Chemistry Letters Vol.33, No.11 (2004)
1483
cause 4 indicated the oxidation wave at 1.13 V and the precursor
polymer 2 (Figure 1b, dashed line) showed no corresponding ox-
idation waves. The reduction wave at ꢂ0:22 V is assigned to the
reduction of the oxidized dithiolthione ring, and the redox couple
indicates the improvement of the electrochemical capacity of the
polymer 3 comparing with the polymer 2 and the stability of 3
against potential sweep. The oxidation wave at 1.87 V and the
reduction wave at 1.60 V are considered to belong to the redox
reaction of the polythiophene main chain.
ꢀ-conjugated polymer such as polythiophene. The polymer 3
showed fluorescence at 569 nm (ꢁex ¼ 472 nm). We are now
investigating the conductivity and fluorescence of 3 in the form
of a radical or cation at different potentials.
This work was partially supported by 21COE Research on
‘‘Practical Nano-Chemistry’’ from MEXT, Japan.
References and Notes
In order to trace the electronic states of the oxidized 3, UV–
vis spectroelectrochemical studies were carried out as shown in
Figure 2. A ꢀ–ꢀꢀ absorption band found at 472 nm before the
oxidation changed over two potential intervals ((i)0–1.6 V and
(ii)1.7–2.0 V vs Ag/AgCl). In the first range of potential, the ab-
sorbance of at 472 nm ꢀ–ꢀꢀ band decreased with an accompany-
ing increase of the absorbance at 726 nm, which is assigned
to the oxidation of the dithiolthion ring by comparison with
the CV of 3. At the higher potential over 1.7 V, the ꢁmax
of the ꢀ–ꢀꢀ absorption was shifted to shorter wavelength by
the oxidation of the polythiophene and the absorbance at
726 nm decreased.
1
For a review, see: for example, ‘‘Handbook of Conducting
Polymers, 2nd ed.,’’ ed. by T. A. Skotheim, R. L.
Elsenbaumer, and J. R. Reynolds, Wiley, Weinhem (2000);
J. Roncali, Chem. Rev., 92, 711 (1992); A. O. Patil, A. J.
Heeger, and F. Wudl, Chem. Rev., 88, 183 (1988); T.
Yamamoto, Bull. Chem. Soc. Jpn., 72, 621 (1999).
A. Cravino, G. Zerza, H. Neugebauer, M. Maggini, S.
Bucella, E. Menna, M. Svensson, M. R. Andersson, C. J.
Brabec, and N. S. Sariciftci, J. Phys. Chem. B, 106, 70
(2002); F. Wang and Y. H. Lai, Macromolecule, 36, 536
(2003); T. Nishiumi, M. Higuchi, and K. Yamamoto,
Macromolecules, 36, 6325 (2003); J. Chen, M. Mitsuishi,
A. Aoki, and T. Miyashita, Chem. Commun., 2002, 2856.
P. S. Landis, Chem. Rev., 65, 237 (1964); D. D. Mysyk, I. F.
Prepichka, D. F. Prepichka, M. R. Bryce, A. F. Popov, L. M.
Goldenberg, and A. J. Moore, J. Org. Chem., 64, 6937
(1999); M. Chollet, B. Legouin, and J. L. Burgot, J. Chem.
Soc., Perkin Trans. 2, 1998, 2227; W. Kim and K. S. Gates,
Chem. Res. Toxicol., 10, 11691 (1997).
2
3
4
0V
0.5
1H NMR (CDCl3, 500 MHz): ꢂ 7.33 (1H, m, Th–H), 4.92
(1H, m, Th–H), 3.80 (6H, m, –OCH3). IR (NaCl, cmꢂ1):
2953 (ꢃC-H), 1738 (ꢂC=O). GPC (CHCl3, polystylene stand-
ard): Mn ¼ 1350, Mw ¼ 1440 (Mw=Mn ¼ 1:1).
2.0V
335
B/mT
333
337
5
6
B. S. Pedersen and S. O. Lawesson, Tetrahedron, 35, 2433
(1979); T. J. Curphey, J. Org. Chem., 67, 6461 (2002).
1H NMR (CDCl3, 500 MHz): ꢂ 7.84 (0.7H, m, vinyl–H),
6.98 (1H, m, Th–H), 3.80 (1.8H, m, –OCH3). IR (NaCl,
cmꢂ1): 2950 (ꢃC-H), 1739 (ꢂC=O), 1259 (ꢂC=S). GPC (CHCl3,
polystylene standard): Mn ¼ 3100, Mw ¼ 4000 (Mw=Mn ¼
1:3). The introduction ratio of the dithiolthione ring was
calculated by comparing to the proton signal of thiophene
ring.
0
500
700
900
300
λ
/nm
Figure 2. Absorption spectra of 3 [1 mM in DMF containing
0.1 M TBABF4. Applied potential: solid line: 0, 1.0, 1.5, 1.6 V
(5, 10, 15, and 40 min), dashed line: 1.7, 1.8, 1.9, 2.0 V] and
ESR spectrum of oxidized 3 (10 mM in DMF containing 0.1 M
TBABF4. Applied potential: 0, 1.1, 1.5, 1.6, 2.0 V).
7
8
9
1H NMR (CDCl3, 500 MHz): ꢂ 8.34 (1H, s, vinyl–H), 7.93
(1H, m, Th–H), 7.23 (2H, m, Th–H). 13C NMR (CDCl3): ꢂ
212, 154, 143, 133, 127, 125, 124. IR (NaCl, cmꢂ1): 3052
(ꢃC-H), 1299 (ꢂC=S). MS: m=z 215 (Mþ). The cyclization
was performed with the same condition as that of the
polymer 2.
J. L. Burgot, A. Darchen, and S. Dervout, J. Electroanal.
Chem., 537, 145 (2002); J. L. Burgot, A. Darchen, and M.
Saidi, J. Electrochim. Acta, 48, 107 (2002); M. Liu, S. J.
Visco, and L. C. De Jonghe, J. Electrochem. Soc., 136,
2570 (1989); K. Naoi, Y. Iwamizu, M. Mori, and Y.
Naruoka, J. Electrochem. Soc., 144, 1185 (1997).
There was no increase of absorbance at 726 nm in the
oxidation of 2 (data not shown). The ESR signal of 3 was also
monitored with applying potential. There was no change of the
ESR signal at 0–1.0 V, however, a broad signal at g ¼ 2:0019
(line width: 0.34 mT) was detected at 1.1–1.4 V (Figure 2). It in-
dicated that the cation radical appeared by the oxidation of the
dithiolthione ring. The signal was split at 1.5 V and became
sharp (line width: 0.12 mT) over 1.6 V. Therefore, we consider
that the absorption band at 726 nm shown in Figure 2 would
be associated with the dithiolthione radical affected by polythio-
phene radical.9
K. Buga, K. Kepczynska, I. Kulszewicz-Bajer, R. Demadrill,
´
A. Pron, S. Quillard, S. Lefrant, and M. Zagorska,
In conclusion, we found that 3-dithiolthione-substituted
polythiophene 3 has reversible redox activity, and made the first
observations of the radical cation of dithiolthione formed by
the oxidation of the dithiolthione ring directly conjugated to a
Macromolecules, 37, 769 (2004); F. Wang and Y. H. Lai,
Macromolecules, 36, 536 (2003); K. Yoshino, X. H. Yin,
S. Morita, M. Nakazono, T. Kawai, M. Ozaki, S. H. Jin,
and S. K. Choi, Jpn. J. Appl. Phys., 32, L1673 (1993).
Published on the web (Advance View) October 16, 2004; DOI 10.1246/cl.2004.1482