Solvent Structure and the Extended Range Hydration of Cr3+ in Aqueous Solution

H/D isotopic substitution neutron scattering has been used to investigate the short and intermediate range solution structure in a 1 m aqueous solution of chromium nitrate. To improve the reliability of the local structural information on the cation environment, information has been incorporated from available extended X-ray absorption fine structure (EXAFS) spectroscopy data into the applied analytical framework. The markedly different structural sensitivities of the experimental probes allow the construction of a detailed three-dimensional atomistic model using the empirical potential structure refinement (EPSR) technique, The method facilitates the construction of a model that is consistent with regards to both the structural details of the immediate Cr3+ aqua-ion environment and the bulk hydrogen-bonded network of solvent water molecules. The results confirm the suitability of the [Cr(H2O)(6)](3+) hydrated ion concept to describe the first hydration shell of this cation and clarify how this pseudomolecular unit is structurally incorporated in the longer range aqueous environment.