Light‐Fueled Transformations of a Dynamic Cage‐Based Molecular System. Issue 9 (19th January 2023)

• Record Type: Journal Article
• Authors: Ovalle, Marco; Kathan, Michael; Toyoda, Ryojun; Stindt, Charlotte N.; Crespi, Stefano; Feringa, Ben L.
• Is Part Of: Angewandte Chemie international edition. Volume 62:Issue 9(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-19
• Subjects: Dynamic Covalent Chemistry -- Molecular Machines -- Photoswitches -- Self-Assembly -- Out-Of-Equilibrium Chemistry; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202214495
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: In a chemical equilibrium, the formation of high‐energy species—in a closed system—is inefficient due to microscopic reversibility. Here, we demonstrate how this restriction can be circumvented by coupling a dynamic equilibrium to a light‐induced E / Z isomerization of an azobenzene imine cage. The stable E ‐cage resists intermolecular imine exchange reactions that would "open" it. Upon switching, the strained Z ‐cage isomers undergo imine exchange spontaneously, thus opening the cage. Subsequent isomerization of the Z ‐open compounds yields a high‐energy, kinetically trapped E ‐open species, which cannot be efficiently obtained from the initial E ‐cage, thus shifting an imine equilibrium energetically uphill in a closed system. Upon heating, the nucleophile is displaced back into solution and an opening/closing cycle is completed by regenerating the stable all‐ E ‐cage. Using this principle, a light‐induced cage‐to‐cage transformation is performed by the addition of a ditopic aldehyde. Abstract : The stability of a photoswitchable imine cage has been altered by irradiation with light. This facilitates the transformation of the cage upon application of external stimuli. A four‐step opening/closing cycle has been achieved by controlling the rates of nuchleophile/imine exchange with an amine, which drives the system out‐of‐equilibrium. Furthermore, a light‐induced cage‐to‐cage transformation has been demonstrated using the same principle.