At the origin of this effect, there is the ability of Al +3 to stabilize the reduced form of DPPH • , not only by stabilizing the negatively charged DPPH -but also by promoting proton transfer from the first shell ethanol molecules to the nitrogen of diazine. This proton transfer is favor-able due to the significant lowering of the pKa of ligands bound to aluminum. All these properties stem from the fact that aluminum is a very strong Lewis acid, which can differentially stabilize charged species formed in redox reactions without the need to receive/release electrons directly.