1003
S
S
handled under ambient conditions. However, they were photo-
active and irradiation of the THF solutions in argon for 1 h with
a low-pressure UV lamp (254 nm) resulted in the complete
decomposition of the DTSBs. Although we have not yet obtained
experimental data to discuss the detailed mechanism, naphthalene
and bi(benzothiophene) were detected in the photolyzed solution
of DTSB3 in 10 and 5% yields, respectively, suggesting the
photochemical cleavage of the Sb-C bonds.
In conclusion, we prepared DTSBs as the first compounds
with a stibole core fused with two or more heteroaromatic rings.8
The optical and computational studies indicated that they possess
the expanded conjugation with low-lying HOMO and LUMO,
like DTS. Taking the widely accepted utilities of heteroatom-
bridged bithiophenes into account, DTSB would show interesting
functionalities and studies concerning the synthesis of DTSB-
containing ³-conjugated functional materials are under way. Such
antimony-heteroaromatic compounds seem to be also of interest
in biological aspects.9
Me3Si
n-BuLi p-TolSbCl2
ether THF
SiMe3
SiMe3
Me3Si
S
S
Sb
-80°C -80°C reflux
Br Br
DTSB1 13%
S
S
S
S
Ar-SbCl2
n-BuLi
ether
-80°C -80°C reflux
THF
Sb
Ar
Br Br
DTSB2 Ar = p-Tol 13%
DTSB3 Ar = 2-naphthyl 20%
Scheme 1. Synthesis of DTSBs.
Table 1. Properties of bridged bithiophenes
UV abs
Emissionc
max/nm max/nm
Compound
Mp/°C
-
-
DTSB1
DTSB2
DTSB3
DTBI1a
DTS1b
355
420, 625
437
117.5d
266, 323, 337, 374
204.7d
This work was partly supported by MEXT KAKENHI
(No. 24102005).
269, 323, 338, 374
443
248.5d
356
356
400, 625
425
114-116e
158-156e
aRef. 7. bRef. 3. cExcited at the absorption -max. dDetermined by DSC.
eDetermined by visual observation.
References and Notes
1
T. Baumgartner, W. Bergmans, T. Kárpáti, T. Neumann, M. Nieger, L.
Table 2. HOMO and LUMO energy levels of dithienometalloles,
derived from DFT calculations at B3LYP/LanL2DZ
Compound HOMO/eV LUMO/eV LUMO-HOMO/eV
2
3
J. Ohshita, M. Nodono, T. Watanabe, Y. Ueno, A. Kunai, Y. Harima, K.
Ohshita, M. Nodono, H. Kai, T. Watanabe, A. Kunai, K. Komaguchi,
M. Shiotani, A. Adachi, K. Okita, Y. Harima, K. Yamashita, M.
DTSB0
DTBI0
DTS0
¹5.67
¹5.59
¹5.65
¹1.77
¹1.69
¹1.76
3.90
3.90
3.89
4
J. Ohshita, H. Kai, A. Takata, T. Iida, A. Kunai, N. Ohta, K.
Komaguchi, M. Shiotani, A. Adachi, K. Sakamaki, K. Okita, Organo-
130, 16144; J. S. Moon, C. J. Takacs, S. Cho, R. C. Coffin, H. Kim,
S. Beaupré, Y. Zhang, J.-R. Pouliot, S. Wakim, J. Zhou, M. Leclerc, Z.
(a)
(b)
(c)
S
S
Sb
5
6
C. M. Amb, S. Chen, K. R. Graham, J. Subbiah, C. E. Small, F. So,
J. Smith, E. B. Domingo, N. Stingelin, M. A. McLachlan, K. Song,
J. Ohshita, Y.-M. Hwang, T. Mizumo, H. Yoshida, Y. Ooyama, Y.
Ohshita, Y. Harima, T. Mizumo, Y. Ooyama, Y. Morihara, T. Izawa, T.
P. Berrouard, N. Allard, B. R. Aïch, C. N. Garon, Y. Tao, M. Leclerc,
J. Ohshita, S. Matsui, R. Yamamoto, T. Mizumo, Y. Ooyama, Y.
Harima, T. Murafuji, K. Tao, Y. Kuramochi, T. Kaikoh, H.
The synthesis of monothienostibole was reported, previously. How-
ever, no properties were given, except for the melting point. See: S.
For example: P. Sharma, N. Rosas, A. Cabrera, A. Toscano, M.
de Jesus Silva, D. Perez, L. Velasco, J. Perez, R. Gutierez,
Figure 2. (a) Structure, and (b) HOMO and (c) LUMO profiles of
DTSB0, derived from DFT calculations.
Dithienostiboles DTSB2 and DTSB3 showed red-shifted
absorption and emission maxima from those of DTSB1, reflecting
the expanded ³ conjugation. No remarkable substituent effects on
the optical properties are observed for DTSB2 and DTSB3.
Emission spectra of the present DTSBs exhibited maxima at 420-
443 nm with quantum efficiencies of 1-2%, similar to DTBIs.7
The solid-state emission was investigated for DTSB3 that showed
a broad band at -max = 461 nm, red-shifted by about 30 nm from
that in chloroform, suggesting intermolecular interaction in the
solid states. Interestingly, a broad band centered at 625 nm was
also observed for DTSB1 both in the solution phase and the solid
states, similar to the phosphorescence peak of DTBI1. However,
this peak was too weak to investigate its origin in detail. The
present DTSBs were stable in the solid states and could be
7
8
9
10 Supporting Information including experimental and computational
details is also available electronically on the CSJ-Journal Web site,
Chem. Lett. 2012, 41, 1002-1003
© 2012 The Chemical Society of Japan