Recent advances in the supramolecular assembly of cyclophosphazene derivatives

Cyclophosphazenes are a fascinating group of inorganic heterocyclic compounds whose rings are constituted by the repetition of phosphorus and nitrogen atoms. They have received particular attention due to their easy functionalization and thermal stability and as an excellent core for the preparation of advanced materials. Rigid trispirocyclic derivatives of cyclophosphazenes afford numerous supramolecular structures that are suitable for the formation of host-guest complexes with a variety of guest molecules such as gas molecules and molecular rotor compounds. Also, the donor nitrogen atoms of the cyclophosphazene ring can participate in non-covalent interactions such as hydrogen bonding and metal coordination. It can also be used in the construction of supramolecular dendrimeric or polymeric systems as either the starting compound or the carrier of supramolecular groups. Thus, cyclophosphazenes have been employed in the preparation of supramolecular systems for about past 30 years. This review focuses on the state of recent advances in the construction of cyclotriphosphazene-based supramolecular systems built by non-covalent interactions and their applications such as host-guest complexes, liquid crystals, coordination polymers and nanostructures. The future perspective of cyclophosphazene supramolecular assemblies is also discussed.