Mesomorphic properties of 2-acyloxy5-(4-alkoxyphenylazo)tropones, 2-acyloxy-5-(4-alkylphenylazo)tropones, and 2-acyloxy-5-(4-alkoxycarbonylphenylazo)tropones

Abstract

Three series of mesomorphic 2-acyloxy-5-phenylazotropones with alkoxy, alkyl, and alkoxycarbonyl groups at C-4 on the phenyl ring were prepared. It was known that the corresponding 5-phenylazotropolone derivatives and their methyl ethers were not mesomorphic. 2-Acetyl-5-(4-hexyloxyphenylazo)tropone, however, shows a monotropic smectic A phase. Even an acetyl group is therefore able to induce a mesophase. The effects of terminal substitution of the tropone ring by groups such as alkoxy, alkoxycarbonyl, and alkyl on the clearing points are discussed.