The geometry and vibrational frequencies of Co(OH2)6 2+ in the quartet state and Co(OH2)6 3+ in the singlet and quintet states were computed with quantum mechanics/molecular mechanics (QM/MM), whereby the LC-BOP-LRD functional was used for the QM part involving the Co(OH2)6 n+ (n = 2, 3) ions. The surrounding 124 MM water molecules were treated with the MMFF94 force field. The hydration energy differences between low-spin Co(OH2)6 3+ and Co(OH2)6 2+ or Co(OH2)6 3+ in the quintet state were also calculated using this method. The electronic energy of the Co(OH2)6 n+ (n = 2, 3) ions was calculated with wave function theory, multistate extended general multiconfiguration quasi-degenerate second-order perturbation theory and spin-orbit configuration interaction. The redox potential of the Co(OH2)6 2+/3+ couple, and the singlet-quintet (adiabatic) Gibbs energy difference of Co(OH2)6 3+, computed based on these data, agree with the experiment.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry