Star-shaped oligobenzoates with a naphthalene chromophore as potential semiconducting liquid crystal materials?

Article abstract of DOI:10.1039/b803000f

A series of star-shaped non-C₃-symmetrical mesogens containing one naphthalene chromophore at a defined position have been synthesised to study the influence of phase symmetry and nano-segregation on the order of the chromophores and their inte

Full text of DOI:10.1039/b803000f

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PAPER
www.rsc.org/materials | Journal of Materials Chemistry
Star-shaped oligobenzoates with a naphthalene chromophore as potential
semiconducting liquid crystal materials?†
a
Matthias Lehmann, Michael Jahra and Jochen Gutmannbc
*
Received 20th February 2008, Accepted 24th April 2008
First published as an Advance Article on the web 27th May 2008
DOI: 10.1039/b803000f
A series of star-shaped non-C3-symmetrical mesogens containing one naphthalene chromophore at a
defined position have been synthesised to study the influence of phase symmetry and nano-segregation
on the order of the chromophores and their interactions in potential semiconducting materials.
Structural investigations reveal a rich mesomorphism from columnar hexagonal, columnar
rectangular, lamellar to cubic phases depending on the type of oligobenzoate arms attached to the core.
Although the decoration of the naphthalene containing arm with peripheral semi-perfluorinated chains
results in a confinement of the chromophores to the interface between cores and perfluorinated units,
the naphthalenes do not strongly interact among themselves as evidenced by the photophysical studies.
The latter is attributed to the E-shaped conformer and the increased intra-columnar separation owing
to the fluorinated chains.
different arms. Many molecules are known with C3-symmetry,
Introduction
owing to the great number of C3-symmetric cores. They form
Non-conventional mesogens are currently of enormous interest
liquid crystal (LC) structures if the peripheral chains are
owing to their amazing self-assembly into complex soft mate-
adequately selected.7–15 Thereby, a great variation in thermo-
rials.1 Among these molecules are for example dendrimers2 and
tropic phases can be found from nematic, to lamellar, to
dendrons,3,4 which do not possess any shape anisotropy, but
columnar structures, which depends on the fine-tuning of the
nevertheless organise by nano-segregation of the chemically and/
core scaffold and the number, preorganisation and type of
or physically different building blocks.1,5 Incorporation of
peripheral flexible chains. Recently, we have shown that
chromophores into such scaffolds introduces functions and thus
symmetrical oligobenzoate star-shaped mesogens, with a phlor-
may transform these compounds into organic semiconductors4
oglucinol core and peripheral dodecyloxy chains form various
or light harvesting molecules.6 One fascinating type of material,
columnar mesophases.15,16 In the low-temperature columnar
which was designed following nature’s example in the tobacco
phases, the individual columns are correlated with each other in
mosaic virus, are dendrons, possessing a chromophore on the
3D assemblies, owing to undulation which is attributed to
focal point and peripheral semi-perfluorinated flexible chains.4
a helical packing of folded, E-shaped conformers. Naphthalene
The chains are known to be incompatible with the other
was chosen as a chromophore for two reasons: first, it is suffi-
molecular units and, thus, the molecules self-organise in helical
ciently small, thus it is expected not to alter the self-organisation
columns by nano-segregation of the chromophores in the centre
process; and second, because naphthalene derivatives are known
of the column. Owing to the good charge carrier mobility and the
for their excellent charge carrier mobilities in crystals, liquid
simple design, these materials are of interest for plastic
crystals and polymers.17–20 Indeed, incorporation of a naphtha-
electronics. Note that the latter molecules assemble the chro-
lene in each individual oligobenzoate arm does not in principle
mophores only in the last step by supramolecular interactions. A
change the self-assembly compared with the parent oligo-
different concept can be pursued if chromophores are preor-
benzoates.16 Moreover, preliminary measurements of the charge
ganised in a single molecule and the superstructure is built in the
carrier mobility by the electrode-less PR-TRMC technique
second step, as observed for peptides and DNA.
revealed a very high value of up to 0.09 cm2 Vꢀ1 sꢀ1, which is
Our interest focussed on three-armed star-shaped compounds
similar to that of hexahexylsulfanyltriphenylene, one of the most
which can be in principle tailor-made by attaching up to three
efficient triphenylene derivatives.21 In the present investigation,
we aim to study the structural requirements for semiconducting
aInsitute of Chemistry, Chemnitz University of Technology, Straße der
Nationen 62, 09111 Chemnitz, Germany. E-mail: Matthias.Lehmann@
chemie.tu-chemnitz.de; Fax: (+) 49/371 531 21229; Tel: +49 371 531
31205
materials, i.e. the influence of the mesophase structure and nano-
segregation on the order of chromophores. Therefore, we
synthesised non-C3-symmetric mesogens with one naphthalene
bMax-Planck Institute for Polymer Research, Ackermannweg 10, 55128
Mainz, Germany
cInstitute of Physical Chemistry, Johannes-Gutenberg University Mainz,
Welderweg 11, 55099 Mainz, Germany
chromophore attached to the phloroglucinol core, by a previ-
ously reported strategy.22 The oligobenzoate arms are different in
length and one of the molecules possesses semi-perfluorinated
chains on the arm where the chromophore is incorporated.
Desymmetrisation was proposed to alter the shape of the
mesogens and consequently the mesophase structure. The
† This paper is part of a Journal of Materials Chemistry theme issue on
Liquid Crystals Beyond Display Applications. Guest editor: Carsten
Tschierske.
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semi-perfluorinated lateral chains are strongly segregating, thus,
we expect that chromophores attached to these building blocks
are confined to the interface of perfluorinated chains and the
benzoate core which might result in defined chromophore stacks.
Here, we report the synthesis, LC characterisation and photo-
physical properties of non-C3-symmetrical star-shaped mesogens
1 containing one naphthalene chromophore (Fig. 1).
Synthesis
The synthesis of the C2-symmetric star molecule 1a starts with
a twofold benzyl protected phloroglucinol as shown in Scheme 1
(Route A). Esterification with acid 3c, cleavage of the protecting
group and final esterification of the two newly formed phenolic
OH groups with arm 3b yielded molecule 1a. Compound 1b was
prepared by a different process (Route B) to avoid the more
difficult work-up, when semi-perfluorinated alkyl chains are
present in the molecule. A mono-protected phloroglucinol was
first coupled to the oligobenzoate arms 3b by a twofold esterifi-
cation. Cleavage of the benzyl ether and subsequent coupling of
the arm 3d, bearing the naphthalene chromophore and lateral
perfluorinated chains, provided mesogen 1b in good yield and
high purity. Mesogens with three different arms have been
synthesised as reported previously, by using a newly designed
ABC building block.22 The five step synthesis affords the prod-
ucts 1c and 1d after a series of coupling and deprotection steps
(Scheme 1, Route C).
Thermotropic properties
The thermotropic properties were studied by polarised optical
microscopy (POM) and differential scanning calorimetry (DSC)
and the results are summarised in Table 1. All materials show
liquid crystal phases from room temperature to their clearing
point. The latter is a function of the number of benzoate
repeating units, as was already observed for the C3-symmetric
mesogens. For example compounds 1a and 1d with the same
Scheme 1 Synthesis of star-shaped mesogens 1.
Fig. 1 Star-shaped mesogens 1.
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Table 1 Mesomorphic properties of 1a–c: DSC results from the second
heating and the first cooling cycles (heating rate 10 ꢁC minꢀ1
)
a
Compound
Onset [ꢁC]/DH [kJ molꢀ1
]
1a
1b
1c
1d
Colhd 65.1/4.4 I
I 60.7/ꢀ4.4 Colhd
Colrd 151.9/1.6 SmA 190.9/2.2 I
I 190.0/ꢀ1.9 L 151.1/ꢀ1.5 Colrd
Colhd 43.2/4.8 I
I 34.5/ꢀ4.8 Colhd
Cub 60.6/2.3 I
I 46.1/ꢀ2.3 Cub
a
Colhd columnar hexagonal LC phase, Colrd columnar rectangular LC
phase (p2mg, see X-ray section), SmA smectic A (lamellar) phase, Cub
cubic LC phase, I isotropic phase.
number of repeating units show clearing temperatures in the
same temperature range (61–65 ꢁC), whereas 1c with one
benzoate group less clears at a 20 ꢁC lower temperature. An
exception is compound 1b, because the strong interactions
between the semi-perfluorinated chains increase the transition
ꢁ
temperature to the isotropic phase by more than 135 C. POM
Fig. 3 A,B: X-Ray diffraction patterns of extruded fibres. Compound 1a
in its Colh phase at 40 ꢁC (A) and compound 1b in its Colrd phase (p2mg)
at 70 ꢁC (B). The framed diffuse reflections on the meridian correspond to
the average separation of the mesogens along the column. C, D:
Diffraction pattern of 1d in the Cub phase at 40 ꢁC (C) and the magni-
fication of the small angle region (D).
observations reveal typical pseudo-focal conic textures for 1a, 1b
and 1c indicating a columnar nature of the mesophases (Fig. 2).
Compound 1d presents only an optical isotropic texture pointing
to a cubic phase. The low viscous, high-temperature mesophase
of 1b exhibit also an optical isotropic phase when sandwiched
between glass plates, but a sample prepared without a cover sheet
becomes birefringent. These observations indicate a lamellar
phase. The dark texture of the sample between two glass slides is
observed even upon rotation of the sample and shows the
homeotropic alignment of a uniaxial LC phase. Fig. 2B reveals
that planar aligned columns can be uniformly grown upon slow
cooling from the lamellar phase. These features are evidence
against an LCol (lamellar columnar) phase and point rather to
a SmA type lamellar phase.
X-Ray diffraction studies and structure of the
mesophases
X-Ray diffraction on aligned samples reveals the columnar
structure of the mesophases of 1a–c. Fig. 3 exhibits typical wide
angle patterns with fibres of 1a and 1b aligned parallel with the
meridian. The reflections on the equator can be attributed to
a two-dimensional order of columns, whereas the intense but
diffuse meridional signals at the halo indicate the intra-columnar
average separation of the mesogens. The data are collected in
Table 2. The reciprocal d-spacings of the equatorial reflections of
1a and 1c are in the ratio 1 : O3 : 2, thus clearly showing the
hexagonal packing of columns. In contrast, the diffraction
pattern of 1b exhibits a large number of equatorial reflections,
which could be resolved in the small angle X-ray studies (Fig. 4).
The least-squares fit of the signals reveals a rectangular phase
˚
˚
with a ¼ 44.7 A and b ¼ 81.0 A. The indexation of the reflections
can be performed according to the plane group p2mg with the
reflection conditions hk: no conditions; h0: h ¼ 2n (Table 2). The
broad meridional peaks on the halo disclose the intra-columnar
spacing of the mesogens. Whereas there is an average intra-
˚
columnar separation of 4.5 A for the mesogens exclusively
decorated with alkyl chains (1a, 1c), the separation increases for
1b owing to the larger semi-perfluorinated chains. For the high-
temperature phase of 1b, the alignment was lost at the phase
transition because of the low viscosity and the subsequent
deformation of the fibre sample. The two reflections at small
Fig. 2 Textures of the liquid crystal phases of 1a–c. A: Pseudo-focal-
conic texture of 1a at 63.8 ꢁC. B: Pseudo-focal-conic texture (bottom
right) and planar alignment (top left) of 1b at 158 ꢁC. C, D: Pseudo-focal-
conic texture (C) and mosaic texture (D) of 1c at 39.5 ꢁC.
˚
angles support a SmA phase with a lamella thickness of 75.5 A,
which compares well with the b parameter of the rectangular
phase. However, the shrinkage is incompatible with the increase
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Table 2 Structural data of the columnar mesophases
a
VM /A
3
3
˚
˚
hk; dexp/A; dcalc/A
˚
˚
a/A
˚
b/A
˚
halo (meridian)/A
˚
Vcell/A
Compound
T/ꢁC
Phase
Colh
Z
Density/g cmꢀ3
0.98
1a
60
10; 36.8; 36.8
11; 21.2; 21.2
20; 18.5; 18.4
02; 35.7; 37.5b
03; 26.6; 25.2
01; 80.7; 81.0
02; 40.9; 40.5
11; 39.1; 39.2
12; 30.1; 30.0
03; 27.3; 27.0
10; 34.6; 34.6
11; 19.3; 20.0
20; 17.3; 17.3
4236
42.5
—
4.5
6945
18841
6082
1.6
1b
1b
165
70
SmA
Colrd
—
75.5b
81.0
5.3
5.2
4615
4033
44.7
4.1
1.5
1.23
0.98
1c
40
Colh
40.0
—
4.4
a
The molecular volume was calculated following reference 23. The obtained value was corrected by a factor using the experimental dilatometry data.16
Broad reflections in the small angle region of the WAXS pattern. The value b was therefore calculated with b ¼ (2d02 + 3d03)/2.
b
only slightly from the molecular structure of the parent oligo-
benzoate. In 1a one benzene unit of the parent star is substituted
by naphthalene. The unit cell parameters of both Colh phases are
almost identical (Table 2).15,16 This indicates a very similar
supramolecular organisation. Table 2 also shows the calculated
molecular volume, the number of molecules per columnar unit
and the density. All these values are nearly matching the previ-
ously reported data of the parent oligobenzoate, and thus
indicate a closely related structure. Therefore, we propose that
E-shaped mesogens 1a self organise in columnar stacks by nano-
segregation of their nonpolar aliphatic chains and the polar
oligobenzoate cores. The characteristic parameters for the
hexagonal mesophase of 1c (Table 2) and the similar molecular
structure compared with 1a indicate an analogous model for the
mesophase of the small star molecule. Interestingly, although all
Fig. 4 SAXS of 1b in the Colrd phase at 70 ꢁC; integration of the
symmetric star-shaped oligobenzoates have been shown to
transform to ordered columnar phases at low temperatures with
a helical supramolecular aggregation of mesogens,16 such
a transition is missing for the desymmetrised stars 1a and 1c. This
suggests that desymmetrised mesogens prevent the formation of
a highly ordered mesophase, and consequently a statistical
orientational distribution of the naphthalene chromophores
around the columnar axis remains at room temperature.
equatorial reflections. The reflections can be indexed according to
˚
˚
a rectangular phase in the plane group p2mg (a ¼ 44.7 A, b ¼ 81.0 A),
which is indicated by the missing 10 reflection (2q ¼ 1.98ꢁ).
ꢁ
of temperature by 100 C. Thus, the expansion must consist of
increasing distances within the layers, which allows fast molec-
ular motions of single molecules or aggregates and consequently
the formation of a uniaxial SmA phase. Fig. 3C and D present
the WAXS diffraction pattern of 1d and its expansion of the
small angle region. No alignment was observed by fibre extru-
sion. The relatively intense discrete reflections are obtained only
upon slow cooling from the isotropic phase without shearing the
sample. This behaviour is typical for cubic phases. A mono
domain could not be grown, which prevented more detailed
characterisation.
A different model has to be considered for the phases of
compound 1b. The rectangular phase can be assigned to a plane
group with p2mg symmetry owing to the missing 10 reflection
(Fig. 4). The relatively small unit cell parameters point again to
a compact LC building block, such as an E-shaped mesogen.
Fig. 5 shows a model of the phase. A pair of antiparallel aligned
E-shaped mesogens constitutes the building block of the
columnar phase. This unit exposes the semi-perfluorinated chains
only to one side of the assembly. Consequently, the semi-per-
fluorinated chains of different columns can nano-segregate along
the a direction of the unit cell. Thereby, the columns interdigitate
similarly to the teeth of two gear wheels. This row of columns
comprises only half of the depicted unit cells. The same columnar
aggregates occupy the space of the second half by nano-segre-
gation of the alkyl chains in the central part of the cell. Thereby,
they form the C2-symmetric structure of the plane group. The
unit cell contains a total of two columns. In a unit cell slice with
Model of the columnar phases
E-Shaped conformers have been reported for the parent mole-
cules forming the hexagonal columns owing to the small
columnar diameter compared with the diameter of the all-s-trans
conformation of the mesogens.16 Such conformers are the result
of frustration and the energy minimisation by optimising nano-
segregation and space-filling. The structure of mesogen 1a differs
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Fig. 5 Model of the rectangular columnar phase and its transformation to the lamellar uniaxial phase at high temperature. The distance between the
perfluorinated lamellae decreases with increasing temperature, however, the distance of mesogens in the column increases. At the phase transition Colrd
to the lamellar phase the positions of the columns and most probably also of the mesogens within the columns are no longer well defined, indicating
a SmA phase.
˚
a height of 5.2 A, which is the intracolumnar separation of
mesogens, there are 4 mesogens filling the space, which results in
a reasonable density for molecules containing perfluorinated
alkyl chains of 1.23 g cmꢀ3. In this model, the chromophores are
indeed confined to the interface between semi-perfluorinated
chains and oligobenzoate building blocks. The model also
explains the transition to the lamellar phase. The columns are
already preorganised in lamellae in the p2mg phase, however,
they are locked in defined positions. At the temperature of the
phase transition to the SmA phase, the identical molecules
without semi-perfluorinated chains are already in the isotropic
phase. This indicates that the interactions of the oligobenzoate
cores and the aliphatic chains are weak at this temperature and
the lamellar structure is maintained mainly by the fluorophilic
interactions of the perfluorinated building blocks. Consequently,
the lamellae are not formed by columns, but by single molecules
or small columnar aggregates, which leads to homeotropic
Fig. 6 UV/Vis absorption spectra of star mesogens in solution (solid
aligned samples between two glass plates.
lines) and as thin spin coated films (dotted lines). The inset is an expan-
Such a transition from a SmA phase to a columnar phase may
sion of the long-wavelength absorption edge at 345 nm for the solution
be of interest for the facile, uniform planar alignment of columns
spectra.
for applications, for example in organic field effect transistors. If
slowly cooled, columns grow preferentially along the homeo-
tropically oriented layers. Similar thermotropic behaviour for
solution spectra exhibit large absorption bands at short wave-
fluorinated molecules has also been found in the series of
lengths with a maximum at 282 nm. These signals consist of
nonconventional polycatenar24 and swallow-tailed25 mesogens.
overlapping absorptions from different aromatic building
blocks, i.e. naphthalene, benzene and gallic acid ester units. The
long-wavelength absorptions at about 338 nm possesses a very
Absorption and fluorescence studies in solution and
thin films
low intensity, which might be attributed to the forbidden a-band
of naphthalene derivatives.29 If aggregates are present in the
The performance of LC materials in plastic electronic devices
depends strongly on the order of chromophores.1a,26 For the
hopping transport of charges, theory predicts high charge carrier
mobility in co-planar stacks of hopping sites, consisting of the
condensed aromatic building blocks.27 Investigation of the
absorption and the fluorescence of these materials can provide
information about the chromophore order in organised media,
based on the exciton theory.28 The absorption spectra of 1 in
CH2Cl2 and thin spin coated films are shown in Fig. 6. All
organised material considerable changes should be observed in
the absorption spectra. The exciton model predicts bathochromic
shifts of absorption maxima in J-type and hypsochromic shifts in
H-type aggregates.28 Comparison of the absorption spectra of all
star-shaped mesogens with one naphthalene in solution and thin
solid films clearly excludes a bathochromic shift, which is
evidence that J-type aggregates are not formed. Owing to the
aggregation of E-shaped mesogens in columnar phases, H-type
aggregates are most probable. Although a small hypsochromic
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shift of the maxima at 338 nm is observed, the overall shape of
the absorption spectra in solution and solid state remains similar.
The hypsochromic shift does not necessarily account for H-type
aggregates and might have its origin in the different environment
of the absorbing species without the solvent matrix. The overlap
of absorption bands from different building blocks prevents
a more detailed analysis.
in different fluorescence spectra in liquid and solid states, thus
indicating the homogeneity of the phases and the fact that all
chromophores possess on average a similar environment.
Although there is a large difference in structure of the columnar
phases of 1a and 1b, no difference can be discovered in the
photophysical studies. Consequently, the confinement of
naphthalene to the interface of semi-perfluorinated chains and
oligobenzoate scaffold does not lead to a stronger interaction of
these functional building blocks. This might be attributed first to
the proposed E-shaped conformers, which are suggested to self-
organise in these types of columnar phases. In order to form
these conformers, the chromophores which are close to the core
of the mesogens have to incline, thus, the formation of strong
interacting aggregates along the column is less probable. Second,
the semi-perfluorinated alkyl chains result in an increased
separation of chromophores owing to the larger volume of the
perfluorinated methylene segments compared with conventional
alkyl chains.
Fluorescence spectroscopy can give further information about
the order of the naphthalene derivatives in the solid state.
Recently, naphthalene has been studied in amorphous solids,30 in
LC polymers,31 as guests in cyclodextrins32 and confined in
micelles of block copolymers.33 In less ordered, amorphous
materials, naphthalene exhibits a typical broad emission with
a maximum between 380 to 410 nm and a band width of about
2800–5000 cmꢀ1, which is attributed to excimer formation.30 In
the single crystal only monomer-like emission at short wave-
lengths can be observed. In contrast, a confined space of micelles
leads to the formation of aggregates, which results in different
structured emission bands with emission maxima even above
500 nm.33 Similar structured fluorescence spectra were recently
found for symmetric star-shaped mesogens with three naphtha-
lenes directly attached to the phloroglucinol core in its high
ordered columnar phase, which showed an excellent charge
carrier mobility.21 Fig. 7 presents the fluorescence spectra of two
arm derivatives 3a and 3b as well as the spectra of the stars 1a and
1b. The arms containing only benzoate and gallic acid ester units
show a slight hypsochromic shift by approximately 5 nm of the
emission maxima in the solid state. Star-shaped mesogens with
only one naphthalene chromophore exhibit significantly different
behaviour. The solid state spectra show bathochromically shifted
emission maxima by 31 nm, however, they are very broad and
centred around 390 nm with a shoulder at 410 nm, which are
features frequently attributed to naphthalene excimer emission
or the fluorescence of the statistical LC copolymer Vectra
A910ꢀ. It should be noted that, in contrast to block copoly-
mers,33 the variation of the excitation wavelength did not result
Summary and conclusions
Desymmetrised star-shaped mesogens with only one naphthalene
chromophore in the scaffold were synthesised efficiently. In
contrast to previously reported C3-symmetric derivatives, no
highly ordered helical columnar mesophase is observed at low
temperature. Instead, attachment of arms of different lengths
around the phloroglucinol core results in stable columnar
hexagonal phases if the lengths of the oligobenzoate arms are not
too different, otherwise, a cubic phase is formed. If only one arm
is decorated with semi-perfluorinated chains, molecules arrange
in a more complex rectangular phase with p2mg symmetry and
inherently preorganised lamellar structure. The latter transforms
to aꢁ SmA type lamellar phase at higher temperature above
159 C, where the interaction of the semi-perfluorinated chains
holds the molecules in a layered structure. Such transitions might
be useful for the uniform planar alignment of columnar phases.
Compared to the non-fluorinated derivatives in the series, the
latter was expected to segregate the chromophores at the inter-
face between semi-perfluorinated chains and oligobenzoate
scaffold. The chromophores are, however, not strongly inter-
acting, which is indicated by results from UV-Vis absorption and
emission studies. Fluorescence spectra show characteristic
features of excimer emission, thus pointing to chromophores in
close proximity without forming defined ground-state aggre-
gates. This is attributed to the E-shaped conformers and the large
intra-columnar separation because of the semi-perfluorinated
chains.
Experimental
General methods
Chemicals were obtained from Acros and Sigma-Aldrich and
used as received. The syntheses of compounds 3a,b,c,e, 9–13 were
described previously.15,21,22 Column chromatography was carried
1
out on silica 60 (Merck, mesh 70–230). PFT H and 13C NMR
spectra were recorded in CDCl3 with a Varian Oxford 400 MHz
spectrometer with the residual solvent signal at 7.26 ppm as
a reference. Mass spectra were obtained on a Finnigan MAT95
(FD MS). Elemental analysis was carried out in the
Fig. 7 Comparison of fluorescence spectra of 1a,b and 3a,b in CHCl3
solution and thin spin coated films. The maxima of all spectra are nor-
malised.
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microanalytical laboratory at the University of Mainz. POM
observations were made with a Zeiss Axioscop 40 equipped with
a Linkam THMS600 hot stage. DSC was performed using
a Perkin Elmer Pyris 1. X-Ray diffraction measurements were
carried out on both powder and aligned samples in glass
capillaries of 2 mm diameter. The aligned fibres were obtained by
extrusion from the LC phase.
and converted and worked up as described for the first step of
compound 3d. After purification by column chromatography
(hexane–ethyl acetate ¼ 6 : 1) and crystallisation from acetone,
the product was obtained as a colourless solid (1.23 g, 79%). 1.22
g (0.69 mmol) of the benzyl ester was then deprotected and
purified analogously to compound 3d. Crystallisation from
acetone afforded phenol 8 as a colourless solid (0.85 g, 73%). 1H
NMR (400 MHz, CDCl3): d ¼ 0.876, 0.88 (2 t, 18 H, CH3); 1.24–
1.38 (m, 96 H, CH2); 1.45–1.52 (m, 12 H, CH2); 1.73–1.87 (m, 12
H, CH2); 4.05 (t, 8 H, OCH2); 4.07 (t, 4 H, OCH2); 5.81 (br s, 1 H,
OH); 6.67 (m, 2 H, aromat. CH); 6.77 (m, 1 H, aromat. CH); 7.35
(AA0BB0, 2 H, CH); 7.41 (s, 4 H, CH); 8.26 (AA0BB0, 4 H, CH);
13C NMR (100 MHz, CDCl3): d ¼ 14.1 (CH3); 22.69, 22.7, 26.0,
26.1, 29.26, 29.36, 29.39, 29.40, 29.57, 29.66, 29.7, 29.73, 29.74,
29.76, 30.3, 31.92, 31.94 (CH2); 69.3, 73.6 (OCH2); 107.2, 107.9,
108.6, 122.2 (Ct); 123.2 (Cq); 126.7 (Cq); 131.9 (Ct); 143.2, 151.9,
153.0, 155.4, 157.1 (Cq); 164.0; 164.5 (Cq, C]O)
The WAXS measurements were performed by using a standard
copper anode (2.2 kW) source with pinhole collimation equipped
with a X-ray mirror (Osmic typ CMF15-sCu6) and a Bruker
detector (High-star) with 1024 ꢂ 1024 pixels. The SAXS
measurements were completed by using a rotating anode
(mikromax 007, copper, Rigaku) source with pinhole collimation
equipped with a X-ray mirror (Osmic type 140-0040 12) and
a Bruker detector (High-star) with 1024 ꢂ 1024 pixels. The
diffraction data were calibrated by using silver behenate as a cali-
bration standard.34 The X-ray patterns were evaluated using the
datasqueeze software (http://www.datasqueezesoftware.com/).
Thin films were prepared by spin coating from CHCl3
solution.
100-[60-(3,4,5-Tridodecyloxybenzoyloxy)-2-naphthoyloxy]-3,5-
dihydroxybenzene (5). 0.40 g (0.47 mmol) 3c, 0.14 g (0.45 mmol)
3,5-dibenzyloxyphenol, 0.20 g (0.95 mmol) DCC and 0.06 g
(0.19 mmol) DPTS were converted and isolated analogously to
the esterification procedure of 3d. Purification by column chro-
matography (hexane–ethyl acetate ¼ 10 :1) and crystallisation
from acetone yielded compound 5 as colourless solid (0.20 g,
40%). The cleavage of the benzyl protecting group was per-
formed analogously to compound 3d. 0.20 g (0.18 mmol)
dibenzyl ether was converted and after purification by column
chromatography, the product was obtained as a colourless solid
60-(3,4,5-Tris(1H,1H,2H,2H,3H,3H,4H,4H-perfluorododecyloxy-
benzoyloxy)naphthoic acid (3d). 1.10 g (0.69 mmol) 3,4,5-
Tris(1H,1H,2H,2H,3H,3H,4H,4H-perfluorododecyloxy)benzoic
acid was coupled with 0.21 g (0.75 mmol) 4-hydroxybenzoic acid
benzyl ester using 0.31
g
(1.49 mmol) N,N0-dicyclohex-
ylcarbodiimide (DCC) and 0.11 g (0.37 mmol) 4-(dimethylami-
no)pyridinium p-toluenesulfonate (DPTS) as coupling reagents.
All materials were dissolved in 40 mL dry methylene chloride and
stirred under nitrogen atmosphere overnight. The solvent was
removed under vacuum and the crude product was extracted
with hexane. DPTS and a part of DCC were removed by filtra-
tion. Further purification by column chromatography (hexane–
ethyl acetate–chloroform ¼ 9 : 1 : 1) and recrystallisation from
acetone yielded 0.65 g, 51% of a colourless solid. 0.6 g (0.32
mmol) of the benzyl ester was then dissolved in 50 mL diethyl
ether and one spatula of Pd/C (10%) was added. The mixture was
stirred under hydrogen atmosphere overnight. Filtration over
Celite 512 and evaporation of the solvent under vacuum yielded
the crude product. Crystallization from acetone afforded the
1
(0.16 g, 95%). H NMR (400 MHz, CDCl3): d ¼ 0.88 (2 t, 9 H,
CH3); 1.26–1.55 (m, 54 H, CH2); 1.74–1.88 (m, 6 H, CH2); 4.07 (2
t, 18 H, OCH2); 5.38 (bs, 2 H, OH); 6.27 (t, 1 H, CH); 6.36 (d, 2
H, CH); 7.44 (dd, 3J ¼ 8.9, 4J ¼ 2.5, 1 H, CH); 7.45 (s, 2 H, CH);
7.75 (dd, 4J ¼ 2.5, 5J ¼ 0.9, 1 H, CH); 7.93 (dd, 3J ¼ 8.7, 5J ¼ 0.7,
3
1 H, CH); 8.06 (dd, 3J ¼ 8.9, 5J ¼ 0.9, 1 H, CH); 8.19 (dd, J ¼
8.7, 4J ¼ 1.7, 1 H, CH); 8.78 (dd, 4J ¼ 1.7, 5J ¼ 0.7, 1 H, CH); 13
C
NMR (100 MHz, CDCl3): d ¼ 14.1 (CH3); 22.69, 22.71, 26.06,
26.08, 29.3, 29.37, 29.4, 29.57, 29.64, 29.66, 29.7, 29.73, 30.3,
31.9, 31.95 (CH2); 69.3, 73.6 (OCH2); 101.0, 102.1, 108.6, 118.9,
122.6 (Ct); 123.5 (Cq); 126.2 (Ct); 126.4 (Cq); 128.2 (Ct); 130.5
(Cq); 131.1; 131.9 (Ct); 136.5, 143.2, 151.0, 152.4, 153.0, 157.3
(Cq); 165.0, 165.2 (C]O)
1
carboxylic acid 3d as a colourless solid (0.45 g, 79%). H NMR
(400 MHz, CDCl3, 5% CF2Cl-CFCl2): d ¼ 1.84–2.25 (m, 18 H,
CH2); 4.08 (t, 2 H, OCH2); 4.13 (t, 4 H, OCH2); 7.43 (dd, 3J ¼ 8.9,
4J ¼ 2.2, 1 H, CH); 7.48 (s, 2 H, CH); 7.74 (dd, 4J ¼ 2.2, 5J ¼ 0.8,
3,5-Bis[40-(3,4,5-tridodecyloxybenzoyloxy)benzoyloxy]-1-[60-
3
1 H, CH); 7.91 (dd, 3J ¼ 8.8, 5J ¼ 0.8, 1 H, CH); 8.06 (dd, J ¼
(3,4,5-tridodecyloxybenzoyloxy)-2-naphthoyloxy]benzene
(1a).
8.9, 5J ¼ 0.8, 1 H, CH); 8.14 (dd, 3J ¼ 8.8, 4J ¼ 1.6, 1 H, CH); 8.72
(dd, 4J, ¼ 1.6, 5J ¼ 0.8, 1 H, CH); 13C NMR (100 MHz, CDCl3;
5% CF2Cl-CFCl2): d ¼ 17.51 (d, CH2, 3JC–F ¼ 14 Hz); 29.0, 30.0
The esterification procedure was performed analogously to the
synthesis of compound 3d by conversion of 0.16 g (0.17 mmol)
diphenol 5, 0.30
g
(0.38 mmol) 4-(3,4,5-tridodecylox-
2
(CH2); 30.9 (t, CF2CH2, JC–F ¼ 22.7 Hz); 68.9, 72.9 (OCH2);
ybenzoyloxy)benzoic acid, 0.16 g (0.75 mmol) DCC and 0.05 g
(0.15 mmol) DPTS in 40 mL dry methylene chloride. Purification
by column chromatography (hexane–ethyl acetate ¼ 10 : 1) and
crystallisation from acetone yielded a colourless solid (0.38 g,
109.2, 119.0 (Ct); 122.5 (Ct), 124.6 (Cq); 126.5 (Ct); 126.8 (Cq),
128.2 (Ct); 130.8 (Cq); 131.3, 132.1 (Ct); 136.9; 143.3; 151.1; 153.1
(Cq); 164.7, 171.1 (Cq, C]O); MS (FD): m/z (%): M+ ¼ 1762.1
(100, M+c); EA: Calc. for C54H33F51O7: C, 36.79; H, 1.89, Found:
C, 36.67; H, 1.98%.
1
90%). H NMR (400 MHz; CDCl3): d ¼ 0.88 (2 t, 27 H, CH3);
1.26–1.52 (m, 162 H, CH2); 1.73–1.88 (m, 12 H, CH2); 4.07 (2 t 18
H, OCH2); 7.22 (t, 1 H, CH); 7.255 (d, 2 H, CH, partially
3,5-Bis[40-(3,4,5-tridodecyloxybenzoyloxy)benzoyloxy]-1-phenol
(8). 0.19 g (0.88 mmol) 1-Benzyloxy-3,5-dihydroxybenzene, 1.54
g 3b (1.93 mmol), 0.80 g (3.87 mmol) DCC and 0.23 g (0.77
mmol) DPTS were dissolved in 50 mL dry methylene chloride
superimposed with solvent signal); 7.37 (AA0BB0,
4 H,
aromat. CH); 7.41 (s, 4 H, CH); 7.46 (s, 2 H, CH); 7.47 (dd, 3J ¼
4
4
8.1, J ¼ 2.1, 1 H, CH, partially superimposed); 7.77 (dd, J ¼
5
3
5
2.1, J ¼ 0.7, 1 H, CH), 7.95 (dd, J ¼ 8.6, J ¼ 0.7, 1 H, CH);
This journal is ª The Royal Society of Chemistry 2008
J. Mater. Chem., 2008, 18, 2995–3003 | 3001

View Article Online
8.09 (dd, 3J ¼ 8.1, 5J ¼ 0.7, 1 H, CH); 8.22 (dd, 3J ¼ 8.6, 4J ¼ 1.7,
1 H, CH); 8.30 (AA0BB0, 4 H, CH); 8.82 (dd, 4J ¼ 1.7, 5J ¼ 0.7, 1
H, CH); 13C NMR (100 MHz; CDCl3): d ¼ 14.1 (CH3); 22.7,
26.05, 26.08, 29.3, 29.37, 29.4, 29.57, 29.63, 29.66, 29.7, 29.74,
30.3, 31.9, 31.95 (CH2); 69.3, 73.6 (OCH2); 108.6, 113.32, 113.42,
118.9, 122.3, 122.7 (Ct); 123.2, 123.5 (Cq); 126.2 (Ct); 126.5 (Cq);
128.3 (Ct); 130.5 (Cq); 131.2, 131.94, 132.0 (Ct); 136.6, 143.16,
143.24, 151.0, 151.5, 151.6, 153.0, 155.5 (Cq); 163.7; 164.4,
165.0 (C]O); MS (FD) m/z (%): 2606.8 (100, [M + 1]+c); EA:
Calc. for C160H248O21: C, 76.63; H, 9.97; Found: C, 76.56; H,
9.97%.
d ¼ 14.1 (CH3); 22.69, 22.7, 26.05, 26.08, 29.28, 29.37, 29.40,
29.57, 29.64, 29.66, 29.7, 29.73, 29.74, 29.76, 30.3, 31.92, 31.94
(CH2); 69.24, 69.28, 69.30, 73.58, 73.61, 73.62 (OCH2); 108.52,
108.60, 108.62, 113.2, 113.46, 113.53, 118.9, 122.23, 122.27, 122.5
(Ct); 123.21, 123.22, 123.27 (Cq); 126.2 (Ct), 126.21, 126.5, 126.7
(Cq); 128.3 (Ct); 130.5 (Cq); 131.2, 131.92, 131.95, 132.0 (Ct);
136.6, 143.1, 143.28, 143.32, 150.8, 151.5, 151.6, 151.7, 152.96,
153.0, 153.02, 155.5, 155.51 (Cq); 163.7, 164.3, 164.42, 164.44,
164.47 (Cq, C]O); MS (FD): m/z (%): 2507.2 (100, [M + 1]+c);
EA: Calc. for C160H248O21: C, 76.63; H, 9.97; Found: C, 76.71;
H, 10.11%.
5-(3,4,5-Tridodecyloxybenzoyloxy)-3-[40-(3,4,5-tridodecyloxyben-
zoyloxy)benzoyloxy]-1-[40-(3,4,5-tridodecyloxybenzoyloxy)naph-
thoyloxy]benzene (1c). The esterification procedure was
performed as described for compound 3d, by conversion of 0.20 g
(0.13 mmol) 13, 0.12 g (0.14 mmol) 3c, 0.06 g (0.28 mmol) DCC
and 0.02 g (0.06 mmol) DPTS in 40 mL dry methylene chloride.
Further purification by column chromatography (hexane: ethyl
acetate ¼ 10: 1) and crystallisation from acetone yielded 0.22 g
3,5-Bis[40-(3,4,5-tridodecyloxybenzoyloxy)benzoyloxy]-1-[60-(3,
4,5-tris(1H,1H,2H,2H,3H,3H,4H,4H-perfluorododecyloxyben-
zoyloxy)-2-naphthoyloxy]benzene (1b). The esterification proce-
dure was performed as described for compound 3d, by
conversion of 0.22 g (0.13 mmol) 8, 0.22 g (0.13 mmol) 3d, 0.06 g
(0.26 mmol) DCC and 0.02 g (0.05 mmol) DPTS in 40 mL dry
methylene chloride. Further purification by column chroma-
tography (hexane–ethyl acetate ¼ 10 : 1) and crystallisation from
acetone yielded 0.13 g (31%) of a colourless solid. 1H NMR (400
MHz, CDCl3, Me4Si): d ¼ 0.876, 0.88 (2 t, 18 H, CH3); 1.25–1.40
(m, 96 H, CH2); 1.45–1.53 (m, 12 H, CH2); 1.73–2.00 (m, 24 H,
CH2); 2.09–2.26 (m, 6 H, CH2); 4.04–4.10 (3 t, 14 H, OCH2); 4.14
(t, 4 H, OCH2); 7.22 (m, 2 H, aromat. CH); 7.26 (m, 1 H, aromat.
CH, partially superimposed with solvent signal); 7.38 (AA0BB0, 2
H, CH); 7.41 (s, 4 H, CH); 7.46 (dd, 3J ¼ 8.9, 4J ¼ 2.7, 1 H, CH);
7.49 (s, 2 H, CH); 7.76 (dd, 4J ¼ 2.7, 5J ¼ 0.8, 1 H, CH); 7.95 (dd,
3J ¼ 8.8, 5J ¼ 0.8, 1 H, CH); 8.09 (dd, 3J ¼ 8.9, 5J ¼ 0.8, 1 H, CH);
8.23 (dd, 3J ¼ 8.8, 4J ¼ 1.9, 1 H, CH); 8.30 (AA0BB0, 4 H, CH),
1
(72%) of a colourless solid. H NMR (400 MHz, CDCl3): d ¼
0.88 (m, 27 H, CH3), 1.26–1.37 (m, 144 H, CH2); 1.46–1.53 (m, 18
H, CH2); 1.73–1.88 (m, 18 H, CH2), 4.03–4.10 (m, 18 H OCH2),
7.18 (m, 1 H, CH); 7.21 (m, 1 H, CH), 7.23 (m, 1 H, CH); 7.37 (2
H, CH, AA0BB0); 7.41 (s, 2 H, CH), 7.413 (s, 2 H, CH), 7.46 (s, 2
3
4
H, CH); 7.464 (dd, J ¼ 8.9, J ¼ 2.5, 1 H, CH partially super-
4
5
3
imposed); 7.76 (dd, J ¼ 2.5, J ¼ 0.8, 1 H, CH); 7.95 (dd, J ¼
8.7, 5J ¼ 0.8, 1 H, CH); 8.08 (dd, 3J ¼ 8.9, 5J ¼ 0.8, 1 H, CH); 8.22
(dd, 3J ¼ 8.7, 4J ¼ 1.8, 1 H, CH); 8.29 (AA0BB0, 2 H, CH); 8.82
(dd, 4J ¼ 1.8, 5J ¼ 0.8, 1 H, CH); 13C NMR (100 MHz, CDCl3):
d ¼ 14.1 (CH3); 22.69, 22.7, 26.05, 26.08, 29.28, 29.37, 29.40,
29.57, 29.64, 29.66, 29.7, 29.74, 29.76, 30.3, 31.92, 31.94 (CH2);
69.25, 69.28, 73.59, 73.62 (OCH2); 108.5, 108.6, 113.2, 113.45,
113.54, 118.9, 122.2, 122.7 (Ct), 123.2, 123.3, 123.5, 126.13 (Cq),
126.14 (Ct); 126.5, (Cq); 128.3, 130.5 (Cq); 131.2, 131.9, 132.0
(Ct); 136.6, 143.15, 143.2, 143.3, 151.0; 151.5, 151.6, 151.7,
152.96, 153.0, 155.5, (Cq); 163.7, 164.3, 164.43, 164.46, 164.9 (Cq,
C]O); MS (FD): m/z (%): 2387.2 (100, [M + 1]+$); EA: Calc. for
8.83 (dd, J ¼ 1.9, J ¼ 0.8, 1 H, CH); 13C NMR (100 MHz,
CDCl3): d ¼ 14.1 (CH3); 17.2 (d), 22.69, 22.7, 26.05, 26.08, 28.7,
29.27, 29.37, 29.39, 29.57, 29.63, 29.66, 29.7, 29.73, 29.74, 29.76,
30.3, 30.6 (t), 31.92; 31.94 (CH2); 68.5, 69.3, 72.8, 73.6 (OCH2);
108.54, 108.58; 113.36, 113.42; 118.9, 122.3, 122.5 (Ct); 123.2,
124.1; 126.2 (Cq); 126.23 (Ct); 126.5 (Cq); 128.3 (Ct); 130.5 (Cq);
131.3, 131.9, 132.0 (Ct); 136.6, 142.6, 143.2; 150.9, 151.5, 151.6,
152.7, 153.0 (Cq); 155.5 (Cq); 163.7, 164.4, 164.44, 164.7 (Cq,
C]O). MS (FD): m/z (%): 3421.4 (37), 3422.4 (100), 3423.2 (90).
EA: Calc. for C160H197F51O21 C 56.11, H 5.80; Found: C 56.25,
H 5.77%.
4
5
C153H244O19: C, 76.93; H, 10.30; Found: C, 76.81; H, 10.17%.
5-(3,4,5-Tridodecyloxybenzoyloxy)-3-[40-(3,4,5-tridodecyl-oxy-
benzoyloxy)benzoyloxy]-1-{40-[400-(3,4,5-tridodecyl-oxybenzoyloxy)
benzoyloxy]napthoyloxy}benzene (1d). The esterification proce-
dure was performed as described for compound 3d, by conver-
sion of 0.20 g (0.13 mmol) 13, 0.14 g (0.14 mmol) 3e, 0.06 g (0.28
mmol) DCC and 0.02 g (0.06 mmol) DPTS in 40 mL dry meth-
ylene chloride. Further purification by column chromatography
(hexane–ethyl acetate ¼ 10 : 1) and crystallisation from acetone
Acknowledgements
We are grateful to the Bundesministerium fur Bildung und
¨
Forschung (BMBF) and the Deutsche Forschungsgemeinschaft
(DFG) for their financial support. We thank Prof. Herbert
Meier, Annette Oehlhof and Dr Norbert Hanold for the
completion of FD mass spectrometry and elemental analysis at
the University of Mainz and Dr U. Baumeister (University of
Halle) for fruitful discussions.
1
yielded 0.23 g (72%) of a colourless solid. H NMR (400 MHz,
CDCl3): d ¼ 0.88 (m, 27 H, CH3); 1.26–1.37 (m, 144 H, CH2);
1.45–1.53 (m, 18 H, CH2); 1.73–1.88 (m, 18 H, CH2); 4.04–4.10
(m, 18 H OCH2); 7.18 (m, 1 H, CH); 7.22 (m, 1 H, CH); 7.24 (m, 1
H, CH); 7.37 (AA0BB0, 2 H, CH); 7.40 (AA0BB0, 2 H, CH
partially superimposed); 7.41 (s, 2 H, CH); 7.414 (s, 2 H, CH);
7.43 (s, 2 H, CH); 7.50 (dd, 3J ¼ 9.0, 4J ¼ 2.3, 1 H, CH); 7.81 (dd,
4J ¼ 2.3, 5J ¼ 0.7, 1 H, CH); 7.97 (dd, 3J ¼ 8.7, 5J ¼ 0.7, 1 H, CH);
8.10 (dd, 3J ¼ 9.0, 5J ¼ 0.7, 1 H, CH); 8.23 (dd, 3J ¼ 8.7, 4J ¼ 1.7,
1 H, CH); 8.29 (2 H, CH, AA0BB0); 8.35 (2 H, CH, AA0BB0); 8.83
(dd, 4J ¼ 1.7, 5J ¼ 0.7, 1 H, CH); 13C NMR (100 MHz, CDCl3):
References
1 (a) T. Kato, N. Mizoshita and K. Kishimoto, Angew. Chem., Int. Ed.,
2006, 45, 38–68; T. Kato, N. Mizoshita and K. Kishimoto, Angew.
Chem., 2006, 118, 45–74, and references therein; (b) C. Tschierske,
Annu. Rep. Prog. Chem., Sect. C, 2001, 97, 191–267, and references
therein; (c) C. Tschierske, J. Mater. Chem., 2001, 11, 2647–2671;
(d) C. Tschierske, J. Mater. Chem., 1998, 8, 1485–1508;
3002 | J. Mater. Chem., 2008, 18, 2995–3003
This journal is ª The Royal Society of Chemistry 2008

View Article Online
(e) C. Tschierske, Prog. Polym. Sci., 1996, 21, 775–852; (f) D. Demus,
Liq. Cryst., 1989, 5, 75–110.
J. C. Mastrangelo, D. Katsis and S. H. Chen, Chem. Mater., 2001,
´
13, 4584–4594; (c) A. Omenat, J. Barbera, J.-L. Serrano,
2 (a) M. Marcos, R. Martin-Rapun, A. Omenat and J.-L. Serrano,
Chem. Soc. Rev., 2007, 36, 1889; (b) B. Donnio and D. Guillon,
Adv. Polym. Sci., 2006, 201, 45–155; (c) S. A. Ponomarenko,
N. Boiko and V. Shibaev, Polym. Sci. C, 2001, 43, 1–45;
(d) I. M. Saez and J. W. Goodby, J. Mater. Chem., 2005, 15, 26–40;
(e) I. M. Saez and J. W. Goodby, Chem.–Eur. J., 2003, 9, 4869–4877.
3 M. Lehmann, C. Ko¨hn, H. Meier, S. Renker and A. Oehlhof,
J. Mater. Chem., 2006, 16, 441–451.
4 (a) V. Percec, M. Glodde, M. Peterca, A. Rapp, I. Schnell,
H. W. Spiess, T. K. Bera, Y. Miura, V. S. Balagurusamy, E. Aqad
and P. A. Heiney, Chem.–Eur. J., 2006, 12, 6298–6314; (b)
V. Percec, M. Glodde, T. K. Bera, Y. Miura, I. Shiyanovskaya,
K. D. Singer, V. S. K. Balagurusamy, P. A. Heiney, I. Schnell,
A. Rapp, H. W. Spieß, S. D. Hudson and H. Duan, Nature, 2002,
417, 384–387.
S. Houbrechts and A. Persoons, Adv. Mater., 1999, 11, 1292–1295;
(d) B. Liu, X. Y. Zahang and X. Z. Yang, Chin. Chem. Lett., 1992,
3, 663–664; (e) S. Takenaka, Y. Masuda, M. Iwano, H. Morita,
S. Kusabayashi, H. Sigiura and T. Ikemoto, Mol. Cryst. Liq. Cryst.,
1989, 168, 111–124; (f) G. Lattermann, Liq. Cryst., 1987, 2, 723–
728; (g) S. Takenaka, K. Nishimura and S. Kusabayashi, Mol.
Cryst. Liq. Cryst., 1984, 111, 227–236.
15 (a) M. Lehmann, R. I. Gearba, M. H. J. Koch and D. Ivanov, Chem.
Mater., 2004, 16, 374–376; (b) M. Lehmann, R. I. Gearba,
M. H. J. Koch and D. Ivanov, Mol. Cryst. Liq. Cryst., 2004, 411,
397–406.
16 M. Lehmann, M. Jahr, B. Donnio, R. Graf, S. Gemming and
I. Popov, Chem.–Eur. J., 2008, 14, 3562–3576.
17 (a) L. J. Wang, Q. Peng, Q. K. Li and Z. Shuai, J. Chem. Phys., 2007,
127, 044506; (b) L. B. Schein, C. B. Duck and A. R. McGhie, Phys.
Rev. Lett., 1978, 40, 197.
18 (a) M. Funahashi and Jun-ichi Hanna, Appl. Phys. Lett., 1997, 71,
602; (b) K. Oikawa, H. Monobe, K.-I. Nakayama, T. Kimoto,
K. Tsuchiya, B. Heinrich, D. Guillon, Y. Shimizu and
M. Yokoyama, Adv. Mater., 2007, 19, 1864.
19 I. Shiyanovskaya, K. D. Singer, V. Percec, T. K. Bera, Y. Miura and
M. Glodde, Phys. Rev. B, 2003, 67, 035204.
20 (a) N. Yoshimoto and J.-I. Hanna, J. Mater. Chem., 2003, 13, 1004;
(b) V. S. Sangawar, R. J. Dhokne, A. U. Ubale, P. S. Chikhalikar
and S. D. Meshram, Bull. Mater Sci., 2007, 30, 163.
21 M. Lehmann, M. Jahr, F. C. Grozema, R. D. Abellon,
D. A. Siebbeles and M. Muller, unpublished results.
¨
22 M. Lehmann and M. Jahr, Org. Lett., 2006, 8, 721–723.
23 A. Immirzi and B. Perini, Acta Crystallogr., Sect. A, 1977, 33,
216–218.
5 A. SkouliosandD. Guillon, Mol. Cryst. Liq. Cryst., 1988, 165, 317–332.
6 For a review see: A. Nantalaksakul, D. R. Reddy, Ch. J. Bardeen and
S. Thayumanavan, Photosynth. Res., 2006, 87, 133–150.
7 Some examples of shape persistent three-armed mesogens: (a)
R. Christiano, D. M. Pereira de Oliveira Santos and H. Gallardo,
Liq. Cryst., 2005, 32, 7–14; (b) Y.-C. Lin, C. K. Lai, Y.-C. Chang
and K.-T. Liu, Liq. Cryst., 2002, 29, 237–242; (c) C.-H. Lee and
T. Yamamoto, Mol. Cryst. Liq. Cryst., 2002, 378, 13–21; (d)
B. G. Kim, S. Kim and S. Y. Park, Tetrahedron Lett., 2001, 42,
2697–2699; (e) J. C. Chang, J. R. Yeon, Y. S. Chin, M. J. Han and
S.-K. Hong, Chem. Mater., 2000, 12, 1076–1082; (f) J. C. Chang,
J. H. Baik, C. B. Lee, M. J. Han and S.-K. Hong, J. Am. Chem.
Soc., 1997, 119, 3197–3198; (g) D. J. Pesak and J. S. Moore, Angew.
Chem., Int. Ed. Engl., 1997, 36, 1636–1639; D. J. Pesak and
J. S. Moore, Angew. Chem., 1997, 109, 1709–1712.
8 Some examples of stilbenoid three-armed mesogens: (a) H. C. Holst,
T. Pakula and H. Meier, Tetrahedron, 2004, 60, 6765–6775; (b)
H. Meier, M. Lehmann, H. C. Holst and D. Schwo¨ppe,
Tetrahedron, 2004, 60, 6881–6888; (c) H. Meier, M. Lehmann and
U. Kolb, Chem.–Eur. J., 2000, 6, 2462–2469; (d) M. Lehmann,
B. Schartel, M. Hennecke and H. Meier, Tetrahedron, 1999, 55,
13377–13394; (e) H. Meier and M. Lehmann, Angew. Chem., Int.
Ed., 1998, 37, 643–645; H. Meier and M. Lehmann, Angew. Chem.,
1998, 110, 666–669; (f) A.-J. Attias, Ch. Cavalli, B. Donnio,
24 E. Nishikawa, J. Yamamoto and H. Yokoyama, J. Mater. Chem.,
2003, 13, 1887.
25 D. Lose, S. Diele, G. Pelzl, E. Dietzmann and W. Weissflog,
Liq. Cryst., 1998, 24, 707.
26 (a) A. M. van de Craats, J. M. Warman, M. P. De Haas, D. Adam,
J. Simmerer, D. Haarer and P. Schuhmacher, Adv. Mater., 1996, 8,
´
823; (b) M. Lehmann, G. Kestemont, R. Gomez Aspe, C. Buess-
Herman, M. H. J. Koch, M. G. Debije, J. Piris, M. P. de Haas,
J. M. Warman, M. D. Watson, V. Lemaur, J. Cornil, Y. H. Geerts,
R. Gearba and D. A. Ivanov, Chem.–Eur. J., 2005, 11, 3349–3362;
(c) for a review see also R. J. Bushby and O. R. Lozman, Curr.
Opin. Colloid Sci., 2002, 7, 343–354; (d) S. Sergeyev, W. Pisula and
Y. Geerts, Chem. Soc. Rev., 2007, 36, 1902; (e) S. Laschat, A. Baro,
N. Steinke, F. Giesselmann, C. Ha¨gele, G. Scalia, R. Judele,
E. Kapatsina, S. Sauer, A. Schreivogel and M. Tosoni, Angew.
Chem., 2007, 119, 4916; S. Laschat, A. Baro, N. Steinke,
F. Giesselmann, C. Ha¨gele, G. Scalia, R. Judele, E. Kapatsina,
S. Sauer, A. Schreivogel and M. Tosoni, Angew. Chem., Int. Ed.,
2007, 46, 4832.
ˆ
D. Guillon, P. Hapiot and J. Malthete, Chem. Mater., 2002, 14,
375–384; (g) G. Zerban and H. Meier, Z. Naturforsch., 1993, 48b,
171–184; (h) H. Meier, Angew. Chem., Int. Ed. Engl., 1992, 31,
1399–1420; H. Meier, Angew. Chem., 1992, 104, 1425–1576.
9 Some examples of hydrogen-bonded three-armed mesogens: (a)
´
J. Barbera, L. Puig, J.-L. Serrano and T. Sierra, Chem. Mater., 2004,
16, 3308–3317; (b) M. L. Bushey, T.-Q. Nguyen, W. Zhang,
D. Horoszewski and C. Nuckolls, Angew. Chem., Int. Ed., 2004, 43,
5446–5453; M. L. Bushey, T.-Q. Nguyen, W. Zhang, D. Horoszewski
and C. Nuckolls, Angew. Chem., 2004, 116, 5562–5570, and
references therein; (c) J. J. van Gorp, J. A. J. M. Vekemans and
E. W. Meijer, Mol. Cryst. Liq. Cryst., 2003, 397, 191–205; (d)
J. J. van Gorp, J. A. J. M. Vekemans and E. W. Meijer, J. Am.
Chem. Soc., 2002, 124, 14759–14769, and references therein.
10 M. Katoh, S. Uehara, S. Kohmoto and K. Kishikawa, Chem. Lett.,
2006, 35, 322–323.
27 V. Lemaur, D. A. da Silva Filho, V. Coropceanu, M. Lehmann,
Y. Geerts, J. Piris, M. G. Debije, A. M. van de Craats,
´
K. Senthilkumar, L. D. A. Siebbeles, J. M. Warman, J. L. Bredas
and J. Cornil, J. Am. Chem. Soc., 2004, 126, 3271–3279.
28 (a) P. W. Bohn, Annu. Rev. Phys. Chem., 1993, 44, 37–60;
(b) M. Kasha, H. R. Rawls and M. Asharaf El-Bayoumi, Pure
Appl. Chem., 1965, 11, 371–392.
29 M. Hesse, H. Meier and B. Zeeh, Spektroskopische Methoden in der
Organischen Chemie, 5th edn, Georg Thieme Verlag, Stuttgart,
New York, 1995.
11 T. Hatano and T. Kato, Chem. Commun., 2006, 1277–1279.
12 Examples of C3-symmetric cyclotriphosphazene mesogens: (a)
´
´
´
J. Barbera, J. Jimenez, A. Laguna, L. Oriol, S. Perez and
J. L. Serrano, Chem. Mater., 2006, 18, 5437–5445; (b) J. Barbera,
´
M. Bardj´ı, J. Jime´nez, A. Laguna, M. P. Mart´ınez, L. Oriol,
J. L. Serrano and I. Zaragozano, J. Am. Chem. Soc., 2005, 127,
8994–9002; (c) K. Moriya, Y. Kawanishi, S. Yano and
M. Kajiwara, Chem. Commun., 2000, 1111–1112; (d) A. M. Levelut
and K. Morija, Liq. Cryst., 1996, 20, 119–124.
30 H. Nakayama, T. Hosokawa and K. Ishii, Chem. Phys. Lett., 1998,
289, 275–280.
31 S. J. Lukacs, S. M. Cohen and F. H. Long, J. Phys. Chem. B, 1999,
103, 6648–6652.
32 G. Grabner, K. Rechthaler, B. Mayer, G. Ko¨hler and K. Rotkiewicz,
J. Phys. Chem. A, 2000, 104, 1365–1376.
33 S. Zapozoczny, M. Rymarzyk-Machal, A. Stradomska, P. Petelenz
and M. Nowakowska, J. Phys. Chem. B, 2007, 111, 10088–10094.
34 T. C. Huang, H. Toraya, T. N. Blanton and J. Wu, J. Appl.
Crystallogr., 1993, 26, 180.
13 D. Goldmann, D. Janietz, C. Schmidt and J. H. Wendorff, Liq.
Cryst., 1998, 25, 711–719.
14 Examples of oligobenzoate three-armed star-shaped mesogens:
(a) B.-Y. Zhang, D.-S. Yao, F.-B. Meng and Y.-H. Li, J. Mol.
Struct., 2005, 741, 135–140; (b) F. Y. Fan, S. W. Culligan,
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