Photoinduced Mechanical Motions of Pseudorotaxane Crystals Composed of Azobenzene and Ferrocenyl Groups on an Axle and a Crown Ether Ring
mediaposted on 22.10.2020, 12:12 by Shao-Chi Cheng, Chi-Hsien Wang, Yi-Chia Lin, Yoshitaka Tsuchido, Yuji Suzaki, Yoshihisa Sei, Ting-Shen Kuo, Masaki Horie
This work describes the design and characterization of photoresponsive dynamic pseudorotaxane crystals composed of azobenzene and ferrocenyl groups in an ammonium cation axle component threaded through dibenzocrown-8 ether rings. Pseudorotaxanes provide flexibility for cis and trans isomerization of azobenzene groups in a crystal state, enabling reversible bending motions under alternating 360 and 445 nm laser irradiation. For such bending motions, strained azobenzene structures were essential; these motifs were obtained by increasing the bulkiness of the substituents on the axle and ring molecules. In addition, the crystals showed photosalient effects, such as jumping motions, under 445 nm laser irradiation. These motions were assisted by the photoabsorption of the ferrocenyl group, which converted 445 nm laser light into heat. The maximum lifting weight accompanied by the photoinduced mechanical motion of a particular crystal was estimated to be 9600 times the crystal weight. These pseudorotaxane crystals exhibit promising features for applications in micro-nanometer-sized miniature mechanical devices.
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Ferrocenyl Groupsferrocenyl grouptrans isomerizationring moleculespseudorotaxane crystals exhibitpseudorotaxane crystalsferrocenyl groups445 nm laser lightPhotoinduced Mechanical Motionscrystal stateCrown Ether Ring445 nm laser irradiationazobenzene groupsazobenzene structurescrystal weightammonium cation axle componentPseudorotaxane Crystals Composedphotosalient effects9600 times