Synthesis of Poly(6-azulenylethynyl)benzene Derivatives as a Multielectron Redox System with Liquid Crystalline Behavior

Article abstract of DOI:10.1021/ja0209262

A series of poly(6-azulenylethynyl)benzenes substituted with n-hexyloxycarbonyl chains at 1,3-positions in azulene rings, i.e., hexakis-, 1,2,4,5-tetrakis-, 1,3,5-tris-, and 1,4-bis(6-azulenylethynyl)benzene derivatives 1, 2, 3, and 4b, have been prepared

Full text of DOI:10.1021/ja0209262

Published on Web 01/18/2003
Synthesis of Poly(6-azulenylethynyl)benzene Derivatives as a
Multielectron Redox System with Liquid Crystalline Behavior
Shunji Ito,*,† Haruki Inabe,† Noboru Morita,† Kazuchika Ohta,‡ Teruo Kitamura,§ and
Kimiaki Imafuku|
Contribution from the Department of Chemistry, Graduate School of Science,
Tohoku UniVersity, Sendai 980-8578, Japan, Department of Functional Polymer Science,
Faculty of Textile Science and Technology, Shinshu UniVersity, Ueda 386-8567, Japan,
Fukuoka Industry, Science & Technology Foundation, Fukuoka Industrial Technology Center,
Chikushino 818-8540, Japan, and Department of Chemistry, Faculty of Science,
Kumamoto UniVersity, Kumamoto 860-8555, Japan
Received July 8, 2002; Revised Manuscript Received October 23, 2002; E-mail: ito@funorg.chem.tohoku.ac.jp
Abstract: A series of poly(6-azulenylethynyl)benzenes substituted with n-hexyloxycarbonyl chains at 1,3-
positions in azulene rings, i.e., hexakis-, 1,2,4,5-tetrakis-, 1,3,5-tris-, and 1,4-bis(6-azulenylethynyl)benzene
derivatives 1, 2, 3, and 4b, have been prepared by a simple one-pot reaction involving repeated Pd-catalyzed
alkynylation of halogenated arenes with substituted 6-ethynylazulene and/or ethynylated arenes with
substituted 6-bromoazulene under Sonogashira-Hagihara conditions. The redox behavior of these novel
poly(6-azulenylethynyl)benzene derivatives was examined by cyclic voltammetry (CV), which revealed the
presumed multielectron redox properties. Compound 4b exhibited a one-step, two-electron reduction wave
upon CV, which revealed the formation of the dianion stabilized by two 6-azulenylethynyl substituents under
electrochemical reduction conditions. Four 6-azulenylethynyl substituents on a benzene ring in a 1,2,4,5
relationship increased the electron-accepting properties because of the formation of a stabilized closed-
shell dianionic structure, whereas 3 was reduced at more negative reduction potentials. In contrast to the
multistep redox behavior of 2, compound 1 was reduced in one step at -1.28 V upon CV. Compound 1
showed a wide temperature range of columnar mesophases (Colho and Colro) from 77.3 °C to the
decomposition temperature at ca. 270 °C. Compounds 2, 3, and 4b exhibited columnar mesomorphism
(Colro) with crystalline polymorphs for 2, unusual triple-melting behavior for 3, and both double-melting
behavior and columnar mesomorphism (Colho) for 4b. Therefore, the investigated systems exemplify a
new principle for multielectron redox behavior with liquid crystalline properties.
Introduction
recently proposed a concept of a violene-cyanine hybrid to
produce a stabilized organic electrochromic system. The hybrid
Electrochromism is observed in reversible redox systems,
which exhibit significant color changes in different oxidation
states.1 Construction of organic molecules that contain multiple
redox-active chromophores2 is fairly important for the prepara-
tion of novel polyelectrochromic materials, which respond to
different potentials with a variety of colors.3 Hu¨nig et al.4
is expected to provide a cyanine dye by an overall two-electron
transfer as illustrated by the general structure in Scheme 1.
Recently, we have proposed that the redox system of
unknown hexa(6-azulenyl)benzene is assumed as the hybrid in
which the closed-shell cyanine-type structure would be also
generated by the two-electron reduction (Chart 1).5 Herein we
point out the possibility for the construction of polyelectro-
chromic materials utilizing polyethynylbenzenes as a platform
bearing multiple azulenes (C10H8) as redox-active chromophores.
Hexakis(6-azulenylethynyl)benzene (1) should act as a three-
step redox system, which will provide stabilized closed-shell
dianion 1red-2, tetraanion 1red-4, and hexaanion 1red-6 by overall
two-, four-, and six-electron transfers and could be expected to
show significant change in the absorption spectra in the different
oxidation states because the azulene system has a remarkable
* Corresponding author. Tel: +81-22-217-7714. Fax: +81-22-217-7714.
† Tohoku University.
‡ Shinshu University.
§ Fukuoka Industrial Technology Center.
| Kumamoto University.
(1) Monk, P. M. S.; Mortimer, R. J.; Rosseinsky, D. R. Electrochromism:
Fundamentals and Applications; VCH: Weinheim, Germany, 1995.
(2) Deuchert, K.; Hu¨nig, S. Angew. Chem., Int. Ed. Engl. 1978, 17, 875-886.
(3) (a) Komatsu, T.; Ohta, K.; Fujimoto, T.; Yamamoto, I. J. Mater. Chem.
1994, 4, 533-536. (b) Rosseinsky, D. R.; Monk, D. M. S. J. Appl.
Electrochem. 1994, 24, 1213-1221.
(4) (a) Hu¨nig, S.; Kemmer, M.; Wenner, H.; Perepichka, I. F.; Ba¨uerle, P.;
Emge, A.; Gescheid, G. Chem. Eur. J. 1999, 5, 1969-1973. (b) Hu¨nig, S.;
Kemmer, M.; Wenner, H.; Barbosa, F.; Gescheidt, G.; Perepichka, I. F.;
Ba¨uerle, P.; Emge, A.; Peters, K. Chem. Eur. J. 2000, 6, 2618-2632. (c)
Hu¨nig, S.; Perepichka, I. F.; Kemmer, M.; Wenner, H.; Ba¨uerle, P.; Emge,
A. Tetrahedron 2000, 56, 4203-4211. (d) Hu¨nig, S.; Langels, A.; Schmittel,
M.; Wenner, H.; Perepichka, I. F.; Peters, K. Eur. J. Org. Chem. 2001,
1393-1399.
(5) (a) Ito, S.; Inabe, H.; Okujima, T.; Morita, N.; Watanabe, M.; Imafuku, K.
Tetrahedron Lett. 2000, 41, 8343-8347. (b) Ito, S.; Inabe, H.; Okujima,
T.; Morita, N.; Watanabe, M.; Nobuyuki, H.; Imafuku, K. Tetrahedron
Lett. 2001, 42, 1085-1089. (c) Ito, S.; Inabe, H.; Okujima, T.; Morita, N.;
Watanabe, M.; Nobuyuki, H.; Imafuku, K. J. Org. Chem. 2001, 66, 7090-
7101.
9
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J. AM. CHEM. SOC. 2003, 125, 1669-1680
1669

A R T I C L E S
Ito et al.
Scheme 1
Chart 2
Chart 1
tendency to stabilize carbanions owing to its high polarizability
(Chart 2).6 The presumed cyanine-type structures formed by
two- and four-electron reduction of 1 are represented by the
bold line in Scheme 2.
We also report herein the successful synthesis of poly(6-
azulenylethynyl)benzenes 2-4 for the comparison with the
electrochemical properties of 1 (Chart 2). Compound 2 also
could be assumed as a violene-cyanine hybrid in the point of
the generation of a closed-shell cyanine-type structure by two-
electron reduction. Compound 4 is a typical example for the
general violene system and 3 exemplifies the redox system
without conjugation in each azulenyl group.
Due to the hexyloxycarbonyl chains substituted at 1 and 3
positions on each azulenyl group, we anticipated these mole-
cules would possess good solubility, fusibility, and the ability
to self-organize in columnar mesophases.7 The stacking behavior
of discotic liquid crystals (LCs) provides opportunities for
materials with one-dimensional transport processes such as
energy migration, electric conductivity, and photoconductivity.8
An EC-LC cell for laser beam writing is proposed for an
application of the electrochromic materials with liquid crystalline
properties.9 We also report herein the liquid crystalline behaviors
of 1-4, which are the first examples exhibiting both multiple
melting behavior and columnar mesomorphism in the chemistry
of azulenes.
Results and Discussion
Synthesis. Poly(6-azulenylethynyl)benzenes 1-4 were pre-
pared by a simple one-pot reaction involving repeated Pd-
(6) Zeller, K.-P. Azulene. In Houben-Weyl; Methoden der Organischen Chemie;
4th ed.; Georg Thieme: Stuttgart, Germany, 1985; Vol. V, Part 2C, pp
127-418.
catalyzed alkynylation of halogenated arenes with substituted
6-ethynylazulene and/or ethynylated arenes with substituted
6-bromoazulene under Sonogashira-Hagihara conditions.10,11
The preparation of diethyl 6-ethynylazulene-1,3-dicarboxylate
(5a) was reported elsewhere.5 Pd(0)-catalyzed reaction of 5a
with 1,4-diiodobenzene (6) afforded the desired bisadduct 4a
(7) (a) Kohne, B.; Praefcke, K. Chimia 1987, 41, 196-198. (b) Praefcke, K.;
Kohne, B.; Singer, D.; Demus, D.; Pelzi, G.; Diele, S. Liq. Cryst. 1990, 7,
589-594. (c) Booth, C. J.; Kru¨erke, D.; Heppke, G. J. Mater. Chem. 1996,
6, 927-934.
(8) (a) Adam, D.; Schuhmacher, P.; Simmerer, J.; Ha¨ussling, L.; Siemensmeyer,
K.; Etzbach, K. H.; Ringsdorf, H.; Haarer, D. Nature 1994, 371, 141-
143. (b) Van de Craats, A. M.; De Haas, M. J.; Warman, J. M. Synth. Met.
1997, 86, 2125-2126. (c) Van de Craats, A. M.; Warman, J. M.; Hasebe,
H.; Naito, R.; Ohta, K. J. Phys. Chem. B 1997, 101, 9224-9232. (d) Van
de Craats, A. M.; Warman, J. M.; Mu¨llen, K.; Geerts, Y.; Brand, J. D.
AdV. Mater. 1998, 10, 36-38.
(9) (a) Nakamura, K.; Kaneko, S.; Ito, Y.; Hirabayashi, H.; Ogura, K. J. Appl.
Phys. 1982, 53, 1792-1796. (b) Nakamura, K.; Nakada, K.; Ito, Y.; Koishi,
E. J. Appl. Phys. 1983, 57, 135-140.
(10) Hafner et al. reported the ethynylation of azulenes in a five-membered ring
utilizing Pd-catalyzed cross-coupling reaction and the preparation of
benzene-bridged poly(1-alkynylazulene)s: (a) Fabian, K. H. H.; Elwahy,
A. H. M.; Hafner, K. Tetrahedron Lett. 2000, 41, 2855-2858. (b) Elwahy,
A. H. M.; Hafner, K. Tetrahedron Lett. 2000, 41, 2859-2862. (c) Elwahy,
A. H. M.; Hafner, K. Tetrahedron Lett. 2000, 41, 4079-4083.
9
1670 J. AM. CHEM. SOC. VOL. 125, NO. 6, 2003

Poly(6-azulenylethynyl)benzene Derivatives
A R T I C L E S
Scheme 2
Scheme 3
Scheme 4
substituents at 1,3-positions in azulene rings were prepared by
the coupling reaction.
Preparation of 6-ethynylazulene with hexyloxycarbonyl chains
commenced with diethyl 6-bromoazulene dicarboxylate (9a)12
was outlined in Scheme 4. The cross-coupling reaction of 5b
with 1,4-diiodobenzene (6) in the presence of Pd(0) catalyst
afforded a mixture of bisadduct 4b and monoadduct 7b in 43%
and 18% yields, respectively, together with diacetylene 8 in 16%
yield (Scheme 4). Formation of 8 is presumably attributable to
the low reactivity of 5b with the aryl halide 6 under the cross-
coupling conditions.13 Likewise, the reaction of 9 with 1,2,4,5-
in 25% yield together with monoadduct 7a in 12% yield
(Scheme 3). However, the product 4a exhibited fairly low
solubility in common organic solvents. For this reason, poly-
(6-azulenylethynyl)benzenes substituted with hexyloxycarbonyl
(11) (a) Sonogashira, K. ComprehensiVe Organic Synthesis; Trost, B. M.,
Fleming, I., Eds.; Pergamon Press: Oxford, U.K., 1991; Vol. 3, Chapt.
2.4, pp 521-549. (b) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.;
Hagihara, N. Synthesis 1980, 627-630. (c) Sonogashira, K.; Tohda, Y.;
Hagihara, N. Tetrahedron Lett. 1975, 4467-4470.
(12) McDonald, R. N.; Richmond, J. M.; Curtis, J. R.; Petty, H. E.; Hoskins, T.
L. J. Org. Chem. 1976, 41, 1811-1821.
(13) (a) Rossi, R.; Carpita, A.; Bigelli, C. Tetrahedron Lett. 1985, 26, 523-
526. (b) Takahashi, A.; Endo, T.; Nozoe, S. Chem. Pharm. Bull. 1992, 40,
3181-3184.
9
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A R T I C L E S
Ito et al.
Scheme 5
Scheme 6
Scheme 7
Figure 1. Spectra of 1 (s), 2 (---), 3 (‚‚‚), and 4b (- ‚ -) in (a) UV-vis
and (b) visible region in chloroform.
Scheme 8
tetraiodobenzene (11)14 gave 2 and 12 in 25% and 20% yields,
respectively, together with 8 in 5% yield (Scheme 5). However,
attempts made toward the 6-fold ethynylation of hexaiodoben-
zene (13) with 5b did not afford the desired 1 even in a small
amount.
The inverse cross-coupling reaction of dihexyl 6-bromoazu-
lene-1,3-dicarboxylate (9b) with hexaethynylbenzene (14)15
prepared in solution via hexakis(trimethylsilylethynyl)benzene
(15) in the presence of Pd(0) catalyst afforded the desired 1 in
55% yield (Scheme 6). It is noteworthy that unstable 14 could
be utilized in the 6-fold Sonogashira reaction without isolation.
Compound 2 was also obtained by the reaction of 9b with
1,2,4,5-tetraethynylbenzene (16)16 generated in situ via 1,2,4,5-
tetrakis(trimethylsilylethynyl)benzene (17) in 66% yield (Scheme
7). Likewise, the reaction of 9b with 1,3,5-triethynylbenzene
(18)17 prepared from 1,3,5-tris(trimethylsilylethynyl)benzene
(19) also afforded 3 in 96% yield (Scheme 8).
Poly(6-azulenylethynyl)benzenes substituted with n-hexyl-
oxycarbonyl chains, 1-3 and 4b, possess fair solubility in
chloroform, dichloromethane, and so on. These compounds are
stable, showing no decomposition even after several weeks at
room temperature. The products 1-4 were fully characterized
by the spectral data as shown in the Experimental Section. Mass
spectra of 3 and 4b ionized by FAB showed correct M+ and
M+ - OC6H13 ion peaks, but higher molecular compounds could
not be ionized by the method. Mass spectra of 1 and 2 were
obtained by ESI-TOF MS, which exhibited the correct M+
+
(14) Mattern, D. L. J. Org. Chem. 1984, 49, 3051-3053.
(15) Diercks, R.; Armstrong, J. C.; Boese, R.; Vollhart, K. P. C. Angew. Chem.,
Int. Ed. Engl. 1986, 25, 268-269.
(16) (a) Berris, B. C.; Hovakeemian, G. H.; Lai, Y.-H.; Mestdagh, H.; Vollhardt,
K. P. C. J. Am. Chem. Soc. 1985, 107, 5670-5687. (b) Berris, B. C.;
Hovakeemian, G. H.; Vollhart, K. P. C. J. Chem. Soc., Chem. Commun.
1983, 502-503.
(17) (a) Osawa, M.; Sonoki, H.; Hoshino, M.; Wakatsuki, Y. Chem. Lett. 1998,
1081-1082. (b) Anderson, H. L.; Walter, C. J.; Vidal-Ferran, A.; Hay, R.
A.; Lowden, P. A. J. Chem. Soc., Perkin Trans. 1 1995, 2275-2279. (c)
Royles, B. J. L.; Smith, D. M. J. Chem. Soc., Perkin Trans. 1 1994, 355-
358.
Na ion peak. UV-vis spectra of 1-3 and 4b in chloroform are
shown in Figure 1. They showed characteristic weak absorption
of the azulene system in the visible region. The longest
absorption maxima of 1-3 and 4b in the visible region exhibited
a slight bathochromic shift in the order of the number of azulene
rings owing to the extension of the π-system.
Disc-type molecules have a tendency to form aggregates in
solution, which causes significant line broadening and shielding
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1672 J. AM. CHEM. SOC. VOL. 125, NO. 6, 2003

Poly(6-azulenylethynyl)benzene Derivatives
A R T I C L E S
Table 1. Reduction Potentialsa of Compounds 1-3, 4b, and 12
sample
E1red, V
E2red, V
E3red, V
E4red, V
1
2
12
3
(-1.28) (6e)
-1.08 (2e)
-1.10 (2e)
(-1.39) (3e)
-1.19 (2e)
-1.28 (2e)
(-1.28) (1e)
(-2.10)
(-2.05)
(-1.84)
(-1.98)
4b
(-1.97)
a The redox potentials were measured by cyclic voltammetry (CV) or
differential pulse voltammetry (DPV) (0.1 M Bu4NBF4 in o-dichlorobenzene,
Pt electrode, scan rate 100 mV/s-1, and Fc+/Fc ) 0.26 V). In the case of
irreversible waves, which are shown in parentheses, Eox and Ered were
calculated as Epa (anodic peak potential) - 0.03 V and Epc (cathodic peak
potential) + 0.03 V, respectively.
1
in their NMR spectra.18 Concentration dependence of the H
NMR spectrum of 1 exhibited some intermolecular aggregation
in solution due to the π-π interaction of aromatic cores.
Increasing the concentration of 1 causes a high-field shift of
the aromatic signals with considerable line broadening in the
1H NMR spectra owing to the results in the larger aggregates
formed.
Cyclic Voltammetry. Redox potentials (in volts vs Ag/Ag+)
of 1-3 and 4b measured by cyclic voltammetry (CV) are
summarized in Table 1. Compound 4b showed a reversible two-
electron transfer at -1.19 V upon CV (Figure 2d). The shape
of CV does not exhibit real one-step, two-electron transfer.
Therefore, the observed overall two-electron transfer in 4b
means the low semiquinone formation constant (KSEM) in the
redox system (Scheme 9). Similar one-step, two-electron
reduction with a low KSEM value has been observed in the 6,6′-
biazulenyl separated by six methine groups.19 The acetylenic
and aromatic core in 4 would reduce coulomb repulsion further
due to the larger distance of the charges.
Compound 3 exhibited an irreversible broad reduction wave,
centered at around -1.39 V (Figure 2c). Compound 3 shows a
potential gap of about 20 mV, which is less, as compared with
that of 4b, because the three 6-azulenylethynyl substituents on
benzene in a 1,3,5 relationship cannot take a closed-shell
dianionic structure like 4 as shown in Scheme 9.
In contrast to the one-step reduction of 3, 1,2,4,5-tetrakis(6-
azulenylethynyl)benzene 2 exhibited a barely separated two-
step reduction wave at E1/2 ) -1.08 and -1.28 V upon CV
(Figure 2b). The electrochemical reduction of 1,2,4-tris(6-
azulenylethynyl)-5-iodobenzene 12 exhibited a similar two-step
reduction wave, but the wave was characterized by a two-
electron reduction wave at -1.10 V and a one-electron transfer
at -1.28 V. Therefore, the two waves observed by the reduction
of 2 must correspond to the transfer of two electrons in both
cases. Consequently, the redox system of 2 could be illustrated
as a violene-cyanine hybrid and could exhibit a significant color
change in a different oxidation state. The presumed cyanine-
type structure formed by the two-electron reduction is repre-
sented by the bold line in Scheme 10.
Hexakis(6-azulenylethynyl)benzene (1) exhibited a quasi-
reversible broad reduction wave, centered at around -1.28 V
at the scan rate of 100 mV/s (Figure 2a). The wave was barely
separated into two waves, at -1.12 and -1.23 V, by differential
pulse voltammetry (DPV). We further extended the scan down
to -2.5 V, but no other peaks were observed. Therefore, the
Figure 2. Cyclic voltammograms of (a) 1 (0.5 mM), (b) 2 (1 mM), (c) 3
(1 mM), and (d) 4b (1 mM) in o-dichlorobenzene containing Bu4NBF4 (0.1
M) as a supporting electrolyte.
(18) Watson, M. D.; Fechtenko¨tter, A.; Mu¨llen, K. Chem. ReV. 2001, 101, 1267-
1300.
(19) Hu¨nig, S.; Ort, B. Liebigs Ann. Chem. 1984, 1959-1971.
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A R T I C L E S
Ito et al.
Scheme 9
Compound 1 showed a very wide temperature range of
columnar mesophases (Colho and Colro) from 77.3 °C to the
decomposition temperature at ca. 270 °C. This is the first
instance of the columnar mesophase in azulenic compounds.21,22
When the virgin state of 1 [K(v) crystal phase] was heated at
77.3 °C, the K(v) phase transformed into a Colho mesophase.
On further heating, the phase exhibited phase transition to a
Colro (C2/m) mesophase. On further heating, the Colro phase
decomposed at around 270 °C. We could not observe any texture
changes between the Colho and Colro phases in 1 by microscopic
observations owing to the high viscosity of these two meso-
phases. However, unequivocal characterization of each state was
confirmed by X-ray diffraction experiments, which exhibited a
diffuse band around 2θ ) 20° in the wide-angle region,
corresponding to the melt of the hexyloxycarbonyl chains. The
patterns revealed the columnar structures (Colho and Colro) of
the two phases (Figure 4).
wave should be attributable to the six-electron transfer in one-
step to generate a hexaanionic species 1red-6. Under the same
conditions, with an increased scan rate, the peak separation is
increased to ∆E ) 599 mV (500 mV/s). The scan rate
dependence should be attributable to the conditions of the
measurement because the peak separation of a ferrocenium/
ferrocene (Fc+/Fc) couple was also observed as 353 mV at a
scan rate of 500 mV/s.
Electrochromic Behavior. UV-vis measurement of 1-3 and
4b was examined to clarify the formation of a closed-shell
cyanine-type structure under the electrochemical reduction
conditions. A constant-current reduction was applied to the
solutions of 1-3 and 4b, with platinum wires for the working
electrode and counterelectrode. When the UV-vis spectra of 1
and 2 were measured in o-dichlorobenzene containing Bu4NBF4
(0.1 M) at room temperature under the electrochemical reduction
conditions, a new absorption in the visible region was gradually
developed as shown in Figure 3. The color of the solution of 1
and 2 gradually changed from brown to black and pink,
respectively, during the electrochemical reduction. Rather well-
developed isosbestic points in the UV-vis spectra suggest the
formation of a new species in solution. Thus, the color change
of the solutions would be attributed to the formation of a
cyanine-type structure in the two-electron reduction. However,
the reverse oxidation of the colored solutions of 1 and 2
exhibited the bleaching of the color but not regeneration of the
UV-vis spectra of the neutral 1 and 2, although the reversibility
was observed upon CV. These results indicate the low stability
of the presumed anionic species under the conditions of the
UV-vis measurement. Several acetylenes with pyridinyl end
groups have been reported to afford extremely sensitive reduc-
tion products.20 Therefore, the instability of the reduced species
must be attributable to rapid polymerization of the cumulenes
formed by the two-relectron reduction.
We also tried electrochemical reduction of 3 and 4b under
UV-vis monitoring, although these two compounds do not take
a cyanine-type structure by the electrochemical reduction. In
these cases, however, we could not obtain any evidence of the
formation of a presumed radical anionic and/or dianionic species.
Absence of the reversibility for the reduction of 3 and 4b also
suggests the instability of the presumed reduction products under
the conditions of the UV-vis measurement.
Liquid-Crystalline Properties. Phase transition behavior of
1-3 and 4b was examined with a polarizing microscope
equipped with a heating plate controlled by a thermoregulator
and measured with a differential scanning calorimeter (DSC).
To distinguish between the solid polymorphs in the compounds,
X-ray diffraction powder patterns were also measured with Cu
KR radiation. In Table 2 are summarized the phase transition
temperatures and phase transition enthalpy changes for 1-3 and
4b. The assignments of X-ray reflections of each of the
mesophases are summarized in Table 3. The detailed thermal
behaviors of these compounds are described below.
Compound 2 exhibited mesomorphism with crystalline pol-
ymorphs, K1 and K2. The solid obtained by the recrystallization
(chloroform) of 2 was in amorphous state, which was revealed
by X-ray diffraction experiments. When the virgin sample
[amorphous solid (v)] was heated from room temperature, it
crystallized gradually to afford K1 crystals, which exhibited the
solid-solid transition at 188.1 °C to give K2 crystals. On further
heating the sample to 215.0 °C, the K2 crystals transformed into
a columnar mesophase. The X-ray diffraction patterns of the
mesophase at 230 °C are shown in Figure 5. The 13 narrow
reflections in the low-angle region correspond to the columnar
structure [Colro (P2/a)] of the mesophase with the lattice
constants in a two-dimensional rectangular lattice, a ) 43.3 Å,
b ) 53.2 Å. However, microscopic observations of the Colro
phase in 2 also did not reveal any texture changes due to the
high viscosity.
Compound 3 exhibited unusual multiple-melting behavior.
Recrystallization of 3 (chloroform) afforded a crystalline phase,
which was denoted as K2(v). The double melting behavior of
the K2(v) phase was confirmed by DSC thermograms for all of
the heating rates (1-40 °C/min) as shown in Figure 6. The two
endothermic peaks II and IV on the thermograms correspond
to the melting of K2(v) and K3 crystals, respectively. Exothermic
peak III, between peaks II and IV, corresponds to the recrys-
tallization from the melt of K2 crystals to K3 ones. The ratio of
peak II [melting of K2(v) phase] to peak IV (melting of K3
phase) increases with faster heating rate. The solid-solid phase
transition from K2(v) to K3 should correspond to peak I at around
60 °C.
The K1 crystal phase including an unidentified X phase
appeared on rapid cooling of an isotropic liquid heated over
the melting point of the K3 crystalline phase down to room
temperature. The DSC thermograms of the rapid-cooled sample
for different heating rates are shown in Figure 7. Endothermic
peak I and exothermic peak II on the thermograms should
correspond to the melting of the X phase and the recrystallization
from the melt of the phase to K1 crystals, respectively. Since
the phase transition from K1 to K2 was observed by microscopic
(21) (a) Praefcke, K.; Schmidt, D. Z. Naturforsch., B: Anorg. Chem., Org. Chem.
1981, 36B, 375-378. (b) Estdale, S. E.; Brettle, R.; Dunmur, D. A.; Marson,
C. M. J. Mater. Chem. 1997, 7, 391-401.
(22) (a) Morita, T.; Kaneko, M. Jpn. Pat. 03261745, 1991. (b) Morita, T.;
Kaneko, M. Jpn. Pat. 03261754, 1991. (c) Morita, T.; Kaneko, M. Jpn.
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(20) Hu¨nig, S.; Berneth, H. Top. Curr. Chem. 1980, 92, 1-44.
9
1674 J. AM. CHEM. SOC. VOL. 125, NO. 6, 2003

Poly(6-azulenylethynyl)benzene Derivatives
A R T I C L E S
Scheme 10
melt of K1(v) crystals, when the sample in photo a was
heated to 158.2 °C. The K2 crystals were gradually solidified
from the melt by holding the temperature at 158.2 °C for 30
min (photo c). The state change in photo c proceeded further
by holding the temperature at 158.2 °C for 120 min (photo d).
Photo e shows the growing of the K2 crystals by holding the
temperature at 158.2 °C for more than 480 min. When the
sample in photo e was heated from 158.2 °C, the K2 crystals
started to melt at 161.2 °C (photo f). The K2 crystals melted,
completely, when the sample in photo e was heated to 162.0
°C (photo g).
Thus, the double melting behavior of compound 4b was
revealed by the polarizing microscopic observations. On the
other hand, since the solid-solid phase transition from K1(v)
to K2 and the relaxation of the melt of K1(v) to K2 are slow,
the DSC measurements of the K1(v) sample gave a single
melting thermogram corresponding to the melting of the K1(v)
phase for any heating rate (1-10 °C/ min).
When the isotropic liquid of 4b was cooled rapidly, the sam-
ple gave the mesophase, which showed a texture for the well-
known developable units characteristic of columnar mesophases
(Figure 10). The X-ray diffraction pattern of the mesophase at
room temperature confirmed it as a hexagonal columnar
structure (Colho phase) with the lattice constant a ) 34.9 Å
(Figure 11). Assuming a specific gravity of 1.2 g cm-3, we can
estimate the average number of molecules per unit cell as 3.1
molecules per 3.62 Å separation along the axis of the columns.
This number of molecules per unit cell and the rodlike molecular
shape are not typical for the 2D-hexagonal columnar system.
Thus, the hexagonal symmetry of the mesophase of 4b is rather
unexpected.
The terms phasmid and phasmidic phase are proposed for
the mesomorphic properties of molecules with a rodlike rigid
core ending in two half-disk-shaped moieties.23 The organization
of 4b may correspond to the stacking of the three rodlike
molecules into a disk similar to the phasmidic phases. Thus,
we can assume that the three molecules of 4b form a cluster to
arrange into a columnar mesophase according to a two-
dimensional hexagonal lattice. The Colho phase showed relax-
ation to the K2 phase at around 65 °C. However, the melting of
the Colho phase could be detected at 148.3 °C by DSC and
polarizing microscope heating the sample cooled to 135 °C from
the isotropic liquid. Consequently, the schematic G-T diagram
of 4b can be depicted as shown in Figure 12. The multiple-
Figure 3. Continuous change in visible spectrum of (a) 1 (10 mL; 0.6 ×
10-5 M) and (b) 2 (10 mL; 0.9 × 10-5 M) in o-dichlorobenzene containing
Bu4NBF4 (0.1 M) upon constant-current electrochemical reduction (40 and
30 µA, respectively) at 10-min intervals.
observations, the exothermic peak II could include that of the
phase transition. Endothermic peaks III and V on the thermo-
grams correspond to the melting of K1 and K2 phases,
respectively. Exothermic peak IV, between peaks III and V,
corresponds to the recrystallization from the melt of K1 crystals
to K2 ones. Consequently, the phase transition of 3 can be
reasonably explained by using a Gibbs free energy versus
temperature (G-T) diagram as shown in Figure 8.
Double melting behavior was observed for compound 4b.
Photomicrographs in Figure 9 show a sequence of the state
changes for 4b. Photo a shows the K1(v) crystals obtained by
recrystallization (chloroform) at 150.0 °C. Photo b exhibits the
(23) (a) Maltheˆte, J.; Levelut, A. M.; Tinh, N. H. J. Phys. Lett. 1985, 46, 875-
880. (b) Nguyen, H.-T.; Destrade, C.; Maltheˆte, J. AdV. Mater. 1997, 9,
375-388.
9
J. AM. CHEM. SOC. VOL. 125, NO. 6, 2003 1675

A R T I C L E S
Ito et al.
Table 2. Phase Transition Temperature (T) and Enthalpy Changes (∆H) of Compounds 1-3 and 4b
a Phase nomenclature: K ) crystal; Colho ) discotic hexagonal columnar ordered mesophase; Colro ) rectangular columnar odered mesophase; A.S. )
amorphus solid; X, Y ) unidentified phases; and I.L. ) isotropic liquid. (v) Fresh virgin state obtained by recrystallization from solvent. b Phase transition
temperature (T) and enthalpy change (∆H) are determined by DSC.
Dihexyl 6-Bromoazulene-1,3-dicarboxylate (9b). A solution of 9a
(5.00 g, 14.2 mmol), 1-hexanol (75.0 g, 734 mmol), and concentrated
H2SO4 (4 mL) was stirred at 100 °C for 5 days. The reaction mixture
was poured into water and extracted with toluene. The organic layer
was washed with water, dried over MgSO4, and concentrated. The
residue was purified by column chromatography on silica gel with
CH2Cl2 to afford 9b (5.26 g, 80%) as red prisms: mp 115-117 °C
(methanol); MS (70 eV) m/z (relative intensity) 464 (M+ + 2, 100),
462 (M+, 98), 361 (M+ - OC6H13, 29), 294 (M+ - 2C6H12, 45), 277
melting behavior of 3 and 4b is thought of as thermal behavior
close to mesomorphism.24
Conclusions
Poly(6-azulenylethynyl)benzenes 1-4 substituted with n-
hexyloxycarbonyl chains have been synthesized. Compounds
1-4 represented the presumed differences in the electron-
transfer ability as a function of the relationship of the substituted
positions. Compounds 1 and 2 exhibited color change under
the electrochemical reduction. However, in the case of 1, its
electrochemical behavior was not ideal, probably due to the
unfavorable steric interactions with two equal neighbors. With
the systems 2-4, all the electrochemical features could be
verified, although not in an ideal way owing to the instability
of the charged species. The poly(6-azulenylethynyl)benzenes
1, 2, and 4b also showed columnar mesomorphism. The multi-
ple-melting behavior was also observed in 2, 3, and 4b. Thus,
these system could be utilized to construct advanced materials
for electrochromic application with liquid crystalline behavior.
(M+ - OC6H13 - C6H12, 36); IR (KBr) νmax 1678 (s, CdO) cm-1
;
UV-vis (CHCl3) λmax 274 (log ꢀ 4.33), 317 (4.79), 349 (3.94), 380
1
(3.95), 513 (2.77) nm; H NMR (400 MHz, CDCl3) δ ) 9.49 (d, J )
11.3 Hz, 2H, H4,8), 8.80 (s, 1H, H2), 8.03 (d, J ) 11.3 Hz, 2H, H5,7),
4.37 (t, J ) 6.7 Hz, 4H, H1′), 1.82 (tt, J ) 7.5, 6.7 Hz, 4H, H2′), 1.49
(m, 4H, H3′), 1.42-1.34 (m, 8H, H4′,5′), 0.92 (m, 6H, H6′); 13C NMR
(100 MHz, CDCl3) δ ) 164.7 (CO), 143.6 (C2), 142.2 (C3a,8a), 138.5
(C6), 137.2 (C4,8), 133.7 (C5,7), 117.9 (C1,3), 64.5 (C1′), 31.5 (C4′), 28.8
(C2′), 25.8 (C3′), 22.5 (C5′), 14.0 (C6′). Anal. Calcd for C24H31BrO4: C,
62.20; H, 6.74; Br, 17.24. Found: C, 62.12; H, 6.80; Br, 17.33.
Dihexyl 6-Trimethylsilylethynylazulene-1,3-dicarboxylate (10).
TMSA (847 mg, 8.63 mmol) was added to a solution of 9b (2.00 g,
4.32 mmol), PPh3 (111 mg, 0.423 mmol), CuI (81 mg, 0.43 mmol),
and PdCl2(PPh3)2 (151 mg, 0.215 mmol) in triethylamine (26 mL) and
toluene (95 mL). The resulting mixture was stirred at room temperature
for 3 h under an Ar atmosphere. The reaction mixture was poured into
10% NH4Cl solution and extracted with CH2Cl2. The organic layer was
washed with water, dried over MgSO4, and concentrated. The residue
was purified by column chromatography on silica gel with 5% ethyl
acetate/hexane to afford 10 (2.07 g, 100%) as purple needles: mp 83-
85 °C (hexane); MS (70 eV) m/z (relative intensity) 480 (M+, 100); IR
(KBr) νmax 2147 (m, CtC), 1698 (s, CdO) cm-1; UV-vis (CHCl3)
λmax 277 (log ꢀ 4.21), 330 (4.86), 360 (4.29), 368 (4.33), 537 (2.79)
nm; 1H NMR (400 MHz, CDCl3) δ ) 9.63 (d, J ) 11.1 Hz, 2H, H4,8),
Experimental Section
General Methods. For general experimental details and instrumenta-
tion, see our earlier publication.25
(24) (a) Ohta, K.; Muroki, H.; Hatada, K.; Takagi, A.; Ema, H.; Yamamoto, I.;
Matsuzaki, K. Mol. Cryst. Liq. Cryst. 1986, 140, 163-177. (b) Ohta, K.;
Muroki, H.; Hatada, K.; Yamamoto, I.; Matsuzaki, K. Mol. Cryst. Liq. Cryst.
1985, 130, 249-263. (c) Ohta, K.; Takenaka, O.; Hasebe, H.; Morizumi,
Y.; Fujimoto, T.; Yamamoto, I. Mol. Cryst. Liq. Cryst. 1991, 195, 103-
121.
(25) Ito, S.; Okujima, T.; Morita, N. J. Chem. Soc., Perkin Trans. 1 2002, 1896-
1905.
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1676 J. AM. CHEM. SOC. VOL. 125, NO. 6, 2003

Poly(6-azulenylethynyl)benzene Derivatives
A R T I C L E S
Table 3. X-ray Diffraction Data of the Mesophase of 1, 2, and 4b
spacing, Å
lattice constant, Å
measured
calculated
Miller indices (hkl)
compound 1 (Colho at 165 °C)
a ) 30.4
25.7
14.8
13.5
8.79
7.74
6.77
6.13
4.72
4.39
ca. 4.2
3.53
26.4
15.2
13.2
(100)
(110)
(200)
(300)
(220)
(400)
(320)
(510)
(600)
b
h ) 3.53
Z ) 1.0 for Fa ) 1.50
8.79
7.61
6.59
6.05
4.73
4.39
(001)
compound 1 [Colro(C2/m) at 210 °C]
a ) 56.2
28.1
25.8
16.0
14.5
13.1
ca. 4.6
3.77
28.1
25.8
15.8
14.5
12.9
(200)
(110)
(310)
(020)
(220)
b
b ) 29.1
h ) 3.77
Z ) 2.0 for F a ) 1.35
(001)
compound 2 (Colro(P2/a) at 230 °C)
a ) 43.3
26.6
21.6
19.5
15.0
14.2
13.5
10.5
8.91
8.63
7.82
7.14
6.67
6.20
ca. 4.5
3.54
26.6
21.6
20.0
14.4
13.9
13.3
10.6
(020)
(200)
(210)
(300)
(310)
(040)
(410)
(060)
(500)
(530)
(610)
(630)
(560)
b
b ) 53.2
h ) 3.54
Z ) 4.0 for Fa ) 1.40
Figure 4. X-ray diffraction powder patterns of 1: Colho mesophase at 165
°C (upper) and Colro (C2/m) mesophase at 210 °C (lower).
8.86
8.66
7.78
7.15
6.68
6.19
(001)
compound 4b (Colho at room temp)
a ) 34.9
30.2
17.6
15.2
11.5
10.1
ca. 4.8
3.62
30.2
17.5
15.1
11.4
10.1
(100)
(110)
(200)
(210)
(300)
b
h ) 3.62
Z ) 3.1 for Fa ) 1.20
(001)
a Assumed density (grams per cubic centimeter). b Halo of molten
hexyloxycarbonyl chains.
8.77 (s, 1H, H2), 7.84 (d, J ) 11.1 Hz, 2H, H5,7), 4.37 (t, J ) 6.9 Hz,
4H, H1′′), 1.82 (tt, J ) 7.5, 6.9 Hz, 4H, H2′′), 1.49 (m, 4H, H3′′), 1.42-
1.34 (m, 8H, H4′′,5′′), 0.92 (m, 6H, H6′′), 0.32 (s, 9H, 2′-TMS); 13C NMR
(100 MHz, CDCl3) δ ) 164.9 (CO), 143.8 (C2), 143.5 (C3a,8a), 137.5
(C4,8), 135.9 (C6), 133.5 (C5,7), 117.0 (C1,3), 107.5 (C1′), 101.3 (C2′),
64.4 (C1′′), 31.5 (C4′′), 28.9 (C2′′), 25.8 (C3′′), 22.6 (C5′′), 14.0 (C6′′),
-0.3 (2′-TMS). Anal. Calcd for C29H40SiO4: C, 72.46; H, 8.39.
Found: C, 71.86; H, 8.50.
Figure 5. X-ray diffraction powder patterns of Colro (P2/a) mesophase
for 2 at 230 °C.
2H, H4,8), 8.79 (s, 1H, H2), 7.86 (d, J ) 11.3 Hz, 2H, H5,7), 4.37 (t, J
) 6.7 Hz, 4H, H1′′), 3.48 (s, 1H, H2′), 1.83 (tt, J ) 7.5, 6.7 Hz, 4H,
H2′′), 1.50 (m, 4H, H3′′), 1.42-1.34 (m, 8H, H4′′,5′′), 0.92 (m, 6H, H6′′);
13C NMR (100 MHz, CDCl3) δ ) 164.8 (CO), 144.1 (C2), 143.6 (C3a,8a),
137.5 (C4,8), 134.7 (C6), 133.5 (C5,7), 117.2 (C1,3), 86.2 (C1′), 82.3 (C2′),
64.4 (C1′′), 31.5 (C4′′), 28.9 (C2′′), 25.8 (C3′′), 22.6 (C5′′), 14.0 (C6′′).
Anal. Calcd for C26H32O4: C, 76.44; H, 7.90. Found: C, 76.47; H,
8.02.
1,4-Bis[1,3-bis(hexyloxycarbonyl)-6-azulenylethynyl]benzene (4b).
To a degassed solution of 5b (311 mg, 0.761 mmol), 6 (100 mg, 0.303
mmol), CuI (2 mg, 0.01 mmol), and triethylamine (0.11 mL) in THF
(15 mL) was added Pd(PPh3)4 (11 mg, 0.010 mmol). The resulting
mixture was stirred at room temperature for 3 days under an Ar
atmosphere. During the reaction period were added 5b (309 mg, 0.756
mmol), CuI (24 mg, 0.13 mmol), and Pd(PPh3)4 (45 mg, 0.039 mmol),
divided into several portions. The reaction mixture was diluted with
CH2Cl2, washed successively with 5% NH4Cl solution and brine, dried
Dihexyl 6-Ethynylazulene-1,3-dicarboxylate (5b). A solution of
KF (184 mg, 3.17 mmol) in water (3 mL) was added to a solution of
10 (755 mg, 1.57 mmol) in DMF (35 mL). After the mixture was stirred
at room temperature for 2 h, the reaction mixture was poured into water
and extracted with toluene. The organic layer was washed with water,
dried over MgSO4, and concentrated to afford 5b (617 mg, 96%) as
purple needles: mp 118-119 °C (hexane); MS (70 eV) m/z (relative
intensity) 408 (M+, 100), 307 (M+ - OC6H13, 26), 240 (M+ - 2C6H12,
33), 223 (M+ - OC6H13 - C6H12, 35); IR (KBr) νmax 3279 (m,
CtC-H), 2095 (m, CtC), 1684 (s, CdO) cm-1; UV-vis (CHCl3)
λmax 276 (log ꢀ 4.25), 322 (4.83), 346 (4.06), 354 (4.13), 379 (3.78),
538 (2.75) nm; 1H NMR (400 MHz, CDCl3) δ ) 9.66 (d, J ) 11.3 Hz,
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J. AM. CHEM. SOC. VOL. 125, NO. 6, 2003 1677

A R T I C L E S
Ito et al.
Figure 7. DSC thermograms of rapid-cooled sample of 3 for different
heating rates. Peaks I-IV in the figure are explained in the main text.
Figure 6. DSC thermograms of K2(v) crystals of 3 for different heating
rates. Peaks I-IV in the figure are explained in the main text.
over MgSO4, and concentrated. The residue was purified by column
chromatography on silica gel with CH2Cl2 and 5% ethyl acetate/
CH2Cl2 and GPC with CHCl3 to afford 4b (117 mg, 43%) as brown
crystals (ethyl acetate), 7b (33 mg, 18%) as purple crystals, and 8 (99
mg, 16%) as green crystals.
4b: MS (FAB) m/z 891 (M+ + 1), 890 (M+), 789 (M+ - OC6H13);
IR (KBr) νmax 2201 (m, CtC), 1688 (s, CdO) cm-1; UV-vis (CHCl3)
λmax 270 (log ꢀ 4.52), 324 (4.65), 364 (4.82), 379 (4.86), 411 (4.93),
1
428 (4.89), 538 (3.37) nm; H NMR (500 MHz, CDCl3) δ ) 9.68 (d,
J ) 11.1 Hz, 4H, H4′′,8′′), 8.78 (s, 2H, H2′′), 7.91 (d, J ) 11.1 Hz, 4H,
H5′′,7′′), 7.65 (s, 4H, H2,3,5,6), 4.38 (t, J ) 6.7 Hz, 8H, H1′′′), 1.83 (tt, J
) 7.6, 6.7 Hz, 8H, H2′′′), 1.50 (m, 8H, H3′′′), 1.41-1.35 (m, 16H, H4′′′,5′′′),
0.93 (m, 12H, H6′′′); 13C NMR (125 MHz, CDCl3) δ ) 164.9 (CO),
143.8 (C2′′), 143.4 (C3′′a,8′′a), 137.5 (C4′′,8′′), 135.8 (C6′′), 133.1 (C5′′,7′′),
132.2 (C2,3,5,6), 128.1 (C1,4), 117.2 (C1′′,3′′), 95.1 (C2′), 94.5 (C1′), 64.4
(C1′′′), 31.5 (C4′′′), 28.9 (C2′′′), 25.8 (C3′′′), 22.6 (C5′′′), 14.0 (C6′′′). Anal.
Calcd for C58H66O8: C, 78.17; H, 7.46. Found: C, 78.15; H, 7.55.
7b: mp 123-125 °C; MS (70 eV) m/z (relative intensity) 610 (M+,
Figure 8. Schematic Gibbs free energy versus temperature (G-T) diagram
of 3.
6), 275 (100); IR (KBr) νmax 2201 (m, CtC), 1698 (s, CdO) cm-1
;
1692 (s, CdO) cm-1; UV-vis (CHCl3) λmax 270 (log ꢀ 4.46), 362
1
UV-vis (CHCl3) λmax 357 (log ꢀ 4.71), 374 (4.67), 398 (4.59), 539
(4.85), 379 (4.86), 400 (4.79), 433 (4.85), 557 (3.28) nm; H NMR
(2.94) nm; 1H NMR (500 MHz, CDCl3) δ ) 9.65 (d, J ) 11.1 Hz, 2H,
(400 MHz, CDCl3) δ ) 9.66 (d, J ) 10.2 Hz, 4H, H4′,8′), 8.80 (s, 2H,
H2′), 7.88 (d, J ) 10.2 Hz, 4H, H5′,7′), 4.38 (t, J ) 6.7 Hz, 8H, H1′′),
1.83 (tt, J ) 7.6, 6.7 Hz, 8H, H2′′), 1.50 (m, 8H, H3′′), 1.42-1.34 (m,
16H, H4′′,5′′), 0.93 (m, 12H, H6′′); 13C NMR (100 MHz, CDCl3) δ )
164.7 (CO), 144.6 (C2′), 143.7 (C3′a,8′a), 137.4 (C4′,8′), 133.7 (C6′), 133.4
(C5′,7′), 117.7 (C1′,3′), 87.5 (C1,4), 78.4 (C2,3), 64.5 (C1′′′), 31.5 (C4′′′),
28.8 (C2′′′), 25.8 (C3′′′), 22.6 (C5′′′), 14.0 (C6′′′). Anal. Calcd for
C52H62O8: C, 76.63; H, 7.67. Found: C, 76.21; H, 7.59.
1,4-Bis[1,3-bis(ethoxycarbonyl)-6-azulenylethynyl]benzene (4a).
The same procedure as was used for the preparation of 4b was adopted.
The reaction of 5a (90 mg, 0.30 mmol) with 6 (50 mg, 0.15 mmol) in
triethylamine (10 mL) in the presence of Pd(PPh3)4 (17 mg, 0.015
mmol), PPh3 (7 mg, 0.03 mmol), and CuI (6 mg, 0.03 mmol) at room
H4′,8′), 8.77 (s, 1H, H2′), 7.87 (d, J ) 11.1 Hz, 2H, H5′,7′), 7.75 (d, J )
8.5 Hz, 2H, H3′′,5′′), 7.31 (d, J ) 8.5 Hz, 2H, H2′′,6′′), 4.37 (t, J ) 6.7
Hz, 4H, H1′′′), 1.83 (tt, J ) 7.6, 6.7 Hz, 4H, H2′′′), 1.50 (m, 4H, H3′′′),
1.41-1.34 (m, 8H, H4′′′,5′′′), 0.92 (m, 6H, H6′′′); 13C NMR (125 MHz,
CDCl3) δ ) 164.9 (CO), 143.7 (C2′), 143.3 (C3′a,8′a), 137.8 (C3′′,5′′), 137.5
(C4′,8′), 135.9 (C6′), 133.4 (C2′′,6′′), 133.0 (C5′,7′), 121.5 (C1′′), 117.1 (C1′,3′),
95.9 (C4′′), 94.2 (C2), 93.9 (C1), 64.4 (C1′′′), 31.5 (C4′′′), 28.8 (C2′′′),
25.8 (C3′′′), 22.6 (C5′′′), 14.0 (C6′′′). HRMS calcd for C32H35IO4 610.1580,
found 610.1578. Anal. Calcd for C32H35IO4: C, 62.95; H, 5.78.
Found: C, 62.90; H, 5.78.
8: mp 200-202 °C (ethyl acetate/hexane); MS (FAB) m/z 814 (M+
+ 1), 814 (M+), 713 (M+ - OC6H13); IR (KBr) νmax 2139 (w, CtC),
9
1678 J. AM. CHEM. SOC. VOL. 125, NO. 6, 2003

Poly(6-azulenylethynyl)benzene Derivatives
A R T I C L E S
Figure 11. X-ray diffraction powder patterns of 4b (Colho mesophase
obtained by rapid cooling at room temperature).
Figure 12. Schematic Gibbs free energy versus temperature (G-T) diagram
of 4b.
Figure 9. Photomicrographs of the double melting behavior of K1 phase
of 4b: (a) at 150 °C, (b) at 158.2 °C, (c) at 158.2 °C after 30 min, (d) at
158.2 °C after 120 min, (e) at 158.2 °C after 480 min, (f) at 161.2 °C, and
(g) at 162.0 °C.
) 7.1 Hz, 8H, 1′′,3′′-COOEt), 1.47 (t, J ) 7.1 Hz, 12H, 1′′,3′′-COOEt);
13C NMR (125 MHz, CDCl3) δ ) 164.9 (s, 1′′,3′′-COOEt), 143.9 (C2′′),
143.5 (C3′′a,8′′a), 137.6 (C4′′,8′′), 135.9 (C6′′), 133.2 (C5′′,7′′), 132.3 (C2,3,5,6),
123.1 (C1,4), 117.2 (C1′,3′), 95.1 (C2′), 94.5 (C1′), 60.2 (t, 1′′,3′′-COOEt),
14.6 (q, 1′′,3′′-COOEt). HRMS calcd for C42H34O8 666.2254, found
666.2236. Anal. Calcd for C42H34O8‚H2O: C, 73.67; H, 5.30. Found:
C, 73.19; H, 5.18.
7a: mp 155-160 °C; MS (70 eV) m/z (relative intensity) 498 (M+,
100), 453 (M+ - OEt, 23); IR (KBr) νmax 2201 (m, CtC), 1684 (s,
CdO) cm-1; UV-vis (CHCl3) λmax 328 (log ꢀ 4.51), 357 (4.66), 374
1
(4.62), 398 (4.54), 537 (2.93) nm; H NMR (500 MHz, CDCl3) δ )
9.67 (d, J ) 11.2 Hz, 2H, H4′,8′), 8.80 (s, 1H, H2′), 7.89 (d, J ) 11.2
Hz, 2H, H5′,7′), 7.76 (d, J ) 8.2 Hz, 2H, H3′′,5′′), 7.33 (d, J ) 8.2 Hz,
2H, H2′′,6′′), 4.44 (q, J ) 7.1 Hz, 4H, 1′,3′-COOEt), 1.46 (t, J ) 7.1
Hz, 6H, 1′,3′-COOEt); 13C NMR (125 MHz, CDCl3) δ ) 164.9 (s,
1′,3′-COOEt), 143.8 (C2′), 143.4 (C3′a,8′a), 137.8 (C3′′,5′′), 137.5 (C4′,8′),
136.0 (C6′), 133.4 (C2′′,6′′), 133.1 (C5′,7′), 121.5 (C1′′), 117.1 (C1′,3′), 95.9
(C2 or C4′′), 94.2 (C2 or C4′′), 93.9 (C1), 60.2 (t, 1′,3′-COOEt), 14.5 (q,
1′,3′-COOEt). HRMS calcd for C24H19IO4 498.0328, found 498.0339.
Anal. Calcd for C24H19IO4‚0.5H2O: C, 56.82; H, 3.97. Found: C, 56.58;
H, 3.91.
Hexakis[1,3-bis(hexyloxycarbonyl)-6-azulenylethynyl]benzene (1).
To a degassed solution of 15 (101 mg, 0.154 mmol) in water (0.2 mL),
THF (11 mL), and methanol (15 mL) was added K2CO3 (16 mg, 0.12
mmol). The resulting mixture was stirred at room temperature for 100
min. After an addition of water and diethyl ether to the reaction mixture,
the organic layer was separated, washed with water, dried over MgSO4,
and concentrated to 5 mL. The residue was diluted with THF (5 mL),
and triethylamine (1 mL), 9b (500 mg, 1.08 mmol), and CuI (3 mg,
Figure 10. Texture of the discotic mesophase (Colho) of 4b obtained by
rapid cooling at room temperature.
temperature for 1 h followed by chromatographic purification on silica
gel with 5% ethyl acetate/CH2Cl2 and GPC with CHCl3 afforded 4a
(25 mg, 25%) as brown crystals and 7a (9 mg, 12%) as purple crystals.
4a: mp 265.5-270 °C (ethyl acetate); MS (70 eV) m/z (relative
intensity) 666 (M+, 100); IR (KBr) νmax 2201 (m, CtC), 1694 (s,
CdO) cm-1; UV-vis (CHCl3) λmax 270 (log ꢀ 4.49), 325 (4.59), 364
1
(4.74), 378 (4.78), 410 (4.83), 429 (4.80), 535 (3.27) nm; H NMR
(500 MHz, CDCl3) δ ) 9.70 (d, J ) 11.1 Hz, 4H, H4′′,8′′), 8.81 (s, 2H,
H2′′), 7.93 (d, J ) 11.1 Hz, 4H, H5′′,7′′), 7.67 (s, 4H, H2,3,5,6), 4.45 (q, J
9
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A R T I C L E S
Ito et al.
0.02 mmol) were added to the solution. After an addition of Pd(PPh3)4
(9 mg, 0.008 mmol) to the degassed mixture, the mixture was stirred
at room temperature for 21 h and then refluxed for 18 h. The reaction
mixture was diluted with CHCl3, washed successively with 10%
NH4Cl solution and brine, dried over MgSO4, and concentrated. The
residue was purified by column chromatography on silica gel with
CHCl3 and 10% ethyl acetate/CHCl3 to afford 1 (214 mg, 55%) as
brown crystals (chloroform): MS (ESI-TOF) m/z 2540.24 (M+ + Na)
[calcd 2539.33]; IR (KBr) νmax 1694 (s, CdO) cm-1; UV-vis (CHCl3)
(C1,2,4,5), 117.6 (C1′′,3′′), 99.8 (C2′), 91.5 (C1′), 64.5 (C1′′′), 31.5 (C4′′′),
28.9 (C2′′′), 25.8 (C3′′′), 22.6 (C5′′′), 14.0 (C6′′′). Anal. Calcd for
C110H126O16: C, 77.53; H, 7.45. Found: C, 77.31; H, 7.51.
12: mp 200-202 °C (toluene); MS (ESI-TOF) m/z 1445.58 (M+
+
Na) [calcd 1445.58]; IR (KBr) νmax 2201 (w, CtC), 1694 (s, CdO)
cm-1; UV-vis (CHCl3) λmax 270 (log ꢀ 4.71), 326 (4.92), 361 (5.04),
1
378 (5.06), 546 (3.45) nm; H NMR (500 MHz, CDCl3) δ ) 9.70 (d,
J ) 11.1 Hz, 2H, H4′′,8′′), 9.67 (d, J ) 11.1 Hz, 4H, H4′′,8′′), 8.79 (s,
3H, H2′′), 8.23 (s, 1H, H6), 7.96 (d, J ) 11.1 Hz, 2H, H5′′,7′′), 7.94 (d,
J ) 11.1 Hz, 2H, H5′′,7′′), 7.92 (d, J ) 11.1 Hz, 2H, H5′′,7′′), 7.86 (s,
1H, H3), 4.38 (t, J ) 6.8 Hz, 4H, H1′′′), 4.36 (t, J ) 6.8 Hz, 8H, H1′′′),
1.86-1.77 (m, 12H, H2′′′), 1.52-1.45 (m, 12H, H3′′′), 1.39-1.34 (m,
12H, H4′′′,5′′′), 0.95-0.89 (m, 18H, H6′′′); 13C NMR (125 MHz, CDCl3)
δ ) 164.8 (CO), 164.7 (CO), 144.4 (C2′′), 144.3 (C2′′), 143.5 (C3′′a,8′′a),
142.5 (C6), 137.6 (C4′′,8′′), 135.8 (C3), 134.9 (C6′′), 134.8 (C6′′), 134.7
(C6′′), 132.9 (C5′′,7′′), 132.8 (C5′′,7′′), 129.8 (C2 or C4), 126.3 (C5), 125.0
(C2 or C4), 117.6 (C1′′,3′′), 117.4 (C1′′,3′′), 101.8 (C1), 100.0 (C2′), 98.6
(C2′), 95.4 (C1′), 91.2 (C1′), 90.9 (C1′), 64.5 (C1′′′), 31.5 (C4′′′), 28.9 (C2′′′),
28.8 (C2′′′), 25.8 (C3′′′), 22.6 (C5′′′), 14.0 (C6′′′). Anal. Calcd for C84H95-
IO12: C, 70.87; H, 6.73. Found: C, 70.70; H, 6.93.
λ
max 331 (log ꢀ 5.28), 381 (5.17), 419 (5.28), 558 (3.71) nm; 1H NMR
(500 MHz, CDCl3) δ ) 9.58 (d, J ) 10.9 Hz, 12H, H4′′,8′′), 8.67 (s,
6H, H2′′), 7.97 (d, J ) 10.9 Hz, 12H, H5′′,7′′), 4.33 (t, J ) 6.9 Hz, 24H,
H1′′′), 1.77 (tt, J ) 7.6, 6.9 Hz, 24H, H2′′′), 1.45 (m, 24H, H3′′′), 1.36-
1.30 (m, 48H, H4′′′,5′′′), 0.90 (m, 36H, H6′′′); 13C NMR (125 MHz, CDCl3)
δ ) 164.3 (CO), 144.6 (C2′′), 143.4 (C3′′a,8′′a), 137.6 (C4′′,8′′), 133.9 (C6′′),
132.5 (C5′′,7′′), 128.5 (C1,2,3,4,5,6), 118.1 (C1′′,3′′), 104.5 (C2′), 90.6 (C1′),
64.4 (C1′′′), 31.6 (C4′′′), 28.9 (C2′′′), 25.9 (C3′′′), 22.6 (C5′′′), 13.9 (C6′′′).
Anal. Calcd for C162H186O24: C, 77.30; H, 7.45. Found: C, 77.19; H,
7.81.
1,2,4,5-Tetrakis[1,3-bis(hexyloxycarbonyl)-6-azulenylethynyl]ben-
zene (2): Method 1. The same procedure as was used for the
preparation of 1 was adopted. Compound 16 was prepared by the
desilylation of 17 (100 mg, 0.216 mmol) by K2CO3 (21 mg, 0.15 mmol)
in water (0.1 mL), THF (5 mL), and methanol (15 mL). The reaction
of 9b (499 mg, 1.08 mmol) with 16 in triethylamine (1 mL) and THF
(10 mL) in the presence of Pd(PPh3)4 (12 mg, 0.010 mmol) and CuI (4
mg, 0.02 mmol) at room temperature for 15 h, followed by chromato-
graphic purification on silica gel with CHCl3 and 10% ethyl acetate/
CHCl3, afforded 2 (244 mg, 66%) as brown crystals (chloroform).
Method 2. The same procedure as was used for the preparation of
4b was adopted. Compound 5b (178 mg, 0.436 mmol) was reacted
with 11 (50 mg, 0.086 mmol) in triethylamine (0.06 mL) and THF (5
mL) in the presence of Pd(PPh3)4 (4 mg, 0.003 mmol) and CuI (0.4
mg, 0.002 mmol), at room temperature for 22 h. During the reaction
period were added 5b (180 mg, 0.441 mmol) and Pd(PPh3)4 (3 mg,
0.003 mmol). Chromatographic purification of the reaction mixture on
silica gel with CH2Cl2 and 10% ethyl acetate/CH2Cl2 and GPC with
CHCl3 afforded 2 (37 mg, 25%), 12 (25 mg, 20%) as brown crystals,
and 8 (17 mg, 5%).
1,3,5-Tris[1,3-bis(hexyloxycarbonyl)-6-azulenylethynyl]ben-
zene (3). The same procedure as was used for the preparation of 1 was
adopted. Compound 18 was prepared by the desilylation of 19 (100
mg, 0.273 mmol) by K2CO3 (26 mg, 0.19 mmol) in water (0.25 mL),
THF (40 mL), and methanol (13 mL). The reaction of 9b (503 mg,
1.09 mmol) with 18 in triethylamine (1 mL) and THF (10 mL) in the
presence of Pd(PPh3)4 (15 mg, 0.013 mmol) and CuI (6 mg, 0.03 mmol)
at room temperature for 15 h, followed by chromatographic purifica-
tion on silica gel with CHCl3 and 5% ethyl acetate/CHCl3, afforded 3
(340 mg, 96%) as purple crystals (ethyl acetate): MS (FAB) m/z 1298
(M+ + 1), 1297 (M+), 1196 (M+ - OC6H13); IR (KBr) νmax 2203 (m,
CtC), 1698 (s, CdO) cm-1; UV-vis (CHCl3) λmax 270 (log ꢀ 4.65),
357 (5.18), 374 (5.15), 396 (5.13), 542 (3.40) nm; 1H NMR (500 MHz,
CDCl3) δ ) 9.60 (d, J ) 11.1 Hz, 6H, H4′′,8′′), 8.71 (s, 3H, H2′′), 7.84
(d, J ) 11.1 Hz, 6H, H5′′,7′′), 7.82 (s, 3H, H2,4,6), 4.37 (t, J ) 6.8 Hz,
12H, H1′′′), 1.84 (tt, J ) 7.9, 6.8 Hz, 12H, H2′′′), 1.51 (m, 12H, H3′′′),
1.42-1.36 (m, 24H, H4′′′,5′′′), 0.94 (m, 18H, H6′′′); 13C NMR (125 MHz,
CDCl3) δ ) 164.7 (CO), 143.9 (C2′′), 143.3 (C3′′a,8′′a), 137.4 (C4′′,8′′),
135.6 (C2,4,6), 135.1 (C6′′), 132.9 (C5′′,7′′), 123.5 (C1,3,5), 117.2 (C1′′,3′′),
94.4 (C2′), 92.3 (C1′), 64.4 (C1′′′), 31.5 (C4′′′), 28.9 (C2′′′), 25.8 (C3′′′),
22.6 (C5′′′), 14.0 (C6′′′). Anal. Calcd for C84H96O12: C, 77.75; H, 7.46.
Found: C, 77.71; H, 7.54.
2: MS (ESI-TOF) m/z 1726.95 (M+ + Na) [calcd 1726.90]; IR (KBr)
ν
max 2203 (w, CtC), 1692 (s, CdO) cm-1; UV-vis (CHCl3) λmax 271
(log ꢀ 4.84), 329 (5.01), 365 (5.15), 379 (5.18), 399 (5.17), 548 (3.60)
nm; 1H NMR (500 MHz, CDCl3) δ ) 9.65 (d, J ) 10.9 Hz, 8H, H4′′,8′′),
8.74 (s, 4H, H2′′), 8.00 (s, 2H, H3,6), 7.93 (d, J ) 10.9 Hz, 8H, H5′′,7′′),
4.37 (t, J ) 6.8 Hz, 16H, H1′′′), 1.81 (tt, J ) 7.9, 6.8 Hz, 16H, H2′′′),
1.48 (m, 16H, H3′′′), 1.38-1.35 (m, 32H, H4′′′,5′′′), 0.91 (m, 24H, H6′′′);
13C NMR (125 MHz, CDCl3) δ ) 164.7 (CO), 144.3 (C2′′), 143.4
(C3′′a,8′′a), 137.5 (C4′′,8′′), 136.5 (C3,6), 134.7 (C6′′), 132.8 (C5′′,7′′), 125.7
Acknowledgment. We are grateful to Professor Nagao
Kobayashi and Dr. Kazuyuki Ishii of Tohoku University for
the measurement of ESI-TOF MS.
JA0209262
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1680 J. AM. CHEM. SOC. VOL. 125, NO. 6, 2003