Excited-state tautomerization of 7-azaindole in water

Curtis F. Chapman, Mark Maroncelli

Research output: Contribution to journalArticle

129 Citations (Scopus)

Abstract

We have studied the solvent dependence of the steady-state absorption, emission, and time-resolved emission of 7-azaindole (7AI) and two nonreactive analogues, N-methyl-7-azaindole (NMAI) and 7-methyl-7H-pyrrolo[2,3-b]pyridine (7MPP), in an effort to understand the apparently anomalous behavior of 7AI in water. We find that 7AI undergoes the same tautomerization reaction via solvent-catalyzed double proton transfer in water as it does in alcohol solvents. Kinetic modeling shows that the unusual features of the 7AI emission in water arise mainly from quantitative changes in two key rate parameters. In water the rate constant for tautomerization (H2O 1.2 × 109 s-1 and D2O 0.35 × 109 s-1 at 24°C) is much slower and simultaneously the nonradiative decay rate of the product is much faster (5 × 109 s-1 in both H2O and D2O) than in most alcohols, making observation of the reaction difficult. The reason the reaction rate in water is unusually slow appears to result from differences in the hydrogen bonding structure and dynamics of water compared to monoalcohols.

Original languageEnglish (US)
Pages (from-to)8430-8441
Number of pages12
JournalJournal of Physical Chemistry
Volume96
Issue number21
DOIs
StatePublished - Jan 1 1992

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Excited states
Water
water
excitation
alcohols
Alcohols
Proton transfer
Pyridine
decay rates
Reaction rates
7-azaindole dimer
Rate constants
pyridines
Hydrogen bonds
reaction kinetics
analogs
Kinetics
protons
kinetics
hydrogen

All Science Journal Classification (ASJC) codes

  • Engineering(all)
  • Physical and Theoretical Chemistry

Cite this

Chapman, Curtis F. ; Maroncelli, Mark. / Excited-state tautomerization of 7-azaindole in water. In: Journal of Physical Chemistry. 1992 ; Vol. 96, No. 21. pp. 8430-8441.
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Excited-state tautomerization of 7-azaindole in water. / Chapman, Curtis F.; Maroncelli, Mark.

In: Journal of Physical Chemistry, Vol. 96, No. 21, 01.01.1992, p. 8430-8441.

Research output: Contribution to journalArticle

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