Electronic ground state and the d-d transitions in bis(biuretato)cobaltate(III) ions.

‡ differences in occupation numbers of the spin orbitals have been used in the spectral assignments of the d-d transitions. The energy calculations used one U parameter, two ﷿ parameters, and two Racah parameters. The ﷿ parameters, which were derived from Orgel orbitals of and a type, were found to be positive. The observed charge-transfer transitions are metal r ligand. The results of our calculations are in agreement with available experimental data, including the spin triplet ground state and the position of the lower d-d transitions. The approach is general and, for example, applicable to heme iron(II).