Optically Active Mesogenic Dispiro[2.0.2.1]Heptane Derivatives and their Unusual Physical Properties

Abstract

Physical properties, i.e. phase transition temperatures, response times, Ps values, tilt angles, helical twisting powers and helical twisting senses of a series of novel ferroelectric liquid crystalline compounds with non-substituted and halogen-substituted dispiro[2.0.2.1]heptyl moieties in their side chains have been measured. When mixed with an achiral SmC base mixture, the resulting SmC* mixtures containing the novel compounds showed ferroelectricity, and the novel compounds were estimated as useful dopants for ferroelectric liquid crystal mixtures. Further unusual properties were observed with the combinations of the two diastereomeric novel compounds, for example (1S,3R,4S)-4a and (1S,3R,4R)-5a. They showed opposite signs for the Ps and the same sense for the N* helical twisting, which clearly suggests that the direction of the Ps and helical sense of N* must be derived from different origins.