SOLVATION OF 7-AZAINDOLE IN ALCOHOLS AND WATER - EVIDENCE FOR CONCERTED, EXCITED-STATE, DOUBLE-PROTON TRANSFER IN ALCOHOLS

The proton inventory technique is used for the first time to investigate excited state proton-transfer processes. The nonradiative pathways of the biological probe, 7-azaindole, in methanol, ethanol, and water are examined. Results in methanol and ethanol demonstrate the involvement of two protons in the transition state for the excited-state double-proton transfer process. These data provide the first experimental evidence suggesting a concerted tautomerization reaction of 7-azaindole in alcohols. The data for 7-azaindole in water are interpreted in terms of a nonradiative pathway that is qualitatively different from that in alcohols. We propose abstraction of the N1 hydrogen by water as a possible nonradiative decay process.