Abstract A series of 5-(arylethynyl)tropolone derivatives and their corresponding benzenoid analogs were synthesized to investigate their mesomorphic properties. 2-(Dodecanoyloxy)-5-(phenylethynyl)tropone (2a) exhibited no mesomorphic behavior, whereas the 2-(4-alkyloxybenzoyloxy)-5-(phenylethynyl)tropones (3a) showed monotropic or enantiotropic nematic (N) phases. Introduction of the 4-alkyloxybenzoyloxy group markedly enhanced the liquid-crystalline behavior. 2-(Dodecanoyloxy)-5-(biphenylethynyl)tropone (2b) exhibited an enantiotropic SmA phase, while the 2-(4-alkoxybenzoyloxy)-5-(biphenylethynyl)tropone derivatives (3b) showed both enantiotropic bilayer SmA and N phases. In addition, compound 3b12 exhibited a reentrant nematic phase, whereas the corresponding benzenoid analog (5b12) displayed an enantiotropic nematic phase.
Kubo et al. (Wed,) studied this question.