The electrocatalyzed reduction of fumaronitrile in aqueous solution by 4,4′-dimethyl-1,1′-trimethylene-2,2′-dipyridinium ion

Abstract

Abstract An electrocatalytic strategy for the reduction of activated olefins in aqueous solution has been demonstrated using fumaronitrile as a model olefin. Cyclic voltammetric experiments show that the reduction of fumaronitrile in pH 8.0 Tris is catalyzed by the cation radical of 4,4′-dimethyl-1,1′-trimethylene-2,2′-dipyridinium ion (DMV2+). Controlled-potential electrolysis experiments show that the electrocatalytic reduction of fumaronitrile proceeds via a two-electron two-proton pathway to form succinonitrile. Kinetic studies of the catalytic reaction by cyclic voltammetry show that the rate-determining step is the solution electron transfer from DMV·+ to fumaronitrile with a rate constant of 15 M−1 s−1. In order to understand better the general applicability of 1,1′-bridged-2,2′-dipyridinium ions as catalysts, molecular modeling was carried out on eight such ions including DMV2+. The results of these calculations were correlated with previously reported electrochemical data to show that an increase in interplanar twist angle results in a more negative E° value, apparently due to the increased importance of inter-ring conjugation in the cation radical. This understanding should aid, within limits, in the rational design of catalysts for a given olefin of interest.