Liquid crystals containing a 2,6-disubstituted anthracene core—mesomorphism, charge transport and photochemical properties

Abstract

The synthesis of 2-(4-phenyl)-6-anthracenes and 4,4′-bisphenyl-2,6-anthracenes, disubstituted by saturated (decyloxy) or unsaturated ((Z)-dec-4-enyloxy) chains, is reported. All the materials are liquid crystals and exhibit smectic A and/or C phases. As compared to the saturated chains, the unsaturated ones provide a significant decrease of the transition temperatures. The presence of the central “lath-like” anthracene core in the rigid aromatic moiety is found to induce some molecular π-stackings, at short range, in the mesophases. This molecular peculiarity is thought to be in a large part responsible for the high charge-carrier mobility values measured (i.e. 2 × 10⁻³ cm² V⁻¹ s⁻²), despite the disordered character of the mesophases. Preliminary examination of photodimerisation revealed that the formation of photoadducts was very poor in the smectic phases as compared to the same experiment run in solution. This result was attributed to the instability of the anthracene photodimers at the too high temperatures of the mesophases.