Structural Characterization and Antibacterial, Antifungal, Antioxidant Activity of ONO Salicyl Based Schiff Base and its VO(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Pd(II) and Hg(II) Complexes

An ONO tridentate Schiff base derived from 3,5-dichlorosalicylaldehyde and 2-amino-4-methylphenol (H2L) and its complexes with VO(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Pd(II) and Hg(II) were synthesized and characterized. The structures of the complexes were confirmed by means of elemental analysis, molar conductivity, magnetic moment, UV-visible, fluorescence, FT-IR and NMR spectroscopy. The M:L ratio is 1:2 in Fe(III) and Co(II) complexes whereas 1:1 in the other complexes. It was observed that the Pd(II) complex is 1:1 ionic while the others are non-ionic according to molar conductivity measurements. H2L showed weak fluorescence at different wavelengths in neutral, acidic and basic areas and in the form of some metal complexes. The VO(II) and Cu(II) complexes increased the fluorescence effect compared to the ligand, while the Fe(III) complex completely quenched it. Antibacterial and antifungal activity of the compounds was evaluated against six bacteria and three fungi. In general, all the compounds showed moderate antimicrobial activity. It was observed that some of the complexes exhibited higher activity towards S. epidermidis and S. aureus compared to the ligand. Antioxidant activity of the compounds was investigated in terms of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH•) scavenging and Cupric Reducing Antioxidant Capacity (CUPRAC) methods. It was found that Zn(II) and Pd(II) complexes showed higher antioxidant activity than the ligand and the other complexes.