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) (<b>CP2</b>), was generated as three atropisomers (<b>1</b>, <b>2</b>, and <b>3</b>) with <i>C</i>_s, <i>C</i>₁, and <i>C</i>_2v symmetries. Thermally, metastable isomers (<b>1</b> and <b>2</b>) convert into the stable isomer (<b>3</b>), which reacts with Pd²⁺ to form specific molecular cages. Depending on the solvent, either rectangular M₂L₂ cages (<b>5'</b> and <b>5</b>) form in 1,4-dioxane or hexagonal M₃L₃ cages (<b>6</b>) in 1,1',2,2'-tetrachloroethane. The solvent dictates the cage type and enables reversible transformation between cages <b>5</b> and <b>6</b>. Additionally, cage <b>5</b>', formed from metastable isomer <b>1</b>, can switch to other cage types (i.e., <b>5</b> or <b>6</b>) depending on temperature and solvent conditions. This multipathway system offers a precise strategy for controlling self-assembly in smart materials.