Ks. Alber et al., THE ELECTROCATALYZED REDUCTION OF FUMARONITRILE IN AQUEOUS-SOLUTION BY 4,4'-DIMETHYL-1,1'-TRIMETHYLENE-2,2'-DIPYRIDINIUM ION, Journal of electroanalytical chemistry [1992], 383(1-2), 1995, pp. 119-126
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 fu
maronitrile in pH 8.0 Tris is catalyzed by the cation radical of 4,4'-
dimethyl-1,1'-trimethylene-2,2/-dipyridinium ion (DMV(2+)). Controlled
-potential electrolysis experiments show that the electrocatalytic red
uction 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 o
f 15 M(-1) s(-1). In order to understand better the general applicabil
ity of 1,1'-bridged-2,2'-dipyridinium ions as catalysts, molecular mod
eling was carried out on eight such ions including DMV(2+). The result
s of these calculations were correlated with previously reported elect
rochemical data to show that an increase in interplanar twist angle re
sults in a more negative E degrees value, apparently due to the increa
sed importance of inter-ring conjugation in the cation radical. This u
nderstanding should aid, within limits, in the rational design of cata
lysts for a given olefin of interest.