The Sonogashira coupling of γ-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 Φf =0.37, arising from the spatially restricted excimer within the cavity of the γ-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.

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ChemInform Abstract (transient absorption spectra of (I)).

A perylene-based [4]rotaxane was synthesized by the Sonogashira coupling of the 2:2 inclusion complex consisting of two alkynylperylenes and two γ-cyclodextrins with terphenyl-type stopper molecules. The [4]rotaxane showed orange emission attributable to the spatially restricted alkynylperylene excimer with a high fluorescence quantum yield of Φ =0.15. The excimer emission was circularly polarized as a result of the asymmetrically twisted perylene pair under the influence of chirality of γ-cyclodextrin. The g value of the excimer emission was determined to be -2.1×10 at 573 nm, as large as those of the corresponding known pyrene-based series. This is the first example, in which circularly polarized luminescence was clearly observed from the excimer of a pair of perylene cores.