Synthesis, mesomorphic properties and biological evolution of calamitic-shaped chalcone-based LCs: effect of lateral and terminal group

Article abstract of DOI:10.1080/15421406.2021.1895961

The mesomorphic properties of linear shaped homologous series based on two linkage group have been designed and synthesized with different side chain substituents (-OR) on the one end of terminal side with presence of lateral nitro group and second terminal iodo substituted group. Novel series consists thirteen members (C₁ to C_8, C₁₀, C₁₂, C₁₄, C₁₆, C₁₈). Compounds (C₁ to C₆) showed nonliquid crystalline properties while compound (C₇ to C₁₈) displayed smectic and nematogenic mesophase properties. The textures of smectic C and nematic phase are fan, schlieren and droplets type. All these compounds were characterized by spectroscopic techniques such as [FTIR] and ¹H Nuclear magnetic resonance [NMR] spectroscopy. The mesomorphic properties of these compounds were observed by POM and further confirmed by DSC and XRD. Chalconyl ester based compounds (C₃ to C₁₂) shows good antibacterial as well as antifungal activity compared with corresponding standard drugs.

Full text of DOI:10.1080/15421406.2021.1895961

Molecular Crystals and Liquid Crystals
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/gmcl20
Synthesis, mesomorphic properties and biological
evolution of calamitic-shaped chalcone-based LCs:
effect of lateral and terminal group
Durgesh J. Dwivedi, Akshay Thakor, Vipul Desai, Vinay S. Sharma & R. B.
Patel
To cite this article: Durgesh J. Dwivedi, Akshay Thakor, Vipul Desai, Vinay S. Sharma & R. B.
Patel (2021): Synthesis, mesomorphic properties and biological evolution of calamitic-shaped
chalcone-based LCs: effect of lateral and terminal group, Molecular Crystals and Liquid Crystals,
DOI: 10.1080/15421406.2021.1895961
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MOLECULAR CRYSTALS AND LIQUID CRYSTALS
https://doi.org/10.1080/15421406.2021.1895961
Synthesis, mesomorphic properties and biological
evolution of calamitic-shaped chalcone-based LCs: effect
of lateral and terminal group
Durgesh J. Dwivedia, Akshay Thakora, Vipul Desaia, Vinay S. Sharmab, 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 Basic and Applied Science, Madhav
University, Sirohi, Rajasthan, India
KEYWORDS
ABSTRACT
Chalcone; enantiotropic;
mesogens; nematic;
smectic C
The mesomorphic properties of linear shaped homologous series
based on two linkage group have been designed and synthesized
with different side chain substituents (-OR) on the one end of ter-
minal side with presence of lateral nitro group and second terminal
iodo substituted group. Novel series consists thirteen members (C1
to C8, C10, C12, C14, C16, C18). Compounds (C1 to C6) showed nonli-
quid crystalline properties while compound (C7 to C18) displayed
smectic and nematogenic mesophase properties. The textures of
smectic C and nematic phase are fan, schlieren and droplets type.
All these compounds were characterized by spectroscopic techni-
1
ques such as [FTIR] and H Nuclear magnetic resonance [NMR] spec-
troscopy. The mesomorphic properties of these compounds were
observed by POM and further confirmed by DSC and XRD. Chalconyl
ester based compounds (C3 to C12) shows good antibacterial as well
as antifungal activity compared with corresponding standard drugs.
CONTACT R. B.Patel
roshanpatel770@gmail.com
Department of Chemistry, K.K.Shah Jarodwala Maninagar
Science College, Gujarat University, Ahmedabad 380008, Gujarat, India.
ß 2021 Taylor & Francis Group, LLC

2
D. J. DWIVEDI ET AL.
1. Introduction
Liquid crystal (LC) is an intermediate state of a matter in between the liquid and the
crystal behaving with some typical properties of a liquid as well as some crystalline
properties. There are many kinds of LC materials with different molecular structures,
based on which LC could be divided into three categories, that is, calamatic liquid crys-
tal, bent-shape liquid crystal and discotic liquid crystal. Calamatic LCs materials are
widely used in a flat-panel display, smart windows, laser and other photonics. Liquid
crystalline (LC) chalconyl ester derivatives play dual role useful in LC devices and
pharmaceutical preparation and therapeutically treatment to cure diseases within defin-
ite range of concentration in solution state [1–5]. Liquid crystals in the nematic group
are most commonly used in production of liquid crystal displays (LCD) due to their
unique physical properties and wide temperature range. In the nematic phase, liquid
crystal molecules are oriented on average along a particular direction. By applying an
electric or magnetic field the orientation of the molecules can be derived in a probable
approach [6–14].
Chalcone is an important class of chemical compound and is being studied exten-
sively because of its significant use or application in various sectors. In the fields of
biology and biochemistry, chalcone has been claimed to be one of the compounds that
plays a vital role in anti-tumor [15,16], anti-inflammatory [17,18], and anti-malarial
[19] activities. It has also been documented that the chalcone possesses a remarkable
nonlinear optical (NLO) property, which is an essential element for optical communica-
tion devices [20]. The other importance of this compound is its high photosensitivity
and thermal stability, which are used in development of various crystalline electro-
optical devices [21–23]. The effects of laterally substituted group on mesogens are con-
siderable interesting because these compounds deviate from the classical rod-like
shape [24–31].
In literature, similar homologous series based on ester-chalcone groups has been
reported till the date. R.Gopalakrishnan et al. reported chalcone based single crystals,
growth, and comparison of two new enone shifted chalcones and their NLO behavior
[32]. Tandel et al. studied the chain chalconyl polymers compounds to exhibiting
threaded type nematic phases [33]. 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 [34,35]. Shah et al.
studied a nonlinear homologous series based on ester and chalcone linkage group [36].
Patel et al. reported rod type homologous series having chalconyl ester central linkage
group and hexyloxy tail group [37].Gallardo and his coworkers reported polycatenar
liquid crystals series based on bent shaped chalcone and cyanopyridine molecules [38].
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 [39]. Rai et al. reported unsymmetrical liquid
crystalline compounds based on chalcones and 3,5-disubstituted isoxazoles derivatives
[40]. Karawi et al. reported chalcone based pyrazoles liquid crystals and also studied
their photo-luminescent behaviors [41]. On continues working on to design chalcone
based LCs, we have reported homologous series based on three phenyl rings bonded
through –CH ¼ CH-COO- and –CO-CH ¼ CH- linking groups as well as varying left n-

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
3
alkoxy terminal end group and a fixed tail part at right side ended group and various
halogen group [42–47]. Very recently, we have reported chalcone biphenyl amine func-
tionalized calixarene based blue-light emitting supramolecular liquid crystal and investi-
gated their OLEDs application [48].
In present research article, we have planned to synthesized chalcone-based homo-
logues series and study the effects of tail group (-OR) and lateral group (-NO2) on LCs
properties of present synthesized iodo based mesogens. Further, the structure-function
relationship was further studied with structural similar reported series by our group.
The liquid crystalline behavior is preliminary checked by polarizing optical microscopy
(POM) and further confirmed by differential scanning calorimetry (DSC) and PXRD
analysis respectively. In the present synthesized few selected derivatives showed good
antibacterial and antifungal activity.
2. Experimental
2.1. Materials
For present synthesized homologous series required materials: 4-iodo acetophenone, 4-
hydroxy benzoic acid, (Lancaster, England, SRL Mumbai), 2-nitro, 4-hydroxy benzalde-
hyde was purchased from (Sigma Aldrich), Anhydrous K2CO3, KOH were purchased
from (Finar Chemicals, India), N,N-dimethyl amino pyridine (DMAP) and
Dicyclohexylcarbodiimide (DCC) was purchased from Fluka Chemie (Switzerland). R-
Br (alkyl halide) (R ¼ CnH2nþ1, n ¼ 1 to 8, 10, 12, 14, 16, 18) were purchased from
S.R.L. Chemicals (Mumbai). The solvents were dried and purified by standard method
prior to use.
2.2. Measurements
Melting points were taken on Opti-Melt (Automated melting point system). The FT-IR
spectra were recorded as KBr pellet on Shimadzu in the range of 3800-600 cmꢀ1
.
Microanalysis was performed on Perkin-Elmer PE 2400 CHN analyzer. The texture
images were studied on a trinocular optical polarizing microscope (POM) equipped
1
with a heating plate and digital camera. H NMR spectra and 13C NMR were 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. Texture image of nematic phase were deter-
mined by miscibility method, thermodynamic quantities enthalpy (DH) and entropy
(DS ¼ DH/T) are qualitatively discussed. For the POM analysis, the synthesized com-
pound is sandwiched between to glass slide and cover slip and heating and cooling rate
is (2˚C/min).
2.3. Synthesis
4-n-alkoxy benzoic acids (A) prepared by reported method [36]. 1-(4-hydroxy-3-nitro-
phenyl)-3-(4-(iodo) phenyl) prop-2-en-1-one (B) was prepared by usual established
method [34]. Final target chalcone-ester derivatives (series-A) were synthesized by a

4
D. J. DWIVEDI ET AL.
Scheme 1. (i) R-Br, KOH, MeOH, Reflux; (ii) EtOH, KOH, r.t. Stirring, 24 hr; (iii) DCC, DMAP, DCM,
r.t. 48 h.
method reported in literature [47]. Thus, the Chalconyl-Ester homologue derivatives
were filtered, washed with sodium bicarbonate solution, dried and purified till constant
transition temperatures is obtain, using an optical polarizing microscope equipped with
a heating stage. The synthetic route to a series is mentioned in Scheme 1.
2.3.1. Synthesis of 4-n-alkoxy benzoic acid (A)
4-hydroxy benzoic acid alkylated by alkylating agent (R-Br), KOH, MeOH (C1 to C8)
and Ethanol (C10 to C16), increasing reflux time period with increasing chain to yield

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
5
1
corresponding 4-n-alkoxy benzoic acids (A), which was confirmed by IR and H NMR
study [36].
2.3.2. Synthesis of chalcone (B)
Chalcone (B) was prepared by usual established method reported in the literature [34].
2.3.3. Synthesis of ester derivatives (Series-A)
The compound has been prepared by esterification of the appropriate 4-n-alkoxy ben-
zoic acid (A) (1.0 mmol) and chalcone (B) (1.02 mmol), dicyclohexylcarbodiimide
(DCC) (1.22 mmol) and dimethylaminopyridine (DMAP) in catalytic amount
(0.2 mmol) in dry CH2Cl2 (DCM) (30 ml) was stirred at room temperature for 48 h. The
white precipitate of DCU is obtained which was isolated by filtration and discarded,
while the filtrate was evaporated to dryness. The resultant crude residue was purified by
column chromatography on silica gel eluting with dichloromethane: methanol, recrystal-
lization from methanol: chloroform (2:3) until constant transition temperatures were
observed [47].
2.3.4. Reaction scheme
2.3.4.1. Analytical data
Chalcone (B): FT-IR (KBr) in cmꢀ1: 3016-3030 (-C-H- str in CH3), 1510-1450 (N-O str
bands), 1450 (N-O str bands), 1365 and 1219 (>C ¼ O str), 940 (trans, -CO-CH ¼ CH-,
1
-CH ¼ CH), 802 disubstituted aromatic ring (para), 1640 (-C ¼ O) group. H NMR: dH
(CDCl3, 400 MHz): 8.02 (d, J ¼ 15.1 Hz, 1H, -CO-CH ¼ CH-), 7.53-7.55 (d, J ¼ 15.1 Hz,
1H, -CO-CH ¼ CH-), 6.94-6.94 & 7.62-7.61 (2H, J ¼ 7.5 Hz, second phenyl ring) , 8.44,
827 & 7.40, (4H, J ¼ 7.1 Hz, first phenyl ring), 5.30 (1H, -OH group).; 13C NMR
(CDCl3): d ppm 14.0 (CH3 of –OC5H11 chain), 22.72–29.36 (CH2 aliphatic), 68.67
(-OCH2), 114.31, 129.78, 131.21, 120.22, 137.41, 137.42, 157.84 (Ar-C), 120.32 (a carbon
of -CO–CH ¼ CH), 144.98 (b carbon of CO–CH ¼ CH), 185.52 (C ¼ O group
of chalcone).
Butyloxy (C4): FT-IR (KBr): 636 Polymethylene (-CH2-)n of –OC5H11, 839 (–C-H-
def. di-substituted-para), 759 Polymethylene (-CH2-) of –OC4H9, 920 (–C-H- def.
hydrocarbon), 1028 and 1068(>C ¼ O str), 1197 and 1250 (>C ¼ O str) in –(CH2)n
chain, 1427 (-C-H- def. in CH2), 1510-1450 (-N-O str bands), 1514 (-C ¼ C-)str, 1658
1
(-C ¼ O group), 1740 (-COO- ester group), 2840 and 2960 (-C-H str in CH3). H NMR
(CDCl3): d ppm 0.88-0.90 (t, 3H, -CH3 of –OC5H11 & –OC4H9), 1.31 & 1.45 (q, 2H,
-CH2 of -OC4H9), 1.76 (P, 2H of –OC4H9 group), 4.06 (t,2H,-O-CH2-CH2-of -OC4H9),
7.56 (d, 1H, J ¼ 15.1 Hz, -CO-CH ¼ CH-), 8.32 (d, 1H, J ¼ 15.1 Hz, -CO-CH ¼ CH-),
7.14-7.15 & 8.11-8.12 (d, 4H, left side phenyl ring), 7.82 & 8.68, 8.51 (3H, central phe-
nyl ring), 7.62-7.61 & 6.94-6.92 (d, 4H, terminal phenyl ring).
Pentyloxy (C5): FT-IR (KBr): 636 Polymethylene (-CH2-)n of –OC4H9, 839 (–C-H-
def. di-substituted-meta), 781 Polymethylene (-CH2-) of –OC5H11, 952 (–C-H- def.
hydrocarbon), 1028 and 1068(-C-O-) Str, 1197 and 1228 (>C ¼ O str in –(CH2)n chain,

6
D. J. DWIVEDI ET AL.
1440 (-N-O str.), 930 (Trans, -CH ¼ CH-)str, 1604 and 1666 (>C ¼ O group), 1726
1
(-COO- ester group), 2850 and 2970 (-C-H str in CH3). H NMR (CDCl3): d ppm 0.88-
0.90 (t, 3H, -CH3 of –OC5H11), 1.31 (q, 2H, -CH2 of -OC5H11), 1.76 (P, 2H of
–OC5H11 group), 4.06 (t, 2H,-O-CH2-CH2-of -OC5H11), 7.58 (d, 1H, J ¼ 15.1 Hz, -CO-
CH ¼ CH-), 8.04 (d, 1H, J ¼ 15.1 Hz, -CO-CH ¼ CH-), 7.14-7.15 & 8.11-8.12 (d, 4H, left
side phenyl ring), 7.82 & 8.68, 8.51 (3H, central phenyl ring), 7.62-7.62 & 6.94-6.93 (d,
4H, terminal phenyl ring).
Hexyloxy (C6): FT-IR (KBr): 636 Polymethylene (-CH2-)n of –OC4H9, 839 (–C-H-
def. di-substituted-meta), 688 Polymethylene (-CH2-) of –OC6H13, 951 (–C-H- def.
hydrocarbon), 1028 and 1068(>C ¼ O) str, 1197 and 1440 (-N-O- str.), 1514 (-C ¼ C-)str,
1604 and 1666 (>C ¼ O group), 1726 (-COO- ester group), 2850 and 2970 (-C-H str in
1
CH3). H NMR (CDCl3): d ppm 0.88-0.90 (t, 3H, -CH3 of –OC6H13), 1.39-1.43 (t, 2H,
-OC6H13), 1.23-1.28 (m, 6H, -CH2 of -OC6H13), 1.76 (P, 2H of –OC6H13 group), 4.06 (t,
2H,-O-CH2-CH2- of -OC6H13), 7.58 (d, 1H, J ¼ 15.1 Hz, -CO-CH ¼ CH-), 8.02 (d, 1H,
J ¼ 15.1Hz, CO-CH ¼ CH-), 7.14-7.15 & 8.11-8.12 (d, 4H, left side phenyl ring), 7.81 &
8.68, 8.51 (3H, central phenyl ring), 7.62-7.61 & 6.94-6.93 (d, 4H, terminal phenyl ring).
Heptyloxy (C7): FT-IR (KBr): 636 Polymethylene (-CH2-)n of –OC4H9, 839 (–C-H-
def. di-substituted-meta), 701 Polymethylene (-CH2-) of –OC7H15, 952 (–C-H- def.
hydrocarbon), 1028 and 1068(>C ¼ O) str, 1197 and 1228 (>C ¼ O str) in –(CH2)n
chain, 1440 (-N-O- str.), 1514 (-C ¼ C-)str, 1604 and 1660 (>C ¼ O group), 1760
1
(-COO- ester group), 2850 and 2970 (-C-H str in CH3). H NMR (CDCl3): d ppm 0.88-
0.90 (t, 3H, -CH3 of –OC7H15), 1.26 (m, 6H, -OC7H15), 1.76 (P, 2H of –OC7H15 group),
4.06 (t, 2H,-O-CH2-CH2-of -OC7H15), 7.58 (d, 1H, J ¼ 15.1 Hz, -CO-CH ¼ CH-), 8.06
(d, 1H, J ¼ 15.1 Hz, -CO-CH ¼ CH-), 7.14-7.15 & 8.11-8.12 (d, 4H, left side phenyl
ring), 7.81 & 8.68, 8.51 (3H, central phenyl ring), 7.62-7.62 & 6.94-6.93 (d, 4H, terminal
phenyl ring).
Decyloxy (C10): FT-IR (KBr): 637 Polymethylene (–CH2–)n of –OC4H9, 839 (–C–H–
def. di-substituted-meta), 821 Polymethylene (-CH2-) of –OC10H21, 952 (–C-H- def.
hydrocarbon), 1028 and 1068(>C ¼ O) Str, 1197 and 1228 (>C ¼ O str in –(CH2)n
chain, 1440 (-N-O- str.),1514 (–C ¼ C–)str, 1666 (>C ¼ O group), 1730 (-COO- ester
1
group), 2850 and 2970 (-C-H str in CH3). H NMR (CDCl3): d ppm 0.88-0.90 (t, 3H,
-CH3 of –OC10H21), 1.29 (m, 12H, of –OC10H21), 1.76 (P, 2H of –OC10H21 group), 4.06
(t,2H,-O-CH2-CH2- of -OC10H21), 7.58 (d, 1H, J ¼ 15.1 Hz, -CO-CH ¼ CH-), 8.02 (d,
1H, J ¼ 15.1 HZ, -CO-CH ¼ CH-), 7.14-7.15 (d, 4H, left side phenyl ring), 7.82 & 8.68,
8.51 (3H, central phenyl ring), 7.62-7.61 & 6.94-6.92 (d, 4H, terminal phenyl ring).
Dodecyloxy (C12): FT-IR (KBr): 636 Polymethylene (–CH2–)n of –OC4H9, 839
(–C–H– def. di-substituted-meta), 759 Polymethylene (–CH2–) of –OC12H25, 952
(–C–H– def. hydrocarbon), 1028 and 1068(>C ¼ O) Str, 1197 and 1228 (>C ¼ O str.)
in (–CH2)n chain, 1440 (–N–O– str.),1514 (–C ¼ C–)str, 1640 (>C ¼ O group), 1726
1
(-COO- ester group), 2850 and 2970 (–C–H str in CH3). H NMR (CDCl3): d ppm
0.88–0.90 (t, 3H, -CH3 of –OC12H25), 1.29 (m, 14H, of –OC12H25), 1.31 (q, 4H, -CH2
of -OC12H25), 1.76 (P, 2H of –OC12H25 group), 4.06 (t, 2H,–O–CH2–CH2-of
–OC12H25), 7.58 (d, 1H, J ¼ 15.1 Hz, –CO–CH ¼ CH-), 8.02 (d, 1H, J ¼ 15.1 HZ,–-
CO–CH ¼ CH–), 7.14–7.15 & 8.11–8.12 (d, 4H, left side phenyl ring), 7.82 & 8.68, 8.51
(3H, central phenyl ring), 7.61–7.62 & 6.93–6.92 (d, 4H, terminal phenyl ring).

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
7
3. Result and discussion
3.1. Pom analysis
In order to investigate the influence of the central linkage group with respect to lateral
nitro and terminal substituted iodo group with varying left alkoxy variable side chain
on the mesomorphic properties of the present synthesized chalconyl materials. In this
present investigation, we have prepared calamitic rod-shaped homologous series with
total thirteen compounds (C1 to C8, C10, C12, C14, C16, C18). In this present study, we
have find out liquid crystalline materials with good thermal stability. In series-A, com-
pounds C1 to C6 shows nonmesomorphic properties and directly passes through iso-
tropic liquid from solid state, this is mainly due to short alkyl spacer in left side chain
causes more crystallinity and directly converted into isotropic phase without displaying
LC phase either heating or cooling condition.
The nonmesomorphicity of C1 to C6 homologous is attributed due to the appearance
of low magnitudes intermolecular dispersion forces and low magnitudes of dipole-dipole
interfaces leading to high crystallizing tendency due to short alkyl chain length as result
it causes hasty breaking of crystal lattices because of unsuitable magnitudes of aniso-
tropic forces of intermolecular desirability [2–4]. Thus, improper breaking of crystal lat-
tices which directly melts at reaching its isotropic temperature on heating and on
further cooling the solidification is taking place without displaying of liquid crystalline
phase [3]. One can see that, higher chain substituted compounds (C7 to C18) showed
liquid crystalline properties with good mesophase temperature range respectively. Cr-
SmC, SmC-N and N-I is plotted against the phase transition temperature versus the
number of carbon atoms in n-alkyl chain at (left alkoxy side chain) as shown in
Figure 1. All phase transition curves showed descending behavior till the last homo-
logue, this is due to the higher flexibility of the molecule along with polarity. Presence
of lateral substituted polar nitro group at lateral position along with terminal iodo
group on central phenyl ring, increases molecular aromaticity, polarity and polarizability
of molecules [34,35]. The phase transition temperature of series-A is shown in Table 1.
Figure 1. Phase diagram of newly synthesized Series-A.

8
D. J. DWIVEDI ET AL.
ꢁ
Table 1. Transition Temperature in C by POM.
0
Transition temperatures in C
Sr.no
R ¼ n-alkyl group
Cr
Smectic
Nematic
Isotropic
173.0
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
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
169.0
167.0
161.0
158.0
151.0
142.0
131.0
130.0
123.0
121.0
118.0
96.0
C3
C4
C5
C6
C7
C8
C10
C12
C14
C16
C18
–
–
–
–
–
–
–
–
ꢂ
ꢂ
138.0
126.0
121.0
119.0
110.0
108.0
89.0
ꢂ
ꢂ
ꢂ
9
ꢂ
ꢂ
10
11
12
13
ꢂ
ꢂ
96.0
91.0
68.0
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
The presence of odd-even parity on n-alkyl chain create variation in phase transi-
tion temperatures, this is due to the odd and even number of methylene units present
in the n-alkyl side chain of left n-alkoxy chain group. The exhibition of smectic C
phase in present synthesized higher homologues (C14, C16, C18), due to the formation
of molecular lamellar packing of in crystal lattices which maintains sliding layered
molecular arrangement in floating condition under the influence of exposed thermal
vibrations on heating and cooling conditions [36]. The exhibition of nematic property
from C7 homologue to C18 homologue is attributed due to the presence of suitable
magnitudes of anisotropic at end to end side intermolecular attractions and appropri-
ate permanent dipole moment across the long molecular axis., dispersion forces,
dipole-dipole interactions, shape, size, magnitudes of polarity and polarizability etc.,
which maintains floating of the homologue in statically parallel orientational order to
adopt nematogenic character, under exposed thermal vibrations; either directly or via
smectic phase in enantiotropic manner [37]. Texture images of some selected com-
pounds are mention in Figure 2 respectively. Compound C12 showed needle type tex-
ture pattern of SmC phase at 96.0 ꢁC which on further heating, exhibited nematic
mesophase at 119.0 ꢁC and finally converted into isotropic liquid at 123.0˚C.
Compound C18 with octadecyloxy tail group exhibited needle type texture image of
smectic C phase at 68.0 ꢁC on heating conditions respectively, which was further con-
firmed by DSC analysis. Similar texture patterns are found for other synthesized chal-
conyl-ester derivatives.
3.2. DSC study
DSC is a valuable method for detecting phase transitions. The thermal behavior of
novel homologues series was confirmed by using DSC measurement shown in Figure
3. DSC thermogram traces under heating and cooling condition. Compound C18
showed three endothermic and exothermic peaks on heating and cooling condition.
On heating condition, three endothermic peaks are traced at 62.5 ˚C, 84.5 ˚C and
109.8 ꢁC corresponding to Cr-SmC, SmC-N and N-I phase transition. While on

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
9
Figure 2. Texture image of Series-A observed between cross polarizers: (a) SmC of C12 homologue at
96.0˚C; (b) SmC of C18 homologue at 68.0˚C.
Figure 3. DSC thermogram of conpound (a) C18; (b) C16; (c) C14; (d) C12 homologues on heating and
cooling condition.
cooling condition, three exothermic peaks are traced at 107.1 ꢁC, 81.2 ˚C and 57.2 ˚C.
For C16 homologue, three significant peaks is observed at 90.4 ꢁC, 106.2 ˚C and 121.6
˚C corresponding to three phase transition, while on cooling condition it again
revealed at 123.2 ˚C, 104.6 ˚C and 69.4˚C respectively. This is nearly to the transition
temperature observed by POM investigation. Similarly compound C14 showed three

10
D. J. DWIVEDI ET AL.
Table 2. 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-SmC
SmC-N
N-I
62.5
84.6
109.8
57.2
81.3
107.1
9.11
10.14
5.12
7.63
12.73
6.45
0.0271
0.0283
0.0134
0.0231
0.0359
0.0169
C16
Cr-SmC
SmC-N
N-I
90.4
106.2
121.6
83.5
104.6
123.2
7.82
16.14
6.43
4.48
17.35
7.56
0.0215
0.0425
0.0162
0.0125
0.0459
0.0190
C14
Cr-SmC
SmC-N
N-I
Cr-N
N-I
Cr-N
N-I
92.1
120.4
126.8
123.4
134.8
116.8
134.6
82.4
117.4
127.6
121.3
135.9
112.3
137.9
10.06
18.39
3.78
14.22
8.62
9.17
4.04
7.49
16.01
6.98
12.54
7.67
10.78
7.89
0.0275
0.0467
0.0094
0.0358
0.0211
0.0235
0.0099
0.0210
0.0410
0.0174
0.0318
0.0187
0.0279
0.0192
C8
C10
endothermic peaks at 92.1 ˚C, 120.4 ˚C and 126.8 ˚C on heating and three exothermic
peaks at 127.6 ˚C, 117.4 ˚C and 82.4 ˚C on cooling condition corresponding to three
phase transition observed on enantiotropical manner respectively. One can see that,
higher chain substituted derivatives showed lamellar type of molecular arrangement
and showed smectic C type of molecular arrangements. Compound C12 showed two
endothermic peaks at 123.4 ˚C and 134.8 ˚C corresponding to Cr-N and N-I phase
transition while on cooling condition, it again traced at 135.9 ˚C and 121.3 ˚C which
was further confirmed by POM study. Two endothermic peaks traced for C10 homo-
logue at 117.4˚C and 139.1˚C on heating condition. Transition temperature obtained
by DSC analysis at heating and cooling condition and the values of enthalpy and
entropy is mention in Table 2. Molecules of every homologue randomly oriented in
all possible directions with high order of disorder or entropy (DS ¼ DH/T) beyond iso-
tropic temperature and the enthalpy value (DH). But, at cooled condition, the same
from and below isotropic temperature, the mesophase is persisted to appear reversibly
at the high temperature at observed during heating condition [35]. The liquid crystal-
line phase obtained enantiotropical manner in present series is smectogenic and nem-
atogenic respectively.
3.3. Thermal stability of mesophase
Some LC parameters evaluated from thermotropic data of presently synthesized novel
series-A is compared with structurally similar series-X which was previously reported by
our research group [49] is mention in Figure 4. The linearity of the both series is differ-
ent at lateral group so their magnitudes of combined effects of molecular rigidity and
polarity may effect on liquid crystalline properties with respect to commencement of
mesophase and its temperature range respectively. Presences of –NO2 group at lateral
side in present series which may increase the polarity and polarizability of molecule as
compared to previously reported series-X. It can be noted that the presence of nitro
group in series-A decrease the thermal stability of mesophase in both phase transition
(Sm-N and N-I) as compared to series-X. The thermal stability parameters were studied

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
11
Figure 4. Structurally similar series-A with series-X.
from DSC analysis data and POM data obtained from synthesized chalcogens materials.
The stability of Sm-N and N-I phase transition in series-A are 102.3 ˚C and 123.0 ˚C
which are lower as compared to series-X (155.0 ˚C and 180.7 ˚C).
3.4. XRD investigation
To investigate the structure of the observed smectic and nematic phase in present syn-
thesized chalconyl-ester derivatives, we have performed high temperature XRD to cor-
relate with the results obtained from DSC and POM investigation to further understand
the molecular arrangement at phase transition temperature state respectively. The XRD
data of comp. C14, C12, C10 are shown in Figure 5 which indicates the X-ray pattern
shows the diffraction peaks in the small angle diffraction region corresponded to a
smectic C and further at higher temperature single diffraction peak appeared which
confirmed the nematic type molecular reorganization. A sharp peaks (2h ¼ 10–200’)
were observed during X-ray investigation. The reflections for the small-angle area cor-
respond to a smectic layer structure. The d-spacing for C14 at 2h ¼ 8.71 Å, 6.34 Å and
5.48 Å and reflections observed at 10.18˚, 14.21˚ and 16.32˚ occur at 96.0˚C further at
110.0˚C, comp.C14 traced only one diffuse peak at 24.98˚ and the calculated d-spacing
is 3.64 Å . In addition, comp. C16 showed three reflections at 2h ¼ 11.26, 16.04 and
19.42 and the calculated d-spacing value is found to be 7.88 Å, 5.57 Å and 4.3 Å.
Compound C12 showed single diffuse reflections at 21.28˚ with 4.24 Å d-spacing length
indicates the absence of any well-ordered smectic type molecular arrangement. It is
observed that the presence of higher alkyl chain at left terminal side group in C14, C16
and C18 homologues may increase the arrangement of molecules in ordering layered
and formation of molecules in smectic mesophase. The arrangement of molecule is iso-
meric calamatic rod type shape. The lower member of the present series showed nem-
atic type mesophase while higher members of the present series showed smectic C type
mesophase. This is due to the molecular packing of the alkyl chains with linking groups
oriented tilted way directions and nitro group substituted at lateral side in smectic
layers structure and effect of flexibility to induce smectic mesophase. The theoretical

12
D. J. DWIVEDI ET AL.
Figure 5. XRD traces of compound C14 (a); C16 (b); C10 (c); C14 (d) measured at transition
Temperature obtained from POM study.
calculated d-spacing length of compound C14 is near to the observed or experimental d-
spacing length as shown in Figure 6. According to the graphical proposed mechanism,
the molecular are arranged in lamellar order, although, the long axes of the molecules
are tilted to the layers planes shown in Figure 7.
3.5. Biological evaluation
In the present work, the focus has been drawn on designing new structural entities of
iodo based nitro substituted chalcones inbuilt with 4-n-alkoxy benzoic acid to form
chalconyl-ester derivatives to evaluate the prospective effect on biological activity, par-
ticularly antibacterial and antifungal activity. Newly synthesized mesogens with two lat-
eral side groups 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 various 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

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
13
Figure 6. XRD traces of compound C14 (a) and C14 (b) measured at 96.0˚ and 110.0˚C.
Figure 7. Proposed molecular packing in present Series-A.
the broth dilution method. All the selected compounds (C3, C4, C5, C6, C7, C10 and
C12) showed good results and further compared with standard drugs.
3.5.1. In vitro antibacterial activity
Table 3 shows that all the newly synthesized compounds were found to exhibit good to
moderate activity against specific microbial strains. Initially, we screened few selected
synthesized mesogens (C3 to C12) for their antibacterial activity in vitro by using both

14
D. J. DWIVEDI ET AL.
Table 3. 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
C3
62.5
62.5
62.5
62.5
100
100
100
100
0.05
50
100
125
100
100
125
200
125
100
1
100
100
250
100
250
100
100
250
0.25
50
62.5
200
100
100
62.5
100
100
100
0.5
2
C4
3
4
C5
C6
5
C7
6
7
C10
C12
Standard
Standard
Standard
Standard
Ampicillin
Gentamycin
Chloramphenicol
Ciprofloxacin
50
25
50
50
25
50
Table 4. Result of antifungal activity of the synthesized compounds.
Antifungal activity
Minimal fungicidal concentration
Sr.No
Code. No.
C.Albicans
A.Niger
A.Clavatus
MTCC 227
MTCC 282
MTCC 1323
Microgramm / ML
1
2
3
4
5
6
7
C3
C4
C5
C6
C7
C10
C12
Nystatin
500
1000
500
1000
500
1000
500
100
250
1000
250
>1000
250
1000
250
>1000
250
>1000
100
250
1000
1000
250
Standard
100
Standard
Greseofulvin
500
100
100
dilution methods. It is interesting to note that all selected mesogens showed excellent
antibacterial activity. The in vitro antibacterial results confirmed that some of the chal-
cone hybrids exhibited antibacterial activity against various strains of E.coli,
P.aeruginosa (Gram–ve) and S.aureus, S.pyogenus (Gram þ ve). An antibacterial result
was comparatively nearer to the standard drug ampicillin as compare to other drug.
Comp. C3 to C6 having excellent activity (62.5 mg/ml MIC) against E.coli. Furthermore,
compound C7, C10 and C12 showed growth inhibition at lower concentration (62.5 mg/
ml MIC) as compare to standard drugs. Compound C3 to C12 showed good activity
against P.aeruginosa at (100 mg/ml MIC and 125 mg/ml MIC) which was further compared
with the standard drug. However, comp.C4 (120 mg/ml MIC) and C5 (125 mg/ml MIC)
and comp. C12 showed activity at higher concentration. Compound C3 and C7 exhibited
good inhibitory activity with lower concentration (62.5mg/ml MIC) against S.Pyogenus.
3.5.2. In vitro antifungal activity
Antifungal activity data displayed in Table 4 which indicates the results of compound
C3 to C12 showed adaptable degrees of inhibition against the tested fungi C.Albicans,

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
15
A.Niger, A.Clavatus. C.Albicans fungi were inhibited by C3, C5, C7 and C12 at 500 mg/ml
MIC which is equal to the concentration of standard drug Greseofulvin. While inhibit-
ing against A.Niger, A.Clavatus fungi by compound C3, C5, C6 and C12 at 250 mg/ml
MIC, while all the other derivatives exerted moderate to poor activity profiles.
4. Conclusions
A new calamitic chalconyl-ester mesogens based on two linking groups and three ben-
zene core as rigid core possessing one lateral group with variable alkoxy side chain
group (-OR). The liquid crystalline properties of the synthesized mesogens were carried
out by using POM, DSC and XRD techniques which revealed the occurrence of enantio-
tropic nematic as well as smectic C phase. The lower member comp. (C1 to C6) shows
non-mesogenic nature due to the presence of short alkoxy side spacer in left side ter-
minal group. Further, comp. C7 to C12 showed only enantiotropical nematic phase while
comp. (C14 to C18) shows nematic as well as smectic C properties. Higher chain substi-
tuted members (C14, C16 and C16) showed well-ordered smectic C as well as nematic
properties. The group efficiency order derived on the basis of (a) mesophase thermal
stability, (b) early or late commencement of mesophase, (c) Temperature range of meso-
phase. The antibacterial and antifungal activity was determined by MIC (Broth dilution
method). All the synthesized mesogens exhibited good antibacterial as well as antifun-
gal activity.
Acknowledgments
DD, AT 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 thanks to the Department of Chemistry, Faculty of Basic and Applied Science, Sirohi,
Rajasthan for providing lab facility. Authors are also thankful to NFDD Centre for providing
analytical and spectral services. Author acknowledge thanks to Microcare Laboratory, Surat for
biological studies.
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