Figure (a) shows the ranges of the vertical S 1 and T 1 excitation energies at the S 0 geometry as well as the adiabatic T MC , T MLCT , and Q MC excitation energies over the whole set of parameters. These ranges are plotted against the Fe-N bond length, which is the the main geometric difference between these electronic states. Note that the ranges of α ∈ [0.0, 0.30] and ω ∈ [0.0, 0.25] are typical for mediumsized metal complexes and can be found in literature (this range also includes the popular B3LYP functional). We note that the energies of the T MLCT state have the smallest dependence on the chosen parameters, whereas both MC states vary substantially. For a certain domain of parameters, the quintet state is lower than the singlet ground state, see Fig.