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Titolo:
Mechanism of formation of the MV center dot+ radical during the UV excitation of methylviologen
Autore:
Mendez, EE; Crespo-Hernandez, C; Figueroa, R; Arce, R; Quinones, E;
Indirizzi:
Univ Puerto Rico, Dept Chem, San Juan, PR 00931 USA Univ Puerto Rico San Juan PR USA 00931 Dept Chem, San Juan, PR 00931 USA
Titolo Testata:
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY
fascicolo: 1, volume: 142, anno: 2001,
pagine: 19 - 24
SICI:
1010-6030(20010820)142:1<19:MOFOTM>2.0.ZU;2-U
Fonte:
ISI
Lingua:
ENG
Soggetto:
ELECTRON-TRANSFER REACTIONS; LASER FLASH-PHOTOLYSIS; CAGE ESCAPE YIELDS; HYDROGEN EVOLUTION; METHYL VIOLOGEN; ARTIFICIAL PHOTOSYNTHESIS; MOLECULAR ASSEMBLIES; CHARGE SEPARATION; PULSE-RADIOLYSIS; AQUEOUS-SOLUTION;
Keywords:
methylviologen radical; UV excitation; quantum yield; photodestruction;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
37
Recensione:
Indirizzi per estratti:
Indirizzo: Quinones, E Univ Puerto Rico, Dept Chem, POB 23346, San Juan, PR 00931 USAUniv Puerto Rico POB 23346 San Juan PR USA 00931 PR 00931 USA
Citazione:
E.E. Mendez et al., "Mechanism of formation of the MV center dot+ radical during the UV excitation of methylviologen", J PHOTOCH A, 142(1), 2001, pp. 19-24

Abstract

The UV illumination of diluted aqueous solutions of methylviologen (MV2+) leads to the formation of the methylviologen radical (MV.+), without the use of microheterogeneous materials or sacrificial electron donors. In the absence Of O-2 the MV.+ radical remains in solution for hours. The formation mechanism of MV.+ was investigated employing the laser flash photolysis technique. The hydrated electron (e(aq)(-)) band and the characteristic bands of the MV.+ radical at 395 and 605 nm were detected in the MV2+ transient absorption spectra. This indicates that (1) MV2+ is ionized at 266 nm and (2) the e(aq) (-) + MV2+ reaction is a source of the MV.+ radical. The rate constant for this reaction was measured at pH 6.5 to be (3.8 +/- 0.1) x 10(10) M-1 s(-1) and its magnitude is in good agreement with literature values. The ionization quantum yield of 0.16 was determined for MV2+ using KI as areference actinometer. The photodestruction quantum yield of MV2+ was calculated to be (8.7 +/- 0.5) x 10(-3) molecules/quantum. The formation quantum yield of MV.+ was measured at the two absorption maxima of the radical, phi (395 nm) = (4.8 +/- 0.5) x 10(-3) and phi (605 nm) = (5.1 +/- 0.3) x 10(-3) molecules/quantum. (C) 2001 Elsevier Science B.V. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 20/09/20 alle ore 07:59:23