Self-assembled dimeric containers based on calix[4]arene, resorcin[4]arene and calix[4]pyrrole scaffolds

Abstract

The understanding of the basic principles controlling reversible encapsulation processes is a key point for the development of valuable applications of synthetic molecular containers. Over the last decades, supramolecular chemists have prepared different molecular scaffolds able to self-assemble through non-covalent interactions to form hollow dimeric capsular assemblies. Calix[4]arenes, resorcin[4]arenes and aryl-extended calix[4]pyrroles are privileged candidates for the self-assembly of molecular containers. They can be locked in bowl-shaped conformations featuring deep aromatic cavities ideal for the inclusion of suitable guests. The binding properties of reversible molecular containers depend on the molecular building blocks used in their assembly. While calix[4]arenes typically encapsulate non-polar aliphatic, aromatic, neutral and positively charged guests through van de Waals, CH-π and/or π-π interactions, calix[4]pyrrole based capsules bind electron-rich neutral or anionic guests mainly through hydrogen bonding interactions with the NHs of the calixpyrrole core. Different non-covalent interactions have been used to induce the assembly of molecular containers: hydrogen bonds, metal/ligand coordination bonds, halogen bonds and diverse combinations of some of them. The type of interaction/s used to hold together the components of the container highly affected their properties and applications. The present chapter tries to provide the reader with a general overview of self-assembled dimeric containers derived from calix[4]arenes, resorcin[4]arenes and aryl-extended calix[4]pyrroles and it also highlights some interesting properties of the resulting encapsulation complexes.