There are, however, a few caveats. First, BSE@GW is a method to calculate excited state properties only. Thus it does not offer an option to predict ground state properties, such as the geometry or the spin state. As a consequence these properties must be calculated using a different method. Unfortunately, the present results for transition metal complexes show a rather strong dependence on geometry, thereby requiring a high precision geometry optimization (here MP2) in advance to produce reliable excitation energies. Second, concerning the accuracy of the excitation energies for Fe(II) triplet states, we cannot yet draw a similar conclusion as for the singlet states. Previous studies demonstrated that the BSE@GW framework tends to underestimate the transition energies of triplet states, which would result in a wrong electronic structure even though the ordering of the excited states is correct. Finally, we note that cases with strong static correlations like high-spin Co(II) can not adequately be considered with BSE@GW.