Calculation of the Redox Properties of Aromatics and Prediction of Their Coupling Mechanism and Oligomer Redox Properties

The B3LYP density functional theory method has been used to determine theoretical values for the peak oxidation potentials for a range of redox-active aromatics in acetonitrile at room temperature. Excellent agreement to within 37 mV is found between these values and those observed experimentally. The calculated electron spin density distributions of indole monomer and indole oligomer radical cations also enable a plausible mechanism to be advanced by which the experimentally observed asymmetric trimer product is formed. Theoretical values for the peak oxidation potential of the indole trimer also show excellent agreement with those observed previously in electrochemical studies, again consistent with this asymmetric trimer product. Together, with the previously demonstrated ability of this approach to predict the coupling mechanisms and redox properties of the oligomers formed from indolocarbazole, these calculations provide a method for the in silico screening of molecular properties to inform molecular materials design and electrosynthesis.