Mesogenic palladium and platinum-diiodide complexes of 4-isocyanobenzylidene-4-alkoxyphenylimines

A series of 4-isocyanobenzylidene-4-alkoxyphenylimines 4-CN-3,5-R₂C₆H₂CHNC₆H ₄-4-OC_nH_2n+1 (R = Me, Prⁱ), were prepared from 4-isocyanobenzaldehydes and long-chain 4-alkoxyanilines. The palladium and platinum-diiodide complexes of the methyl-substituted ligands, MI₂(4-CN-3,5-Me₂C₆H₂CHNC ₆H₄-4-OC_nH_2n+1)₂ exhibit mesomorphic behaviour, forming nematic and smectic C phases (for n > 10). The metal centers apparently serve as rigid linear links between the isocyanide ligands, but have little additional influence on the liquid crystal properties, as evidenced by the small differences in transition temperatures between the palladium and platinum compounds. The corresponding complexes with lateral isopropyl substituents (R = Prⁱ) do not exhibit mesomorphic properties.