Non-Aqueous Transuranic Coordination Complexes

As of 2014, there is an expected 69,000 metric tons of nuclear waste sitting in storage in the U.S. Little efforts have been made to deal with the radiotoxicity of the spent nuclear fuel (SNF). The problem arises from the complex mixture of the SNF and highly radioactive actinides. Due to the high radioactivity of the minor actinides (Pu-Cm), there is a lack of understanding the fundamental chemistry of the actinides. The focus of this work is to prepare coordination complexes that can be used as probes for elucidating changes in the structure and bonding across the actinides series Most coordination chemistry that has been studied with the actinide series has only utilized ligands stable to oxygen and moisture due to the difficulties of handling the transuranium actinides. The chemistry of non-aqueous ranium has made great progress, while, the non-aqueous chemistry of the transuranic elements is relatively unexplored and offers a wider platform for exploring methods of deducing electronic structure and information about the actinide-ligand bond. Such information can be very useful for discovering trends in the whole series. The beginning chapters focus on simple coordination compounds using soft N and S donor ligands for complexing Am-Cf. Since very little structure data is known for these elements and softer donor ligands have shown to have a preference over trivalent actinides than lanthanides, we focus on these systems to understand the trends in bonding across the 5f series. Chapter 4 focus on a series (U-Cf) of complexes using the redox active ligand 2,4,6,8-tetrakis(tert-butyl)-9-hydroxyphenoxanone (HDOPO) were synthesized in non-aqueous conditions under an inert atmosphere and have been fully characterized by X-ray, optical, magnetic, and computational techniques. Spectroscopic data reveals the An(DOPO)3 complexes of the earlier actinides being the tetravalent state, in contrast to the later actinides, they are in the trivalent state. Furthermore, the Cf(III) complex disrupts the tris-chelate trend due to radiolysis. It is also shown that the ligand undergoes redox transitions to stabilize the higher oxidation states of the earlier actinides. The results will help contribute toward gaining foundational knowledge of structure and bonding in non-aqueous transuranic chemistry as well as give insight into the participation of f-orbitals in bonding. The ending chapters are out of the scope of non-aqueous chemistry but projects that pertain to the nature of the actinide series. As the first focuses on the effects of radiolysis. As we go to the heavier actinides, radiolysis affects the crystallization of our targeted products. In this case, an aged thorium source produces peroxide over time changing the result of the product. Lastly, is an example of driven degeneracy covalency in an americium chromate system. It was thought the later actinides tend to be more ionic, however we are finding small amount of covalent character partakes in the bonding. Collectively, this body of work primary focus is elucidating the structure and bonding of the f-elements through coordination complexes utilizing various techniques.