Tetraphenylenes as novel saddle-shaped building blocks of columnar and smectic liquid crystals

Abstract

We report the synthesis and liquid crystalline properties of novel mesogenic octaalkyloxytetraphenylenes. Starting from 4-bromoveratrol, the saddle-shaped target tetraphenylenes were obtained in five steps. Compounds with shorter C7–C12 alkyl chain lengths displayed enantiotropic hexagonal columnar mesophases. For the decyloxy derivative a lattice constant d=27.4 Å was determined by X-ray diffraction. The compounds with longer C13–C16 alkyl chains exhibited enantiotropic mesophases, which are most probably smectic in nature. X-ray diffraction of the R=C₁₄H₂₉ derivative indicated a phase transition within the smectic mesophases.