SYNTHESIS AND BINDING STUDIES OF NEUTRAL DIOXYDIAMIDE IONOPHORES III

Article abstract of DOI:10.1016/S0040-4020(01)89075-X

The syntheses of several bis-(1,2-phenylenedioxydiacetamides) with eight binding sites (four ethers, four amides) are described.It had been anticipated that these bis-compounds would be much stronger binders for Group IIA cations than are members of our previously described 1,2-phenylenedioxydiacetamide system, e.g. 1-3, which give isolable complexes usually of 2:1 ligand/metal cation stoichiometry.Binding constants for the new diesters 4 and 5 were determined in methanol using UV absorption changes and the Scatchard method.The binding strength of 4 was concentration dependent and only moderately greater than that for 1 or for the more closely related 4-hydroxymethyl compound 3.Diester 5 was a weaker binder for Group IIA cations than was either 1 or 3.Cooperativity of the two sets of binding sites with either Sr2+ or Ba2+ was demonstrated for 4 but not for 5.Electrochemical selectivity values (K^pot ij) as determined by Simon et al for 4, 5 and 6, in liquid membrane electrodes are reported for various cations.High ion selectivity for Na1+ vs either Ca2+ or K+ were found, especially for 6.