The Competition of σ‑Hole···Cl– and π‑Hole···Cl– Bonds between C6F5X (X = F, Cl, Br, I) and the Chloride Anion and Its Potential Application in Separation Science

On the basis of the varying amplitude and patterns of the 19F NMR chemical shift of C6F5X (X = F, Cl, Br, I) in the presence of chloride anions, bonding models of C6F5X·Cl– complexes were tentatively established, and the relevant binding constants were obtained. Interaction models were also simulated using computational chemistry. The theoretical computations were found to be highly consistent with the results of the experiments. The results show that C6F5Br/C6F5I and Cl– were prone to forming C–I/Br···Cl– σ-hole bonding complexes with the 19F NMR signal shifting to higher fields, and the interaction strength of the C6F5I···Cl– σ-hole bond was larger than that of C6F5Br···Cl–; C6F6/C6F5Cl and Cl– formed π-hole···Cl– bonding complexes with the signal shifting to lower fields, and the interaction strength of C6F6 was larger than that of C6F5Cl. The binding constant of the C6F5I···Cl– σ-hole bonding complex is 38.0 M–1, which is nearly 165- to 345-fold larger than that of the other C6F5X·Cl– complexes. On the basis of the above results, solid phase extraction experiments were designed, and the results demonstrated the potential applicability of the C–I···Cl– σ-hole bond in separation science.