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Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/10054/3840

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
Authors: MUKHERJEE, TK
PANDA, D
DATTA, A
Keywords: normalized emission-spectroscopy
intramolecular charge-transfer
photoinduced electron-transfer
solvation dynamics
7-azaindole dimer
fluorescence-spectra
dual fluorescence
mixed-solvents
hydrogen-bond
atom transfer
Issue Date: 2005
Publisher: AMER CHEMICAL SOC
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.
URI: http://dx.doi.org/10.1021/jp052917w
http://dspace.library.iitb.ac.in/xmlui/handle/10054/3840
http://hdl.handle.net/10054/3840
ISSN: 1520-6106
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