THE PREPARATION AND PROPERTIES OF NEUTRAL DIAMIDE IONOPHORES FOR GROUP IIA METAL CATIONS-II

Article abstract of DOI:10.1016/S0040-4020(01)91239-6

The elaboration of a series of neutral ligands featuring vicinal ether and N,N-dialkylacetamido groups is described.Several of these ligands were previously described.The ligands are moderate binders with K_app=1E3-1E5 in methanol of the Group IIA cations for wich they are sensitive.Binding constants by Scatchard method are reported for number of ligands mainly with Ca, Sr, Mn and Ba.The ligands in methylene chloride solution extract these cations via their picrate salts from water.The electrochemical K_ij^pot (selectivity) values for some of the ligands when they are incorporated into liquid membrane electrodes and tested with various cations as determined by Simon et al. (ETH Zurich) are reported.Selectivity ratios of over 100:1 for Na vs Ca were found for several piperidenyl amides of 1,2-phenylenedioxydiacetic acid.Incorporation of N-methylamino instead of ether oxygen groups into the basic structure gives a stronger cation binder which is still selective for Group IIA vs Group IA cations but with binding capacity for transition metal cations also.Limitations of the Scatchard plots for these ligands and the non-correspondance of electrochemical selectivities with the ordering of binding of cations in single liquid phase are discussed.