Ligand-catalysed metal ion reduction. Voltammetric determination of rate and formation constants for the nickel complex with 6-mercaptopurine-9-D-riboside

The catalytic reduction of nickel ions on the hanging mercury drop el ectrode in the presence of traces of 6-mercaptopurine-9-D-riboside (M PR) was investigated by linear scan voltammetry in the physiological pH range. A nickel complex is reduced at potentials more positive th an the reduction of the hydrated ion. The reduction of the complex pr oduces a voltammetric pattern which is typical for the electrode proc esses controlled by a parallel chemical reaction. The theoretical tre atment for the regeneration of the reactant by a redox reaction was a dapted to the investigated electrode process.The kinetic equation thu s derived was used for the determination of both the rate (k(1) = 3.1 1 x 10(6) mol(-1) dm(3) s(-1)) and formation (log beta(1) = 3.40) con stants for the reducible complex by means of a multiparametric curve fitting approach.