Photodegradation of the Imidazole Ring Induced by Indole Derivatives in Oxygen‐free Aqueous Solutions

An imidazole ring photodegradation induced by indole derivatives in oxygen‐free aqueous solutions (Λ exc = 254 nm) was demonstrated and studied in various systems at low concentration (0.2 m M ). The degradation rate was maximal in the indole‐imidazole system and decreased when a substituent was present on either or both rings. The degradation rate also depended on pH (maximal at pH ˜ 6) and on imidazole concentration. Results obtained under N 2 O atmosphere, in the presence and absence of 1 M t ‐butanol, indicate that the imidazole degradation is promoted by hydrated electrons photogenerated by the indole chromophore. Kinetic analysis of the data confirms this mechanism.