We compare the electron transfer (ET) rates of hydroquinone self-assembled monolayers (SAMs) on gold electrodes containing either an alkane or pi-delocalized oligo(phenylene vinylene) (OPV) bridge at basic pH (between pH 8 and 12.6). The hydroquinone SAMs were diluted with octane-l-thiol. Cyclic voltammograms of the quinone/hydroquinone (Q/H(2)Q) couple allowed the peak-to-peak separation of the anodic and catholic peak potentials to be analyzed and apparent rate constants (k(app)) to be determined using Laviron's formalism. We found that a simple rate law containing one equilibrium constant (K-AH) and two rate constants (k(AH) and k(A)) describes the dependence of k(app) as a function of pH. From this model, the ratio of the rate constants for the protonated form H(2)Q, k(AH) ((opv))/k(AH) ((alk)) was similar to 800, and the ratio of the de-protonated form, HQ(-), k(A(OPV))/k(A(alk)) was similar to 2. The large ratio at pH < pK(AH) suggests that, for protonated H(2)Q, the ability of the OPV bridges to tunnel electrons significantly affects the overall rate. The small ratio at strongly basic pH (> K-p(AH)) implies that, for the de-protonated form HQ-, the overall ET rate is less sensitive to the bridge. (c) 2007 Elsevier B.V. All rights reserved.