STRUCTURAL ION SELECTIVITY OF THIA CROWN-ETHER COMPOUNDS WITH A BULKYBLOCK SUBUNIT AND THEIR APPLICATION AS AN ION-SENSING COMPONENT FOR AN ION-SELECTIVE ELECTRODE

Several 14-membered thia crown ether ionophores having a bulky block s ubunit were synthesized, and their chemical structures and ion selecti vities were examined in detail when these compounds were used as an io n-sensing component of an ion-selective electrode, The ionophores of b oth cyclic and noncyclic thia ethers exhibited a high selectivity for silver ion (Ag+), in which the sulfur atom in the ionophore molecule p lays a role as the effective coordination donor site for the silver io n, The best Ag+-selective electrode was prepared with the 14-membered thia crown ether having one sulfur atom, three oxygen atoms, and a bul ky pinan subunit. The ion selectivity of this electrode for Ag+ was ov er 10(4) times that for other metal cations. In the case where the sul fide in the thia ether ionophore was changed to sulfoxide by oxidation , ion selectivity for mercury ion became higher; therefore, the sulfox ide was found to be an effective coordination site for the mercury ion , The ion selectivity features of noncyclic sulfide, sulfoxide, and su lfone were also examined and compared with the results of the cyclic a nd noncyclic thia ethers.