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Title: Resolving Confined 7Li Dynamics of Uranyl Peroxide Capsule U 24

Here, we obtained a kerosene-soluble form of the lithium salt [UO 2(O 2)(OH) 2] 24 phase (Li-U 24), by adding cetyltrimethylammonium bromide surfactant to aqueous Li-U 24. 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-U 24-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-U 24 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 U 24 cage, and they can undergo exchange within the confined environment, as the solution is heated. Very different than U 24 in aqueous media, there is no evidence that the Li cations exit the cage, and therefore, this represents a truly confined space.
Authors:
ORCiD logo [1] ;  [2] ;  [3] ; ORCiD logo [3] ; ORCiD logo [4] ; ORCiD logo [2] ; ORCiD logo [1]
  1. Univ. of Minnesota, Minneapolis, MN (United States)
  2. Oregon State Univ., Corvallis, OR (United States)
  3. Univ. of Notre Dame, Notre Dame, IN (United States)
  4. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Report Number(s):
SAND-2018-1993J
Journal ID: ISSN 0020-1669; 660910
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 57; Journal Issue: 9; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Research Org:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Energy Frontier Research Centers (EFRC) (United States). Materials Science of Actinides (MSA)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1457405

Xie, Jing, Neal, Harrison A., Szymanowski, Jennifer, Burns, Peter C., Alam, Todd M., Nyman, May, and Gagliardi, Laura. Resolving Confined 7Li Dynamics of Uranyl Peroxide Capsule U24. United States: N. p., Web. doi:10.1021/acs.inorgchem.8b00474.
Xie, Jing, Neal, Harrison A., Szymanowski, Jennifer, Burns, Peter C., Alam, Todd M., Nyman, May, & Gagliardi, Laura. Resolving Confined 7Li Dynamics of Uranyl Peroxide Capsule U24. United States. doi:10.1021/acs.inorgchem.8b00474.
Xie, Jing, Neal, Harrison A., Szymanowski, Jennifer, Burns, Peter C., Alam, Todd M., Nyman, May, and Gagliardi, Laura. 2018. "Resolving Confined 7Li Dynamics of Uranyl Peroxide Capsule U24". United States. doi:10.1021/acs.inorgchem.8b00474.
@article{osti_1457405,
title = {Resolving Confined 7Li Dynamics of Uranyl Peroxide Capsule U24},
author = {Xie, Jing and Neal, Harrison A. and Szymanowski, Jennifer and Burns, Peter C. and Alam, Todd M. and Nyman, May and Gagliardi, Laura},
abstractNote = {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},
journal = {Inorganic Chemistry},
number = 9,
volume = 57,
place = {United States},
year = {2018},
month = {4}
}