NMR-Spektroskopische Untersuchungen der kinetischen Limitierung der Kationenselektivität eines cadmiumselektiven Ionophors

NMR Studies of the Kinetic Limitation of Cation Selectivity of a Cadmium-Selective Ionophore The Cd²⁺-selective ionophore N,N,N′,N′-tetrabutyl-3, 6-dioxaoctanedithioamide (1) looses its capability to induce cation selectivity in solvent polymeric membranes if these are contacted with Cu²⁺, Pd²⁺, Pt²⁺, Ag⁺ and Hg²⁺. For systems with a free energy of activation of the ligand exchange reaction of more than about 65 kJ mol^?1 (in acetonitrile) the cation complexes of the ionophore act as anion exchangers (Pt²⁺, Pd²⁺). Below about 45 kJ mol^?1 cation permselectivity is observed (Zn²⁺, Cd²⁺). Ag⁺ and Hg²⁺ induce a decomposition of the ionophore.