The Role of the Organic Solvent Polarity in Isolating Uranyl Peroxide Capsule Fragments

Ana Arteaga; Debmalya Ray; Elliot Glass; Nicolas P. Martin; Lev N. Zakharov; Laura Gagliardi; May Nyman

doi:10.1021/acs.inorgchem.9b02660

The Role of the Organic Solvent Polarity in Isolating Uranyl Peroxide Capsule Fragments

Ana Arteaga, Debmalya Ray, Elliot Glass, Nicolas P. Martin, Lev N. Zakharov, Laura Gagliardi, May Nyman

Research output: Contribution to journal › Article › peer-review

12 Scopus citations

Abstract

Uranyl peroxide capsules are a fascinating class of polyoxometalates (POMs), discovered only in the 21st century. Understanding the reactivity between peroxide, alkali cations, and uranyl in alkaline solutions is important in nuclear science disciplines including mineralogy, nuclear energy, and legacy nuclear wastes. Here, we have developed a general procedure to isolate different fragments of the uranyl-peroxide POM capsules, using organic solvents to partially remove K⁺ salts from crude solids of the monomer building block UO₂(O₂)₃ ^4- (K-U₁), leading to stabilization of these reactive fragments. Higher polarity organic solvents remove more K⁺ salts from the crude solid, owed to higher solubility, resulting in more extensive linking of uranyl peroxide building units. By this strategy we have isolated and structurally characterized a dimer K₆[(UO₂)₂(O₂)₄(OH)₂]·7H₂O (K-U₂) and a hexamer face frequently observed in the capsules, K₁₂[(UO₂)₆(O₂)₉(OH)₆]·xH₂O (K-U₆). Comparing experimental and computed Raman spectra shows that these intermediates crystallize by a solid-to-solid transformation, via polymerization of the monomer building block. By small-angle X-ray scattering (SAXS), we track the conversion of the fragments to POM capsules; the reaction rate increases from K-U₁ (days) < K-U₂ (hours) < K-U₆ (instantaneous). This study provides a general synthetic procedure to isolate metastable uranyl peroxide oligomers and control the oligomerization, which will be later applied to systems with the heavier alkalis that are even less stable.

Original language	English
Pages (from-to)	1633-1641
Number of pages	9
Journal	Inorganic Chemistry
Volume	59
Issue number	3
DOIs	https://doi.org/10.1021/acs.inorgchem.9b02660
State	Published - Feb 3 2020
Externally published	Yes

Funding

This work was supported by the Department of Energy, National Nuclear Security Administration (NNSA) under Award Number DE-NA0003763. L.N.Z. and N.P.M. provided crystallography support for K–U 6 .

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title = "The Role of the Organic Solvent Polarity in Isolating Uranyl Peroxide Capsule Fragments",

abstract = "Uranyl peroxide capsules are a fascinating class of polyoxometalates (POMs), discovered only in the 21st century. Understanding the reactivity between peroxide, alkali cations, and uranyl in alkaline solutions is important in nuclear science disciplines including mineralogy, nuclear energy, and legacy nuclear wastes. Here, we have developed a general procedure to isolate different fragments of the uranyl-peroxide POM capsules, using organic solvents to partially remove K+ salts from crude solids of the monomer building block UO2(O2)3 4- (K-U1), leading to stabilization of these reactive fragments. Higher polarity organic solvents remove more K+ salts from the crude solid, owed to higher solubility, resulting in more extensive linking of uranyl peroxide building units. By this strategy we have isolated and structurally characterized a dimer K6[(UO2)2(O2)4(OH)2]·7H2O (K-U2) and a hexamer face frequently observed in the capsules, K12[(UO2)6(O2)9(OH)6]·xH2O (K-U6). Comparing experimental and computed Raman spectra shows that these intermediates crystallize by a solid-to-solid transformation, via polymerization of the monomer building block. By small-angle X-ray scattering (SAXS), we track the conversion of the fragments to POM capsules; the reaction rate increases from K-U1 (days) < K-U2 (hours) < K-U6 (instantaneous). This study provides a general synthetic procedure to isolate metastable uranyl peroxide oligomers and control the oligomerization, which will be later applied to systems with the heavier alkalis that are even less stable.",

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The Role of the Organic Solvent Polarity in Isolating Uranyl Peroxide Capsule Fragments

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