Electrochemistry in tetrahydrofuran and at low temperature: protocol,procedures and methods

This review describes the protocol, procedures and methods for electrochemical studies in THF and at low temperature that have been developed in the course of the last 5 years in our laboratory. Electrochemical studies in THF benefit from a large accessible potential window. In practice, it is however necessary to avoid the presence of humidity in the electrochemical cell. A specific reference electrode had to be designed for those measurements. Microelectrodes, the voltammetric response of which is negligibly affected by the resistivity of the medium, were preferred to macroelectrodes. Moreover, a methodology has been developed for the quantitative analysis of both voltammetric and chronoamperometric curves obtained for the microelectrodes. The fitting of chronoamperometric measurements using the Shoup and Szabo's expression allows us to estimate the diffusion coefficient of the substrate. The modelling of the cyclic voltammograms measured over a large range of scan rates allows the confirmation of the diffusion coefficient of the substrate D_A, the determination of the diffusion coefficient of the electrogenerated molecule D_B, of the formal potential E, of the transfer coefficient α and of the standard heterogeneous rate constant for the electron transfer k₀. Typically, systems are investigated at temperatures ranging from room temperature to 192 K. Parameters obtained at various temperatures are used to extract, through Arrhenius plots, the activation energies both for the diffusion coefficient E_A(D) and for the electron transfer reaction E_A(k₀). Copyright © 2009 John Wiley & Sons, Ltd.