Architectural Control in Chiral Azobenzene Systems: Effects of Macrocycle and Cage Formation on Photoswitching...

Chiral photoswitchable architectures represent a frontier in molecular science, offering platforms where light can precisely control both molecular conformation and stereochemical environment. While promising, integrating photoswitches into robust 3D scaffolds to achieve superior thermal stability and functional responsiveness remains challenging. Here, we report the rational design and synthesis of an azobenzene-containing BINOL-derived chiral dialdehyde that undergoes Dynamic Covalent Chemistry to form a discrete macrocycle with a bisamine and a novel cage with a trisamine. We conducted a systematic, comparative study across the three systems to isolate the effect of increasing structural confinement on photo-switching characteristics. All three architectures-the aldehyde, macrocycle, and cage-exhibit reversible E↔Z photoisomerization of the azobenzene units under alternate irradiation with 370 and 456 nm light. In both the macrocycle and cage, the azobenzene units isomerize sequentially in both directions. Notably, both macrocyclization and cage formation significantly enhance photoswitching efficiency and substantially improve the thermal stability of the metastable Z-isomer, a crucial requirement for practical applications. Furthermore, the cage exhibits pronounced light-induced cavity modulation, resulting in significant shifts in its Circular Dichroism spectrum. These results establish molecular architecture as a crucial design principle for constructing highly responsive chiral hosts with tunable optical and structural features.