Structure and third-order optical property - Studies on metal bridged biferrocene complexes

A series of metal bridged biferrocene trinuclear complexes derived from Sch iff base ligand, S - benzyl - N - (ferrocenyl - 1 - methylmethylidene) dith io carbazate (here after abbreviated as HL) have been synthesized and spect roscopically; characterized. Single crystal structure analysis for the nick el complex, NiL2, palladium complex, PdL2 and copper complex, CuL2 revealed that the Schiff base ligand acted as a singly negtively charged bidentate and coordinated to the metal atom via the mercapto sulphur and beta - nitro gen atoms. The coordination geometry of nickel atom and the palladium atom is close to square planar configuration forming an extensive electron deloc alization system. The two ligands coordinated to the metal atom in a novel cis - configuration with the two ferrocene moieties on the same side. Detai led structure analysis show that the novel cis - configuration is stabilize d by the intramolecular pi - pi stack interaction between the two acetylcyc lopantadienyl ring;. The coordination geometry of copper atom in CuL2 is cl osed to tetrahedral configuration, The electrochemical measurements of the three complexes suggest that square planar configuration of the Ni(II) and Pd(II) moieties can effectively transmit the redox effects of the ferrocene moieties, while the tetrahedral configuration of Cu(II) complex cannot. Th e results also show that the complexes NiL2, PdL2 exhibit higher third - or der nonlinear response.