Hydrogen bond hexameric capsules: Structures, host-guest interactions, guest affinities, and catalysis

Abstract

Resorcin[4]arenes (6) and pyrogallol[4]arenes (7) are concave molecules which were found to form large hexameric capsules in the solid state and in solution in the presence of specific guests. There after diffusion NMR have shown that 6, 7 and even octahydroxypyridine[4]arenes (8) form, spontaneously, hexameric capsules in organic solvents thus demonstrating that hexameric capsules are much more abundant than previously thought. In the following chapter after a brief introduction we describe the supramolecular structures of the hexamers of 6, 7 and 8. Then self-sorting and the guests affinity in the hexameric capsules of 6 and 7 are described after which the peculiar NMR spectra of encapsulated solvent molecules in the hexamers of 7 are describe in details. One of the main characteristics of molecular capsule it the ability of such system to isolate the guest from the bulk. Such systems can be regarded as nano-reactors where new chemistry and catalysis can emerge. Here we describe the recent example in which the hexameric capsules of 6 were used as nano-reactors and catalytic vessels. We end our essay by a short description of the recent developments in the field of metal organic nano-capsules (MONCs).