Solvation and excited-state proton transfer of 7-azaindole in alcohols

✍ Scribed by Y. Chen; F. Gai; J.W. Petrich

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 562 KB
• Volume: 222
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(94)87069-1

✦ Synopsis

Fluorescence lifetime measurements of purified 7-azaindole in methanol and butanol as a function of temperature are performed. The results indicate that in alcohols there exists a population of 'I-azaindole that is solvated in such a way that excitedstate tautomerixation is no longer a viable mode of nonradiative decay, that is, in a way that has been observed for water but to a lesser extent. Solvation by alcohols or by water is thus more similar than has been previously proposed. An excellent correlation is demonstrated between the time constant for double-proton transfer and pKaUto, where K.,,, is the autoprotolysis constant of the solvent. This correlation, along with earlier results, suggests that the actual proton-transfer event, and not the solvation step forming the necessary cyclic hydrogen-bonded complex, is the rate-limiting step in dilute solutions of 'I-axaindole.