axis,
dipole-dipole interactions, dispersion forces etc which favors the building of lamellar packing
of molecules in preoccupied rigid crystal lattices forming layered arrangement. The inter lay-
ered attractions are loosened under the influence of exposed thermal vibrations till thermal
frequency exceeds the internal energy (ꢀH) or resistivity towards externally exposed thermal
energy corresponding to attraction between the sides of two layers; the layers of molecules
may start to sides out at Cr-Sm transition temperature and then sliding out of layers continue
up to Sm-I transition temperature in floating condition with appearance of smectic mesophase
of appropriate texture or textures. On continued heating a sample under microscopic obser-
vation from and beyond isotropic temperatures, the molecules are randomly oriented in all
possible directions with high order of disorder or high entropy (ꢀS = ꢀH/T) and without
formation of any less ordered molecular arrangement which can induce nematic phase. On
cooling the isotropic mass, the smectogenic mesophase reversibly reappears at the same tem-
perature at which it had cleared on heating. The exhibition of odd-even effect in Sm-I tran-
sition curve is attributed to even and odd number of carbon atoms present in n-alkyl chain.
The diminishing of odd-even effect in Sm-I transition curve for higher homologues from and
beyond decyloxy (C ) homologue is attributed to the coiling or bending or flexing or cou-
10
pling of n-alkyl chain with the principle axis of a core structure of molecule. The variations in
mesomorphic properties from homologue to homologue in the same present novel series is
due to the changing number of methylene unit or units added progressively in n-alkyl chain
of left terminal end group. Absence of nematogenic character in a series is attributed to the
weaker end to end intermolecular adhesion as a consequence of molecular rigidity and flexi-
bility associated with the enthalpy change (ꢀH) of the substances concerned.
Some mesomorphic properties of present novel series are compared with structurally sim-
ilar other known series-X [25] and Y [26] as shown in Figure 10.
Homologous series-1, X and Y resemble to each other with respect to three phenyl rings,
central bridge -COO- linking first and middle phenyl rings and left n-alkoxy terminal end
group (-OR) for the same homologue from series to series. Homologous series-1 and X resem-
ble to each other with all above resembling features and an added feature is another central
bridge -CO-CH=CH- linking middle and third or a last phenyl rings, but differs with respect
to tail end groups -CH and -Br. Similar homologous series-1 and Y resemble each other with
3
respect to tail end group -CH ; but differs with respect to central bridges -CO-CH=CH- and
3
-
N = N- linking middle and the last phenyl rings. Thus, the combined effect of molecular
rigidity (ꢀH) and flexibility vary from homologue to homologue in the same series and for
the same homologue from series to series. Thus, changing trend in mesomorphic properties
and the degree of mesomorphism depend upon the suitable magnitudes of anisotropic forces
of intermolecular end to end lateral attractions as a consequence of molecular rigidity and
flexibility. The changing trend in average thermal stability, commencement of mesophase,
mesophase lengths etc are recorded in following Table 3 related to series-1, X and Y under
comparison.
Table 3 indicate that,
•
Homologous series-1 and X of chalconyl derivatives are smectogenic without exhibition
of nematic property but azoester series-Y is smectogenic in addition to nematogenic.

5
4
V. C. KOTADIYA ET AL.
Figure . Structurally similar homologous series.
•
Smectogenic mesophase commences from very first (C ) member of the chalconyl ester
1
derivatives of series-1 and X, whereas it commences from decyloxy (C ) homologue of
10
azoester series-Y.
•
•
•
•
•
•
Nematogenic mesophase does not commence till the last (C ) member of a series-1 and
16
X, but it commences from very first member (C ) of a series-Y.
1
Smectic thermal stability of present series-1 is lower than chalconyl ester series-X, but it
is higher than azoester series-Y.
Nematogenic thermal stability is the highest of series-Y among the series under compar-
ative study.
Total mesophase length (Sm+N) range of present series is higher than the series-X and
Y under comparison.
Odd–even effect is observed for the transition curves in the phase diagram for the series
in which mesophase commences from C homologue.
1
The phase diagrams of the series-X and Y chosen for comparative study purpose are
shown in Figure 9b and Figure 9c along with phase diagram of present series-1.
Table . Average thermal stability in°C..
Series →
[]
[X]
[Y]
Smectic — Isotropic
or
Smectic — Nematic
Commencement of smectic phase
Nematic —isotropic
Commencement of nematic phase
.
[C -C ]
C
—
—
.
[C -C ]
C
—
—
.
[C -C ]




 
C
.
[C -C ]


C
Total mesophase length in°C
. to .
C C
. to .
C C
. to .
C C

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
55
The exhibition of smectic property by all the series under comparison and the missing
of nematic phase by series-1 and X can be attributed to the weakening of the forces hold-
ing the planes of layers together in the preoccupied lamellar packing of molecules in their
rigid crystals relative to the intermolecular attractions within a given layer under the influ-
ence of exposed thermal vibrations at solid-mesomorphic transition temperature and the lay-
ers become free to slide and rotate out over one another giving smectic phase fore definite
range of temperature in floating condition. However, on heating the smectic phase to a higher
temperature at which smectic phase ceases to appear the intermolecular end to end attrac-
tive forces of cohesion are weakened for the molecules of series-1 and X to such an extent
that, statistically parallel orientational order of molecular arrangement fails to exhibit, and
nematic mesophase formation does not appear in the microscopic observation under polarize
light and exposed thermal vibrations. However, the homologue molecules of azoester series-Y
resists exposed thermal vibrations with sufficient potentiality and maintains statistically par-
allel orientational molecular order in floating condition beyond another range of temperature
after ceasing of smectic phase appearance at Sm-N transition temperature. Thus, the forma-
tion of nematic phase is missed by series 1 and X but nematic phase formation in addition
to smectic phase appears from C to C homologues of an azoester series-Y. All homologues
1
16
of the three homologous series under comparison, transform into isotropic state, by passing
through only one or two mesomorphic state. The molecules concerned are randomly ori-
ented in all possible directions from and beyond isotropic temperature with high order of
disorder or high entropy (ꢀS = ꢀH/T). The mesophase formation reversibly reappears on
cooling carefully to the isotropic mass of the samples under study at the same phase transi-
tion temperature at which they were appeared for smectic or/and nematic phase formation on
heating. The commencement of smectic phase occurs from very first member of the series-1
and X, but it occurs late from C homologue. Early or late commencement of series depends
10
on the extent of non coplanarity of a molecule. The early commencement of smectic phase
related to less non coplanarity at the molecule. The extent of non coplanarity and the lat-
eral attractions due to the common central bridges -COO- and -CO-CH=CH- central bridge
being almost equal for the same homologue from series-1 to series-X. the observed difference
in thermal stability of 15.37 units is attributed to the polarity and polarizability difference
of -CH and -Br tail end group of series-1 and X respectively but this difference is less effective
3
for the its contribution to the extent of noncoplanarity of the molecules of same homologue
from series-1 to series-X. Therefore, the molecules of series-1 and X are being equicoplaner
their smectogenic character commences equally from very first member of the both series.
But the uncommon central bridges -CO-CH=CH- (series-1 and X) and -N = N- (series-Y),
the -CO-CH=CH- central bridge is longer than -N = N- causes more noncoplanarity due
to the twist obtained as the oxygen atom of the -CO-CH=CH- group bump into the non
bonded adjacent hydrogen atoms of the phenyl ring which causes considerable strain on the
molecule. Consequently the coplanarity of the molecule is reduced to some extent. The central
bridge -N = N- is shorter than -CO-CH=CH- which reduces length to breadth ratio affecting
intermolecular cohesive forces with common tail group -CH of present series-1. Therefore
3
Sm-N thermal stability of series-Y is lowered considerably due to overall decrease in length
and polarizability of the molecule. The difference value in thermal stability for smectic is due
to the -CH=CH- unit. However, the molecular linearity being maintained through -N = N-
unit the commencement of mesophase of less ordered than smectic (i.e. nematic) takes place
from very first member whose nematic thermal stability is much higher than its smectic ther-
mal stability due intermolecular closeness and weaker lamellar packing of molecules in crystal
lattices; which facilitated smectic phase formation late from C homologue of lower thermal
10

5
6
V. C. KOTADIYA ET AL.
stability; as compared to series 1 and X. The mesophase length range is a direct result of the
resistivity towards exposed thermal vibrations which vary from homologue to homologue
in the same series and series to series for the same homologue depending upon favorable
molecular rigidity and flexibility to cause mesophase formation. Thus, variation of smecto-
genic mesophase formation of series-1 and X occurred due to dissimilarity in the flexible tail
groups -CH and -Br whose molecular flexibility differs due to the difference in C-CH and C-
3
3
Br bond polarity and polarizability keeping rest of the rigid molecular part unchanged for the
same homologue. Similarity variations in the mesomorphic behaviors of series-Y from series-
1
and X is attributed to the variation in molecular rigidity due to changing central bridges -N
=
N- and -CO-CH=CH- whose rest of the molecular part including flexible part for the same
homologue remain unaltered.
Conclusions
•
•
(
Novel chalconyl ester derivatives of homologous series is entirely smectogenic with -CH3
and -OR flexible end groups whose mesophase length ranges from 3.5°C to 79.6°C and
it is of middle ordered melting type.
The group efficiency order derived on the basis of (i) thermal stability (ii) early com-
mencement of mesophase and (iii) degree of mesomorphism are as under for smectic
and/or nematic phase.
i) Nematic: -N = N- > -CO-CH=CH- = -CO-CH=CH- (with -CH ) (with -CH (with
3
3)
-Br)
(
1) Smectic: -CO-CH=CH- > -CO-CH=CH- > -N = N- (with -Br) (with -CH (with
3)
-
CH
3)
(ii) Nematic: -N = N- > -CO-CH=CH- = -CO-CH=CH- (with -CH ) (with -CH (with
3
3)
-Br)
(
2) Smectic: -CO-CH=CH- = -CO-CH=CH- > -N = N- (with -CH (with -Br) (with
3)
-
CH )
3
(
iii) Smectic± Nematic: -CO-CH=CH- > -N = N- > -CO-CH=CH- (with -CH ) (with
3
-
CH ) (with -Br)
3
•
•
•
•
•
Molecular rigidity and flexibility operate the suitable magnitudes of anisotropic forces
of intermolecular cohesion and closeness to induce mesomorphic (LC) state.
The phenomenon of mesomorphism is sensitive and susceptible to molecular struc-
ture.
Chalconyl derivatives are biologically active molecules whose bioactivity can be
exploited as antibacterial, antimalerial, anti cancer, anti-inflammatory etc.
Binary systems of chalconyl esters can be studied to construct thermotropic articles or
display devices.
The Sm-I transition curve of an entirely smectogenic series passes through two max-
ima.
Acknowledgments
Authors acknowledge thanks to the Department of Chemistry (DST-FIST Funded & UGC-SAP Spon-
sored), Saurashtra University, Rajkot, for research work. Authors are also thankful to Dr. A.V. Doshi,
Ex. Principal, M.V.M. Science and Home Science College, Rajkot, for his valuable co-operation dur-
ing present investigation as and when needed. Also thanks are due to the National Facility for Drug
Discovery through New Chemical Entities (NCE’s), for analysis of samples.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
57
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