High-yield syntheses of doubly 2,7-dialkynylpyrene-threaded photostable 8rotaxanes exhibiting extremely bright circularly polarized luminescence.

Circularly polarized luminescence (CPL) emitters garner much interest due to their potential applications in chiroptical materials. While many organic CPL emitters have been reported, their preparation often requires low-yield reactions and laborious optical resolution steps. In this study, we demonstrated a cooperative rotaxane approach to synthesize CPL emitters with desirable properties in high yields. We designed doubly 2,7-dialkynylpyrene-threaded 8rotaxanes with two γ-cyclodextrins and four cucurbit6urils as ring components. Although these 8rotaxanes have heavily complicated interlocked structures, their syntheses were achieved in 67-77% isolated yields as a single isomer utilizing a cooperative capture strategy. These 8rotaxanes exhibited high luminescence quantum yields Φ lum of 0.40-0.47 and large |g lum| values of 1.1-1.9 × 10-2 in an aqueous solution. Considering ε = 2.2-2.5 × 105 M-1 cm-1, the CPL brightness (B CPL = ε × Φ lum × |g lum|/2) values of 569-836 were as bright as the highest ones of reported organic CPL emitters. Owing to the insulation of the alkynylpyrene cores against outside molecules by the ring components, the 8rotaxanes showed outstanding photo- and thermal-stability in solutions. The 8rotaxanes might have the potential to be CPL emitters suitable for future optical materials.