Whereas the reversible reduction of azobenzenes has been known for decades, their oxidation is destructive and as a result has been notoriously overlooked. Here, we show that a chain reaction leading to quantitative Z → E isomerization can be initiated before reaching the destructive anodic peak potential. This hole-catalyzed pathway is accessible to all azobenzenes, without exception, and offers tremendous advantages over the recently reported reductive, radical-anionic pathway because it allows for convenient chemical initiation without the need for electrochemical setups and in the presence of air. In addition, catalytic amounts of metal-free sensitizers, such as methylene blue, can be used as excited-state electron acceptors, enabling a shift of the excitation wavelength to the far red of the azobenzene absorption (up to 660 nm) and providing quantum yields exceeding unity (up to 200%). Our approach will boost the efficiency and sensitivity of optically dense liquid-crystalline and solid photoswitchable materials.

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中文翻译：

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空穴催化作为高效且独立于波长的Z → E偶氮苯异构化的一般机理

尽管数十年来已知可逆还原偶氮苯，但是它们的氧化是破坏性的，因此臭名昭著地被忽略了。在这里，我们显示了导致定量Z → E的链反应异构化可以在达到破坏性的阳极峰值电势之前引发。所有偶氮苯均无例外地具有这种空穴催化的途径，并且与最近报道的还原性自由基-阴离子途径相比，具有巨大的优势，因为它允许方便的化学引发，而无需进行电化学设置和在空气中进行。此外，催化量的无金属敏化剂（例如亚甲基蓝）可以用作激发态电子受体，使激发波长移至偶氮苯吸收的远红光（最大660 nm）并提供量子产量超过统一（高达200％）。我们的方法将提高光密液晶和固态光敏开关材料的效率和灵敏度。

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