Effect of polyelectrolytes on the rate of ligand–metal-ion reactions. Part 1.—‘Catalysis’ of the complexation of Nickel(II) with an azo-dye

Abstract

The effect of different anionic polyelectrolytes on the rate of complexation of Nickel(II) with the bidentate ligand pyridine-2-azo-p-dimethylaniline (PADA) is studied using the stopped-flow technique. The ‘catalytic’ effects observed are dependent on the structure of the polyelectrolyte considered: two anionic polyelectrolytes characterized by the same linear charge density, but chemically different, will either inhibit (polyphosphate) or accelerate [poly(styrene sulphonate)] the complexation reaction. Intermediary situations are observed with alternated copolymers of maleic acid and with carboxymethylcelluloses. The results are consistent with Manning's polyelectrolyte theory, but give additional knowledge of the specific interactions occurring between counterions and polylelectrolyte charged sites.