A convenient synthesis of isothianaphthene oligomers and their electrochemical studies

Bi- and tri-isothianaphthene-α,ω-dicarbaldehydes were easily synthesized by using 4,7-dihydro-4,7-ethano-2-benzo[c]thiophene as a useful synthon of 1,3-unsubstituted isothianaphthene. The UV–vis absorptions of oligo-isothianaphthene derivatives exhibit a considerable bathochromic shift compared to the cases of other oligo-thiophene analogs, and their cyclic voltammetry shows narrowed HOMO–LUMO gaps of the isothianaphthene derivatives. This indicates high efficiency of π-electron delocalization in the oligo-isothianaphthenes along the conjugated backbone.