Novel phosphorylated calixarenes for the recognition of f-elements

The binding properties of three series of phosphorylated calixarene derivatives bearing phosphine oxide or phosphonate groups either at the wide or the narrow rims have been investigated towards some representative lanthanide and actinide ions using several approaches: (i) liquid–liquid extraction of europium, americium, thorium and uranyl ions from nitric acid solutions into the two diluents m-nitrobenzotrifluoride (m-NBTF) or dichloromethane; (ii) complexation in single media (methanol and acetonitrile) followed by UV-spectrophotometric and isoperibolic (micro)calorimetric titrations (ITC). The latter technique was found to be very useful for the determination of the stoichiometries of the complexes formed, in particular when the complexation did not induce significant spectral changes. It also provided a full thermodynamic characterization of these new systems. The influence of some structural features of the ligands as the nature of the substituents and the condensation degree of the calixarene moiety, on the distribution coefficients and on the complexation thermodynamic parameters has been established.