Stability of multiply charged anions of lanthanide hexafluorides LnF 62− and LnF 63− (Ln=Ce to Lu)

Abstract

The kinetic and electronic stability of a series of free LnF 6 q− -type lanthanide hexafluorides (Ln=Ce to Lu; q=2,3) is studied with the relativistic effective core potentials of Cundari and Stevens. In all complexes (LnF 6 2− and LnF 6 3−), the octahedral or almost octahedral structure is calculated to be stable through normal mode analyses at the unrestricted Hartree–Fock (UHF) and complete active space self-consistent field (CASSCF) levels. The electronic stability of all complexes is investigated using the state-averaged CASSCF and quasidegenerate perturbation theory with multiconfigurational self-consistent field reference functions (MC-QDPT) schemes. The most electronically stable LnF 6 q− is LnF 6 2− for Ce, Pr, Nd, Pm, Sm, Tb, Dy, Ho, Er, Tm, Yb. These LnF 6 2− anions are found to have an energy barrier with respect to the unimolecular decomposition LnF 6 2−→LnF 6 5−+F − and are predicted to be long-lived species formally existing in a meta-stable state.