Chalcogen bonding and liquid crystallinity: Understanding the anomalous behaviour of the 4′-(alkylthio)[1,1′-biphenyl]-4-carbonitriles (nSCB)

Abstract The synthesis and characterisation of the first eleven members of the 4′-(alkylthio)[1,1′-biphenyl]-4-carbonitriles series is reported. All eleven members show monotropic liquid crystal behaviour. The first six members are exclusively nematogenic, the seventh member shows nematic and smectic A phases, and the higher homologues only smectic A behaviour. A comparison of their transitional behaviour with that of the corresponding alkyl and alkyloxy-cyanobiphenyls reveals a new pattern of behaviour. Specifically, the nematic-isotropic transition temperatures show a large decrease on passing from the methylthio to ethylthio homologues. This unexpected behaviour is interpreted in terms of chalcogen bonding.