Cyclic and normal pulse voltammetric studies of 2,3,6,7,10,11-hexaphenylhexazatriphenylene using a benzonitrile thin layer-coated glassy carbon electrode

The method of interposing a thin layer of immiscible organic solvent (benzonitrile, BN) between a glassy carbon electrode surface and an aqueous solution has been successfully applied to study the electrode reaction of a highly hydrophobic organic molecule, 2,3,6,7,10,11-hexaphenylhexazatriphenylene (HAT). Four couples of well-defined redox peaks of HAT were observed at the BN thin layer-coated electrode in N₂-saturated 2 M HClO₄ aqueous solution. By cyclic voltammetry, square-wave voltammetry, and normal pulse voltammetry, the thermodynamic and kinetic parameters (i.e., the formal potential, standard rate constant, and cathodic transfer coefficient) for the multistep redox reaction of HAT and its diffusion coefficient were evaluated. The good agreement between the observed normal pulse voltammograms and the calculated one with use of the obtained kinetic and thermodynamic parameters demonstrated that the evaluated parameters are reasonable and that the present approach is useful in the kinetic study of the multistep redox reaction of hydrophobic reactants. A probable reaction mechanism for the whole redox reaction of HAT was also proposed.