Abstract
We obtained a kerosene-soluble form of the lithium salt [UO2(O2)(OH)2]24 phase (Li-U24), by adding cetyltrimethylammonium bromide surfactant to aqueous Li-U24. Interestingly, its variable-temperature solution 7Li NMR spectroscopy resolves two narrowly spaced resonances down to -10 °C, which shift upfield with increasing temperature, and finally coalesce at temperatures > 85 °C. Comparison with solid-state NMR demonstrates that the Li dynamics in the Li-U24-CTA phase involves only exchange between different local encapsulated environments. This behavior is distinct from the rapid Li exchange dynamics observed between encapsulated and external Li environments for Li-U24 in both the aqueous and the solid-state phases. Density functional theory calculations suggest that the two experimental 7Li NMR chemical shifts are due to Li cations coordinated within the square and hexagonal faces of the U24 cage, and they can undergo exchange within the confined environment, as the solution is heated. Very different than U24 in aqueous media, there is no evidence that the Li cations exit the cage, and therefore, this represents a truly confined space.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 5514-5525 |
| Number of pages | 12 |
| Journal | Inorganic chemistry |
| Volume | 57 |
| Issue number | 9 |
| DOIs | |
| State | Published - May 7 2018 |
Bibliographical note
Funding Information:The synthesis, solution NMR and SAXS characterization, compositional analysis, and computational studies performed at OSU, NDU, and UMN were performed as a part of the Materials Science of Actinides, an Energy Frontier Research Center, funded by the Department of Energy, under award number DE-SC0001089. The solid-state NMR was performed at Sandia National Laboratories, which is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. Jing Xie thanks Pere Miró and Bess Vlaisavljevich for helpful discussion.
Publisher Copyright:
© 2018 American Chemical Society.