Synthesis, Characterization and Antimicrobial Activities of Bis-2-Hydroxybenzylidene-N, N′-Ethylenediamine and its Cd(II), Co(II) and Cr(III) Complexes

Three Schiff base complexes [CdL2] (1), [CrL2]Cl(2) and [CoL2] (3) with L= bis-2-hydroxybenzylidene-N, N′-ethylenediamine were synthesized by microwave assisted technique and analysed by melting point determination, solubility, molar conductivity, magnetic susceptibility, UV-Vis and IR spectroscopy. All solvent-bound analyses were conducted in DMSO. Molar conductivity measurements showed that complex 1 and 3 are non-electrolytic while 2 were found to be electrolytic with their composition corresponding to a metal-ligand ratio of 1:2 with respect to the Schiff base ligand. The IR spectra showed that the Schiff base ligands acted in bidentate fashion to the metal centres with coordination involving the azomethine nitrogen atoms and the methanolic oxygen atom of the Schiff base. Electronic spectra and magnetic susceptibility measurements suggested a six-coordinate local symmetry around the metal ions in an octahedral geometry. Magnetic susceptibility studies also revealed that the complexes of Cr(III) and Co(II) are paramagnetic while that of Cd(II) was diamagnetic ([CdL2] = 0.00 BM, [CrL2]Cl = 3.92 BM and [CoL2] = 4.91 BM). The result also suggested the Schiff base ligands to be weak field ligands as they formed high spin complexes with the Co(II) ion. The obtained structural data thus allows for the proposition of an octahedral structural arrangement for the studied metal complexes. The antimicrobial studies indicated that the Schiff base ligands are only weakly active against the studied bacteria but inactive against the studied fungi. In contrast to the free ligands, the metal complexes of this ligand significantly increased or induced antimicrobial sensitivity against the studied microbial strains. Thus, the Schiff base complexes hold promise as powerful and all-around antibacterial agents.