Hexacatenar liquid-crystalline complexes of palladium(ii) and platinum(ii) based on trialkoxystilbazole esters

Abstract

The synthesis and characterisation of 4-(3′,4′,5′-trialkoxybenzoyloxy)pyridines (1a–e), and of their corresponding palladium(II), (2a–e), and platinum(II), (3a–e), complexes are described. The pyridine-based ligands are not mesomorphic, but upon complexation to PdCl₂ or PtCl₂, new hexacatenar mesogens are formed which show exclusively the hexagonal columnar mesophase. The mesomorphic behaviour of the complexes was characterised by polarised optical microscopy, differential scanning calorimetry and X-ray diffraction. The metal seems to influence the crystal phase and mesophase stability as well as the mesomorphic temperature range.