On the supramolecular packing of bent-shaped molecules: The influence of the central bent-core on the liquid crystalline behaviour

Article abstract of DOI:10.1039/b9nj00230h

Two series of bent-shaped molecules have been synthesized and their supramolecular self-organization at variable temperature has been studied. The majority of these bent-compounds form liquid crystalline phases and the mesomorphic behaviour of them has be

Full text of DOI:10.1039/b9nj00230h

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On the supramolecular packing of bent-shaped molecules: the influence
of the central bent-core on the liquid crystalline behaviourw
´
Nelida Gimeno, Marıa Jose Clemente, Patricia Forcen, Jose Luis Serrano
and Maria Blanca Ros*
´
´
´
´
Received (in Montpellier, France) 1st June 2009, Accepted 27th July 2009
First published as an Advance Article on the web 20th August 2009
DOI: 10.1039/b9nj00230h
Two series of bent-shaped molecules have been synthesized and their supramolecular
self-organization at variable temperature has been studied. The majority of these bent-compounds
form liquid crystalline phases and the mesomorphic behaviour of them has been fully
characterized by polarised optical microscopy, calorimetry, X-ray diffraction and dielectric
techniques. A series of bis-4-n-tetradecyloxybenzoyloxybenzoates derived from naphthalene,
resulting in a change of the bending angle, have proved that when these cores bend around 1201,
a polar lamellar packing (SmCaPA) can be induced, whereas when the angle was around 601, an
orthogonal lamellar arrangement (SmA) that responded to an electric field, are found to occur.
Liquid-crystal order can also be achieved over a significant range of temperatures by
using appropriate bis-4,40-disubstituted phenylene derivatives (–Ar–X–Ar–). Groups such
as –CO–, SO– and –CH2– connecting the aromatic rings induce the SmCaPA phase while a
sulfide group (–S–) leads to columnar order. Further, the formation of isotropic textures as
chiral conglomerates or a field-induced phase transition have also been observed as unusual
properties of the self-organizations of these compounds.
In order to control the supramolecular packing of
Introduction
bent-shaped molecules an extensive range of structural
modifications have been made on the general structure of this
type of compounds, regarding the terminal chains, the lateral
moieties and the central bent core (see Fig. 1 and 2).
Since 1996, when Niori et al.1 reported for the first time on
self-organization of achiral bent-core molecules resulting in
new liquid crystalline phases (also known as banana-shaped
liquid crystals), a rising interest has grown on them, due
essentially to the unusual properties of these new materials
regarding both polarity and chirality.
The lateral cores have been widely modified. Both the nature
and sense of the links between the lateral aromatic rings have
been probed to be useful tools to control the molecular
arrangements.3a,e,5 Furthermore, the variation of the number
of lateral aromatic rings and the incorporation of substituents
in them (specially halides) have also become a very attractive
target for researchers.6 Concerning terminal chains, apart
from several structure–mesomorphic properties relationship
studies where the length of the terminal chains is modified
(namely alkyl or alkoxy chains with 2 up to 22 carbons),7
examples of terminal chains incorporating chiral centers,8
bulky silicon-containing groups,9 polymerizable moieties10 as
well as some polycatenar systems11 have been reported.
Finally, regarding the central core the modifications are
mainly related with the rigidity and the polarity of this moiety.
Typical mesomorphism of bent-shaped compounds has been
Because of the particular shape of these molecules, a
restricted rotation around the molecular long axis is generated
that gives rise to a macroscopic polarization in the smectic
layers or columns. Furthermore, in the tilted phases formed by
these bent-core molecules the combination of polar order and
director tilt leads to a chiral structure of the layers without the
presence of chiral molecules.2
The singularities of these self-organizing supramolecular
systems have attracted the attention from academics, and
several highlights and review papers have been published in
the last few years.3 Additionally their potential has also been
pointed out for applications in fields such as electrooptics and
nonlinear optics materials, where organic compounds have
provided exceptional contributions by appropriate molecular
design.4
´
´
Quımica Organica, Facultad de Ciencias, Instituto de Ciencia de
Materiales de Arago´n, Universidad de Zaragoza-CSIC, 50009
Zaragoza, Spain. E-mail: bros@unizar.es; Tel: +34 976762277
w Electronic supplementary information (ESI) available: 1: Graphical
comparison of imine vs. ester naphthalene series. 2: Conformations
and theoretical molecular lengths of N(2,3) and N(2,7). 3: Switching
curves of N(2,7). 4: DSC curves, X-ray diffractograms and micro-
photographs of selected compounds. See DOI: 10.1039/b9nj00230h
Fig. 1 General structure of bent-shaped molecule that form bent-core
liquid crystals.
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1,3- N(1,3), 1,6- N(1,6), 1,7- N(1,7), 1,2- N(1,2) and 2,3- N(2,3)
while series II, contains different p-disubstituted phenylene
rings linked by methylene (CH2), carbonyl (CO), sulfide (S)
and sulfoxide (SO) groups as central moieties.
All compounds bear 4-n-tetradecyloxybenzoyloxybenzoates
as lateral structures, selected because of its well-known
tendency to induce wide bent-core mesophase ranges, low
transition temperatures as well as a high chemical stability.3
The interest on these structures arises because they may
open new possibilities for the design of mesogenic bent-core
structures. Moreover, the results can be also extended to other
self-organizing supramolecular systems, such as SAM or LB
films.18 On one hand, few naphthalene derivatives different
from 2,7-substitutions have been studied so far,8f,14,19 even
though they will allow different bending angles by changing
substitution on the aromatic structure. On the other hand,
they can be considered suitable candidates to introduce
substituents on the central aromatic core in an easy
way without varying significantly the length (L)/diameter (d)
ratio, in contrast with what happens with 1,3-phenylene
derivatives.
Concerning bis-4,40-disubstituted phenylenes, future possibilities
could be proposed for them, not only on changing the typical
1201 angle by using –S– and –CH2– moieties but also by
introducing either strong polarity and chirality in the apex
position by modifying the carbonyl or sulfoxide center.
Fig. 2 Schematic representations used for bent-shaped molecules (a).
Models proposed for some of the arrangements, in the SmCP and Colr
packings (b). Schematic representations of the antiferroelectric
switching of a SmCaPA and SmCsPF mesophase induced by applying
an electric field (c).
observed in molecules where the central core consists
of 1,3-disubstituted benzene, 2,6-disubstituted pyridine,
2,7-disubstituted naphthalene or 3,40-disubstituted biphenyl
rings.3 In these cases, a bent-core angle of about 1201 is
generated, which is considered the optimal angle to promote
compact packing affording polar mesophases. Nevertheless
the bending angle can be varied in the range between 105
and 1401 leading to mesomorphism. Thus the presence of a
substituted six-membered central aromatic ring (with halogens,
methyl or nitro groups)3,12 or alternatively the presence of
five-membered ring heterocycles13 cause a distortion of the
bent angle. On the other hand, recent interest has also been
focused on the search of ‘‘banana’’-like mesomorphism for
molecules showing a very acute central angle such as for
1,7-dihydroxynaphthalene derivatives.8f,14
Beside this, more flexible structures, either cyclic15 or odd
acyclic16 aliphatic spacers as well as single point examples of
linking units such as –CH2–, –CO–, –S–, –O– or –CH2OOC–
have been used by some authors to promote this type of
supramolecular packing.17
With the aim of going deeper in the supramolecular packing
of some of these scarcely studied bent-core structures herein,
we describe and discuss the ability of different bent-shaped
molecules to show liquid crystal behaviour.
The compounds selected for this study have been divided in
two series (Scheme 1). Series I contains a group of central
naphthalene derivatives where the aromatic system has
been substituted in different positions, namely 2,7- N(2,7),
Scheme 1 The synthetic route and the schematic representation of the
two series of bent-shaped compounds studied.
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Synthesis
Table 1 Transition temperatures (T/1C) and enthalpies (DH/kJ molꢁ1
)
for compounds N(2,7), N(1,3), N(1,6), N(1,7), N(1,2), N(2,3), CO, SO,
CH2, S, Ph(1,3) and Bi(3,40)
All the final compounds were prepared by condensation of the
4-(4-n-tetradecyloxybenzoyloxy)benzoic acid with the corres-
ponding diphenol using the DCC/DMAP method as shown
in Scheme 1. All the diphenols were purchased from
Sigma-Aldrich, except for 3,40-dihydroxybiphenyl that was
prepared as described before20 and 4,40-bisphenol sulfoxide
that was obtained by oxidation of the 4,40 thiobisphenol
using the method described by Engman.21 Mesomorphic,
electrooptic and optical properties of compounds CH2 and S
have already been described. However, their synthesis and
structural characterization is described here for the first time.
Compound
Phase transition/1C (DH/kJ molꢁ1 ab
)
N(2,7)
C ꢂ 103.0 (51.9) ꢂ SmCaPA ꢂ 118.0 (25.2) ꢂ I
I ꢂ 115.7 (26.3) ꢂ SmCaPA ꢂ 87.8 (52.3) ꢂ C
C ꢂ 127.9 (73.8) ꢂ I
N(1,3)
N(1,6)
N(1,7)
N(1,2)
N(2,3)
CO
I ꢂ 105.1 (40.5) ꢂ C
C ꢂ 110.1 (27.4) ꢂ SmCaPA ꢂ 148.2 (26.4) ꢂ I
I ꢂ 145.2 (26.9) ꢂ SmCaPA ꢂ 95.3 (24.4) ꢂ C
C ꢂ 145.0 (15.4) ꢂ C0 ꢂ 155.2 (54.0) ꢂ I
I ꢂ 149.0 (54.2) ꢂ C0 ꢂ 132.0 (13.7) ꢂ C
C ꢂ 87.8 (29.8) ꢂ SmA ꢂ 158.2 (12.2) ꢂ I
I ꢂ 153.2 (12.6) ꢂ SmA ꢂ 34.1 (7.5) ꢂ C
C ꢂ 127.3 (54.6) ꢂ SmA ꢂ 210.6 ꢂ N ꢂ 211.6 (7.4)c ꢂ I
I ꢂ 211.3 ꢂ N ꢂ 210.5 (7.8)c ꢂ SmA ꢂ 75.0 (44.8) ꢂ C
C ꢂ 155.6 (21.4) ꢂ SmCaPA ꢂ 195.3 (19.0) ꢂ I
I ꢂ 195.3 (17.7) ꢂ SmCaPA ꢂ 141.5 (22.8) ꢂ C
C ꢂ 143.5 (34.6) ꢂ SmCaPA ꢂ 162.2 (25.9) ꢂ I
I ꢂ 161.1 (25.6) ꢂ SmCaPA ꢂ 124.2 (36.0) ꢂ C
C ꢂ 123.9 (60.5) ꢂ SmCaPA ꢂ 161.6 (28.0) ꢂ I
I ꢂ 160.5 (27.6) ꢂ SmCaPA ꢂ 108.5 (30.2) ꢂ C
C ꢂ 150.8 ꢂ Colr ꢂ 156.2 (45.8)d ꢂ I
Results and discussion
SO
Liquid crystalline properties
CH2
All of the new compounds reported here were studied by
polarizing optical microscopy (POM), differential scanning
calorimetry (DSC) and X-ray diffraction (XRD) at variable
temperature in order to characterize their liquid crystalline
behaviour. Furthermore, the electro-optic responses of the
different materials were also investigated by POM under an
electric field in order to obtain additional information about
the liquid crystalline phases formed by these molecules and
their ability to switch under electric fields. The results obtained
using the different techniques led us to assign the liquid
crystalline properties gathered in Table 1 for these compounds.
For the sake of comparative analysis, the properties of the
related materials Bi(3,40)20 and Ph(1,3)20 are also included in
this table.
S
I ꢂ 154.9 (25.3) ꢂ Colr ꢂ 148.1 (22.9) ꢂ C
C ꢂ 103.9 (50.9) ꢂ SmCaPA ꢂ 118.3 (25.5) ꢂ I
I ꢂ 116.5 (24.9) ꢂ SmCaPA ꢂ 88.8 (49.6) ꢂ C
C ꢂ 74.2 (21.4) ꢂ SmCaPA ꢂ 156.9 (27.9) ꢂ I
I ꢂ 156.5 (27.1) ꢂ SmCaPA ꢂ 67.7 (17.5) ꢂ C
Ph(1,3)20
Bi(3,40)20
a
Data determined by DSC, from second scans at a scanning rate of
b
10 1C minꢁ1
.
Cr: crystal, SmA: smectic A mesophase, N: nematic
mesophase, Colr: columnar rectangular mesophase, SmCaPA: smectic
C anticlinic polar antiferroelectric mesophase, I: isotropic liquid.
c
d
Combined enthalpy for SmA–N–I transition. Combined enthalpy
for C–Colr–I transition.
(see ESIw). XRD studies confirm the smectic nature of the
mesophase and allowed us to calculate a layer spacing of 39 A
for both compounds. By evaluating the theorical length of the
molecules by stereomodels (considering all-trans conformation
of the terminal chains, see ESIw) it was possible to calculate a
tilt angle of 501 (Table 2) typical for molecules in the
SmCP phase.
As it can be seen, all the materials studied here exhibit liquid
crystalline mesophases characteristic of bent-cores except
for compounds N(1,3) and N(1,7). Enthalpy values for the
mesophase–isotropic liquid transitions are in the range
17–28 kJ molꢁ1, according to values reported for this type of
phase transition. Mesomorphic behaviour will be analysed
within the same series of compounds.
When comparing the range of mesophase of compounds
N(2,7) and N(1,6) with that of parent compounds Bi(3,40) and
Ph(1,3) (included in this study for comparative reasons) it is
possible to conclude that compounds N(2,7) and Ph(1,3)
provide a similar mesogenic range, whereas N(1,6) and
Bi(3,40) show the widest but similar range. It is worth
mentioning that when increasing the asymmetry of the
molecule (as for compounds N(1,6) and Bi(3,40)), a stabilization
of the mesophase is achieved as well as a remarkable increase
in the range of mesophase. Furthermore, 1,6-naphthalene
could be considered as an attractive alternative to the broadly
used 3,40-biphenylene structure.
(a) Series I: naphthalene derivatives. The mesomorphic
behaviour of compounds of this series is highly influenced
by the position of the lateral cores around the naphthalene
system, that is, by the bending angle generated between them.
For compounds N(2,7), N(1,3) and N(1,6), a molecular bend-
ing angle of approximately 1201 is afforded. Compounds
N(2,7) and N(1,6), exhibit typical texture of the polar smectic
C mesophase, growing from the isotropic liquid as concentric
defects to develop a grainy texture. However, compound
N(1,3) shows no mesomorphic behaviour even though the
angle is similar to that of the other two compounds. This
could be attributed to the fact that the two lateral cores are
connected to the same aromatic core in such a way that the
second aromatic ring acts as a bulky group disturbing the
compact packing of the molecules leading to the bent-core
liquid crystal phase. The smectic mesophase of compounds
N(2,7) and N(1,6) was assigned as the antiferroelectric
anticlinal variety (SmCaPA) (Fig. 2 and 3(a)) by the characteristic
textures observed by optical microscopy and complementary
dielectric studies revealing their antiferroelectric switching
Fig. 3 Photomicrographs of the textures of the (a) SmCP phase of
N(1,6) at 146 1C and of the nematic (b) and SmA (c) phases of N(2,3)
at 210 and 207 1C, respectively, between glass plates.
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Table 2 X-Ray diffraction data for the mesophases of the compounds N(2,7), N(1,6), N(1,2), N(2,3), CO, SO, CH2 and S
Compound
Phase
SmCP
Parameters A (exptl.)
La/A (theor.)
Layer spacing/A
Miller indices
N(2,7)
c: 39.6
69.8
39.2
20.1
13.1
39.0
33.9
33.3
42.8
21.4
49.4
24.7
16.5
46.2
23.1
15.4
43.8
25.8
20.8
16.1
001
002
003
001
001
001
001
002
001
002
003
001
002
003
101
002
400
103
N(1,6)
N(1,2)
N(2,3)
CO
SmCP
SmA
SmA
c: 39.0
c: 33.9
c: 33.3
c: 42.8
68.6
56.8 (38.5)b
56.6 (37.5)b
72.5
SmCP
SO
CH2
S
SmCP
SmCP
Colr
c: 49.4
c: 46.2
73.0
72.5
72.9
a: 83
c: 51.5
a
b
Molecular length calculated considering extended conformation of terminal chains. In parentheses, length corresponding to half molecule.
When the angle is reduced to approximately 601, as
for compounds N(1,7), N(1,2) and N(2,3) (substitutions 1,7-,
1,2- and 2,3- on the naphthalene unit, respectively),
mesomorphic behaviour is observed for two out of the three
compounds.
Compound N(1,7) showed only one peak in the DSC
Fig. 4 Different schematic drawings of the molecules proposed for
thermogram on the heating process corresponding to a crystal
the SmA mesophase induced by bent-core molecules: for a SmAP
to isotropic liquid transition. However, textures consistent
mesophase (a) and for a calamitic SmA mesophase (b, c) (any polar
with a smectic A mesophase (SmA) were observed under
POM for the compounds N(1,2) and N(2,3) as fan-shaped
textures were formed (Fig. 3(c)). In both cases, the mesophase
was stable over a very wide range of temperatures. It is
remarkable that even if the bent angle is similar for both
compounds, the breaking of the symmetry in the case of
compound N(1,2) decreased significantly the transition
temperatures for this material. On the other hand, compound
N(2,3) exhibits also a very short range of enantiotropic
nematic mesophase above the SmA as could be detected by
the appearance of typical nematic droplets on slow cooling
from the isotropic liquid. This mesophase was confirmed by a
small peak on the DSC thermogram. However, it was not
possible to obtain an X-ray diffractogram of this phase due to
the very short range of temperature in which it appears. X-Ray
diffractograms of the SmA mesophase showed only one strong
reflection in the short range angle region corresponding to a
layer spacing of 34 and 33 A for compounds N(1,2) and
N(2,3), respectively. These values are close to that calculated
theoretically for a half molecule so pointing to an arrangement
like that shown in Fig. 4(c).
arrangement is proposed in this case).
Similar behaviour was observed for compound N(1,2). In
this case, initially on cooling the isotropic liquid a poorly
aligned texture showing several defects was obtained and a
higher electric field (up to 240 Vpp) is necessary to reach the
black texture (Fig. 5(f)–(j)). In both cases, when removing the
electric field, no changes are observed, even when uncrossing
the polarizers. These behaviours indicate that there might be a
reorientation of the molecules induced by the electric field.
However there is not any experimental data to confirm the
Furthermore, the behaviour of the mesophase of the
compounds N(1,2) and N(2,3) under an electric field was
studied in 5 mm Linkam commercial cells. For compound
N(2,3), initially on cooling from the isotropic phase, the
sample showed a birefringent semi-aligned texture with few
defects (Fig. 5(a)). When applying an increasing electric field
to the sample, yellow stripes appeared perpendicular to the
alignment direction of the sample (Fig. 5(b)). When a higher
voltage was reached (150 Vpp), the stripes almost disappeared
and the texture became black (Fig. 5(c)).
Fig. 5 Microphotographs in 5 mm commercial Linkam cell of
compounds: (top) N(2,3) at 207 1C applying no electric field (a) and
applying (b) 120 Vpp, (c) 130 Vpp, (d) 140 Vpp and (e) 150 Vpp of AC
voltage at 1 Hz; (bottom) N(1,2) at 164 1C applying no electric field
(i) and applying (j) 200 Vpp, (k) 220 Vpp, (l) 230 Vpp and (e) 240 Vpp
.
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presence of a SmAP phase. No current peak was detected
when applying electric field. Further studies in order to
analyze the dielectric and electro-optic behaviour for these
compounds are being carried out.
As the molecular angle is small and the central core bulky,
the molecules can not be packed one inside the other as is
usually proposed for bent-core mesophases and a classical
parallel orthogonal packing is likely present (Fig. 4(a)). Under
such conditions a smectic A arrangement could be achieved
if molecules are assembled, for example, in one of the
dispositions shown in Fig. 4(b) or (c).
Fig. 6 Photomicrographs of the texture of (a) SmCP phase of
compound CO at 180 1C when uncrossing polarizers (a) left and
(b) right. (c) columnar mesophase of compound S at 152 1C.
angle of 451 could be calculated for this compound. The
mesophase of this compound was studied in detail and results
are gathered elsewhere.22
When comparing the mesogenic behaviour of this series of
compounds with those observed for imine-based analogues
reported by Lee et al.,14b significant differences are observed
(see ESIw). In the case of 2,7- and 1,6-substitutions a
remarkable decrease in the clearing points, with a significant
reduction of mesophase range, is achieved when changing
from imine to ester. However, only a slight decrease on
the clearing points is noticed for the other compounds of the
series. Concerning the mesophases, it is worth mentioning the
appearance of the B4 phase for some of the imine derivatives,
which could not be detected for the ester analogues. Further,
N(2,3) showed a nematic phase, not described for the imine
homologue. Liquid crystalline phases were not formed for the
(1,7) or (1,3) derivatives in either of the series.
A columnar phase was detected for compound S in a
very short range of mesophase. A mosaic texture was observed
under POM (see Fig. 6(c)) when cooling from the isotropic
liquid and up to four reflections in the X-ray diffraction
pattern were detected, which could be indexed to
a
rectangular columnar cell which lattice parameters a = 83 A
and c = 51.5 A.
When applying an electric field to the columnar mesophase
of this compound, a clear electro-optical switching was
observed. This behaviour has been studied in detail concluding
that a transition from a columnar to a SmCP mesophase has
taken place induced by the electric field as has been published
elsewhere.22b
(b) Series II: bis-4,40-disubstituted phenylene derivatives. In
the case of compounds of series II, all of them exhibit liquid
crystalline properties, irrespective of their angular structure.
Compounds CO and SO showed a SmCaPA mesophase as
could be assigned by electrooptical and dielectric measure-
ments. Although both compounds have rather similar
structures and show a similar mesomorphic behaviour,
compound CO, bearing the carbonyl moiety, leads to a slight
stabilization of both the solid and the liquid crystal phases.
Likewise, the X-ray patterns of these two compounds in the
mesophase showed up to three reflections at periodic distances
in the small-angle region in addition to a diffuse wide angle
scattering (see Table 2). Layer spacings of 43 and 49 A were
measured experimentally at the SmCP phase for compounds
CO and SO, respectively. When comparing experimental
values with those determined theoretically using stereomodels
(considering extended conformation of the terminal chains), it
was possible to calculate tilting angles of around 49 and 411,
respectively.
Interestingly, both carbonyl (–CO–) and methylene (–CH2–)
central bent-cores generate an isotropic texture for the SmCP
mesophase, with dark conglomerates where domains of
different chirality are observed when uncrossing the polarizers
(see Fig. 6(a) and (b)). However, the transition temperatures
are significantly lower for the methylene derivative as could be
expected from the stronger polar nature of the CO group. In
the case of the sulfur derivatives (SO and S), the behaviour is
slightly different when substituting sulfoxide for the less rigid
sulfur atom. A columnar mesophase in very narrow interval of
temperature is obtained instead of the SmCP mesophase
assigned for compound SO, however, a very similar range of
mesophases are induced by the two compounds. This fact
indicates a remarkable effect of the central moiety on the
packing of the molecules hindering a lamellar arrangement
for compound S, only reached under application of an
electric field.
Compounds CH2 and S can be related to CO and SO. In the
later cases, hybridization of the central atom was changed
from sp2 to sp3 (for CH2 and S) which involves variations in
both angle and conformational freedom, as well as, previously
mentioned, their polar and chiral potentials. Compounds CH2
and S form bent-core mesophases. Even though the methylene-
derivated core (CH2) is more flexible than the carbonyl one
and much more than the other aromatic cores studied in this
paper, compound CH2 still shows a wide range of SmCP
mesophase. The antiferroelectric anticlinal nature of this
mesophase was confirmed by electrooptical and dielectric
measurements. X-Ray diffraction patterns show up to three
reflections in the small-angle region in addition to a diffuse
wide angle scattering. A layer spacing of 46 A and a tilting
Conclusions
Two different series of bent-shaped molecules have been
prepared and their supramolecular self-organization at
variable temperature has been studied.
In order to readily control the bent-shaped molecular
packing, naphthalene has been used as the origin of
bent-central cores. Different bis-4-n-tetradecyloxybenzoyloxy-
benzoates resulting in a change of the bending angle proved
that when the bending angle was around 1201, SmCP
mesomorphism can be induced, whereas when the angle was
much smaller, around 601, a SmA phase that shows a response
under electric field occurred. However, it seems that not only
the angle is determining in the mesomorphic behaviour as
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some of the compounds are crystalline even if they show
similar bending angle. The wide ranges of mesophase
determined, together with the number of available positions
for substituents, open interesting possibilities for naphthalene
central cores to be used as bending units to generate polar
order and mesomorphism.
stirred for 24 h, the resulting solid was filtered off and the
filtrate was evaporated to give a solid, which was purified by
flash chromatography on silica gel, using dichloromethane as
the eluent. The solid was crystallized twice, first from toluene
and then from ethyl acetate.
2,7-Bis[4-(4-n-tetradecyloxybenzoyloxy)benzoyloxy]naphthalene
1
N(2,7)). Yield: 25%. Rf (hexanes–ethyl acetate 8 : 2): 0.5. H
On the other hand, bent-core mesomorphism can be also
achieved over a significant range of temperatures by using
appropriate bis-4,40-disubstituted phenylene derivatives.
Groups such as –CO–, –SO– and –CH2– connecting them
induce the SmCP phase and a sulfide group (–S–) leads to
columnar order. Besides, two compounds (CO and CH2) show
isotropic texture with dark conglomerates, while one of them
(S) exhibits a Colr–SmCP change upon applying a high
enough electric field.
NMR (300 MHz, CDCl3): d 0.86 (t, J = 6.5 Hz, 6H);
1.20–1.38 (m, 44H); 1.77–1.84 (m, 4H); 4.03 (t, J =
6.7 Hz, 4H); 6.96 (d, J = 8.7 Hz, 4H), 7.15–7.18 (m, 4H);
7.35 (d, J = 9.0 Hz, 4H); 7.48 (d, J = 7.8 Hz, 2H); 8.12
(d, J = 8.7 Hz, 4H); 8.26 (d, J = 9.0 Hz, 4H). 13C NMR
(300 MHz, CDCl3) d 14.2, 22.7, 26.1, 29.4, 29.4, 29.5, 29.6,
29.7, 31.9, 68.5, 100.0, 114.4, 115.9, 119.4, 121.0, 122.2, 126.7,
129.9, 131.9, 132.4, 151.5, 155.6,163.8, 164.2, 164.4. IR
(Nujol, NaCl): 1734, 1722, 1678, 1600, 1463, 1161, 1055 cmꢁ1
.
Experimental
EA for C66H80O10: calc.: C 76.74%, H 7.75%; found: C 76.84,
H 7.99%. MS (FAB+) m/z: 317, 367, 437.
Infrared spectra for all the compounds were obtained using
ATI Mattson (FTIR) and Nicolet Avatar 360 (FTIR) spectro-
1,3-Bis[4-(4-n-tetradecyloxybenzoyloxy)benzoyloxy]naphthalene
(N(1,3)). Yield: 64%. Rf (dichloromethane–hexanes 9 : 1):
0.17. 1H NMR (400 MHz, CDCl3): d 0.88 (t, J = 6.8 Hz, 6H);
1.27–1.57 (m, 44H); 1.81–1.85 (m, 4H); 4.05 (t, J =
6.4 Hz, 4H); 7.00 (dd, J = 2.8 Hz, J = 8.8 Hz, 4H),
7.38–7.44 (m, 5H); 7.50–7.58 (m, 2H); 7.70–7.72 (m, 1H);
7.90 (d, J = 8.0 Hz, 1H); 7.97 (d, J = 8.0 Hz, 1H);
8.15–8.19 (m, 4H); 8.32 (d, J = 8.4 Hz, 2H); 8.41 (d, J =
8.4 Hz, 2H). 13C NMR (400 MHz, CDCl3) d 14.1, 22.7, 26.0,
29.1, 29.4, 29.6, 29.6, 29.7, 29.7, 29.7, 31.9, 68.4, 114.3, 114.4,
116.9, 121.0 121.0, 121.5, 122.1, 122.3, 125.3, 126.4, 126.5,
126.7, 127.4, 128.0, 131.9, 132.0, 132.4, 132.5, 134.4, 147.5,
147.9, 155.6, 155.7, 163.8, 163.9, 164.0, 164.2, 164.3. IR
(Nujol, NaCl): 2920, 2851, 1736, 1604, 1467, 1258, 1207,
1162, 1067 cmꢁ1. EA for C66H80O10: calc.: C 76.71%,
H 7.80%; found: C 76.81%, H 7.81%. MS (FAB+) m/z:
368, 451, 1056.
photometers in the 400–4000 cmꢁ1 spectral range. 1H and 13
C
NMR spectra were recorded on Bruker ARX-300 MHz,
Bruker AV-400 MHz and AV-500 MHz spectrometers and
samples were in solution. Elemental analyses were performed
on a Perkin-Elmer 240 analyzer. Mass spectrometry studies
(FAB+, MALDI+) were performed with a VG AutoSpec
EBE and a Microflex (MALDI-ToF). Commercial chemicals
(reagent grade) were purchased from Aldrich Chemical Co.,
Fluka or Panreac and used without further purification.
Solvents were purified and dried by standard techniques.
Mesomorphic properties were studied by optical microscopy
using an Olympus BH2 microscope with crossed polarizers.
The microscope was connected to a Linkam THMS 600 hot
stage and an Olympus DP-12 camera. Transition temperatures
were determined by differential scanning calorimetry (DSC)
using TA2910, DSC Q20, DSC Q1000 or DSC Q2000
differential calorimeters calibrated with indium (156.6 1C,
28.44 J gꢁ1). X-Ray diffraction patterns were obtained with
an evacuated Pinhole Camera (Anton–Paar) operating with a
point-focused Ni-filtered Cu-Ka beam. The samples were held
in Lindemann glass capillaries (1 mm diameter) and heated,
where necessary, with a variable-temperature attachment. The
diffraction patterns were collected on flat photographic film.
Polarization measurements were carried out using commercial
cells with ITO electrodes coated with polyimide (LINKAM, 5 mm).
The triangular wave voltage was supplied by an HP3245A
function generator plus an amplifier and the current
was recorded using an IO tech 488/6A multimeter. All the
equipment was controlled with a Fujitsu S-325 generator and a
Tektronix TDS 310 oscilloscope.
1,6-Bis[4-(4-n-tetradecyloxybenzoyloxy)benzoyloxy]naphthalene
(N(1,6)). Yield: 50%. Rf (dichloromethane–hexanes 9 : 1):
0.54. 1H NMR (400 MHz, CDCl3): d 0.88 (t, J = 6.8 Hz, 6H);
1.27–1.55 (m, 44H); 1.79–1.87 (m, 4H); 4.06 (t, J =
6.8 Hz, 4H); 6.98–7.01 (m, 4H), 7.38–7.44 (m, 6H); 7.58
(dd, J = 7.6 Hz, J = 8.4 Hz, 1H); 7.78–7.81 (m, 2H); 8.02
(d, J = 9.2 Hz, 1H); 8.15–8.19 (m, 4H); 8.32–8.34 (m, 2H);
8.41–8.43 (m, 2H). 13C NMR (300 MHz, CDCl3) d 14.1, 22.7,
26.0, 29.1, 29.3, 29.6, 29.6, 29.7, 29.7, 29.7, 31.9, 68.4, 114.4,
121.0 121.0, 122.1, 122.3, 125.4, 126.0, 126.6, 127.6, 131.9,
132.0, 132.4, 132.5, 132.8, 146.6, 149.3, 155.5, 155.6, 163.8,
163.8, 164.4. IR (Nujol, NaCl): 2920, 2850, 1736, 1603, 1255,
1202, 1162, 1061 cmꢁ1. EA for C66H80O10: calc.: C 76.71%,
H 7.80%; found: C 76.57%, H 7.66%. MS (FAB+) m/z: 317,
451, 1056.
General synthetic procedure used to prepare bent-shaped
compounds
DCC (1.1 mmol) was added to a cooled (0 1C), stirred mixture
of the corresponding diphenol (0.39 mmol), 4-(4-tetradecyloxy-
benzoyloxy)benzoic acid (1 mmol) and DMAP (0.5 mmol) in
dichloromethane (20 mL) under an argon atmosphere. The
reaction mixture was stirred for 30 min at 0 1C and then
allowed to warm to room temperature. The mixture was
1,7-Bis[4-(4-n-tetradecyloxybenzoyloxy)benzoyloxy]naphthalene
(N(1,7)). Yield: 49%. Rf (dichloromethane–hexanes 8 : 2): 0.28.
1H NMR (400 MHz, CDCl3): d 0.88 (t, J = 6.8 Hz, 6H);
1.26–1.50 (m, 44H); 1.79–1.86 (m, 4H); 4.05 (t, J =
6.8 Hz, 4H); 6.97–6.99 (m, 4H), 7.35–7.45 (m, 6H); 7.55
(dd, J = 7.6 Hz, J = 8.4 Hz, 1H); 7.75 (d, J = 1.6 Hz, 1H);
ꢀc
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View Article Online
7.83 (d, J = 8.4 Hz, 1H); 7.99 (d, J = 8.8 Hz, 1H); 8.14–8.16
(m, 4H); 8.29–8.31 (m, 2H); 8.39–8.41(m, 2H). 13C NMR
(300 MHz, CDCl3) d 14.1, 22.7, 26.0, 29.1, 29.3, 29.6, 29.6,
29.7, 29.7, 29.7, 31.9, 68.4, 114.4, 121.0 121.0, 122.1, 122.3,
125.4, 126.0, 126.6, 127.6, 131.9, 132.0, 132.4, 132.5, 132.8,
146.6, 149.3, 155.5, 155.6, 163.8, 163.8, 164.4. IR
(Nujol, NaCl): 2920, 2850, 1736, 1603, 1255, 1202, 1162,
1061 cmꢁ1. EA for C66H80O10: calc.: C 76.71%, H 7.80%;
found: C 76.50%, H 7.87%. MS (FAB+) m/z: 317, 451, 1056.
6.97 (d, J 8.7 Hz, 4H); 7.20–7.37 (m, 8H); 7.91 (d, J =
8.7 Hz, 4H); 8.14 (d, J = 8.7 Hz, 4H); 8.28 (d, J = 8.7 Hz,
4H). 13C NMR (300 MHz, CDCl3) d 14.1, 22.7, 25.9, 29.1,
29.3, 29.5, 29.6, 29.9, 31.9, 68.4, 109.3, 114.4, 120.9, 121.8,
122.2, 126.4, 131.6, 131.7, 131.9, 132.0, 132.4, 135.1, 154.2,
155.7, 163.9, 164.0, 164.3. IR (Nujol, NaCl): 1730, 1645, 1602,
1462, 1253, 1165 cmꢁ1 EA for C68H82O11S: calc.: C 76.21%,
H 7.60%, S 2.94%; found: C 76.40%, H 7.61%, S 2.61%.
MS (FAB+) m/z: 317, 437, 649, 1087.
Bis[4-(4-n-tetradecyloxybenzoyloxy)benzoyloxyphenyl]methane
1
(CH2). Yield: 51%. Rf (hexanes–ethyl acetate 8 : 2): 0.4. H
1,2-Bis[4-(4-n-tetradecyloxybenzoyloxy)benzoyloxy]naphthalene
(N(1,2)). Yield: 23%. Rf (dichloromethane–hexanes 9 : 1):
1
NMR (300 MHz, CDCl3): d 0.87 (t, J = 6.0 Hz, 6H);
1.25–1.47 (m, 44H); 1.78–1.83 (m, 4H); 4.01– 4.06 (m, 6H);
6.97 (d, J = 8.4 Hz, 4H); 7.15 (d, J = 8.8 Hz, 4H); 7.27
(d, J = 8.8 Hz, 4H); 7.35 (d, J = 8.4 Hz, 4H); 8.15 (d, J =
8.4 Hz, 4H); 8.27 (d, J = 8.4 Hz, 4H). 13C NMR (300 MHz,
CDCl3) d 13.7, 22.2, 25.5, 28.6, 29.1, 29.4, 29.5, 29.6, 29.7,
68.4, 114.4, 120.9, 121.6, 121.7, 122.1, 126.9, 130.0, 131.7,
132.4, 138.4, 149.3, 155.3, 163.8, 164.3, 164.6. IR (Nujol, NaCl):
1727, 1605, 1509, 1463, 1286, 1256, 888, 846 cmꢁ1. EA for
C69H84O10: calc.: C 77.21%, H 7.89%; found: C 77.00%,
H 7.72%. MS (FAB+) m/z: 317, 437, 635, 1073.
0.14. H NMR (400 MHz, CDCl3): d 0.89 (t, J = 6.8 Hz, 6H);
1.27–1.55 (m, 44H); 1.81–1.84 (m, 4H); 4.06 (t, J = 6.8 Hz, 4H);
6.98–7.01 (m, 4H), 7.27 (d, J = 9.2 Hz, 2H); 7.34 (d, J =
8.8 Hz, 2H); 7.53–7.57 (m, 3H); 7.90 (d, J = 8.8 Hz, 1H);
7.93–7.96 (m, 2H); 8.12–8.16 (m, 4H); 8.19 (d, J = 8.8 Hz, 2H);
8.32 (d, J = 8.8 Hz, 2H). 13C NMR (300 MHz, CDCl3) d 14.1,
22.7, 26.0, 29.1, 29.4, 29.5, 29.6, 29.7, 29.7, 29.7, 31.9, 68.4,
114.4, 114.4, 121.0 121.1, 121.4, 121.8, 122.1, 122.2, 125.9,
126.2, 126.3, 126.8, 127.1, 128.0, 131.8, 132.0, 132.4, 132.4,
132.5, 137.4, 139.7, 155.5, 155.7, 163.5, 163.7, 163.8, 163.8,
164.1, 164.2. IR (Nujol, NaCl): 2922, 2852, 1729, 1607, 1465,
1263, 1168, 1063 cmꢁ1. EA for C66H80O10: calc.: C 76.71%,
H 7.80%; found: C 76.29%, H 7.74%. MS (FAB+) m/z: 317,
451, 1056.
Bis[4-(4-n-tetradecyloxybenzoyloxy)benzoyloxyphenyl]sulfur (S).
Yield: 60%. Rf (dichloromethane–ethyl acetate 9 : 1): 0.52. 1H
NMR (300 MHz, CDCl3): d 0.88 (t, J = 6.6 Hz, 6H);
1.27–1.48 (m, 44H); 1.80–1.86 (m, 4H); 4.05 (t, J = 6.6 Hz,
4H); 6.99 (d, J = 8.1 Hz, 4H); 7.20 (d, J = 8.1 Hz, 4H); 7.37
(d, J = 8.1 Hz, 4H); 7.43 (d, J = 8.1 Hz, 4H); 8.15 (d, J =
8.1 Hz, 4H); 8.27 (d, J = 8.1 Hz, 4H). 13C NMR (300 MHz,
CDCl3) d 14.1, 22.7, 25.9, 29.1, 29.3, 29.5, 29.6, 29.9 31.9, 68.4,
109.3, 114.4, 120.9, 122.0, 122.1, 122.6, 126.6, 131.8, 132.2,
132.4, 133.0, 150.1, 155.4, 163.8, 164.2. IR (Nujol, NaCl):
1732, 1607, 1584, 1463, 1397, 1395, 889 cmꢁ1. EA for
C68H82O10S: calc.: C 74.83%, H 7.57%, S 2.94%; found:
C 74.71%, H 7.24%, S 2.61%. MS (FAB+) m/z: 317, 437,
653, 1092.
2,3-Bis[4-(4-n-tetradecyloxybenzoyloxy)benzoyloxy]naphthalene
(N(2,3)). Yield: 80%. Rf (dichloromethane–hexanes 9 : 1):
1
0.25. H NMR (400 MHz, CDCl3): d 0.88 (t, J = 6.8 Hz, 6H);
1.27–1.58 (m, 44H); 1.80–1.84 (m, 4H); 4.03 (t, J = 6.4 Hz,
4H); 6.95 (d, J = 7.2 Hz, 4H), 7.27 (d, J = 6.8 Hz, 4H); 7.88
(dd, J = 3.2 Hz, J = 6.0 Hz, 2H); 7.86–7.89 (m, 4H); 8.09
(d, J = 7.2 Hz, 4H); 8.16 (d, J = 6.4 Hz, 4H). 13C NMR
(400 MHz, CDCl3) d 14.1, 22.7, 26.0, 29.1, 29.3, 29.6, 29.5,
29.6, 29.7, 31.9, 68.4, 114.4, 121.0 121.1, 122.1, 126.0, 126.5,
127.6, 131.7, 131.8, 132.4, 141.3, 155.5, 163.8, 163.9, 164.2. IR
(Nujol, NaCl): 2923, 2853, 1732, 1601, 1465, 1253, 1202, 1161,
1059 cmꢁ1. EA for C66H80O10: calc.: C 76.71%, H 7.80%;
found: C 76.75%, H 7.65%. MS (FAB+) m/z: 368, 451,
541, 1056.
Acknowledgements
This research was supported by CICYT-FEDER of Spain-UE
MAT2006-13571-C02 and the Department of Ciencia,
Bis[4-(4-n-tetradecyloxybenzoyloxy)benzoyloxyphenyl] ketone
(CO). Yield: 40%. Rf (hexanes–ethyl acetate 8/2): 0.66.
1H NMR (300 MHz, CDCl3): d 0.86 (t, J = 6.3 Hz, 6H);
1.23–1.42 (m, 44H); 1.80–1.86 (m, 4H); 4.03 (t, J = 6.6 Hz, 4H);
6.97 (d, J 8.7 Hz, 4H); 7.20–7.37 (m, 8H); 7.91 (d, J =
8.7 Hz, 4H); 8.14 (d, J = 8.7 Hz, 4H); 8.28 (d, J =
8.7 Hz, 4H). 13C NMR (300 MHz, CDCl3) d 14.1, 22.7,
25.9, 29.1, 29.3, 29.5, 29.6, 29.9, 31.9, 68.4, 109.3, 114.4,
120.9, 121.8, 122.2, 126.4, 131.6, 131.7, 131.9, 132.0, 132.4,
135.1, 154.2, 155.7, 163.9, 164.0, 164.3. IR (Nujol, NaCl):
1730, 1645, 1602, 1462, 1253, 1165 cmꢁ1. EA for C69H82O11:
calc.: C 76.21%, H 7.60%, S 2.94%; found: C 76.40%,
H 7.61%, S 2.61%. MS (FAB+) m/z: 317, 437, 649, 1087.
Tecnologıa y Universidad del Gobierno de Aragon-Fondo
´ ´
Social Europeo (project E04); N. G. acknowledges the Spanish
Government for a Juan de la Cierva fellowship.
References
1 T. Niori, T. Sekine, J. Watanabe, T. Furukawa and H. Takezoe,
J. Mater. Chem., 1996, 6, 1231.
2 D. R. Link, G. Natale, R. Shao, J. E. Maclennan, N. A. Clark,
E. Korblova and D. M. Walba, Science, 1997, 278, 1924.
3 (a) G. Pelzl, S. Diele and W. Weissflog, Adv. Mater., 1999, 11, 707;
(b) C. Tschierske and G. Dantlgraber, Pramana, 2003, 61, 455;
(c) D. M. Walba, Top. Stereochem., 2003, 24, 457; (d) M. B. Ros,
J. L. Serrano, M. R. De la Fuente and C. L. Folcia, J. Mater.
Chem., 2005, 15, 5093; (e) R. Amaranatha Reddy and
C. Tchierske, J. Mater. Chem., 2006, 16, 907; (f) H. Takezoe
and Y. Takanishi, Jpn. J. Appl. Phys., 2006, 45, 597; (g) G. Pelzl
and W. Weissflog, Thermotropic Liquid Crystals. Recent Advances,
ed. A. Ramamoorthy, Springer, The Netherlands, 2007,
Bis[4-(4-n-tetradecyloxybenzoyloxy)benzoyloxyphenyl] sulfoxide
(SO). Yield: 40%. Rf (dichloromethane–ethyl acetate 9 : 1):
0.66. 1H NMR (300 MHz, CDCl3): d 0.86 (t, J = 6.3 Hz, 6H);
1.23–1.42 (m, 44H); 1.80–1.86 (m, 4H); 4.03 (t, J = 6.6 Hz, 4H);
ch. 1, p. 1; (h) A. Jakli, C. Bailey and J. Harden, Thermotropic
´
ꢀc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2009 New J. Chem., 2009, 33, 2007–2014 | 2013

View Article Online
Liquid Crystals. Recent Advances, ed. A. Ramamoorthy, Springer,
The Netherlands, 2007, ch. 2, p. 59.
´
2005, 871; (i) J. Barbera, N. Gimeno, I. Pintre, M. B. Ros and
J. L. Serrano, Chem. Commun., 2006, 1212.
4 J. Etxebarria and M. B. Ros, J. Mater. Chem., 2008, 18, 2919.
5 (a) V. Prasad, S. W. Kang, X. H. Qi and S. Kumar, J. Mater.
Chem., 2004, 14, 1495; (b) W. Weissflog, G. Naumann, B. Kosata,
11 (a) E. Gorecka, D. Pociecha, J. Matraszek, J. Mieczkowski,
D. Guillon and B. Donnio, J. Am. Chem. Soc., 2004, 126, 15946;
(b) E. Gorecka, D. Pociecha, J. Matraszek, J. Mieczkowski,
Y. Shimbo, Y. Takanishi and H. Takezoe, Phys. Rev. E: Stat.,
Nonlinear, Soft Matter Phys., 2006, 73, 031704; (c) I. C. Pintre,
M. W. Schroder, A. Eremin, S. Diele, Z. Vakhovskaya, H. Kresse,
´
¨
R. Friedemann, S. A. Rama Krishman and G. Pelzl, J. Mater.
Chem., 2005, 15, 4328; (c) I. C. Pintre, N. Gimeno, J. L. Serrano,
M. B. Ros, I. Alonso, C. L. Folcia, J. Ortega and J. Etxebarria,
J. L. Serrano, M. B. Ros, I. Alonso, J. Martı
C. L. Folcia, J. Etxebarria, F. Goc, D. B. Amabilino,
E. Puigmartı-Luis and E. Gomar-Nadal, Chem. Commun., 2008,
2523.
´
nez-Perdiguero,
J. Mater. Chem., 2007, 17, 2219; (d) I. Alonso, J. Martı
´
nez-
´
Perdiguero, C. L. Folcia, J. Etxebarria, J. Ortega, I. C. Pintre
and M. B. Ros, Phys. Rev. E: Stat., Nonlinear, Soft Matter Phys.,
2008, 78, 041701.
6 (a) R. Achten, A. Koudijs, Z. Karczmarzyk, A. T. M. Marcelis and
E. J. R. Sudholter, Liq. Cryst., 2004, 31, 215; (b) C. V. Yelamaggad,
M. Mathews, S. A. Nagamani, D. S. S. Rao, S. K. Prasad,
S. Findeisen and W. Weissflog, J. Mater. Chem., 2007, 17, 284, and
references therein.
12 (a) S. Umadevi and B. K. Sadashiva, Chem. Mater., 2006, 18, 5186;
(b) H. N. Shreenivasa Murthy, M. Bodyagin, S. Diele,
U. Baumeister, G. Pelzl and W. Weissflog, J. Mater. Chem.,
2006, 16, 1634.
13 (a) S. Kang, Y. Saito, N. Watanabe, M. Tokita, Y. Takanishi,
H. Takezoe and J. Watanabe, J. Phys. Chem. B, 2006, 110, 5205;
(b) S. W. Choi, S. Kang, Y. Takanishi, K. Ishikawa, J. Watanabe
and H. Takezoe, Angew. Chem., Int. Ed., 2006, 45, 6503;
(c) E. Cavero, D. P. Lydon, S. Uriel, M. R. De la Fuente,
7 (a) V. Prasad, S. W. Kang and S. Kumar, J. Mater. Chem., 2003,
13, 1259; (b) R. Achten, R. Cuypers, M. Giesbers, A. Koudijs,
A. Marcelis and E. Sudholter, Liq. Cryst., 2004, 31, 1167.
8 (a) S. K. Lee, C. W. Park, J. G. Lee, K. T. Kang, K. Nishida,
Y. Shimbo, Y. Takanishi and H. Takezoe, Liq. Cryst., 2005, 32,
1205; (b) S. K. Lee, S. Heo, J. G. Lee, K. T. Kang, K. Kumazawa,
V. Koushi, K. Nishida, Y. Shimbo, Y. Takanishi, J. Watanabe,
Doi, T. Takahashi and H. Takezoe, J. Am. Chem. Soc., 2005, 127,
11085; (c) R. Amaranatha Reddy, B. K. Sadashiva and
U. Baumeister, J. Mater. Chem., 2005, 15, 3303; (d) K. Nishida,
M. Cepic, W. J. Kim, S. K. Lee, S. Heo, Y. Takanishi, K. Isikawa,
K. T. Kang, J. Watanabe and H. Takezoe, Phys. Rev. E: Stat.,
Nonlinear, Soft Matter Phys., 2006, 74, 21704; (e) K. Nishida,
W. J. Kim, S. K. Lee, S. Heo, J. G. Lee, K. T. Kang, Y. Takanishi,
K. Isikawa, K. T. Kang, J. Watanabe and H. Takezoe, Jpn. J.
Appl. Phys., 2006, 45, L329; (f) S. K. Lee, M. Tokita, Y. Shimbo,
K. T. Kang, H. Takezoe and J. Watanabe, Bull. Korean Chem.
Soc., 2007, 28, 2241.
9 (a) G. Dantlgraber, A. Eremin, S. Diele, A. Hauser, H. Kresse,
G. Pelzl and C. Tschierske, Angew. Chem., Int. Ed., 2002, 41, 2408;
(b) C. Keith, R. Reddy, H. Hahn, H. Lang and C. Tschierske,
Chem. Commun., 2004, 1898; (c) R. Reddy, G. Dantlgraber,
U. Baumeister and C. Tschierske, Angew. Chem., Int. Ed., 2006,
45, 1928; (d) C. Keith, R. Reddy, A. Hauser, U. Baumeister and
C. Tschierske, J. Am. Chem. Soc., 2006, 128, 3051; (e) R.A. Reddy,
U. Baumeister, C. Keith and C. Tschierske, J. Mater. Chem., 2007,
17, 62; (f) C. Keith, G. Dantlgraber, R. A. Reddy, U. Baumeister
and C. Tschierske, Chem. Mater., 2007, 19, 694; (g) Y. Zhang,
M. J. O’Callaghan, U. Baumeister and C. Tschierske, Angew.
Chem., Int. Ed., 2008, 47, 6892.
´
J. L. Serrano and R. Gimenez, Angew. Chem., Int. Ed., 2007, 46,
5175.
14 (a) E.-J. Choi, X. Cui, W.-C. Zin, C. W. Ohk, T.-K. Lim and
J.-H. Lee, ChemPhysChem, 2007, 8, 1919; (b) S. K. Lee, Y. Naito,
L. Shi, M. Tokita, H. Takezoe and J. Watanabe, Liq. Cryst., 2007,
34, 935.
15 (a) G. Gesekus, I. Dierking, S. Gerber, M. Wulf and V. Vill, Liq.
Cryst., 2004, 31, 145; (b) B. Glettner, S. Hein, R. A. Reddy,
U. Baumeister and C. Tschierske, Chem. Commun., 2007, 2596;
(c) G. Dantlgraber, C. Keith, U. Baumeister and C. Tschierske,
J. Mater. Chem., 2007, 17, 3419.
16 (a) S. W. Choi, M. Zennyoji, T. Takanishi, H. Takezoe, T. Niori
and J. Watanabe, Mol. Cryst. Liq. Cryst., 1999, 328, 185;
(b) M. Sepelj, A. Lesac, U. Baumeister, S. Diele, H. L. Nguyen
and D. Bruce, J. Mater. Chem., 2007, 17, 1154; (c) Y. Naito,
R. Ishige, M. Itoh, M. Tokita and J. Watanabe, Chem. Lett., 2008,
37, 880; (d) E. Bialecka-Florjanczyk, I. Sledzinska, E. Gorecka and
J. Przedmojski, Liq. Cryst., 2008, 35, 401.
17 (a) J. Thisayukta, Y. Nakayama and J. Watanabe, Liq. Cryst.,
2000, 27, 1129; (b) K. Pelz, W. Weissflog and U. Baumeister,
Liq. Cryst., 2003, 30, 1151.
18 (a) J. Wang, L. Zou, A. Jakli, W. Weissflog and E. K. Mann,
´
Langmuir, 2006, 22, 3198; (b) N. Duff, L. Wang, D. J. Lacks and
E. K. Mann, Langmuir, 2006, 22, 9082; (c) N. Duff, E. K. Mann
and D. J. Lacks, Langmuir, 2008, 24, 4456; (d) L. Scheres,
R. Achten, M. Giesbers, L. C. de Smet, A. Arafat, E. J. R.
Sudholter, A. T. M. Marcelis and H. Zuilhof, Langmuir, 2009,
¨
25, 1529.
10 (a) C. D. Keum, A. Kanazawa and T. Ikeda, Adv. Mater., 2001, 13,
321; (b) K. Fodor-Csorba, A. Vajda, G. Galli, A. Jakli, D. Demus,
S. Holly and E. Gacs-Baitz, Macromol. Chem. Phys., 2002, 203,
1556; (c) S. S. Kwon, T. S. Kim, C. K. Lee, S. T. Shin, L. T. Oh,
E. J. Choi, S. Y. Kim and L. C. Chien, Bull. Korean Chem. Soc.,
2003, 24, 274; (d) A. C. Sentman and D. L. Gin, Angew. Chem., Int.
Ed., 2003, 42, 1815; (e) S. Rauch, C. Selbmann, P. Bault,
H. Sawade, G. Heppke, O. Morales-Saavedra, M. Y. M. Huang
and A. Jakli, Phys. Rev. E: Stat., Nonlinear, Soft Matter Phys.,
19 S. K. Lee, L. Shi, R. Ishige, S. Kang, M. Tokita and J. Watanabe,
Chem. Lett., 2008, 37, 1230.
20 D. Shen, A. Pegenau, S. Diele, I. Wirth and C. Tschierske, J. Am.
Chem. Soc., 2000, 122, 1593.
21 L. Engman, J. Ling and G. Merenyi, J. Phys. Chem., 1994, 98,
3174.
22 (a) J. Ortega, C. L. Folcia, J. Etxebarria, N. Gimeno and
M. B. Ros, Phys. Rev. E: Stat., Nonlinear, Soft Matter Phys.,
2003, 68, 011707; (b) J. Ortega, M. R. de la Fuente, J. Etxebarria,
C. L. Folcia, S. Diez, J. A. Gallastegui, N. Gimeno, M. B. Ros and
M. A. Perez-Jubindo, Phys. Rev. E: Stat., Nonlinear, Soft Matter
2004, 69, 021707; (f) J. Barbera, N. Gimeno, L. Monreal, R. Pinol,
´
M. B. Ros and J. L. Serrano, J. Am. Chem. Soc., 2004, 126, 7190;
(g) E. J. Choi, J. C. Ahn, L. C. Chien, C. K. Lee, W. C. Zin,
D. C. Kim and S. T. Shin, Macromolecules, 2004, 37, 3080;
(h) C. Keith, R. A. Reddy and C. Tschierske, Chem. Commun.,
Phys., 2004, 69, 011703; (c) J. Martınez-Perdiguero, I. Alonso,
´
C. L. Folcia, J. Etxebarria and J. Ortega, Phys. Rev. E: Stat.,
Nonlinear, Soft Matter Phys., 2006, 74, 031701.
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