NMR's contribution to actinide complexes in solution

Molecular-scale chemical information about solutions is of primary importance in the understanding of liquid-liquid extraction phenomena. From this point of view, NMR spectroscopy is a useful tool. However, in the field of the nuclear fuel reprocessing, this technique needs to overcome certain intrinsic limitations, including the presence of both paramagnetic metals and radioactivity. Because of the experimental difficulties encountered, paramagnetic data about actinides is scarce but nevertheless required in order to take advantage of information contained in the electron-nucleus interactions. This study will present two speciation studies dealing with Am(III) and U(IV) complexes in solution. Am(III) paramagnetism was found to be weak enough to observe a complex formed with a tetrapodal hexadentate N,O ligand in an aqueous solution. Although U(IV) paramagnetism is stronger, due to a fast chemical exchange with the ionic liquid used it was possible to extract structural information arising from 1H NMR spectra analysis. Results obtained in solution are consistent with X-Ray data which indicate that ligand-metal interactions mainly come from hydrogen bonding.