Smectic bimetallomesogens in β-enaminoketonate copper complexes: the steric effect of a methyl substituent on the core group and the crystal structure

Abstract

A systematic study has been made of the liquid crystalline properties of two types of copper complexes derived from enamino-β-ketonate and iminopropyl-β-ketonate Schiff bases that exhibit mesomorphism. These complexes are structurally similar, and all have a bimetallic center as an expanded core group. The mesophase stability depends upon the steric bulk between the layer structures. The enamino-β-ketonate complexes exhibit smectic A phases, however, the iminopropyl-β-diketonates are not liquid crystalline. Examination of the structural features of these complexes revealed that the presence of a methyl group attached to the core group was the cause for the lack of liquid crystallinity observed in the latter. The crystal and molecular structure of bis[3,5-dioctanoylphenyl 2-(3-hydroxypropyl)iminopropyl ketonato]copper(II) was determined by means of X-ray analysis. The Cu· · ·Cu intramolecular separation is 3.0375(5) Å. The planar geometry is slightly distorted toward square pyramidal by displacement of the copper by 0.018 Å from the mean plane through atoms N(1), O(2), O(1A) and O(1).