Extraction of local coordination structure in a low-concentration uranyl system by XANES.
Extraction of local coordination structure in a low-concentration uranyl system by XANES.
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DOI：
10.1107/s1600577516001910
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发表时间：
2016-05
影响因子：
2.5
通讯作者：
Lin-juan Zhang;Jing Zhou;Jianyong Zhang;Jing Su;Shuo Zhang;N. Chen;Yunpeng Jia;Jiong Li;Yu Wang;Jian Qiang Wang
中科院分区：
文献类型：
--
作者：
Lin-juan Zhang;Jing Zhou;Jianyong Zhang;Jing Su;Shuo Zhang;N. Chen;Yunpeng Jia;Jiong Li;Yu Wang;Jian Qiang Wang
在原子/分子尺度上获取铀酰物质的结构信息是控制和预测其理化性质的关键步骤。为了获得这些信息，对铀酰配合物的实验和理论L3-edge x射线吸收近边缘结构（XANES）光谱进行了系统的研究。结果表明，铀酰类化合物的键长R和XANES的相对能位ΔE分别为：轴向面ΔE1 = 168.3/R(U-Oax)(2) - 38.5，赤道面ΔE2 = 428.4/R(U-Oeq)(2) - 37.1。这些公式可用于直接提取铀吸收剂与氧配体原子在铀酰离子轴向面和赤道面的距离。此外，根据硝酸盐浓度逐渐变化的一系列硝酸铀酰配合物的平均赤道配位键长度，估计了水分子和硝酸盐配体得到的每种构型的相对权重。XANES分析结果与扩展x射线吸收精细结构（EXAFS）分析结果一致。XANES分析适用于普遍存在的铀酰配体配合物，如铀酰碳酸配合物。最重要的是，XANES研究方法可以扩展到低浓度的铀酰体系，如铀酰-氨基肟酸盐配合物（~ 40 p.p.m.铀）的结果所示。定量XANES分析是一种可靠、直接的方法，为锕系元素的结构化学研究提供了一种简化的方法。
Obtaining structural information of uranyl species at an atomic/molecular scale is a critical step to control and predict their physical and chemical properties. To obtain such information, experimental and theoretical L3-edge X-ray absorption near-edge structure (XANES) spectra of uranium were studied systematically for uranyl complexes. It was demonstrated that the bond lengths (R) in the uranyl species and relative energy positions (ΔE) of the XANES were determined as follows: ΔE1 = 168.3/R(U-Oax)(2) - 38.5 (for the axial plane) and ΔE2 = 428.4/R(U-Oeq)(2) - 37.1 (for the equatorial plane). These formulae could be used to directly extract the distances between the uranium absorber and oxygen ligand atoms in the axial and equatorial planes of uranyl ions based on the U L3-edge XANES experimental data. In addition, the relative weights were estimated for each configuration derived from the water molecule and nitrate ligand based on the obtained average equatorial coordination bond lengths in a series of uranyl nitrate complexes with progressively varied nitrate concentrations. Results obtained from XANES analysis were identical to that from extended X-ray absorption fine-structure (EXAFS) analysis. XANES analysis is applicable to ubiquitous uranyl-ligand complexes, such as the uranyl-carbonate complex. Most importantly, the XANES research method could be extended to low-concentration uranyl systems, as indicated by the results of the uranyl-amidoximate complex (∼40 p.p.m. uranium). Quantitative XANES analysis, a reliable and straightforward method, provides a simplified approach applied to the structural chemistry of actinides.