Please use this identifier to cite or link to this item:
Title: Excited-state proton transfer of 2-(2 '-pyridyl)benzimidazole in microemulsions: Selective enhancement and slow dynamics in aerosol OT reverse micelles with an aqueous core
Keywords: Normalized Emission-Spectroscopy
Intramolecular Charge-Transfer
Photoinduced Electron-Transfer
Solvation Dynamics
7-Azaindole Dimer
Dual Fluorescence
Atom Transfer
Issue Date: 2005
Citation: JOURNAL OF PHYSICAL CHEMISTRY B, 109(40), 18895-18901
Abstract: Excited-state proton transfer (ESPT) of 2-(2'-pyridyl)benzimidazole (2PBI) in reverse micelles has been studied by steady-state and time-resolved fluorescence spectroscopy. The nanometer sized water pool in the n-heptane/Aerosol OT (AOT)/water microemulsion is found to promote tautomer emission of this probe, as is evident from the emergence of a Stokes shifted band at 450 nm at the expense of the normal emission band on increasing the water content of the system. In the nonaquous microemulsion with a methanol core, the normal emission is quenched but no tautomer emission is obtained. With an acetonitrile core, there is no change in emission properties. Similarly, there is no evidence of ESPT in Triton X-100 reverse micelles. This indicates the requirement of ESPT to occur in microheterogeneous media; the medium should be a ternary system comprised of water and a hydrophobic phase separated by a negatively charged interface. In the microemulsions with an aqueous core, the fluorescence decays of 2PBI at the red end exhibit rise times of 0.8 ns and the time-resolved area-normalized emission spectra (TRANES) exhibit an isoemissive point, indicating slow dynamics of the two-state ESPT of 2PBI in aqueous ACT reverse micelles. The origin of the selective enhancement in AOT microemulsions as well as the slow dynamics is explored using fluorescence spectroscopic techniques, with support from quantum chemical calculation.
ISSN: 1520-6106
Appears in Collections:Article

Files in This Item:
There are no files associated with this item.

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.