“Synthesis, Mesomorphic and DFT Studies of Chalcone Derived Room Temperature Liquid Crystal with Presence of Lateral Nitro and N, N-Dimethyl Amino Terminal Group”

Article abstract of DOI:10.1080/15421406.2019.1641981

In this present article, we wish to report on the liquid-crystalline properties of chalcone-ester based homologous series of compounds having aliphatic chain length in n-alkoxy group (n = 1 to 10, 12, 14, 16, 18). The present series consisted thirteen compounds, in which comp.C₁ and C₂ shows nonliquid crystalline properties, while comp.C₃ to C₇ display SmC phase and comp.C₈ to C₁₈ exhibits only nematic phase. Textural pattern of presently synthesized compounds are schlieren and threaded type. All this compounds were well characterized by elemental analysis, FT-IR and ¹H NMR. Phase transition temperatures of present synthesised compounds were determined by optical polarising microscopy (POM), differential scanning calorimetric (DSC). Detailed XRD investigation endorses the presence of the nematic phase in higher homologues and SmC phase in lower homologues. It is shown that chalcone with ester as linking unit favors a calamitic liquid crystalline behaviour in molecules. To get more insights, the DFT based HOMO, LUMO studies are carried out which supports intramolecular charge transfer interactions in this class of mesogens. Chalconyl ester based compounds C₃ to C₁₂ shows antibacterial as well as antifungal activity compared with corresponding standard drugs.

Full text of DOI:10.1080/15421406.2019.1641981

Molecular Crystals and Liquid Crystals
ISSN: 1542-1406 (Print) 1563-5287 (Online) Journal homepage: https://www.tandfonline.com/loi/gmcl20
“Synthesis, Mesomorphic and DFT Studies of
Chalcone Derived Room Temperature Liquid
Crystal with Presence of Lateral Nitro and N, N-
Dimethyl Amino Terminal Group”
Devendra K. Shukla, Vinay S. Sharma, Varsha Prajapat & R.B. Patel
To cite this article: Devendra K. Shukla, Vinay S. Sharma, Varsha Prajapat & R.B. Patel (2019)
“Synthesis, Mesomorphic and DFT Studies of Chalcone Derived Room Temperature Liquid Crystal
with Presence of Lateral Nitro and N, N-Dimethyl Amino Terminal Group”, Molecular Crystals and
Liquid Crystals, 682:1, 8-26, DOI: 10.1080/15421406.2019.1641981
To link to this article: https://doi.org/10.1080/15421406.2019.1641981
Published online: 11 Sep 2019.
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MOLECULAR CRYSTALS AND LIQUID CRYSTALS
2019, VOL. 682, NO. 1, 8–26
https://doi.org/10.1080/15421406.2019.1641981
“Synthesis, Mesomorphic and DFT Studies of Chalcone
Derived Room Temperature Liquid Crystal with Presence
of Lateral Nitro and N, N-Dimethyl Amino Terminal Group”
Devendra K. Shuklaa, Vinay S. Sharmab, Varsha Prajapatb, and R.B. Patela
aDepartment of Chemistry, K.K.Shah Jarodwala Maninagar Science College, Gujarat University,
b
Ahmedabad, Gujarat, India; Department of Chemistry, Faculty of Applied and Basic Science, Madhav
University, Sirohi, Rajasthan, India.
KEY WORDS
ABSTRACT
Liquid crystal; nematic;
chalcone; enantiotropic
In this present article, we wish to report on the liquid-crystalline
properties of chalcone-ester based homologous series of compounds
having aliphatic chain length in n-alkoxy group (n ¼ 1 to 10, 12, 14,
16, 18). The present series consisted thirteen compounds, in which
comp.C1 and C2 shows nonliquid crystalline properties, while
comp.C3 to C7 display SmC phase and comp.C8 to C18 exhibits only
nematic phase. Textural pattern of presently synthesized compounds
are schlieren and threaded type. All this compounds were well char-
acterized by elemental analysis, FT-IR and 1H NMR. Phase transition
temperatures of present synthesised compounds were determined
by optical polarising microscopy (POM), differential scanning calori-
metric (DSC). Detailed XRD investigation endorses the presence of
the nematic phase in higher homologues and SmC phase in lower
homologues. It is shown that chalcone with ester as linking unit
favors a calamitic liquid crystalline behaviour in molecules. To get
more insights, the DFT based HOMO, LUMO studies are carried out
which supports intramolecular charge transfer interactions in this
class of mesogens. Chalconyl ester based compounds C3 to C12
shows antibacterial as well as antifungal activity compared with cor-
responding standard drugs.
GRAPHICAL ABSTRACT
CONTACT Vinay S. Sharma
vinaysharma3836@gmail.com, roshanpatel770@gmail.com
ß 2019 Taylor & Francis Group, LLC

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
9
1. Introduction
Study of liquid crystalline (LC) state is a multidisciplinary subject useful to the mankind
and industrial applications through scientist, technologists and technocrats [1–4] due to
its unique property to flow as liquid and optical properties as crystals. Calamitic mole-
cules of conventional and unconventional liquid crystalline compounds have been inten-
sively explored for scientific and technological potential applications such as biologically
active materials, sensing materials and electronic display materials [5–6].
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 [7–10]. It is believe that the presence of a, b-unsaturated functional
group in chalcone (-CH ¼ CH-CO-) is responsible for anti-microbial activity, which can
be altered depending upon the type of substituent present on the aromatic rings
[11–12]. It has been observed that -CO-CH ¼ CH- linkage is less conducive to meso-
morphism as compared to -CH ¼ N-, -COO-, -N ¼ N-, -CH ¼ CH-COO- linkages group
because of non-linearity and angle strain arising from the presence of keto (-C ¼ O)
group in chalcone [13]. Surprisingly, when -CO-CH ¼ CH- linkage is linked with
another linking group it becomes conductive to show LC property.
Previously, Yellamaggad et al. reported the bent-core unsymmetrical dimers in
which cholesteryl ester and chalconyl moiety are present, which enhances the biaxial-
ity and chirality of the system [14]. R.Gopalakrishnan et al. reported chalcone based
single crystals, growth, and comparison of two new enone shifted chalcones and their
NLO behaviour [15]. Tandel et al. studied the chain chalconyl polymers compounds
to exhibiting threaded type nematic phases [16]. Vinyl esters linkage group have been
well known for last decades of years, Vora et al. reported binary mixtures of cinna-
mate esters exhibit a wide range of smectic and nematic mesophase [17]. Doshi et al.
reported various homologous series based on chalconyl and vinyl ester linkage group
and studied the effect on mesomorphism [18–20]. Furthermore, 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 [21]. Recently, Bhoya et al. reported a calamitic rod
type homologous series containing vinyl ester and azomethine linkage groups
[22–23]. Yahya et al. reported a series of azo-ester mesogens containing liquid crys-
talline acrylate having different terminal groups. They reported –OCH3, -OC2H5 and
–OCH3 substituted compounds exhibited greater mesophase stability as compare to
halogen (-F, -Cl, -Br) [24]. Recently, we reported chalconyl ester based homologues
series with different terminal group at tail part that affect the mesomorphic prop-
erty [25–26].
In Present work, we planned to investigate a new chalcone based calamitic homolo-
gous series based on three phenyl rings and also study the effect of lateral nitro (-NO2)
group on LCs property and reactivity with respect to –N(CH3)2 tail at one end and vari-
able alkoxy terminal chain at another end. Comprehensive literature search on chalcone
based room temperature LCs have so far not been reported till the date. Therefore,
these synthesised newly compounds will help in considerate the structure-property rela-
tionship in the developing list of chalcone-based liquid crystalline compounds.

10
D. K. SHUKLA ET AL.
2. Experimental
2.1. 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 Perkin-Elmer PE 2400 CHN analyser. The texture
images were studied on a trinocular optical polarising microscope (POM) equipped
1
with a heating stage. H NMR was recorded on a 400 MHz in Bruker Advance 400 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 minꢀ1. X-
ray diffraction (XRD) measurements were performed on a Rigaku-Ultima IV powder
diffractometer equipped with a Cu ka source (k ¼ 1.5418 A˚ and 1.6 kW, X-ray tube
with applied voltage and current values as 40 kV and 30 mA power) and also Philips
X’PERT MPD. For the POM study, novel synthesized compound is sandwiched between
glass slide and cover slip and heating and cooling rate is (2˚C/min) respectively.
Geometry optimization and energy calculations were performed at the B3LYP/6-311
level in dichloromethane solution using the CPCM solvation method with default con-
vergence criteria.
2.2. Materials
For present synthesized homologous series required materials: 4-hydroxy benzoic acid,
alkyl bromide (R-Br) were purchased from SRL (Mumbai), 4-hydroxy, 3-nitro acetophe-
none, 4-N,N dimethyl amino benzaldehyde were purchased from (Sigma Aldrich), KOH
(Finar Chemicals, India), N,N-dimethyl amino pyridine (DMAP) and
Dicyclohexylcarbodiimide (DCC) were purchased from Fluka Chemie (Switzerland).
The solvents were dried and purified by standard method prior to use
3. Result and discussion
In present article, we have synthesized newly chalcone based calamitic rod shaped hom-
ologous series contain chalcone and ester as central linking group with presence of left
side changing alkoxy (-OR) group varying from methyl (C1) to octadecyl (C18) in pres-
ence of -nitro group on lateral side and N,N-dimethyl amino group at right terminal
side. Here, we have study the effect of polar lateral group with changing alkyl chain
length in terminal chain (-OR) on mesogenic property of liquid crystalline compounds.
A newly chalconyl-ester derived series prepared from condensation of dimeric 4-n-
alkoxy benzoic acids and chalcone (a-4-hydroxy phenyl 3’-nitro benzoyl b-4’’-N, N-
dimethyl amino ethylene) is synthesized and evaluated their thermometric data to com-
pare mesomorphic behaviours and the molecular structure through molecular rigidity
and flexibility. The phase behaviour of all new synthesised compounds has been investi-
gated by polarising optical microscope (POM) and differential scanning calorimetry
(DSC), and X-ray diffraction (XRD).

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
11
3.1. Synthesis and characterisation
In order to study the influences of the different numbers of mesogens on mesomorphic
properties, calamitic-shaped chalconyl ester derivatives were designed as target com-
pounds having nitro group at lateral side with presence of N,N-dimethyl amino ter-
minal group at one end and variable chain at another end. The synthesis of p-n-alkoxy
benzoic acid (C) was carried out by reported method [28]. The (E)-3-(4-(dimethyl
amino) pheny-1-(4-hydroxy-3-nitro phenyl) prop-2-en-1-one (chalcone) (D) was pre-
pared by treating of 4-hydroxy 3-nitro acetophenone and 4-N, N-dimethyl amino ben-
1
zaldehyde in ethanol [29]. The H NMR of comp.D shows doublet of ethylene group
2H (d ¼ 7.54 ppm and d ¼ 8.04 ppm). From FT-IR, the peak found at 1640 cmꢀ1 signi-
fying the presence of -C ¼ O group. The final target compounds of series-1 were pre-
pared by modified method using DCC and DMAP reagent for 24 hr to get the series of
compounds [30]. The resultant crude residue was purified by using column chromatog-
raphy on silica gel eluting with ethyl acetate: hexane as eluent (3:2). FT-IR results shows
peaks at 1730 cmꢀ1 and 1640 cmꢀ1 correspondence to –COO- and –C ¼ O group.
1
While the results obtained from H NMR supported to the corresponding structures of
com. E3, E4, E8 and comp.E14. The synthetic route of series-1 is mentioned in
Scheme 1.
3.2. POM investigation
We have studied comprehensively the effect of linking group, lateral group as well as
changing alkyl chain length in left terminal chain (-OR) to form mesogens having
calamitic rod-shaped. Here, in present investigation, we have synthesized newly chal-
cone (-CO-CH ¼ CH-) and ester (-COO-) linkage group inbuilt between three phenyl
ring and lateral nitro group based homologous series. In present series-1, we have pre-
pared total thirteen compounds from C1 (-OCH3) to C18 (-OC18H37). Comp. C1, C2
shows non-liquid crystalline property while comp. C3 to C5 shows SmC property and
remaining comp.C6 to C18 display only nematic mesophase. The observed data derived
from POM and DSC study complemented to each other. All the synthesized com-
pounds, except comp.C1, C2 exhibited mesogenic property in enantiotropically manner.
Conversely, the type of the mesomorphic property depends upon the number of carbon
atoms present in the aliphatic side chain in alkoxy (-OR) group. Comp.C1, C2 shows
non liquid crystal (NLCs) property, this is due to the presence of short alkyl spacer
methoxy (-OCH3), ethoxy (-O-CH2-CH3) group at left side alkoxy terminal group. The
crystallising tendency of short alkyl spacer compounds (C1, C2) are higher as compare
to other compounds in present series-1 and so it directly transform into isotropic state
when heating from solid state without exhibiting any LC property on heating and cool-
ing condition. The transition temperature of present series is listed below in Table 1.
The plot of transition temperatures versus the number of carbon atoms present in
terminal alkoxy chain showing Cr-SmC, SmC/N-l and N-I phase transition curve shown
in Figure 1. The phase diagram shows descending tendency in all transition curve
increasing from lower member to higher member in present series-1. The transition
curve of Cr-SmC showing decreasing tendency from comp.C3 to C7. The Cr/SmC-I and
N-I transition cure start decreasing as side alkoxy chain increases from comp.C1 to C18.

12
D. K. SHUKLA ET AL.
Scheme 1. Synthetic route of target compounds; (a) MeOH, conc.H2SO4, Reflux; (b) R-Br, KOH, MeOH,
Reflux; (c) KOH, EtOH, Reflux; (d) KOH, EtOH, RT, 12 hr stirring; (e) DCC, DMAP, DCM, RT, 24 hr stirring.
No odd-even effect is seen in all phase transition present in present series-1. It can be
seen that, as the methylene group increases in side alkoxy tail group (-OR), the linearity
and polarizability of the molecules also increase which increases the flexibility of the
molecules to induce mesomorphism at lower temperature. In present series-1, comp.C12
to C18 shows nematic liquid crystalline property at room temperature, this is due to the
presence of chain length (n ¼ 12 to 18) which increases the flexibility of compounds
and as a results LC property were seen at lower temperature or a room temperature.
The presence of lateral polar nitro group in second phenyl ring which normally
decrease the thermal stability of smectic and nematic mesophase, as a result of the

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
13
ꢁ
Table 1. Transition Temperature in C by POM
0
Transition temperatures in C
Sr.no
R ¼ n-alkyl group
Cr
SmC
N
I
1
2
3
4
5
6
7
8
C1
C2
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
–
–
–
–
ꢂ
–
–
–
–
–
–
–
–
–
ꢂ
108.0
102.0
98.0
95.0
93.0
91.0
84.0
76.0
71.0
64.0
61.0
59.0
49.0
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
C3
C4
C5
C6
C7
C8
C10
C12
C14
C16
C18
74.0
68.0
62.0
54.0
43.0
–
–
–
–
–
ꢂ
ꢂ
–
–
–
–
–
–
–
–
–
64.0
53.0
48.0
46.0
41.0
39.0
36.0
31.0
ꢂ
ꢂ
9
ꢂ
10
11
12
13
ꢂ
ꢂ
ꢂ
–
ꢂ
(Cr ¼ solid crystal; Sm ¼ Smectic C phase; N ¼ nematic phase; I ¼ Isotropic phase)
broadening effect that forcing the molecules and increases its polarity and polarizability
[30]. The exhibition of smectic and nematic phase in comp.C6 and C7 is attributed to
the optimum magnitudes of dipole-dipole interactions which control the suitable magni-
tudes of anisotropic forces and intermolecular cohesion and closeness to exhibited
smectic and nematic phase in either reversible or irreversible manner [18]. The
–N(CH3)2 group has significantly influenced the mesogenic properties and its charge
transfer interfaces and broadening of molecule due to presence of -CH3 group in
–N(CH3)2 away from the plane.
In present series-1, the higher homologous display nematic phase with absence of any
lamellar packing to exhibited only nematic property, this is due to the disalignment of
molecules of an angle less than ninety degree under the externally exposed thermal
vibrations of suitable magnitudes which matches with internal energy stored in a mol-
ecule (DH) as related to suitable magnitudes of anisotropic forces of intermolecular end
to end attractions, as a consequence of favorable molecular rigidity and flexibility, which
favorably arranges molecules to float on the surface in statistically parallel orientational
order to maintain molecular two dimensional array [18, 31].
3.2.1. Textural study
The crystalline compounds placed on clear glass slide sheltered by coverslip were heated
to the isotropic state and heating and cooling rate (2 ꢁC/min) respectively and observing
mesophase texture image shown in Figure 2. POM observations reveal that comp.C18
exhibited schlieren type texture with four brush pattern of nematic phase at 32.0 ꢁC on
heating condition. Comp. C4 display focal conic texture image of SmC phase at 68.0 ꢁC
on cooling condition. Compound C8 shows threaded type textural pattern of nematic

14
D. K. SHUKLA ET AL.
Figure 1. Phase diagram of series-1
phase at 48.0˚C on cooling condition which was further confirmed by DSC analysis.
Compound C16 exhibits threaded type textural pattern of nematic phase at 33.0˚˚C on
heating condition. We have measure the phase sequence of compound C8 on cooling
condition as shown in Figure 3 which indicates (a) solid crystal, (b) commencement of
nematic mesophase, (c-e) nematic mesophase at 38.0˚C, 48.0˚C, 49.0˚C, (f) Isotropic
mass appeared at 76.0˚C. Observed phase sequence is repeated again during cooled con-
dition and also confirmed by DSC analysis.
3.2.2. Comparative study
Some LC properties evaluated from thermotropic data of presently investigated newly
series-1 with compared with structurally similar analogues series-2[32] as shown in
Figure 4. Both the series-1 and series-2 are same with respect to two linkage group and
terminally substituted N, N-dimethyl amino group and altering side chain at left ter-
minal part. The linearity of both the series are same however the breadth of series-1 is
higher as compare to series-2 due to presence of -nitro group at lateral side on second
phenyl ring. The temperature range of mesophase in series-1 is lower as compare to ser-
ies-2, this is due to the presence of nitro group which increasing the polarity and polar-
izability of molecules and also the presence of dimethyl amino group which increases
the charge transfer interactions and flexibility caused by altering alkyl side chain in
alkoxy group (-OR). Thus, changing in LC properties like thermal stability and tem-
perature range, commencement of mesophase will be influenced by the magnitudes of
changing features of homologous series-1 and series-2 taken under comparative study.
Figure 5 shows the ball-stick model of series-1 and series-2. It can be seen that, series-1 is
more linear as compare to series-2 and it is differing from lateral side group on second phe-
nyl ring in series-1. Both the series having ester (-COO-) and chalcone (-CO-CH¼ CH-)
linkage group and shows LCs property at lower temperature. However, due to presence of

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
15
Figure 2. Microphotographs of (a) Nematic phase of comp.C18 at 32.0˚C. (b) SmC phase of comp. C4
at 68.0˚C. (c) Nematic phase of comp. C8 at 48.0˚C. (d) Nematic phase of comp. C16 at 33.0˚C.
nitro group in series-1 which effect on the thermal stability of mesophase and as a results
mesophase appeared at lower temperature with poor thermal stability.
From the above Table 2, it indicates that presently investigated series-1 and series-X
which was chosen for comparison are nematogenic in addition of smectogenic. Thermal
stability of nematic phase in newly series-2 is higher as compare to series-1. However,
the thermal stability of smectic phase in series-1 is higher as compare to series-2. Both
the series shows mesomorphism in enantiotropical manner. The thermal stability of Cr-
SmC and SmC-I phase transition in series-1 is higher as compare to series-2, while the
SmC-N, Cr-N and N-I phase transition of series-1 is lower as compare to series-2.
These observations are further established by using DSC analysis where phase transition
associated with Cr-N, N-I in higher members, Cr-SmC, SmC-N, N-I in middle mem-
bers while Cr-SmC, SmC-I in lower member of present series-1. Figure 6 represents the
proposed mechanism to represents the arrangement of molecules to induce SmC phase
in lower member (C3 to C7) and nematic mesophase in higher member (comp.C6 to
C18) of present series-1. From Figure 6, It can be seen that the molecular length of
higher member alkyl chain contain compounds is higher as compared to short alkyl

16
D. K. SHUKLA ET AL.
Figure 3. Phase sequence of comp.C14 (heating cycle).
Figure 4. Structurally similar analogous series
spacer chain based compounds. Thus, due to the presence of higher alkyl chain in
alkoxy terminal part increasing more flexibility to passing solid phase to nematic phase
without exhibiting any smectic phase. Comp. C1 and C2 shows nonliquid crystalline
property due to the presence of short alkyl spacer present in n-alkoxy terminal part.
3.3. Chemical reactivity
The nature of the electronic transition and frontier molecular orbital (FMO) distribu-
tions are investigated by using density functional theory (DFT) at the B3LYP/6-311
level in Dichloromethane solution using the CPCM solvation model with default con-
vergence criteria. The calculated FMO distributions of comp.C8 (series-1) compared
with comp.C8 (series-2) are presented in Figure 7 and Figure 8. It is shown that from
Figure 7 that for comp.C8 from series-1 and series-2, both HOMO and LUMO are

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
17
Figure 5. Ball-stick model of series-1, -2.
ꢁ
Table 2. Average thermal stability in C
Series
Series-1
Series-2
SmC-I
SmC-N
Cr-N
Cr-SmC
N-I
95.33
58.56
68.03
60.02
69.37
81.66
59.64
82.01
52.85
76.66
localized on the chalconyl-phenyl unit having N,N-dimethyl amino terminal group.
A close examination of these orbitals reveals that the HOMO of comp.C4 from both
series is predominantly localized on the second phenyl with chalconyl-phenyl unit
while the LUMO is mostly concentrated on chalconyl-phenyl unit. Presence of
N,N-dimethyl amino group at terminal side shows significant influence on the
HOMO and LUMO orbitals. It can be noted that the electronic properties of
comp.C8 (series-1, series-2) could have originated from the chalconyl-phenyl unit
substituted by N,N-dimethyl amino group at tail side. The energy difference
between the HOMO and LUMO is termed as HOMO-LUMO gap. The HOMO-
LUMO gap of comp.C8 from both series is shown in Table 3. As careful observation
of Table 3, the HOMO-LUMO gap of comp.C8 (series-2) is 4.342 eV which is lower
as compare to comp.C8 (series-1). The presence of nitro group at lateral side effects
the possibility of charge transfer of electron in the HOMO to the LUMO. The
higher value of HOMO energy contributes negatively to the activity due to presence
of N, N-dimethyl amino group as electron-donating group which increase the
energy of the HOMO orbitals.
Figure 9 shows the planar structure along with carbon numbers and the geometry
of present comp.C8-I and comp.C8-II were optimized using density functional theory
(DFT) based method with Becker’s three-parameter functional and the Lee-Yang-Parr

18
D. K. SHUKLA ET AL.
Figure 6. Proposed mechanism of present series-1.
Figure 7. The molecular orbitals and energy for the HOMO and LUMO of comp.C8 (series-1).
functional (B3LYP) with 6-311 basis set [33]. The magnitude of dipole moment
(4.77 D) of comp.C8-I is higher as compare to comp.C8-II due to presence of polar
nitro group on lateral side is shown for geometry optimized structure. Further, the

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
19
Figure 8. The molecular orbitals and energy for the HOMO and LUMO of comp.C8 (series-2).
overall length of the molecule (L) is found to be 28.275 Å (C8-I) and 24.085 Å
(C8-II).
3.4. DSC analysis
DSC is a valuable method for the detection of phase transitions. The thermal behaviour
of newly synthesized compounds was confirmed by using DSC measurement shown in
Figure 10. In present study, DSC thermogram is traces in heating and cooling condi-
tion. An examination of crystal to mesophase transition temperatures reveal that with
increasing alkyl chain length in left tail group, a decrease in transition temperatures. As
a result, mesophase temperature range for compounds found lower and some of
remaining compounds shows good mesophase range due to the presence of right ter-
minal unaltered –N(CH3)2 group. Comp.C18 shows endothermic peak at 35.68 ꢁC on
heating trace, which indicates the presence of crystal to SmC mesophase while on cool-
ing condition, it trace at 36.02˚C which reveal the presence of mesophase in enantio-
tropical manner. Comp.C8 shows significant endothermic peaks at 49.27 ꢁC on heating
condition, which is nearly to the transition temperature observed by POM study while
on cooling condition, it appeared at 50.62˚C indicate the presence of Cr-N phase transi-
tion. Compound C6 shows first endothermic peaks at 49.81˚C for crystal to crystal
phase and second endothermic peak appear at 72.09˚C on heating condition and on
cooling condition, it trace at 49.98˚C and 73.12˚C to confirm the presence of crystal to
nematic phase which was further confirmed by POM analysis. For compound C3, the
first endothermic peak trace at 35.68˚C which shows the presence crystal to crystal
phase and on further heating second endothermic peak trace at 72.68˚C indicate crystal
to smectic phase on heating condition while in cooling condition, endothermic peak

20
D. K. SHUKLA ET AL.
Table 3. HOMO-LUMO energy value of comp.C8 (series-1, series-2).
Comp.
HOMO
LUMO
Energy gap
C8-I (series-1)
C8-II (series-2)
ꢀ9.479 eV
ꢀ9.475 eV
ꢀ5.334 eV
ꢀ5.133 eV
4.145 eV
4.342 eV
Figure 9. Energy optimized space filled model showing magnitude and direction of dipole moment.
trace at 80.02˚C which specifies the presence of smectic mesophase and at 40.07˚C
smectic phase transform into crystal Transition temperature obtained by DSC analysis
at heating condition and the value of enthalpy and entropy are listed in Table 4.
3.5. XRD study
The mesophase structures of novel chalconyl-ester LCs were further confirmed by X-ray
diffraction (XRD) studies of comp.C5 and comp.C12 filled in Lindemann capillaries. The
XRD pattern obtained for comp.C5 and comp.C12 at 62.0˚C and 41.0˚C corresponding
to smectic C and nematic phase are shown in Figure 11 and Figure 12. The sharp
reflection in the small angle region with d-spacing 14.924 Å of comp.C5 which is
slightly smaller than the molecular length 15.026 Å indicating the tilted organization of

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
21
Figure 10. DSC thermogram of (a) comp.C18; (b) comp.C8; (c) comp.C6; (d) comp.C3 on heat-
ing condition.
the molecules in the layers. The presence of sharp reflection in the small angle region is
characteristic of layer ordering of smectic phase. No any diffuse peak is present at wide
angle region. In comp.C12, no any significant peak is present at lower angle region while
the broad hump at higher angle region indicates the absence of in plane order and
liquid like nature of molecules in the layer.
3.6. Biological Evaluation
In the present work, the focus has been drawn on designing new structural entities of
chalcones inbuilt with 4-n-alkoxy benzoic acid to form chalconyl-vinyl ester scaffolds to
evaluate the prospective effect on biological activity, particular antibacterial and antifun-
gal activity. Newly synthesized bent core compounds based on chalconyl-vinyl ester
were examined for antimicrobial activity against four pathogenic micro-organism viz.
E.coli, P.aeruginosa (Gram –ve) and S.aureus, S.pyogenus (Gram þ ve) bacterial strains.
The antifungal activities were carried out with C.albicans, A.niger and A.clavatus at vari-
ous concentrations. The synthesized compounds showed good activity results against
E.coli, P.aeruginosa (Gram–ve) and S.aureus, S.pyogenus (Gram þ ve). The ampicillin,
gentamycin, chloramphenicol, ciprofloxacin, nystatin and greseofulvin were used as the
standard drug for gram-positive, gram-negative and fungal strains, respectively. The
minimum inhibitory concentration (MIC) was evaluated by the broth dilution method.

22
D. K. SHUKLA ET AL.
Table 4. Transition temperature (ꢁC) and enthalpy (J gꢀ1) and entropy change (J gꢀ1kꢀ1) by DSC
measurement.
Comp.
Transition
Heating scan(ꢁC)
Cooling scan(ꢁC)
DH (-Jg-1)
DH (Jg-1)
DS (-J g-1k-1)
DS (J g-1k-1)
C18
Cr-N
N-I
Cr-N
N-I
Cr-Cr’
Cr’-N
N-I
Cr-Cr’
Cr’-SmC
SmC-I
Cr-SmC
SmC-I
35.68
>50.0
49.27
>80.0
49.81
72.09
>100.0
35.68
40.07
>100.0
60.72
36.02
–
50.62
–
49.98
73.12
–
72.68
80.02
–
1.82
6.94
2.32
12.81
3.34
14.73
2.74
5.32
11.43
8.21
1.67
3.42
–
3.82
–
3.43
21.82
–
1.42
7.32
–
0.0059
0.0214
0.0072
0.0362
0.0103
0.0426
0.0073
0.0172
0.0365
0.0220
0.0050
0.0333
0.0110
–
0.0118
–
0.0106
0.0630
–
0.0041
0.0207
–
C8
C6
C3
C5
61.23
–
5.43
–
0.0162
–
>100.0
12.42
(Cr-Cr’ ¼ solid to solid crystal; Cr-SmC ¼ solid to SmC; Cr-N ¼ solid to nematic; N-I ¼ nematic to isotropic)
Figure 11. XRD patterns of compound C5 at 62˚C.
However, in case of antifungal activity, comp.C3, C4, C6, C7, C8, C10 and C12 showed
good results in C.Albicans at 500 mg/mL which was equivalent to standard drug
greseofulvin.
3.6.1. In vitro antibacterial activity
Table 4 shows that all the newly synthesised compounds were found to exhibit good to
moderate activity against specific microbial strains. Initially, we screened all the synthes-
ised compounds (C3 to C12) for their antibacterial activity in vitro by using both dilu-
tion methods [34]. The in vitro antibacterial results confirmed that some of the
chalconyl-ester hybrids exhibited antibacterial activity against various strains of E.coli,
P.aeruginosa (Gram–ve) and S.aureus, S.pyogenus (Gram þ ve) as shown in Table 5. An
antibacterial result was comparatively nearer to the standard drug ampicillin as compare
to other drug. While, C3 to C12 showed activity (62.5 mg/ml MIC and 100mg/ml MIC)
against E.coli, which is nearer to the standard value of ampicillin. Furthermore,

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
23
Figure 12. XRD patterns of compound C12 at 41˚C.
Table 5. Result of antibacterial activity of the synthesized compounds
ANTIBACTERIAL ACTIVITY
Minimal Inhibition Concentration
Code
No.
E.Coli
MTCC 443
P.Aeruginosa
MTCC 442
S.Aureus
MTCC 96
S.Pyogenus
MTCC 442
Sr.No
Microgramm / ML
1
2
3
4
5
6
7
Standard
Standard
Standard
Standard
C3
C4
C5
C6
C7
C8
C10
62.5
62.5
62.5
100
62.5
100
100
100
0.05
50
125
100
125
100
200
100
125
100
1
100
200
200
100
100
100
250
250
0.25
50
62.5
100
62.5
100
62.5
100
62.5
100
0.5
Ampicillin
Gentamycin
Chloramphenicol
Ciprofloxacin
50
25
50
50
25
50
compound C3, C4, C5, C8, C10 and C12 having excellent growth inhibition at lower con-
centration (62.5mg/ml MIC) as compare to standard drug. Compound C3 to C12 showed
activity against P.aeruginosa at (100 mg/ml MIC and 125 mg/ml MIC) which was further
compare with the standard drug. However, compound C5 (120 mg/ml MIC) and C6
(125 mg/ml MIC) showed activity at higher concentration. Compound C3, C5, C7 and
C10 showed good inhibitory activity with lower concentration (62.5 mg/ml MIC) against
S.Pyogenus while remaining compound showed higher MIC value respectively.
3.6.2. In vitro antifungal activity
Antifungal activity data displayed in Table 6 which indicates the results of compound
C3 to C12 showed adaptable degrees of inhibition against the tested fungi C.Albicans,
A.Niger, A.Clavatus. C.Albicans fungi were inhibited by C3, C4, C6, C8 and C10 at 500

24
D. K. SHUKLA ET AL.
Table 6. Result of antifungal activity of the synthesized compounds
ANTIFUNGAL ACTIVITY
Minimal Fungicidal Concentration
C.Albicans
A.Niger
A.Clavatus
Sr.No
Code. No.
C3
C4
C5
C6
C7
C8
C10
MTCC 227
MTCC 282
MTCC 1323
Microgramm / ML
1
2
3
4
5
6
7
500
500
250
500
250
500
500
100
500
250
1000
250
250
1000
250
250
100
100
200
250
200
250
250
250
250
100
100
Standard
Standard
Nystatin
Greseofulvin
mg/ml MIC which is equal to the concentration of standard drug Greseofulvin.
However, compound C5 and C7 showed lower MIC as compared to other synthesized
derivatives respectively. While inhibiting against A.Niger, A.Clavatus fungi by com-
pound C3, C5, C6, C8 and C10 at 250 mg/ml MIC, while remaining compounds showed
poor activity.
4. Conclusions
A new calamitic rod type chalcone-derived LCs compounds based on three phenyl rings
as rigid core possessing two linking unit, lateral nitro group and N,N-dimethyl amino
as terminal group at one end and other end with variable alkyl chain length in alkoxy
group (-OR). Interestingly, it can be noted that seven compounds from this synthesized
series showed good antimicrobial activity. The antibacterial and antifungal activity was
determined by MIC (Broth dilution method). The POM and DSC measurements con-
firmed the presence of enantiotropic nematic as well as smectic mesophase. The lower
member (comp.C3 to C5) shows enantiotropic smectic C phase while higher member
(comp. C6 to C18) shows enantiotropic nematic phase at room temperature having
lower value of thermal stability. The group efficiency order derived on the basis of (a)
thermal stability, (b) early or late commencement of mesophase, (c) Temperature range
of mesophase.
Acknowledgement
DS and RBP acknowledge thanks to Dr. R.R.Shah, principal and management of K. K. Shah
Jarodwala Maninagar Science College, Ahmedabad for providing research lab and other facility.
VS and VP thanks to Department of Chemistry, Faculty of Basic and Applied Science, Sirohi,
Rajasthan for providing lab facility. Authors thanks to Mr.Anuj Patel for providing DFT study of
present synthesized compounds. Authors are also thankful to NFDD Centre for providing analyt-
ical and spectral services.
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