Applications of the channel flow cell for UV‐visible spectroelectrochemical studies: The kinetics of dimerization of the methyl viologen radical cation

A channel flow cell specifically designed for ultraviolet‐visible spectroelectrochemical experiments is described. The performance of the cell was characterized using the oxidation of N,N , N ′, N ′‐tetramethyl‐ p ‐phenylenediamine in aqueous electrolytes and excellent agreement between theory and experiment was obtained. The technique was applied to study the dimerization rate of methyl viologen radical cations. The mechanistic results confirm that the electrogenerated methyl viologen radical cation dimerizes rapidly in aqueous solution and a previously unknown dimerization rate constant close to 10 4 M −1 s −1 is reported.