Spectral, magnetic and thermal characterization of new Ni(II), Cu(II), Zn(II) and Cd(II) complexes with a bischelate Schiff base

The Schiff base N,N'-bis-(3-methoxy-salicyliden)-o-tolidine (H2L) derived from o-vanillin and 3,3`-dimethylbenzidine has been synthesized and structurally characterized. The crystal structure shows that the planar molecular units are arranged in sheets assembled through hydrogen bonds and pi-pi stacking interactions. New Ni(II), Cu(II), Zn(II), and Cd(II) complexes with H2L were synthesized and characterized by microanalytical, molar conductivities, ESI MS, IR, UV-Vis-NIR, and EPR spectra, magnetic data at room temperature as well as thermal analysis. IR data are in accord with divergent bischelate nature of ligand that coordinates as anion through azomethine nitrogen and phenolic oxygen. The electronic spectra correlated with magnetic susceptibility measurements, and EPR data indicate an octahedral stereochemistry for Ni(II) complex and a tetrahedral one for Cu(II) complex. Processes such as water elimination, thermolyses, and oxidative degradation of Schiff base were evidenced during thermal analysis. All these processes lead to the most stable metallic oxides as final products.