The nature of metal-ligand bonding in the primary hydration shell and in ionophores with alkali metal ions

Abstract

1. 1. Transport of alkali ions in model membranes mediated by ionophores is associated with at least two basic problems: (a) a conceivable physical model for the metal-ligand bonding in the primary hydration shell and (b) migration of ions from the primary hydration shell to ionophores to form ion complexes. 2. 2. The nature of metal-ligand bonding both in the primary hydration shell and in the ionophores has been found to be around 80% ionic and 20% covalent in both cases by independent investigation. Clearly the energetics being equivalent in both systems, ions will not migrate from the former to the latter. 3. 3. A novel model is proposed in terms of hydrogen bonding in the primary hydration shell for Li + and Na + so that the migration of these ions to ionophores is easily envisaged. Hyrogen bonding contributes 18% and 5% of the energy to the total hydration shell energy of Li + and Na +, respectively.