A doubly alkynylpyrene-threaded [4]rotaxane that exhibits strong circularly polarized luminescence from the spatially restricted excimer

The Sonogashira coupling of g -CD-encapsulated alkynylpyrenes with terphenyl-type stopper molecules gave a doubly alkynylpyrene-threaded [4]rotaxane. The rotaxane showed only excimer emission, with a high fluorescence quantum yield of Fcy f = 0.37, arising from the spatially restricted excimer within the cavity of the g-CD. The excimer emission suffered little from self-quenching up to a concentration of 1.5 × 10×5 m and was circularly polarized with a high glum value of -1.5 × 10^-2. The strong circularly polarized luminescence may result from the two stacked pyrenes existing in the rotaxane in an asymmetrically twisted manner.