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Title: Regulation of the extent and dynamics of excited-state proton transfer in 2-(2 '-pyridyl)benzimidazole in Nafion membranes by cation exchange
Keywords: Photoinduced Electron-Transfer
Normalized Emission-Spectroscopy
Perfluorinated Ionomer Membranes
Perfluorosulfonate Ionomer
Selective Enhancement
Luminescence Probe
Dual Fluorescence
7-Azaindole Dimer
Issue Date: 2006
Citation: JOURNAL OF PHYSICAL CHEMISTRY B, 110(6), 2611-2617
Abstract: The effect of the microenvironment of a Nafion membrane on the excited-state proton transfer (ESPT) of 2-(2'-pyridyl)benzimidazole (2PBI) has been investigated by steady-state and time-resolved fluorescence spectroscopy. The mechanism of the ESPT is found to depend remarkably on the water content of the membrane. In the protonated form of the membrane, ESPT is found to involve the dicationic (D) form of the fluorophore, whereas in cation-exchanged membranes, it is found to involve the monocation (C). The change in the mechanism and extent of ESPT in cation-exchanged membranes can be explained by considering dehydration of the membrane as well as the less acidic environment around the 2PBI molecules. The slow dynamics is found to result from two factors, namely, slow and incomplete solvation of the transition state, leading to a slowing down of the proton-transfer process, and a slow solvation of the polar tautomeric excited state.
ISSN: 1520-6106
Appears in Collections:Article

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