Highly Emissive Phenylene-Expanded [5]Radialene

A pentagonal macrocycle (MC5-PER) with radialene topology was facilely synthesized through the selective one-pot Suzuki-Miyaura cross-coupling reaction. The resulting product endows the pentagonal architecture as revealed by its single crystal structure, and affords the smallest ring strain and the best conjugation. As tetraphenylethene subunits are embedded, MC5-PER is highly emissive in solid state due to the aggregation-induced emission effect. Because of flexible structure and preferable fibre-like self-assemble, aggregate of MC5-PER displays interesting polymorphism-dependent emission and acts as a sensitive fluorescent sensor for explosive detection.