Rigid chiral building blocks for copper(II)- and palladium(II)-containing liquid crystals

The possibility of metal coordination in oxazolinyl phenols has allowed the preparation of new chiral metal-containing liquid crystals in which the st ereogenic center is located in the rigid mesogenic core. By using (S)-beta -amino alcohols as chiral starting materials for the synthesis of the oxazo line ligands, two types of complex have been prepared: (i) mononuclear copp er(II) complexes and (ii) dinuclear orthopalladated organometallic compound s with either nonplanar (acetato-bridged) or planar (chloro-bridged) geomet ries. The synthesis and structural characterization of all of these compoun ds are described. The formation of a single diastereoisomer with a trans co nfiguration in nonplanar palladium(H) complexes has been confirmed by H-1 N MR, spectroscopy. The complexes mainly show SA mesomorphism, although when they are used as chiral dopants in a matrix with the phase sequence N-S-A-S -C they induce a cholesteric mesophase. The presence of stereogenic centers lying out of the coordination plane in a rigid environment must account fo r the formation of the helical cholesteric mesophase over broad temperature ranges.