Estimation of association constants of macrocyclic ethers by potentiometry. Part V. Na+ binding in dioxane/water (80/20)

Abstract

The various association constants, beta(nm) and K-nm, of NaCl and NaClO4 with [12]crown-4, [15]crown-5, [18]crown-6, benzo[15]crown-5, benzo[12]crown-4, dibenzo[18]crown-6 and dinaphtho[18]crown-6 have been estimated in a mixture of dioxane/water (80/20) using a sodium ion selective electrode (ISE). The constants have been estimated using 1/(K-nm[L-o](n+m-)) = (1 - nP')(n) X (1 - mP')(m)/P', where P', the mole fraction of complexed Na+ in the presence of identical cation/ligand concentrations, is obtained for different aggregation dissociation possibilities. The association constants of the complexes are reported and discussed in terms of the multiple composition due to strong dioxane/water binding. The binding mechanism is shown to depend on the free cation and counter ion that are formed by different ratio macrocycle-metal complexes in dioxane/water (80/20) solutions.