Oxidative transformations of surface-bound perylene

We report on the covalent attachment of perylene derivatives to silica and indium-doped tin oxide surfaces. The spectroscopic properties of the immobilized fluorophores are studied by steady-state and time-resolved emission spectroscopy. The redox properties of the molecules are examined by electrochemical methods. It was found that the oxidation of perylene in aqueous medium results in the formation of perylenequinones. The transformation proceeds through a number of steps, with monohydroxyperylene(s) being the intermediate species. The final oxidation products are three isomeric forms of the perylenequinone/perylenehydroquinone redox couple. Understanding the mechanism of perylene transformation allows estimation of the concentration of molecules on the surface, and comparison of these results to those for pyrene and anthracene derivatives underscores the generality of this type of oxidative degradation for polycyclic aromatic hydrocarbons.