- The development of 1,3-diphenylisobenzofuran as a highly selective probe for the detection and quantitative determination of hydrogen peroxide
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1,3-Diphenylisobenzofuran (DPBF) has been developed as a selective probe for the detection and quantitative determination of hydrogen peroxide in samples containing different reactive nitrogen and oxygen species (RNOS). DPBF is a fluorescent probe which, for almost 20 years, was believed to react in a highly specific manner toward some reactive oxygen species (ROS) such as singlet oxygen and hydroxy, alkyloxy or alkylperoxy radicals. Under the action of these individuals DPBF has been rapidly transformed to 1,2-dibenzoylbenzene (DBB). In order to check if DPBF can act as a unique indicator of the total amount of different RNOS, as well as oxidative stress caused by an overproduction of these individuals, a series of experiments was carried out, in which DPBF reacted with peroxynitrite anion, superoxide anion, hydrogen peroxide, hypochlorite anion, and anions commonly present under biological conditions, namely nitrite and nitrate. In all cases, except for hydrogen peroxide, the product of the reaction is DBB. Only under the action of H2O2 9-hydroxyanthracen-10(9H)-one (oxanthrone) is formed. This product has been identified with the use of fluorescence spectroscopy, NMR spectroscopy, high performance liquid chromatography coupled with mass spectrometry, infrared spectroscopy, elemental analysis, and cyclic voltammetry (CV). A linear relationship was found between a decrease in the fluorescence intensity of DPBF and the concentration of hydrogen peroxide in the range of concentrations of 0.196–3.941 mM. DPBF responds to hydrogen peroxide in a very specific way with the limits of detection and quantitation of 88 and 122.8 μM, respectively. The kinetics of the reaction between DBBF and H2O2 was also studied.
- ?amoj?, Krzysztof,Zdrowowicz, Magdalena,Rudnicki-Velasquez, Pawe? B?a?ej,Krzymiński, Karol,Zaborowski, Bart?omiej,Niedzia?kowski, Pawe?,Jacewicz, Dagmara,Chmurzyński, Lech
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- Visible light singlet oxygen production with tetra(4-carboxyphenyl) porphyrin/SiO2
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The production of singlet oxygen with tetra(4-carboxyphenyl)porphyrin adsorbed on SiO2 irradiated with visible light (λ > 500 nm) was evidenced by EPR spectra of TEMPO formed by oxidation of 2,2,6,6-tetramethyl-4-piperidone(TEMP) with 1O2. The formation of singlet oxygen was also evidenced by the formation of anthraquinone and oxanthrone as oxidation products of anthracene with 1O 2. The absence of the EPR DMPO-O2- signal evidenced that superoxide anion was not present. No other oxygen radicals were detected. TCPP and TCPP/SiO2 were characterized with UV-vis, UV-vis diffuse reflectance and FT-IR spectroscopy.
- Diaz-Uribe, Carlos E.,Daza, Martha C.,Páez-Mozo, Edgar A.,Martínez O., Fernando,Guedes, Carmen L.B.,Di Mauro, Eduardo
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- Photoreduction of nitro arenes by formic acid in acetonitrile at room temperature
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The formic acid-mediated photoreduction of aromatic nitro compounds in room temperature acetonitrile solutions was investigated. This mild photoreduction can be accomplished in high yield, with wide functional group tolerance and short reaction times (30 min to 1 h), and allows a very clean method for the conversion of nitro arenes to amines. Also, the photoreduction, as a convenient, versatile and general method, applies efficiently to polycyclic and heterocyclic nitro arenes.
- Cors, Ariel,Bonesi, Sergio M.,Erra-Balsells, Rosa
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p. 1555 - 1558
(2008/09/19)
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- Meso-disubstituted anthracenes with fluorine-containing groups: Synthesis, light-emitting characteristics, and photostability
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(Chemical Equation Presented) Synthesis, photophysical properties, and photostability of 9,10-disubstituted anthracenes with fluorine-containing groups (FCG) are described. The values of Φf and λem greatly go up by the meso-substitution with FCG, and a nice corelationship between Φf and Aπ (magnitude of π conjugation length in the excited single state) is observed. The C6F5 group at the meso positions exhibits an excellent ability in the photostability as well as in the emission efficiency.
- Matsubara, Yoshio,Kimura, Atsushi,Yamaguchi, Yoshihiro,Yoshida, Zen-ichi
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supporting information; experimental part
p. 5541 - 5544
(2009/05/30)
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- Photocatalytic oxygenation of anthracenes and olefins with dioxygen via selective radical coupling using 9-mesityl-10-methylacridinium ion as an effective electron-transfer photocatalyst
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Visible light irradiation of the absorption band of 9-mesityl-10- methylacridinium ion (Acr+-Mes) in an O2-saturated acetonitrile (MeCN) solution containing 9,10-dimethylanthracene results in formation of oxygenation product, i.e., dimethylepidioxyanthracene (Me 2An-O2). Anthracene and 9-methylanthracene also undergo photocatalytic oxygenation with Acr+-Mes to afford the corresponding epidioxyanthracenes under the photoirradiation. In the case of anthracene, the further photoirradiation results in formation of anthraquinone as the final six-electron oxidation product, via 10-hydroxyanthrone, accompanied by generation of H2O2. When anthracene is replaced by olefins (tetraphenylethylene and tetramethylethylene), the photocatalytic oxygenation of olefins affords the corresponding dioxetane, in which the O-O bond is cleaved to yield the corresponding ketones. The photocatalytic oxygenation of anthracenes and olefins is initiated by photoexcitation of Acr+-Mes, which results in formation of the electron-transfer state: Acr?- Mes?+, followed by electron transfer from anthracenes and olefins to the Mes?+ moiety together with electron transfer from the Acr? moiety to O2. The resulting anthracene and olefin radical cations undergo the radical coupling reactions with O 2?- to produce the epidioxyanthracene (An-O 2) and dioxetane, respectively.
- Kotani, Hiroaki,Ohkubo, Kei,Fukuzumi, Shunichi
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p. 15999 - 16006
(2007/10/03)
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- Oxidation of polycyclic aromatic hydrocarbons catalyzed by iron tetrasulfophthalocyanine FePcS: Inverse isotope effects and oxygen labeling studies
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Iron(III) tetrasulfophthalocyanine (FePcS) was shown to catalyze the oxidation of polycyclic aromatic hydrocarbons by H2O2. Benzo[a]pyrene and anthracene were converted to the corresponding quinones while biphenyl-2,2′-dicarboxylic acid was the main product of phenanthrene oxidation. The mechanism of the anthracene oxidation by H2O2 in the presence of FePcS or by KHSO5 with iron(III) mesotetrakis(3,5-disulfonatomesityl)porphyrin (FeTMPS) (see Figure 1 for catalyst structures) has been investigated in details by using kinetic isotope effects (KIEs) and 18O labeling studies. KIEs measured on the substrate consumption in the competitive oxidation of [H10] anthracene and [D10]anthracene by FePcS/H2O2 and FeTMPS/KHSO5 were essentially the same, 0.75 ± 0.02 and 0.76 ± 0.06, respectively. These inverse KIEs on the first oxidation step can be explained by the sp2-to-sp3 hybridization change during the addition of an electrophilic oxoiron complex to the sp2 carbon center of anthracene to form a σ adduct (this inverse KIE being enhanced by stronger slacking interactions between the perdeuterated substrate with the macrocyclic catalyst). Although the first oxidation step seems to be the same, different distribution of the oxidation products of anthracene and very different 18O incorporation into anthrone and anthraquinone in catalytic oxidations performed in the presence of H218O suggested that different active species should be responsible for anthracene oxidation in both catalytic systems. All the results obtained are compatible with an involvement of TMPSFeV=O (or TMPS+FeIV=O), having two redox equivalents above the iron(III) state of the metalloporphyrin precursor, while PcSFeIV=O (one redox equivalent above FeIII state of FePcS) was proposed to be the active species in the metallophthalocyanine-based system.
- Sorokin, Alexander,Meunier, Bernard
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p. 1269 - 1281
(2007/10/03)
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- Photochemistry of anthracene in water
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Photolysis of anthracene (350 nm) in aerated water yields endoperoxide and 9,10-anthraquinone as the major primary photoproducts. Photolysis of anthracene in oxygen-deficient aqueous solutions yields the three isomers of 10,10'-dihydroxy-9,9',10,10'-tetrahydro-9,9'-bianthryl as the primary photoproduct. Involvement of a cation radical mechanism is suggested.
- Sigman,Zingg,Pagni,Burns
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p. 5737 - 5740
(2007/10/02)
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- ELECTROCHEMISTRY AT ANTHRACENE CRYSTAL/AQUEOUS NO2-, NO3- SOLUTION INTERFACE
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Holes (radical cations) were injected into one face of an anthracene crystal slab and discharged at the other face, which was in contact with a neutral aqueous solution containing 1 M NO3- or NO2-.Hole current densities (J) of up to 700 μAcm-2 generated a variety of surface oxidation products including anthraquinone, 9-nitroanthracene (9NA), oxanthrone, anthrone, bianthronyl (BA), and 9,10-dinitroanthracene with both NO3- and NO2- solutions.The amount of BA and 9NA increased as J2.With increasing NO3- concentration, the amount of 9NA produced increased, while that of BA decreased.It was concluded that 9NA is made by cooperation of two holes on adjoining molecules at defect sites.
- Leong, Baldwin,Pope, Martin,Steigman, Joseph
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p. 2506 - 2511
(2007/10/02)
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- Transformations photochimiques d'endoperoxydes derives d'hydrocarbures aromatiques polycycliques II. Cas de l'endoperoxyde d'anthracene: di- et tetraepoxydes derives
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Syn 4a,10:9,9a-diepoxy-4a,9,9a,10-tetrahydroanthracene 10, an intermediate in the thermal transformations of 9,10-epidioxyanthracene 5a, can be prepared by photolysis of 5a in benzene at long wavelengths (λ >/= 435 nm) and at low temperature.Its chemical behaviour has been studied.In particular, diepoxide 10 appears to be very sensitive to acids and is isomerized by ZnCl2 into a bicyclic acetal: 6,11-epoxy-6,11-dihydrodibenzooxepine 20.Acetal 20 is itself isomerized by CF3CO2H into the unstable 1-(2-hydroxyphenyl)-isobenzofuran 32, which can be trapped by N-methylmaleimide as endo (33) and exo (35) adducts.Photo-oxygenation of die 10 leads to the 1,4-epidioxy-4a,10:9,9a-diepoxy-1,4,4a,9,9a,10-hexahydroanthracenes, syn 25 and anti 26, which by thermal or photochemical isomerization give the 1,2:3,4:4a,10:9,9a-tetraepoxy-1,2,3,4,4a,9,9a,10-octahydroanthracenes syn 27 and anti 28.The stereochemistry of these new compounds has been deduced from 1H NMR spectra.
- Defoin, Albert,Baranne-Lafont, Joele,Rigaudy, Jean
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p. 145 - 155
(2007/10/02)
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