Here, 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.
Xie, Jing, Neal, Harrison A., Szymanowski, Jennifer, Burns, Peter C., Alam, Todd M., Nyman, May, & Gagliardi, Laura (2018). Resolving Confined <sup>7</sup>Li Dynamics of Uranyl Peroxide Capsule U<sub>24</sub>. Inorganic Chemistry, 57(9). https://doi.org/10.1021/acs.inorgchem.8b00474
@article{osti_1457405,
author = {Xie, Jing and Neal, Harrison A. and Szymanowski, Jennifer and Burns, Peter C. and Alam, Todd M. and Nyman, May and Gagliardi, Laura},
title = {Resolving Confined <sup>7</sup>Li Dynamics of Uranyl Peroxide Capsule U<sub>24</sub>},
annote = {Here, 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.},
doi = {10.1021/acs.inorgchem.8b00474},
url = {https://www.osti.gov/biblio/1457405},
journal = {Inorganic Chemistry},
issn = {ISSN 0020-1669},
number = {9},
volume = {57},
place = {United States},
publisher = {American Chemical Society (ACS)},
year = {2018},
month = {04}}
Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Energy Frontier Research Centers (EFRC) (United States). Materials Science of Actinides (MSA)