Synthesis of Precursor Molecules for Low Band Gap Polymers

Abstract

The synthesis and characterization of precursors for polyarene- and hetarenemethylenes (PAM) of structure 3, which are predicted to be low band gap polymers are described. The precursor molecules 4 are synthesized from the corresponding 2-thiophene- and 2-pyrrole- carbaldehydes 6a and 6b by Knoevenagel condensation with 2,5-dihydrothiophene 1-oxide (9) and/or the analogous benzo- and naphto-annulated sulfoxides 9. The sulfoxide groups in 9 are easily reduced with formation of the sulfides 11. The synthesis of the precursor molecules 20-22 containing two directly linked quinoid structures is also described.To increase the solubility of the 1,3-bis(2-thienylmethylene)-1,3-dihydroisothianaphtene systems 4 e.g.alkoxy substituents are introduced into the annulated benzene ring of 4