The laser versus the lamp: Reactivity of the diphenyl ketyl radical in the ground and excited states

Baumann, H.; Merckel, C.; Timpe, H.‐J.; Graneß, Angela; Kleinschmidt, J.; Gould, Ian R.; Turro, Nicholas J.

doi:10.1016/0009-2614(84)85285-9

Cited by 50 publications

(25 citation statements)

References 21 publications

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“…It has been reported that 1 H . (D 1 ) reacts with amine,3g and it was found that the τ f values of 1 H . (D 1 ) decreased with an increase of the concentration of 1 (S 0 ).…”

Section: Resultsmentioning

confidence: 99%

Properties of Excited Ketyl Radicals of Benzophenone Analogues Affected by the Size and Electronic Character of the Aromatic Ring Systems

Sakamoto

Cai

Fujitsuka

et al. 2006

Chemistry A European J

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The properties of benzophenone ketyl radical analogues with large aromatic ring systems, such as naphthylphenylketone (2), 4-benzoylbiphenyl (3), and bis(biphenyl-4-yl)methanone (4), were investigated in the excited state by using nanosecond-picosecond two-color two-laser flash photolysis. Fluorescence and transient absorption spectra of ketyl radicals of 2-4 in the excited state were observed for the first time. The fluorescence and properties of the excited ketyl radicals were significantly affected by the size and electronic properties of the aromatic ring systems. The reactivity of the ketyl radicals in the excited state with several quenchers was examined and they were found to show reactivity toward N,N-diethylaniline. In addition, for the benzophenone ketyl radical, a unique quenching process of the radical in the excited state by the ground-state parent molecule was found. The factors regulating the fluorescence lifetime of the ketyl radicals in the excited state are discussed quantitatively.

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“…It has been reported that 1 H . (D 1 ) reacts with amine,3g and it was found that the τ f values of 1 H . (D 1 ) decreased with an increase of the concentration of 1 (S 0 ).…”

Section: Resultsmentioning

confidence: 99%

Properties of Excited Ketyl Radicals of Benzophenone Analogues Affected by the Size and Electronic Character of the Aromatic Ring Systems

Sakamoto

Cai

Fujitsuka

et al. 2006

Chemistry A European J

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“…Fluorescence from the diphenylketyl radical or benzophenone ketyl radical has been studied in order to investigate the photophysics and photochemistry of the exciteddoublet state. 15,20,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] The fluorescence decay time and quantum yield of the ketyl radical of benzophenone in toluene have been measured and were found to be τ f ) 3.9 ns 32 and Φ f ) 0.11, 38 respectively. The fluorescence decay time of the radical in more polar solvents is comparable (e.g., τ f ) 3.7 ns in acetonitrile 28 ), so the fluorescence quantum yield should also be significant in these solvents.…”

mentioning

confidence: 99%

Time-Resolved Fluorescence Monitoring of Aromatic Radicals in Photoinitiated Processes

Shield

Harris

1998

Anal. Chem.

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Photolytic initiation of free radical reactions is important to many areas of technology; time-resolved monitoring of submicromolar concentrations of radicals produced during the course of these reactions is needed to provide information about the rate of initiation and its competition with radical recombination. In this work, time-resolved laser-induced fluorescence is evaluated for monitoring of diphenylketyl radicals produced by photoreduction of the triplet state of benzophenone. Fluorescence from the doublet-doublet transition of the radical is excited with a continuous wave laser and provides a sensitive method to detect these intermediates at nanomolar concentrations and to study their kinetics in solution on time scales from a few microseconds to hundreds of milliseconds. The ketyl radical fluorescence measurements of radical initiation reactions allowed the H atom abstraction rate constant by triplet benzophenone from both 2-propanol and benzhydrol to be determined, where k(H) = (2.1 ± 0.1) × 10(6) M(-)(1) s(-)(1) for 2-propanol and k(H) = (4.4 ± 0.1) × 10(6) M(-)(1) s(-)(1) for benzhydrol. The diphenylketyl radical recombination rate constant was also determined by time-resolved fluorescence monitoring of the decay of the radical population and found to be k(r) = (1.9 ± 0.2) × 10(8) M(-)(1) s(-)(1). Formation kinetics could be measured on a microsecond time scale from radical populations as low as 45 nM; decay kinetics could be followed on a millisecond time scale from 20 nM radical concentrations.

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“…About 30 μs later the peaks disappeared completely, which consists with benzophenone excited triplet state characteristic absorption peaks reported in literatures. [12][13][14] According to the quantum chemistry calculations, these two peaks belong to the benzophenone triplet state ( 3 BP * ) absorption. Figure. 1.…”

Section: Density Functional Theory (Dft) Computationsmentioning

confidence: 99%

Phototransformation mechanism of monuron induced by the triplet benzophenone in aqueous solution

Zheng

Pei

2015

J. Phys. Org. Chem.

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Phototransformation mechanism of monuron induced by the triplet benzophenone in aqueous solution was investigated by laser flash photolysis technique, while quenching of the triplet benzophenone by monuron was studied by nanosecond transient absorption spectroscopy. The transient species in the transient absorption spectra have been identified by quantum chemistry calculations. The results show that under 355-nm irradiation proton transfer between the triplet benzophenone and monuron happens, and monuron radical is formed and followed by dechlorination degradation reactions. This work indicated that in aqueous solution some dissolved natural organic matters are helpful to degradation of the organic pollutants under the sunlight.

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The laser versus the lamp: Reactivity of the diphenyl ketyl radical in the ground and excited states

Cited by 50 publications

References 21 publications

Properties of Excited Ketyl Radicals of Benzophenone Analogues Affected by the Size and Electronic Character of the Aromatic Ring Systems

Properties of Excited Ketyl Radicals of Benzophenone Analogues Affected by the Size and Electronic Character of the Aromatic Ring Systems

Time-Resolved Fluorescence Monitoring of Aromatic Radicals in Photoinitiated Processes

Phototransformation mechanism of monuron induced by the triplet benzophenone in aqueous solution

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