Calamitic-rod-shaped mesogens based on chalcone esters comprising varying alkoxy and lauryl ester chains: Synthesis, mesomorphism and computational study

Article abstract of DOI:10.1080/15421406.2017.1393167

In this studywe have synthesized a new class of compounds incorporating of chalconyl-ester and terminally substituted lauryl group. A series of new chalcones with three aromatic rings is synthesized and characterised 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 optical polarized light microscopy (POM) and confirmed by differential scanning calorimetry (DSC). It is found that all the prepared materials display enantiotropic LCs phases except first two homologue in present series. The lowermember comp. (C₃ to C₆) display only SmC phase while comp. (C₇ to C₁₂) shows smectic C as well as nematic phase. The higher member comp. (C₁₄ to C₁₈) display only nematic phase in heating and cooling condition. To get more insights, the HOMO, LUMO studies are carried out which supports intramolecular charge transfer interactions in this class of mesogens. (Figure presented.).

Full text of DOI:10.1080/15421406.2017.1393167

Molecular Crystals and Liquid Crystals
ISSN: 1542-1406 (Print) 1563-5287 (Online) Journal homepage: http://www.tandfonline.com/loi/gmcl20
Calamitic-rod-shaped mesogens based on
chalcone esters comprising varying alkoxy and
lauryl ester chains: Synthesis, mesomorphism and
computational study
Vinay S. Sharma, Sunil B. Patel, Anuj S. Sharma & R. B. Patel
To cite this article: Vinay S. Sharma, Sunil B. Patel, Anuj S. Sharma & R. B. Patel (2017)
Calamitic-rod-shaped mesogens based on chalcone esters comprising varying alkoxy and lauryl
ester chains: Synthesis, mesomorphism and computational study, Molecular Crystals and Liquid
Crystals, 656:1, 32-47, DOI: 10.1080/15421406.2017.1393167
To link to this article: https://doi.org/10.1080/15421406.2017.1393167
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Date: 17 December 2017, At: 11:27

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
, VOL. , –
https://doi.org/./..
Calamitic-rod-shaped mesogens based on chalcone esters
comprising varying alkoxy and lauryl ester chains: Synthesis,
mesomorphism and computational study
Vinay S. Sharmaa, Sunil B. Patelb, Anuj S. Sharmab, and R. B. Patela
aChemistry Department, K. K. Shah Jarodwala Maninagar Science College, Gujarat University, Ahmedabad,
Gujarat, India; bDepartment of Chemistry, School of Science, Gujarat University, Ahmedabad, Gujarat, India
ABSTRACT
KEYWORDS
Chalcone; lauryl ester;
mesomorphic; nematic;
smectic
In this study we have synthesized a new class of compounds incorporat-
ing of chalconyl-ester and terminally substituted lauryl group. A series
of new chalcones with three aromatic rings is synthesized and char-
acterised by elemental analyses and spectroscopic techniques such as
Fourier transform infrared [FT-IR] and proton magnetic resonance mag-
netic resonance [1H NMR] spectroscopy. The mesomorphic properties of
these compounds were observed by optical polarized light microscopy
(POM) and confirmed by differential scanning calorimetry (DSC). It is
found that all the prepared materials display enantiotropic LCs phases
except first two homologue in present series. The lower member comp.
(C3 to C6) display only SmC phase while comp. (C7 to C12) shows smec-
tic C as well as nematic phase. The higher member comp. (C14 to C18)
display only nematic phase in heating and cooling condition. To get
more insights, the HOMO, LUMO studies are carried out which supports
intramolecular charge transfer interactions in this class of mesogens.
GRAPHICAL ABSTRACT
1. Introduction
Thermotropic liquid crystals are an important class of self-organized molecular entities which
are in dynamic motion yet possessing long range orientational order [1–2]. Thermotropic LC
CONTACT Vinay S. Sharma
vinaysharma@gmail.com
Science College, Gujarat University, Ahmedabad, Gujarat, , India.
Chemistry Department, K.K. Shah Jarodwala Maninagar
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gmcl.
©  Taylor & Francis Group, LLC

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
33
molecule consists a core, which is usually a linker rod like linked aromatic ring by different
linker unit and tail part which are either straight alkyl or alkoxy chains whose terminal unit is
obviously a polar substituent to providing flexibility to stabilize the molecular alignment. Base
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 covalent strategy [10].
A number of chalcone having reported to exhibit a broad spectrum of anti-bacterial,
antifungal, antiulcer, antimalarial, antitumor, anticancer, anti-inflammatory and antitu-
bercular activity [11, 12]. It is believe that the presence of α, β-unsaturated functional
–
=
–
–
group in chalcone ( CH CH CO ) is responsible for anti-microbial activity, which can
be altered depending upon the type of substituent present on the aromatic rings [13, 14].
–
–
=
–
It has been observed that CO CH CH linkage is less conducive to display mesomor-
phism as compared to CH N , COO , N N linkages group because of the presence
–
= – –
– – =
– =
of non-linearity and angle strain arising from keto ( C O) group [15–19]. Surprisingly,
–
–
=
–
when CO CH CH linkage is linked with another linking group it becomes conductive
to induces thermally stable LCs properties. 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 wide range of temperature. In addition, the nematic phase in
which liquid crystal molecules are oriented on average along to a particular direction [20].
By applying an electric or magnetic field, the orientation of the molecules can be derived
in a probable approach [21]. The chemical constitution of molecules exhibiting mesogenic
property which are of great importance [22]. From the computational methods, detail study
of liquid crystalline compounds with relating to similar or differ structure to exhibits phase
behaviour and other optical properties [23]. In the literature studies, there are several reports
of mesogenic compounds having chalcone linkage group.
Vora et al. [24] reported a homologous series of polymers containing a chalcone linkage.
Soon after words Chudghar and his co-workers reported a homologous series containing on
ester-chalcone linkages [25]. Yeap et al. have also synthesized mesomorphic compounds con-
taining on ester-chalcone linkage [26]. Thaker et al. reported homologous series based on
schiff base and chalconyl linking group [27]. Furthermore, they reported two novel homolo-
gous series contain schiff base and chalcone linkage group [28]. Many mesogenic homologous
series contain one central linkage group were reported [29–31]. Previously, Yellamaggad et al.
reported the bent-core unsymmetrical dimers in which cholesteryl ester and chalconyl moiety
are present, which enhances the biaxiality and chirality of the system [32]. R.Gopalakrishnan
et al. reported chalcone based single crystals, growth, and comparison of two new enone
shifted chalcones and their NLO behaviour [33]. Tandel et al. studied the chain chalconyl
polymers compounds to exhibiting threaded type nematic phases [34]. Doshi et al. reported
chalconyl ester and chalconyl vinyl ester linkage group inbuilt between three phenyl rings and
studied the effect on mesomorphism by substituted groups at terminal and lateral side [35, 36].
Shah et al. studied a nonlinear homologous series based on ester and chalcone linkage group
[37]. Patel et al. reported rod type homologous series having chalconyl ester central linkage
group and hexyloxy tail group [38].Gallardo and his coworkers reported polycatenar liquid
crystals series based on bent shaped chalcone and cyanopyridine molecules [39]. Recently,
Bhoya et al. reported chalconyl-ester linking group based homologous series [40, 41]. Further-
more, S.Kumar et al. reported chalcone based LCs compounds possessing short alkyl chain at
one end and other end with variable chain lengths. These derivatives were reported to exhibit
SmC, SmA and nematic phase [43].

34
V. S. SHARMA ET AL.
Here, in this work, three phenyl rings based thermotropic mesogens with presence of right
terminal lauryl ester tail and left side variable alkoxy group and three linking groups are
synthesized and study by using POM, DSC and PXRD analysis. Furthermore, density func-
tional theory (DFT) based HOMO, LUMO studies are carried out which supports charge
transfer interactions in presently synthesized LCs compounds. Recently, our research group
reported various calamitic and bent type homologous series which consisted two and three
–
=
–
–
–
–
phenyl rings bonded through vinyl ester ( CH CH COO ) or ester ( COO ) and chalcone
–
–
=
–
( CO CH CH ) groups with presence of left variable side group and other part having fixed
terminal substituent group [44–47].
2. Experimental
2.1. Materials
For present synthesized homologous series required materials: 4-hydroxy acetophenone, Lau-
ric acid, 4-hydroxy benzaldehyde, 4-hydoxy benzoic acid were purchased from (S.R.L, Mum-
bai). N, N-dimethyl amino pyridine (DMAP) and Dicyclohexyl carbodiimide (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 spec-
tra were recorded as KBr pellet on Shimadzu in the range of 3800-600 cm−1. Microanalysis
was performed on Perkin-Elmer PE 2400 CHN analyser. The texture images were studied
on a trinocular optical polarising microscope (POM) equipped with a heating plate and dig-
1
ital camera. H NMR was recorded on a 400 MHz in Bruker Advance in the range of 0.5
ppm-16 ppm using CDCl3 solvent. The phase transition temperatures were measured using
Shimadzu DSC-50 at heating and cooling rates of 10°C min−1. Texture image of nematic
phase were determined by miscibility method. Thermodynamic quantities enthalpy (ꢀH)
and entropy (ꢀS = ꢀH/T) are qualitatively discussed. For the POM measurement, the newly
synthesized compound is sandwiched between glass slide and cover slip and heating and cool-
ing rate is (2°C/min) respectively.
2.3. Synthesis of compounds in present series
... Preparation of -formyl phenyl dodecanoate (a)
4-formyl phenyl dodecanoate (1a) has been prepared by esterification of the appropriate lauric
acid (2.0 mmol) and 4-hydroxy benzaldehyde (2.0 mmol), dicyclohexyl carbodiimide (DCC)
(2.22 mmol) and dimethylaminopyridine (DMAP) in catalytic amount (0.2 mmol) in dry
CH2Cl2 (DCM) (30 ml) was stirred at room temperature for 24 h. The white precipitate of
DCU is obtained which was isolated by filtration and remove, while the filtrate was evaporated
to dryness. The resultant crude residue was purified by column chromatography on silica gel
eluting with ethyl acetate: hexane as eluent (3:2) [48].
... Synthesis of (E)--(-(-hydroxy phenyl)--oxoprop--en--yl) phenyl dodecanoate
(a) (chalcone).
Chalcone (2a) was prepared by usual established method reported in literature [49]. (Brown,
Yield: 61%), IR (KBr): vmax/ cm−1 3460 ( OH str.-bonded), 3079-2920 ( C H str. aliphatic
–
– –

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
35
– =
– = –
–
–
alkyl group), 1667 ( C O, group), 1610 ( C C ) aromatic, 1730 ( COO group), 1280
– –
–
( O CH2 ether linkage), 962 (trans, alkene). Elemental analysis: calculated for C27H34O4:
Cal: 76.77; H, 8.05; found: C, 75.98; H, 7.94%.
... Synthesis of Methyl--hydroxy benzoate (a)
Equimolar proportion of p-hydroxy benzoic acid and absolute methanol shacked well in pres-
ence of two drops of concentrated H2SO4 and reaction mixture was refluxed for two to three
hours. Then reaction mixture was dumped into ice, and allowed it to settle down. Solid white
precipitate of methyl-4-hydroxy benzoate is obtained. Product was filtered, washed, dried and
then purified by alcohol. Fine crystals are obtained (M.P.126°C, yield 79%) [50].
... Synthesis of Methyl--n-alkoxy benzoate (b)
Methyl-4-n-alkoxy benzoate(3b) were prepared by alkylation of Methyl-4-hydroxy benzoate
(3b) with alkyl bromide (R-Br) in MeOH (C1 to C8) and EtOH (C10 to C18) and reflux at
3 to 4 hrs. and then dump into ice-cold water to get final Methyl-4-n-alkoxy benzoate (3b)
derivatives [50].
... Synthesis of -n-alkoxy benzoic acid (c)
4-n-alkoxy benzoic acids (3c) were prepared by dissolving comp.3b in ethanol (40 ml) and
10% aq. KOH (2 ml) was added. The resultant mixture was heated at reflux for 6 to 7 hours then
cooled to room temperature, poured into ice cold water (80 ml) and then acidified with dil.
HCl. The crude product obtained −b1y filtration was recrystallized by using MeOH/DCM [51].
–
–
Comp.3C4: IR (KBr): vmax/ cm , 3021 (C H str.), 3301 ( OH of carboxylic group), 1650
1
=
–
(C O str. of carboxylic group), 648 polymethylene group of OC4H9 group. HNMR: 0.88
(t, 3H, OC4H9), 1.44 (sex, 2H, OC4H9), 1.72 (q, 2H, OC4H9), 4.07 (t, 2H, OC4H9), 10.2
(s, 1H, COOH group), 7.11 & 7.92 (d, 4H, first phenyl ring). Elemental analysis: C11H14O3:
–
–
–
–
–
Cal: C, 68.04; H, 7.21%; found: C, 67.69; H, 7.18%.
−1
–
–
Comp.3C8: IR (KBr): vmax/ cm , 3071 (C H str.), 3308 ( OH of carboxylic group),
=
–
–
1680 (C O str. of carboxylic group), 1710 ( COO group), 641 polymethylene group of
1
–
–
OC8H17 group. HNMR: 0.88 (t, 3H, –OC8H17), 1.26-1.30 (m, 8H, OC8H17), 1.44 (sex,
–
–
–
–
2H, OC8H17), 1.72 (q, 2H, OC4H9), 4.07 (t, 2H, OC8H17), 10.8 (s, 1H, COOH group),
7.12 & 7.91 (d, 4H, first phenyl ring). Elemental analysis: C15H22O3: Cal: C, 72.00; H, 8.80%;
found: C, 71.31; H, 7.68%.
... General procedure for the synthesis of final target compounds (C)
The final target compounds (C) has been prepared by esterification of the appropriate com-
pound (3c) (2 mmol) and compound (2a) (2 mmol), dicyclohexyl carbodiimide (DCC) (2.22
mmol) and dimethylaminopyridine (DMAP) in catalytic amount (0.2 mmol) in dry CH2Cl2
(DCM) (30 ml) was stirred at room temperature for 28 h. The slightly yellowish precipitate
of DCU is obtained which was isolated by filtration and remove, while the filtrate was evap-
orated to dryness. The resultant crude residue was purified by column chromatography on
silica gel eluting with ethyl acetate: hexane as eluent (3:2) [48]. The characterization data of
target compounds mention in supporting information. The synthesis route of target com-
pounds was mention in below Scheme 1.
−1
–
– =
–
–
Comp.C1: IR (KBr): vmax/ cm , 3031 (C H str.), 1660 ( C O group), 1740 ( COO
1
– –
–
–
=
–
group), 1280 ( O CH2 ether linkage), 960 (trans CH CH ). HNMR: 0.88 (t, 2H, lau-
ryl chain), 1.26 (m, 12H, lauryl chain), 1.30 to 1.33 (m, 4H, lauryl chain), 2.51 (t, 2H, lauryl
–
–
–
=
–
chain), 3.71 (s, 3H, OCH3), 7.51 (d, 1H, J = 15.1 Hz, CO CH CH ), 8.01 (d, 1H, J = 15.1
–
–
=
–
Hz, CO CH CH ), 6.81 (d, 4H, first phenyl ring), 7.51 (d, 4H, second phenyl ring), 7.61

36
V. S. SHARMA ET AL.
(d, 4H, third phenyl ring). Elemental analysis: C35H40O6: Cal: C, 75.53; H, 7.19%; found: C,
75.12; H, 7.05%.
−1
–
– =
–
–
Comp.C4: IR (KBr): vmax/ cm , 3021 (C H str.), 1640 ( C O group), 1730 ( COO
– –
–
=
–
group), 1280 ( O CH2 ether linkage), 960 (trans –CH CH ), 648 polymethylene group of
1
–
–
OC4H9 group. HNMR: 0.88 (t, 6H, OC4H9 and lauryl chain), 1.26 (m, 12H, lauryl chain),
–
1.30 to 1.33 (m, 4H, lauryl chain), 2.51 (t, 2H, lauryl chain), 4.02 (t, 2H, OC4H9), 1.72 (p,
–
–
–
–
=
–
2H, OC4H9), 1.41 (sex, 2H, OC4H9), 7.51 (d, 1H, J = 15.1 Hz, CO CH CH ), 8.01 (d,
–
–
=
–
1H, J = 15.1 Hz, CO CH CH ), 6.74 (d, 4H, first phenyl ring), 7.53 (d, 4H, second phenyl
ring), 7.61 (d, 4H, third phenyl ring). Elemental analysis: C38H46O6: Cal: C, 76.25; H, 7.69%;
found: C, 76.02; H, 7.48%.
−1
–
=
Comp.C8: IR (KBr): vmax/ cm , 303 (C H str.), 1610 (C O str. of carboxylic group), 1740
( COO group), 1280( O CH2 ether linkage), 960 (trans, CH CH ), 641 polymethylene
–
–
– –
–
–
=
–
1
–
–
group of OC8H17 group. HNMR: 0.88 (t, 6H, OC8H17 and lauryl chain), 1.26-1.30 (m,
–
–
–
–
24H, OC8H17 and lauryl chain), 1.43 (p, 2H, OC8H17), 1.74 (p, 2H, OC8H17), 4.01 (t, 2H,
–
–
=
–
OC8H17), 2.52 (t, 2H, lauryl chain), 7.52 (d, 1H, J = 15.1 Hz, CO CH CH ), 8.01 (d,
–
–
=
–
1H, J = 15.1 Hz, CO CH CH ), 6.71 (d, 4H, first phenyl ring), 7.56 (d, 4H, second phenyl
ring), 7.60 (d, 4H, third phenyl ring). Elemental analysis: C42H54O6: Cal: C, 77.06; H, 8.25%;
found: C, 76.91; H, 8.21%.
... Reaction and scheme
Scheme (ia). DCC/DMAP, DCM,  hr. stirring (rt); (iia) KOH, EtOH,  hr. stirring (rt); (iiia) MeOH, conc.HSO,
 hr. reflux; (iiib) R-Br, KOH, MeOH,  to  hr. reflux; (iiic) KOH, EtOH,  hr. reflux; (iva) DCC/DMAP, DCM,  hr.
stirring (rt).

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
37
3. Result and discussion
3.1. Mesomorphic behaviour study
Here in present investigation, we have synthesized newly liquid crystalline compounds having
three linking unit joint via three phenyl rings from small alkyl chain (C1) to higher alkyl chain
(C18) at left end side chain with fixed lauryl tail group at right terminal side in present series. A
newly ester-chalcone-ester linking group based homologous series synthesised from conden-
sation of 4-n-alkoxy benzoic acid (3c) and (E)-4-(3-(4-hydroxy phenyl)-3-oxoprop-1-en-1-
yl) phenyl dodecanoate (2a) (chalcone) is synthesized and evaluated their LC behaviour. The
thermotropic mesophase behaviour of all newly synthesised compounds was primarily inves-
tigated by polarising optical microscope (POM). The exact temperature of phase transition
and associated enthalpy values were determined by differential scanning calorimetry (DSC)
analysis. The presence of SmC phase is confirmed by XRD technique at transition tempera-
ture. We have totally prepared thirteen compounds in present series from lower member to
higher member, out of thirteen compounds, comp.(C3 to C6) shows only enantiotropic SmC
phase, comp. (C7 to C12) shows enantiotropic smectic C and nematic phase while comp.(C14
to C18) display only nematic phase with wide range of temperature.
... POM study
We have studied the effect of changing variable aliphatic alkoxy side chain on mesogenic
property of liquid crystalline compounds. Here, in present article, we have synthesized three
–
–
phenyl ring based calamitic rod-shaped mesogens having two ester ( COO ) and chalcone
–
=
–
–
( CH CH CO ) group at central part with presence of terminal substituent on both sides.
The transition temperature of present series is listed in Table 1. As seen in Table 1, com-
pounds C1 to C2 shows non liquid crystalline nature, The nonmesomorphicity of comp.C1
to C2 is attributed to their high crystallising tendency which arises due to low magnitudes of
dispersion forces and low dipole-dipole interaction which results into unsuitable magnitudes
of anisotropic forces of intermolecular end to end or lateral attractions as a consequence of
unfavorable combined effects of molecular rigidity and flexibility [52]. While comp. C3 to C6
display only smectic C phase on both heating and cooling condition, comp. C7 to C18 shows
nematic phase. Mesophase formation was found to be dependent on the number, position
Table . Transition temperature in °C by POM.
Transition temperatures in C
Sr.no
R = n-alkyl group
Cr-I
Cr-SmC
SmC-N
SmC/N-I













C
C
C
C
C
C
C
C
C
C
C
C
C
.
.
—
—
—
—
·
—
—
—
—
—
—
—
—
—
—
—
·
—
—
—
—
·
·
·
·
·
·
·
·
·
·
·
·
.
.
.
.
.
.
.
.
—
.
.
.
.
.
.
.
.
.
.
.
·
·
·
·
·
—
·
·
.
.
.
.
.
.
.
·
·
·
·
·
·
·
·
·
·
—
—
—
·
·
—
—
·
·
·
·
– =
(Cr I Crystal to isotropic phase; Cr-SmC = crystal to smectic C phase; SmC-N = smectic C to nematic phase; N-I = nematic to
isotropic phase).

38
V. S. SHARMA ET AL.
Figure . Phase diagram of present series.
and the molecular length of the side alkyl chain which increases the flexibility of molecules
attached to the alkoxy side group (-OR). As shown in Table 1, lower member compounds of
present series shows wide temperature range of mesophase as compare to higher members.
The phase diagram of present series is shown in Figure 1 which indicates the phase
behaviour of Cr-SmC/N, SmC-N and N-I transition curve. It can be seen that, as series
increases from lower homologue (C1) to higher homologue (C18), the transition temperature
gradually is decreases. Cr-SmC/N phase transition curve exhibit a smooth falling tendency
from comp. C1 to C5 and formerly increases at comp.C6, this is due to the presence of odd-
even parity of carbon present in n-alkyl side chain and from comp.C6, it continued to exhibit
descending tendency upto last homologue (C18). Odd-even effect is present at comp. (C5-C6)
and comp. (C6-C7) in Cr-SmC/N transition curve. SmC-N transition curve shows descending
tendency without exhibiting any odd-even effect. N-I transition curve shows falling tendency
upto comp.C7 and then slightly increase at comp.C8 and continued to showing falling ten-
dency upto last homologue. The decreasing tendency in melting and clearing temperature
could be due to the lowering the vander waals interactions between aromatic phenyl cores
and higher degree of flexibility due to presence of long alkyl chain in alkoxy group at left
terminal part and also the presence of lauryl ester at right tail side.
... Textural study
The crystalline compounds placed on 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 image. Microphotographs of the textures observed for compounds C10
and C4 are depicted in Figure 2. Comp.C10 shows broken fan like texture image of smectic C
phase at 143.0°C on cooling condition. Comp. C4 shows needle type texture image of smectic
C phase at 169.0°C on cooling condition. The texture pattern is also being seen in heating
condition. It can be noted that, presence of mesophase in present series is enantiotropical
type.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
39
Figure . Optical photomicrographs on cooling; (a) smectic C (comp.C) at °C; (b) smectic C (comp.C)
at °C.
... Comparative study
Figure 3 indicates the geometrical optimized structure of present series which is calamitic rod
type, consequently, the phenyl rings of the core are connected through ester, chalcone and
ester linking units while lauryl ester and alkoxy chains are positioned at terminal locations.
By varying the length of the left alkoxy chain from C1 to C8, C10, C12, C14, C16, C18, eleven
mesogens are prepared. The presence of polar flexible methylene part in variable alkoxy chain
and also presence of decanoyl ester or lauryl ester at right terminal part increases the polarity
and flexibility of molecule to induce mesomorphism. Presence of middle chalcone group is
become conductive in presence of two ester group to display LCs property. Figure 4 shows
the planar structure of selected two compounds C4 and C14 along with carbon numbers and
the geometry optimized structure from DFT. The overall molecular length of comp.C14 is
higher as compare to comp.C4 while the bond angle at linking group side is similar in both of
the compounds. The dipole moment of comp.C4 is slightly higher as compare to comp.C14.
Comp.C14 shows only nematic phase due to the presence of long side chain in both the sides
to becomes more flexible and absence of lamellar packing arrangement of molecules while in
comp.C4, due to the short alkyl spacer at one end and presence of lamellar packing order in
molecules to induce smectic C phase and on further heating it transform into isotropic state
without displaying any nematic type textural pattern on heating and cooling condition.
... Frontier molecular orbital (FMO) distribution
The calculated frontier molecular orbital (FMO) distributions of comp.C4, comp.C10 and
comp.C18 are presented in Figure 5, 6, 7. The HOMO/LUMO gap in comp.C4 is lower as
Figure . Space-filing diagram and geometrical shape of present series.

40
V. S. SHARMA ET AL.
Figure . Expected molecular configuration with length and bond angle of (a) comp.C; (b) comp.C by
MM method.
Figure . FMO distribution of comp.C.
compare to comp.C10 and comp.C18 due to the presence of short alkyl spacer at one terminal
end. In Figure 5, A close examination of these orbitals reveal that the HOMO is predomi-
nantly localized on the second phenyl and chalcone linking unit while the LUMO is mostly
concentrated on both phenyl benzoate and chalcone unit; lauryl ester and butoxy part in both
terminal side does not have any significant influence on the HOMO and LUMO orbitals. In
Figure . FMO distribution of comp.C.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
41
Figure . FMO distribution of comp.C.
Figure . Temperature range of phase transition in series.
Figure 6, HOMO is localized on the second phenyl and chalcone unit while LUMO is localized
on chalcone unit and third phenyl ring. From the Figure 7, it can be seen that the distribution
of HOMO and LUMO are contrasted as increasing in alkoxy side chain at left tail part. Thus,
it can be concluded that the electronic properties of present synthesized compounds could
have originated from the phenylic-chalcone group rather than other linking unit [53].
... Thermal stability and temperature range
Thermal stability of present novel synthesised 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 compare to other phase transition.
Mesophase commences from C3 homologue in present series. Temperature range of present
Table . Average thermal stability in °C.
Series
Series
SmC-I
SmC-N
Cr-SmC
N-I
. (C-C)
. (C-C)
. (C-C)
. (C-C)
(SmC-I = smectic C to isotropic; SmC-N = smectic C to nematic; Cr-SmC = solid to smectic C;
N-I = nematic to isotropic).

42
V. S. SHARMA ET AL.
Figure . Total minimizes energy of present series.
series is shown in Figure 8. From careful observation of Figure 8, we have noted that the
temperature range of lower member and higher member is higher as compare to middle
member of present series. Comp.C10 and comp.C12 shows good total thermal stability as
compare to other member of present series. We have compared the total minimize energy and
dipole/dipole interactions value for present thirteen compounds in series which is mention
in Figure 9 and Figure 10 respectively. From Figure 9, it can be noted that, as number of
alkyl chain in alkoxy group increase the value of total energy minimize is also increases. As
dipole/dipole interaction is in decreasing order from comp.C1 to C10 except comp.C5, C7 and
higher homologoues of series.
Figure 11 represents the proposed mechanism to indicate the arrangement of lamellar
packing in molecules to shows SmC and on further heating transform into nematic phase.
Figure . Dipole/dipole interaction in present series.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
43
Figure . Propose mechanism of present series.
Figure . DSC thermograms of compound (a) comp.C; (b) comp.C; (c) comp.C; (d) comp.C on heating
and cooling cycles.

44
V. S. SHARMA ET AL.
Figure . DSC thermograms of compound of comp.C on heating and cooling cycles.
In Figure 11, we have compare 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 condition. The molecular length
of comp.C14 is higher as compare to comp.C4 due to the presence of long alkyl chain which
increases the flexibility and polarity of molecule and does not exits any lamellar packing type
arrangement in molecules to exhibit smectic phase.
3.2. 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
of thermograms on several heating and cooling cycles. In Figure 12, comp.C5 exhibits one
significant endothermic peak at 162.81°C in heating cycle, which correspondence to the
presence of crystal to smectic C phase and on cooling condition, it appears at 163.24°C
which reveals with POM result. Comp. C12 shows three endothermic peak at 135.21°C,
154.27°C and 182.36°C on heating cycle corresponding to Cr-SmC, SmC-N and N-I phase
transition, while on cooling cycle, it again appears at 138.02°C and 156.72°C which was
further confirmed by POM analysis which suggest that the mesophase appeared is SmC
Table . Transition temperature (ºC) and enthalpy (J g−) and entropy change (J g−k−) by DSC
measurement.
Comp. Transition Heating scan(ºC) Cooling scan(ºC) ꢀH (Jg−
)
ꢀH (Jg−
)
ꢀS (J g−k−
)
ꢀS (J g−k−
)
C5
C12
C8
C6
C3
Cr-Cr’
Cr’-SmC
SmC-I
Cr-SmC
SmC-N
N-I
Cr-SmC
SmC-N
N-I
Cr-Cr’
Cr’-SmC
SmC-I
Cr-Cr’
Cr’-SmC
SmC-I
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
—
.
.
—
.
.
—
.
.
—
.
.
.
.
.
.
.
.
.
.
—
.
.
—
.
.
—
.
.
.
.
.
—
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
—
.
.
—
.
.
—
.
.
.
.
.
—
.
.
.
.
.
.
.
.
.
—
(Cr-Cr’= solid to solid crystal; Cr’-SmC = solid to SmC; SmC-N = SmC to nematic; N-I = nematic to isotropic).

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
45
and nematic type. Comp. C8 shows two endothermic peaks at 150.92°C and 169.01°C on
heating condition and again reappears at 152.32°C and 175.27°C on cooling condition which
confirm the results obtain by POM study. Comp.C6 exhibits endothermic peaks at 149.88°C,
171.08°C and 185.35°C on heating cycle while on cooling cycle, again these exothermic peaks
traced at 148.18°C and 172.63°C confirm the presence of solid to solid, solid to smectic C
and smectic C to isotropic transition. In Figure 13, Comp.C3 shows endothermic peaks at
161.08°C, 175.95°C and 203.01°C in heating condition while on cooling condition; it appears
at 150.26°C and 176.08°C which reveals with POM result. The phase transition temperatures,
enthalpy and entropy values for the present synthesized series are summarized in Table 3.
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 end with
variable alkyl chain length in alkoxy group (-OR). The liquid crystalline properties of the
synthesized mesogens are carried out by POM and DSC methods which revealed the occur-
rence of enantiotropic nematic as well as addition of smectic 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 right end alkoxy group. Comp. (C3 to C6) shows only enantiotropi-
cal 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 smectic 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 indi-
cated the intermolecular charge transfer interactions and revealed the electronic properties
of present synthesized newly compounds were originated from second and third phenyl to
chalcone moiety.
Acknowledgement
Authors acknowledge thanks to Dr. R. R. Shah, principal and management of K. K. Shah Jarodwala Man-
inagar Science College, Ahmedabad. Authors are also thankful to NFDD Centre for providing analytical
and spectral services.
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