Superoxide Radical Anion‐Mediated Aerobic Oxidative Synthesis of 2‐Substituted Quinazolines under Visible Light

2017 ◽  
Vol 6 (4) ◽  
pp. 449-452 ◽  
Author(s):  
Xiu‐Long Yang ◽  
Qing‐Yuan Meng ◽  
Xue‐Wang Gao ◽  
Tao Lei ◽  
Cheng‐Juan Wu ◽  
...  
Keyword(s):  
Visible Light ◽  
Radical Anion ◽  
Superoxide Radical ◽  
Superoxide Radical Anion

Visible light superoxide radical anion generation by tetra(4-carboxyphenyl)porphyrin/TiO2: EPR characterization

2010 ◽  
Vol 215 (2-3) ◽  
pp. 172-178 ◽  
Author(s):  
Carlos E. Diaz-Uribe ◽  
Martha C. Daza ◽  
Fernando Martínez ◽  
Edgar A. Páez-Mozo ◽  
Carmen L.B. Guedes ◽  
...  
Keyword(s):  
Visible Light ◽  
Radical Anion ◽  
Superoxide Radical ◽  
Superoxide Radical Anion

Scavenging of photogenerated singlet molecular oxygen and superoxide radical anion by sulpha drugs - Kinetics and mechanism

2004 ◽  
Vol 82 (12) ◽  
pp. 1752-1759 ◽  
Author(s):  
Marta Díaz ◽  
Marta Luiz ◽  
Sonia Bertolotti ◽  
Sandra Miskoski ◽  
Norman A García
Keyword(s):  
Visible Light ◽  
Ground State ◽  
Radical Anion ◽  
Superoxide Radical ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Singlet Molecular Oxygen ◽  
Superoxide Radical Anion ◽  
Sulpha Drugs

The ability of the sulfanilic antibiotics (SDs), dapsone (DAP), sulfisoxazole (SFX), sulfadiazine (SFD), and sulfanilic acid (SFNA) to act as scavengers of the visible-light-photogenerated species superoxide radical anion (O2·–) and singlet molecular oxygen (O2(1Δg)) was studied employing the natural pigment riboflavin (Rf) and the artificial dye Rose Bengal as photosensitisers. A complex mechanism, common to all the SDs studied, was elucidated through stationary photolysis, polarographic detection of oxygen uptake, fluorescence spectroscopy, time-resolved phosphorescence detection of O2(1Δg), and laser flash photolysis. Visible-light irradiation of aqueous and aqueous methanolic solutions of Rf (ca. 0.02 mmol/L) plus SD (ca. 0.5 mmol/L) photogenerated excited singlet and triplet Rf (1Rf* and 3Rf*). Under these experimental conditions, only 3Rf* is quenched either by oxygen, giving rise to O2(1Δg) by electronic energy transfer to dissolved ground-state oxygen, or by SD, yielding semireduced Rf through an electron-transfer process. Complementary experiments performed in pure water employing superoxide dismutase and sodium azide inhibition of oxygen uptake, in parallel with laser flash photolysis data, showed that O2·– is also formed, probably due to the reaction of the anion radical from Rf with dissolved oxygen, yielding also neutral, ground-state Rf. Both active oxygen species, namely, O2·– and O2(1Δg), are quenched by the SDs and, as a result, photodegradation of the SDs — each to a different extent — and photodegradation of the sensitiser itself were observed. The SDs that kinetically behave as the better physical quenchers of O2(1Δg), which are in principle good candidates as photoprotectors, namely, DAP and SFD, suffer photooxidation, exhibiting high to moderate oxygen consumption rates due to the O2·– oxidative pathway, whereas for SFNA and SFX, oxidation predominantly occurs through an O2(1Δg)-mediated mechanism. Microbiological results for SFX, taken as a representative SD, indicate that the photodegradation of the drug, upon visible-light Rf-sensitised irradiation, is accompanied by a net loss in bacteriostatic activity.Key words: photooxidation, singlet oxygen, superoxide radical anion, sulpha drugs.

N,N.N′,N′-tetramethylhydroethidine (TMHE) - in search for better probes for the detection of superoxide radical anion

2017 ◽  
Vol 108 ◽  
pp. S38
Author(s):  
Adam Sikora ◽  
Radosław Michalski ◽  
Micael Hardy ◽  
Olivier Ouari ◽  
Jan Adamus ◽  
...  
Keyword(s):  
Radical Anion ◽  
Superoxide Radical ◽  
Superoxide Radical Anion

scholarly journals Reactivity of Superoxide Radical Anion with Cyclic Nitrones:  Role of Intramolecular H-Bond and Electrostatic Effects

2007 ◽  
Vol 129 (26) ◽  
pp. 8177-8191 ◽  
Author(s):  
Frederick A. Villamena ◽  
Shijing Xia ◽  
John K. Merle ◽  
Robert Lauricella ◽  
Beatrice Tuccio ◽  
...  
Keyword(s):  
Radical Anion ◽  
Superoxide Radical ◽  
Electrostatic Effects ◽  
Superoxide Radical Anion ◽  
Cyclic Nitrones

Concerted double proton-transfer electron-transfer between catechol and superoxide radical anion

2017 ◽  
Vol 19 (38) ◽  
pp. 26179-26190 ◽  
Author(s):  
Jorge Quintero-Saumeth ◽  
David A. Rincón ◽  
Markus Doerr ◽  
Martha C. Daza
Keyword(s):  
Electron Transfer ◽  
Proton Transfer ◽  
Superoxide Anion ◽  
Radical Anion ◽  
Reaction Rate ◽  
Superoxide Radical ◽  
Superoxide Radical Anion ◽  
Double Proton Transfer

Catechol reacts with a superoxide anion via concerted double proton-transfer electron-transfer with a reaction rate that is dominated by tunneling.

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