Institut für Nukleare Entsorgung, Karlsruhe Institute of Technology (KIT-INE), Karlsruhe, Germany.
Dalton Trans. 2012 Aug 28;41(36):10941-7. doi: 10.1039/c2dt30243h.
Tetravalent thorium exhibits a strong tendency towards hydrolysis and subsequent polymerization. Polymeric species play a crucial role in understanding thorium solution chemistry, since their presence causes apparent solubility several orders of magnitude higher than predicted by thermodynamic data bases. Although electrospray mass spectrometry (ESI MS) identifies Th(IV) dimers and pentamers unequivocally as dominant species close to the solubility limit, the molecular structure of Th(5)(OH)(y) polymers was hitherto unknown. In the present study, X-ray absorption fine structure (XAFS) spectroscopy, high energy X-ray scattering (HEXS) measurements, and quantum chemical calculations are combined to solve the pentamer structure. The most favourable structure is represented by two Th(IV) dimers linked by a central Th(IV) cation through hydroxide bridges.
四价钍表现出强烈的水解和随后聚合倾向。聚合态物质在理解钍溶液化学中起着至关重要的作用，因为它们的存在使得实际溶解度比热力学数据库预测的高出几个数量级。尽管电喷雾质谱（ESI-MS）明确地将 Th(IV)二聚体和五聚体鉴定为接近溶解度极限的优势物种，但 Th(5)(OH)(y)聚合物的分子结构在此之前尚不清楚。在本研究中，结合使用 X 射线吸收精细结构（XAFS）光谱、高能 X 射线散射（HEXS）测量和量子化学计算来解决五聚体结构。最有利的结构由两个通过氢氧化物桥连接的中心 Th(IV)阳离子的 Th(IV)二聚体表示。
