Synthesis of tetra-N-substituted 1,10-dioxa-4,7,13,16-tetraazacyclooctadecanes and their application as lead (II) selective electrodes. X-ray crystalstructure of 4,7,13,16-tetrathenoyl-1,10-dioxa-4,7, 13,16-tetraazacyclooctadecane

Terra-N-substituted 1,10-dioxa-4,7,13,16-tetraazacyclooctadecanes (tetraaza crown ethers) (1-5) have been synthesised. Each compound was incorporated i n a PVC membrane that provided the basis for a lead-selective potentiometri c electrode. The electrode based on the 4,7,13,16-tetrathenoyl-1,l 10-dioxa -4,7,13,1 6-tetraazacyclooctadecane (5) ionophore bearing four thenoyl func tional subunits exhibited excellent lead (II) ion selectivity with only Ag and Hg2+ significantly interfering. The crystal structure of this host (5) has been determined by single crysral X-ray analysis. Crystal data. C32H36 N4O6S4, M 700.9, monoclinic, space group P2(1)/c, a, 10,315(4), b, 13.635(2 ), c, 14.357(6)Angstrom, beta 124.63(2)degrees, V 1661.6(9)Angstrom(3), D-c , 1.40 g cm(-3), Z 2, mu(Cu), 29.90 cm-l. Final residuals R, R, were 0.054, 0.082 for the observed data.