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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)
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