Fluorescence studies in a pyrrolidinium ionic liquid: polarity of the medium and solvation dynamics

Mandal, Prasun K. ; Samanta, Anunay (2005) Fluorescence studies in a pyrrolidinium ionic liquid: polarity of the medium and solvation dynamics Journal of Physical Chemistry B, 109 (31). pp. 15172-15177. ISSN 1089-5647

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp051844d

Related URL: http://dx.doi.org/10.1021/jp051844d


While the imidazolium ionic liquids have been studied for some time, little is known about the pyrrolidinium ionic liquids. In this work, steady-state and picosecond time-resolved fluorescence behavior of three electron donor-acceptor molecules, coumarin-153 (C153), 4-aminophthalimide (AP), and 6-propionyl-2-dimethylaminonaphthalene (PRODAN), has been studied in a pyrrolidinium ionic liquid, N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, abbreviated here as [bmpy][Tf2N]. The steady-state fluorescence data of the systems suggest that the microenvironment around these probe molecules, which is measured in terms of the solvent polarity parameter, ET(30), is similar to that in 1-decanol and that the polarity of this ionic liquid is comparable to that of the imidazolium ionic liquids. All three systems exhibit wavelength-dependent fluorescence decay behavior, and the time-resolved fluorescence spectra show a progressive shift of the fluorescence maximum toward the longer wavelength with time. This behavior is attributed to solvent-mediated relaxation of the fluorescent state of these systems. The dynamics of solvation, which is studied from the time-dependent shift of the fluorescence spectra, suggests that ~45% of the relaxation is too rapid to be measured in the present setup having a time resolution of 25 ps. The remaining observable components of the dynamics consist of a short component of 115-440 ps (with smaller amplitude) and a long component of 610-1395 ps (with higher amplitude). The average solvation time is consistent with the viscosity of this ionic liquid. The dynamics of solvation is dependent on the probe molecule, and nearly 2-fold variation of the solvation time depending on the probe molecule could be observed. No correlation of the solvation time with the probe molecule could, however, be observed.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:51597
Deposited On:29 Jul 2011 04:04
Last Modified:29 Jul 2011 04:04

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