Robust Red‐Absorbing Donor‐Acceptor Stenhouse Adduct Photoswitches

• Published in: Chemistry : a European journal Vol. 30; no. 30; pp. e202400621 - n/a
• Main Authors: Philip, Abbey M., Krogh, Marie E., Laursen, Bo W.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 28.05.2024
• Subjects: Chromophores; Design optimization; Donor-Acceptor Stenhouse Adducts; Doppler effect; Ground state; Modularity; Photochromes; Photoswitches; Polymer films; Polymer Thin Films; Polymers; Red shift; Red-Light Photoswitching; Robustness (mathematics); Separation; Structure-Function Relationship; Structure-function relationships; Thin films; Photoswitches; Donor-Acceptor Stenhouse Adducts; Red-Light Photoswitching; Structure-Function Relationship; Polymer Thin Films
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202400621

Donor‐Acceptor Stenhouse Adduct (DASA), a class of push‐pull negative photochrome, has received large interest lately owing to its versatile synthesis, modularity and excellent photoswitching in solutions. From a technological perspective, it is imperative for this class of photoswitches to work robustly in solid state, e. g. thin films. We feature a molecular framework for the optimized design of DASAs by introducing a new thioindoline donor (D3) and assessing its performance against known 2nd generation indoline‐based donors. The systematic structure‐function investigations suggest that to achieve robust reversible photoswitching, a ground state with low charge separation is desired. DASAs with stronger electron donors and a larger charge separation in the ground state result in a low population of the photothermalstationary state (PTSS) and reduced photostability. The DASA with thioindoline donor (D3A3) seems to be a special case among the donor series as it causes a red shift (ca. 15 nm), however with less polarization of the ground state and marginally better photostability as compared to the unsubstituted 2‐methyl indoline (D1A3). We also emphasize the consideration of the key additional factors that can modulate the red‐light photoswitching properties of DASA chromophores in polymer thin films, which might not be dominant in homogenous solution state. Structure‐property guidelines are disclosed for creating robust donor‐acceptor Stenhouse adduct (DASA) photochromes. A comprehensive investigation has revealed that a DASA photochrome with a low degree of charge separation is desired to achieve a robust, reversible photoswitching. Other indirect factors that could modulate the DASA photoswitching in polymer thin films are also discussed in detail.