Kinetics of oxidation of nickel(II) aza macrocycles by peroxydisulphate in aqueous media

The kinetics of the oxidation of nickel (II) hexaaza and nickel (II) pentaaza macrocycles by the peroxydisulphate anion, S2O8 2–, were studied in aqueous media. Effect of pH on reaction rate was also studied. The rate increases with increase of S2O8 2– concentration. Rates are almost independent of acid between pH 4 and 2, giving overall a relatively simple second-order rate law followed by oxidation within the ion pair solvent shell. Using rate = +1/2 d[Ni(L)3+]/dt = k[Ni(L)2+][S2O8 2–], oxidation rate constants were determined.