Lanthanide(iii) hydration was studied by utilizing density-functional theory and second-order Møller-Plesset perturbation theory combined with scalar-relativistic 4f-in-core pseudopotentials and valence-only basis sets for the Ln(iii) ions. For [Ln(iii)(H(2)O)(h)](3+) (h = 7, 8, 9) and [Ln(iii)(H(2)O)(h-1)·H(2)O](3+) (h = 8, 9) molecular structures, binding energies, entropies and energies of hydration as well as Gibbs free energies of hydration were calculated using (8s7p6d3f2g)/[6s5p5d3f2g] basis sets for Ln(iii) and aug-cc-pV(D,T)Z basis sets for O and H in combination with the COSMO solvation model. At the generalized gradient approximation level of density-functional theory a preferred hydration number of 8 is found for La(iii)-Tm(iii) and 7 for Yb(iii)-Lu(iii), whereas hybrid density-functional theory predicts a hydration number 8 for all Ln(iii). At the SCS-MP2 level of theory the preferred hydration number is found to be 9 for La(iii)-Sm(iii) and 8 for Eu(iii)-Lu(iii) in good agreement with experimental evidence.

A systematic computational approach to An(III) hydration on a density-functional level of theory, using quasi-relativistic 5f-in-core pseudopotentials and valence-only basis sets for the An(III) subsystems, is presented. Molecular structures, binding energies, hydration energies, and Gibbs free energies of hydration have been calculated for [An(III)(OH(2))(h)](3+) (h = 7, 8, 9) and [An(III)(OH(2))(h-1) * OH(2)](3+) (h = 8, 9), using large (7s6p5d2f1g)/[6s5p4d2f1g] An(III) and cc-pVQZ O and H basis sets within the COSMO implicit solvation model. An(III) preferred primary hydration numbers are found to be 8 for all An(III) at the gradient-corrected density-functional level of theory. Second-order Møller-Plesset perturbation theory predicts preferred primary hydration numbers of 9 and 8 for Ac(III)-Md(III) and No(III)-Lr(III), respectively.

The complexes of uranium(VI) with salicylhydroxamate, benzohydroxamate, and benzoate have been investigated in a combined computational and experimental study using density functional theory methods and extended X-ray absorption fine structure spectroscopy, respectively. The calculated molecular structures, relative stabilities, as well as excitation spectra from time-dependent density functional theory calculations are in good agreement with experimental data. Furthermore, these calculations allow the identification of the coordinating atoms in the uranium(VI)-salicylhydroxamate complex, i.e. salicylhydroxamate binds to the uranyl ion via the hydroxamic acid oxygen atoms and not via the phenolic oxygen and the nitrogen atom. Carefully addressing solvation effects has been found to be necessary to bring in line computational and experimental structures, as well as excitation spectra.

Theory C 1000 Approaching Actinide(+III) Hydration from First Principles -[hydration energies of [M(OH 2 ) n ] 3+ with M: Ac-Lr and n = 7, 8, 9]. -(WIEBKE, J.; MORITZ, A.; CAO, X.; DOLG*, M.; Phys. Chem. Chem. Phys. 9 (2007) 4, 459-465; Inst. Theor.