Δ^4,4‘-Dicyclopenta[2,1-<i>b</i>:3,4-<i>b</i>‘]dithiophene. A Conjugated Bridging Unit for Low Band Gap Conducting Polymers

Abstract

Δ 4,4‘ -Dicyclopenta[2,1- b:3,4- b ‘]dithiophene has been prepared from cyclopenta[2,1- b:3,4- b ‘]bithiophen-4-one and its electrochemical and spectroscopic properties have been characterized. Its low HOMO−LUMO gap and facile electrochemical polymerization make it an attractive building block for low band gap conducting polymers. Films of poly-(Δ 4,4‘ -dicyclopenta[2,1- b:3,4- b ‘]dithiophene) on electrodes have been characterized by cyclic voltammetry, electronic absorption spectroscopy, IR spectroscopy, and in situ conductivity measurements. The spectroscopic and electrochemical results confirm the formation of a polymeric material with long conjugation length and low band gap (ca. 0.5 eV). The intrinsic conductivity is consistent with this band gap.