School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore.
Key Laboratory of Photochemistry, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
Angew Chem Int Ed Engl. 2016 Apr 4;55(15):4697-700. doi: 10.1002/anie.201600405. Epub 2016 Mar 10.
TiO2 photoredox catalysis has recently attracted much interest for use in performing challenging organic transformations under mild reaction conditions. However, the reaction scheme is hampered by the fact that TiO2 can only be excited by UV light of wavelengths λ shorter than 385 nm. One promising strategy to overcome this issue is to anchor an organic, preferably metal-free dye onto the surface of TiO2. Importantly, we observed that the introduction of a catalytic amount of the redox mediator TEMPO [(2,2,6,6-tetramethylpiperidin-1-yl)oxyl] ensured the stability of the anchored dye, alizarin red S, thereby resulting in the selective oxidation of organic sulfides with O2. This result affirms the essential role of the redox mediator in enabling the organic transformations by visible-light photoredox catalysis.
TiO2 光氧化还原催化最近受到关注，可在温和的反应条件下用于进行具有挑战性的有机转化。然而，该反应方案受到 TiO2 只能被波长 λ 小于 385nm 的紫外光激发的限制。克服这一问题的一种有前途的策略是将有机染料（最好是无金属）锚定在 TiO2 的表面上。重要的是，我们观察到引入少量氧化还原介体 TEMPO[(2,2,6,6-四甲基哌啶-1-基)氧]可确保锚定染料茜素红 S 的稳定性，从而导致 O2 选择性氧化有机硫化物。这一结果证实了氧化还原介体在通过可见光光氧化还原催化实现有机转化中的重要作用。
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