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

Liang, Jiaqi; Peng, Li-Jun; Zhu, Ke-Lin; Li, Zhi-Ao; Chen, Xu-Lang; Yang, Yu-Dong; Li, Qian; Bi, Qian-Nan et al. · Proc Natl Acad Sci U S A · 2025

basic_science · Level V

Where this comes from

Abstract

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><sub>s</sub>, <i>C</i><sub>1</sub>, and <i>C</i><sub>2v</sub> symmetries. Thermally, metastable isomers (<b>1</b> and <b>2</b>) convert into the stable isomer (<b>3</b>), which reacts with Pd<sup>2+</sup> to form specific molecular cages. Depending on the solvent, either rectangular M<sub>2</sub>L<sub>2</sub> cages (<b>5'</b> and <b>5</b>) form in 1,4-dioxane or hexagonal M<sub>3</sub>L<sub>3</sub> 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.