Symmetrically Tetra‐functionalized Pillar[6]arenes Prepared by Fragment Coupling.

Due to the highly symmetrical structures generated from one‐pot syntheses, the partial functionalization of macrocycles is usually beset with low yields and onerous purifications of the target multifunctional macrocycles. To improve this situation, taking pillar[6]arenes as an example, a two‐step fragment coupling method has been developed for synthesizing symmetrically tetra‐functionalized pillar[6]arenes, namely X‐pillar[6]arenes. This method is simple and versatile, which makes hetero‐fragment coupling and pre‐functionalization available. Nine new macrocycles and a pillar[6]arene‐based cage have been prepared. In addition, one of the newly synthesized macrocycles, COOEtEtXP[6], exhibits a strong cyan luminescence in the solid state under irradiation by 365 nm UV light. This emission originates from intramolecular through‐space conjugation. Meanwhile, formation of a supramolecular polymer by multiple non‐covalent intra/intermolecular interactions helps rigidify the structure and make COOEtEtXP[6] an efficient solid‐state emitter. It is believed that this fragment coupling can also be used to realize the multi‐functionalization of other macrocycles. [ABSTRACT FROM AUTHOR]