Design, Synthesis, and Characterization of Uranyl and Neptunyl Coordination Complexes

This dissertation focuses on exploring the fundamental chemistry of solid-state uranyl and neptunyl coordination complexes to better understand actinyl crystal chemistry and probe the nature of structure directing factors leading to their formation. The goal of this research is to design and synthesize coordination complexes that demonstrate rich chemical and structural diversity of the 5f-elements at a nexus with ionic liquids, protonated amines, and a variety of N-, O- and h²-(N-O) donor ligands.

The principle theme explores the use of functionalized ionic liquids as unconventional solvents that may act as a ligand, charge balance specie, or as an aqueous-less reaction medium. Several classes of ionic liquids were employed to develop coordination compounds and hybrid materials that expand on the topological diversity of solid-state uranyl structures and systematically investigate, through judicious selection of incorporated moieties, the importance and role of various structure directing factors (i.e. steric affects, hydrogen bonding, pH, temperature, etc.)

A second area of research investigates transuranic cyanometallates, and demonstrates marked differences between pentavalent neptunium and hexavalent uranium chemistry. Notably, the work demonstrates important differences relating to redox chemistry and so-called cation-cation interactions prevalent in Np(V) coordination chemistry. Furthermore, the work also demonstrates a novel system for exploring mixed-valent tetracyanoplatinate complexes, with the potential for chemical fine tuning of their magnetic and electronic properties.

A third area of research explores the importance of structural unit charge density matching and hydrogen bonding between an interlayer complex and anionic structural unit in the formation of two-dimensional uranyl sulfate compounds. Here, a literature review and analysis of structural data is used to elucidate aspects of structure directing properties to better inform on and provide clarity in their descriptions within the literature. This work provides a qualitative framework for understanding orientational geometric isomerism, interlayer stacking interactions and interlayer distance dependence for two-dimensional uranyl sulfate compounds incorporating protonated cyclic and alkylamines via templating effects.