Synthesis and liquid crystal properties of mixed alkynyl-alkoxy-triphenylenes

The synthesis and liquid crystalline properties of some new multisubstituted triphenylenes are reported. The materials bear combinations of alkyne and alkoxy substituents and were designed to probe the structural factors controlling mesophase formation, type and stability in triphenylene discotics. A combination of factors contributes to mesophase stability in these systems. Compounds bearing two alkynes can support, and indeed enhance, columnar mesophase behaviour, but mesophase behaviour is completely suppressed when four or six alkynes are present. A twinned structure linked by a diacetylene bridge shows a stable nematic phase, but conversion to a saturated bridge destroys all mesophase behaviour.