Synthesis, electrochemical and antimicrobial studies of mono and binuclear iron(III) and oxovanadium(IV) complexes of [ONO] donor tridentate Schiff-base ligands

Tridentate Schiff bases (H2L1 or H2L2) were derived from condensation of acetylacetone and 2-aminophenol or 2-aminobenzoic acid. Binuclear square pyramidal complexes of the type [M2(L1)2] center dot nH2O (M = Fe-Cl, n = 0; M = VO, n = 1) were accessed from interaction of H2L1 with anhydrous FeCl3 and VOSO4 center dot 5H2O, respectively. A similar reaction with H2L2, however, produced mononuclear complexes [ML2(H2O)x] center dot nH2O (M=Fe-Cl, x = 0, n = 0; M=VO, x = 1, n = 1). The compounds were characterized using elemental analysis, FT-IR, UV-Vis, and NMR (for ligand only), and mass spectroscopies and solution electrical conductivity studies. Magnetic susceptibility measurements suggest antiferromagnetic exchange in binuclear Fe(III) and VO(IV) complexes. Thermo gravimetric analysis (TGA) provided unambiguous evidence for the presence of coordinated as well as lattice water in [VOL2(H2O)] center dot H2O. Cyclic voltammetric studies showed well-defined redox processes corresponding to Fe(III)/Fe(II) and VO(V)/VO(IV). Invitro antimicrobial activities of the compounds were investigated against Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeroginosa, Escherichia coli, Bacillus subtilis, and Proteus vulgaris. H2L1 and its binuclear complexes exhibited pronounced activity against all the microorganisms tested.