The Crystal and Molecular Structures of Three Homologous, Mesogenic Trans, Trans-4'-Alkylbicyclohexyl-4-carbonitriles (Cyclohexylcyclohexanes, CCHs)

Abstract

The crystal and molecular structures of three homologous trans, trans-4'-alkylbicyclohexyl-4-carbonitriles (Cyclohexylcyclohexanes, CCHs) with the following alkyl groups: propyl (CCH3); pentyl (CCH5); heptyl (CCH7) are described. All three compounds exhibit liquid crystalline phases at higher temperatures. Both cyclohexyl rings assume the chair conformation and the alkyl groups adopt the trans-conformation.

In the crystalline state two kinds of layer structure are discussed. In the first type, the long axes of the molecules are tilted to the normal of the layer. In the second kind of structure, the longest molecular axis lies within the layer. The role of the cyano dipoles is discussed. In CCH3 a dipole-dipole interaction in the crystal is indicated. The packing in the solid crystalline states of the three compounds is compared with the known models, derived from X-ray data, for the liquid crystalline state.