Photochemical Processes of Superbase Generation in Xanthone Carboxylic Salts

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 o...

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Published inAngewandte Chemie International Edition Vol. 62; no. 11; pp. e202214784 - n/a
Main Authors Ley, Christian, Siedel, Antoine, Bertaux, Tony, Croutxé‐Barghorn, Céline, Allonas, Xavier
Format Journal Article
LanguageEnglish
Published Germany Wiley Subscription Services, Inc 06.03.2023
Wiley-VCH Verlag
EditionInternational ed. in English
Subjects
Atomic energy levels
Caged Compounds
Carboxylic acids
Chemical Sciences
Chemical synthesis
Generators
Isocyanates
Photobase Generator
Photochemicals
Photochemistry
Photodecarboxylation
Photophysics
Ring opening polymerization
Spectroscopy
Triplet state
Photobase Generator
Caged Compounds
Photophysics
Photodecarboxylation
Photochemistry
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Summary: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 2.2×109 s−1. The photophysics and photochemistry of XnAA‐TBD photobase generator are described along with the rate constants of intersystem crossing and internal conversion underlying the release of TBD by a photodecarboxylation process occurring from T2 with a rate constant of 2.2×109 s−1.
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ISSN:1433-7851
1521-3773
DOI:10.1002/anie.202214784