Solution coordination chemistry of actinides: Thermodynamics, structure and reaction mechanisms

The emphasis of this review is on the combination of experimental and theoretical methods to obtain microscopic information on the chemistry of actinides in aqueous solution. A brief discussion is given of some important experimental methods that provide information on the equilibrium constants and constitution of actinide complexes in solution, their structure and the rate and mechanism of ligand substitution reactions. The microscopic perspective is provided by a comparison of experimental data with those obtained using quantum chemical methods; the emphasis is here on structure and reaction mechanisms. Most of the experimental data refer to the chemistry of uranium, thorium and curium, but this information can be generalized to other actinides as their chemistry is often very similar in a given oxidation state. The first step in the analysis of complex formation in solution is based on equilibrium analytical methods; the discussion is here focused on those requiring macro amounts of actinides, as these are necessary in the methods used to obtain structure (large angle X-ray scattering, extended X-ray absorption spectroscopy and NMR) and dynamic (NMR, relaxation and stopped-flow methods) information. Finally, some comments are made on how the molecular understanding of complex formation between UO2 (2+) and small ligands may be of importance in naturally occurring ligands like humic and fulvic acids and biomolecules, such as amino acids, proteins and nucleotides. (c) 2005 Elsevier B.V. All rights reserved.