Synthesis and optical properties of pyridino end-capped oligothiophenes

Article abstract of DOI:10.1246/bcsj.20110168

Oligothiophenes end-capped with fused pyridino units were synthesized by means of the Stille coupling and their optical properties were studied. These compounds show absorption maxima and edges at 324374 nm and 3.102.76 eV, respectively, depending on the oligothiophene chain lengths. DFT calculations indicate that both the HOMO and LUMO levels are lowered by the introduction of the pyridino units.

Full text of DOI:10.1246/bcsj.20110168

© 2011 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 84, No. 11, 1243-1247 (2011) 1243
Synthesis and Optical Properties of Pyridino
End-Capped Oligothiophenes
Yong-Mook Hwang,1 Joji Ohshita,*1 Tomonobu Mizumo,1 Hiroto Yoshida,1
Yoshihito Kunugi,2 and Takashi Sugioka3
1Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University,
Higashi-Hiroshima, Hiroshima 739-8527
2Department of Applied Chemistry, Faculty of Engineering, Tokai University,
4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292
3Synthesis Research Laboratory, Kurashiki Research Center, Kuraray Co., Ltd.,
2045-1 Sakazu, Kurashiki, Okayama 710-0801
Received June 1, 2011; E-mail: jo@hiroshima-u.ac.jp
Oligothiophenes end-capped with fused pyridino units were synthesized by means of the Stille coupling and their
optical properties were studied. These compounds show absorption maxima and edges at 324-374 nm and 3.10-2.76 eV,
respectively, depending on the oligothiophene chain lengths. DFT calculations indicate that both the HOMO and LUMO
levels are lowered by the introduction of the pyridino units.
Oligo- and polythiophenes are of current interest, as
promising organic materials that can be used for organic
devices, such as organic thin film transistors and organic
photovoltaic cells.1 High planarity of oligo- and polythio-
phenes leads to enhanced conjugation, and the rather strong
intermolecular interaction originating from the high polar-
izability of the sulfur electrons facilitates the intermolecular
hopping mobility. However, there is still a need to improve
the properties of oligo- and polythiophenes, including carrier
mobility, film forming properties, thermal and chemical
stability, etc.
The introduction of end-capping aromatic substituents has
been often studied to tune the electronic states of oligo- and
polythiophenes and also to avoid oxidation and polymerization,
upon fabrication of the devices. For example, phenyl,2 fluore-
nyl,3 styryl,4 and naphthyl5 end-capped oligothiophenes were
prepared as high-performance semiconductors with good carrier
mobility and high device stability. Fused end-capping units
have been also examined and benzo and naphtho end-capped
oligothiophenes were reported to show moderate to high
mobility in their vapor-deposited films.6 In this paper, we
report the first synthesis of pyridino end-capped oligothio-
phenes and their optical properties. In these compounds, polar
pyridino units would enhance the intermolecular interaction in
the solid states, and their electron-withdrawing properties would
lead to the effective intramolecular interaction with the electron-
donating oligothiophene units, enhancing the conjugation.
pyridine, which was then treated with sodium alkoxide to give
alkoxybromothienopyridine 1. Oxidative coupling of methoxy-
thienopyridinyllithium prepared from 1a with CuCl2 gave
bi(thienopyridine) 2a in 41% yield, while the Stille coupling
reactions of 1 with bis(tributylstannyl)thiophene and -bithio-
phene catalyzed by [Pd(PPh3)4] afforded pyridino end-capped
oligothiophenes 3 and 4 in 35-45% yield (Scheme 1). Similar
coupling with bis(tributylstannyl)benzene gave phenylene-
linked thienopyridine 3a¤ in 75% yield.
Some properties of the present oligothiophenes are summa-
rized in Table 1. They are orange solids that melt without
decomposition and are soluble in common organic solvents,
such as toluene, THF, and chloroform. The absorption and
emission maxima of the compounds are little affected by the
substituents (R = Me, n-Bu, or n-Hex) and move to longer
wavelength as elongating the oligothiophene chain from 2 to 4,
as presented in Figure 1. Compounds 2a and 3a¤ are not
emissive in chloroform. Phenylene-bridged compound 3a¤
exhibits a shorter absorption -max by 10 nm than 3a. The UV
spectrum of 4a was measured also as a vapor-deposited film,
which reveals the longer absorption maximum by 16 nm than
that in chloroform, clearly indicating the close packing of the
molecules in the solid state leading to the highly planar
structure and/or the strong intermolecular ³-³ interaction.
Optical properties of benzo6 and hexyl end-capped oligothio-
phenes7 shown in Scheme 2 were reported previously. Di-
hexylquaterthiophene 4H shows the absorption band at
-
max = 402 nm red-shifted from that of 4a-4c (374 nm), while
Results and Discussion
the absorption edges (Eg) are only slightly red shifted on
going from 4a-4c (450 nm, 2.76 eV) to 4H (460 nm,
2.70 eV).7,8 The absorption maximum of 4B is reported only
for its film (-max = 344 nm),6 which is at higher energy than
that of 4a (390 nm).
Pyridino end-capped oligothiophenes were prepared as
shown in Scheme 1. Ring constructing reaction of benzene-
sulfonyl cyanide with (3-methylthien-2-ylmethylene)aniline,
followed by bromination gave (benzenesulfonyl)bromothieno-
Published on the web November 3, 2011; doi:10.1246/bcsj.20110168

1244 Bull. Chem. Soc. Jpn. Vol. 84, No. 11 (2011)
Pyridino End-Capped Oligothiophenes
PhSO2
PhSO2
NBS
O
N
+
Ph S C N
N
S
Br
O
S
N
S
Ph
RONa
RO
MeO
MeO
BuLi
S
CuCl2
N
N
N
N
Br
Li
S
S
S
OMe
2a
1
RO
OR
a R = Me
b
R = n-Bu
c R = n-Hex
S
N
N
S
S
3
RO
Bu3Sn Ar SnBu3
[Pd(PPh3)4]/DMF
S
S
N
N
S
S
OR
4
MeO
S
N
N
S
OMe
3a'
Scheme 1. Preparation of pyridino end-capped oligothiophenes.
Table 1. Synthesis and Properties of Pyridino End-Capped
Oligothiophenes
Similar optical tendency is observed also for terthiophene
derivatives (3a-3c: -max = 344-346 nm, Eg = 2.95 eV; 3H:
-
max = 374 nm, Eg = 2.91 eV). For bithiophenes, however,
UV-vis absorptiona)
Emissiona)
em/nm Φfb)
Yield Mp
/% /°C
both -max and Eg indicated rather enhanced conjugation for
2a (-max = 324 nm, Eg = 3.10 eV) over 2H (-max = 316 nm,
Eg = 3.43 eV). For bithiophenes bearing only one interring
bond, the effects of the conformer population are not very
important and essentially pyridine end-capped oligothiophenes
should possess better conjugation than the corresponding hexyl
end-capped ones. The intramolecular charge-transfer (CT)
interaction in these pyridino end-capped oligothiophenes
would be considered. Indeed, the UV absorption band of
4a moved to 382 nm in DMSO. However the shift is small
(6 nm) and such CT interaction is not remarkably operative if
it is involved.
Compound
-max/nm Eg/eV
-
2a
3a
3b
3c
3a¤
4a
4b
4c
41
35
40
41
75
35
42
45
258
196
170
165
205
246
206
198
324
344
345
346
334
374
374
374
3.10
3.00
3.00
3.00
3.22
2.76
2.76
2.76
ndc)
428
429
430
ndc)
472
473
474
ndc)
0.12
0.12
0.12
ndc)
0.22
0.22
0.22
a) In chloroform, with [substrate] = 2.0 © 10¹5 M. b) Absolute
quantum efficiency, determined in an integration sphere.
c) No emission detected.
To know more about the electronic states of these oligo-
thiophenes, we carried out DFT calculations on simplified
models and 4a (Scheme 3) at the B3LYP/6-31G(d,p) level and
the results are depicted in Figure 2.9 The optimized geometries
of these compounds exhibit high planarity of the systems,
retaining all the ring atoms in one plane. Smaller HOMO-
LUMO energy gaps are obtained for pyridino end-capped
2m and 4m than for 2Hm and 4Hm, respectively. Interest-
ingly, pyridino annulation causes slight changes in bond
angles and lengths in the annulated thiophene rings to shorten
the intramolecular non bonding H-S contacts as shown in
Scheme 3, which may increase the population of twisted
conformers for pyridino end-capped quaterthiophenes, being
Since the absorption maxima reflect the average of the
electronic states of conformers, it is likely that the larger
difference of the absorption maxima between 4a-4c and 4H
than that of the edges is due to the higher degree of the
population of twisted conformers with respect to the thio-
phene-thiophene single bond rotation for 4a-4c. This is
supported also by the larger Stokes shifts for 4a-4c than 4H.
Quaterthiophene 4H was reported to show two emission
maxima at 463 and 492 nm,7 thus -em ¹ -max = 61, 90 nm,
both of which are smaller than those of 4a-4c (-em ¹ -max
98-100 nm).
=

Y.-M. Hwang et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 11 (2011) 1245
H
2.945
1.2
2a 3a'
3a−3c
4a−4c
2a
3a'
3a
3b
3c
4a
4b
4c
S
S
S
H
H
N
H
H
1.0
0.8
0.6
0.4
0.2
S
S
S
H
2Hm
2.941
H
4Hm
2.923
S
S
S
N
N
N
S
S
S
2m
H
4m
2.902
2.918
MeO
H
0.0
325
S
S
N
N
S
350
375
400
425
450
475
S
OMe
H
2.898
Wavelength/nm
4a
(a)
Scheme 3. Model compounds and 4a for DFT calculations.
Numbers indicate the H-S contacts (¡) in the optimized
geometries, derived from the calculations.
3a−3c
4a−4c
3a
3b
3c
4a
4b
4c
2000
1000
0
400
450
500
550
600
650
700
Wavelength/nm
(b)
Figure 1. UV-vis absorption (a) and emission (b) spectra of
pyridino end-capped oligothiophenes in chloroform.
Figure 2. HOMO and LUMO energy levels of model
compounds, derived from DFT calculations at the
B3LYP/6-31G(d,p) level.
S
S
S
n-Hex
n-Hex
n-Hex
n-Hex
S
S
S
2H
4H
S
S
S
n-Hex
S
n-Hex
S
S
S
3H
4B
Scheme 2. Hexyl and benzo end-capped oligothiophenes (Refs. 6 and 7).
responsible for their blue-shifted absorptions relative to
those of dihexyl analogs. It is also noteworthy that the
introduction of pyridino groups at the ends lowers both the
HOMO and LUMO levels significantly, and reduces the
HOMO-LUMO energy gaps to an extent. One may consider
the substitution effects, but the introduction of methoxy
groups on 4m elevates HOMO and LUMO energy levels
only slightly, and exerts no significant influence on the energy
gap.
Conclusion
In conclusion, we prepared pyridino end-capped oligothio-
phenes and demonstrated efficient conjugation in the system
based on optical studies. The low-lying HOMOs and LUMOs
of this type of compounds seem to provide opportunities to
utilize them as organic device materials such as electron-
transporting materials for organic light-emitting diodes, and
host materials for photovoltaic cells with large Voc (open circuit

1246 Bull. Chem. Soc. Jpn. Vol. 84, No. 11 (2011)
Pyridino End-Capped Oligothiophenes
voltage) and bipolar thin film transistor materials with stability
toward oxidation. Studies to explore the applications of the
present pyridino end-capped oligothiophenes are in progress.
(270 MHz, CDCl3): ¤ 0.99 (t, J = 7.2 Hz, 3H), 1.51-1.56
(m, 2H), 1.78-1.84 (m, 2H), 4.34 (t, J = 6.5 Hz, 2H), 7.09
(s, 1H), 7.62 (s, 1H), 8.67 (s, 1H). MS: m/z 287 [M+]. Data for
1
1c: 71% yield. Mp 42 °C. H NMR (400 MHz, CDCl3): ¤ 0.91
Experimental
(t, J = 6.8 Hz, 3H), 1.33-1.37 (m, 4H), 1.45-1.53 (m, 2H),
1.78-1.86 (m, 2H), 4.32 (t, J = 6.5 Hz, 2H), 7.09 (s, 1H), 7.62
(s, 1H), 8.67 (s, 1H); 13C NMR (100 MHz, CDCl3): ¤ 14.09,
22.65, 25.77, 29.18, 31.63, 67.06, 101.68, 106.24, 128.31,
130.21, 141.85, 146.87, 162.21. MS: m/z 315 [M+].
General Procedure. All reactions were carried out in dry
nitrogen. Tetrahydrofuran (THF) and dimethylformamide
(DMF) were distilled from sodium/benzophenone and calcium
hydride, respectively, and were stored over activated molecular
sieves until use. NMR spectra were recorded on JEOL Model
LA-400 and EX-270 spectrometers. Mass spectra were
measured on a SHIMADZU QP-5050A spectrometer, while
HR-ESI-mass spectra were obtained on a Thermo Fisher
Scientific LTQ Orbitrap XL spectrometer at the Natural Science
Center for Basic Research and Development (N-BARD),
Hiroshima University. UV and emission spectra were measured
on Shimadzu UV-3150 and RF-5000 spectrophotometers,
respectively. Emission quantum yields were determined in an
integration sphere attached to a Hamamatsu Photonics C7473
Multi-Channel Analyzer. The usual workup mentioned bellow
includes hydrolysis of the reaction mixture with water,
extraction of organic products with chloroform, washing the
extract with water, drying the washed extract over anhydrous
magnesium sulfate, and evaporation of the solvent, in that
order.
5-(Benzenesulfonyl)thieno[2,3-c]pyridine. A mixture of
3.77 g (22.6 mmol) of benzenesulfonyl cyanide and 3.08 g
(22.6 mmol) of isobutyl chloroformate in 100 mL of xylene
was heated to reflux. To this was added dropwise 3.03 g (15.0
mmol) of (3-methylthien-2-ylmethylene)aniline over a period
of 30 min. The mixture was refluxed for an additional 1 h. After
usual workup, the residue was chromatographed on silica gel
to give 10.1 g (67% yield) of the title compound. 1H NMR
(CDCl3, 270 MHz): ¤ 7.48-7.62 (m, 4H), 7.90 (d, J = 4.86 Hz,
1H), 8.08-8.13 (m, 2H), 8.66 (d, J = 1.1 Hz, 1H), 9.16
(d, J = 1.1 Hz, 1H). MS: m/z 275 [M+].
2,2¤-Bi(5-methoxythieno[2,3-c]pyridine) (2a). To a THF
(15 mL) solution of (5-methoxythieno[2,3-c]pyridin-2-yl)lithi-
um prepared by treating 0.400 g (1.64 mmol) of 1a with
1.28 mL (2.13 mmol) of 1.66 M n-BuLi/hexane at ¹78 °C was
added slowly 0.264 g (1.97 mmol) of CuCl2 at the same
temperature. After being stirred at ¹78 °C for 1 h, the mixture
was hydrolyzed with dil. HCl. The organic layer was separated
and the aqueous layer was extracted with chloroform. The
organic layer and the extracts were combined and washed with
dil. HCl to remove residual CuCl2 then with water. After drying
over anhydrous magnesium sulfate, the solvent was evaporated
and the residue was subjected to column chromatography on
silica gel (5% EtOAc in hexane as eluent) to yield 2a as an
orange solid (41% yield). Mp 258 °C; 1H NMR (270 MHz,
CDCl3): ¤ 4.00 (s, 6H), 7.02 (s, 2H), 7.76 (s, 2H), 8.78 (s, 2H).
13C NMR (100 MHz, CDCl3): ¤ 54.1, 102.2, 120.9, 129.5,
141.1, 143.1, 148.7, 162.0. MS: m/z 328 [M+]. HR-ESI-MS:
m/z 329.0413 [M + H+] (calcd for C16H13O2N2S2, 329.0413).
Bis(5-alkoxythieno[2,3-c]pyridin-2-yl)thiophene
3a-3c
and -bithiophene 4a-4c. A mixture of 1a (200 mg, 0.819
mmol), 2,5-bis(tributylstannyl)thiophene (271 mg, 0.41 mmol),
and [Pd(PPh3)4] (48 mg, 0.039 mmol) in DMF (15 mL) was
stirred at 50 °C for 2 days. After usual workup, the residue was
subjected to column chromatography on silica gel (20% ether
in hexane as eluent) to yield 3a as an orange solid (35% yield).
1
Mp 196 °C. H NMR (270 MHz, CDCl3): ¤ 4.04 (s, 6H), 7.38
(s, 2H), 7.47 (s, 2H), 7.78 (s, 2H), 8.76 (s, 2H); 13C NMR
(100 MHz, CDCl3): ¤ 54.24, 101.91, 125.75, 128.92, 130.49,
130.70, 135.79, 141.88, 146.20. MS: m/z 410 [M+]. Anal.
Calcd for C20H14N2O2S3: C, 58.51; H, 3.44; N, 6.82%. Found:
C, 58.59; H, 3.09; N, 6.65%. Compounds 3b, 3c, and 4a-4c
were obtained in a fashion similar to that above. Data for 4a,
purified by column chromatography on silica gel (10% EtOAc
5-(Benzenesulfonyl)-2-bromothieno[2,3-c]pyridine.
A
mixture of 2.37 g (8.60 mmol) of 5-(benzenesulfonyl)thieno-
[2,3-c]pyridine and 4.60 g (25.8 mmol) of NBS in 30 mL of
acetonitrile was stirred at 70 °C for 6 h. To this were added
100 mL of acetic acid and 100 mL of water. After usual
workup, the residue was recrystallized from toluene/ethyl
acetate to give 2.49 g (81% yield) of the title compound. Mp
205 °C. 1H NMR (270 MHz, CDCl3): ¤ 7.50-7.63 (m, 3H),
7.86 (s, 1H), 8.10-8.14 (m, 2H), 8.65 (d, J = 0.8 Hz, 1H), 9.13
(d, J = 0.8 Hz, 1H). MS: m/z 353 [M+ for 79Br].
1
in hexane as eluent): 35% yield. Mp 246 °C. H NMR (400
MHz, CDCl3): ¤ 4.04 (s, 6H), 7.26 (d, J = 3.9 Hz, 2H), 7.28
(d, J = 3.9 Hz, 2H), 7.47 (s, 2H), 7.74 (s, 2H), 8.74 (s, 2H).
13C NMR (100 MHz, CDCl3): ¤ 54.2, 101.9, 124.3, 125.9,
128.9, 130.2, 130.7, 135.2, 136.5, 141.8, 146.1, 162.2. MS:
m/z 492 [M+]. Anal. Calcd for C24H16N2O2S4: C, 58.51; H,
3.27; N, 5.69%. Found: C, 58.24; H, 3.09; N, 5.53%. Data for
3b, purified by column chromatography on silica gel (10%
5-Alkoxy-2-bromothieno[2,3-c]pyridine 1a-1c. A solu-
tion of 2-bromo-5-(benzenesulfonyl)thieno[2,3-c]pyridine
(1.00 g, 2.82 mmol) and MeONa/MeOH prepared from sodium
metal (2.5 g) and methanol (70 mL) in 30 mL of THF was
heated to reflux overnight. After usual workup, the residue was
subjected to column chromatography on silica gel (5% EtOAc
in hexane as eluent) to yield 1a as an orange solid (74%).
1
ether in hexane as eluent): 40% yield. Mp 170 °C. H NMR
(400 MHz, CDCl3): ¤ 0.99 (t, J = 7.2 Hz, 6H), 1.47-1.55 (m,
4H), 1.77-1.85 (m, 4H), 4.35 (t, J = 6.5 Hz, 4H), 7.38 (s, 2H),
7.44 (s, 2H), 7.76 (s, 2H), 8.73 (s, 2H). 13C NMR (100 MHz,
CDCl3): ¤ 13.93, 19.31, 31.34, 66.63, 102.06, 125.79, 128.96,
130.37, 130.46, 135.80, 141.92, 146.23, 162.1. MS: m/z 494
[M+]. Anal. Calcd for C26H26N2O2S3: C, 63.13; H, 5.30; N,
5.66%. Found: C, 62.99; H, 5.13; N, 5.42%. Data for 4b,
purified by column chromatography on silica gel (10% EtOAc
1
Mp 117 °C. H NMR (270 MHz, CDCl3): ¤ 4.02 (s, 3H), 7.10
(s, 1H), 7.63 (s, 1H), 8.68 (s, 1H). MS: m/z 245 [M+].
Compounds 1b and 1c were obtained as orange solids in a
fashion similar to that above, using n-BuONa/n-BuOH and
n-HexONa/n-HexOH instead of MeONa/MeOH for 1b and
1
1c, respectively. Data for 1b: 75% yield. Mp 55 °C; H NMR

Y.-M. Hwang et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 11 (2011) 1247
in hexane as eluent): 42% yield. Mp 206 °C. 1H NMR
(400 MHz, CDCl3): ¤ 0.99 (t, J = 7.2 Hz, 6H), 1.50-1.56
(m, 4H), 1.78-1.84 (m, 4H), 4.60 (t, J = 6.5 Hz, 4H), 7.26
(d, J = 3.9 Hz, 2H), 7.28 (d, J = 3.9 Hz, 2H), 7.45 (s, 2H), 7.73
(s, 2H), 8.72 (s, 2H). 13C NMR (100 MHz, CDCl3): ¤ 13.92,
19.30, 31.34, 66.63, 102.09, 124.37, 125.96, 128.96, 130.18,
130.45, 135.29, 136.57, 141.89, 146.15, 162.09. MS: m/z 576
[M+]. Anal. Calcd for C30H28N2O2S4: C, 62.47; H, 4.89; N,
4.86%. Found: C, 62.30; H, 4.72; N, 4.78%. Data for 3c,
purified by column chromatography on silica gel (10% ether in
References
For recent reviews: a) A. Mishra, C.-Q. Ma, P. Bäuerle,
Chem. Rev. 2009, 109, 1141. b) I. Osaka, R. D. McCullough, Acc.
Chem. Res. 2008, 41, 1202. c) S. Günes, H. Neugebauer, N. S.
Sariciftci, Chem. Rev. 2007, 107, 1324.
1
2
a) X. M. Hong, H. E. Katz, A. J. Lovinger, B.-C. Wang, K.
Raghavachari, Chem. Mater. 2001, 13, 4686. b) M. Mushrush, A.
Facchetti, M. Lefenfeld, H. E. Katz, T. J. Marks, J. Am. Chem. Soc.
2003, 125, 9414. c) S. Mohapatra, B. T. Holmes, C. R. Newman,
C. F. Prendergast, C. D. Frisbie, M. D. Ward, Adv. Funct. Mater.
2004, 14, 605.
1
hexane as eluent): 41% yield. Mp 165 °C. H NMR (400 MHz,
3
a) H. Meng, Z. Bao, A. J. Lovinger, B.-C. Wang, A. M.
CDCl3): ¤ 0.90 (t, J = 7.2 Hz, 6H), 1.33-1.37 (m, 8H), 1.45-
1.52 (m, 4H), 1.78-1.85 (m, 4H), 4.35 (t, J = 6.5 Hz, 4H), 7.37
(s, 2H), 7.45 (s, 2H), 7.74 (s, 2H), 8.73 (s, 2H). 13C NMR
(100 MHz, CDCl3): ¤ 14.06, 22.62, 25.76, 29.21, 31.62,
66.91, 102.00, 125.75, 128.93, 130.32, 130.41, 135.75,
141.89, 146.18, 162.06. MS m/z: 550 [M+]. HR-ESI-MS:
m/z 551.1857 [M + H+] (calcd for C30H35O2N2S3, 551.1855).
Data for 4c, purified by column chromatography on silica gel
(10% EtOAc in hexane as eluent): 45% yield. Mp 198 °C.
1H NMR (400 MHz, CDCl3): ¤ 0.99 (t, J = 7.2 Hz, 6H),
1.33-1.37 (m, 8H), 1.45-1.51 (m, 4H), 1.79-1.86 (m, 4H),
4.35 (t, J = 6.5 Hz, 4H), 7.26 (d, J = 3.9 Hz, 2H), 7.28
(d, J = 3.9 Hz, 2H), 7.45 s, 2H), 7.73 (s, 2H), 8.73 (s, 2H).
13C NMR (100 MHz, CDCl3): ¤ 14.08, 22.64, 25.77, 29.23,
31.64, 66.94, 102.06, 124.37, 125.96, 128.96, 130.19, 130.43,
135.27, 136.56, 141.90, 146.12, 162.06. MS: m/z 632 [M+].
Anal. Calcd for C34H36N2O2S4: C, 64.52; H, 5.73; N, 4.43%.
Found: C, 64.60; H, 5.69; N, 4.40%.
1,4-Bis(5-methoxythieno[2,3-c]pyridin-2-yl)benzene (3a¤).
A mixture of 1a (0.771 g, 1.70 mmol), 1,4-bis(tributylstannyl)-
benzene (0.280 g, 0.849 mmol), [Pd(PPh3)4] (49 mg, 0.040
mmol), CuI (16.2 mg, 0.085 mmol), and CsF (0.257 mg,
1.7 mmol) in 10 mL of DMF was stirred at 100 °C for 24 h.
After usual workup, the residue was subjected to column
chromatography on silica gel (10% EtOAc in hexane as eluent)
to give 3a¤ (75% yield). Mp 205 °C. 1H NMR (400 MHz,
CDCl3): ¤ 4.02 (s, 6H), 7.29 (s, 2H), 7.68 (s, 6H), 8.77 (s, 2H).
13C NMR (100 MHz, CDCl3): ¤ 54.19, 101.63, 127.54, 128.81,
130.47, 130.97, 134.36, 136.03, 141.88, 146.88, 162.06. MS
m/z: 404 [M+]. HR-ESI-MS: m/z 405.0726 [M + H+] (calcd
for C22H17O2N2S2, 405.0726).
Mujsce, J. Am. Chem. Soc. 2001, 123, 9214. b) H. Meng, J. Zheng,
A. J. Lovinger, B.-C. Wang, P. G. Van Patten, Z. Bao, Chem.
Mater. 2003, 15, 1778.
4
C. Videlot-Ackermann, J. Ackermann, H. Brisset, K.
Kawamura, N. Yoshimoto, P. Raynal, A. El Kassmi, F. Fages,
J. Am. Chem. Soc. 2005, 127, 16346.
5
H. K. Tian, J. W. Shi, D. H. Yan, L. X. Wang, Y. H. Geng,
F. S. Wang, Adv. Mater. 2006, 18, 2149.
H. K. Tian, J. W. Shi, B. He, N. H. Hu, S. Q. Dong, D. H.
6
Yan, J. P. Zhang, Y. H. Geng, F. S. Wang, Adv. Funct. Mater. 2007,
17, 1940.
7
A. Facchetti, M.-H. Yoon, C. L. Stern, G. R. Hutchison,
M. A. Ratner, T. J. Marks, J. Am. Chem. Soc. 2004, 126, 13480.
The absorption edge of 4H was not reported in number
(Ref. 7) and thus was read from the literature figure.
All calculations were performed by the density functional
8
9
theory (DFT) calculations, using Gaussian 09 Program Package,
Revision A.02: M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E.
Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone,
B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li,
H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L.
Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J.
Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,
T. Vreven, J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro, M.
Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov,
R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J. C.
Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M. Millam,
M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J.
Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin,
R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K.
Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J.
Dannenberg, S. Dapprich, A. D. Daniels, O. Farkas, J. B.
Foresman, J. V. Ortiz, J. Cioslowski, D. J. Fox, Gaussian 09
(Revision A.02), Gaussian, Inc., Wallingford CT, 2009.
Supporting Information
1H and 13C NMR spectra of compounds 2a, 3c, and 3a¤. This
material is available free of charge on the web at http://
www.csj.jp/journals/bcsj/.