Paramagnetic Resonance Study of Liquids during Photolysis: Hydrogen Peroxide and Alcohols

Livingston, Ralph; Zeldes, Henry

doi:10.1063/1.1726811

Cited by 262 publications

(76 citation statements)

References 24 publications

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“…The g-value and lack of hyperfine structure of the resonance due to the solvent species are consistent with the known ESR properties of ethoxy radicals (7), which are quite different from those of radicals resulting from ahydrogen abstraction (8). The kinetic results (first-order decay and dependence of decay rate on porphyrin) indicate that complexes are being generated, a binary complex of semiquinone and ethoxy radical in the case of quinone alone, and a ternary complex of porphyrin, semiquinone, and ethoxy radical in the porphyrin-sensitized process.…”

Section: Discussionsupporting

confidence: 70%

In Vitro Photoreactions of Chlorophyll and Photosynthetic Energy Conversion: Chlorophyll-Quinone-Ethanol at Low Temperature as an Analog of Photosystems I and II

Harbour

Tollin

1972

Proc. Natl. Acad. Sci. U.S.A.

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Illumination at low temperatures of ethanol solutions of p-benzoquinone, alone or in the presence of chlorophyll or pheophytin, leads to the reversible formation of radical complexes. Based on g-value determinations and deuterium-substitution effects, the radicals are identified as a semiquinone and an ethoxy radical. In the porphyrin-sensitized system, ternary complexes are produced. Chlorophyll also forms a cation radical upon illumination, whereas pheophytin does not. The generation of this cation radical is independent of the presence of quinone, and proceeds via the chlorophyll singlet state, as opposed to quinone and ethoxy radical production, which involve triplet states. The significance of these reactions to photosynthetic energy conversion is discussed.Our previous studies of chlorophyll-sensitized quinone radical production in solution (1-3) have provided indirect evidence, mainly kinetic in nature, for the following primary photoprocess:(solvent-Chl-quinone) + hp --(solvent-ChlT-quinone) (solvent-ChlI-quinone) solvent0X+ Chl + quinonered This mechanism proposes that absorption of a photon within a ternary complex results, via the chlorophyll triplet state, in the formation of an oxidized solvent radical and a reduced quinone radical (semiquinone). The purpose of this communication is to report on attempts to obtain further support for this mechanism by the use of low temperatures to stabilize the solvent radical, and deuterated solvent and quinone to permit individual identification of ESR signals due to radicals derived from these components. As will be shown, evidence has been obtained that demonstrates that illumination of these solutions does indeed lead to the formation of the above-mentioned radicals, in addition to the chlorophyll cation radical, which is produced in a separate parallel reaction. A more complete account of these experiments, which will be published separately (manuscript in preparation), includes a detailed interpretation of the ESR spectra in terms of the nature of the intermediates that are formed. METHODSAll of the experimental techniques involved in sample preparation, chlorophyll purification, and ESR observation have been described (2, 4). g-Value determinations were made with diphenylpicryihydrazyl as a standard. Fully-deuterated ethanol was obtained from Merck, Inc. The fully-deuterated benzoquinone was prepared by the method of Charney and Becker (5). RESULTSUpon irradiation of degassed solutions of either benzoquinone (with blue light: 330-500 nm, or white light) or pheophytin plus benzoquinone (with red light: Corning CS 2-73 filter) in ethanol in an ESR spectrometer at 1300K, the spectrum shown in Fig. 1 is reversibly produced. Note the poorly-resolved, but still evident, hyperfine structure that is present, particularly on the low-field side of the spectrum. Under similar experimental conditions, replacement of ethanol by its fully-deuterated analog resulted in a considerable improvement in spectral resolution (Fig. 1). A possible cause of such enhanced re...

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Section: Discussionsupporting

confidence: 70%

In Vitro Photoreactions of Chlorophyll and Photosynthetic Energy Conversion: Chlorophyll-Quinone-Ethanol at Low Temperature as an Analog of Photosystems I and II

Harbour

Tollin

1972

Proc. Natl. Acad. Sci. U.S.A.

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“…The g values of the radical species formed by the reaction of Scheme I-2 seems to be about 2.01, since there was a localized radical on the O atom. 36 On the other hand, the g values for a free electron shifted to 2.0023 as a result of the delocalized radical on the OCO bond, in which the radical species was formed by the reaction of Scheme I-1. Therefore, Scheme I-1 seems to be the structure that actually occurred in the oxidation reaction process on the charged positive electrode.…”

Section: Resultsmentioning

confidence: 99%

“…22,[33][34][35][36] A spin-spin dipole interaction depends on the spin concentration. In this case, the concentration of the radical species was about 100 ppm in the electrolyte solution, which is sufficient for the broadening effect needed to achieve spin-spin interaction.…”

Section: Resultsmentioning

confidence: 99%

Electron-Spin-Resonance Study of the Reaction of Electrolytic Solutions on the Positive Electrode for Lithium-Ion Secondary Batteries

Matsuta

Katô

Ota

et al. 2001

J. Electrochem. Soc.

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The lithium-ion secondary battery is mainly used as the power source for a variety of portable electronic equipment because of its high energy density. However, many efforts have been made to improve its performance even after it was marketed in 1990. 1 One technical issue is that the capacity decreases during cycling or storage.Solvent decomposition on the electrode is considered a major reason for the capacity decrease. [2][3][4][5] Therefore, many studies have been carried out on the decomposition mechanisms of electrolytic solutions on the negative or positive electrode.In the negative electrode, the reduction of the electrolyte irreversibly forms a surface film on it. 6,7 This film is called the solidelectrolyte interphase (SEI). [7][8][9] The SEI has been studied by analytical techniques such as X-ray photoelectron spectroscopy (XPS) [10][11][12] and infrared spectroscopy. [13][14][15][16][17][18] In past studies, reaction gas products like alkane, alkene, H 2 , CO 2 , and CO are produced and have been observed by gas chromatography. [19][20][21] Many decomposition mechanisms of the electrolytic solutions on the negative electrode surface were suggested from observations of the final decomposition products. Radical species of an intermediate state in this reaction mechanism were observed by electron spin resonance spectroscopy (ESR). 22 Research continued to elucidate the reaction between the electrolytic solution and the negative electrode.In parallel with the above work, CO 2 and ROCOOLi-type compounds have been observed as reaction products of the electrolytic solutions on the positive electrode by infrared spectroscopy, 23-27 mass spectroscopy, 26,27 and ESR. 28 Studying the reaction between the positive electrode and the electrolyte solution is important because an oxidation of the electrolytic solution on the positive electrode is regarded as a major cause of self-discharge. 3,[29][30][31] This oxidation can be expressed by the following equation 29,30 Electrolytic solution ϩ Li x MO 2 ϩ yLi ϩ r oxidized species of electrolytic solution ϩ Li xϩy MO 2 [1] In this reaction, passing through cation radical species, the electrolytic solution is decomposed into gas species, soluble species in the electrolytic solution, and solid electrolyte interphase (SEI) components on the electrode.In this work, we use ESR to observe the reactive intermediate radical species in the reaction between the positive electrode and the electrolytic solution. Furthermore, we discuss the intermediate radical structure and these radical quantities. ExperimentalNonaqueous solvents [ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC)], lithium hexafluorophosphate (LiPF 6 ), and LiCoO 2 , of which the grade were used by the marketing battery, were used. The LiCoO 2 was oxidized by charging to the potential of 4.3 V vs. Li/Li ϩ .Samples for the ESR measurement were prepared as follows. A charged positive electrode of 2 ϫ 25 mm with 19 mg of an active mate...

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“…More relevantly, it is known that the unpaired spin in groups such as -CH-OH and -NH-0. couples unsymmetrically to the aromatic protons in radicals such as c,H,-CH-OH (34,35) and C6H,-NH-0.…”

Section: The Structure Of Radicals Formed Frommentioning

confidence: 99%

Electron paramagnetic resonance spectroscopic study of radicals derived from glycine, dl-α-alanine, and β-alanine in aqueous solution

Smith¹,

Fox²,

Mcginty³

et al. 1970

Can. J. Chem.

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The substrates glycine, dl-u-alanine, and B-alanine have been examined in turn within an aqueous continuous-flow system using the titanous chloride -hydrogen peroxide radical-generating method.The temperature was 25 i 2 "C and the p H of the reaction mixture was varied within the range of values ca. 2 to ca. 5 by addition of sulfuric acid. The electron paramagnetic resonance spectra of the following transient radicals were observed: from glycine, .CH(NHZ)COOH; from dl-a-alanine, CH3C(NNZ)COOH and .CH2CH(NH3+)COOH; and from P-alanine, CH2(NH3+)CHCOOH.

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Paramagnetic Resonance Study of Liquids during Photolysis: Hydrogen Peroxide and Alcohols

Cited by 262 publications

References 24 publications

In Vitro Photoreactions of Chlorophyll and Photosynthetic Energy Conversion: Chlorophyll-Quinone-Ethanol at Low Temperature as an Analog of Photosystems I and II

In Vitro Photoreactions of Chlorophyll and Photosynthetic Energy Conversion: Chlorophyll-Quinone-Ethanol at Low Temperature as an Analog of Photosystems I and II

Electron-Spin-Resonance Study of the Reaction of Electrolytic Solutions on the Positive Electrode for Lithium-Ion Secondary Batteries

Electron paramagnetic resonance spectroscopic study of radicals derived from glycine, dl-α-alanine, and β-alanine in aqueous solution

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