Publication
684
Org. Biomol. Chem. 9,4064-4069, 2011
DOI:10.1039/C1OB05090G
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Pyridine as proton acceptor in the concerted proton electron transfer oxidation of phenol |
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Julien Bonin, Cyrille Costentin, Marc Robert, and Jean-Michel Savéant
Laboratoire d’Electrochimie Moléculaire, UMR CNRS 7591, Université Paris Diderot, 15 rue Jean-Antoine de Baïf, 75205 Paris Cedex 13, France
Taking pyridine as a prototypal example of biologically important nitrogen bases involved in proton-coupled electron transfers, it is shown with the example of the photochemically triggered oxidation of phenol by RuIII(bpy)3 that this proton acceptor partakes in a concerted pathway whose kinetic characteristics can be extracted from the overall kinetic response. The treatment of these data, implemented by the results of a parallel study carried out in heavy water, allowed the determination of the intrinsic kinetic characteristics of this proton acceptor. Comparison of the reorganization energies and of the pre-exponential factors previously derived for hydrogen phosphate and water (in water) as proton acceptors suggests that, in the case of pyridine, the proton charge is delocalized over a primary shell of water molecules firmly bound to the pyridinium cation. |