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Download fileTorsionally Responsive Tropone-Fused Conjugated Polymers
journal contribution
posted on 2015-10-13, 00:00 authored by Kyung-su Kim, Inhwan Cha, Daeheum Cho, Jongho Ahn, Chinnadurai Satheeshkumar, Ki Seok Yang, Jin Yong Lee, Yunmi Lee, Changsik SongTorsionally responsive molecular
systems can change their electronic
properties according to the dihedral angles and can be utilized as
sensory materials. We have designed and synthesized novel tropone-fused
conjugated polymers PBTr, PBTr-T, and PBTr-Tz that showed interesting dihedral-angle-dependent variations
in UV–vis absorptions. Tropone-fused thiophene derivatives
were prepared from one-step condensation of thiophene-3,4-dialdehyde
and aliphatic ketones via a modular, facile, and high-yielding method.
Subsequent halogenation and Stille cross-coupling polymerization with
a bis(stannyl)benzodithiophene resulted in a tropone-fused conjugated
polymer PBTr. We were also able to prepare thiophene-
and thiazole-bridged polymers, PBTr-T and PBTr-Tz, respectively, using similar synthetic methods. Electronic absorptions
of the newly synthesized PBTrs were measured in solutions
and in films states. Substantial red-shifts occurred in the case of
thiophene-bridged PBTr-T, whereas almost no shift was
observed for thiazole-bridged PBTr-Tz. We attributed
this to the substantial change in the torsional angle between the
tropone-fused thiophene moiety and thiophene, which was further supported
by density functional theory (DFT) calculations. Similar spectral
changes of UV–vis absorptions were observed when a poor solvent
(methanol) was introduced to a chloroform solution of PBTr-T. Reverse torsional angle variations were realized with initially
planar PBTr-Tz by introducing steric hindrance through
protonation on the thiazole rings. We believe that torsionally responsive
tropone-fused conjugated polymers are promising as novel platforms
for sensory applications.