Charge transfers influence on the spin ground state of manganese and iron superoxide dismutases: a DFT study on a model of the reduced active site interacting with O2–

From DFT and time-dependent DFT calculations on MnIISOD and FeIISOD active site models interacting with O2– we have determined that metalto-ligand charge transfers stabilise the S = 2 and S = 5/2 spin states as ground spin states for the [MnIISOD-O2–] and [FeIISOD-O2–] model complexes, respectively. These charge transfers are ruled by the electronic configuration of the metal ion, and they can be determinant in the catalysis reaction.