Rhodium-Catalyzed Intermolecular Cycloaromatization Route to Cycloparaphenylenes that Exhibit Aggregation-Induced Emission.

Abstract

A high-yielding new route to substituted cycloparaphenylenes has been developed via reductive aromatization of a diyne bearing two cyclohexadiene units giving a cyclophenylene-ethynylene (CPE) followed by the cationic rhodium(I)/dppe complex-catalyzed intermolecular [2+2+2] cycloaddition (cycloaromatization) of the CPE with monoynes. The thus-obtained products, substituted [8]cycloparaphenylene-triphenylenes ([8]CPPTs), exhibited definite aggregation-induced emission (AIE). This molecule is noteworthy as a novel AIE-active cycloarylene that does not have well-known AIE luminogens, such as tetraphenylethene and 1,2,4,5-tetraphenylbenzene skeletons. The single-crystal X-ray diffraction analyses of the AIE-active [8]CPPTs revealed their highly ordered packing structures in which the rotation of the triphenylene moieties is restricted.