Proton-transfer mediated quenching of pyrene/indole charge-transfer states in isooctane solutions.
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.
Altamirano
Marcela S
MS
Departamento de Química, Universidad Nacional de Río Cuarto, 5800-Río Cuarto, Argentina.
Bohorquez
María del Valle
Mdel V
Previtali
Carlos M
CM
Chesta
Carlos A
CA
D005453:Fluorescence; D007211:Indoles / Q000737:chemistry*; D015394:Molecular Structure; D009795:Octanes / Q000737:chemistry*; D011522:Protons; D011721:Pyrenes / Q000737:chemistry*; D015203:Reproducibility of Results; D012996:Solutions / Q000737:chemistry; D013050:Spectrometry, Fluorescence
D007211:Indoles; D009795:Octanes; D011522:Protons; D011721:Pyrenes; D012996:Solutions; C030374:indole; C030984:pyrene; C045798:2,2,4-trimethylpentane