Optimizing Isomerization in Azobenzene Organic Cages through Imine Bond Reduction

Photoswitchable systems are used in chemical sensing, separations, and stimuli-responsive materials and studied for switching efficiency, but the compositional impact on molecule stability is underexplored. Herein, we evaluate the compositional influences on the transformational stability of organic cages containing azobenzene formed via an amine or an imine bond. The flexible amine bond increases the efficiency of the trans- to cis-isomerization (E → Z transition), increasing the stability of the cis-configuration (ZZZ) with no spontaneous isomerization due to the formation of a metastable structure that needs to be overcome via further light exposure. Density functional theory modeling of the ZZZ (trans) and EEE (cis) isomers of the azobenzene cages identified transfer energies between the isomers and differences in the cage geometries. Binding energy calculations predicted gas separation due to structural variation following isomerization.