Preferential binding of unsaturated hydrocarbons in aryl-bisimidazolium·cucurbit[8]uril complexes furbishes evidence for small-molecule π–π interactions. Issue 44 (17th October 2019)

• Record Type: Journal Article
• Authors: Barrow, Steven J.; Assaf, Khaleel I.; Palma, Aniello; Nau, Werner M.; Scherman, Oren A.
• Is Part Of: Chemical science. Volume 10:Issue 44(2019)
• Page Start: 10240
• Page End: 10246
• Publication Date: 2019-10-17
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c9sc03282g
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Restricting the internal cavity size of cucurbit[8]uril with auxiliary guests sets up an intermolecular interaction chamber for hydrocarbons, which provides insights into dispersion, arene–hydrocarbon interactions, and desolvation effects. Abstract : Whilst cucurbit[ n ]urils (CB n ) have been utilized in gas encapsulation, only the smaller CB n ( n = 5 and 6) have utility given their small cavity size. In this work, we demonstrate that the large cavity of CB8 can be tailored for gaseous and volatile hydrocarbon encapsulation by restricting its internal cavity size with auxiliary aryl-bisimidazolium (Bis, aryl = phenyl, naphthyl, and biphenyl) guests. The binding constants for light hydrocarbons (C ≤ 4) are similar to those measured with CB6, while larger values are obtained with Bis·CB8 for larger guests. A clear propensity for higher affinities of alkenes relative to alkanes is observed, most pronounced with the largest delocalized naphthalene residue in the auxiliary Bis guest, which provides unique evidence for sizable small-molecule π–π interactions.