Oxovanadium(IV) complexes containing tetradentate N₂O₂-type ligands: synthesis, crystal structure, antioxidant activity, and spectroscopic characterization

Two coordination complexes were synthesized using vanadyl(IV) acetylacetonate and H₂denm/H₄dpim in MeOH/CHCl₃ and characterized. The complexes were [VO(denm)(H₂O)]·CH₃OH (1) and [VO(H₂dpim)(CH₃COONa)]·CH₃OH (2) (H₂denm = 2,2′-[[(1R,2R)-1,2-diphenyl-1,2-ethanediyl]bis[(E)-nitrilomethylidyne]]bis[6-methoxyphenol]; H₄dpim = [(2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(6-methoxyphenol)]. The vanadyl(IV) species of 1 and 2 exhibited distorted octahedral geometries with two N and two O atoms of each ligand and aqua/acetate ligand. Complex 1 did not exhibit emissions in the solid and solution states, whereas complex 2 exhibited strong band maxima in the solid state and a dimethyl sulfoxide solution. The magnetic properties and electron paramagnetic resonance spectra of 1 and 2 revealed that they were S = 1/2 spin systems. The antioxidant activity of 2 was higher than those of 1 and ascorbic acid.