Halogen- and Hydrogen-bonding Effects in a Series of Uranyl Fluorides and MOFs for Radionuclide Detection
Spent nuclear fuel stewardship has been at the forefront of actinide chemistry since the advent of nuclear weapons and nuclear energy. Spent fuel is comprised of an evolving mixture of radioactive elements, many of which take hundreds to thousands of years to decay into stable isotopes. The disposal, safe handling, and detection of these materials calls for research to understand their reactivity and properties.
The uranyl cation, UO 2 2+ , is the most stable and environmentally relevant form of uranium featuring strong U=O bonds which impart significant stability. In the current project, we study uranyl fluoride materials which are some of the most prominent species of uranium in the nuclear fuel cycle. In a series of uranyl fluoride materials, structural analysis revealed molecular assembly via noncovalent interactions in the second coordination sphere with close halogen-oxo contacts. These interactions were probed via Raman spectroscopy where a decrease in the halogen-oxo distances manifests as a red-shifting trend among the Raman U=O symmetric stretches. This spectroscopic trend coupled with computational analysis supports the conclusion that more polarizable halogen atoms allow for stronger halogen-oxo interactions, thus weakening the U=O bond. Another aspect of nuclear fuel stewardship is the development of functional materials for capture and detection of relevant radionuclides in support of (for example) forensics applications. We sought to synthesize a metal organic framework (MOF) that could trap certain radioisotopes and provide an optical indication of their presence via scintillation. Presented herein is a series of isostructural MOFs, [Ln 2 (TFTA) 3 (2,2’-bpy) 2 (H 2 O) 2 ] (Ln = Sm-Er), consisting of lanthanide metal cations bound to tetrafluoroterephthalate linkers and 2,2’-bipyridine capping ligands. Crystal structures and void space calculations suggest these materials can uptake radioactive noble gas species, and efforts are in progress to ascertain scintillation properties.
BIO
Elizabeth received her B.S. in Chemistry from Bloomsburg University of Pennsylvania where she did undergraduate research under Dr. Matthew Polinski, studying nuclear and synthetic solid-state inorganic chemistry. Elizabeth then joined Professor Christopher L. Cahill’s research group in 2022 to pursue her Ph.D.in the field of nuclear chemistry.
