Excited-state proton-transfer dynamics of 7-hydroxyquinoline in room temperature ionic liquids

Bhattacharya, Bhaswati ; Samanta, Anunay (2008) Excited-state proton-transfer dynamics of 7-hydroxyquinoline in room temperature ionic liquids Journal of Physical Chemistry B, 112 (33). pp. 10101-10106. ISSN 1089-5647

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp802930h

Related URL: http://dx.doi.org/10.1021/jp802930h

Abstract

Excited-state proton transfer (ESPT) reaction of 7-hydroxyquinoline (7-HQ) mediated by methanol molecules has been studied in two room temperature ionic liquids (RTILs) using steady-state and time-resolved fluorescence measurements. While no ESPT is observable in neat RTILs, characteristic tautomer fluorescence of 7-HQ could be observed in the presence of small quantity of methanol (0.5-4.1 M). The observation of a rise time (350 ps-1.4 ns) associated with the tautomer fluorescence suggests that proton transfer in 7-HQ is indeed an excited-state phenomenon that requires considerable solvent reorganization prior to the relay of proton from the hydroxyl group to the distant ring nitrogen atom through suitably organized dimeric chain of methanol molecules. The rise time of the tautomer fluorescence, which has been found to decrease with increasing methanol concentration, is attributed to the change of viscosity of the medium upon methanol addition. While the influence of viscosity on the ESPT kinetics is evident from the data, lack of any definite correlation between the bulk viscosity and the rise time has been interpreted in terms of the microheterogeneous nature of the media that does not allow assessment of the microviscosity around 7-HQ from the bulk viscosity.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:51610
Deposited On:29 Jul 2011 04:06
Last Modified:29 Jul 2011 04:06

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