Analysis of Electron Transfer Reactions in Solution with the Development of High-Sensitive Detection Method for Electrogenerated Chemiluminescence using Flow-Electrolysis.

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New method for the measurement of electrogenerated chemiluminescence (ECL) was developed by using a pulse-electrolysis stopped-flow method. While numerous studies have been devoted to the ECL caused in the reactions between cation and anion radicals of aromatic substances in aprotic solvents, the ECL reactions ever observed have been resticted to the systems having a smaller redox potential differences than those of a molecule concerned. These are so called "energy deficient" systems. By contrast, for example, the pure reaction between diphenylanthracene (DPA) cation radical and pyrene (PY) anion radical has been very difficult to be observed in the conventional methods because of the interference by the reduction of DPA which is concurrent with the reduction of PY.Although this sort of "energy sufficient" reaction has never been observed, its measurement will be effective to study the emission directly from the singlet state (S-route) and to obtain the information on the excited states explicity. In the present work, the ECL measurement on the energy sufficient systems composed of different kind of ion radicals has become possible by using a pulse-electrolysis stopped-flow apparatus having two electrolysis lines. In this apparatus, by generating cation radicals and anion radicals independently, the ECL is observed in an optical cell. Therefore, various reactions of the energy sufficient systems composed of different kind of ion radicals can be targeted including sort-lived species. In the reaction between thianthrene cation radical and PY anion radical, it was found that the emision spectra changed with the addition of the precursors reflecting the complex electron and energy transfers in solution. In addition, the emitting properties was clarified to depend on the sort of the molecules significantly through the measurements in which three Components were mixed.