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

We have calculated the IP, DeltaG(e), and E-ox, values for 10 mono-substituted benzene molecules and compared them with experimental values obtained by linear sweep voltammetry. The E-ox. 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 E-ox, values to be lower by about 0.9 V. Consideration of bulk solvent effects is important to fully describe the experimental variation in E-ox. The HOMO, NBO, and Wiberg bond index were analyzed to investigate the changes when moving from neutral to cationic molecules. (C) 2002 Elsevier Science B.V. All rights reserved.