Conformational Selectivity and Chiral Self-Assembly Structures of Crown Ethers on Metal Surfaces

Crown ethers (CEs), macrocyclic polyethers, have attracted significant attention in supramolecular chemistry. It is known that they have many isomers due to their flexibility. It is challenging to select some exact conformation and tune the following self-assembly structure of CEs, and it has rarely been reported to date. Herein, by choosing 18-crown-6-ether and dibenzo-18-crown-6-ether for study, we report an effective stereoisomeric selectivity of CEs by a strategy of both chemical modification and CEs hosting Na/K ions. The conformational difference in CEs can further tune the molecular interactions, resulting in the chiral self-assembly structures of CEs. By the combination of scanning tunneling microscopy, density functional theory, and X-ray photoelectron spectroscopy, this study reveals the underlying mechanism of CEs in both conformational selectivity and the formation of chiral assembly structures.