Ferrocene-containing thermotropic liquid crystals: Laterally connected twins

A novel type of liquid crystalline ferrocene derivatives has been synthesised and investigated. These metallomesogens consist of two rod-like 4,4('')-disubstituted p-terphenyl rigid cores which are laterally connected to each other via spacers incorporating 1,1'-disubstituted ferrocene units. These materials have broad smectic A mesophases and considerably increased mesomorphic ranges in comparison to the structurally related derivatives incorporating a 1,4-disubstituted benzene ring instead of the ferrocene unit in the spacer. For comparison, a molecule consisting of a single 4,4('')-disubstituted p-terphenyl unit carrying a lateral ferrocene substituent and the corresponding benzoate were also prepared and investigated.