关键词: 甲基紫精, 光诱导电子转移, 光催化, 自由基, 电子自旋共振

Abstract: The photoinduced electron transfer and photoc.atalysis reaction processes of methyl viologen(MV⁺⁺) with methyl alcohol, ethyl alcohol, propyl alcohol, iso-propyl alcohol, glycoland benzyl alcohol were studied by means of ESR method. Results indicated that some alcohols, which usually are very stable to UV rad.radiation, may be initiated to leading to photocatalytic decomposition and photo-oxidation in the presence of methyl viologen, and methylviologen played a key role of catalyst in photoreaction processes. As in the absence of oxygen, a very strong ESR signal of MV⁺ ion radical was observed in MV⁺⁺/C₂H₅OH systemirradiated for 10min, obviously, it implies that the photoinduced electron transfer processestook place between methyl viologen and ethyl alcohol; if radiation time was more long, the Hatoms and carbon-centered radicals might be detected, and MV⁺ radical would graduallydisappears. When the system was irradiated under the condition of bubbling O₂, the·OOH and carbon-centered radicals were observed and no signal of MV⁺ radical was given; the signal of·OOH radical weakened and·OH radical was formed in the presence of a fair amount ofwater, go a step further, with the increase of water amount, the signal intensity of·OOH radical was further weakened and vanished, at the same time, the signal intensity of·OH radical increased greatly. It is a very interesting fact that, as bubbing O₂, MV⁺⁺/C₆H₅CH₂OH system.could give a quite strong signal of superoxide anion radicals O₂^-, and MV⁺⁺/CH₃OH system might give a rather weak signal of O₂^-. Furthermore, if no O₂ existed, there would not be any observed reaction in MV-/CH₃OH system irradiated by UV,however, benzyl alcohol could be photocatalytically decomposed, thus leading to the production of large amount of benzyl-oxyl radical C₆H₅CH₂O and hydro-methyl radical CH₂OH.The process and mechanism of photoinduced electron transfer and related photocatalytic reactions for methyl viologen with some alcohols were investigated and discussed in detail.

Key words: Methyl viologen, Photoinduced electron transfer, Photocatalysis, Free radical, ESR