Transient Absorptions over the Range 600-800 nm Observed in Flash-Photolysis of Aqueous Solutions of Indole

In the course of study on photoreduction of ferricytochrome c, transient absorptions of photolyzed indole were found over the range 600-800 nm, where usually the absorption of hydrated electrons is observed. The assignment of the absorptions was achieved by comparing the rate constants for decay of the absorptions found in this work with those for the absorptions already assigned and reported. The absorption around 720 nm observed in N2-saturated neutral solution was assigned to the electron-adduct formed by the reaction of indole with hydrated electron. In acidic solution, the absorption peak near 690 nm was observed and assigned to H-adduct of indole. The peak near 710 nm observed in N2O-saturated solution was assigned to OH-adduct, which was produced by the reaction of indole with hydroxyl radical converted from hydrated electron by the reaction with nitrous oxide.