Ikeda Atsushi, Hennig Christoph, Tsushima Satoru, Takao Koichiro, Ikeda Yasuhisa, Scheinost Andreas C, Bernhard Gert
Forschungszentrum Dresden-Rossendorf (FZD), Institute of Radiochemistry, P.O. Box 510119, 01314 Dresden, Germany.
Inorg Chem. 2007 May 14;46(10):4212-9. doi: 10.1021/ic070051y. Epub 2007 Apr 7.
Electrochemical, complexation, and electronic properties of uranyl(VI) and -(V) carbonato complexes in an aqueous Na2CO3 solution have been investigated to define the appropriate conditions for preparing pure uranyl(V) samples and to understand the difference in coordination character between UO22+ and UO2+. Cyclic voltammetry using three different working electrodes of platinum, gold, and glassy carbon has suggested that the electrochemical reaction of uranyl(VI) carbonate species proceeds quasi-reversibly. Electrolysis of UO22+ has been performed in Na2CO3 solutions of more than 0.8 M with a limited pH range of 11.7 < pH < 12.0 using a platinum mesh electrode. It produces a high purity of the uranyl(V) carbonate solution, which has been confirmed to be stable for at least 2 weeks in a sealed glass cuvette. Extended X-ray absorption fine structure (EXAFS) measurements revealed the structural arrangement of uranyl(VI) and -(V) tricarbonato complexes, [UO2(CO3)3]n- [n = 4 for uranyl(VI), 5 for uranyl(V)]. The bond distances of U-Oax, U-Oeq, U-C, and U-Odist are determined to be 1.81, 2.44, 2.92, and 4.17 A for the uranyl(VI) complex and 1.91, 2.50, 2.93, and 4.23 A for the uranyl(V) complex, respectively. The validity of the structural parameters obtained from EXAFS has been supported by quantum chemical calculations for the uranyl(VI) complex. The uranium LI- and LIII-edge X-ray absorption near-edge structure spectra have been interpreted in terms of electron transitions and multiple-scattering features.
研究了铀酰（VI）和 -（V）碳酸根配合物在Na2CO3水溶液中的电化学、络合和电子性质，以确定制备纯铀酰（V）样品的合适条件，并了解UO22+和UO2+之间配位特性的差异。使用铂、金和玻碳三种不同工作电极的循环伏安法表明，碳酸铀酰（VI）物种的电化学反应是准可逆的。使用铂网电极在pH范围为11.7 < pH < 12.0的0.8 M以上的Na2CO3溶液中对UO22+进行了电解。它产生了高纯度的碳酸铀酰（V）溶液，已证实该溶液在密封玻璃比色皿中至少稳定2周。扩展X射线吸收精细结构（EXAFS）测量揭示了铀酰（VI）和 -（V）三碳酸根配合物[UO2(CO3)3]n- [铀酰（VI）时n = 4，铀酰（V）时n = 5]的结构排列。铀酰（VI）配合物的U - Oax、U - Oeq、U - C和U - Odist键长分别确定为1.81、2.44、2.92和4.17 Å，铀酰（V）配合物的分别为1.91、2.50、2.93和4.23 Å。EXAFS获得的结构参数的有效性得到了铀酰（VI）配合物量子化学计算的支持。铀的LI - 和LIII - 边X射线吸收近边结构光谱已根据电子跃迁和多重散射特征进行了解释。
