Light‐Fueled Transformations of a Dynamic Cage‐Based Molecular System

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 Zopen 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.

Shining a Light on Dissipative Supramolecular Assemblies

“…Back-to-back, Feringa et al 10c presented a dissipative photoswitchable imine cage based on the tripodal tris(2-aminoethyl)amine ( Tri ) precursor and ditopic 3,3′-(diazene-1,2-diyl)dibenzaldehyde ( Di ). These building blocks readily form an E , E , E - Tri 2 Di 3 cage, 11 first synthesized by Bauer and Vögtle, 12 which is reversibly convertible into a mixture of different cages PSS 340 - Tri 2 Di 3 (containing the various isomeric cages E , E , Z - Tri 2 Di 3 , E , Z , Z - Tri 2 Di 3 , and Z , Z , Z - Tri 2 Di 3 ) by irradiation with light of the wavelength of 340 nm and vice versa at 420 nm (Figure 4 ).…”