Pyridine-2,6-Dicarboxylic Acid Esters as Novel Ligands for Metal Extraction and Sensing

N,O-hybrid donor ligands are promising compounds for the isolation and separation of actinides and lanthanides from process solutions of spent nuclear fuel reprocessing. Newly synthesized N,O-hybrid donor ligands – derivatives of 2,6-pyridinedicarboxylic acid were studied as extractants and membrane components for potentiometric sensors. The extraction ability of solutions of these compounds in meta-nitrobenzotrifluoride towards d- and f-elements from nitric and perchloric acid solutions was investigated. It was shown that the replacement of amide groups with ester groups reduces the extraction ability of the ligands. Switching from nitric acid to perchloric acid gives a dramatic increase in extraction capacity due to the perchlorate effect. Also, a significant increase in extraction capacity is observed when chlorinated cobalt dicarbolide is added to the organic phase: the highest distribution coefficient is observed at a 1 : 1 ratio of extractant and additive concentrations. Potentiometric membrane sensors based on the new ligands showed significant sensitivity to Cd²⁺. Correlations between extraction and sensing behavior of new ligands were studied.