All the potential reactions D5a, D5b, and D7 evolve from a divalent Al 3+ -complex to a monovalent one. The significance of the charge reduction is clearly demonstrated if we compare D6 and D7 reduction rections. Both reactions imply the reduction of DPPH• with its further protonation and coordination to Al 3+ . While in reaction D7 the protonation takes place at the expense of the deprotonation of an ethanol ligand already coordinated to Al 3+ (Figure ), reducing the final charge of the Al 3+ -complex to +1, in reaction D6 the DPPH• protonation is assisted by an extra proton of the media that makes the final charge of the Al 3+ -complex to be +2. This small difference between the two reactions completely changes their thermochemistry, evolving from a spontaneous reaction (D7) with a E red that perfectly matches with experimental data to a non-spontaneous reaction (D6) with a E red that is absolutely in disagreement with experimental results. The difference between reactions D5a and D5b lies on the relative coordination of DPPH -and the deprotonated ethanol group (in cis for the D5a reaction and in trans for D5b) (see Figure ) while they describe the same chemical reaction. Specifically, the reduction reaction that presents a E red with the highest agreement with the experimental value is D7. This reaction accounts for the reduction of DPPH• coupled to its coordination to Al 3+ and an intramolecular protonation assisted by an ethanol ligand. Once again, as we saw for hydroquinones and for the redox reactions without the presence of Al 3+ , the global redox process is better de- ), we can see that the presence of aluminum increases the E red values (∆E ∅→Al red ), leading to a more exergonic process and stabilizing the reduced DPPH-H species.