Chiral Supramolecular Structures Formed by Dibenzo-18-crown-6-ether and NaCl/KCl on Au(111) and Cu(111) Surfaces

The host-guest chemistry of crown ethers can be applied to construct chiral supramolecular nanostructures on metal surfaces. In this study, dibenzo-18-crown-6-ether (DB18C6E) molecules and alkali metal salts (NaCl and KCl) were codeposited on Au(111) and Cu(111) surfaces, and the formed supramolecular structures of the DB18C6E-Na/K complexes were characterized by low-temperature (78 K) scanning tunneling microscopy (LT-STM) and X-ray photoelectron spectroscopy (XPS) in an ultrahigh vacuum (2 × 10^-10 mbar). On the Au(111) surface, a sole chiral supramolecular architecture of DB18C6E-Na/K complexes with ordered NaCl/KCl molecular and Cl atomic adsorptions is identified. In addition, two different chiral supramolecular networks of DB18C6E-K complexes with ordered KCl molecular adsorption are observed. On the Cu(111) surface, a zigzag chain and a chiral supramolecular architecture of DB18C6E-Na complexes without ordered NaCl molecular participation are observed. And three chiral supramolecular architectures of DB18C6E-K complexes without ordered KCl molecular participation are confirmed. DFT and XPS analyses further supported the formation of DB18C6E-Na/K complexes, their configuration change, and self-assembly difference on both Au(111) and Cu(111) surfaces. These findings provide significant insight into crown ethers' host-guest chemistry and chiral supramolecular formation.