Issue 8, 2010

Reactions of excited-state benzophenone ketyl radical in a room-temperature ionic liquid

Abstract

The photochemistry of the benzophenone ketyl radical in D1 excited state, BPH(D1), was studied by means of two-color dual-pulse laser flash photolysis (355 and 532 nm) in a room-temperature ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (Bmim-TFSA), and in methanol. Upon excitation with the 532 nm pulse, BPH(D1) emitted strong fluorescence. The transient absorption and fluorescence spectra of BPH(D1) were measured with nanosecond and sub-nanosecond time resolution, respectively. The observed Stokes shift was 1700 cm−1 in Bmim-TFSA, and this shift was close to that in acetonitrile. The fluorescence lifetime of BPH(D1) was determined to be 5 ns in Bmim-TFSA, and again the value was close to that in acetonitrile. The rate constant of the reaction of BPH(D1) with CCl4 in Bmim-TFSA was determined to be (2.1 ± 0.4) × 109 M−1 s−1, which was 10 times the rate constant calculated on the basis of the bulk viscosity of Bmim-TFSA. The results are discussed in terms of the effective microscopic viscosity of the ionic liquid that was recently reported for the cage effect.

Graphical abstract: Reactions of excited-state benzophenone ketyl radical in a room-temperature ionic liquid

Article information

Article type
Paper
Submitted
29 Sep 2009
Accepted
13 Jan 2010
First published
22 Jan 2010

Phys. Chem. Chem. Phys., 2010,12, 1963-1970

Reactions of excited-state benzophenone ketyl radical in a room-temperature ionic liquid

K. Takahashi, H. Tezuka, S. Kitamura, T. Satoh and R. Katoh, Phys. Chem. Chem. Phys., 2010, 12, 1963 DOI: 10.1039/B920131A

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