Synthesis, transition temperatures and optical anisotropy of some isothiocyanato-substituted biphenyls

A range of alkyl-, alkoxy- and alkylsulfanyl-substituted biphenyls with terminal isothiocyanato substituents have been prepared and their suitability as dopants in nematic mixtures of high optical anisotropy evaluated. Palladium-catalysed cross-coupling reactions involving arylboronic acids have been used to synthesize the biphenyl core unit, followed by functional-group interconversions to give the desired isothiocyanato-substituted materials. The –NCS terminal group is in conjugation with the biphenyl core and this combination was expected to provide materials of high optical anisotropy. Mesogenic and optical properties have been determined and are discussed.