Molecular Recognition of Fluoride Anion:  Benzene-Based Tripodal Imidazolium Receptor

A benzene-based tripodal imidazolium receptor utilizing the strong (C−H)+···X- hydrogen bonding interaction between imidazolium moieties and halide anions is extensively investigated both theoretically and experimentally. Ab initio calculations predict that this receptor has a very high affinity for fluoride ion (F-). The association constant and free energy gain of the N-butyl receptor 2 for F- in acetonitrile were measured to be 2.1 × 105 M-1 and −7.25 kcal/mol, respectively, showing that the receptor has a high affinity for F- in highly polar organic solvents.