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 upon irradiation.
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.
The photophysical and photochemical properties of sulfoxide and sulfone derivatives of hemithioindigo photoswitches are scrutinized and compared to the unoxidized parent chromophores. Oxidation results in significantly blue‐shifted absorptions and mostly reduction of photochromism while thermal stabilities of individual isomers remain largely unaltered. Effective photoswitching takes place at shorter wavelengths compared to parent hemithioindigos and high isomeric yields can be obtained reversibly in the respective photostationary states. Reversible solid‐state photoswitching is observed for a twisted sulfone derivative accompanied by visible color changes. These results establish oxidized hemithioindigo photoswitches as promising and versatile tools for robust light‐control of molecular behavior for a wide range of applications.
Subcomponent self-assembly relies on cation coordination whereas the roles of anions, often only emerging during self-assembly, are growing. When sites for anions are instead pre-programmed, they have the potential to...
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.
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