Size‐Selective and Reversible Encapsulation of Single Small Hydrocarbon Molecules by a Cavitand–Porphyrin Species

Abstract

Ein gastfreundlicher Wirt: Ein neues, kapselförmiges Wirtmolekül, das gezeigte Cavitandporphyrin, schließt reversibel einzelne Kohlenwasserstoffmoleküle kleiner als Propan ein (siehe Bild). Mit Ausnahme von Acetylen korrelieren die Bindungsaffinitäten invers mit der Größe des Gast‐Kohlenwasserstoffs.

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

“…[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.…”

“…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. [1][2][3][4][5][6][7][8][9] The binding of xenon with CB6 has been studied by 129 Xe NMR spectroscopy in the presence of 0.2 m Na 2 SO 4 , [23] where the solubility is increased (but where also the binding strength suffers). [21,22] In particular, it prevents 1 H NMR titrations, which have been routinely employed in all previous studies on solution-phase gas binding by molecular containers.…”

“…[1][2][3][4][5][6][7][8][9] The binding of xenon with CB6 has been studied by 129 Xe NMR spectroscopy in the presence of 0.2 m Na 2 SO 4 , [23] where the solubility is increased (but where also the binding strength suffers). [1][2][3][4][5][6][7][8][9] In the quest for a convenient method to monitor volatile hydrocarbon binding to CB6, we selected an indicator displacement strategy [25] based on our recently developed anchor dye approach. [24] The binding constants, which we report herein for several simple hydrocarbons, are much larger than those observed for xenon, and, in fact, the largest ones reported for neutral guests with CB6.…”

“…[21,22] In particular, it prevents 1 H NMR titrations, which have been routinely employed in all previous studies on solution-phase gas binding by molecular containers. [1][2][3][4][5][6][7][8][9] The binding of xenon with CB6 has been studied by 129 Xe NMR spectroscopy in the presence of 0.2 m Na 2 SO 4 , [23] where the solubility is increased (but where also the binding strength suffers). Alternatively, an alkylated CB6 derivative with higher water solubility has been employed, which was also investigated by isothermal titration calorimetry, to afford a binding constant of 3400 m À1 with xenon.…”

“…[24] The binding constants, which we report herein for several simple hydrocarbons, are much larger than those observed for xenon, and, in fact, the largest ones reported for neutral guests with CB6. [1][2][3][4][5][6][7][8][9] In the quest for a convenient method to monitor volatile hydrocarbon binding to CB6, we selected an indicator displacement strategy [25] based on our recently developed anchor dye approach. [1][2][3][4][5][6][7][8][9] In the quest for a convenient method to monitor volatile hydrocarbon binding to CB6, we selected an indicator displacement strategy [25] based on our recently developed anchor dye approach.…”