Formation of π-excimer or π-exciplex in electrogenerated chemiluminescence involving perylene molecule revealed using a dual-electrolysis stopped-flow method

Abstract

Electrogenerated chemiluminescence (ECL) reactions involving the perylene cation radical (PE + ) and perylene anion radical (PE − ) in acetonitrile have been observed using a dual-electrolysis stopped-flow method. In this method, ECL emission from the systems composed of different kinds of ion radicals can be easily observed by mixing both the electrolyzed solutions directly. Therefore, the ECL spectra were observed systematically in the reactions of PE + and PE − with different ion radicals. Consequently, emission definitely from the singlet state of PE was observed in the reactions between PE + and the 9,10-diphenylanthracene anion radical (DPA − ), PE − and DPA + , and PE − and the thianthrene cation radical (TH + ). In contrast, emission at long wavelength was obtained in the reaction between PE + and the pyrene anion radical (PY − ) as well as the reaction between PE + and PE − . From this result, for the molecular interactions involving PE and PY, the presence of the π complexing interaction to form the π-excimer and the π-exciplex was strongly suggested in the ECL-emitting reactions. The present approach was thus found to be effective to reveal the molecular aspects of the excited states formed in solution.