In Situ Photoisomerization of an Azobenzene‐Based Triple Helicate with a Prolonged Thermal Relaxation Time

The phosphate‐coordination triple helicates A2L3 (A = anion) with azobenzene‐spaced bis‐bis(urea) ligands (L) have proven to undergo a rare in situ photoisomerization (without disassembly of the structure) rather than the typically known, stepwise “disassembly‐isomerization‐reassembly” process. This is enabled by the structural self‐adaptability of the “aniono” assembly arising from multiple relatively weak and flexible hydrogen bonds between phosphate anion and bis(urea) units. Notably, the Z→E thermal relaxation rate of isomerized azobenzene unit is significantly decreased (up to 20‐fold) for the triple helicates compared to free ligands. Moreover, the binding of chiral guest cations inside the cavity of Z‐isomerized triple helicate can induce optically pure diastereomers, thus demonstrating a new strategy for making light‐activated chiroptical materials.