Guest-Induced Conformational Transformations in Tiara5arene Crystals: A Pathway for Molecular Sieving

In pursuit of environmental sustainability and energy efficiency, assorted macrocyclic compounds have recently emerged as crystalline adsorbents for the efficient molecular sieving of various chemical commodities. Herein, we delve into the conformational characteristics and solid-state packing modes of tiara5arenes (T5), a rim-differentiated pillar5arene derivative. By meticulously exploring the conformational space, we have successfully identified a multitude of distinct T5 conformers within a relatively narrow energy range of 22 kJ/mol. This finding underscores the inherent conformational flexibility of this macrocyclic scaffold, enabling T5 to adapt diverse packing arrangements in the solid state. While solvent-free T5 crystals do not exhibit permanent porosity, they undergo solvomorphic interconversions when exposed to various guest compounds. Our study demonstrates that T5-based crystalline materials exhibit a notable preference for selectively capturing aromatic and olefinic solvents, such as benzene, toluene, chlorobenzene, and cyclohexene, over their aliphatic hydrocarbon counterparts from equivalent volume liquid mixtures, achieving up to 10:1 selectivity between benzene and cyclohexane.