EXTRACTIVE PROPERTIES TOWARDS RARE-EARTH-METAL IONS OF CALIX[4]ARENESSUBSTITUTED AT THE NARROW RIM BY PHOSPHORYL AND AMIDE GROUPS

The extractive properties of the cone and partial-cone isomers of 5,11 ,17,23-tetra-tert-butyl-25, arbamoylmethoxy)-26,28-bis(diphenylphosphi noylmeth oxy)calix[4]arene (cone-1 acid partial-cone-1) in 1,2-dichlor oethane towards rare-earth metal ions in nitrate media at 25 degrees C were investigated. The analysis of the extraction equilibrium obtaine d from a mixture of four rare-earths (La, Eu, Er and Y) revealed that the extracted species have a 1 : 1 metal/ligand ratio for both ligands . The intra-group separation efficiencies of the ligands have been eva luated in a competitive extraction process of 11 rare-earth metal ions (La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Yb and Y). Significantly higher extractive properties were found for cone-1 with respect to partial-co ne-1, suggesting the crucial role of the phosphoryl groups in the comp lexation of the rare-earth ions. These findings were corroborated by e xtraction studies with other narrow-rim-substituted cone-calix[Lt]aren es containing two (2), three (3 and 4) and four (5) phosphoryl groups. Comparison of the extractive properties of the amide containing calix arenes with those of diphenyl-N,N-dimethylcarbamoylphosphine oxide (D phi DMCMPO) are also presented and discussed.