CIDEP studies of the formation of benzyl-type radicals in the photoreduction of flavones

Sakaguchi, Yoshio; Hayashi, H.; Murai, Hisao; I’Haya, Yasumasa J.

doi:10.1021/j100282a004

Cited by 34 publications

(14 citation statements)

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“…However their intensities are expected to differ remarkably from the corresponding line intensities of EPR spectra of pairs of radicals under thermal equilibrium [2]. This expectation follows from simple arguments.…”

Section: Intensities Of Aps Linesmentioning

confidence: 93%

“…Asa consequenee, ah EPR line of one of the separate radicals is in emission while another radical has an EPR line in absorption (CIDEP effect, see, e.g., [1]). Second, EPR spectra of radical pairs in cage demonstrate so-called antiphase structure (APS) lines [2][3][4]. Both these features originate from spin dynamics of unpaired electron spins of radical pairs bom in a state with the non-zero zero-quantum coherence, i.e., in the definite multiplet state -singlet or triplet.…”

Section: Introductionmentioning

confidence: 99%

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Comment on a shape of EPR spectra of spin-correlated radical pairs and separate radicals escaped geminate recombination

Salikhov

1997

Appl. Magn. Reson.

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For model spin-correlated radical pairs (RPs) the EPR spectra are simulated and their shape is analyzed in detail. It is demonstrated that the widths and intensities of the EPR spectra are determined essentially by the rate of the singlet-triplet dephasing and the scale of the spin-spin interactions. It is also shown that chemical exchange of the RPs between states with different values of the exchange and the dipole-dipole interactions can produce the apparent antiphase structure lines in the EPR spectra.

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Section: Intensities Of Aps Linesmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Comment on a shape of EPR spectra of spin-correlated radical pairs and separate radicals escaped geminate recombination

Salikhov

1997

Appl. Magn. Reson.

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“…Adduct formation occurs especially when the reductant molecules have hydrogen atoms directly bonded to germanium, boron or tin, making them comparatively more electronegative. Benzyl radicals are formed when flavones ate photolyzed in the presence of this type of reductant [6]. With maleic anhydride, the hydrogen adduct formation is observed even in the absence of these particular compounds [7,8].…”

Section: Introductionmentioning

confidence: 98%

Time-resolved EPR study of the photoreduction of phthalic anhydride and chlorinated phthalic anhydrides in 2-propanol

et al. 2003

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The photoreduction of phthalic anhydride (PA), 3,6-dichlorophthalic anhydride (3,6-DCPA), 4,5-dichlorophthalic anhydride (4,5-DCPA) and tetrachlorophthalic anhydride (TCPA) in 2-propanol has been studied with time-resolved electron paramagnetic resonance. The chemically induced dynamic electron polarization spectra show that the reaction takes place through the excited triplet states. From PA, cyclohexadienyl-type hydrogen adduct and ketyl radicals were observed, whereas 3,6-DCPA produced the 3,6-DCPA anion and hydrogen adduct radicals. With 4,5-DCPA only the anion radical appeared, whilst the TCPA system showed no apparent anion and adduct radical formation. These data show that the hydrogen adduct formation occurs at the 4 position in the benzene ring, but that 4,5-DCPA and TCPA do not undergo this reaction. The anion radicals of PAs are formed in subsequent deprotonation reactions of the ketyl radicals. We propose that the hydrogen adduct radical formation in PA and 3,6-DCPA takes place through direct hydrogen abstraction by the excited triplet molecules, in competition with similar abstraction by the carbonyl group to form the ketyls.

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“…Xanthone (Xn, Figure 1) is one of the aromatic carbonyl compounds, and there have been a lot of reports on its photoinduced reactions in homogeneous and inhomogeneous systems. [24][25][26][27][28] The rate constants (k q ) of the quenching reaction of the excited triplet state of Xn ( 3 Xn*) with phenols in organic solvents were reported to be on the order of 10 8 to 10 9 M -1 s -1 , which is slightly smaller than the diffusion controlled limit. In micelle systems, 3 Xn* is expected to react with water-soluble AsH -very fast at the water-oil interface region of the micelle because Xn exists in the hydrophobic region of the micelle, similarly to Toc • .…”

Section: Introductionmentioning

confidence: 99%

Time-Resolved Electron Paramagnetic Resonance Investigation of Photoinitiated Antioxidant Reaction of Vitamin C (Ascorbic Acid) with Xanthone in Aqueous Sodium Lauryl Sulfate, Hexadecyltrimethylammonium Chloride, and Triton X-100 Micelle Solutions

et al. 2003

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The photoinitiated reaction between vitamin C and xanthone in sodium lauryl sulfate (SDS), hexadecyltrimethylammonium chloride (CTAC), and Triton X-100 micelle solutions at various pH was investigated by time-resolved electron paramagnetic resonance (TR-EPR). The TR-EPR spectra were explained by superimpositions of the xanthone ketyl and the vitamin C radicals, showing that a fast hydrogen abstraction reaction of the excited xanthone from vitamin C progresses around the water−oil interface region of the micelles. The EPR signal intensity of the vitamin C radical showed the notable pH dependence, which seems to be attributable to the acid−base dissociation equilibrium of vitamin C. The results suggested that the present reaction is controlled by the transportation of the excited xanthone and vitamin C to the reaction-progressing region, which is the surface or inside of the micelle, and by the difference of the reactivity between the dissociation forms of vitamin C.

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CIDEP studies of the formation of benzyl-type radicals in the photoreduction of flavones

Cited by 34 publications

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Comment on a shape of EPR spectra of spin-correlated radical pairs and separate radicals escaped geminate recombination

Comment on a shape of EPR spectra of spin-correlated radical pairs and separate radicals escaped geminate recombination

Time-resolved EPR study of the photoreduction of phthalic anhydride and chlorinated phthalic anhydrides in 2-propanol

Time-Resolved Electron Paramagnetic Resonance Investigation of Photoinitiated Antioxidant Reaction of Vitamin C (Ascorbic Acid) with Xanthone in Aqueous Sodium Lauryl Sulfate, Hexadecyltrimethylammonium Chloride, and Triton X-100 Micelle Solutions

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