Synthesis and Electronic Properties of Aldehyde End-Capped Thiophene Oligomers and Other α,ω-Substituted Sexithiophenes

Abstract

A series of α,ω-aldehyde end-capped oligomers of thiophene with three, four, five, six, and eight thiophene units have been synthesized using the palladium-catalyzed Stille's coupling reactions. The UV−vis spectral data indicate that these aldehyde end-capped oligomers have longer conjugation lengths as evidenced by the higher λmax values than the corresponding unsubstituted oligothiophenes. The λmax value increases as the number of thiophene units is increased. The intrinsic conductivity of the solution-cast films of the aldehyde end-capped oligothiophenes is generally higher than that of their corresponding unsubstituted counterparts. Other α,ω-substituted sexithiophenes, such as n-dodecanoyl, tert-butyldimethylsilyl, hydroxymethyl, and [(n-butoxyethoxy)ethoxy]methyl sexithiophenes, have also been synthesized. α,ω-Bis([(n-butoxyethoxy)ethoxy]methyl)sexithiophene has a remarkably high solubility in chloroform (1.8 g/L) and a conductivity (1 × 10-6 S/cm) comparable to the unsubstituted sexithiophene.