DESIGN AND SYNTHESIS OF CALCIUM AND MAGNESIUM IONOPHORES BASED ON DOUBLE ARMED DIAZACROWN ETHER COMPOUNDS AND THEIR APPLICATION TO AN ION-SENSING COMPONENT FOR AN ION-SELECTIVE ELECTRODE

The double-armed diazacrown ethers, which have a base diazacrown ether ring with two diamide-type side chains, were designed and synthesized on the basis of the proposed molecular model for the novel neutral Ca 2+ and Mg2+ ionophores. The potentiometric ion-selective electrodes we re prepared with over 20 kinds of systematically synthesized diazacrow n ether derivatives. The relationship between the molecular structures of the ionophores and the ion selectivities was fully discussed. The electrodes based on the 21- and 18-membered diazacrown ether derivativ es possessing a glycolic diamide and malonic diamide in their side cha ins (K23E1 and K22B5) exhibited excellent Ca2+ and Mg2+ selectivities, respectively. The ion-selectivity features of the novel Ca2+ and Mg2 ionophores supply important structural information about the design o f host molecules for alkaline earth metal cations.