DISCOTIC METALLOMESOGENS - EFFECTS OF SIDE-CHAINS DENSITY IN TRANSITION-METAL BIS(BETA-DIKETONATE) COMPLEXES

The preparation and mesogenic properties of a series of discotic beta- diketonate metal complexes are reported. The results show that the den sity of side chains, positions of side chains, and the geometries of t he metal centers play important roles in determining the mesomorphic b ehaviors and thermodynamic stability of these complexes. In the series of copper complexes 3, all these disc-like molecules with eight alkox y side chains exhibit columnar hexagonal disordered (D-bd) mesophases. In the series of copper complexes 2 with six side chains, only compou nds substituted with longer alkoxy chains (n = C-14 or C-16) exhibit d iscotic columnar mesophase. However, in the series of complexes 1, onl y crystal-to-isotropic transitions were observed. The results showed t hat induction of liquid crystallinity not only depends on the numbers of side chains (i.e. side chain density), but also on the degree of di stribution over the central core. Palladium complexes analogs exhibit similar discotic mesophases, and due to their greater core-core organi zation, they also have higher clearing points and wider temperature ra nge of mesophases than copper complexes.