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首页> 外文期刊>Chemistry: A European journal >Competitive decay pathways of the radical ions formed by photoinduced electron transfer between quinones and 4,4 '-dimethoxydiphenylmethane in acetonitrile
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Competitive decay pathways of the radical ions formed by photoinduced electron transfer between quinones and 4,4 '-dimethoxydiphenylmethane in acetonitrile

机译：醌和4,4'-二甲氧基二苯甲烷之间的醌和4,4'-二甲氧基二苯甲烷之间的光诱导电子转移形成的自由基离子的竞争性衰减途径

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The reactivity of the cation radical of (4-MeOC6H4)(2)CH2 photosensitized by 1,4-benzoquinone (BQ), 2,5-dichloro-1,4-benzoquinone (Cl(2)BQ), and tetrachloro-1,4-benzoquinone (chloranil, CA) was investigated in acetonitrile. The main photoreaction products obtained by steady-state irradiation were identified to be: (4-MeOC6H4)(2)-CHOC6H4OH, sensitized by BQ; (4-MeOC6H4)(2)CHCI, sensitized by Cl(2)BQ; (4-MeOC6H4)(2)CHOH, sensitized by CA. The mechanism of their formation was investigated by nanosecond laser flash photolysis that allowed transient species (radical ions, neutral radicals, and ions) to be detected and characterized in terms of absorption spectra, formation quantum yields, and decay rate constants. For all systems, the interaction between the triplet quinone (Q) and (4-MeOC6H4)(2)CH2 produced the corresponding radical ions (quantum yield phi greater than or equal to 0.72) which mainly decay by back electron transfer processes. Less efficient reaction routes for the radical ions (Q)is approximately equal to and (4-MeOC6H4)(2)CH2.+ were also: i) the proton-transfer process with the formation of the radical (4-MeOC6H4)(2)CH. by use of Cl(2)BQ; ii) the hydrogen-transfer process with the formation of the cation (4-MeOC6H4)2CH(+) in the case of CA. Instead, BQ sensitized a much higher yield of BQH(.) and (4-MeOC6H4)(2)CH., mainly by the direct interaction of triplet BQ with (4-MeOC6H4)(2)CH2 It was also shown that the presence of salts decreases significantly the rate of the back electron transfer process and enhances the quantum yields of formation of the neutral radicals and ions when Cl(2)BQ and CA are used, respectively The behavior of (BQ)is approximately equal to, (Cl(2)BQ)is approximately equal to, and (CA)is approximately equal to appears to be mainly determined by the Mulliken charges on the oxygen atom obtained from quantum mechanical calculations with the model B3LYP/6-311G(d,p). Spin densities seem to be much less important. [References: 27]
机译：1,4-苯醌（BQ），2,5-二氯-1,4-苯醌（Cl（2）BQ）和四氯-1光敏的（4-MeOC6H4）（2）CH2的阳离子自由基的反应性在乙腈中研究了4-4-苯醌（氯醌，CA）。通过稳态辐射获得的主要光反应产物被鉴定为：（4-MeOC6H4）（2）-CHOC6H4OH，经BQ敏化; （4-MeOC6H4）（2）CHCl，由Cl（2）BQ增敏; （4-MeOC6H4）（2）CHOH，由CA致敏。通过纳秒激光闪光光解法研究了它们的形成机理，该方法允许检测瞬态物质（自由基离子，中性自由基和离子），并根据吸收光谱，形成量子产率和衰减速率常数进行表征。对于所有系统，三重态醌（Q）与（4-MeOC6H4）（2）CH2之间的相互作用产生了相应的自由基离子（量子产率phi大于或等于0.72），这些离子主要通过反向电子转移过程而衰减。自由基离子（Q）的效率较低的反应路线大约等于和（4-MeOC6H4）（2）CH2。+也为：i）形成自由基（4-MeOC6H4）（2）的质子转移过程CH。通过使用Cl（2）BQ; ii）在CA情况下，氢转移过程会形成阳离子（4-MeOC6H4）2CH（+）。取而代之的是，BQ敏化了更高的BQH（。）和（4-MeOC6H4）（2）CH。产量，这主要是由于三重态BQ与（4-MeOC6H4）（2）CH2的直接相互作用所致。分别使用Cl（2）BQ和CA时，盐的含量显着降低了背电子转移过程的速率并提高了中性自由基和离子形成的量子产率。（BQ）的行为近似等于（Cl （2）BQ）大约等于，而（CA）大约等于似乎主要由模型B3LYP / 6-311G（d，p）的量子力学计算获得的氧原子上的Mulliken电荷确定。自旋密度似乎不那么重要。 [参考：27]

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