Electrochemical and ESR Studies of the Methane C-H Bond Activation in the Presence of Radical Cations of Pyrazine-di-N-oxide and its Substituted Derivativesстатья
Аннотация:Activation of the methane C-H bond in the presence of electrochemically generated radical cations of pyrazine-di-N-oxide and also of 2,5-dimethyl- and 2,3,5,6-tetramethyl-pyrazine-di-N-oxides is studied by methods of cyclic voltammetry (CVA) , quantum chemical simulations, and ESR electrolysis. The studies are carried out on glassy carbon (GC) and Pt electrodes in 0.1 M LiClO4 solutions in acetonitrile. ESR spectra of radical cations of aromatic di-N-oxides in the absence and in the presence of methane are recorded. The changes in the shape CVA curves and the intensity of ESR signals of di-N-oxide radical cations observed in the presence of methane point to the activation of the methane C-H bond followed by its oxidation. The reaction of pyrazine-di-N-oxide with the methane C-H bond is simulated by quantum chemical methods. The obtained results are explained within the framework of the mechanism of overall two-electron oxidation of methane within its complex with an aromatic di-N-oxide radical cation.