Halogen anion (Cl−, Br−) and alkali metal cation (Cs+, K+, Rb+) synergistic binding behaviors using a belt shaped dual-functional hydrocarbon receptor

The belt shaped functionalized hydrocarbon receptors have attracted great interest because of their special "frustum-like" configuration, in which the openings at the upper and lower ends (dual-functional sites) are more beneficial when used as ion recognition sites. In this paper, the binding behaviors of the belt shaped dual-functional hydrocarbon receptors for halogen anions (Cl- and Br-) and alkali metal cations (K+, Rb+, and Cs+) were investigated in depth using density functional theory calculations. It is found that anion/cation binding can be enhanced and synergistically regulated by counterion and the corresponding conformational changes of the receptor, which well reflects the electrical complementary matching and mutual reinforcement effects. The nature of the receptor-ion interactions was further elucidated by combining the noncovalent intermolecular interaction with molecular electrostatic potential analysis. The complexation process of Cs+/Cl- with the receptor was dynamically tracked using ab initio molecular dynamics simulation.