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Pairing effect: Varying the concentration of support electrolyte in the electrochemical EC 2 reduction of 2,6-diphenylpyrylium reveals the presence of ion pairing between the electroactive species and BF 4-. Experiment and theory are shown to be in good agreement only if ion pairing is included in the simulations. This previously unanticipated effect is only observable if voltammetry is performed under conditions of weak support. Copyright © 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.

The reduction of 2-nitrobromobenzene in acetonitrile has been studied in the presence and near absence of supporting electrolyte at a mercury hemispherical microelectrode. In the presence of a high concentration of tetra-n-butylammonium perchlorate, voltammetric studies over a wide range of voltage scan rates spanning the transition from convergent to linear diffusion confirms the reduction mechanism as DISP1, rather than ECE, as previously thought by the majority of earlier studies. A rate constant of approximately 23 s-1 at 298 K was inferred for the loss of bromide ion from the 2-nitrobromobenzene radical anion. In the presence of weak support, with concentration ratios of electrolyte to reactant of 5 and 0.5, the Nernst-Planck-Poisson system of equations were used to model the coupled diffusion-migration-reaction. It was found the both the mechanism of reaction and the derived homogeneous kinetics were unchanged in the near absence of supporting electrolyte. © 2011 Elsevier B.V. All rights reserved.