Liquid Crystallinity of 2-Acyl-7-[p-(alkoxy)benzylideneamino]fluorenes

The liquid crystallinity of the title compounds was studied in order to design a stable liquid crystal used at low temperature. The Schiff base derived from 1- or 3-fluoreneamine scarcely shows liquid crystallinity. The propionyl group is effective for lowering the melting point of the mesophase compared to the acetyl group in a series of the title substances. The liquid crystallinity of the title compounds was compared with that of biphenyl homologues. A mesophase of the title substances was observed over a wider range of temperatures than in the case of biphenyl derivatives in a series of propionyl groups.