Mapping the multi-step mechanism of a photoredox catalyzed atom-transfer radical polymerization reaction by direct observation of the reactive intermediates.
Mapping the multi-step mechanism of a photoredox catalyzed atom-transfer radical polymerization reaction by direct observation of the reactive intermediates.
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DOI：
10.1039/d0sc01194k
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发表时间：
2020-04-16
期刊：
影响因子：
8.4
通讯作者：
Orr-Ewing AJ
中科院分区：
文献类型：
--
作者：
Lewis-Borrell L;Sneha M;Bhattacherjee A;Clark IP;Orr-Ewing AJ
迄今为止，光氧化还原催化新应用的快速发展已经超过了对合理设计新型催化剂重要的机理研究。在这里，我们报告使用超快瞬态吸收光谱方法来揭示多个连续步骤的有机催化原子转移自由基聚合反应的机理和动力学细节。研究的聚合体系包括N，N-二芳基二氢吩嗪光催化剂，自由基引发剂（2-溴丙酸甲酯）和单体（异戊二烯）。时间分辨光谱测量跨越亚皮秒到微秒（即，几乎8个数量级的时间）跟踪关键活性中间体的形成和损失。这些测量识别负责电子转移的光催化剂的激发态和参与传播反应的自由基中间体，以及量化它们的寿命。研究结果将N，N-二芳基二氢吩嗪有机光催化剂的性质与催化循环中连续步骤的速率联系起来。在多步光氧化还原催化聚合反应期间，通过瞬态吸收光谱实时跟踪短寿命中间体。
The rapid development of new applications of photoredox catalysis has so far outpaced the mechanistic studies important for rational design of new classes of catalysts. Here, we report the use of ultrafast transient absorption spectroscopic methods to reveal both mechanistic and kinetic details of multiple sequential steps involved in an organocatalyzed atom transfer radical polymerization reaction. The polymerization system studied involves a N,N-diaryl dihydrophenazine photocatalyst, a radical initiator (methyl 2-bromopropionate) and a monomer (isoprene). Time-resolved spectroscopic measurements spanning sub-picosecond to microseconds (i.e., almost 8 orders of magnitude of time) track the formation and loss of key reactive intermediates. These measurements identify both the excited state of the photocatalyst responsible for electron transfer and the radical intermediates participating in propagation reactions, as well as quantifying their lifetimes. The outcomes connect the properties of N,N-diaryl dihydrophenazine organic photocatalysts with the rates of sequential steps in the catalytic cycle. Short-lived intermediates are tracked in real-time by transient absorption spectroscopy during a multi-step photoredox catalysed polymerization reaction.
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影响因子：
15
作者：
McCarthy BG;Pearson RM;Lim CH;Sartor SM;Damrauer NH;Miyake GM
通讯作者：
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影响因子：
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Bhattacherjee, Aditi;Sneha, Mahima;Orr-Ewing, Andrew J.
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