Insights into the solution structure of the hydrated uranyl ion from neutron scattering and EXAFS experiments.

The solution structure of 1.0 M Uranyl Chloride has been determined by the EPSR modelling of a combination of neutron scattering and EXAFS data. The experimental data show an equilibrium in solution between [UO 2 (H 2 O) 5 ] 2+ and [UO 2 Cl(H 2 O) 4 ] + with a stability constant of 0.23 ± 0.03 mol -1 dm -3 . A much smaller fraction of the neutral [UO 2 Cl 2 (H 2 O) 3 ] ion is also observed. The data also show, for the first time in solution, that the uranyl ion is a very poor hydrogen bond acceptor, but the coordinated waters show enhanced hydrogen bond ability compared to the bulk water.