Pressure-driven, solvation-directed planar chirality switching of cyclophano-pillar[5]arenes (molecular universal joints)

• Published in: Chemical science (Cambridge) Vol. 12; no. 12; pp. 4361 - 4366
• Main Authors: Yao, Jiabin, Mizuno, Hiroaki, Xiao, Chao, Wu, Wanhua, Inoue, Yoshihisa, Yang, Cheng, Fukuhara, Gaku
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 02.02.2021; The Royal Society of Chemistry
• Subjects: Anisotropy; Aromatic compounds; Chemistry; Chirality; Hydrostatic pressure; Solvation; Solvents; Universal joints
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d0sc06988d

Planar chiral cyclophanopillar[5]arenes with a fused oligo(oxyethylene) or polymethylene subring ( MUJ s), existing as an equilibrium mixture of subring-included (in) and -excluded (out) conformers, respond to hydrostatic pressure to exhibit dynamic chiroptical property changes, leading to an unprecedented pressure-driven chirality inversion and the largest ever-reported leap of anisotropy ( g ) factor for the MUJ with a dodecamethylene subring. The pressure susceptivity of MUJ s, assessed by the change in g per unit pressure, is a critical function of the size and nature of the subring incorporated and the solvent employed. Mechanistic elucidations reveal that the in-out equilibrium, as the origin of the MUJ 's chiroptical property changes, is on a delicate balance of the competitive inclusion of subrings versus solvent molecules as well as the solvation of the excluded subring. The present results further encourage our use of pressure as a unique tool for dynamically manipulating various supramolecular devices/machines. Pressure switches the in/out conformation of cyclophano-pillararenes with accompanying inversion of the chiroptical properties.