Involvement of the azide radical in the quenching of singlet oxygen by azide anion in water

Harbour, John R.; Issler, Sandra L.

doi:10.1021/ja00367a066

Cited by 140 publications

(69 citation statements)

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“…The main mechanism which takes place in our reaction conditions may be the generation of singlet oxygens and their reaction with the substrates. Further evidence for a 1 O 2 mechanism was obtained by performing the photooxygenation in the presence of N 3 -, which is known as a singlet oxygen scavenger [95,96,101]. Entry 4 in Table 2 shows that the yield of free base porphyrin was considerably reduced under these conditions.…”

Section: Resultssupporting

confidence: 45%

Oxidation of benzoins to benzils in the presence of porphyrin sensitizers by air and sunlight or visible light

et al. 2013

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In this work, two new aerobic routes are introduced for the oxidation of a variety of benzoins to benzils by using molecular oxygen in the presence of porphyrins as sensitizers, using white light or sunlight in acetonitrile under mild conditions. The methods have a wide range of applications, do not involve cumbersome work-up, exhibit chemoselectivity and proceed under mild reaction conditions. The resulting products are obtained in good yields in a reasonable time.

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Section: Resultssupporting

confidence: 45%

Oxidation of benzoins to benzils in the presence of porphyrin sensitizers by air and sunlight or visible light

et al. 2013

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Section: Confirmation Of Singlet Oxygen Presencesupporting

confidence: 43%

“…Sodium azide is known as a strong singlet oxygen quencher (10 8 dm 3 mol -1 s -1 in H 2 O). 33,37,38 In all the equipments similar profiles of DPBF oxidation and suppression by azide were observed, Figure 3 shows the results observed with the LED600 equipment.It is possible to observe in Figure 3B, that in the presence of NaN 3 , a reduction in the oxidation speed of DPBF occurs. The absorption peak in the DPBF region is found in the 429 nm region and shows the Figure that the mechanism of oxidation by participation of singlet oxygen is predominant.…”

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confidence: 43%

A comparative study of irradiation systems for photoinactivation of microorganisms

Paula¹,

Santos²,

Menezes³

et al. 2010

J. Braz. Chem. Soc.

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Estudou-se a construção de sistemas de LED aplicados a processos de fotosensitização. Visando à obtenção de dispositivos mais eficientes avaliou-se a aplicação de LED de alta potência (HPLED), que apresenta maior fluxo fotônico, tendendo a excitar uma maior fração de moléculas. Foram descritos detalhes de construção de 3 diferentes sistemas de irradiação completamente distintos (lâmpada halógena filtrada, LED convencional, HPLED), utilizando azul de metileno como fotosensitizador. A comparação entre a eficiência de cada equipamento foi realizada através da cinética de fotooxidação de 1,3-Diphenylisobenzofuran e inativação de Staphylococcus aureus. A emissão de luz de cada equipamento, sobreposta à absorção do fotosensitizador, também se mostrou um importante parâmetro na estimativa da eficiência dos equipamentos. Foi observada uma inibição bacteriana superior a 99% para concentrações de 5 × 10 -6 mol dm -3 de fotosensitizador, no sistema que emprega HPLED. Os equipamentos baseados em LED, apresentaram resultados satisfatórios além de baixo custo e simples montagem.The construction of LED systems applied to photosensitization processes was studied. Aiming to obtain more efficient devices it was evaluated the use of high intensity LED (HPLED), that present greater photonic flux, tending to excite a greater fraction of molecules. Construction details for 3 different irradiation systems were described (filtered halogen bulbs, conventional LED, HPLED), using methylene blue as a photosensitizer. A comparison between the efficiency of the equipments was carried out through the kinetics of photooxidation of 1,3-Diphenylisobenzofuran and Staphylococcus aureus photoinactivation. The overlap between the light emited from each equipment and the photosensitizer absorption, was also an important parameter in estimating the efficiency of the equipment. Bacterial inhibition higher than 99% for concentrations of 5 × 10 -6 mol dm -3 of the photosensitizer was observed, in the system that uses HPLED. The equipments based on LED showed satisfactory results, besides their low cost and simple to assembling. Keywords: high power LED, Staphylococcus aureus, methylene blue, irradiation systems IntroductionPhotodynamic Inactivation (PDI) 1 or Photodynamic Antimicrobial Chemotherapy (PACT) 2 is the name of a process, derived from Photodynamic Therapy, that causes the death of microorganisms under the action of visible light and a specific drug, also called photosensitizer. 3 The electronic excitation of the photosensitizer in the presence of oxygen implies in the generation of a large number of reactive oxygen species (ROS), as for example, singlet oxygen, 4,5 in a process known as photosensitization.Since 1976, the oxidative action of singlet oxygen and other ROS on tumor cells has been reported in the medical and scientific communities. 5,6 Around the world, several research results have been published on the use of photosensitization to fight diseases caused by fungi, viruses, bacteria and yeasts. 3,5,[7][8][9][10][11] Among the photos...

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“…So far, the mechanism of 1 O2 emission quenching by Ν3 ions has not been well recognized. While Harbour' and Issler claim that the process of 1 O2 2 quenching proceeds through formation of charge-transfer complex [7], Haag and Mill prove that the dominant reaction in this process is typical physical quenching [8].In our studies incorporation of azide ions, Ν3 , into the Eu(ΙΙ)/Eu(IΙI)-H 2 O 2 system, brings about a strong increase in chemiluminescence emission characteristic of Εu(III) ions. On the basis of both chemiluminescence and fluorescence studies, where particular emphasis was paid to the measurements of a lifetime of 5 D0 Εu(III) ions, a mechanism of chemiluminescence process was proposed.…”

mentioning

confidence: 40%

Influence of N₃^-Ions on Chemiluminescence of the Eu(II)/Eu(III)-H₂O₂System

et al. 1996

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The basic system of chemiluminescence investigations of relevant biological and inorganic compounds consists of Εu(II)/Εu(III)-Η2O2 . In these studies the increase in Eu(III) ion emission intensity usually results from an effective complexation reaction. In the present study, the Ν3 ions are used as a ligand. The increase in the chemiluminescence intensity of the Εu(III) ion, the pH influence (in the range of 4.5-7.5) on the chemiluminescence intensity of the Eu(lII) ion, as well as the quenching of the 5D0 excited state of the Εu(IIl) ion are observed due to Ν3 complexation. Taking into account the well-known Fenton system [Fe(II)/Fe(III)-Η2O2], containing additionally the Ν3, Eu(lII) or Sm(llI) ions, we found that the Εu(III) or Sm(III) ions were excited as a result of energy transfer process. A mechanism of the studied reactions is proposed.PACS numbers: 78.60.Ps, 78.55.-m 1. Ιntroduction A chemiluminescence (CL) method is used to study both biological and inorganic compounds in systems containing lanthanide ions, mainly europium [1][2][3]. The basic reaction of the method is oxidation of Eu(II) to Eu(III) ions, occurring in complexes with ligand, through hydrogen peroxide and excitation of these ions, which then come down to the ground state emitting characteristic radiation [3]. Products of simultaneous reactions of H 2 O 2 decomposition and radicals recombination are excited dimoles of a singlet state 1O2 [4, 5], whose influence on the level of CL may by determined using quenchers [6]. In literature the often reported quencher of an excited state 1 O2 are azide ions Ν . So far, the mechanism of 1 O2 emission quenching by Ν3 ions has not been well recognized. While Harbour' and Issler claim that the process of 1 O2 2 quenching proceeds through formation of charge-transfer complex [7], Haag and Mill prove that the dominant reaction in this process is typical physical quenching [8].In our studies incorporation of azide ions, Ν3 , into the Eu(ΙΙ)/Eu(IΙI)-H 2 O 2 system, brings about a strong increase in chemiluminescence emission characteristic of Εu(III) ions. On the basis of both chemiluminescence and fluorescence studies, where particular emphasis was paid to the measurements of a lifetime of 5 D0 Εu(III) ions, a mechanism of chemiluminescence process was proposed.(101)

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Involvement of the azide radical in the quenching of singlet oxygen by azide anion in water

Cited by 140 publications

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Oxidation of benzoins to benzils in the presence of porphyrin sensitizers by air and sunlight or visible light

Oxidation of benzoins to benzils in the presence of porphyrin sensitizers by air and sunlight or visible light

A comparative study of irradiation systems for photoinactivation of microorganisms

Influence of N₃^-Ions on Chemiluminescence of the Eu(II)/Eu(III)-H₂O₂System

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Involvement of the azide radical in the quenching of singlet oxygen by azide anion in water

Cited by 140 publications

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Oxidation of benzoins to benzils in the presence of porphyrin sensitizers by air and sunlight or visible light

Oxidation of benzoins to benzils in the presence of porphyrin sensitizers by air and sunlight or visible light

A comparative study of irradiation systems for photoinactivation of microorganisms

Influence of N3-Ions on Chemiluminescence of the Eu(II)/Eu(III)-H2O2System

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Influence of N₃^-Ions on Chemiluminescence of the Eu(II)/Eu(III)-H₂O₂System