Computational study of lanthanide(III) hydration

Lanthanide(III) hydration was studied by utilizing density-functional theory and second-order Moller-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)center dot 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.