Heteroaryl functionalised diacetylenes: preparation and solid-state reactivity

Abstract

Diacetylenes are known to undergo solid-state topochemical polymerisation to give polydiacetylenes. The reactivity of the monomer is controlled by the arrangement of the molecules in the crystal lattice wherein certain parametric conditions must be met for 1,4-addition to proceed. In the present paper, we investigated the structure–reactivity relationship of a class of diacetylene monomers. Heteroaryl moieties such as thiophene, benzo[b]thiophene and quinoline as one or both directly bound side groups of a diacetylene backbone were used. Thus various symmetrical as well as unsymmetrical diacetylenes were prepared and characterised. The solid-state polymerisation behaviour of these diacetylenes was studied in the light of their single-crystal X-ray structure. It was found that in order to react in the solid state, the diacetylenes must have the required lattice parameters. However, even when the required lattice parameters are met, the diacetylene monomers do not necessarily undergo solid-state 1,4-addition polymerisation, implying the existence of further controlling factors to determine reactivity.