Premium
Investigating Actinyl Oxo Cations by X‐ray Absorption Spectroscopy
Author(s) -
Den Auwer Christophe,
Simoni Eric,
Conradson Steven,
Madic Charles
Publication year - 2003
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200300093
Subject(s) - uranyl , chemistry , extended x ray absorption fine structure , actinide , x ray absorption spectroscopy , xanes , valence (chemistry) , aqueous solution , absorption spectroscopy , coordination complex , inorganic chemistry , uranium , coordination sphere , molecular orbital , x ray absorption fine structure , crystallography , oxidation state , spectroscopy , computational chemistry , molecule , ion , metal , crystal structure , organic chemistry , physics , materials science , quantum mechanics , metallurgy
Early actinide elements (from U to Am) have the ability to form linear trans ‐dioxo complexes with formal valence of the actinide being equal to ( V ) or ( VI ). For instance, the ubiquity of the uranyl cation in uranium aqueous chemistry is the basis for its very important industrial and environmental concerns. As a result, the physical chemistry of the actinyl moieties has been the subject of constantly growing investigations. Among all the spectroscopic probes, X‐ray absorption spectroscopy is a particularly useful element and energy‐selective technique. This article reviews the investigation of molecular actinyl complexes using both XANES and EXAFS tools. The absorption edge features have long been used to characterize the frontier orbitals of the absorbing atom. In the case of actinide cations, the L III edge, located in the hard X‐ray region, provides a useful fingerprint of the cation polyhedron. Tentatively, simple molecular orbital considerations together with full multiple scattering simulation codes have provided significant interpretations of the edge features. Various examples involving a distortion of the actinyl coordination sphere, starting from the aqueous species are given. Complementary structural data can be obtained in the EXAFS region of the absorption spectrum. In the literature, such molecular systems have been well documented from uranyl aqueous chemistry to neptunyl or plutonyl coordination complexes with oxygen donor ligands. Furthermore, complexation mechanisms upon absorption onto mineral surfaces have been increasingly investigated over the past few years. Overall, contribution of the XAS technique to a better understanding of the actinide bonding is demonstrated from various examples of the literature and the authors’ data. Importance of the simulation codes in order to better describe the absorption features is also strongly underlined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)