Frozen-orbital analysis of the excited states of metal complexes in high symmetry: O_h case

A frozen-orbital analysis (FZOA) is proposed in order to understand the nature and the ordering of the excited states due to the excitations between degenerate Orbitals of metal complexes in high symmetry. The FZOA method represents a direct application of group theory. In the FZOA approach, only a few two-electron integrals are considered to explain the ordering and the energy splittings of the excited states, which are brought about by excitations between two degenerate Orbitals. Furthermore, FZOA may be utilized to explain the intensities of the absorption peaks. Here, we apply FZOA to two series of the excited states of MoF₆. Although there are large discrepancies between the actual excitation energies by FZOA and those derived by more accurate calculations, the ordering and the energy splittings are comparable. This relative agreement is sufficient to justify an analysis based on FZOA methods. On the basis of the present results, we suggest that FZOA methods would yield some general insight into the nature of the excited states for molecules of high symmetry.