Synthesis and mesomorphic properties of novel Schiff base liquid crystalline EDOT derivatives

Article abstract of DOI:10.1016/j.molliq.2016.11.010

Herein, we reported novel banana liquid crystals derived from ethylenedioxythiophene (EDOT) central unit encompass with Schiff base. Structural charecterization of these compounds was carried out from their spectral and elemental analysis. Physical properties of all the newly synthesized compounds were investigated by polarising optical microscopy, differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction and Raman spectroscopy. EDOT bearing three-ring Schiff base bent-core compounds are non-mesomorphic but all the Schiff bases containing five-rings exhibit enantiotropic mesophase behaviour. The higher homologues show long range nematic phase along with a smectic C phase at lower temperature. While the lower homologues exhibit only N phase. The bent-angle in these compounds is in between of calamitic LCs and banana LCs; therefore, the molecules escape from the polar order packing observed in typical bent core LCs. Detailed XRD investigation endorses the presence of the N phase in lower homologues and Sm C phase in higher homologues.

Full text of DOI:10.1016/j.molliq.2016.11.010

MOLLIQ-06552; No of Pages 8
Journal of Molecular Liquids xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
Synthesis and mesomorphic properties of novel Schiff base liquid
crystalline EDOT derivatives
⁎
Ashwathanarayana Gowda, Arun Roy, Sandeep Kumar
Soft Condensed Matter Group, Raman Research Institute, C.V. Raman Avenue, Sadashivnagar, Bangalore 560 080, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Herein, we reported novel banana liquid crystals derived from ethylenedioxythiophene (EDOT) central unit en-
compass with Schiff base. Structural charecterization of these compounds was carried out from their spectral and
elemental analysis. Physical properties of all the newly synthesized compounds were investigated by polarising
optical microscopy, differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction and Raman
spectroscopy. EDOT bearing three-ring Schiff base bent-core compounds are non-mesomorphic but all the Schiff
bases containing five-rings exhibit enantiotropic mesophase behaviour. The higher homologues show long range
nematic phase along with a smectic C phase at lower temperature. While the lower homologues exhibit only N
phase. The bent-angle in these compounds is in between of calamitic LCs and banana LCs; therefore, the mole-
cules escape from the polar order packing observed in typical bent core LCs. Detailed XRD investigation endorses
the presence of the N phase in lower homologues and Sm C phase in higher homologues.
Received 16 September 2016
Accepted 5 November 2016
Available online xxxx
Keywords:
EDOT
Banana liquid crystals
Nematic phase
Smectic C phase
© 2016 Elsevier B.V. All rights reserved.
1. Introduction
shows extensive mesomorphic behaviour. The presence of heteroatoms
(N, O and S) can cause significant effects on polarity, polarisability,
Mesogenic shape anisotropy, central unit, connecting groups and flex-
ible alkyl chains are contemporary approaches to the design and synthesis
of thermotropic banana liquid crystals or bent-core liquid crystals (BC LC)
[1–3]. In 1996 Niori et al. [4], reinvestigated the mesomorphic behav-
iour of 1,3-phenylene-bis-[4-(4-n-octylphenylimino)methyl]benzoates
banana-shaped Schiff's base derivatives originally synthesized by
Matsunaga et al. [5]. Their studies revealed the unique features of ferro-
electric switching in these molecules, although the constituent mesogens
are achiral. After that, BC LCs have become subject of considerable re-
search interest to understand the structural property relationship in
these intriguing materials [6–14]. The BC LC derived from five, six and
seven aromatic rings have been found to form LC phases. Interestingly,
the first three-ring bent-core LCs exhibiting a nematic phase at room tem-
perature have recently been realized [15]. A number of bent-core
mesogens have been derived from several central cores such as
benzene, resorcinol, naphthalene, oxazole, oxadiazole, triazole, thiazole,
thiadiazole, thiophene, benzothiophene, benzodithiophene, pyridine-
2,6-dicarbaldehyde, pyrazabole, fluorenone [16].
dielectric, type of mesophase, phase transition temperatures and some-
time geometric shape [33]. In recent year, a number of 2,5-disubstituted
thiophene based mesomorphic compounds have been synthesized and
characterized for their mesophase behaviour [22–32]. The incorpora-
tion of thiophene core fragment in the mesogen can abundantly in-
crease optical anisotropy, devaluation in melting point, elevation of a
negative dielectric anisotropy, reduction of viscosity and fast switching
response [17], which makes them highly technological important
materials [34–36].
We have recently reported that 3,4-ethylenedioxythiophene
(EDOT), a thiophene based heterocyclic compound, can be used as a
novel central core unit for the synthesis of various thermotropic ba-
nana-liquid crystal [37]. EDOT acts as an electron rich unique building
block for the synthesis of various classes of molecular π-conjugated sys-
tems. At ambient temperature EDOT undergoes rapid polymerization
which has gained potential applications in fabrication of various elec-
tronic and optoelectronic devices such as field-effect transistors, photo-
voltaic devices, non-linear optical materials, light-emitting diode and
molecular switches [38–42]. LCs derived from thiophene unit are well
known in the literature [22–32], however extensive literature search re-
veals that any Schiff base bearing EDOT based BC LC has not been report-
ed so far. Herein, we report for the first time, the synthesis and
characterization of Schiff-base containing BC LC derived from EDOT.
Initially we designed and synthesized three-ring Schiff base com-
pounds as shown in Scheme 1, where central EDOT is flanked between
two phenyl rings via imine linkage. These three-ring compounds were
Mesomorphic compounds containing heterocyclic rings are gaining
increasing importance as thermotropic liquid crystals [17–34]. The
introduction of five-membered heterocyclic units such as 1,3,4-
oxadiazole [17,18], 1,2,4-oxadiazole [19,20], isoxazole [21], 1,3,4-
thiadiazole and thiophene [22–32] widens the bent angle and
⁎
Corresponding author.
E-mail address: skumar@rri.res.in (S. Kumar).
http://dx.doi.org/10.1016/j.molliq.2016.11.010
0167-7322/© 2016 Elsevier B.V. All rights reserved.
Please cite this article as: A. Gowda, et al., Synthesis and mesomorphic properties of novel Schiff base liquid crystalline EDOT derivatives, J. Mol.
Liq. (2016), http://dx.doi.org/10.1016/j.molliq.2016.11.010

2
A. Gowda et al. / Journal of Molecular Liquids xxx (2016) xxx–xxx
Scheme 1. Synthesis of EDOT-based BC LCs. (i) 1-bromooctadecane, K2CO3, dry. DMF,80 °C 12 h; (ii) 10% Pd/C, (1:1) EtOH:THF, r.t, 6 h; (iii) 4-alkoxybenzoic acid, DCC, DMAP, DCM, r.t,
12 h; (iv) 10% Pd/C, (1:1) EtOH:THF, r.t, 6 h; (v) n-BuLi (1.6 M), dry DMF, dry THF, −78 °C, 2 h; (vi) 3–4 drops glacial acetic acid, EtOH, reflux, 4 h.
found to be non-liquid crystalline, which is not much surprising as
three-ring structures are usually not conducive for BC LCs [43,44]. Fur-
thermore, to increase length: width ratio, we added one more phenyl
ring on each side by ester linkage to generate five-membered banana
liquid crystals bearing Schiff base as shown in Scheme 1. The 2,5-disub-
stituted EDOT with imine linkage exhibits the bent-angle of about 155°.
To understand the structure–property relationship and to develop novel
BC LCs of EDOT central unit, we prepared six novel derivatives in which
EDOT was converted into EDOT-2,5-dialdehyde as the key intermediate
for the synthesis of Schiff base containing three- and five-ring com-
pounds. The influence of terminal chains on mesophase transition tem-
peratures is studied by varying the length of the flexible alkyl chains. All
the five-membered mesogens in the series (9a–9f) were found to ex-
hibit enantiotropic mesophase behaviour. Higher homologues of the se-
ries show nematic phase along with semectic C phase at lower
temperature. The phase behaviour and phase transitions were investi-
gated by using polarising optical microscopy (POM), differential scan-
ning calorimetry (DSC) and X-ray diffraction techniques (XRD). The
thermal stability was measured with thermogravimetric analysis (TGA).
vibrational frequencies ensures that the optimized geometry corre-
sponds to a true energy minimum. From the DFT calculations, the ener-
gy and the length of fully extended Schiff base containing three-ring
compound 8b were found to be −6,814,984.61 kJ mol−1 and 60.83 Å
and for five-ring compound 9f these were, −9,242,837.16 kJ mol−1
and 64.57 Å respectively, as shown in Fig. 1. The dihedral angle between
central EDOT and phenyl ring with imine linkage is 159.35° in three-ring
compound 8b while in five-ring compound 9f, the dihedral angles be-
tween central EDOT and first phenyl ring with imine linkage, the first
and second phenyl ring with ester linkage are 156.97° and 146.22°, re-
spectively, reflecting the absence of coplanarity of the phenyl rings in
2. Results and discussions
2.1. Density functional theory studies
Novel EDOT based Schiff base BC LCs were designed as shown in
Scheme 1 and Fig. 1. GAUSSIAN-09 program package was employed to
carry out DFT calculations at the Becke's three-parameter functional
and Lee, Yang and Parr correlation functional (B3LYP). The 6–311 G(d)
basis set was used for ground-state geometry optimisation for C, H, N
atoms. The internal coordinates of the system, which is used as input
for GAUSSIAN-09 program was generated by the GAUSS VIEW 4.1 pro-
gram [45,46]. The absence of any imaginary frequency in the calculated
Fig. 1. DFT optimized structure. (a) The molecular structure of three-ring compound 8b
and (b) five-ring compound 9f optimized at DFT level. The bent angles are 167.17° (8b)
and 153.39° (9f), respectively. The dihedral angles reveal that the phenyl rings are out-
of-plane.
Please cite this article as: A. Gowda, et al., Synthesis and mesomorphic properties of novel Schiff base liquid crystalline EDOT derivatives, J. Mol.
Liq. (2016), http://dx.doi.org/10.1016/j.molliq.2016.11.010

A. Gowda et al. / Journal of Molecular Liquids xxx (2016) xxx–xxx
3
the molecule. The DFT optimized analysis shows that the bending angle
is approximately 167.17° in three-ring compound 8b and 153.39° in
five-ring compound 9f respectively.
textures were observed for all other derivatives. Upon heating com-
pound 9b melts at 163 °C and become isotropic liquid at 274 °C, nematic
droplets were observed on slow cooling from isotropic melts. On
heating, compound 9c melts at 159 °C and endure with crystal-crystal
transition at 166 °C and become isotropic liquid at 246 °C. Similarly,
compound 9d become isotropic liquid at 230 °C and nematic phase ob-
served during cooling.
2.2. Synthesis
Schiff base containing novel BC LCs were synthesized as shown in
Scheme 1. Lithiation of EDOT with n-BuLi in dry THF followed by N,N′-
dimethyl formamide (DMF) quenching gives EDOT-2,5-dialdehyde 7
as a key intermediate for the synthesis of three- and five-ring Schiff
base compounds. Compound 3a was purchased from commercial
source. O-alkylation of 4-nitrophenol with 1-bromooctadecane gives
compound 2. Reduction of compound 2 with H2 gas in presence of pal-
ladium on carbon catalyst at room temperature gives 4-(octadecyloxy)
aniline 3. Reaction of 4-butylaniline or 4-(octadecyloxy)aniline with
EDOT-2.5-dialdehyde 7 in presence of catalytic amount of glacial acetic
acid in absolute ethanol under reflux temperature gives Schiff base con-
taining three-ring BC non-mesogenic derivatives 8a–8b. Condensation
reaction of 4-Nitrophenol with 4-alkoxy benzoic acid in the presence
of N,N′-dicyclohexylcarbodiimide (DCC) and catalytic amount of 4-
dimethylaminopyridine (DMAP) affords compound 4, which yields
key intermediate 5 on reduction. Finally, the Schiff base containing
five membered mesogenic derivatives (9a–9f) were obtained by the re-
action of compound 5 with EDOT-2.5-dialdehyde 7. Detailed synthetic
procedure and characterization of all intermediate and final compounds
are described in the experimental section.
Compounds 9e and 9f show significant changes in texture from
schlieren texture to fan-like texture of smectic phase at low tempera-
ture (Fig. 2). To investigate the nature of this smectic phase, we used
commercial polyimide-coated cell (Instec Inc.) having 9 μm thickness
for planar alignment of the sample in the LC phases. The compound 9f
was filled uniformly in the LC cell at isotropic temperature. Upon
cooling from the nematic phase to lower temperature, shows a focal
conic fan-like texture of smectic phase as shown in Fig. 2c and d respec-
tively. The compound 9e transferred to isotropic liquid at 210 °C, on
slow cooling nematic to smectic phase transition was observed at
176 °C. Similarly, compound 9f become isotropic liquid at 202 °C, The
early growing stage of SmC phase at 197 °C viewed at 100 × magnifica-
tions (Fig. 2c) and Fig. 2d represents fully grown textures at 181 °C
viewed at 200 × magnifications. The dark brash in the smectic phase re-
gion appears at angles with respect to layer normal revealed the
synclinic smectic C phase. Using POM the calculated tilt angle of mole-
cule with respect to the layer normal is nearly 45°, which is in good
agreement with XRD results, discussed later. The polarization measure-
ment using triangular wave voltage technique determines that absence
of spontaneous polarization in these layers. Therefore, smectic C phase
observed for the compounds 9e–9f represents calamitic smectic C
type phase due to large bent angles in these molecules.
3. Mesomorphic properties
The thermal behaviour of all the mesogenic compounds was also in-
vestigated with DSC measurements at heating and cooling scan rate of
10 °C min−1 under nitrogen atmosphere. The phase transition temper-
atures obtained in DSC agree very well with POM observation. The com-
pounds 9b–9d exhibit exclusively enantiotropic nematic phase over
wide temperature. These compounds display two types of endothermic
transition from crystal to nematic phase at lower temperature and ne-
matic to isotropic transition at higher temperature as shown in
Table 1. However, compound 9e–9f shows an additional transition in
between these two transitions on heating and cooling scan, which con-
firms the presence of enantiotropic smectic C phase between the ne-
matic and crystal phases. Representative DSC thermographs of 9e are
presented in Fig. 3.
The graphical representation of thermal data is presented in Fig. 4
where Y axis represents transition temperature and X axis presents
compound 9a–9f. As can be seen, both crystalline state to nematic
phase and nematic–isotropic (N–I) temperatures exhibit a smooth fall-
ing tendency with increasing number of carbon atoms in the terminal
alkoxy chain compounds 9a–9f. Compound 9e–9f display increasing
smectic C phase range with increasing length of terminal alkyl chain
and decreasing nematic phase. This decrease in melting and clearing
temperature could be due to the lowering the van der Walls interactions
between aromatic cores and higher degree of flexibility of the terminal
chains.
The thermotropic mesophase behaviour of all novel compounds was
primarily investigated by polarising optical microscopy (POM). The
exact temperature of phase transition and associated enthalpy values
were determined by differential scanning calorimetry (DSC) and are
summarised in Table 1. The onset temperatures are given in °C and
the numbers in parentheses indicate the transition enthalpy (ΔH) in
kJ mol−1
.
The Schiff base containing three-ring compounds 8a and 8b did not
show any liquid crystalline properties and was not studied further.
Lower homologues of the series 9a–9f exhibit exclusively the nematic
phase with wide temperature range, while compounds 9e and 9f with
alkoxy dodecane and tetradecane chain display enantiotropic nematic
phase at higher temperature, followed by appearance of smectic C
phase at lower temperature. All the mesogenic compounds when ob-
served under cross polarisers upon cooling from isotropic melt, display
characteristic defect textures with two- and four-point brushes for ne-
matic mesophase (Fig. 2). The compound 9a on heating melt at 176 °C
and become isotropic liquid at 295 °C. Fig. 2a represents early growing
nematic droplets observed on cooling from isotropic liquid at 291 °C.
Typical schlieren textures were photographed at 280 °C on further
cooling from the isotropic melt as shown in Fig. 2b. Similar nematic
Table 1
Phase transition temperature (onset in DSC, °C, heating scan) and enthalpies (kJ mol−1, in
parentheses) of Schiff base EDOT derivatives 8a–8b and 9a–9f.
Cr: crystalline phase; N: nematic phase; SmC: smectic C phase; I: isotropic phase. * Phase
transition temperature observed in POM.
4. Thermogravimetric analysis
Phase transition
The thermal stability of all the liquid crystalline compounds was
checked using TGA 4000 thermogravimetric analysis instrument. All
the samples 9a–9f were subject to heat scan of 10 °C min−1 under a ni-
trogen atmosphere. The solid samples exhibit no weight loss in the tem-
perature range 310–340 °C. All the compounds initiated weight loss at
340–360 °C and whole process was completed at about 530 °C as
shown in Fig. 5. The decomposition temperature in these compounds
is much higher than the isotropic temperature. It revealed that all the
mesogenic derivatives possess good thermal stability.
Compound
(onset (°C) [ΔH (kJ mol−1)])
8a
8b
9a
9b
9c
9d
9e
9f
Cr 149.7 [33.1] I
Cr 129.4 [35.4] I
Cr 176 N 295 I*
Cr 163.7 [26.5] N 273.1 [2.0] I
Cr1 158.8 [2.3] Cr2 166.2 [18.4] N 245.3 [1.2] I
Cr1 159.2 [4.7] Cr2 175.2 [42.5] N 229.7 [1.7] I
Cr1 143.2 [1.7] Cr2 169.0 [18.5] SmC 176.3 [0.3] N 209.8 [0.9] I
Cr1 139.6 [1.4] Cr2 165.8 [14.7] SmC 198.3 [1.6] N 201.0 [1.3] I
Please cite this article as: A. Gowda, et al., Synthesis and mesomorphic properties of novel Schiff base liquid crystalline EDOT derivatives, J. Mol.
Liq. (2016), http://dx.doi.org/10.1016/j.molliq.2016.11.010

4
A. Gowda et al. / Journal of Molecular Liquids xxx (2016) xxx–xxx
Fig. 2. Polarising optical microscopy textures, for compound 9a: (a) nematic droplets observed during the early growing stage after cooling from the isotropic liquid at 291 °C, viewed at
100× magnifications, (b) growing of nematic texture on further cooling to 282 °C, viewed at 200× magnifications, for compound 9f: (c) early growing stage of SmC phase at 197 °C, viewed
at 100× magnification, (d) SmC texture at 181 °C, viewed at 200× magnification. The smectic C phase was observed in a 9 μm polyimide-coated LC cell for planar alignment of the sample
and viewed through cross-polariser on cooling from nematic phase.
5. X-ray scattering measurements
4.76 Å indicates a fluid-like correlation of the molecules in the layers.
The layer spacing of 46.95 Å in the smectic C phase is smaller than the
molecular length of 64.57 Å, indicating the tilted organisation of the
molecules in the layers. The tilt angle estimated from the layer spacing
and the molecular length is found to be about 45° at 182 °C, which en-
dorse with tilt angle measured using POM observations in the smectic
C phase.
The mesophase structures of novel Schiff base BC LCs were further
confirmed by X-ray diffraction (XRD) studies of unoriented samples
filled in Lindemann capillaries. The XRD pattern observed was for the
compounds 9c–9f on both heating and cooling scans. The XRD of com-
pounds 9a–9d could not be taken due to their very high isotropic tem-
perature. A representative and typical diffraction pattern obtained for
compound 9f at 201 °C in the nematic phase and at 183 °C for the smec-
tic C phase are shown in Fig. 6a and b, respectively. The XRD pattern of
compound 9f at 201 °C shows a diffuse peak at a small angle region and
a diffuse wide-angle maxima at d = 4.62 Å typical of the nematic phase
(Fig. 6a). The XRD pattern at 183 °C in the smectic C phase region is
shown in Fig. 6b. Two sharp reflections in the small angle regime with
d-spacings 46.95 Å and 23.52 Å were observed. These peaks in the
small-angle region are in the ratio of 1:2 of wave number indicating
the lamellar smectic-like packing of the molecules in the layers with
layer spacing as 46.95 Å. The diffuse peak at wide angle region at
6. Raman spectroscopy
The structure of the novel banana liquid crystals was further
examined by Raman spectroscopy. Raman spectra were recorded with
Horiba Jobin Yvon T6400 Micro Raman using a He–Ne Laser operating
at λ = 632.8 nm. The laser power at 1.8 mW was kept constant
throughout measurements. Spectral data were obtained at an optical
resolution of 50× objective lens and accumulated at 10 s to obtain
data with a sufficiently high signal-to-noise ratio. All solid samples
12
300
Cr to N (9a-9d) or Cr to SmC (9e, 9f)
SmC phase
Nematic phase
11
10
9
Heating scan
Crystal
SmC to N
280
N to isotropic phase
Isotropic
Isotropic
260
240
220
8
7
Nematic phase
200
6
Cooling scan
180
SmC phase
160
5
Crystal
140
140
160
180
200
C)
220
240
9a
9b
9c
9d
9e
9f
Temperature
(
Compounds
Fig. 3. DSC thermograms obtained for the compound 9e derivative showing phase
transitions on heating and cooling cycles at a scan rate of 10 °C min−1
.
Fig. 4. Graphical presentation of the thermal behaviour of compounds 9a–9f.
Please cite this article as: A. Gowda, et al., Synthesis and mesomorphic properties of novel Schiff base liquid crystalline EDOT derivatives, J. Mol.
Liq. (2016), http://dx.doi.org/10.1016/j.molliq.2016.11.010

A. Gowda et al. / Journal of Molecular Liquids xxx (2016) xxx–xxx
5
70000
1585
9a
1334
9a
9b
9c
9d
9e
9f
100
80
60
40
20
0
9b
60000
9c
1458
1492
9d
1207
50000
9e
1160
9f
40000
960
440
30000
1720
20000
10000
500
1000
Raman shift (cm
1500
2000
-
1
100
200
300
400
500
600
700
800
)
Temperature ( C)
Fig. 7. Raman spectrum of mesogenic compounds 9a–9f over the range 450–2000 cm−1 at
298 K.
Fig. 5. Thermogravimetric analysis of compounds 9a–9f, respectively.
7. Experimental section
were placed in a normal glass slide and covered with a coverslip. The
Raman shift recorded in the range between 400 and 2000 cm−1 at
room temperature. The Raman spectra (Fig. 7) clearly indicated the typ-
ical Raman bands at lower regions at 443–1350 cm−1 which corre-
sponding to aliphatic chains and aromatic rings. The intense peaks at
140–1600 cm−1 corresponds to EDOT containing a heteroaromatic
ring. The prominent peaks at 1712 cm−1 are responsible for ester
linking groups in the mesogenic derivatives respectively.
7.1. General methods
All the chemicals and reagents were AR-grade quality and purchased
from Sigma-Aldrich. The solvents were dried and distilled using a stan-
dard protocol. The intermediate and final compounds were purified by
column chromatography using Acme make silica gel (100−200)
mesh and repeated recrystallisation from appropriate solvent system.
Spectral and elemental analysis confirmed the structural elucidation
and purity of all the compounds. Fourier transform infrared spectrosco-
py (FT-IR) spectra were recorded using Shimadzu – 8400; only major
peaks were reported in cm−1. Nuclear magnetic resonance spectrosco-
py (1H NMR and 13C NMR) were recorded on Bruker 500 MHz machine
using deuterated chloroform (CDCl3) as a solvent and chemical shifts
were recorded in parts per million (ppm) from tetramethylsilane as in-
ternal standard (CDCl3: 1H NMR: δ = 7.23; 13C NMR = 77.0). Elemental
analysis was carried out using Elementar Vario MICRO Select instru-
ment. The microscopic textures were recorded on a sample placed be-
tween ordinary glass slides using Olympus BX51 polarising optical
microscope (Olympus, Tokyo, Japan) in conjunction with Mettler
FP82HT hot stage and Mettler FP90 central processor. The phase transi-
tion temperature and associated enthalpies of the liquid crystalline
samples were determined by Perkin Elmer DSC 8000 coupled to a con-
trolled liquid nitrogen accessory (CLN 2) differential scanning calorime-
(a) 201 C
104
d = 4.62
Å
103
0
5
10
15
(degrees)
20
25
30
try instrument using 2–4 mg samples and a scan rate of 10 °C min−1
.
2
Further detail examination of liquid crystalline mesophase structure
was done by X-ray diffraction using Panalytical (Empyrean) Cu-Kα
(1.54 Å) X-ray diffractometer.
105
104
103
102
(b) 183 C
d
= 46.95 Å
1
7.2. General procedure for the synthesis of intermediates and final
compounds
All the compounds were synthesized by simple straight forward re-
action. The intermediate compound 3a was purchased from commercial
source.
d
= 23.52 Å
2
d = 4.76
Å
7.2.1. Synthesis of 1-nitro-4-(octadecyloxy) benzene (2b)
To a stirring solution of 4-nitrophenol 1 (1 g, 7.18 mmol) and anhy-
drous potassium carbonate (1.98 g, 14.37 mmol) in dry DMF (25 mL)
was added 1-bromooctadecane (2.4 g, 7.18 mmol). The reaction mix-
ture was refluxed for 8 h. After cooling to room temperature, ice cold
water was added under vigorous stirring and the solid was filtered off.
The crude compound was dried under high vacuum and recrystalliza-
tion from ethanol gives pure white crystals 2. Yield: 80%. IR (film)
0
5
10
15
20
25
30
2
degrees)
Fig. 6. XRD patterns of compound 9f: (a) nematic phase at 201 °C; (b) smectic C phase at
183 °C.
υ ;
max: 2918, 2850, 1606, 1504, 1454, 1377, 1348 cm−1 1H NMR
Please cite this article as: A. Gowda, et al., Synthesis and mesomorphic properties of novel Schiff base liquid crystalline EDOT derivatives, J. Mol.
Liq. (2016), http://dx.doi.org/10.1016/j.molliq.2016.11.010

6
A. Gowda et al. / Journal of Molecular Liquids xxx (2016) xxx–xxx
(500 MHz, CDCl3): δ = 8.19 (d, 2H, J = 8.5 Hz), 6.93 (d, 2H, J = 8 Hz),
4.04 (t, 2H, J = 6 Hz), 1.84–1.79 (m, 2H), 1.47–1.43 (m, 2H), 1.35–
1.25 (m, 28H), 0.89 ppm (t, 3H, J = 6.5 Hz); 13C NMR (500 MHz,
CDCl3): δ = 164.26, 141.32, 125.92, 114.40, 68.91, 31.93, 29.70, 29.67,
29.65, 29.57, 29.53, 29.37, 29.31, 28.97, 25.91, 22.70, 14.12 ppm; ele-
mental analysis: C24H41NO3; calculated (%): C 73.61, H 10.54, N 3.57;
found: C 73.72, H 10.61, N 3.66.
14.10 ppm; elemental analysis: C21H25NO5; calculated (%): C 67.90, H
6.77, N 3.76; found: C 67.95, H 6.84, N 3.81.
4d. IR (film) υmax: 2920, 2910, 2852, 1732, 1608, 1525, 1456, 1377,
1350 cm−1; 1H NMR (500 MHz, CDCl3): δ = 8.32 (d, 2H, J = 8 Hz), 8.13
(d, 2H, J = 8 Hz), 7.40 (d, 2H, J = 8 Hz), 6.99 (d, 2H, J = 8 Hz), 4.05
(t, 2H, J = 6.5 Hz), 1.82 (br, 2H), 1.47 (br, 2H), 1.37–1.28 (m, 12H),
0.88 ppm (t, 3H, J = 6.5 Hz); 13C NMR (500 MHz, CDCl3): δ = 164.09,
163.97, 156, 145.28, 132.52, 125.22, 122.67, 120.44, 114.54, 68.47,
31.89, 29.55, 29.35, 29.31, 29.07, 25.97, 22.68, 14.10 ppm; elemental
analysis: C23H29NO5; calculated (%): C 69.09, H 7.31, N 3.50; found:
C 69.16, H 7.36, N 3.54.
7.2.2. Synthesis of 4-(octadecyloxy) aniline (3b)
1-Nitro-4-(octadecyloxy)benzene 2b (0.5 g, 1.38 mmol) and 10%
palladium on charcoal (100 mg) was placed in single necked round bot-
tom flask along with 20 mL mixture of ethanol: THF (1:1) solvent. The
reaction mixture was stirred at room temperature in presence of hydro-
gen atmosphere for 6 h. After completion, the reaction mixture was fil-
tered through celite pad and filtrate was concentrated under reduced
pressure to give crude product. In order to remove trace amount of pal-
ladium content, the crude product was passed through neutral alumina
and recrystallization from n-heptane affords white colour solid
3b. Yield: 85%. IR (film) υmax: 3387, 3169, 2953, 2922, 2850, 1592,
4e. IR (film) υmax: 2926, 2918, 2852, 1732, 1609, 1527, 1454, 1377,
1351 cm−1 1H NMR (500 MHz, CDCl3): δ = 8.32 (d, 2H, J = 7.5 Hz),
;
8.13 (d, 2H, J = 7 Hz), 7.40 (d, 2H, J = 7.5 Hz), 6.99 (d, 2H, J = 7 Hz),
4.05 (t, 2H, J = 6.5 Hz), 1.82 (br, 2H), 1.47 (br, 2H), 1.36–1.27
(m, 16H), 0.88 ppm (t, 3H, J = 6.5 Hz); 13C NMR (500 MHz, CDCl3):
δ = 164.09, 163.97, 156, 145.29, 132.52, 125.22, 122.67, 120.44,
114.54, 68.47, 31.92, 29.65, 29.59, 29.55, 29.35, 29.07, 25.97, 22.69,
14.11 ppm; elemental analysis: C25H33NO5; calculated (%): C 70.17, H
7.77, N 3.27; found: C 70.10, H 7.82, N 3.35.
1518, 1462, 1377 cm−1 1H NMR (500 MHz, CDCl3): δ = 6.73 (d, 2H,
;
J = 8 Hz), 6.63 (d, 2H, J = 8 Hz), 3.87 (t, 2H, J = 6.5 Hz), 3.40
(br, 2H), 1.76–1.70 (m, 2H), 1.43–1.39 (m, 2H), 1.29–1.25 (m, 27H),
0.88 ppm (t, 3H, J = 6.5 Hz); 13C NMR (500 MHz, CDCl3): δ = 152.38,
139.78, 116.43, 115.69, 68.74, 31.93, 29.70, 29.67, 29.61, 29.60, 29.44,
29.37, 26.08, 22.70, 14.12 ppm; elemental analysis: C24H43NO; calculat-
ed (%): C 79.71, H 11.97, N 3.87 found: C 79.78, H 12.01, N 3.91.
4f. IR (film) υmax: 2956, 2914, 2852, 1732, 1608, 1525, 1454, 1377,
1350 cm−1 1H NMR (500 MHz, CDCl3): δ = 8.32 (d, 2H, J = 8.5 Hz),
;
8.13 (d, 2H, J = 8.5 Hz), 7.40 (d, 2H, J = 8.5 Hz), 6.99 (d, 2H, J =
8 Hz), 4.05 (t, 2H, J = 6.5 Hz), 1.82 (br, 2H), 1.47 (br, 2H), 1.36–1.26
(m, 20H), 0.88 ppm (t, 3H, J = 6.5 Hz); 13C NMR (500 MHz, CDCl3):
δ = 164.10, 163.97, 156.21, 145.29, 132.52, 125.22, 122.67, 114.54,
68.47, 31.93, 29.69, 29.65, 29.58, 29.55, 29.35, 29.07, 25.97, 22.69,
14.11 ppm; elemental analysis: C24H43NO; calculated (%): C 71.18, H
8.17, N 3.07; found: C 71.23, H 8.24, N 3.12.
7.2.3. Synthesis of 4-nitrophenyl-4-alkoxybenzoate (4a–4f)
In a two neck-flask containing 4-nitrophenol 1 (2 g, 14.37 mmol), 4-
alkoxybenzoic acid (14.37 mmol) and catalytic amount of 4-
dimethylaminopyridine (DMAP) (0.17 g, 1.43 mmol) was added dry di-
chloromethane (DCM) solvent (50 mL) under argon at room tempera-
ture. After stirring for 10 min, N,N′-dicyclohexylcarbodiimide (DCC)
(4.42 g, 21.56 mmol) in 15 mL of dry DCM was added. The resulting
mixture was stirred at room temperature for 24 h. At the end of reaction,
the precipitated N,N-dicyclohexylurea (DCU) was removed by filtration
and the filtrate was washed with 5% KOH solution and followed by
washing with excess of distilled water and then extracted with DCM
(3 × 75 mL). The combined extracts were dried over sodium sulphate
(Na2SO4) and concentrate under vacuum. Recrystallisation of crude
compound with isopropyl alcohol affords yellow colour solid (4a–4f).
Yield: 55–65%.
7.2.4. Synthesis of 4-aminophenyl-4-alkoxybenzoate (5a–5f)
Palladium on carbon (10% Pd/C) (0.1 g) was added to a vigorous stir-
ring solution of 5 mL mixture of THF: EtOH (1:1) solvent containing
nitro compound 4a–4f (0.2 g). The reaction was stirring under hydro-
gen atmosphere at room temperature for 8 h. After completion of reac-
tion, the resulting reaction mixture was filtered through celite pad and
filtrate was concentrated completely under vacuum. In order to remove
trace palladium content, the residue was passed through column
chromatography using neutral alumina (n-hexane/ethyl acetate 1:1).
Recrystallisation of crude compound with n-heptane gives pure white
solid 5a–5f in about 90% yield.
5a. IR (film) υmax: 3452, 3365, 2955, 2924, 2854, 1712, 1606, 1514,
4a. IR (film) υmax: 2922, 2914, 2854, 1735, 1606, 1529, 1454, 1377,
1454, 1377 cm−1 1H NMR (500 MHz, CDCl3): δ = 8.11 (d, 2H, J =
;
1348 cm−1
;
1H NMR (500 MHz, CDCl3): δ = 8.31 (d, 2H, J = 8.5 Hz),
8.5 Hz), 6.95 (m, 4H), 6.70 (d, 2H, J = 8 Hz), 4.04 (t, 2H, J = 6.5 Hz),
3.64 (s, 2H), 1.80 (br, 2H), 1.51 (m, 2H), 0.98 ppm (t, 3H, J = 6.5 Hz);
13C NMR (500 MHz, CDCl3): δ = 165.49, 163.38, 144.06, 143.27,
132.16, 122.38, 121.89, 115.70, 114.22, 67.98, 31.15, 19.20, 13.81 ppm;
elemental analysis: C17H19NO3; Calculated (%): C 71.55, H 6.70,
N 4.90; found: C 71.52, H 6.76, N 4.94.
8.13 (d, 2H, J = 8 Hz), 7.40 (d, 2H, J = 8.5 Hz), 6.99 (d, 2H, J =
8.5 Hz), 4.06 (t, 2H, J = 6.5 Hz), 1.82 (br, 2H), 1.51 (br, 2H), 1.0 ppm
(t, 3H, J = 7 Hz); 13C NMR (500 MHz, CDCl3): δ = 164.09, 163.97,
156, 145.28, 132.53, 125.22, 122.67, 120.44, 114.54, 68.14, 31.11,
19.19, 13.80 ppm; elemental analysis: C17H17NO5; calculated (%): C
64.75, H 5.42, N 4.44; found: C 64.81, H 5.49, N 4.52.
5b. IR (film) υmax: 3402, 3294, 2953, 2922, 2854, 1724, 1606, 1514,
4b. IR (film) υmax: 2920, 2912, 2854, 1743, 1606, 1514, 1454, 1377,
1454, 1377 cm−1 1H NMR (500 MHz, CDCl3): δ = 8.11 (d, 2H, J =
;
1344 cm−1
;
1H NMR (500 MHz, CDCl3): δ = 8.31 (d, 2H, J = 8.5 Hz),
8.5 Hz), 6.96 (m, 4H), 6.70 (d, 2H, J = 8 Hz), 4.03 (t, 2H, J = 6.5 Hz),
3.64 (s, 2H), 1.84–1.81 (m, 2H), 1.49–1.46 (m, 2H), 1.35 (br, 4H),
0.91 ppm (t, 3H, J = 6.5 Hz); 13C NMR (500 MHz, CDCl3): δ = 165.52,
163.38, 144.07, 143.25, 132.18, 122.29, 121.84, 115.71, 114.22, 68.30,
31.56, 29.08, 25.67, 22.60, 14.04 ppm; elemental analysis: C19H23NO3;
Calculated (%): C 72.81, H 7.39, N 4.46; found: C 72.86, N 7.46, N 4.51.
5c. IR (film) υmax: 3464, 3373, 2955, 2920, 2852, 1714, 1604, 1510,
1456, 1375 cm−1; 1H NMR (500 MHz, CDCl3): δ = 8.11 (d, 2H, J = 8 Hz),
6.96 (m, 4H), 6.70 (d, 2H, J = 8 Hz), 4.03 (t, 2H, J = 6.5 Hz), 3.64 (s, 2H),
1.82–1.80 (m, 2H), 1.48–1.44 (m, 2H), 1.34–1.29 (m, 8H), 0.90 ppm
(t, 3H, J = 6.5 Hz); 13C NMR (500 MHz, CDCl3): δ = 1.65.51, 163.38,
144.07, 143.26, 132.17, 122.38, 121.86, 115.70, 114.23, 68.31, 31.81,
29.33, 29.22, 29.11, 25.99, 22.66, 14.10 ppm; elemental analysis:
8.13 (d, 2H, J = 8 Hz), 7.40 (d, 2H, J = 8.5 Hz), 6.99 (d, 2H, J = 8 Hz),
4.058 (d, 2H, J = 6.5 Hz), 1.84–1.81 (m, 2H), 1.49–1.47 (m, 2H), 1.36
(br, 4H), 0.92 ppm (t, 3H, J = 6 Hz); 13C NMR (500 MHz, CDCl3): δ =
164.08, 163.98, 155.99, 145.27, 132.52, 125.22, 122.68, 120.41, 114.53,
68.46, 31.54, 29.04, 25.65, 22.59, 14.02 ppm; elemental analysis:
C
19H21NO5; calculated (%): C 66.46, H 6.15, N 4.07; found: C 66.55, H
6.23, N 4.15.
4c. IR (film) υmax: 2955, 2920, 2910, 1732, 1608, 1525, 1456, 1377,
1350 cm−1 1H NMR (500 MHz, CDCl3): δ = 8.31 (d, 2H, J = 8.5 Hz),
;
8.13 (d, 2H, J = 8 Hz), 7.40 (d, 2H, J = 8 Hz), 6.98 (d, 2H, J = 8 Hz),
4.05 (t, 2H, J = 6.5 Hz), 1.85–1.80 (m, 2H), 1.49–1.45 (m, 2H), 1.37–
1.32 (m, 8H), 0.88 ppm (t, 3H, J = 6.5 Hz); 13C NMR (500 MHz,
CDCl3): δ = 164.09, 163.97, 156, 145.28, 132.52, 125.22, 122.67,
120.44, 114.54, 68.47, 31.89, 29.55, 29.35, 29.31, 29.07, 25.97, 22.68,
C
21H27NO3; calculated (%): C 73.87, H 7.96, N 4.10; found: C 73.91,
H 8.01, N 4.15.
Please cite this article as: A. Gowda, et al., Synthesis and mesomorphic properties of novel Schiff base liquid crystalline EDOT derivatives, J. Mol.
Liq. (2016), http://dx.doi.org/10.1016/j.molliq.2016.11.010

A. Gowda et al. / Journal of Molecular Liquids xxx (2016) xxx–xxx
7
5d. IR (film) υmax: 3406, 3302, 2920, 2852, 1714, 1606, 1510, 1456,
1377 cm−1; 1H NMR (500 MHz, CDCl3): δ = 8.11 (d, 2H, J = 8 Hz), 6.96
(m, 4H), 6.70 (d, 2H, J = 7.5 Hz), 4.03 (t, 2H, J = 6.5 Hz), 3.64 (s, 2H),
1.81 (br, 2H), 1.46 (br, 2H), 1.36–1.28 (m, 12H), 0.88 ppm (t, 3H, J =
6.5 Hz); 13C NMR (500 MHz, CDCl3): δ = 165.49, 163.38, 144.07,
143.28, 132.16, 122.38, 121.89, 115.69, 114.23, 68.31, 31.89, 29.55,
29.36, 29.31, 29.11, 25.98, 22.68, 14.10 ppm; elemental analysis:
C23H31NO3; calculated (%): C 74.76, H 8.44, N 3.78; Found: C 75.01,
H 8.49, N 3.83.
C 73.01, H 6.99, N 6.07, S 6.94; found: C 73.07, H 7.04, N 6.11, S 6.97.
1H NMR and 13C NMR spectrum showed in Supplementary Information
Fig. S2
8b. IR (film) υmax: 2953, 2918, 2852, 1614, 1516, 1462, 1377 cm−1
;
1H NMR (500 MHz, CDCl3): δ = 8.61 (s, 2H), 7.17 (d, 2H, J = 8 Hz), 6.89
(d, 2H, J = 8 Hz), 4.36 (s, 4H), 3.96 (t, 4H, J = 6.5 Hz), 1.79–1.75 (m, 4H),
1.46–1.42 (m, 4H), 1.35–0.25 (m, 54H), 0.89 ppm (br, 6H); 13C
NMR (500 MHz, CDCl3): 158.04, 146.71, 122.52, 114.93, 68.30, 65.08,
31.93, 29.70, 29.67, 29.61, 29.59, 29.42, 29.37, 29.31, 26.06, 22.70,
14.12 ppm; elemental analysis: C56H88N2O4S; calculated (%): C 75.96,
H 10.0, N 3.16, S 3.61; found: C 75.99, H 10.04, N 3.19, S 3.63. 1H NMR
and 13C NMR spectrum showed in Supplementary Information Fig. S3
9a. IR (film) υmax: 2918, 2906, 2852, 1716, 1606, 1508, 1454,
1377 cm−1; 1H NMR (500 MHz, CDCl3): δ = 8.63 (s, 2H), 8.14 (d, 4H,
J = 8.5 Hz), 7.29 (d, 4H, J = 8 Hz), 7.21 (d, 4H, J = 7.5 Hz), 6.97
(d, 4H, J = 8.5 Hz), 4.39 (s, 4H), 4.05 (t, 4H, J = 6.5 Hz), 1.82–1.80
(m, 4H), 1.51 (br, 4H), 1.0 ppm (t, 6H, J = 7.5 Hz); 13C NMR
(500 MHz, CDCl3): 165.03, 163.58, 149.42, 148.97, 148.93, 143.97,
132.29, 122.39, 122.16, 121.53, 121.05, 114.31, 68.02, 65.13, 31.15,
19.20, 13.82 ppm. Elemental analysis: C42H40N2O8S; calculated (%):
C 68.83, H 5.49, N 3.82, S 4.36; found: C 68.87, H 5.54, N 3.84, S 4.39.
1H NMR and 13C NMR spectrum showed in Supplementary Information
Fig. S4
5e. IR (film) υmax: 3458, 3369, 2928, 2912, 2850, 1714, 1604, 1514,
1454, 1377 cm−1 1H NMR (500 MHz, CDCl3): δ = 8.11 (d, 2H, J =
;
7.5 Hz), 6.96 (m, 4H), 6.70 (d, 2H, J = 7 Hz), 4.03 (t, 2H, J = 6.5 Hz),
3.64 (s, 2H), 1.81 (br, 2H), 1.46 (br, 2H), 1.35–1.27 (m, 16H),
0.88 ppm (t, 3H, J = 6.5 Hz); 13C NMR (500 MHz, CDCl3): δ = 165.50,
163.39, 144.07, 143.27, 132.17, 122.38, 121.88, 115.70, 114.23, 68.32,
31.93, 29.66, 29.64, 29.59, 29.56, 29.36, 29.12, 25.99, 22.69,
14.12 ppm; elemental analysis: C25H35NO3; calculated (%): C 75.53,
H 8.86, N 3.52; found: C 75.59, H 8.93, N 3.57.
5 f. IR (film) υmax: 3423, 3331, 2908, 2897, 2872, 1730, 1606, 1512,
1454, 1377 cm−1; 1H NMR (500 MHz, CDCl3): δ = 8.11 (d, 2H, J = 8 Hz),
6.96 (m, 4H), 6.70 (d, 2H, J = 8 Hz), 4.03 (t, 2H, J = 6.5 Hz), 3.64 (s, 2H),
1.81 (br, 2H), 1.46 (br, 2H), 1.35–1.26 (m, 19H), 0.88 ppm (t, 3H, J =
6.5 Hz); 13C NMR (500 MHz, CDCl3): δ = 165.49, 163.39, 144.06,
143.28, 132.16, 122.38, 115.69, 114.23, 68.31, 31.93, 29.69, 29.65,
29.59, 29.55, 29.36, 29.11, 25.99, 22.69, 14.11 ppm; elemental analysis:
9b. IR (film) υmax: 2928, 2854, 1722, 1604, 1510, 1454, 1377 cm−1
;
1H NMR (500 MHz, CDCl3): δ = 8.63 (s, 2H), 8.14 (d, 4H, J = 8 Hz), 7.29
(d, 4H, J = 8.5 Hz), 7.21 (d, 4H, J = 8 Hz), 6.97 (d, 4H, J = 8.5 Hz), 4.39
(s, 4H), 4.05 (t, 4H, J = 6.5 Hz), 1.84–1.81 (m, 4H), 1.48 (br, 4H), 1.36
(br, 8H), 0.92 ppm (br, 6H); 13C NMR (500 MHz, CDCl3): 165.02,
163.58, 149.42, 148.96, 143.97, 132.29, 122.38, 122.16, 114.32, 68.35,
65.13, 31.55, 29.08, 25.67, 22.59, 14.02 pm; elemental analysis:
C
27H39NO3; calculated (%): C 76.19, H 9.22, N 3.28; found: C 76.24,
H 9.28, N 3.34.
7.2.5. Synthesis of 2,3-dihydrothieno[3,4-b][1,4]dioxine-5,7-dicarbaldehyde
(7)
1.6 M solution of n-butyl lithium (n-BuLi) (29 mL) was added
dropwise to a stirring solution of EDOT (3 g, 0.021 mol) in dry THF
(50 mL) at −78 °C under N2 atmosphere. After addition, the reaction
mixture was slowly raised to temperature to 0 °C and stirred same at
temperature for 30 min. Again the reaction mixture was recooled to
−78 °C and quenched with dry DMF (3.5 mL). The reaction mixture
was stirred at room temperature for 2 h. The resulting reaction mixture
was poured in to crushed ice containing HCl (pH = 4). The brown col-
our solid precipitated out and filtered off, washed with excess of
water and dried in vacuo. Recrystallisation of crude product with cold
methanol gives brown colour solid 7. Yield: 75%. IR (film) υmax: 2955,
C46H48N2O8S; calculated (%): C 70.03, H 9.95, N 3.54, S 4.05; found: C
70.09, H 9.99, N 3.57, S 4.07.1H NMR and 13C NMR spectrum showed
in Supplementary Information Fig. S5
9c. IR (film) υmax: 2955, 2924, 2854, 1716, 1604, 1508, 1456,
1363 cm−1; 1H NMR (500 MHz, CDCl3): δ = 8.63 (s, 2H), 8.14 (d, 4H,
J = 8 Hz), 7.29 (d, 4H, J = 8 Hz), 7.21 (d, 4H, J = 7.5 Hz), 6.97 (d, 4H,
J = 8 Hz), 4.39 (s, 4H), 4.04 (t, 4H, J = 6.5 Hz), 1.83–1.81 (m, 4H),
1.48–1.46 (m, 4H), 1.34–1.30 (m, 16H), 0.89 ppm (m, 6H); 13C NMR
(500 MHz, CDCl3): 165.03, 163.57, 149.41, 148.97, 148.93, 143.98,
132.29, 122.39, 122.17, 121.51, 121.04, 114.31, 68.35, 65.13, 31.81,
29.34, 29.23, 29.11, 26, 22.66, 14.11 ppm; elemental analysis:
2924, 2854, 1666, 1614, 1504, 1454, 1375 cm−1
;
1H NMR (500 MHz,
C50H56N2O8S; calculated (%): C 71.06, H 6.67, N 3.31, S 3.78; found: C
CDCl3): δ = 10.04 (s, 2H), 4.46 (s, 4H); 13C NMR (500 MHz, CDCl3):
180.94, 147.15, 124.16, 65.15; elemental analysis: C8H6O4S; calculated
(%): C 48.48, H 3.04, S 16.14; found: C 48.51, H 3.06, S 16.14. 1H NMR
and 13C NMR spectrum showed in Supplementary Information Fig. S1.
71.10, H 6.69, N 3.33, S 3.80. 1H NMR and 13C NMR spectrum showed
in Supplementary Information Fig. S6
9d. IR (film) υmax: 2953, 2922, 2852, 1714, 1606, 1508, 1454,
1365 cm−1; 1H NMR (500 MHz, CDCl3): δ = 8.63 (s, 2H), 8.14 (d, 4H,
J = 8 Hz), 7.29 (d, 4H, J = 8 Hz), 7.21 (d, 4H, J = 7.5 Hz), 6.97 (d, 4H,
J = 8 Hz), 4.39 (s, 4H), 4.04 (t, 4H, J = 6.5 Hz), 1.83–1.81 (m, 4H),
1.49–1.46 (m, 4H ), 1.37–1.28 (m, 24H), 0.90 ppm (br, 6H); 13C NMR
(500 MHz, CDCl3): 165.01, 163.58, 149.43, 148.94, 143.97, 132.29,
122.38, 122.15, 121.54, 121.06, 114.33, 68.36, 65.13, 31.90, 29.56,
29.36, 29.31, 29.11, 25.99, 22.68, 14.11 ppm; elemental analysis:
7.2.6. Synthesis of final compounds 8a–8b and 9a–9f
The condensation reaction between 4-aminophenyl-4-
alkoxybenzoate with EDOT-2.5-dialdehyde
mesogenic derivatives. The general method described as follows.
3,4-Ethylenedioxythiophene-2,5-dicarboxyaldehyde (0.2 g,
7 gives Schiff base
7
0.86 mmol) and 4-methoxyaniline 3a or 4-amino 4-alkoxybenzoate
3b or 4-aminophenyl 4-alkoxybenzoate 5a–5f (3.47 mmol) was dis-
solved in 20 mL of absolute ethanol and few drops of glacial acetic
acid was added. The reaction mixture was refluxed for 4 h in presence
on nitrogen atmosphere. After completion of reaction, the solid was fil-
tered off and crude solid was purified by repeated recrystallization from
isopropyl alcohol gives pure yellow colored compounds 8a–8b and 9a–
9f. Yield: 75–85%.
C54H64N2O8S; calculated (%): C 71.97, H 7.15, N 3.10, S 3.55; found: C
72.01, H 7.18, N 3.13, S 3.56. 1H NMR and 13C NMR spectrum showed
in Supplementary Information Fig. S7
9e. IR (film) υmax: 2924, 2852, 1730, 1604, 1510, 1454, 1363 cm−1
;
1H NMR (500 MHz, CDCl3): δ = 8.63 (s, 2H), 8.14 (d, 4H, J = 8 Hz), 7.29
(d, 4H, J = 8 Hz), 7.21 (d, 4H, J = 8 Hz), 6.97 (d, 4H, J = 8.5 Hz), 4.39
(S, 4H), 4.04 (t, 4H, J = 6 Hz), 1.83–1.80 (m, 4H), 1.47 (br, 4H), 1.36–
1.27 (m, 32H), 0.88 ppm (t, 6H, J = 6 Hz); 13C NMR (500 MHz,
CDCl3): 165.01, 163.58, 149.43, 148.94, 143.96, 132.28, 122.38, 122.15,
121.55, 121.07, 114.33, 68.36, 65.13, 31.92, 29.66, 29.63, 29.59, 29.56,
29.36, 29.35, 29.11, 25.99, 22.69, 14.11 ppm; elemental analysis:
8a. IR (film) υmax: 2953, 2918, 2852, 1614, 1516, 1462, 1377 cm−1
;
1H NMR (500 MHz, CDCl3): δ = 8.61 (s, 2H), 7.16 (m, 8H), 4.36 (s, 4H),
2.61 (t, 4H, J = 7 Hz), 1.62–1.59 (m, 4H), 1.38–1.34 (m, 4H), 0.94 ppm
(t, 3H, J = 6.5 Hz); 13C NMR (500 MHz, CDCl3): 149.01, 148.11,
143.61, 141.20, 129.07, 121.16, 121.01, 65.09, 35.23, 33.67,
22.34, 13.96 ppm. Elemental analysis: C28H32N2O2S; calculated (%):
C
58H72N2O8S; calculated (%): C 72.77, H 7.57, N 2.92, S 3.34; found:
C 72.81, H 7.61, N 2.95, S 3.37. 1H NMR and 13C NMR spectrum showed
in Supplementary Information Fig. S8
Please cite this article as: A. Gowda, et al., Synthesis and mesomorphic properties of novel Schiff base liquid crystalline EDOT derivatives, J. Mol.
Liq. (2016), http://dx.doi.org/10.1016/j.molliq.2016.11.010

8
A. Gowda et al. / Journal of Molecular Liquids xxx (2016) xxx–xxx
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9f. IR (film) υmax: 2955, 2924, 2854, 1732, 1604, 1510, 1454,
J. Mater. Chem. 11 (2001) 2748–2758.
[8] A. Jakli, Liq. Cryst. Rev. 1 (2013) 65–82.
[9] V. Gortz, Liq. Cryst. Today 19 (2010) 37–48.
[10] W. Weissflog, H.N.S. Murthy, S. Diele, G. Pelzl, Phil. Trans. R. Soc. A 364 (2006)
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1377 cm−1; 1H NMR (500 MHz, CDCl3): δ = 8.63 (s, 2H), 8.14 (d, 4H,
J = 8 Hz), 7.29 (d, 4H, J = 7.5 Hz), 7.21 (d, 4H, J = 8 Hz), 6.97 (d, 4H,
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8. Conclusion
A new series of BC LCs bearing Schiff base derived from EDOT central
unit was synthesized and characterized. EDOT based three ring Schiff-
base compounds found to be non-mesogenic, while five ring Schiff
base compounds exhibit liquid crystalline phases. The bent angle of
five membered ring is 154°. The lower homologues compounds exhibit
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Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.molliq.2016.11.010.
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Please cite this article as: A. Gowda, et al., Synthesis and mesomorphic properties of novel Schiff base liquid crystalline EDOT derivatives, J. Mol.
Liq. (2016), http://dx.doi.org/10.1016/j.molliq.2016.11.010