Photoreduction of methylviologen using methylacridine orange in the presence of triethanolamine in ethanol-water mixtures

被引:8
作者
Islam, SDM
Yoshikawa, Y
Fujitsuka, M
Ito, O [1 ]
Komatsu, S
Usui, Y
机构
[1] Tohoku Univ, Inst Chem React Sci, Aoba Ku, Sendai, Miyagi 9808577, Japan
[2] Ibaraki Univ, Dept Environm Sci, Mito, Ibaraki, Japan
关键词
methylacridine orange; methylviologen; laser photolysis; electron transfer; photoreduction;
D O I
10.1016/S1010-6030(00)00266-5
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Photoreduction of methylviologen (MV2+) by 10-methylacridine orange (MAO(+)) in the presence of triethanolamine (TEOA) has been investigated in ethanol-water mixed solvents by means of steady-state and laser-flash photolysis in visible/near-IR regions. The complete conversion from MV2+ to MV.+ was observed under the condition of [MV2+]>[MAO(+)] in the presence of an excess TEOA. By laser-flash photolysis measurements, the various rate constants for the electron transfer processes (k(et)) have been determined. The k(et) values for electron transfer from the triplet state of MAO(+) ((3)(MAO(+))*) to MV2+, which is the initial step of oxidative route, are in the order of 10(8) M-1 s(-1). The rate constant of back electron transfer between the ion radicals (MV.+ and (MAO(+))(.+)) was ca. 3 x 10(8) M-1 s(-1), while the back electron-transfer process was suppressed on addition of TEOA. The k(et) values from TEOA to (3)(MAO(+))*, which is the initial step of reductive route, are in the order of 10(5) M-1 s(-1). The k(et) value for electron transfer from (MAO(+))(.-) to MV2+ was estimated to be 4.7 x 10(8) M-1 s(-1). Contributions of the oxidative and reductive routes of (3) (MAO(+))* to the MV.+ formation vary with TEOA concentration. High quantum yields for the MV.+ formation were evaluated. The effects of the ion salt and solvents on the rate constants and quantum yields were found. (C) 2000 Elsevier Science S.A. All rights reserved.
引用
收藏
页码:155 / 161
页数:7
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