Synthesis of the Fluorine-Edged Macrocycle for Promoting High-Resolution Gas Chromatographic Separation

Herein, we report that the introduction of fluorine binding sites to macrocycles achieves high-resolution gas chromatographic separation of aromatic hydrocarbons, cycloolefins, and cycloparaffins. The tetrafluoroterphen[3]arene (4FTP3) macrocycle, containing 12 fluorines on its skeleton edge, was synthesized in a 52% yield via a one-pot approach and then coated onto a capillary column as a gas chromatographic stationary phase. The resulting column permitted the high-resolution separation of cyclohexane/cyclohexene/benzene, cycloheptane/cycloheptene, and tetrahydronaphthalene/naphthalene mixtures, with a retention capacity decreasing in the order of aromatic hydrocarbons > cycloolefins > cycloparaffins. Single-crystal structural analysis revealed that 4FTP3 assembled into a three-dimensional superstructure with multiple internal cavities and external voids by multiple intermolecular C–H···F interactions and contributed to the separation. Significantly, the distinction of C–H···F interactions between macrocycle 4FTP3 and analytes resulted in different binding affinities, association enthalpies, and retention times for the various analytes and therefore plays a key role in such high-resolution separation. The simple preparation, high yield, and clear separation mechanism associated with 4FTP3 render it a cost-effective separation material for use in further applications. The design of macrocycles with specific binding sites provides new insights into high-resolution gas chromatographic separation.