The synthesis and mesogenic behaviour of the first series of low molar mass thieno[3,2-b]thiophene-2-carboxylate ester-based mesogens

Abstract

The synthesis of a family of alkyl 5-(4-hexyloxyphenyl)thieno[3,2-b]thiophene-2-carboxylate liquid crystals is described. The synthetic methodology utilised includes a Fiesselmann synthesis of the thieno[3,2-b]thiophene core, and the first report of a completely regioselective α-bromination of the resulting thieno[3,2-b]thiophene-2-carboxylate ester. The target materials display enantiotropic smectic A phases with melting points and transition temperatures that are significantly higher than their phenyl analogues. The synthesis and mesomorphic behaviour of these new materials is reported and discussed.