MESOMORPHIC PROPERTY AND ORIENTATIONAL ORDER IN THE NEMATIC PHASES OF NICKEL(II) AND OXOVANADIUM(IV) COMPLEXES OF N-SALICYLIDENE-N-PROPYLAMINE DERIVATIVES

Homologous series of new metallonematogens, bis[4-((4-alkoxybenzoyl)oxy)-N-n-propylsalicylaldiminato]nickel(II) and -oxovanadium(IV), have been synthesized and their thermotropic mesomorphism has been characterized by thermal analysis. All of the nickel(II) complexes prepared exhibit enantiotropic nematic phases over temperature ranges between 158-230-degrees-C (melting points) and 160-253-degrees-C (clearing points). Corresponding oxovanadium(IV) complexes are also nematogenic, but the thermal stability of the nematic phases is much lower as indicated by their clearing temperatures being depressed by 51-degrees-C on the average. Orientational order or a nickel(II) complex in its nematic phase was investigated by means of H-1 NMR spectroscopy, and the results showed that the species has a more or less normal nematic order. The oxovanadium(IV) congener was dissolved in the nickel(II) nematic host and studied by ESR spectral analysis. The results for this and related oxovanadium(IV) probes have shown that the central chelate cores of these molecules are highly oriented. It has also been revealed by H-1 NMR measurements that the nematogenic nickel(II) complex used in these experiments shows some association phenomenon in solution.