Controllable photomechanical bending of metal-organic rotaxane crystals facilitated by regioselective confined-space photodimerization

• Published in: Nature communications Vol. 13; no. 1; p. 2030
• Main Authors: Geng, Jun-shan, Mei, Lei, Liang, Yuan-yuan, Yuan, Li-yong, Yu, Ji-pan, Hu, Kong-qiu, Yuan, Li-hua, Feng, Wen, Chai, Zhi-fang, Shi, Wei-qun
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 19.04.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 140/131; 639/301/1005/1006; 639/638/298/303; 639/638/541/961; Bending machines; Confined spaces; Crystals; Deformation; Design; Energy; External stimuli; Fabrication; Humanities and Social Sciences; Irradiation; Laboratories; Ligands; Light; Light effects; Light irradiation; Mechanical analysis; Metals; Molecular machines; multidisciplinary; Radiation; Regioselectivity; Rotaxanes; Science; Science (multidisciplinary); Single crystals; Solid state; Styrene
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-29738-y

Molecular machines based on mechanically-interlocked molecules (MIMs) such as (pseudo) rotaxanes or catenates are known for their molecular-level dynamics, but promoting macro-mechanical response of these molecular machines or related materials is still challenging. Herein, by employing macrocyclic cucurbit[8]uril (CB[8])-based pseudorotaxane with a pair of styrene-derived photoactive guest molecules as linking structs of uranyl node, we describe a metal-organic rotaxane compound, U-CB[8]-MPyVB, that is capable of delivering controllable macroscopic mechanical responses. Under light irradiation, the ladder-shape structural unit of metal-organic rotaxane chain in U-CB[8]-MPyVB undergoes a regioselective solid-state [2 + 2] photodimerization, and facilitates a photo-triggered single-crystal-to-single-crystal (SCSC) transformation, which even induces macroscopic photomechanical bending of individual rod-like bulk crystals. The fabrication of rotaxane-based crystalline materials with both photoresponsive microscopic and macroscopic dynamic behaviors in solid state can be promising photoactuator devices, and will have implications in emerging fields such as optomechanical microdevices and smart microrobotics. The preparation of materials that display macro-mechanical responses to external stimuli is challenging. Here, the authors synthesize metal-organic rotaxane frameworks that contain photoactive axles as linkers; light irradiation triggers photodimerization of the ligands, which leads to macroscopic photomechanical bending of individual bulk crystals.