Nematic tolanes and acetylenes

Abstract

The first liquid crystals incorporating a non-conjugated carbon–carbon triple bond in the terminal chain to exhibit a nematic phase above the melting point are reported. A variety of compounds incorporating a carbon–carbon triple bond in the terminal chain or between two phenyl rings have been synthesised as part of an investigation of the effects of the shape, conformation and rigidity of the terminal chains of liquid crystals on their mesophase behaviour. A series of related tolanes incorporating an alkenyloxy chain with an additional carbon–carbon double bond or a simple alkoxy chain as a terminal substituent also were prepared for comparison purposes.