CONTROLLING INTERMOLECULAR INTERACTIONS BETWEEN METALLOMESOGENS - SIDE-CHAIN EFFECTS IN DISCOTIC COPPER, PALLADIUM, AND VANADYL BIS(BETA-DIKETONATES)

A systematic study of the liquid-crystalline properties of 30 metal bis(beta-diketonate) complexes (M = Cu, VO, Pd) that exhibit discotic mesophases is reported. This study has determined that the ability of the metal center to influence the mesophase stability depends upon the density of side chains. In the 10-side-chain complexes series 3, all of the materials were found to be liquid crystalline. In this series the M = VO analogues were found to have lower melting and clearing points than those with M = Cu and M = Pd. For the 12-side-chain series 4 the opposite is true, and the M = VO materials have substantially higher clearing points. The differences between series 3 and 4 arise from the enhanced core-core interactions that accompany the increased side-chain density. The side-chain-induced organization assists the expression of the metal center's character in determining the stability and nature of the mesophase. The fact that the transition temperatures of the M = Cu and M = Pd compounds differ more in series 4 than in series 3 is also a manifestation of this greater organization. The influence of the metal centers is discussed in the context of intermolecular dative associations and for some phases of the M = VO materials these interactions produce polymeric (-V=O-V=O-)(n) structures.