A Toolbox Approach To Construct Broadly Applicable Metal-Free Catalysts for Photoredox Chemistry: Deliberate Tuning of Redox Potentials and Importance of Halogens in Donor-Acceptor Cyanoarenes
A Toolbox Approach To Construct Broadly Applicable Metal-Free Catalysts for Photoredox Chemistry: Deliberate Tuning of Redox Potentials and Importance of Halogens in Donor-Acceptor Cyanoarenes
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DOI：
10.1021/jacs.8b08933
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发表时间：
2018-11-14
影响因子：
15
通讯作者：
Zeitler, Kirsten
中科院分区：
文献类型：
--
作者：
Speckmeier, Elisabeth;Fischer, Tillmann G.;Zeitler, Kirsten
特定光催化剂的有针对性的选择已被证明对于成功实现具有挑战性的光氧化还原催化转化发挥着关键作用。在此，我们以 1,2,3,5-四（咔唑-9-基）-4,6-二氰基苯（4CzIPN）为起点，成功实施了一系列基于氰基芳烃的纯有机供体-受体光催化剂的合理设计策略。对供体取代基和受体分子核心的系统修饰使我们能够识别强氧化性和强还原性催化剂（例如，对未活化的萘酚三氟甲磺酸酯进行前所未有的脱氟），这还提供了具有可预测趋势的非常平衡的氧化还原电位。特别是卤素芳烃核心取代有助于我们有针对性地改变催化剂的氧化还原性能。基于其卓越的电化学和光物理特性，所有新颖的纯有机光氧化还原催化剂在三种具有挑战性的、机械上不同的基准反应类别（需要平衡、高氧化性或强还原性）中进行了评估，以证明它们作为可定制光催化剂的巨大潜力，超越并补充了流行的典型最佳光催化剂。
The targeted choice of specific photocatalysts has been shown to play a critical role for the successful realization of challenging photoredox catalytic transformations. Herein, we demonstrate the successful implementation of a rational design strategy for a series of deliberate structural manipulations of cyanoarene-based, purely organic donor-acceptor photocatalysts, using 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as a starting point. Systematic modifications of both the donor substituents as well as the acceptors' molecular core allowed us to identify strongly oxidizing as well as strongly reducing catalysts (e.g., for an unprecedented detriflation of unactivated naphthol triflate), which additionally offer remarkably balanced redox potentials with predictable trends. Especially halogen arene core substitutions are instrumental for our targeted alterations of the catalysts' redox properties. Based on their preeminent electrochemical and photophysical characteristics, all novel, purely organic photoredox catalysts were evaluated in three challenging, mechanistically distinct classes of benchmark reactions (either requiring balanced, highly oxidizing or strongly reducing properties) to demonstrate their enormous potential as customizable photocatalysts, that outperform and complement prevailing typical best photocatalysts.