Synthesis and Characterisation of Binuclear Cu(II), Ni(II) and Co(II) Chelates with Tetradentate Schiff Base Ligands Derived from 1,5-Diaminonaphthalene

A new series of copper(II), nickel(II) and cobalt(II) chelates containing the binucleating tetradentate Schiff base ligands N,N′-bis(salicylidene)-1,5-diaminonaphthalene (H2L), N,N′-bis(3-methoxysalicylidene)-1,5-diaminonaphthalene (H2L′) and N,N′-bis(4-hydroxysalicylidene)-1,5-diaminonaphthalene (H2L) have been synthesized. These compounds have been characterized by elemental analyses, conductivity measurements, magnetic susceptibility, thermoanalyses (TG-DTA), infrared and electronic spectral data. The results suggest that the Schiff bases function as tetradentate ligands coordinating through the ONNO donor system and indicate a binuclear structure for the Cu(II) complexes with pseudo-tetrahedral geometry and binuclear structures for the Co(II) and Ni(II) complexes with pseudo-octahedral geometry. All complexes are non-electrolytes.