Synthesis of Calix[4]arene ligands with multiple proton-ionizable groups for complexation of multivalent metal ions
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Abstract
A series of new conformationally mobile tri-ionizable calix[4]arenes has been prepared for the complexation of trivalent lanthanide ions by matching the metal ion charge (3+) with the same number of proton-ionizable groups. The A-(X)sulfonyI carboxamide group, -C(0)NHS02X, was chosen as the proton-ionizable function because its acidity may be tuned by variation of X.
Three series of new di-ionizable calix[4]arene-l,3-crown-5 ethers have been prepared in the cone, 1,3-aItemate and partial cone conformations to probe the influence of conformation, acidity variations and the crown ether ring size in solvent extraction of metal ions. A dansyl fluorescent group was coupled to di-ionizable calix[4]arene-l,3- crown-5 to produce potential fluorogenic ligands.