The electronic characterization of conjugated aryl-substituted 2,5-bis(2-thien-2-ylethenyl) thiophene-based oligomers

A series of 2,5-bis(2-thien-2-ylethenyl) thiophene-based oligomers with a para-R-arylethenyl substituent

have been subjected to electrochemical (cyclic voltammetry and electronic absorption spectroscopy) and

density functional theory characterization. The primary aim of this investigation is to characterize the

behavior of these oligomers in the oxidized state. Oligomers without methyl ‘end-caps’ undergo facile

r-dimerization; however there is no evidence for the formation of higher oligomers. The oxidized

r-dimers exist in both cationic and dicationic form. Oligomers with methyl ‘end-caps’ do not show

any evidence of r-dimerization. The inductive capacity of the para-R substituent has a significant bearing

on the electronic properties of the oligomer, in particular, oligomers with more electron-withdrawing

substituents have charge transfer character associated with the dominant electronic excitations.