Calix[4]arene and its diphosphorylated derivative have been immobilized onto cross-linked polystyrene beads through an etherification reaction. The supported calixarene complexes 96.7% Cs(I) from a 10-4 N solution in 1 M NaOH. Poly(hydroxystyrene) complexes 35.6% Cs(I) from the same solution. Immobilization of the calixarene onto a polymer support thus does not affect its inherently high affinity for cesium ions. Substituting two of the three remaining hydroxyl groups on the calixarene with diethoxyphosphoryl moieties allows for quantitative complexation of Fe(III) and Pb(II) from 0.01 M nitric acid solutions. The unsubstituted calixarene complexes 6.00% Fe(III) and 7.36% Pb(II) while diethoxyphosphoryl-substituted poly(hydroxystyrene) complexes 10.0% Fe(III) and 3.76% Pb(II). The calixarene therefore acts as a platform on which ligands can be immobilized in close enough proximity to permit cooperative binding of metal ions.

Calixarenes are macrocyclic compounds with four to eight repeat units formed by the condensation of p-alkylated phenols with formaldehyde. Substitution with ion-complexing ligands can allow for the synthesis of a wide array of selective coordinating compounds. Phosphorus-containing ligands have been found to complex a large number of metal ions with selectivity being determined by the precise ligand structure. The coordination chemistry that results when calixarenes are phosphorylated is reviewed to emphasize the unique potential of such molecules for selective metal ion separations and in ion sensor technology. The three sections of this review are (a) transition metal complexes of phosphorylated calixarenes (e.g., phosphino, phosphinite, and phosphine-functionalized calixarenes), (b) application of phosphorylated calixarenes as selective metal ion complexants, and (c) immobilization of calixarenes onto inorganic and organic polymers.

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