Fluorescence of the benzophenone ketyl radical: solvent effects

Yankov, P.; Nickolov, Zh.; Zhelyaskov, V.; Петков, Иван

doi:10.1016/1010-6030(89)87061-3

Cited by 9 publications

(6 citation statements)

References 14 publications

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“…Under excitation BP converts to the biradical triplet state, in which it abstracts hydrogen atom from aliphatic alcohols with the formation of two ketyl-radicals. They undergo protolytic dissociation, and the radical anion, which has a very high negative electrochemical potential, may be the true reductant [7,20,21].…”

Section: Resultsmentioning

confidence: 99%

Structure and spectra of photochemically obtained nanosized silver particles in presence of modified porous silica

Krylova

Eremenko

Smirnova

et al. 2005

International Journal of Photoenergy

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Mesoporous silica powders and films modified with organic sensitizer benzophenone were used as photocatalysts in the reaction of silver ion reduction by isopropyl alcohol under UV-irradiation withλ=253.7 nm and 365 nm in presence of colloidal silica as stabilizer. Morphological changes of silver colloids during irradiation were studied using transmission electron microscopy, and correlated to the absorption spectra.

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Section: Resultsmentioning

confidence: 99%

Structure and spectra of photochemically obtained nanosized silver particles in presence of modified porous silica

Krylova

Eremenko

Smirnova

et al. 2005

International Journal of Photoenergy

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“…However, to the best of our knowledge, there are few reports about the systematic study of solvent effects on the radical in the excited state. Yankov et al reported the solvent effect on the fluorescence of BPH • . However, the solvent effect on the relaxation processes of BPH • (D 1 ) was not revealed due to the poor time resolution of the instruments.…”

Section: Introductionmentioning

confidence: 99%

Solvent Effect on the Deactivation Processes of Benzophenone Ketyl Radicals in the Excited State

et al. 2006

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The solvent effects on ketyl radicals of benzophenone derivatives (BPD) in the excited state (BPDH*(D1)) were investigated. Absorption and fluorescence spectra of BPDH*(D1) in various solvents were measured using nanosecond-picosecond two-color two-laser flash photolysis. The fluorescence peaks from BPDH*(D1) showed a shift due to the dipole-dipole interaction with the solvent molecules. The dipole moments (mu(e)) of BPDH*(D1) were estimated to be 7-10 D, indicating that BPDH*(D1) are highly polarized. It was revealed that the fluorescence lifetime (tau(f)) depends on mu(e) in acetonitrile because the stabilization by solvent molecules affects the tau(f) value in polar solvents, predominantly. On the contrary, the conformation of BPDH*(D1) plays an important role in cyclohexane because the efficiency of the unimolecular reaction from BPDH*(D1) depends on the conformation. The substituent effect on the electron transfer from BPDH*(D1) to their parent molecules was also discussed.

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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%

“…A potentially sensitive means of detecting aromatic radical intermediates produced in these photoreactions is to photoexcite the radical to its excited-doublet state and monitor fluorescence from the excited radical. Fluorescence from the diphenylketyl radical or benzophenone ketyl radical has been studied in order to investigate the photophysics and photochemistry of the excited-doublet state. ,,− 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, 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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Fluorescence of the benzophenone ketyl radical: solvent effects

Cited by 9 publications

References 14 publications

Structure and spectra of photochemically obtained nanosized silver particles in presence of modified porous silica

Structure and spectra of photochemically obtained nanosized silver particles in presence of modified porous silica

Solvent Effect on the Deactivation Processes of Benzophenone Ketyl Radicals in the Excited State

Time-Resolved Fluorescence Monitoring of Aromatic Radicals in Photoinitiated Processes

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