Doze Anna M, Fu Youxin, Di Donato Mariangela, Hilbers Michiel F, Luurtsema Gert, Elsinga Philip H, Buma Wybren Jan, Szymanski Wiktor, Feringa Ben L
Centre for Systems Chemistry, Stratingh Institute for Chemistry, Faculty of Science and Engineering, University of Groningen Nijenborgh 4 9747 AG Groningen The Netherlands
Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Centre Groningen Hanzeplein 1 9713 GZ Groningen The Netherlands.
Chem Sci. 2024 Jun 26;15(29):11557-11563. doi: 10.1039/d4sc01810a. eCollection 2024 Jul 24.
The light-induced photocycloaddition of 9,10-phenanthrenequinone (PQ) with electron-rich alkenes (ERA), known as the PQ-ERA reaction, is a highly attractive photoclick reaction characterized by its operational simplicity and high biocompatibility. One essential aspect of photoclick reactions is their high rate, however the limited solubility of PQs often requires the use of a co-solvent. Evaluating the effect of different co-solvents on the PQ-ERA reaction and their influence on the reaction rate, we discovered that sulfur-containing compounds, in particular the frequently used solubilizing co-solvent DMSO, quench the triplet state of the PQ. These experimental results, supported by nanosecond-microsecond and ultrafast transient absorption data, show that even minimal amounts of DMSO result in a decreased lifetime of the reactive triplet state, essential for the photoclick reaction. Without DMSO as co-solvent, exceptionally high photoreaction quantum yields up to 93% with only 1 equivalent ERA) and complete conversion in seconds can be achieved. With these outstanding efficiencies, the PQ-ERA reaction can be used without excess ERA and at low light intensities, facilitating photoclick transformations in various future applications.
9,10-菲醌（PQ）与富电子烯烃（ERA）的光诱导光环加成反应，即PQ-ERA反应，是一种极具吸引力的光点击反应，其特点是操作简单且生物相容性高。光点击反应的一个重要方面是反应速率高，然而PQ的溶解度有限，常常需要使用助溶剂。在评估不同助溶剂对PQ-ERA反应的影响及其对反应速率的作用时，我们发现含硫化合物，特别是常用的增溶助溶剂二甲基亚砜（DMSO），会猝灭PQ的三重态。这些实验结果得到纳秒-微秒和超快瞬态吸收数据的支持，表明即使极少量的DMSO也会导致光点击反应所必需的反应性三重态寿命缩短。在不使用DMSO作为助溶剂的情况下，仅使用1当量的ERA就能实现高达93%的异常高光化学反应量子产率，并且在数秒内即可完全转化。凭借这些出色的效率，PQ-ERA反应可以在不使用过量ERA且低光照强度的条件下进行，有助于在未来的各种应用中实现光点击转化。
