Electron-transfer from excited carboxyalkylferrocenes to nitrous oxide

Abstract

When the anion Fc[CH₂]_nCO₂^–(n= 2. 3, or 4) is illuminated, in aqueous solution containing nitrous oxide, with light of wavelength ca. 240 nm, a compound is obtained whose electronic spectrum resembles that of theferricenium ion and which may be chemically reduced to the original acid. The structure assigned is that of the dipolar ion, Fc⁺[CH₂]_nCO₂^–(2). Addition of an alcohol diminishes the yield of (2). in a manner consistent with a photoexcited state undergoing three competitive processes : first-order decay to the ground electronic state, reaction with nitrous oxide to give (2), and quenching by ROH. It is deduced that the lifetime of this photoexcited state is greater than 1 µs, implying that it is probably a triplet state.