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Proton-transfer mediated quenching of pyrene/indole charge-transfer states in isooctane solutions.

Authors
  • Altamirano, Marcela S
  • Bohorquez, María del Valle
  • Previtali, Carlos M
  • Chesta, Carlos A
Type
Published Article
Journal
The journal of physical chemistry. A
Publication Date
Jan 31, 2008
Volume
112
Issue
4
Pages
589–593
Identifiers
DOI: 10.1021/jp076294t
PMID: 18177025
Source
Medline
License
Unknown

Abstract

The fluorescence quenching of pyrene (Py) by a series of N-methyl and N-H substituted indoles was studied in isooctane at 298 K. The fluorescence quenching rate constants were evaluated by mean of steady-state and time-resolved measurements. In all cases, the quenching process involves a charge-transfer (CT) mechanism. The I(o)/I and tau(o)/tau Stern-Volmer plots obtained for the N-H indoles show a very unusual upward deviation with increasing concentration of the quenchers. This behavior is attributed to the self-quenching of the CT intermediates by the free indoles in solution. The efficiency of quenching of the polyaromatic by the N-H indoles increases abruptly in the presence of small amount of added pyridine (or propanol). A detailed analysis of the experimental data obtained in the presence of pyridine provides unambiguous evidence that the self-quenching process involves proton transfer from the CT states to indoles.

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