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

Takahashi, Kenji; Tezuka, Hiroaki; Kitamura, Shingo; Satoh, Toshifumi; Katoh, Ryuzi

doi:10.1039/b920131a

Cited by 13 publications

(17 citation statements)

References 72 publications

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“…The k T-T values were experimentally obtained from the decay of 3 BP* observed at 610 nm to avoid contribution of BPH . The DA(t) curves were simulated by the Levenberg-Marquardt nonlinear least squares method with eqn (15). The fitting parameters are a 0 and k RP .…”

Section: Cage Lifetimes Of Ionic Liquidsmentioning

confidence: 99%

“…48 In the report, the cage effects were found to increase with increasing macroviscosity from Emim BF 4 to PP13 TFSA. 47 The extensive studies on the nanoscale ordering structures of ILs have been reported, [8][9][10][11][12][13][14][15] however, the cage lifetime has not been reported until now. To the best of our knowledge, this is the first report on the cage lifetime of ILs.…”

Section: Cage Lifetimes Of Ionic Liquidsmentioning

confidence: 99%

“…Ionic liquids (ILs) are currently a promising new class of solvents in green chemistry, electrochemistry, and nanochemistry, because of their exceptional combination of properties: nonvolatility, noncorrosiveness, nonflammability, stability to air and moisture, and designability, and provide new environments for chemical reactions. [1][2][3][4][5][6][7] Although a number of studies on their structures and functions have been reported, [8][9][10][11][12][13][14][15] the mechanistic insight into chemical reactions in ILs is still unclear because of the complex solvent structures in ILs. Especially, it has been reported that the ILs have nanoscale ordering structures as a result of the strong coulombic interactions and the aggregation of the nonpolar parts of ionic molecules.…”

Section: Introductionmentioning

confidence: 99%

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Cage lifetimes of ionic liquids as studied by the magnetic field effect probe

Okada

Yago

Takamasu

et al. 2012

Phys. Chem. Chem. Phys.

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Magnetic field effects (MFEs) on the photoinduced hydrogen abstraction reaction of benzophenone with phenol were investigated in ionic liquids (ILs) with a short alkyl chain (N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)amide (TMPA TFSA)) and long alkyl chains ((N,N,N-trimethyl-N-octylammonium bis(trifluoromethanesulfonyl)amide (TMOA TFSA) and N-decyl-N,N,N-trimethylammonium bis(trifluoromethanesulfonyl)amide (DTMA TFSA)) by a nanosecond laser flash photolysis technique. In each ionic liquid, escaped radical yield of a benzophenone ketyl radical rapidly increased with increasing magnetic field strength (B) of 0 T < B≤ 0.01 T. At 0.01 T < B≤ 0.4 T, the escaped radical yield almost saturated in TMPA TFSA or gradually increased in TMOA TFSA and DTMA TFSA. At much higher fields of 0.4 T < B≤ 30 T, the yield gradually decreased, resulting in 10-15% decrease at 30 T. The observed MFEs can be explained by the hyperfine coupling and Δg mechanisms together with the relaxation mechanism. On the time profiles of the transient absorption observed for the benzophenone ketyl radical, MFEs were generated in the time range of 0 < t < 0.6 μs. The cage lifetimes of TMOA TFSA and DTMA TFSA were estimated to be at least 120 ns.

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Section: Cage Lifetimes Of Ionic Liquidsmentioning

confidence: 99%

Section: Cage Lifetimes Of Ionic Liquidsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cage lifetimes of ionic liquids as studied by the magnetic field effect probe

Okada

Yago

Takamasu

et al. 2012

Phys. Chem. Chem. Phys.

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“…In particular, diffusion/mobility-controlled processes in ILs may proceed noticeably different compared to common organic solvents, ultimately leading to a change of the reaction pathways and the products formed. 13,14 Heterogeneities and nanostructuring of ILs have been of great interest for both experimental and theoretical studies. [5][6][7][8][9][10][11][12] It was found that charged cationic head groups and anions aggregate in polar nano-domains, whereas hydrophobic alkyl tails of cations aggregate in non-polar nanodomains.…”

Section: Introductionmentioning

confidence: 99%

Probing Microenvironment in Ionic Liquids by Time-Resolved EPR of Photoexcited Triplets

et al. 2015

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Unusual physicochemical properties of ionic liquids (ILs) open vistas for a variety of new applications. Herewith, we investigate the influence of microviscosity and nanostructuring of ILs on spin dynamics of the dissolved photoexcited molecules. We use two most common ILs [Bmim]PF6 and [Bmim]BF4 (with its close analogue [C10mim]BF4) as solvents and photoexcited Zn tetraphenylporphyrin (ZnTPP) as a probe. Time-resolved electron paramagnetic resonance (TR EPR) is employed to investigate spectra and kinetics of spin-polarized triplet ZnTPP in the temperature range 100-270 K. TR EPR data clearly indicate the presence of two microenvironments of ZnTPP in frozen ILs at 100-200 K, being manifested in different spectral shapes and different spin relaxation rates. For one of these microenvironments TR EPR data is quite similar to those obtained in common frozen organic solvents (toluene, glycerol, N-methyl-2-pyrrolidone). However, the second one favors the remarkably slow relaxation of spin polarization, being much longer than in the case of common solvents. Additional experiments using continuous wave EPR and stable nitroxide as a probe confirmed the formation of heterogeneities upon freezing of ILs and complemented TR EPR results. Thus, TR EPR of photoexcited triplets can be effectively used for probing heterogeneities and nanostructuring in frozen ILs. In addition, the increase of polarization lifetime in frozen ILs is an interesting finding that might allow investigation of short-lived intermediates inaccessible otherwise.

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“…[1][2][3][4][5][6][7] ILs also provide new environments for chemical reactions with applications in many fields, such as catalysis, synthesis, electron transport, polymerization, and formation of nanomaterials. Although a number of studies on the structure of ILs have been reported, [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] the mechanistic details of chemical reactions in ILs remain relatively unstudied owing to ILs' tendency to form complex structures, such as nanoscale ordering structures. We have also studied the nanoscale ordering structures of ILs by the magnetic field effect probe (MFE probe).…”

Section: Introductionmentioning

confidence: 99%

Local structure of ionic liquids probed by self-quenching of thiobenzophenone

Tanaka

Yago

Wakasa

2013

Phys. Chem. Chem. Phys.

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Self-quenching of the triplet excited state of thiobenzophenone ((3)TBP*) in molecular solvents, a sodium dodecyl sulfate (SDS) micellar solution, and ionic liquids (ILs) was measured using nanosecond laser flash photolysis. In the molecular solvents and ILs, (3)TBP* single-exponentially decayed, and the decay was accelerated with increasing TBP concentration. Self-quenching rate constants (k(SQ)) obtained in the ILs were smaller than those in the molecular solvents with similar solvent viscosities, indicating that molecular diffusion is inhibited in the ILs. In the SDS micellar solution, the decay of (3)TBP* showed two components. The fast decay component was attributed to self-quenching of (3)TBP* which presents inside micelles containing two or more TBP molecules, while the slow decay component was from deactivation of single (3)TBP*. The decay of (3)TBP* in an IL, N,N,N-trimethyl-N-propylammonium bis(trifluoromethylsulfonyl)amide (TMPA TFSA), had only one decay component, showing that unlike the micelles, the local structure of TMPA TFSA does not have a long lifetime. The cage lifetime of TMPA TFSA was estimated to be between 17 and 20 ns.

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

Abstract: The photochemistry of benzophenone ketyl radical in the D 1 excited state, BPH(D 1 ), was studied by means of two-color dual-pulse laser flash photolysis (355 and 532

Cited by 13 publications

References 72 publications

Cage lifetimes of ionic liquids as studied by the magnetic field effect probe

Cage lifetimes of ionic liquids as studied by the magnetic field effect probe

Probing Microenvironment in Ionic Liquids by Time-Resolved EPR of Photoexcited Triplets

Local structure of ionic liquids probed by self-quenching of thiobenzophenone

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