Structure and properties of new liquid crystalline cubane‐1,4‐dicarboxylic acid derivatives

Abstract

New symmetrical esters of cubane‐1,4‐dicarboxylic acid have been prepared. These compounds have the bulky cubane moiety as the central building block. Five classes of derivative have been synthesized: (a) bis[(4‐alkyl)phenyl]cubane‐1,4‐dicarboxylates; (b) bis[(4‐alkoxy)phenyl]cubane‐1,4‐dicarboxylates; (c) the two chiral derivatives bis(cholestenyl)cubane‐1,4‐dicarboxylate, and (S)‐bis[4‐(2‐methylbutyloxycarbonyl)phenyl]cubane‐1,4‐dicarboxylate; (d) three members of the bis [4‐(2,2‐alkoxycarbonylvinyl)phenyl]cubane‐1,4‐dicarboxylates; and (e) bis[(4′‐ethoxycarbonyl)‐1,1′‐biphenyl‐4‐yl]cubane‐1,4‐dicarboxylate. The shorter homologues of the alkoxyphenyl ester series exhibited a nematic (N) phase. No mesophase was observed for the pentyl derivative, while the higher homologues showed a smectic A (SmA) phase according to X‐ray investigations. The 4‐alkylphenyl and chiral derivatives showed only a melting point. The double swallow tailed bis[4‐(2,2‐alkoxycarbonylvinyl)phenyl)]cubane‐1,4‐dicarboxylates also exhibited no mesophase behaviour. On increasing the number of aromatic rings on both sides of the central cubane moiety, N and SmA phases appeared at higher temperatures. In binary mixtures of homologues of alkoxyphenylcubane esters, the temperature range of the SmA phase of the individual compounds became wider and enantiotropic in nature.

Acknowledgement

The authors are grateful to Professor John Tsanaktsidis for helpful discussions; also the Hungarian Research Fund OTKA T030401 and T032667, and the Austrian‐Hungarian Foundation 56ÖU4 for financial support. This work was also supported by COST D14 WG 159.

Notes

^a( ) Denotes monotropic transitions.

^bEnthalpy could not be resolved.

^cPOM observation.

^dDecomposition.