Peroxidase-like activity of an azamacrocyclic Ni(II) complex

Peroxidase-like activity of an azamacrocyclic Ni(II) complex, [Ni(II)(DMDAC)]²⁺ (DMDAC = 1,8-dimethyl-1,3,6,8,10,13-hexaaza-cyclotetradecane = 1,8-dimethyl diazacyclam), was investigated by observing the oxidation of 2,2′-azinobis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) in the presence of H₂O₂. UV/Vis and electron paramagnetic resonance spectral changes obtained from the mixture solution of [Ni(II)(DMDAC)](ClO₄)₂, ABTS, and H₂O₂ indicated that both ABTS and its oxidized form, ABTS^+•, were the substrates of the peroxidase-like activity of [Ni(II)(DMDAC)]²⁺. Current work and previously reported experimental and theoretical works on the peroxidase-like activity of azamacrocyclic Ni(II) complexes suggest that these kind of macrocyclic Ni(II) complexes can generally exhibit peroxidase-like activity in aqueous solution and the catalytic cycle proceeds through the heterolytic cleavage of the O–OH bond in a Ni(II)-hydroperoxo species.