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Updated: Jul 8, 2026

Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
Published on: July 19, 2019
Proton-transfer mediated quenching of pyrene/indole charge-transfer states in isooctane solutions
Marcela S Altamirano1, María del Valle Bohorquez, Carlos M Previtali
1Departamento de Química, Universidad Nacional de Río Cuarto, 5800-Río Cuarto, Argentina.
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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