Synthesis, structural characterization and antioxidant activity of some vanadium(IV), Mo(VI)/(IV) and Ru(II) complexes of pyridoxal Schiff base derivatives

Abstract New complexes containing vanadium(IV), Mo(VI)/(IV) and Ru(II) derived from Schiff base of pyridoxal and S-benzyldithiocarbazate (H 2 pysb) or p -toluidine (Hpytol) have been prepared. The structures of the described compounds were elucidated by elemental analyses, spectroscopic techniques (IR, 1 H NMR, UV–Vis and EPR) magnetism, molar conductivity and thermal analysis measurements. Their redox behaviors were also studied by cyclic voltammetry. The ligand H 2 pysb showed coordination to the metal ions in a dibasic tridenate manner through deprotonated phenolate oxygen, azomethine nitrogen and thiolate sulfur, while Hpytol behaved as monobasic bidentate through phenolate oxygen and azomethine nitrogen. The complexes were tested for their antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and the data obtained revealed that the scavenging activity of the complexes towards DPPH is high for the oxovanadium(IV) complexes with lower IC 50 values which are comparable to ascorbic acid as a standard antioxidant. The EC 50 concentration ratio together with other antioxidant parameters are also reported.