Dipole-driven self-assembly of redox-active mesogenic tetracyanoanthraquinodimethanes

Article abstract of DOI:10.1039/b808029a

Tetracyanoanthraquinodimethane (TCAQ) derivatives having three alkoxy chains at their extremities self-assemble to form both columnar liquid crystals and fibrous aggregates through intermolecular dipole-dipole interactions. The TCAQ derivatives are redox-

Full text of DOI:10.1039/b808029a

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PAPER
www.rsc.org/materials | Journal of Materials Chemistry
Dipole-driven self-assembly of redox-active mesogenic
tetracyanoanthraquinodimethanes†
*
Kyosuke Isoda, Takuma Yasuda and Takashi Kato
Received 12th May 2008, Accepted 11th July 2008
First published as an Advance Article on the web 12th August 2008
DOI: 10.1039/b808029a
Tetracyanoanthraquinodimethane (TCAQ) derivatives having three alkoxy chains at their extremities
self-assemble to form both columnar liquid crystals and fibrous aggregates through intermolecular
dipole–dipole interactions. The TCAQ derivatives are redox-active, and they exhibit responses in
electrochromism in the reductive potential region.
benzoyloxy moieties having one, two, or three long alkoxy
Introduction
chains13 were attached to the functional TCAQ and AQ cores,
respectively. TCAQ derivatives 1–3 were prepared via the
Knoevenagel condensation of 4–6 with Lehnert’s reagent,14
prepared from malononitrile, TiCl4, and pyridine. Compounds
4–6 were obtained by the condensation reaction of 2,6-
dihydroxyanthraquinone with two equivalents of the corres-
ponding benzoic acid bearing alkoxy chains. The chemical
Soft materials such as liquid crystals, gels, and polymers have
attracted attention1–4 because of their great potential as
dynamically functional materials. Liquid crystals are unique
among soft materials because they form ordered and dynamic
molecular structures, and the use of liquid crystals with
functional moieties is a useful approach to the preparation of
functional soft materials.5 It is of interest to incorporate electro-
active6 and redox-active7 moieties into liquid crystals to develop
low-dimensional (1D and 2D) conductive and photo-functional
materials. Our intention here is to incorporate a polar molecule,
11,11,12,12-tetracyanoanthraquinodimethane (TCAQ)8,9 into
mesogenic molecular structures. TCAQ molecules, analogues of
p-extended tetracyano-p-quinodimethane (TCNQ), have been
reported to show redox-active and electro-active properties.8,9 In
addition, they adopt a distorted roof-shaped conformation,
resulting in an intrinsic dipole moment perpendicular to the
molecules, which could be useful for specific intermolecular
interactions. Tetrathiafulvalene (TTF), TCNQ, TCAQ, and
their derivatives can also form conductive charge-transfer
complexes.10 Although recent research has focused on the
preparation of electro-active TTF-based liquid crystals11 and
nanofibers,12 the incorporation of TCAQ or TCNQ units into
these self-assembled materials has not been explored so far.
Herein, we report compounds 1–3 (Scheme 1), the first
example of mesogenic TCAQ derivatives that are capable of
forming both columnar liquid crystals and fibrous aggregates.
We have also prepared anthraquinone (AQ) derivatives 4–6
(Scheme 1), having a similar p-conjugated framework.
structures of these new compounds were confirmed by 1H and 13
C
NMR spectroscopy and elemental analysis (see the Experimental
section).
Liquid-crystalline properties
The thermal properties of compounds 1–6 are summarized in
Table 1. Compounds 1a,b, with three alkoxy chains at each
terminal, exhibit liquid-crystalline hexagonal columnar (Colh)
phases over a wide temperature range. A fan-like texture with
a large extinction along the polarizer directions is observed in the
Colh phase of 1a under the polarizing optical microscope (Fig. 1).
The X-ray diffraction pattern of 1a at 100 ꢀC shows four
˚
reflection peaks at 34.4 (100), 17.2 (200), 13.0 (210), and 11.4 A
˚
(300) in the small-angle region together with a weak peak at 3.7 A
˚
(001). The peak at 3.7 A is due to the stacking distance of the
adjacent TCAQ molecules within the column (Fig. 2). These
results suggest that an ordered Colh phase is formed for TCAQ
˚
derivatives 1a,b. The intercolumnar distance of 39.4 A in the Colh
phase of 1a at 80 ꢀC (estimated from the X-ray diffraction
pattern) increases to 40.1 A at 160 ꢀC (see ESI†). In contrast,
˚
analogous compounds 2a,b and 3a,b bearing one or two alkoxy
chains at each terminal of the TCAQ-based cores do not show
mesomorphic behavior. These results imply that polycatenar
structures are effective at inducing LC properties in the bulky
TCAQ molecules.13
Results and discussion
Molecular design and syntheses
AQ derivatives 6a,b show nematic and smectic C liquid-
crystalline phases, while compounds 4a,b and 5a,b do not exhibit
mesomorphic behavior. A Schlieren texture with 2-brush and
4-brush disclinations, which is characteristic of nematic phases, is
observed for 6a,b under the polarizing optical microscope
(Fig. 3a). Upon further cooling from the nematic phases, 6a,b
exhibit a smectic C phase over a wide temperature range. Fig. 3b
shows the characteristic fingerprint texture observed for 6a in the
smectic C phase at 190 ꢀC on cooling (see ESI† for 6b). The X-ray
We designed and synthesized TCAQ and AQ derivatives 1–6 as
shown in Scheme 1. To induce mesomorphic properties, two
Department of Chemistry and Biotechnology, School of Engineering, The
University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
E-mail: kato@chiral.t.u-tokyo.ac.jp; Fax: (+81) 3-5841-8661
† Electronic supplementary information (ESI) available: Synthetic
procedures and characterization data for 1–6; additional figures. See
DOI: 10.1039/b808029a
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Scheme 1 Synthesis of tetracyanoanthraquinodimethane (TCAQ) derivatives (1–3) and anthraquinone (AQ) derivatives (4–6).
Table 1 Thermal behavior of 1–6
Compound
Phase transitiona
1a
1b
2a
2b
3a
3b
4a
4b
5a
5b
6a
6b
Cr ꢁ10 (42) Colh 168 (24) Iso
Cr1 2 Cr2 61 (9) Colh 161 (22) Iso
Cr1 54 Cr2 74 Cr3 101 Cr4 110 (15) Iso
Cr1 7 Cr2 61 Cr3 115 Cr4 121 (45) Iso
Cr1 124 Cr2 136 (17) Iso
Cr 131 (18) Iso
Cr1 5 Cr2 69 Cr3 96 (90) Iso
Cr1 7 Cr2 27 Cr3 73 (105) Iso
Cr1 21 Cr2 62 Cr3 145 (114) Iso
Cr1 21 Cr2 49 Cr3 142 (128) Iso
Cr1 65 Cr2 77 Cr3 132 (20) SmC 184 (2) N 223 (2) Iso
Cr1 91 Cr2 103 Cr3 114 (17) SmC 197 (1) N 206 (1) Iso
Fig. 2 X-Ray diffraction pattern of 1a in the Colh phase at 100 ꢀC. The
a
Transition temperatures (ꢀC) and enthalpies of transition (kJ molꢁ1, in
parentheses) determined by DSC on second heating (first heating reflects
recrystallization conditions) at 5 ꢀC minꢁ1. Cr: crystalline; N: nematic;
SmC: smectic C; Colh: hexagonal columnar; Iso: isotropic.
insets show the magnified views.
Fig. 1 Polarizing optical photomicrograph of 1a in the Colh phase at
100 ꢀC.
diffraction pattern of 6a at 140 ꢀC shows two peaks with a
˚
d-spacing of 33.4 (001) and 16.5 A (002) (see ESI†). The fully
extended molecular length for 6a is estimated to be approxi-
˚
mately 50 A. It is considered that the molecules are tilted and that
Fig. 3 Polarizing optical photomicrographs of 6a (a) in the nematic
phase at 200 ꢀC and (b) in the smectic C phase at 190 ꢀC on cooling.
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˚
the terminal alkoxy chains are partially interdigitated in the
layered smectic C phase.
The intercolumnar distance of 39.7 A in the Colh phase of 1a at
100 ꢀC, estimated by the X-ray diffraction measurement, is
shorter than the fully extended molecular length of approxi-
It is of interest that the phase transition behavior of 1–3 is
markedly different from that of 4–6. The conformation and
polarity of their central aromatic framework are key factors for
mesomorphism. While the AQ unit has a planar geometry, the
TCAQ unit adopts a highly distorted roof-shaped conformation
as a consequence of the strong steric repulsion between the four
cyano groups and the four peri hydrogens,8a–c,15 and thereby
possesses an intrinsic dipole moment as large as 7.3 debye along
the C2 axis (Fig. 4a). Accordingly, strong longitudinal dipole–
dipole interactions can facilitate the self-assembly of 1a,b into
a 1D stacked array (Fig. 4b), in which the adjacent TCAQ
molecules should be arranged in an antipallarel manner. The
number of molecules located in a slice of each column can be
estimated as approximately 2 (see ESI†).16,17 Moreover, nano-
segregation of the highly polar TCAQ cores from the
surrounding lipophilic alkoxy chains plays a crucial role in the
preferable formation and stabilization of the Colh phases.
˚
mately 50 A (Fig. 4b). The interdigitation of the terminal alkoxy
chains between the neighboring columns would occur in the
Colh phase.
Swager and co-workers reported on 3,4-dicyanothiophene-
based bent-rod liquid crystals that have a large dipole moment in
the lateral direction.18 In this case, the molecules were assembled
in an antiparallel manner through intermolecular dipole–dipole
interactions. Mori and co-workers reported that the troponoid-
based liquid crystals possessing a peripheral cyano group
formed antipallarel assemblies assisted by canceling the dipole
repulsion.19 For these highly polar mesogenic molecules, the
intermolecular dipole–dipole interactions should be the driving
force to stabilize the LC phases.
Self-assembly in organic solvents
There are only a few examples of liquid-crystalline materials that
exhibit gelation abilities in organic solvents.5e,19b,20,21a Mamiya
et al. reported that carbonate-appended azobenzene derivatives
with a large dipole moment self-assemble into both smectic LC
phases and fibrous aggregates via intermolecular dipole–dipole
interactions.21a We expected that 1–3, having a large dipole
moment perpendicular to the p-conjugated cores, could also
gelate some organic solvents.
The gelation abilities of compound 1–6 were evaluated in
various organic solvents at a concentration of 10 g Lꢁ1. Only
TCAQ derivatives 1a,b, which are capable of forming 1D
columnar LC phases, show gelation abilities in dodecane at room
temperature, whereas the analogous compounds 2a,b and 3a,b as
well as AQ derivatives 4–6 are incapable of gelating any of the
solvents tested (see ESI†). Transparent gels are formed in
dodecane when the heated solution of 1a is cooled to room
temperature (Fig. 5a). The DSC measurement performed on the
dodecane gels ofꢀ1a at 10 g Lꢁ1 exhibits a single reversible sol–gel
transition at 67 C on heating (see ESI†). The polarized optical
microscopy for the gels of 1a reveals the formation of elongated
fibrous aggregates (Fig. 5b). The formed fibrous aggregates are
strongly birefringent, suggesting a high degree of molecular
ordering. The small-angle X-ray scattering (SAXS) pattern of
˚
the gels of 1a shows a peak at 39.6 A (see ESI†). This value
is comparable to the intercolumnar distance observed in the
˚
Colh phase of 1a (39.7 A). Therefore, the self-assembled
Fig. 4 (a) Optimized molecular geometry of TCAQ calculated at the
B3LYP/6-31G* level: top view (left) and side view (right). An arrow
indicates the dipole moment. (b) Representation of a possible self-
assembled columnar structure involving twelve stacked molecules of 1a.
Fig. 5 (a) Photograph and (b) polarizing optical photomicrograph of
the gel of 1a in dodecane (10 g Lꢁ1) at room temperature.
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nanostructures of 1a in the fibrous aggregates should be similar
to those of the columnar LC structures.
Similar dipole-driven assemblies in organic solvents were
reported for highly polar merocyanine dyes21b and cyano-
chalcone derivatives,21c in which the molecules adopted an
antipallarel arrangement to cancel their dipoles. Recently, we
reported pyridine-based diamide gelators with smectic layered
structures.22 Mesomorphic properties and gelation abilities are
closely related since the non-mesomorphic pyridyl derivatives do
not act as gelators. In the present study, a columnar structure
may be related to the formation of the self-assembled fibrous
aggregates in the solvents.
Electrochemical behavior
Compounds 1–6 have shown redox-active properties as charac-
terized by cyclic voltammetry. As shown in Fig. 6a, TCAQ
derivative 1a exhibits a single reversible reduction wave at the
half-wave potential (E1/2) of ꢁ0.46 V vs. Ag+/Ag, which is
ascribed to the formation of the dianion of 1a.8a–c A considerable
potential difference (DE ¼ 430 mV) between the cathodic and
anodic peaks may arise from conformational changes between
the distorted neutral 1a and the planar dianion of 1a during the
redox process. The redox behavior of 2a,b and 3a,b is similar to
that of 1a,b (see ESI†). The reduction potentials of TCAQ
derivatives 1–3 are shifted to more negative potentials than that
´
of TCAQ reported by Martın and co-workers (E1/2 ¼ ꢁ0.36 V vs.
Ag+/Ag).9a This behavior can be ascribed to the substitution
effect of the attached benzoyloxy groups.8b For compound 4a,
the two reversible reduction waves appear at E1/2 ¼ ꢁ1.10 and
ꢁ1.63 V vs. Ag+/Ag, and the redox behavior of 4b and 6a,b is
nearly the same as that of 4a (see ESI†). In contrast, the reduc-
tion potentials of 1–3 are observed at less negative potentials
compared to those of AQ derivatives 4a,b and 6a,b. These results
suggest that TCAQ derivatives 1–3 have higher electron-
accepting capabilities than AQ derivatives 4a,b and 6a,b.
The spectroelectrochemical experiments have been performed
for 1a in the same electrolyte solution (Fig. 6b). The UV–vis
absorption spectrum of 1a at 0 V vs. Ag+/Ag shows absorption
peaks at 300 and 350 nm. When the applied potential is nega-
tively increased from 0 to ꢁ1.4 V, a new broad absorption band
centered around 540 nm appears, accompanied by a decrease in
the absorbance at 350 nm. The visible absorption would be
ascribed to the formation of the dianion of 1a (Fig. 7a).8a–c By
returning to 0 V, the initial UV–vis spectrum is recovered. The
reversible redox cycles can also be achieved in a thin film of 1a
coated on an indium-tin-oxide (ITO)-coated glass electrode in
a Bu4NClO4/CH3CN electrolyte solution at room temperature.
An obvious color change between yellow (1a) and red (dianion of
1a) is observable during the reduction from 0 to ꢁ1.4 V (Fig. 7b).
Recently, Kitagawa and co-workers reported that a thin film of
Pt(II)-based metallomesogens with catecholate and 2,20-dipyridyl
ligands coated on an ITO glass electrode showed reversible redox
cycles in Colh phases.7a In the present study, the redox reaction,
accompanied by a clear color change, has been achieved for the
TCAQ derivative in the columnar LC state. To our knowledge,
there are few examples of redox-active columnar LC materials
that show reversible electrochromic behavior during the redox
reaction.
Fig. 6 (a) Cyclic voltammogram of 1a (2.0 mM) recorded in a CH2Cl2
solution of Bu4NClO4 (0.10 M). Sweep rate is 50 mV sꢁ1. (b) UV–vis
absorption spectra of 1a observed at 0 V (solid line) and ꢁ1.4 V (dashed
line) vs. Ag+/Ag.
Fig. 7 (a) Structural changes in 1a,b by redox reactions (R ¼ 3,4,5-tri-
alkoxyphenyl). (b) Photographs showing the electrochromic behavior of
a thin film of 1a coated on an ITO electrode in a CH3CN solution of
Bu4NClO4 (0.10 M): E ¼ 0 V (left); E ¼ ꢁ1.4 V (right).
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extracted with CHCl3, and the organic layer was washed with an
aqueous NaHCO3 and brine, and then dried over anhydrous
Na2SO4. After filtration and evaporation, the product was
purified by column chromatography (silica, CHCl3–hexane ¼ 1 :
1, v/v), recrystallized from CHCl3–methanol, and dried under
Conclusion
We have shown self-assembled structures and properties of
mesogenic molecules incorporating TCAQ and AQ. TCAQ
derivatives 1a,b based on highly polar p-conjugated cores self-
assemble into columnar liquid crystals via the intermolecular
dipole–dipole interactions and nanosegregation of polar
aromatic and aliphatic moieties. In contrast, AQ derivatives 6a,b
of non-polar p-conjugated cores show nematic and smectic C
phases over wide temperature ranges. Compounds 1a,b also form
fibrous aggregates in organic solvents. The reversible electro-
chemical reactions of 1a,b occur in the condensed columnar
liquid-crystalline state as well as in the solution state. These
TCAQ-based materials are expected to be a candidate for new
n-type liquid-crystalline semiconductors and self-assembled
insulated molecular wires.
1
vacuum to afford 1a as a bright yellow solid (0.42 g, 18%). H
NMR (400 MHz, CDCl3): d 8.31 (d, J ¼ 8.4 Hz, 2H), 8.15 (d, J ¼
2.4 Hz, 2H), 7.59 (dd, J ¼ 8.4 and 2.4 Hz, 2H), 7.40 (s, 4H), 4.10–
4.03 (m, 12H), 1.86–1.75 (m, 12H), 1.56–1.10 (m, 108H), 0.90–
0.86 (m, 18H). 13C NMR (100 MHz, CDCl3): d 164.08, 158.77,
153.93, 153.10, 143.85, 131.85, 129.31, 127.23, 126.00, 122.19,
121.55, 112.82, 112.61, 108.87, 83.58, 73.67, 69.37, 31.91, 30.33,
29.72, 29.68, 29.64, 29.62, 29.55, 29.38, 29.35, 29.27, 26.08, 22.67,
14.10. Anal. Calcd for C106H160N4O10: C, 77.14; H, 9.77; N,
3.39%. Found: C, 77.30; H, 9.92; N, 3.19%.
2,6-Bis(3,4,5-tritetradecyloxybenzoyloxy)-11,11,12,12-tetra-
cyanoanthraquinodimethane (1b). This compound was prepared
from 4b (1.89 g, 1.1 mmol), malononitrile (0.35 g, 5.3 mmol),
TiCl4 (1.2 mL), and pyridine (2.2 mL) in dry CH2Cl2 (50 mL) by
adopting the procedure used for 1a, and was obtained as a bright
Experimental section
General
1H and 13C NMR spectra were recorded on a JOEL JNM-LA400
spectrometer. Chemical shifts of H and 13C NMR signals were
1
1
yellow solid (0.60 g, 30%). H NMR (400 MHz, CDCl3): d 8.31
(d, J ¼ 8.4 Hz, 2H), 8.15 (d, J ¼ 2.4 Hz, 2H), 7.59 (dd, J ¼ 8.4 and
2.4 Hz, 2H), 7.40 (s, 4H), 4.10–4.03 (m, 12H), 1.87–1.70 (m,
12H), 1.53–1.10 (m, 132H), 0.90–0.86 (m, 18H). 13C NMR (100
MHz, CDCl3): d 164.06, 158.80, 153.94, 153.10, 143.82, 131.85,
129.32, 127.23, 126.01, 122.19, 121.56, 112.82, 112.60, 108.86,
83.57, 73.67, 69.37, 31.92, 30.34, 29.75, 29.74, 29.70, 29.68, 29.66,
29.63, 29.56, 29.39, 29.38, 29.36, 29.28, 26.08, 22.68, 14.11. Anal.
Calcd for C118H184N4O10: C, 77.93; H, 10.20; N, 3.08%. Found:
C, 77.68; H, 10.42; N, 2.84%.
quoted to tetramethylsilane (d ¼ 0.00) and CDCl3 (d ¼ 77.0) as
internal standards, respectively. The 13C NMR spectra for 5a,b
could not be taken at room temperature because of their poor
solubility in CDCl3. Elemental analyses were carried out with
a Yanaco MT-6 CHN autocorder. Differential scanning calo-
rimetry (DSC) measurements were performed on a NꢀETZSCH
DSC204 Phoenix calorimeter at a scanning rate of 5 C minꢁ1
.
Transition temperatures were taken at the onset of transition
peaks. For compound 1a, the melting temperature was deter-
mined as the peak position in the DSC traces due to the broad-
ness of the transition peak. A polarizing optical microscope
Olympus BH-51 equipped with Mettler FP82 HT hot stage was
used for visual observation. X-Ray diffraction (XRD) patterns
were obtained using a Rigaku RINT-2500 diffractmeter with
a heating stage using Ni-filtered CuKa radiation. Cyclic
voltammetry (CV) was carried out in a CH2Cl2 solution of
Bu4NClO4 (0.10 M) with Pt working and counter-electrodes, and
an Ag+/Ag reference electrode using an ALS CHI 600B electro-
chemical analyzer. In situ electrochromism studies were
conducted in a three-electrode quartz cell with the same
electrolyte system as CV using the potentiostat together with
a JASCO V-670 spectrometer. Molecular mechanics calculations
were performed with the COMPASS force-field using Accelrys
MS Modeling (v. 4.0) softwares. The density functional theory
(DFT) calculations were carried out using Wavefunction
SPARTAN’04 (v. 1.0.3) programs. The ground-state geometries
were optimized at the B3LYP/6-31G* level of theory.23
2,6-Bis(4-dodecyloxybenzoyloxy)-9,10-anthraquinone (6a). To
a mixture of 2,6-dihydroxyanthraquinone 7 (0.80 g, 3.3 mmol),
10a (2.14 g, 7.0 mmol), and 4-dimethylaminopyridine (DMAP,
0.40 g, 3.3 mmol) in dry CH2Cl2 (50 mL) was added dropwise
a solution of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide
hydrochloride (EDC, 1.91 g, 10.2 mmol) in dry CH2Cl2 (50 mL).
The mixture was stirred for 40 h at room temperature. After
quenching with water (50 mL), the product was extracted with
CHCl3. The organic layer was washed with water and dried over
anhydrous Na2SO4. After filtration and evaporation, the crude
product was purified by column chromatography (silica, CHCl3),
recrystallized from CHCl3–methanol, and dried under vacuum to
give 6a as a light-yellow solid (2.40 g, 79%). 1H NMR (400 MHz,
CDCl3): d 8.41 (d, J ¼ 8.0 Hz, 2H), 8.18–8.14 (m, 6H), 7.67 (dd, J
¼ 8.0 and 2.4 Hz, 2H), 7.00 (d, J ¼ 8.8 Hz, 4H), 4.06 (t, J ¼ 6.4
Hz, 4H), 1.85 (quint, J ¼ 6.4 Hz, 4H), 1.57–1.45 (m, 4H), 1.40–
0.95 (m, 32H), 0.89 (t, J ¼ 6.8 Hz, 6H). 13C NMR (100 MHz,
CDCl3): d 181.48, 164.08, 163.98, 155.98, 135.17, 132.53, 130.93,
129.45, 127.72, 120.51, 120.45, 114.48, 68.40, 31.91, 29.65, 29.63,
29.59, 29.55, 29.35, 29.07, 25.97, 22.69, 14.13. Anal. Calcd for
C52H64O8: C, 76.44; H, 7.90%. Found: C, 76.26; H, 7.97%.
Syntheses of TCAQ derivatives 1a,b and AQ derivatives 6a,b
2,6-Bis(3,4,5-tridodecyloxybenzoyloxy)-11,11,12,12-tetracyano-
anthraquinodimethane (1a). To a stirred mixture of 4a (2.18 g,
1.4 mmol) and malononitrile (1.39 g, 21.0 mmol) in dry CH2Cl2
(100 mL) were slowly added TiCl4 (0.8 mL) followed by pyridine
(2.2 mL) at 0 ꢀC. The mixture was refluxed for 24 h. After cooling
to room temperature, the reaction mixture was added into a large
amount of aqueous hydrochloric acid (ca. 5%). The product was
2,6-Bis(4-tetradecyloxybenzoyloxy)-9,10-anthraquinone (6b).
This compound was prepared from 7 (0.80 g, 3.3 mmol), 10b
(2.34 g, 7.0 mmol), DMAP (0.40 g, 3.3 mmol), and EDC (1.91 g,
10.2 mmol) in dry CH2Cl2 (50 mL) by adopting the procedure
used for 6a, and was obtained as a light-yellow solid (2.44 g,
4526 | J. Mater. Chem., 2008, 18, 4522–4528
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1
W. R. Dichtel, K. Isoda, T. Kato and J. F. Stoddart, Angew.
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84%). H NMR (400 MHz, CDCl3): d 8.40 (d, J ¼ 8.0 Hz, 2H),
8.18–8.14 (m, 6H), 7.67 (dd, J ¼ 8.0 and 2.4 Hz, 2H), 7.00 (d, J ¼
8.8 Hz, 4H), 4.06 (t, J ¼ 6.4 Hz, 4H), 1.83 (quint, J ¼ 6.4 Hz, 4H),
1.52–1.43 (m, 4H), 1.40–0.89 (m, 40H), 0.88 (t, J ¼ 6.8 Hz, 3H).
13C NMR (100 MHz, CDCl3): d 181.45, 164.05, 163.99, 156.01,
135.19, 132.52, 130.95, 129.43, 127.67, 120.57, 120.41, 114.50,
68.42, 31.91, 29.68, 29.66, 29.64, 29.58, 29.54, 29.35, 29.08, 25.97,
22.68, 14.10. Anal. Calcd for C56H72O8: C, 77.03; H, 8.31%.
Found: C, 76.74; H, 8.40%.
´
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Acknowledgements
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This work was partially supported by a Grant-in-Aid for
Creative Scientific Research of ‘‘Invention of Conjugated
Electronic Structures and Novel Functions’’ (No. 16GS0209)
(T.K.) from the Japan Society for the Promotion of Science
(JSPS) and by the Global COE Program for Chemistry Inno-
vation (T.K. and K.I.) from the Ministry of Education, Culture,
Sports, Science and Technology. We also thank Drs T. Nishi-
mura and T. Hatano of The University of Tokyo for helpful
discussions, and Ms K. Saeki of The University of Tokyo for
help in elemental analyses. T.Y. is grateful for financial support
from the JSPS Research Fellowship for Young Scientists.
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This journal is ª The Royal Society of Chemistry 2008
J. Mater. Chem., 2008, 18, 4522–4528 | 4527

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4528 | J. Mater. Chem., 2008, 18, 4522–4528
This journal is ª The Royal Society of Chemistry 2008