Resorcarenes: Hollow building blocks for the host-guest chemistry.

The continuous search for new qualities and the desirability of controlling the size, shape and the chemical features had led to the successful synthesis of various molecular containers and their complexes starting from resorcarene skeleton. The rigidified cavitands have been extended to capture in their round hug bigger and bigger molecules. By covalent synthesis many kinds of new hosts have been built, that maintain guests in their prison for more and more long time. Self assembly, driven by metal-ligand interaction, van der Waals forces, hydrophobicity and, mainly, hydrogen bonds, is at the base of capsules, a novel type of compounds with a peculiar inner phase, stereochemistry and reactivity. The amazing variety of hollow buildings with a resorcarene-based framework and often unique properties is reviewed.