Calix[6]arene-Picolinamide Extractants for Radioactive Waste Treatment: Effect of Additional Carboxy Binding Sites in the Pyridine 6-Positions on Complexation, Extraction Efficiency and An/Ln Separation
of the pyridine nuclei of calixarene-based picolinamide ligands on the extraction and complexation properties of lanthanide(III) and actinide(III) metal ions was studied. For this purpose, six new ligands 1–6 were synthesized; their conformational properties were studied both in solution and in the solid state, and their binding properties towards lanthanide (LnIII) and actinide (AnIII) metal ions were