Electrochemical one-electron reduction of the "extended viologen" dication 1(2+) proceeds reversibly at -0.64 V (vs Ag vertical bar AgCl electrode) to yield the red cation radical 1(+center dot), which readily produces a dark-blue dimer hindering the observation of the one-electron reduction of 1(+center dot). The second reduction step at -1.4 V seen by conventional electrochemical methods then corresponds to the reduction of a dimer (1 - 1)(2+). Fast cyclic voltammetry at scan rates up to kV/s and voltammetry at micromolar concentrations eliminate the coupled bimolecular chemical reactions and permit the determination of the reduction potential of the cation radical 1(+center dot). (c) 2006 The Electrochemical Society.