Arteaga Ana, Ray Debmalya, Glass Elliot, Martin Nicolas P, Zakharov Lev N, Gagliardi Laura, Nyman May
Department of Chemistry , Oregon State University , Corvallis , Oregon 97331 , United States.
Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute , University of Minnesota , Minneapolis , Minnesota 55455 , United States.
Inorg Chem. 2020 Feb 3;59(3):1633-1641. doi: 10.1021/acs.inorgchem.9b02660. Epub 2020 Jan 21.
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 UO(O) (), 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 K[(UO)(O)(OH)]·7HO () and a hexamer face frequently observed in the capsules, K[(UO)(O)(OH)]·HO (). 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 (days) < (hours) < (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.
过氧化铀胶囊是一类引人入胜的多金属氧酸盐（POMs），直到21世纪才被发现。了解过氧化物、碱金属阳离子和铀酰在碱性溶液中的反应性，在包括矿物学、核能和遗留核废料等核科学学科中具有重要意义。在此，我们开发了一种通用方法来分离过氧化铀POM胶囊的不同片段，使用有机溶剂从单体结构单元UO(O)（）的粗固体中部分去除钾盐，从而使这些活性片段得以稳定。极性更高的有机溶剂由于溶解度更高，能从粗固体中去除更多的钾盐，导致过氧化铀结构单元之间的连接更加广泛。通过这种策略，我们分离并对一种二聚体K[(UO)(O)(OH)]·7HO（）和一种在胶囊中经常观察到的六聚体面K[(UO)(O)(OH)]·HO（）进行了结构表征。比较实验和计算得到的拉曼光谱表明，这些中间体通过单体结构单元的聚合，由固-固转变结晶而成。通过小角X射线散射（SAXS），我们追踪了片段向POM胶囊的转化过程；反应速率从（数天）<（数小时）<（瞬间）逐渐增加。这项研究提供了一种通用的合成方法来分离亚稳的过氧化铀低聚物并控制低聚反应，该方法随后将应用于稳定性更低的重碱体系。
