Campus Units

Chemistry

Document Type

Article

Publication Version

Published Version

Publication Date

3-1993

Journal or Book Title

Journal of Physical Chemistry

Volume

97

Issue

9

First Page

1770

Last Page

1780

DOI

10.1021/j100111a011

Abstract

A study of the fluorescence lifetimes and quantum yields of 7-azaindole and its methylated derivatives NImethyl- Famindole (1 M7AI) and 7-methyl-7H-pyrrolo[ 2,341 pyridine (7M7AI) in water is performed in order to explain the observation that the fluorescence spectrum of 7-azaindole apparently consists of one band (A, = 386 nm) whereas in alcohols the spectrum is bimodal (e.g., for methanol, A,, = 374, 505 nm). Careful measurements of the fluorescence decay as a function of emission wavelength indicate a small amplitude of an -70-ps decaying component at the bluer wavelengths and a rising component of the same duration at the redder wavelengths. The small amplitude component, which comprises no more than 20% of the fluorescence decay, is attributed to excited-state tautomerization that is mediated by the solvent. Particular attention is paid to the pH dependence of the fluorescence lifetimes and yields. We propose that upon tautomerization the basic l-nitrogen (NIo)f 7-azaindole is rapidly protonated givingrise to a species whose emission maximum is at -440 nm. The fluorescence emission maximum and lifetime of 7-azaindole is dominated by the 80% of the solute molecules that are blocked by unfavorable solvation from executing excited-state tautomerization. It is proposed that 210 ns is required for the surrounding water molecules to attain a configuration about 7-azaindole that is propitious for tautomerization.

Comments

Reprinted (adapted) with permission from Journal of Physical Chemistry 97 (1993): 1770, doi: 10.1021/j100111a011. Copyright 1993 American Chemical Society.

Copyright Owner

American Chemical Society

Language

en

File Format

application/pdf

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