Ligand design for complexation in aqueous solution. 2. Chelate ring size as a basis for control of size-based selectivity for metal ions

The role of chelate ring size in complex stability, and selectivity based on metal ion size, is examined. Formation constants of pairs of ligands which differ in that one member of the pair forms a five-membered chelate ring where the other forms a six-membered chelate ring are reported with metal ions ranging in ionic radius from small to medium sized