Synergistic regulation of metal-organic cage architectures via temperature- and solvent-driven atropisomerism.

Regulating multistimulus responses in artificial systems remains a challenge in smart material development. We present a versatile chemical switching system that precisely controls the self-assembly of metal-organic cages via temperature and solvent changes. The key component, cyclo[2](1,3-(4,6-dimethyl)benzene) (4-pyridine)[6](1,3-(4,6-dimethyl)benzene) (CP2), was generated as three atropisomers (1, 2, and 3) with Cs, C1, and C2v symmetries. Thermally, metastable isomers (1 and 2) convert into the stable isomer (3), which reacts with Pd2+ to form specific molecular cages. Depending on the solvent, either rectangular M2L2 cages (5' and 5) form in 1,4-dioxane or hexagonal M3L3 cages (6) in 1,1',2,2'-tetrachloroethane. The solvent dictates the cage type and enables reversible transformation between cages 5 and 6. Additionally, cage 5', formed from metastable isomer 1, can switch to other cage types (i.e., 5 or 6) depending on temperature and solvent conditions. This multipathway system offers a precise strategy for controlling self-assembly in smart materials.