Synthesis, characterization and antimicrobial studies of o-phenylenediamine Schiff base, Ni(II), Cu(II), Zn(II) complexes and Cu(II) adduct

Abstract

The Schiff base ligand, N, N?-bis(salicylidene)-1,2-phenylenediamine (H2PSA), was derived by the reaction of o-phenylenediamine and salicylaldehyde under reflux. Ni(II), Cu(II) and Zn(II) complexes of H2PSA were also obtained. The Cu(II) adduct was derived by the equimolar addition of 1,10-phenanthroline to the precipitated Cu(II) complex. H2PSA was characterized by melting point, 1H and 13C NMR, infrared and UV/Vis spectroscopies; and the metal compounds by magnetic susceptibility measurements, percentage metal and elemental analyses. Percentage metal and elemental analysis showed the stoichiometry of the complexes as [Ni(PSA)], [Cu(PSA).H2O], [Zn(H2PSA)(SO4)].ZnSO4, and the copper(II) adduct as [Cu(PSA)(Phen)]. The infrared (IR) spectrum of the ligand showed the bands due to ?(C=N) and ?(C–O) at 1613 cm–1 and 1316 cm–1 respectively. These bands were shifted in the IR spectra of the metal complexes to 1616-1607 cm–1 and 1340-1324 cm–1 respectively, indicating the participation of imine nitrogen and phenolic oxygen in the chelate formation. Both nickel(II) and zinc(II) complexes were diamagnetic with magnetic moments of zero while the copper(II) complex and adduct had magnetic moments of 1.70 and 2.20 B.M respectively. The electronic spectra of nickel(II) and Cu(II) complexes demonstrated band absorptions between 450 nm and 490 nm, which were assigned to transitions in the square planar geometry.
The antimicrobial activity of the compounds against four bacterial and two fungal strains showed moderate activity at inhibition diameters of 14–18 mm.