Synthesis and Extractive Properties of Hexaphosphorylated Calix[6]arenes

A series of calix6]arenes substituted with phosphoryl functional groups were prepared by the Arbuzov reaction of hexakis(chloromethyl)calix6]arene hexamethyl ether with isopropyl esters of trivalent phosphorus acids, followed by appropriate chemical transformations. Molecular modeling and NMR data show that phosphorylated calix6]arenes exist in the stereochemically labile 1,2-alternate conformation. The extractive power of these compounds with respect to americium and europium was studied. Due to the cooperative binding of the metal cation with phosphoryl groups, the phosphorylated calixarenes are more effective extractants than their acylcic analogs and commercial organophosphorus extractants.