Electron-Transfer Stopped-Flow Method: Its Validity for Spectrochemical Analysis of Electrogenerated Cation Radicals

Abstract

The reaction of 4-bromo-N,N-dimethylaniline cation radical was studied using an electron-transfer stopped-flow (ETSF) method. In the ETSF method, was generated via the electron-transfer reaction between DMABr and tris (p-bromophenyl)amine cation radical. Thus, the influence of the concentration of DMABr on the reaction of was easily observed by controlling the concentrations in the mixed solutions. As a consequence, diverse changes in the absorption spectra were observed involving the formation of the cation radical and dication of the dimer compound, tetramethylbenzidine (TMB), depending on the concentration of DMABr. When only was formed, the reaction was assigned to the simple formation of This reaction was first order in and the rate constant was determined to be 0.20 s−1. In contrast, when a large excess of DMABr was also present, the rapid and quantitative formation of was observed via the reaction expressed by The validity of the ETSF method for spectrochemical analysis of electrogenerated cation radicals is demonstrated by analyzing the present reactions. © 2001 The Electrochemical Society. All rights reserved.