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

Abstract

An accommodating host: A new capsule‐shaped host molecule, the cavitand–porphyrin shown, reversibly encapsulates single hydrocarbon molecules smaller than propane (see picture). With the exception of acetylene, the binding affinities are inversely correlated with the size of the guest hydrocarbons.

A Cavity‐Tailored Metal‐Organic Cage Entraps Gases Selectively in Solution and the Amorphous Solid State

“…[8] Soluble containers bind gases in different ways than do framework materials. [9] The use of purely organic capsules [10] for gas binding has been well explored, [11] whereas gas encapsulation within discrete metal-organic cages [12] has been observed in a much more limited set of cases. [13] A water-soluble Fe II 4 L 6 coordination cage was found to encapsulate SF 6 or Xe in water via the hydrophobic effect.…”

“…Surrounding the inner cavity with ethyl chains results in a lipophilic confined volume of 86 Å 3 , calculated using VOIDOO [18] . We envisaged this space to be suitable for the binding of small hydrocarbon gases via van der Waals interactions [11b,e] . Note that if 12 methylene groups were to be subtracted from or added into the cavity, the resulting cages bearing methyl or propyl substituents might be too large to bind gaseous guests or too crowded to form in solution.…”

Supramolecular fluorescence sensor for liquefied petroleum gas

“…This supramolecular sensor works at room temperature, while many semiconductor gas sensors require high temperature of 200-500°C, indicating that the supramolecular sensor operates with lower power consumption. Molecular hosts that can bind gas molecules [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] have been developed so far. A main difference between the nanocube and other molecular hosts is that the nanocube finely responds to the guest molecules and outputs a strong fluorescence signal.…”

“…As LPG is liquefied under pressure of ca. 1 MPa at room temperature, which is much lower than the required pressure for compressed natural gas (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32), LPG has a great advantage in terms of transportation compared with other fuel gases 1 . However, its low explosive limit (~0.2 vol%) has often caused accidents and harm 2 .…”

Microwave-assisted synthesis of a new series of resorcin[4]arene cavitand-capped porphyrin capsules

“…29, 30 The use of two short, adjacent ether bridges (two atoms in length), in the construction of a 'pac-man' kind of ligand, 31 allows the reversible encapsulation of various hydrocarbons with noteworthy guest exchange rates. 15,29,30 Classical hemicarcerands, as pioneered by Cram and coworkers, are well documented as receptors to a vast range and number of guest molecules. [32][33][34][35] Fundamentally, complexation investigations of the reported hosts indicated that the shape and size of the portals governing access to the molecular cavity were of particular importance in the binding abilities of the receptor molecule.…”