Utilizing Noncovalent Interactions for the Assembly of f-element Hybrid Materials
The study of f-elements, the lanthanides and actinides, is a broad field that encompasses a wide range of disciplines and is motivated by a cognizance of material scarcity, environmentalism, and legacy waste from nuclear weapons and energy production. f-elements bearing hybrid materials, those with inorganic and organic entities assembled on a molecular scale provide an appropriate forum for targeted syntheses and for study of structure-property relationships. The utilization of noncovalent interactions (NCIs), intermolecular forces such as halogen or hydrogen bonds that are not formal bonds, in the formation of hybrid materials provides a level synthetic control necessary for predictable molecular assembly and targeting structural criteria. By judiciously choosing the metal and ligands, and applying a ‘cap and link’ strategy of utilizing N- and O-donating organic ligands, molecules can then be connected and coaxed into the crystalline solid-state. Compounds are structurally characterized with single crystal X-ray diffraction to determine atom and ligand connectivity which are then rationalized using density functional theory generated electrostatic surface potentials. To highlight this, a series of uranyl materials is presented wherein the increasing polarizability of halogens on benzoate ligands (F, Cl. Br, and I) cause structural and spectroscopic changes. Introduction of a halogen-oxo interaction with more polarizable halogens shift the luminescence and Raman spectra profiles, allowing investigation of the structure-property relationships within this series of compounds. By controlling the coordination environment with appropriate ligands, varying structural substituents, and analyzing shifts in f-element spectroscopic behavior, we were able to probe the fundamental structure-properties relationships in these uranyl, and more generally f-element-containing, hybrid materials can be studied.
J. August Ridenour is a fifth-year chemistry Ph.D. candidate at GW University, working with Dr. Cahill. He graduated with a B.S. in Chemistry and History from Dickinson College in 2014. His current research focus is on the structural and spectroscopic characterization of lanthanide (Ln) and actinide (An) containing hybrid materials. Concurrently, August is a teaching assistant for the Science of Nuclear Materials course at the Elliot School of International Affairs, taught by Dr. Cahill. This course melds his two academic and professional interests, actinide chemistry with nuclear science and security policy, while working to provide policy students a modicum of technical understanding.