Modification of calix[4]arenes with CMPO-functions at the wide rim. Synthesis, solution behavior, and separation of actinides from lanthanides

摘要

Two calix[4]arene tetraethers (Y = C_5H_(11), C_(14)H_(29)) bearing on their wide rim four-N(Me)-CO-CH_2-P(O)Ph_2 residues were synthesized for the first time. Their ability to extract lanthanides and actinides from an acidic aqueous phase to organic phases (CH_2Cl_2, NPHE) was studied. In comparison tot he corresponding -NH-analogs, they are less efficient extractants, the selectivity for the light over the heavy lanthanides is less pronounced, while there is still an interesting selectivity of Am~(3+) over Eu~(3+). Stability constants for selected lanthanide salts were determined also in homogenous phase (methanol, acetonitrile) but do not account for the different extraction results. The complexation of Gd~(3+) was also followed by relaxivity (NMRD) measurements, which suggest an even stronger aggregation for the N-methyl compound while the 1:1 complex is reached for a smaller ratio [L]/[Gd~(3+)] compared to the NH analog. The formation of aggregates is also supported by dynamic light scattering measurements. A single crystal X-ray structure of the pentyl ether reveals a C_2-symmetrical pinched cone conformation for the free ligand.