Finally, we note that the DFT calculations reported in this study predict a notoriously low VIE of 3.4 eV for the deprotonated form of 6MP, which leads to the prediction of a negative oxidation potential energy (Table ). We think that this is an artifact of DFT that results in the underestimation of the VIE for the deprotonated form at this level of theory. DFT is known to underestimate the energies of anionic species, hence, it would not be surprising that it may also underestimate the VIE of the deprotonated form of 6MP. Indeed, similar VIE calculations performed using other functionals (PBE0, M06, and B3PW91) lead to similarly low values (~3.5 eV, Table ), but the calculation of the VIE using the MP2 level of theory leads to a ca. 1 eV higher ionization energy for the deprotonated form of 6MP (4.4 eV). This result supports our interpretation of the VIE using DFT and caution against overinterpretation of the results presented in Table for the deprotonated form of 6MP.