SYNTHESIS AND PHYSICOCHEMICAL STUDIES ON TRANSITION-METAL COMPLEXES OF SYMMETRICAL BIS-SCHIFF BASE LIGANDS

A new series of symmetric bis-Schiff bases derived from 1,2-diaminoethane with bis-salicylaldehyde (H2L1) and/or bis-o-hydroxyacetophenone (H2L2) have been prepared. The metal(II) complexes of these ligands were isolated and characterized by elemental analyses, magnetic moments and spectral (visible, i.r.) measurements. I.r. spectra show that the ligands behave as dianionic or neutral tetradentate. Replacing the imine C-H with a bulky methyl group leads to a steric interaction with the methylene protons of the chelate ring. The (NiL2) is diamagnetic four coordinate square planer. The electronic spectrum shows that [Cu2(H2L1)Cl4(OH2)4] complex is tetragonally distorted octahedral. The polarographic reduction of Schiff bases was investigated in Britton-Robinson buffer solutions at pH 3-12. The polarograms at dme indicated that depolarizers, (H2L1 & H2L2) are reduced through 8-electron irreversible diffusion-controlled wave. The mechanistic pathway of the electrode reaction is discussed.