All-Red-Light Photoswitching of Indirubin Controlled by Supramolecular Interactions

09 August 2021, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Red light responsiveness of photoswitches is a highly desired property for many important application areas such as biology or material sciences. The main approach to elicit this property uses strategic substitution of long known photoswitch motives such as azobenzenes or diarylethenes. Only very few photoswitches possess inherent red-light absorption of their core chromophore structures. Here we present a strategy to convert the long known purple indirubin dye into a prolific red light responsive photoswitch. In a supramolecular approach its photochromism can be changed from a negative to a positive one while at the same time significantly higher yields of the metastable E isomer are obtained. E to Z photoisomerization can then also be induced by red light of longer wavelengths. Indirubin therefore represents a unique example of reversible photoswitching using entirely red light for both switching directions.



Supplementary materials

Supporting Information
Details of synthesis, photochemical, photophysical and thermal behavior, theoretical description, supramolecular interactions, crystal structural data. Additional theoretically obtained optimized structures on different levels of theory are available by request from the authors.


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