Synthesis and structural characterization studies of cobalt(III), manganese(III) and iron(III) schiff base complexes

Coordination behaviour of the ligands towards trivalent metal ions has been investigated by IR, molar conductance, magnetic moments and electronic spectral measurements. The ligands employed are TAA, PAA, ISA and IDA. The ligands and their metal complexes have been investigated with particular reference to the structure and bonding of the ligand moiety in the metal complexes. All the complexes are intensely coloured and are insoluble in water and methanol and soluble in DMSO. They possess 1:2 metal-ligand stoichiometry and formulation of the complexes has been made on the basis of their analytical data and magnetic susceptibility measurements. Molar conductance values were in the range expected for a 1:1 electrolytic species. The bonding nature of the ligands to the metal ion has been determined by careful comparison of the IR spectra of the complexes and the ligands. All the ligands function as neutral tridentate/bidentate, in all the complexes utilizing the carbonyl oxygen atoms and azomethine nitrogen atoms for coordination. IR spectra together with molar conductance values adequately confirmed the ionic nature of acetate group. The cyclic voltammogram of [Fe(PAA)2Cl2]Cl showed the quasi-reversible reduction nature. The indexing of the X-ray diffraction pattern obtained for the [Fe(TAA)2]Cl3 complex indicated that it has an orthorhombic crystal lattice. The Schiff base ligands and their metal complexes were tested against four pathogenic bacteria (Staphylococcus aureus, Bacillus substilis) as Gram-positive bacteria, and (Escherichia coli, Klebsiella pneumonia) as Gram-negative bacteria. All the metal complexes exhibit higher antibacterial activity than the free ligand. Iron(III) complexes have higher bacterial activity than the other complexes.