Guest loading, chromatographic purification and controlled release from kinetically trapped, hydrogen-bonded pyrogallol[4]arene capsules

Encapsulated or Not Encapsulated? Ammonium Salts Can Be Encapsulated in Hexameric Capsules of Pyrogallol[4]arene

“…On the basis of these observations and on the fact that the hexamer of 1b is formed without the aid of water molecules, the Purse group speculated that a solvent-free method, the melting approach, should enable one to increase the repertoire of guests that can be encapsulated in the hexameric capsules of 1b . Indeed, it was found that many guests that could not be encapsulated when chloroform was used as a solvent were encapsulated in the hexameric capsule of 1b when the melting method was used . In these recent studies, it was found that tetraalkylammonium salts (R 4 N + X – ) are not encapsulated in the hexamers of 1b .…”

On the mechanism of mechanochemical molecular encapsulation in peptidic capsules

“…21 An exception in this regard is a tightly sealed pyrogallolarene hexameric capsule that is surprisingly kinetically stable in non-polar solvents and encapsulation can be achieved by neat-melting with guests. [22][23][24] We recently reported a hydrogen bonded peptidic capsule that is kinetically stable in non-polar solvents ( Fig. 1 and 2).…”

2H NMR reveals liquid state-like dynamics of arene guests inside hexameric pyrogallol[4]arene capsules in the solid state

“…Guest exchange for solvent occurs over time, but often with ΔG ‡ > 23 kcal/mol and an imperceptibly slow rate at ambient temperature. 22,28 Guests encapsulated in these hexamers are generally dynamic in the capsules' interiors on the 1 H NMR timescale, although Cohen has shown evidence for distinct guest sites tied to attractive interactions between guests and the host's alcohol groups. 19,23,29 Solid-state 13 C NMR has been used by Cohen et al to identify guest encapsulation in pyrogallol [4]arene hexamers in the solid state, and our lab has applied this method to the study of solid-state, mechanically induced hexamer assembly with guest inclusion by ball milling, extending the scope of molecular encapsulation.…”