The structure of cubane mono and 1,4-dicarboxylic acids in lyotropic liquid crystalline solution

Abstract

Proton nmr studies of cubane mono and 1,4-dicarboxylic acids in lyotropic liquid crystalline solution show that these molecules are distorted from the cubane structure. The protons of cubane dicarboxylate which are vicinal to their respective carboxylate group are displaced towards those groups along the C3 axis resulting in an elongation relative to a cube. In cubane monocarboxylate there is also a displacement of vicinal protons toward the carboxyl group, but this is accompanied by a displacement of the protons one carbon further removed, away from the carboxyl groups. The shape of this latter compound is comparable to that of a section of a cone with the narrow end of the cone defining the proton positions adjacent to the carboxyl group while the wide end of the cone defines the positions of the adjacent set of protons. The remaining proton of course sits on the C3 axis which determines the centre of symmetry of the cone.