Superphanes: Facile and efficient preparation, functionalization and unique properties

Abstract

Superphanes, compounds in which the two benzene rings clamped parallel on top of each other by six bridges, have been attracting considerable interest because of their structural beauty and symmetry. However, progress in the research of superphane chemistry and beyond has been seriously hampered by their poor availability. Herein, we report the facile and scalable synthesis of a collection of superphanes with structural diversity and their unique photophysical properties, as well as their unusual host–guest behavior. A set of secondary amine–linked superphanes are obtained via dynamic self–assembly of a hexakis–amine and various readily derived aromatic dialdehyde in one pot, followed by in–situ reduction with NaBH4. Further post–functionalization was exemplified by secondary amine to tertiary amine conversion. All superphanes under study were found to exhibit interesting fluorescence either in solution or in the solid state. Finally, the unusual host–guest binding properties was exemplified by the stabilization of a labile 2Cl–·H2O cluster with fully protonated 6a both in solution and in the solid state. With the easy and versatile synthesis, modification, as well as unique photophysical and host–guest properties reported herein, we believe that this study offers new possibilities for superphane chemistry, supramolecular host design, advanced functional materials and beyond.

Keywords

• Cyclophanes
• Superphanes
• Self–assembly
• Dynamic covalent bond
• Fluorescence emission
• Host–guest