Synthesis of mononuclear metal complexes with some tetradentate Schiff base ligands

A series of Cu(II), Ni(II) and Co(II) complexes with N,N'-bis-[5-X-salicylidene]-2,2'-diamirtodibenzyl [H-2-XSalDDB (X= H, CH3, Br)] have been prepared. The metal complexes were characterized an the basis of elemental analyses, electrical conductance, magnetic susceptibility, spectral and thermal studies. Ail of the complexes are non-electrolytes of 1:1 (M:L) stoichiometry. The room temperature magnetic susceptibility and electronic spectral data support a pseudo-tetrahedral geometry for the complexes. The IR spectra show that the Schiff bases function as tetradentate ligands coordinating through the ON-NO donor system. Substitution on the phenyl ring of the complexes produces a shift in the azomethine nu(C=N) stretching vibrational frequency which is related to Hammett's substituent parameter a. The H-1 NMR data reveal that all Schiff bases exist in the enol-iminic form. Various ESR parameters for the copper complexes have been calculated. The thermal curves of the chelates are single-stepped and indicate the absence of water molecules.