Determination of the oxidation potentials of organic benzene derivatives: theory and experiment

We have calculated the IP, ΔGe, and Eox values for 10 mono-substituted benzene molecules and compared them with experimental values obtained by linear sweep voltammetry. The Eox values were evaluated using the density functional method and thermodynamic cycles. The relative oxidation potentials are in close agreement with experimental values, while the UB3LYP/6-31+G(d) approach shows the absolute Eox values to be lower by about 0.9 V. Consideration of bulk solvent effects is important to fully describe the experimental variation in Eox. The HOMO, NBO, and Wiberg bond index were analyzed to investigate the changes when moving from neutral to cationic molecules.