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 bi s(beta-diketonate) complexes (M = Cu, VO, Pd) that exhibit discotic me sophases is reported. This study has determined that the ability of th e metal center to influence the mesophase stability depends upon the d ensity 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-cha in density. The side-chain-induced organization assists the expression of the metal center's character in determining the stability and natu re 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 i s 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 intera ctions produce polymeric (-V=O-V=O-)(n) structures.