An efficient route to stable room-temperature liquid-crystalline triphenylenes

Fourfold 2,3,6,10-alkoxycarbonyl-substituted triphenylenes are synthesised in five concise steps from 4-methylcyclohexanone by selective monoformylation of 2,6,10-trimethyltriphenylene, followed by oxidation in aqueous dichromate solution. Their low symmetry leads to mesogenic self assembly in a columnar liquid-crystalline state at or near room temperature, depending on the choice of alkyl group. These materials unite several properties that are desirable in charge-transporting thin films for organic optoelectronics: room-temperature self assembly into structures of good charge mobility and high viscosity, low electron density in the aromatic core, smooth synthetic access, and optical transparency. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)