Rare Bird: U⁺⁵ in Uranium Chalcogenides

Author(s)

Anna A. Berseneva
Vladislav V. Klepov
Habiba B. Kashem, University of South CarolinaFollow
Alevtina A. Maksimova
Gregory Morrison, University of South CarolinaFollow
Joshua Wright
Joseph Schaeperkoetter
Scott T. Misture
Hans Conrad zur Loye, University of South CarolinaFollow

Document Type

Article

Abstract

Chalcogen environments tend to stabilize low oxidation states, thus making the +5 oxidation state in uranium chalcogenides extremely rare. Having one unpaired electron, the magnetism of U⁺⁵, 5f¹, is of significant interest; however, it is underexplored due to a scarcity of examples. Three related all-U⁺⁵ chalcogenides, Na₂Cu₅US₆, Na₃Cu₄US₆, and Na₃Cu₄USe₆, were obtained as single crystals via the flux-assisted boron chalcogen mixture method as part of a broader investigation of the Na-Cu-U-Q (Q = S and Se) systems. To test the formation of the Se-analog of Na2Cu5US6, we performed in situ high-temperature powder X-ray diffraction using sealed capillaries; this approach demonstrated the formation and presence of only Na₃Cu₄USe₆ and not “Na₂Cu₅USe₆” in the reaction mixture. In addition to assigning oxidation states using charge balance and the sample composition, oxidation states of copper, +1, and uranium, +5, in Na₂Cu₅US₆ were also determined via X-ray absorption near edge spectroscopy. Magnetic properties were investigated on both bulk powder samples of Na₂Cu₅US₆ and Na₃Cu₄UQ₆ (Q = S and Se) and millimeter-size single crystals of Na₂Cu₅US₆, where magnetic susceptibility and magnetization vs field measurements revealed antiferromagnetic behavior of Na₂Cu₅US₆ and Na₃Cu₄UQ₆ (Q = S and Se) with a TN of 4.7, 3.4, and 5.9 K, respectively. Finally, a broad discussion of the effective magnetic moment of U⁺⁵, which is significantly smaller, 1.06 μB in Na₂Cu₅US₆ and 1.08 μB in Na₃Cu₄USe₆, than predicted by spin-only (1.73 μB) and total angular momentum (2.54 μB) models. The fact that only about 20 compositions of such materials are currently known, highlights the need to explore additional compositions containing uranium in rare oxidation states before it will be possible to understand the magnetic properties of such materials more fully.

Digital Object Identifier (DOI)

https://doi.org/10.1021/acs.chemmater.4c01440

Publication Info

Published in Chemistry of Materials, Volume 63, Issue 16, 2024.

Rights

© 2024 American Chemical Society

APA Citation

Klepov, Kashem, Wright, & Schaeperkoetter (2024). Rare Bird: U⁺⁵ in Uranium Chalcogenides. Chemistry of Materials, 63(16). https://doi.org/10.1021/acs.chemmater.4c01440