A DFT Study of the Electronic Spectrum of the α-Keggin Anion [CoIIW12O40]6-

Multiplet splittings for several excited configurations of [Co(II)W(12)O(40)](6-) were calculated using DFT methods. In agreement with the experimental interpretation of the spectrum the calculations found that the first strong band corresponds to Co d-d transitions, but it is worth noting that superposed to these transitions there are charge transfer transitions from cobalt to tungsten. The calculations also showed the importance of Jahn-Teller distortions in the excited states. With the exception of the consequences derived from a smaller splitting of d cobalt orbitals the d-d spectrum of [CoCl(4)](2-) is similar to that of the more complex Keggin anion. Finally, the energy of the bielectronic transition (4)A(2) --> (4)T(1)(P) was estimated via an approximate procedure based on ligand field theory.