Photoreduction of nitronaphthalenes in benzene by N,N-dialkylanilines and triethylamine:: a time-resolved UV-vis spectroscopic study
Photoreduction of nitronaphthalenes in benzene by N,N-dialkylanilines and triethylamine:: a time-resolved UV-vis spectroscopic study
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DOI：
10.1039/b202889c
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发表时间：
2002-01-01
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影响因子：
--
通讯作者：
Görner, H
中科院分区：
文献类型：
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作者：
Görner, H
采用时间分辨紫外-可见光谱技术，在354nm激光脉冲下研究了室温下苯中1-甲氧基-4-硝基萘和1-和2-硝基萘的三重态。三态与N， N-二甲基苯胺和N， N-二乙基苯胺反应；速率常数接近扩散控制极限。在340 nm处有峰的瞬态反应是由于-氨基烷基自由基PhN(R)(CHR)- c环'由二烷基苯胺的h原子转移形成的。这种自由基的衰变发生在几分钟内，如在340-410纳米范围内的漂白所观察到的。因此，硝基萘最终转化为稳定的产物，如亚硝基萘，并发生二烷基苯胺的脱烷基反应。三乙胺猝灭的三重态生成的自由基阴离子arno2作为乙腈的中间体，在苯中生成共轭酸(ArNO2H)- n -环。这些自由基被认为在ms时间范围内通过缓慢终止最终生成亚硝基萘。在三种胺存在的情况下，三种硝基萘在苯中发生分解，最大量子产率为0.1-0.3。讨论了二烷基苯胺的光去甲基化机理和硝基萘的光还原反应。
The triplet state of 1-methoxy-4-nitronaphthalene and 1- and 2-nitronaphthalene in benzene at room temperature was studied by time-resolved UV-vis spectroscopy with ns laser pulses at 354 nm. The triplet state reacts with N, N-dimethylaniline and N, N-diethylaniline; the rate constant is close to the diffusion-controlled limit. A transient with a peak at 340 nm is attributed to the alpha-aminoalkyl radical, PhN(R)(CHR)-C-circle', being formed by H-atom transfer from the dialkylaniline. Decay of this radical takes place within a few mus, as observed by bleaching in the 340-410 nm range. Thereby, a nitronaphthalene is eventually converted into stable products, such as nitrosonaphthalene, and dealkylation of the dialkylaniline occurs. Triplet quenching by triethylamine yields the radical anion, ArNO2radical anion, as an intermediate in acetonitrile and the conjugate acid, (ArNO2H)-N-circle, in benzene. These radicals are suggested to ultimately yield nitrosonaphthalenes by slow termination in the ms time range. Decomposition of the three nitronaphthalenes in benzene takes place in the presence of the three amines with maximum quantum yields of 0.1-0.3. The mechanisms of photodemethylation of the dialkylanilines and the photoreduction reactions of the nitronaphthalenes are discussed.