Voltage-controlled fluorometry of the transfer of nonfluorescent ions across the 1,2-dichloroethane/water interface using fluorescent ionophores

The voltage-driven transfer of alkali and alkaline-earth metal ions across the polarized 1,2-dichlorocthane (DCE)/water interface has been measured fluorometrically by using two fluorescent ionophares, coumarin 153-linked monoaza-15-crown-5 (C153-crown(O(4))) and two-coumarin 153-linked diaza-18-crown-6 ((C153)(2)-K(22)), The 1:1 complex formation prevails for both monovalent and divalent ion transfer, when the concentration of C153-crown(O(4)) in DCE is at the micromolar level. In the Mg(2+) ion transfer, the formation of the 1:2 (metal-ligand) complex becomes significant at the millimolar level of C153-crown(O(4)). C153-crown(O(4)) seems to adsorb at the interface. The complexation of Ba(2+) with (C153)2-K(22) is significantly slower than the complexation with C153-crown(O(4)).