Non-Aqueous Electrochemical Studies of Lanthanide and Actiniide Complexes

In the 2018 Nuclear Posture Review, it has been emphasized that the continued production of nuclear materials is and will continue to be an essential part of American interest and policy. Necessarily, the cleanup and environmental management of excess nuclear waste, especially from the Cold War era, also continues to be an ongoing effort. For example, just the disposition of legacy plutonium, amounting to 34 MT, is not scheduled to be complete for several decades. The electrochemistry of lanthanide and actinide ligand complexes has been studied to various degrees. In some cases, this area has been very understudied. Most of the known coordination complexes are unstudied. Plutonium as an element perhaps presents some of the most interesting redox phenomena, exhibiting up to four oxidation states simultaneously in solution. Later actinides berkelium and californium have very scarce published literature, especially non-aqueous based electrochemistry. Other physical data such as log β and diffusion coefficients are also hard to find for many actinides. The beginning chapters focus on a well-studied ligand, 2,6-pyridinedicarboxylic acid (H2DPA) that has been well-characterized in solid-state methods for the lanthanides and actinides. This ligand has almost exclusively been studied under aqueous conditions, yet for reductive efforts with elements such as Sm, developing a non-aqueous approach was preferred. Detailed solubility investigations are provided, as well as detailed studies with cerium and plutonium, and finally studies with europium and samarium. The next set of chapters deals with later actinide investigations. For reductive electrochemistry with californium, detailed studies with cryptand were developed with the lanthanides. A preferred method was developed that was ultimately used to obtain novel data for californium. In the case of Bk, a pyridyl nitroxide ligand (pyNO) was used to collect the first non-aqueous cyclic voltammogram for this element. Lastly, the final chapter covers a few others systems that were given some efforts. Many of these systems have very interesting electrochemistry, but they were beyond the scope of just one dissertation to complete. These include Schiff bases and DOPO chemistry. The Schiff base data adds insightful data along with the tetravalent chemistry studied in earlier chapters, while the DOPO chemistry covers non-innocent redox phenomena affected by Pu.