Synthesis of complexes Co, Cu, Ni and Pd supported by “ONNO” type Schiff base ligand and their DNA cleavage, antioxidant effects and antimicrobial studies

A new Schiff base ligand was synthesized from a reaction of 5-benzoyl-4-hydroxy-2-methyl-6-phenyl-2H-pyridazine-3-one and 1,3-diaminopropane. Schiff base metal complexes were synthesized from a reaction of Ni(AcO) 2 × 4H 2 O, Cu(AcO) 2 × H 2 O, Co(AcO) 2 × 4H 2 O, Pd(AcO) 2 metal salts and ligand, respectively.  All compounds were characterized using magnetic susceptibility, elemental analysis, NMR (for ligand), UV-Vis and FT-IR spectroscopic analysis. While octahedral structure has been proposed for Ni(II), Pd(II) and Co(II) complexes, square-planar geometry is suggested for Cu(II) complex. Synthesized compounds were evaluated for their antioxidant effect, DNA cleavage and antimicrobial studies. The DPPH free radical scavenging activity of compounds 1, 2, 3, 4 and 5 on DPPH were found as 38.5%, 32.5%, 36.9%, 35.7% and 45.7% at 200 mg l -1 , respectively.  The compounds 4 and 5 revealed maximum ferrous chelating activity of 64.5% and 78.1% at 200 mg ml -1 , respectively. For all the compounds, DNA cleavage studies showed complete DNA digestion at 100 mg ml -1 . Antimicrobial activities of 3 and 4 complexes against Staphylococcus aureus (ATTC 6538) were determined to be in 12 mm diameter.