Advances in actinide solid-state and coordination chemistry
- PDF / 1,004,475 Bytes
- 10 Pages / 585 x 783 pts Page_size
- 55 Downloads / 196 Views
Introduction The past decade has witnessed a reemergence of actinide solidstate and coordination chemistry as a major research emphasis, with several international groups focusing on the creation and characterization of a myriad of complex and unprecedented materials and complexes with unusual properties and structures. To summarize all recent important activity in actinide chemistry would require more space than this article allows. The advances we have selected for discussion are of particular interest, in part, because few, if any, of these developments would have been readily predicted a decade ago. The developments covered here include the emergence of nanostructured actinide materials, specifically polyoxometalate clusters; topological implications of cation-cation interactions; unusual framework and complex actinyl borate materials; the creation of U(VI) tetraoxide species; the emergence of U(V) chemistry in both the solution and solid state; and discovery of analogues of the uranyl ion. Recent reviews of these and other aspects of actinide chemistry provide far more detail.1–9
Background The largest infusion of new knowledge in actinide solid-state chemistry is in inorganic actinide solids (including those templated by organic moieties), including natural minerals. From 1995 to 2005, the number of known structures more than
doubled in the case of uranium,10 and several research groups have placed an increased emphasis on the creation of complex materials containing transuranium elements over the past five years.11–18 A high proportion of the characterized compounds were synthesized under hydrothermal conditions, typically in the range of 100 to 220°C. Such relatively mild hydrothermal conditions readily promote the growth of crystals suitable for single-crystal diffraction studies in many actinide-containing chemical systems. Studies of the solid-state chemistry of actinides also provided much needed insights into the solution chemistry of these complex elements, and research coupling crystallographic data with complementary synchrotron-based solution studies is starting to provide unique insights into the complexity in solutions.19–21 The structures of actinide materials are very strongly oxidation-state dependent. Coordinating ligands tend to be evenly distributed about the lower-valence (III, IV) actinide cations, and coordination numbers in the range of eight to 12 are common. This homogeneous distribution of ligands about the actinide cation fosters formation of higher symmetry structures, often frameworks. Such structures usually have analogues elsewhere on the periodic table, especially in the lanthanide series. The situation is very different for actinide cations in the V and VI oxidation states. These almost always occur as linear (or nearly so) (AnO2)+1,+2 dioxocations (where
Peter C. Burns, Department of Civil Engineering and Geological Sciences, University of Notre Dame, IN 46556, USA; [email protected] Yasuhisa Ikeda, Laboratory for Nuclear Reactors at Tokyo Institute of Technology, Japan; yikeda@nr
Data Loading...
