Influence of fluoro substituents on the mesophase behaviour of banana-shaped molecules

Article abstract of DOI:10.1039/b201467j

Three new series of bent-shaped five-ring liquid crystals, based on the ester of isophthalic acid as the central core and azomethine linkages, are presented. They differ by the number and the position of halogeno substituents on the outer rings. This lateral substitution strongly influences the type of mesophases formed. Calculations were performed to determine the modification of the distribution of charge along the different molecules.

Full text of DOI:10.1039/b201467j

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Influence of fluoro substituents on the mesophase behaviour of
banana-shaped molecules
J. P. Bedel,a J. C. Rouillon,a J. P. Marcerou,a M. Laguerre,b H. T. Nguyena and
M. F. Achard*a
aCentre de Recherche Paul Pascal, Universite´ Bordeaux I, Av. A. Schweitzer, 33600 Pessac,
France. E-mail: achard@crpp.u-bordeaux.fr
bInstitut Europe´en de Chimie et Biologie, Ecole Polytechnique-Universite´ Bordeaux
I-Universite´ Bordeaux II- 16 Avenue Pey-Berland, 33607 Pessac, France
Received 8th February 2002, Accepted 3rd May 2002
First published as an Advance Article on the web 13th June 2002
Three new series of bent-shaped five-ring liquid crystals, based on the ester of isophthalic acid as the central
core and azomethine linkages, are presented. They differ by the number and the position of halogeno
substituents on the outer rings. This lateral substitution strongly influences the type of mesophases formed.
Calculations were performed to determine the modification of the distribution of charge along the different
molecules.
The influence of the alkyl or alkoxy terminal chains, which is
Introduction
often straightforward in calamitic mesogens, is not completely
evident in banana-shaped compounds. Nevertheless, in homo-
logous series, two or three different mesophases are observed
depending on the length of the terminal chains.2–11 In several
series,8,10,11 the short homologues present an intercalated
smectic ‘‘B6’’ and/or a two dimensional ‘‘B1 phase’’ and the
long chain derivatives show a switchable lamellar ‘‘B2 phase’’.
Other systems present a more complex evolution of the poly-
morphism depending on the length or on the nature of the
terminal chains.
Until recently, the observation of ferroelectricity in liquid
crystals, resulting in macroscopic electric polarization, was
restricted to materials with chiral molecular structure. But in
1996, ferroelectricity was observed under an electric field in
achiral compounds composed of bent molecules1 and since this
discovery, bent or ‘‘banana-shaped’’ liquid crystals have turned
into a major field of research.
These materials form several new liquid crystalline phases,
designated by the label B1–B82,3 and some of them exhibit
interesting ferro-or antiferroelectric properties although the
compounds are non-chiral. With exception of B3 and B4, all
the Bn mesophases present a lamellar organisation without
in-plane order. B2, B6, B8 can be considered as the analogues
of a ‘‘monolayer’’, ‘‘intercalated’’ and ‘‘bilayer’’ smectic
respectively. B2 and B8 present an ‘‘antiferroelectric type’’
response. B5 presents a similar response. B1 and B7 correspond
to more complex two-dimensional structures. In addition,
for B7 type mesophases, a helical superstructure is probable
but their complete structure is not solved. Note that this
nomenclature remains preliminary and there are strong
reasons to think that a ‘‘Bn’’ appellation constitutes a group
of mesophases, rather than an unique phase.
The liquid crystalline properties of the banana-shaped com-
pounds are also strongly influenced by the nature and position
of the lateral substituents. Thus, modifying the initial structure1
with a -COCH3, -C2H5 or -C6H13 group, attached at position
5 of the central phenyl ring (i.e. at the top of the molecule),
the mesomorphic properties disappear.2 With a chlorine12 or a
bromine13 atom at position 4, the ‘‘B2 phase’’ is preserved. The
introduction of a -CN group at position 4 gives rise to an
unusual SA–SC–B2 sequence.14 In contrast, the introduction of
a methyl or a nitro group on position 2 of the central ring
15
produces new mesophases (‘‘B5’’ for -CH3 and ‘‘B7’’ for
-NO216). These systematic studies were performed on the basis
of the same series and underline the importance of the lateral
substituents attached to the central ring.
The bent shape of these molecules results from a central
1,3-phenylene or 2,7-naphthylene unit and compounds with
five, six or seven aromatic (or heterocyclic) rings have been
synthesised.2 Nonetheless, most banana-shaped liquid crystals
reported up to now correspond to five-ring mesogens with a
1,3-phenylene central unit as shown in Chart 1.
The influence of substituents on the intermediate or outer
rings has been less studied.4,17–21 The first example of lateral
substitution on the terminal phenyl rings (with a fluorine atom)
was reported in a series with thiocarboxylic linkages:4 up to
On the basis of this general formula, different chemical
modifications can be considered and according to the available
data, each alteration can lead to a change in or even to the loss
of the liquid crystalline properties.
In particular, the influence of the nature, position and direction
of the linking groups appears very strong. For example, the
compounds in which the first ‘‘Bn’’ phases were discovered1
correspond to azomethine and carboxylic linkages with Y ~
-NLCH-, X ~ -COO-, X’ ~ -OOC-, Y’ ~ -CHLN- and the
simple inversion of the sense of Y (-CHLN-) and Y’(-NLCH-)
groups leads to the disappearance of these mesophases. We
noted that connecting groups corresponding to an alternating
distribution of the electronic density throughout the molecules
favour the liquid crystalline properties.4
Chart 1 General formula of five-ring banana molecules.
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DOI: 10.1039/b201467j

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four switchable banana phases, different from the referenced
Bn phases,22 were observed whereas the unsubstituted com-
pounds form nematic and smectic phases.
The products were recrystallized three times from ethanol–
toluene and twice from toluene–heptane. Yields: 30–50%.
The transition temperatures and associated enthalpies are
reported in Table 1. The phase assignment is based on comple-
mentary techniques, involving X-ray diffraction measurements
optical observations, miscibility studies with known reference
compounds and electro-optical analysis.
The goal of this paper is to systematically study the influence
of different halogeno substitutions on the outer phenyl rings
on the mesophase behaviour of banana-shaped compounds.
The basic structure corresponds to a series previously published
(‘‘Cn’’) which presents the same ‘‘B1’’ and ‘‘B2’’ phases5 as
the first reference series. The connecting groups are identical
and the molecular structure was modified by introducing a
fluorine atom at position 2 or 3 or two fluorine atoms at
positions 2 and 3 on the external phenyl rings. In the three
cases, complete homologous series with terminal alkoxy chains
varying from 7 to 14 methylene groups have been synthesised.
Substitution of a fluorine atom at position 2: DnF2 series
If a fluorine is attached at position 2 of the basic molecule a
large decrease in both melting and clearing temperatures is
observed and two types of mesophases exist depending on the
number of carbon atoms in the chains.
On cooling from the isotropic liquid, the phase of the short
homologues (n ~ 7–9) grows as dendritic nuclei which coalesce
and give a mosaic texture (Fig. 1a). X-Ray patterns present a
diffuse scattering at large angle and two incommensurate reflec-
tions in the small angle region suggesting a two-dimensional
B1 phase. According to a B1 assignment, one can assume a
rectangular lattice with a parameter ‘‘c’’ corresponding to the
layer thickness (from the (002) reflection) and a parameter ‘‘a’’
(from the (101) reflection) attributed to the in-plane periodicity
of the modulated phase. The X-ray data corresponds to a low
value of the ‘‘a’’ parameter corresponding to a lattice involving
few molecules.
The short chain homologues show neither polarisation current
nor texture change under field as expected for a ‘‘B1’’ phase.
The longer homologues (n ~ 10–12 and 14) exhibit the same
‘‘B2’’ phase as in the non-substituted series. An example of the
observed textures is given in Fig. 1b for the D11F2 compound.
The X-ray patterns of oriented samples (obtained by slow
cooling of a drop of the isotropic liquid) correspond to tilted
Results and discussion
Materials
All the compounds were prepared following the general
synthetic pathway shown in Scheme 1:
Isophthalaldehyde (0.1 mol) and 4-aminophenol (0.2 mol)
were dissolved in boiling absolute ethanol in presence of a few
drops of acetic acid. The solution was refluxed for 3 h. This
condensation led to 1,3-bis[4-hydroxyphenyliminomethyl]ben-
zene (compound 1), which was recrystallized three times from
a heptane–ethanol mixture.
To obtain the banana-shaped mesogens, the appropriate
benzoic acid (compound 2: 2 mmol) and compound 1 (1 mmol)
were treated in dichloromethane with dicyclohexylcarbodi-
imide (2.2 mmol) and 4-dimethylaminopyridine as catalyst.
The mixtures were stirred at room temperature for about 24 h.
Scheme 1 Synthetic pathway used to obtain the Cn, DnF2, DnF3 and DnF23 series of banana-shaped molecules. For each series, ‘‘n’’ corresponds to
the number of carbon atoms in the terminal alkoxy chains and varies from 7 to 14.
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Table 1 Transition temperatures (uC) and enthalpies (italics, kJ mol21) as a function of the carbon atoms number in the terminal chains (from DSC
runs, increasing temperature, rate 5 uC min21). As usually observed in banana compounds, the enthalpy changes corresponding to the clarification
transition are larger than for classical rod-like liquid crystals
n
Cn
K
DnF2
K
DnF3
K
DnF23
7
8
9
9
128.4
28.7
120.9
29.2
121.3
32.0
B1
B1
B1
152.9
17.2
153.5
18.2
147.2
18.8
I
I
I
120.4
17.3
B1
B1
B1
122.7
13.3
124.0
17.1
119.9
16
I
I
I
109.5
26.9
B1x
B1x
163.8
23
162.1
23.4
I
I
K
K
139.5
B1x
B1x
165.8
19.4
163.1
20.3
I
I
25.6
141.1
22.7
K
K
103.5
30.3
K
111.8
33.4
K
K
100.7
35.9
K
K
K
K
K
112.8
32.9
111.5
33.9
111.7
34.8
111.0
31.7
110.7
48
B7bis
B7bis
B7bis
B7bis
B2
160.3
22.9
158.9
22.7
158.3
23.5
157.0
22.7
156.6
23
I
I
I
I
I
K
K
K
K
138.7
26.2
137.6
24.6
137.0
24.6
136.2
26.9
B7bis
B7bis
B7bis
B7bis
162.0
22.0
161.8
22.4
162.3
22.6
162.5
23.9
I
I
I
I
10
11
12
13
K
K
K
K
120.4
33.6
117
37.4
115
41.4
116.7
72
B2
B2
B2
B2
148.9
20.1
149.9
21.1
151
22.3
151.9
23.2
I
I
I
I
K
K
K
101.2
30.5
99.2
30.4
100.3
23.5
B2
B2
B2
123.8
18.4
126.1
19.5
129.2
20.8
I
I
I
14
K
114.8
68.5
B2
150.4
23.1
I
K
97.0
28.1
B2
131.0
22.2
I
K
110.0
50
B7bis
155.4
22.7
I
K
133.6
25.8
B7bis
161.1
23.8
I
aK: crystalline phase, I: isotropic liquid. For liquid crystalline phase identification, see text. bThe chloro derivatives DnCl3 present the same
mesophases as DnF3, but the transition temperatures are lowered: for example, K 82 uC B7bis 139 uC I for D12Cl3 compound.
smectics. The strong Bragg reflection in the small-angle region,
with two harmonics reveals a layer structure (Fig. 2). The layer
normal (meridian) is parallel to the drop axis. The diffuse
scattering maxima in the wide-angle region indicate a liquid-
like order within the layer and the tilt of the molecules with
respect to the layer normal. This tilt angle (32u) appears
significantly lower than for the non-substituted Cn series (42u).
Surprisingly, the layer spacing is also smaller in the DnF2 series
than in the Cn one (Table 2). This suggests a different
arrangement of the molecules in the B2 phase, involving a
larger interpenetration of the terminal chains in the fluorine
substituted DnF2 compounds.
under the application and the removal of the field between a
non-polar and a polar phase (Fig. 3). The optical texture also
changes after the threshold leading to two different figures with
or without applied field. Note that there is no big difference
between the textures at 2V and 1V unlike in a calamitic chiral
smectic where the tilt angle flips from one direction to another.
To sum up, the introduction of a fluorine atom at position 2
on the outer phenyl rings of the banana-shaped molecules does
not change the mesomorphism but causes a strong reduction of
the mesophase stability in comparison with non-substituted
compounds.
Substitution of a fluorine atom at position 3: DnF3 series6
On applying a sufficiently high electric field (after a threshold
of 8 V mm21), the long homologues react like a ‘‘B2 phase’’ with a
two-peak polarisation response indicating the phase transitions
At the opposite, the introduction of a fluorine atom at position
3 on the external phenyl rings increases the stability of the
Fig. 2 X-Ray pattern of an oriented sample of D11F2 compound in the
B2 phase.
˚
Table 2 Linear increase of the layer spacing/A versus the carbon
number in the terminal chains. One can note a significant difference
between the two series, which only differ by a fluorine substituent in
position 2 of the outer phenyl rings
n
10
11
12
14
Cn series
DnF2 series
36.10
33.40
37.45
34.90
38.80
36.10
41.40
38.75
Fig. 1 a) Texture of the B1 phase of compound D9F2 (118 uC) b)
Texture of the B2 phase of compound D11F2 (125 uC).
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Fig. 5 Microscopic textures of the B1x mesophase of D8F23
compound (161 uC).
Fig. 3 Switching current response in the B2 phase of D12F2, obtained
by applying a triangular voltage (¡100 V; sample thickness 3.5 mm).
the threshold 10 V mm21. No significant variation is observed
versus temperature in the mesophases.
mesophase both by the decrease of the melting point and by
an unusual enhancement of the clearing temperatures (see
Table 1).
Substitution of two fluorine atoms at positions 2 and 3: DnF23
series
The short chain homologues (n ~ 7–8) exhibit a two-
dimensional ‘‘B1x’’ phase which is structurally different
from the two-dimensional B1 phase with a rectangular lattice
observed in the non-substituted Cn compounds. The four
incommensurate reflections in the small angle region are com-
patible with a rectangular centred lattice. Nevertheless, as for
a B1 phase, the B1x mesophase shows again neither polarisa-
tion current nor texture change under electric field.
By introducing two fluorine atoms at positions 2 and 3, the
influence of the substitution on position 3 prevails and as
for the DnF3 series, the ‘‘B1x’’ phase is observed for short
homologues (n ~ 7, 8) and the long homologues present
a ‘‘B7bis’’ mesophase. In this DnF23 series, the clearing
temperatures are higher than those of the non-substituted
compounds but one can note in Table 1 the increase of the
melting temperatures. Examples of the microscopic textures for
both B1x and B7bis mesophases are given in Fig. 5a and 6.
The X-ray pattern of the B1x phase shows four reflections
The longer homologues (n ~ 9 to 14) exhibit a ‘‘ B7’’ variant,
labelled ‘‘B7bis’’ phase. As for the original ‘‘B7’’ observed in
nitro-substituted compounds,16 this B7bis phase presents a large
variety of beautiful textures at the transition from the isotropic
liquid and a complex X-ray pattern in the small angle region
which excludes a simple layered organisation and suggests a
two-dimensional structure. But in contrast to the original B7, it
does have a polarisation response under applied field (Fig. 4) .
This response appears after a rather high threshold of about
10 V mm21 and is constituted of only ‘‘one peak’’ per half
period (i.e. a ‘‘ferroelectric type’’). This means that the
polarised phase created by the field has a long lifetime, so
that it does not revert back to the zero-field non-polar phase
when the field switches back and forth between 2V and V. As
evidenced in Fig. 4 with a ‘‘triple plateau’’ voltage where V goes
smoothly between three plateaux at 2100 V, 0 V and 1100 V,
the polarisation has a lifetime greater than 10 ms and never
vanishes in these conditions. It just rotates at constant modulus
from 2P to 1P as in classical ferroelectric phases. When the
field is switched off, the reverse phase transition to a non-polar
phase takes place.
21
21
21
˚
˚
˚
in the small-angle region (q ~ 0.078 A , 0.150 A , 0.163 A
21
˚
0.307 A for D8F23) as for DnF3 compounds and a diffuse
scattering at wide angles indicates the liquid like order of this
mesophase.
In the same way, the long chain members of the DnF23 series
present X-ray patterns similar to the DF3 series (Fig. 7).
The behaviour under electric field is similar to that of the
DnF3 series. No response is observed for the B1x phase. For
the B7bis phase, the field induces first the transition to a long-
lived polar phase (i.e. a ‘‘one peak’’ response) after a threshold
at about 12 V mm21 as before. Nevertheless, contrary to the
DnF3 series, at a second threshold of about 20 V mm21, this
‘‘one peak’’ response changes progressively in a few minutes
into a ‘‘two peaks’’ one , indicating the transition with a short-
lived polarisation (Fig. 8). The apparent polarisation is about
360 nC cm22 for D11F3. This smooth transition is accom-
panied by a progressive change in the texture.
The examples shown in this paper give evidence of the subtle
relationship between the chemical structure and mesomorphic
properties of banana compounds. The introduction of a lateral
fluorine substituent at position 3 on the terminal phenyl rings,
which seems a priori a minor modification, leads to a drastic
change in the mesomorphic behaviour since a two-dimensional
‘‘B7bis’’ mesophase is observed instead of a layered ‘‘B2 phase’’.
In the same way, a chlorine atom at position 3 or two fluorine
atoms at positions 2 and 3 also induce a ‘‘B7bis’’ mesophase,
while a lateral fluorine substituent at position 2 preserves the
‘‘B2’’ phase.
The polarisation value is between 300 and 380 nC cm22 for
the long homologues, the typical response time 100 ms and
It is clear that the molecular organisation of bent-shaped
compounds results in a complex balance between the electro-
static interactions and the van der Waals interactions
developed by the aliphatic chains. Thus the distribution of
the electrostatic potential extrema{ along the molecule will
{The electrostatic potential was calculated by VSS methods on lowest-
energy conformers found after Monte-Carlo space conformation
studies. Charge calculations were performed by using the MOPAC
semi-empirical package with MNDO method.
Fig. 4 Switching current response in the ‘‘B7bis phase’’ of D10F3,
obtained by applying a modified triangular voltage ( ¡100 V; sample
thickness 5.4 mm; T ~ 120 uC).
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Fig. 6 Examples of the B7bis textures of the long homologues of the DnF23 series: a, ‘‘banana-tree leaves’’; b, different kinds of spiral germs
indicating helicoidal structure; c, ribbons with equally spaced lines and d, two-dimensional periodic patterns.
Fig. 7 X-Ray pattern in the low-angle region of a non-oriented
21
21
˚
˚
D9F23 sample: several reflections are seen (q ~ 0.048 A , 0.158 A
,
0.302 A 0.322 A21 ) but the structure cannot be determined without
an oriented sample. Note that, increasing the chain length, the weaker
reflections vanish and as for a smectic phase, an intense reflection with
its first harmonic only is detected.
21
Fig. 8 Switching current response in the ‘‘B7bis phase’’ of D14F23,
obtained by applying a modified triangular voltage (sample thickness
3.6 mm; T ~ 136 uC): a) V ~ ¡ 58 V (below the second threshold), b),
c), d) evolution with time at a voltage V ~ ¡71 V corresponding to the
second threshold.
˚
˚
strongly influence the molecular arrangement and the nature
of the mesophases. Fig. 9 shows this repartition along a branch
of the banana compounds. The presence of the halogeno
substituents on the outer rings modifies the distribution of the
potential extrema (Table 3): within the DnF3 and Cn series,
there appears a very contrasted pattern of negative extrema
distributed along the branch, while there remains only a very
deep negative extremum around the outer carboxylate moiety
within the DnF2 series.
In the DnF2 series, the fluorine substitution at position 2
considerably increases the electrostatic potential and equalises
Table 3 Maximum values of the calculated electrostatic potential (kcal mol21) on the different parts of the molecule
Series Site
Cn
DnF2
DnF3
DnCl3
DnF2,3
Central ring
CHLN
Intermediate ring
25
225
229
229
230
254
215
217
23
224
215
220
248
0
24
225
28
219
250
0
224
227
226
228
248
27
226
218
222
253
25
O
CLO
Outer ring
O at the end of the branch
222
230
228
225
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Scheme 3 Reagents and conditions: a: CnH2n11Br, K2CO3, acetone; b:
Br2, NaOH, dioxane.
Oriented samples of the smectic phases were obtained by slow
cooling of a drop of the isotropic liquid.
Fig. 9 Distribution of the electrostatic potential along a ‘‘branch’’ of
banana compounds.
Electro-optical properties were studied using commercial
cells (from E.H.C., Japan) with rubbed polyimide layer (but
the surface treatment is not effective to make uniformly
oriented cells).
Switching current was observed by applying a voltage-wave
using a function synthesizer (HP 331 20A ) and an high power
amplifier (Krohn-Hite ).
the negative charges from the centre of the molecule to the
ester linkage. Thus, by comparison with the non-substituted Cn
series, the existence of a ‘‘B2 phase’’ does not depend on the
repartition of the negative potential in the central part of the
molecule. Moreover, the small difference of charges between
the outer ring and the extremity favours the interpenetration of
the aliphatic chains.
Synthesis of the benzoic acids (compounds 2):
It is clear that the presence of a fluorine (or chlorine) atom at
position 3 in the series DnF3 (or DnCl3) only slightly reduces
the electrostatic potential around the Schiff base and the ester
group but largely reinforces the negative potential between the
fluorine substituted phenylene group and the alkoxy group.
The DnF23 series constitutes an intermediate case: an increase
and an equalisation of the charges in the central part of the
molecule is observed as for the DnF2 series, and the difference
between the outer ring and the terminal group is kept as for the
substitution at position 3.
The 2-fluoro-4-alkoxybenzoic acids were prepared according to
the method shown in Scheme 2.23
The 3-fluoro-4-alkoxybenzoic acids (compounds 2) were
prepared according to the method shown in Scheme 3.24
The 2,3-difluoro-4-alkoxybenzoic acids were prepared
according to the method shown in Scheme 4.25
Analytical data
These small differences are able to induce different molecular
arrangements and thus different mesophases. It is obvious that
the relationship between chemical structure and mesomorphic
behaviour is a complex problem and that our understanding is
still at an early stage.
1,3-Bis[4-(3-dodecyloxybenzoyloxy)phenyliminomethyl]benzene
(compound C12). 1H NMR (200 MHz, CDCl3) d (ppm): 8.6
(2H, s, CHLN), 8.4 (1H, s, Ar-H), 8.13–8.18 (4H, d, Ar-H),
8.05–8.09 (2H, d,Ar-H), 7.6 (1H, t, Ar-H), 7.2–7.35 (8H, m,
Ar-H), 6.95–7.00 (4H,d, Ar-H), 4.05 (4H, t, O-CH2), 1.8–1.85
(4H, m, O-CH2-CH2), 1.25–1.5 (36H, m, CH2), 0.85–0.92
(6H, m, CH3).
IR (KBr) n/cm21: 2920, 2851, 1726, 1606, 1509, 1472, 1289,
1254, 1193, 1170, 1086, 884, 852, 762, 683.
3. Experimental
Elemental analysis: calculated: C: 78.03%; H: 8.07%; N:
3.14%. Found: C: 77.59%; H: 8.22%; N: 3.17%.
The thermal behaviour was investigated using a Perkin-Elmer
DSC7 differential calorimeter. The optical textures of the
mesophases were observed through a polarizing microscope
(Leitz Diavert) equipped with a hot stage (FP-82HT) and an
automatic controller (Mettler FP-90). Samples were observed
on regular slide glass without any surface treatment.
1,3-Bis[4-(2-fluoro-4-tetradecyloxybenzoyloxy)phenylimino-
D
14F2). 1H NMR (200 MHz,
methyl]benzene (compound
X-Ray diffraction experiments were carried on a 18 kW
rotating anode X-ray source (Rigaku-200) with use of a
Ge(111) crystal as monochromator. The scattered radiation
was collected on a two dimensional detector (Imaging Plate
system from Mar Research, Hamburg). The samples were
placed in an oven, providing a temperature control of 0.1 K.
Scheme 2 Reagents and conditions: a: CnH2n11Br, KOH, EtOH; b:
CH3COCl, FeCl3, CH2Cl2; c: Br2, NaOH, dioxane.
Scheme 4
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CDCl3) d (ppm): 0.85–0.9 (m, 6H ,m, CH3), 1.3 (m, 44H,
22CH2), 1.8 (m, 4H, 2 O-CH2-CH2), 4.05 (t, 4H, 2 O-CH2),
6.65–6.8 (m, 4H, Ar-H), 7.25–7.35 (m, 8H, Ar-H), 7.6 (t, 1H,
Ar-H), 8.1 (m, 4H, Ar-H), 8.4 (s, 1H, Ar-H), 8.6 (s, 2H,
CHLN).
Elemental analysis: calculated: C: 75.61%; H: 7.93%; N:
2.84%; F: 3.86%. Found: C: 75.38 %; H: 7.98 %; N: 2.89 %;
F: 3.59 %.
5
6
7
8
9
A. Maranatha and B. K. Sadashiva, Liq. Cryst., 2000, 27, 1613.
1,3-Bis[4-(3-fluoro-4-tetradecyloxybenzoyloxy)phenylimino-
D
14F3). 1H NMR (200 MHz,
10 J. C. Rouillon, J. P. Marcerou, M. Laguerre, H. T. Nguyen and
M. F. Achard, J. Mater. Chem, 2001, 11, 2946.
11 W. Weissflog, I. Wirth, S. Diele, G. Pelzl and H. Schmalfuss, Liq.
Cryst., 2001, 28, 1603.
12 G. Pelzl, S. Diele, S. Grande, A. Jakli, C. Lischka, H. Kresse,
H. Schmalfuss, I. Wirth and W. Weissflog, Liq. Cryst., 1999, 26,
401.
13 H. Dehne, M. Po¨tter, S. Sokolowski, W. Weissflog, S. Diele,
G. Pelzl, I. Wirth, H. Kresse and S. Grande, Liq. Cryst., 2001, 28,
1269.
methyl]benzene (compound
CDCl3) d (ppm): 0.85–0.9 (m, 6H, 2CH3), 1.25–1.5 (m, 44H,
22CH2), 1.8 (m, 4H, 2 O-CH2-CH2), 4.1 (t, 4H, 2 O-CH2), 7.1
(t, 2H, Ar-H), 7.22–7.34 (m, 8H, Ar-H), 7.6 (t, 1H, Ar-H),
7.88–8.05 (m, 6H, Ar-H), 8.4 (s, 1H, Ar-H), 8.6 (s, 2H, CHLN).
Elemental analysis: calculated: C: 75.61%; H: 7.93%; N:
2.84%; F: 3.8 %. Found: C: 75.84%; H: 7.98%; N: 2.93%;
F: 3.68%.
14 W. Weissflog, L. Kovalenko, I. Wirth, S. Diele, G. Pelzl,
H. Schmalfuss and H. Kresse, Liq. Cryst., 2000, 27, 677.
15 S. Diele, H. Grande, H. Kruth, C. Lischka, G. Pelzl, W. Weissflog
and I. Wirth, Ferroelectrics, 1998, 212, 169.
16 G. Pelzl, S. Diele, A. Jakli, C. Lischka, I. Wirth and W. Weissflog,
Liq. Cryst., 1999, 26, 135.
17 B. K. Sadashiva, H. N. Shreenivasa Murthy and Surajit Dhara,
Liq. Cryst., 2001, 28, 183.
18 R. Amaranatha Reddy, B. K. Sadashiva and Surajit Dhara, Chem.
Commun., 2001, 1972.
1,3-Bis[4-(2,3-difluoro-4-tetradecyloxybenzoyloxy)phenylimi-
nomethyl]benzene (compound D14F2,3.
1H NMR (200 MHz,
CDCl3) d (ppm): 0.85–0.9 (m, 6H, 2CH3), 1.25–1.5 (m, 44H,
22CH2), 1.8 (m, 4H, 2 O-CH2-CH2), 4.15 (t, 4H, 2 O-CH2),
6.85 (m, 2H, Ar-H), 7.3 (m, 8H, Ar-H), 7.6 (t, 1H, Ar-H), 7.85
(m, 2H, Ar-H), 8.05 (d, 2H, Ar-H), 8.4 (s, 1H, Ar-H), 8.6 (s, 2H,
CHLN).
19 G. Heppke, D. D. Parghi and H. Sawade, Ferroelectrics, 2000, 243,
269.
References
20 C. K. Lee and L. C. Chien, Ferroelectrics, 2000, 243, 231.
21 W. Weissflog, H. Nadasi, U. Dunemann, G. Pelzl, S. Diele,
A. Aremin and H. Kresse, J. Mater. Chem., 2001, 11, 2748.
22 J. P. Bedel, J. C. Rouillon, J. P. Marcerou, M. Laguerre,
H. T. Nguyen and M. F. Achard, submitted.
23 H. T. Nguyen, A. Babeau, J. C. Rouillon, G. Sigaud, N. Isaert and
F. Bougrioua, Ferroelectrics, 1996, 79, 33.
24 M. F. Nabor, H. T. Nguyen, C. Destrade, J. P. Marcerou and
J. Twieg, Liq. Cryst., 1991, 10, 785.
25 S. M. Kelly, Helv. Chim. Acta, 1989, 72, 594.
1
2
3
4
T. Niori, T. Sekine, J. Watanabe, T. Furukawa and H. Takezoe,
J. Mater. Chem., 1996, 6, 1231.
See for example: G. Pelzl, S. Diele and W. Weissflog, Adv. Mater.,
1998, 11, 707 and references therein.
J. P. Bedel, J. C. Rouillon, J. P. Marcerou, M. Laguerre,
H. T. Nguyen and M. F. Achard, Liq. Cryst., 2001, 28, 1285.
H. T. Nguyen, J. C. Rouillon, J. P. Marcerou and P. Barois,
International Conference On Liquid Crystals, Strasbourg, 1999
(D2-O3); H. T. Nguyen, J. C. Rouillon, J. P. Marcerou, J. P. Bedel,
2220
J. Mater. Chem., 2002, 12, 2214–2220