Intrachain energy transfer in silylene-spaced alternating donor-acceptor divinylarene copolymers

Article abstract of DOI:10.1039/b206308e

Silylene-spaced donor-acceptor divinylarene copolymers are synthesized by hydrosilylation of bisalkynes 7 with bisvinylsilanes 3; efficient intrachain energy transfer between donor-acceptor chromophores is observed.

Full text of DOI:10.1039/b206308e

Intrachain energy transfer in silylene-spaced alternating donor–acceptor
divinylarene copolymers†
Yen-Ju Cheng, Tsyr-Yuan Hwu, Jui-Hung Hsu and Tien-Yau Luh*
Department of Chemistry, National Taiwan University, Taipei, Taiwan 106
Institute of Chemistry, Academia Sinica, Taipei, Taiwan 115. E-mail: tyluh@chem.sinica.edu.tw;
Fax: +886-2-2651-1488; Tel: +886-2-2789-8500
Received (in Cambridge, UK) 3rd July 2002, Accepted 23rd July 2002
First published as an Advance Article on the web 7th August 2002
Silylene-spaced donor–acceptor divinylarene copolymers
are synthesized by hydrosilylation of bisalkynes 7 with
bisvinylsilanes 3; efficient intrachain energy transfer be-
tween donor–acceptor chromophores is observed.
chromphores may also take place leading to transfer of energy.
We now describe the first example on the synthesis and
photophysics of silylene-spaced alternating donor–acceptor
copolymers 1.
Our strategy was to synthesize a series of monomeric silyl-
substituted divinylarenes 3. Based on the absorption and
emission properties of these monomers (Table 1), a series of
polymers 1 was designed so that the absorption of one
chromophore (Ar2) can overlap with the emission of the other
chromophore (Ar1). The synthesis of vinylsilanes 3 was based
on the nickel-catalyzed silylolefination of the corresponding
dithioacetals 5 followed by the reduction of the corresponding
Si–O bond in 6,3 whereas a Sonogashira reaction was employed
for the synthesis of bisalkynes 7. Hydrosilylation of 7 with 3
afforded the corresponding copolymers 1. Monomers 4 were
obtained similarly from 7 and 8.‡
Conjugated copolymers with alternating donor/acceptor repeat-
ing units have received much attention because the intra-
molecular charge transfer within the chain may result in
concomitant changes in band gaps, electrochemical and optical
properties.1 Alternatively, intramolecular energy transfer along
a non-conjugated supramolecular system or a polymer chain has
been extensively investigated because it may serve as a useful
model to mimic the natural light harvesting process.2 We and
others found that the silicon moiety in silylene spaced
divinylarene copolymers 1 may serve as an insulating tetra-
hedral spacer so that there is no conjugation along the polymeric
backbone.3,4 Intrachain chromophore interaction due to folding
of the polymer has been observed in silylene–divinylbenzene
copolymers 1a.3 It is known that photoinduced through-space
charge transfer may occur in 4-donor-4A-acceptor substituted
diphenyldimethylsilanes 2.5 Since 1 is synthesized by the
As shown in Table 1, the emission maximum of 4a matched
well with the absorption maximum of 3b. Fig. 1 shows the
concentration dependent emission spectra (excitation at 324
nm) of an equal molar mixture of 3b and 4a. It is noteworthy
that the intermolecular energy transfer between 4a and 3b does
not proceed efficiently. The fluorescence spectrum (excitation
at 324 nm) for polymer 1b is also included in Fig. 1 for
comparison, only emission from chromophore Ar2 being
observed. This result indicated that complete energy transfer
from diphenyloxadiazole moiety to terphenylene-tetravinylene
chromophore occurred in 1b. In a similar manner, efficient
energy transfer from divinylbenzene to divinylstilbene in 1c and
from divinyldialkoxybenzene to terphenylene-tetravinylene
hydrosilylation of bisalkynes 7 with bisvinylsilanes 3,3 the two
neighboring chromophores in 1 can be different and alternating.
It is envisaged that interaction between the neighboring
† Electronic supplementary information (ESI) available: experimental
details. See http://www.rsc.org/suppdata/cc/b2/b206308e/
1978
CHEM. COMMUN., 2002, 1978–1979
This journal is © The Royal Society of Chemistry 2002

Fig. 2 Emission spectra (excitation wavelength: 300 nm) of 1c (—), 4b (…)
and absorption spectrum of 3c (Ã) in CHCl3.
Fig. 3 Emission spectra (excitation wavelength: 360 nm) of 1d (—), 4c (…)
and absorption spectrum of 3a (Ã) in CHCl3.
Table 1 Absorption and emission properties of polymers 1 and monomers
3 and 4
to 100 fold) and with solvents ( < 3 nm in benzene, CHCl3, THF
and EtOAc). Energy transfer therefore should occur within the
polymer chain. Photoinduced charge transfer,5 if any, would
apparently play little role in these polymers.
We thank the Ministry of Education and the National Science
Council for financial support.
Substrate
lmax/nm
lem/nm
Mn (PDI)
1b
1c
1d
3a
3b
3c
4a
4b
4c
328, 411
345, 355
345, 408
338, 411
348, 413
355
324
263, 300
262, 360
471, 495
396, 415
468, 496
467, 490
467, 490
392, 411
363, 384, 401
334, 347
418
4100 (1.5)
3200 (2.7)
3990 (1.5)
Notes and references
‡ All new compounds gave satisfactory spectroscopic and analytical data.
The details are described in the ESI.†
1 T. Yamamoto, Z.-h. Zhou, T. Kanbara, M. Shimura, K. Kizu, T.
Maruyama, Y. Nakamura, T. Fukuda, B.-L. Lee, N. Ooba, S. Tomaru, T.
Kurihara, T. Kaino, K. Kubota and S. Sasaki, J. Am. Chem. Soc., 1996,
118, 10389.
2 S. E. Webber, Chem. Rev, 1990, 90, 1469; A. Adronov S. L. Gilat, J. M.
J. Fréchet, K. Ohta, F. V. R. Neuwahl and G. R. Fleming, J. Am. Chem.
Soc., 2000, 122, 1175; M. A. Fox, Acc. Chem. Res, 1999, 32, 201; C.
Devadoss, P. Bharathi and J. S. Moore, J. Am. Chem. Soc., 1996, 118,
9635.
3 R.-M. Chen, K.-M. Chien, K.-T. Wong, B.-Y. Jin and T.-Y. Luh, J. Am.
Chem. Soc., 1997, 119, 11321.
4 R. J. P. Corriu, C. Guerin, B. Henner, T. Kuhlmann, A. Jean, F. Garnier
and A. Yassar, Chem. Mater, 1990, 2, 351; Y. Pang, S. Ijadi-Maghsoodi
and T. J. Barton, Macromolecules, 1993, 26, 5671; H. K. Kim, M.-K. Ryu
and S.-M. Lee, Macromolecules, 1997, 30, 1236; Y.-J. Miao and G. C.
Bazan, Macromolecules, 1997, 30, 7414; A. Mori, E. Takahisa, H.
Kajiro, Y. Nishihara and T. Hiyama, Macromolecules, 2000, 33, 1115; A.
Kunai, E. Toyoda, I. Nagamoto, T. Horio and M. Ishikawa, Organome-
tallics, 1996, 15, 75; H. Li and R. West, Macromolecules, 1998, 31,
2866.
5 C. A. van Walree, M. R. P. Roest, W. Schuddeboom, L. W. Jenneskens,
J. W. Verhoeven, J. M. Warman, H. Kooijman and A. L. Spek, J. Am.
Chem. Soc, 1996, 118, 8395; A. Zehnacker, F. Lahmani, C. A. Van
Walree and L. W. Jenneskens, J. Phys. Chem. A, 2000, 104, 1377.
Fig. 1 Concentration dependent fluorescence spectra (excitation wave-
length: 324 nm) of an equal molar mixture of 3b and 4a in CHCl3 (a: 1 3
1021 g mL21; b: 1 3 1022 g mL21; c: 1 3 1023 g mL21) and (d)
fluorescence spectrum (excitation wavelength: 324 nm) of 1b in CHCl3.
chromophore in 1d was observed (Figs. 2 and 3). The emission
profiles remained essentially unchanged with concentration (up
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1979