Local Electronic Structure and Stability of Pentacene Oxyradicals

A series of pentacene oxyradicals is studied as a model of an oxidized graphene edge. The relative stability of the oxyradical species formed is rationalized on the basis of the concept of local aromaticity. It is found that qualitative and quantitative measures of delocalized bonding show consistently that formation of the π-aromatic fragments associated with different reference π-aromatic systems explain trends in Gibbs free energies and relative energies. As a result, a chemically intuitive model based on aromaticity can explain the relative stability of the oxyradicals in a way that uniquely appeals to chemists’ knowledge of structure and reactivity.