Ley Christian, Siedel Antoine, Bertaux Tony, Croutxé-Barghorn Céline, Allonas Xavier
Laboratoire de Photochimie et d'Ingénierie Macromoléculaire, Université de Haute Alsace, 3b rue A. Werner, 68200, Mulhouse, France.
Angew Chem Int Ed Engl. 2023 Mar 6;62(11):e202214784. doi: 10.1002/anie.202214784. Epub 2023 Feb 2.
Photobase generators are species that allow the photocatalysis of various reactions, such as thiol-Michael, thiol-isocyanate, and ring-opening polymerization reactions. However, existing compounds have complex syntheses and low quantum yields. To overcome these problems, photobase generators based on the photodecarboxylation reaction were developed. We synthesized and studied the photochemistry and photophysics of two xanthone photobase, their carboxylic acid precursors, and their photoproducts to understand the photobase generation mechanism. We determined accurate quantum yields of triplet states and photobase generation. The effect of the intermediate radical preceding the base release was demonstrated. We characterized the photophysics of the photobase by femtosecond spectroscopy and showed that the photodecarboxylation process occurred from the second excited triplet state with a rate constant of 2.2×10 s .
光碱产生剂是能够使各种反应发生光催化作用的物种，比如硫醇-迈克尔反应、硫醇-异氰酸酯反应以及开环聚合反应。然而，现有的化合物合成过程复杂且量子产率较低。为克服这些问题，基于光脱羧反应的光碱产生剂得以开发。我们合成并研究了两种呫吨酮光碱、它们的羧酸前体及其光产物的光化学和光物理性质，以了解光碱产生机制。我们测定了三重态和光碱产生的准确量子产率。证明了碱释放之前中间自由基的作用。我们通过飞秒光谱对光碱的光物理性质进行了表征，并表明光脱羧过程发生于第二激发三重态，速率常数为2.2×10 s 。
