FERROELECTRIC LIQUID-CRYSTALS WITH A TOLANE RIGID CORE AND AN OPTICALLY-ACTIVE ALKYL SULFINATE GROUP - SYNTHESIS, CHARACTERIZATION, MOLECULAR MODELING, AND STEREOCHEMICAL INVESTIGATIONS

The synthesis and the properties of new ferroelectric liquid-crystalli ne compounds with a tolane rigid core and an optically active alkyl su lfinate group are reported. These compounds contain two chiral centers : a sulfinate group and a branched aliphatic chain. The diastereomers having opposite configuration at the sulfur center and the same config uration at carbon have been isolated; one exhibits smectic C and A ph ases, the other only a smectic A phase. This behavior confirms the rol e of sulfur configuration in determining the thermotropic properties. Molecular modeling has shown that the sign of the transverse dipole mo ment is directly related to the sulfur configuration. By correlation o f the sign of the spontaneous polarization with the sign of the calcul ated transverse dipole component, it has been possible to deduce sulfu r's absolute configuration for each diastereomer; this appears as a ne w method to determine the absolute configuration of an asymmetric sulf ur in chiral mesogenic molecules leading to ferroelectric liquid cryst als.