Interactions between ions and free or immobilized ligands. Application of the competition method

Application of a competition method to determine affinities of ligands for ionic species in low polarity media is described. A soluble ligand, L, and a network-immobilized ligand, N, are allowed to interact with the counterion of an ionic chromophore A” according to the reaction NM⁺A⁻ + L → LM⁺A⁻ + N (K). K values were determined in toluene and in ether-type solvents for linear and macrocyclic polyethers and polyamines, as well as for other cation-complexing agents, by varying either N or L. In solvents such as dioxane, binding constants of M⁺A⁻ to N can be determined directly. Combined with K values they yield the complex formation constant, K_L, of the reaction M⁺A⁻ + L → LM+A⁻.