Guest‐Facilitated Heteroleptic Assembly of Helical Anionocages Enables Reversible Chirality Modulation

• Published in: Angewandte Chemie International Edition Vol. 63; no. 8; pp. e202319552 - n/a
• Main Authors: Wang, Shanshan, Ye, Xuanli, Yang, Zaiwen, Li, Anyang, Sheng, Xinsong, Wang, Qiangqiang, Jia, Chuandong
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 19.02.2024
• Edition: International ed. in English
• Subjects: Assembly; Binding; Cage Compounds; Cages; Chirality; Circular dichroism; Crown ethers; Dichroism; Ethers; Ligands; Modulation; Potassium; Supramolecular Chemistry; Switch; Tetraethylammonium; Cage Compounds; Switch; Supramolecular Chemistry; Chirality
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202319552

We report a novel strategy for reversible modulation of the supramolecular chirality based on guest‐facilitated heteroleptic assembly of helical anionocages. Two triple‐stranded helical anionocages including a chiral cage 1 (A2L13) and a crown ether functionalized achiral cage 2 (A2L23) were synthesized by anion coordination of bis‐monourea‐based ligands and PhPO32−. Both cages exhibited favorable binding with tetraethylammonium TEA+ and cobaltocenium Cob+ (endo‐guest, bound in the cavity). Additionally, cage 2 could reversibly release and recapture the guests through binding the exo‐guest potassium ions (K+) in the crown ethers and subsequent removal of the K+ by [2,2,2]‐cryptand. The circular dichroism (CD) spectrum of cage 1 was not significantly affected by guest encapsulation or mixing with the “empty” cage 2. However, in the presence of both cage 2 and an endo‐guest/exo‐guest, the Cotton effects were reversed at 391 nm and significantly enhanced at 310 nm. This observation was attributed to the guest‐facilitated formation of heteroleptic cages that enabled effective chirality transfer from the chiral to the achiral ligands. The CD changes induced by K+ could be fully reversed by removing it with [2,2,2]‐cryptand. Sequential addition and removal of K+ allowed reversible modulation of the chirality for at least 10 cycles without significant attenuation. Guest‐facilitated heteroleptic assembly of helical anionocages has proved effective for chirality modulation of a supramolecular system, which was induced by effective chirality transfer from the chiral to achiral ligands. While both the endo‐guest (bound in the cavity) and exo‐guest (K+, bound in the crown ethers) are effective for chirality modulation, only that induced by K+ could be reversibly switched.