Theoretical Studies on Lanthanide Cation Extraction by Picolinamides: Ligand–Cation Interactions and Interfacial Behavior

Abstract We report theoretical investigations on the complexation and liquid–liquid extraction of trivalent lanthanide cations by picolinamide ligands L. The relative contributions of pyridine vs. amide moieties of L and the effect of alkyl substituents are investigated in the gas phase by quantum mechanical calculations. The uncomplexed ligands L with different lipophilic substituents and Eu(NO3)3 L 3 complexes are simulated at a water–"oil" interface, where "oil" is modeled by chloroform. The simulations point to the importance of interfacial phenomena in the liquid–liquid extraction of cations by picolinamide ligands and the difference between pyridine vs. amide substituted ligands. Keywords: PicolinamideCation extractionInterfaceChelating ligandsModeling