Lanthanide containing Schiffʹs base complexes with chloride counter-ions: mesomorphic properties

Liquid crystalline lanthanide complexes (metallomesogens) with chloride counter-ions have been synthesized. The complexes have the stoichiometry [Ln(LH)3Cl3], where Ln is a trivalent rare-earth ion (Y, Pr, Sm, Eu–Lu), and LH is the ligand N-octadecyl-4-octyloxysalicylaldimine. Although the Schiffʹs base ligands do not exhibit mesomorphism, the complexes do (SmA phase). The mesomorphic behaviour of these compounds has been investigated by hot-stage polarized microscopy, differential scanning calorimetry (DSC) and high temperature X-ray diffraction measurements. The stoichiometry of the complexes remains constant throughout the lanthanide series. The complexes have rather high transition temperatures.