Weick Fabian, Hagmeyer Nina, Giraud Madeleine, Dietzek-Ivanšić Benjamin, Wagenknecht Hans-Achim
Institute of Organic Chemistry, Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 6, 76131, Karlsruhe, Germany.
Institute of Physical Chemistry, Friedrich Schiller University Jena, Lessingstraße 4, 07743, Jena, Germany.
Chemistry. 2023 Nov 24;29(66):e202302347. doi: 10.1002/chem.202302347. Epub 2023 Oct 11.
Aryl chlorides as substrates for arylations present a particular challenge for photoredox catalytic activation due to their strong C(sp )-Cl bond and their strong reduction potential. Electron-rich N-phenylphenothiazines, as organophotoredox catalysts, are capable of cleaving aryl chlorides simply by photoinduced electron transfer without the need for an additional electrochemical activation setup or any other advanced photocatalysis technique. Due to the extremely strong reduction potential in the excited state of the N-phenylphenothiazines the substrate scope is high and includes aryl chlorides both with electron-withdrawing and electron-donating substituents. We evidence this reactivity for photocatalytic borylations and phosphonylations. Advanced time-resolved transient absorption spectroscopy in combination with electrochemistry was the key to elucidating and comparing the unusual photophysical properties not only of the N-phenylphenothiazines, but also of their cation radicals as the central intermediates in the photocatalytic cycle. The revealed photophysics allowed the excited-state and radical-cation properties to be fine-tuned by the molecular design of the N-phenylphenothiazines; this improved the photocatalytic activity.
由于芳基氯化物具有很强的C(sp )-Cl键和很强的还原电位，因此作为芳基化反应的底物，它们对光氧化还原催化活化提出了特殊的挑战。富电子的N-苯基吩噻嗪作为有机光氧化还原催化剂，能够通过光诱导电子转移简单地裂解芳基氯化物，而无需额外的电化学活化装置或任何其他先进的光催化技术。由于N-苯基吩噻嗪在激发态具有极强的还原电位，其底物范围很广，包括带有吸电子和供电子取代基的芳基氯化物。我们证明了这种光催化硼化和膦酰化反应的活性。先进的时间分辨瞬态吸收光谱与电化学相结合，是阐明和比较N-苯基吩噻嗪及其阳离子自由基作为光催化循环核心中间体的异常光物理性质的关键。所揭示的光物理性质使得通过N-苯基吩噻嗪的分子设计来微调激发态和自由基阳离子性质成为可能；这提高了光催化活性。
