MESOMORPHIC 4'-FUNCTIONALIZED 6'-PHENYL-2,2'-BIPYRIDINES - TRIDENTATELIGANDS FOR ORGANOPALLADIUM MESOGENS

A novel series of 6'-phenyl-2,2'-bipyridines (HL-n) substituted in the 4' position with promesogenic functional groups has been prepared. Th e materials are strongly luminescent and display nematic mesomorphism. The HL-n behave as C,N,N-tridentate, cyclometallating ligands leading to [Pd(L-n)Cl] derivatives. Metal co-ordination promotes a considerab le stabilization of the crystal phase, forcing mesophases to become me tastable. All [Pd(L-n)Cl] species indeed exhibit a monotropic mesophas e either nematic or smectic A in character depending on the chain leng th of the substituents on the central pyridine unit.