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A methoxy-substituted tripodal hydroxylamine ligand, H3TriNOxOMe, was synthesized and coordinated to rare earth cations for separation purposes. Metrics of the resulting complexes were investigated and compared with their parent TriNOx3− counterparts for determination of the molecular basis for the described rare earth separation system. Addition of an electron donating group to the aryl backbone resulted in a more electron rich ligand that increased the equilbrium constant for complex dimerization five-fold. The new separation system yielded efficient Nd/Dy separations in toluene rather than benzene. [ABSTRACT FROM AUTHOR]

Purification of rare earth elements is challenging due to their chemical similarities. All of the deployed separation methods rely on thermodynamic properties, such as distribution equilibria in solvent extraction. Rare-earth-metal separations based on kinetic differences have not been examined. Herein, we demonstrate a new approach for rare-earth-element separations by exploiting differences in the oxidation rates within a series of rare earth compounds containing the redox-active ligand [{2-( tBuN(O))C6H4CH2}3N]3−. Using this method, a single-step separation factor up to 261 was obtained for the separation of a 50:50 yttrium-lutetium mixture. [ABSTRACT FROM AUTHOR]

Rare earth (RE) metals are critical components of electronic materials and permanent magnets. Recycling of consumer materials is a promising new source of rare REs. To incentivize recycling, there is a clear need for the development of simple methods for targeted separations of mixtures of RE metal salts. Metal complexes of a tripodal hydroxylaminato ligand, TriNOx3-, featured a size-sensitive aperture formed of its three η²-(N,O) ligand arms. Exposure of cations in the aperture induced a self-associative equilibrium comprising RE(TriNOx)THF and [RE(TriNOx)]2 species. Differences in the equilibrium constants Kdimer for early and late metals enabled simple separations through leaching. Separations were performed on RE1/RE2 mixtures, where RE1 = La-Sm and RE2 = Gd-Lu, with emphasis on Eu/Y separations for potential applications in the recycling of phosphor waste from compact fluorescent light bulbs. Using the leaching method, separations factors approaching 2,000 were obtained for early-late RE combinations. Following solvent optimization, >95% pure samples of Eu were obtained with a 67% recovery for the technologically relevant Eu/Y separation. [ABSTRACT FROM AUTHOR]