Chiral Biphenylacetylene Smectic Liquid Crystals

Standard Sonogashira coupling afforded rod-like, phenylacetylene extended biphenyl mesogens substituted with different chiral alkoxy chains, starting from commercially available 4-(4'-bromophenyl)phenol. Depending on the position of the chiral center and the polar nature of the target molecules as determined by the electron withdrawing end-groups, different types of smectic liquid crystals are formed. The liquid crystal phases are fully characterized by polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction. In two cases, the molecular chirality is transferred to the supramolecular assembly, which is proved by circular dichroism measurements in the chiral mesophase.