Effect of polyelectrolytes on the rate of ligand–metal-ion reactions. Part 2.—Retardation by polyphosphates of the complexation of cobalt(II) with an azo-dye

Abstract

The effect of long-chain polyphosphates on the rate of complexation of cobalt(II) with pyridine-2-azo-p-dimethylaniline (PADA) is studied using the temperature-jump method. PADA is shown to be a very sensitive probe allowing the study of the specific interactions between Co²⁺ ions and polyphosphates. The retardation effect observed is attributed to the ‘site-binding’ of Co²⁺ ions accompanied by complete dehydration. The results confirm, through a totally different approach, previous conclusions from n.m.r. measurements.