Coordination and Redox Chemistries of the Rare Earths Within Redox Active Nitroxide Ligand Frameworks

The rare earth elements, La–Lu, Sc and Y, are vital components of many technologies. Production processes of these ions, however, involve inefficient and costly separations steps that are associated with large amounts of waste. This work develops the coordination and redox chemistries of the rare earth ions within nitroxide ligand frameworks with particular emphasis on improving the current state of separations. The synthesis and characterization of a family of N-tert-butyl-N-2-pyridyl hydroxylamines are described. These were used as ligands and oxidants towards cerium and a series of highly stabilized CeIV complexes were formed. These established the basis of a ligand field series for the 4f-block using combinations of solution electrochemistry and DFT techniques. Modification of the pyridyl nitroxide system led to the development of a tripodal nitroxide ligand, whose coordination chemistry to the rare earth ions was exploited for early/late rare earth separations. The redox chemistry of the rare earth ions within this tripodal nitroxide ligand environment was also explored. The techniques established with these projects were applied to the understanding of the newly discovered biological role of the rare earths for methanol dehydrogenase reactivity.