Internal Cavity versus External Cavity: A Theoretical Study of Molecular Recognition of Biphenarene.

Crystalline macrocyclic materials hold great promise for the efficient separation of compounds with similar structures and properties via selective molecular recognition. Notably, the crystal packing of the macrocycles creates new intermolecular external cavities capable of accommodating guest molecules in a manner distinct from molecular recognition in solution, thereby exhibiting different adsorption properties. This work focuses on the guest recognition mechanisms of MeBP3, a new type of macrocyclic arene, in a crystal environment. Density functional theory (DFT) calculations and wavefunction analyses are performed to elucidate the preferential encapsulation of CH3CN within the internal cavity of MeBP3. In contrast, cis-1,2-dichloroethene exhibits preferential encapsulation within the external cavity of MeBP3. This study provides insights into the selective molecular recognition of biphenarenes, particularly in solid-state environments, which is crucial for advancing the design and application of macrocyclic arenes in selective adsorption and separation.