About
Research
Academics
People
Board
Torsionally
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-bridgedPBTr-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.