Synthesis, Structure Elucidation, and Redox Properties of 99Tc Complexes of Lacunary Wells鈭扗awson Polyoxometalates: Insights into Molecular 99Tc鈭扢etal Oxide Interactions

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• 作者：Donna McGregor ; Benjamin P. Burton-Pye ; Robertha C. Howell ; Israel M. Mbomekalle ; Wayne W. Lukens ; Jr. ; Fang Bian ; Edward Mausolf ; Frederic Poineau ; Kenneth R. Czerwinski ; Lynn C. Francesconi
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：March 7, 2011
• 年：2011
• 卷：50
• 期：5
• 页码：1670-1681
• 全文大小：1084K
• 年卷期：v.50,no.5(March 7, 2011)
• ISSN：1520-510X

文摘

The isotope ⁹⁹Tc (尾_max, 293.7; half-life, 2.1 脳 10⁵ years) is an abundant product of uranium-235 fission in nuclear reactors and is present throughout the radioactive waste stored in underground tanks at the Hanford and Savannah River sites. Understanding and controlling the extensive redox chemistry of ⁹⁹Tc is important in identifying tunable strategies to separate ⁹⁹Tc from spent fuel and from waste tanks and, once separated, to identify and develop an appropriately stable waste form for ⁹⁹Tc. Polyoxometalates (POMs), nanometer-sized models for metal oxide solid-state materials, are used in this study to provide a molecular level understanding of the speciation and redox chemistry of incorporated ⁹⁹Tc. In this study, ⁹⁹Tc complexes of the (伪₂-P₂W₁₇O₆₁)^{10鈭?/sup> and (伪₁-P₂W₁₇O₆₁)10鈭?/sup> isomers were prepared. Ethylene glycol was used as a 鈥渢ransfer ligand鈥?to minimize the formation of TcO₂路xH₂O. The solution structures, formulations, and purity of TcVO(伪₁/伪₂-P₂W₁₇O₆₁)7鈭?/sup> were determined by multinuclear NMR. X-ray absorption spectroscopy of the complexes is in agreement with the formulation and structures determined from 31P and 183W NMR. Preliminary electrochemistry results are consistent with the EXAFS results, showing a facile reduction of the TcVO(伪₁-P₂W₁₇O₆₁)7鈭?/sup> species compared to the TcVO(伪₂-P₂W₁₇O₆₁)7鈭?/sup> analog. The 伪₁ defect is unique in that a basic oxygen atom is positioned toward the 伪₁ site, and the TcVO center appears to form a dative metal鈭抦etal bond with a framework W site. These attributes may lead to the assistance of protonation events that facilitate reduction. Electrochemistry comparison shows that the ReV analogs are about 200 mV more difficult to reduce in accordance with periodic trends.}