A series of metal bridged biferrocene trinuclear complexes derived from Schiff base ligand, S-benzyl-N-(ferrocenyl-1-methylmethylidene) dithio carbazate (here after abbreviated as HL) have been synthesized and spectroscopically characterized. Single crystal structure analysis for the nickel complex, NiL~2, palladium complex, PdL~2 and copper complex, CuL~2 revealed that the Schiff base ligand acted as a singly negtively charged bidentate and coordinated to the metal atom via the mercapto sulphur and β-nitrogen atoms. The coordination geometry of nickel atom and the palladium atom is close to square planar configuration forming an extensive electron delocalization system. The two ligands coordinated to the metal atom in a novel cis- configuration with the two ferrocene moieties on the same side. Detailed structure analysis show that the novel cis-configuration is stabilized by the intramolecular π-π stack interaction between the two acetylcyclopantadienyl rings. The coordination geometry of copper atom in CuL~2 is closed to tetrahedral 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. The results also show that the complexes NiL~2, PdL~2 exhibit higher third-order nonlinear response.

Key words: FERROCENE, NON LINEAR OPTICS, CRYSTAL STRUCTURE, COPPER COMPLEX