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(+center dot), 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.