“Molecular” Molecular Sieves: Lid-Free Decamethylcucurbit[5]uril Absorbs and Desorbs Gases Selectively This work was supported in part by a Grant-in-Aid for COE Research “Design and Control of Advanced Molecular Assembly Systems” from the Ministry of Education, Science, Sports, and Culture, Japan (#08CE2005). The authors also thank Prof. T. Shinmyozu of the Institute for Fundamental Organic Chemistry in Kyushu University for use of a Rigaku RAPID X-ray instrument.

Abstract

Miniatur‐Gasauffangbehälter mit Deckel: Salzfreies Decamethylcucurbit[5]uril(MeCuc5)‐Pulver absorbiert selektiv N2, O2, Ar, N2O, NO, CO und CO2 bei Raumtemperatur, bei 110°C werden die Gase wieder desorbiert; der Vorgang lässt sich mehrfach wiederholen. Alle Edelgase von He bis Xe werden dagegen in Lösung in MeCuc5 eingeschlossen. Das Bild zeigt den Einschlusskomplex mit Xe.

Strong Binding of Hydrocarbons to Cucurbituril Probed by Fluorescent Dye Displacement: A Supramolecular Gas‐Sensing Ensemble

“…The inclusion of small hydrocarbons into molecular container compounds in solution has received considerable attention 1–9. It allows for a puristic understanding of the solvophobic driving force for the formation of discrete host–guest complexes10 and has additional potential for gas storage, uptake, and separation, thus complementing solid‐state applications of porous materials11, 12 or surface‐immobilized macrocycles 13. Studies on the precipitation of complexes between the smallest alkanes with α‐cyclodextrin date back to the 1950s 14.…”

Strong Binding of Hydrocarbons to Cucurbituril Probed by Fluorescent Dye Displacement: A Supramolecular Gas‐Sensing Ensemble

“…Gases, which were known to bind-although with unknown affinity-to CB5, [12] (CH 4 but also Ar, Kr, N 2 , and O 2 ) did not show any detectable binding with CB6. Isobutane and cyclopentane are bound strongest, with bindings constants close to 10 6 m À1 .…”

“…[1][2][3][4][5][6][7][8][9] It allows for a puristic understanding of the solvophobic driving force for the formation of discrete host-guest complexes [10] and has additional potential for gas storage, uptake, and separation, thus complementing solid-state applications of porous materials [11,12] or surface-immobilized macrocycles. [1][2][3][4][5][6][7][8][9] It allows for a puristic understanding of the solvophobic driving force for the formation of discrete host-guest complexes [10] and has additional potential for gas storage, uptake, and separation, thus complementing solid-state applications of porous materials [11,12] or surface-immobilized macrocycles.…”

“…Herein, we describe a highly sensitive fluorescence-based method for the quantification of volatile hydrocarbons binding with cucurbituril. While a CB5 derivative has been reported to bind very small guests such as methane and acetylene, [12, 19] the homologue which holds most promise for hydrocarbon binding is CB6, [20] the original cucurbituril, which possesses an intermediary size to allow inclusion of guests with up to seven heavy atoms into its inner cavity. [17,18] They are well-established to bind organic ammonium ions through a combination of hydrophobic interactions inside the nonpolar inner cavity and ion-dipole interactions with the carbonyl portals.…”

“…[17,18] They are well-established to bind organic ammonium ions through a combination of hydrophobic interactions inside the nonpolar inner cavity and ion-dipole interactions with the carbonyl portals. While a CB5 derivative has been reported to bind very small guests such as methane and acetylene, [12, 19] the homologue which holds most promise for hydrocarbon binding is CB6, [20] the original cucurbituril, which possesses an intermediary size to allow inclusion of guests with up to seven heavy atoms into its inner cavity. [18,21] Unfortunately, CB6 has an intrinsically low water solubility of about 30 mm, which complicates the determination of actual binding constants.…”