Disproportionation of a 2,2-diphenyl-1-picrylhydrazyl radical as a model of reactive oxygen species catalysed by Lewis and/or Brønsted acids

Abstract

Electron-transfer disproportionation of a 2,2-diphenyl-1-picrylhydrazyl radical (DPPH˙) occurred in the presence of Sc³⁺ acting as a strong Lewis acid in deaerated acetonitrile. In contrast, in the case of weaker Lewis acids than Sc³⁺, such as Mg²⁺ and Li⁺, external protons from acetic acid were required for the disproportionation of DPPH˙ to occur.