Host-Guest Recognition and Fluorescence of a Tetraphenylethene-Based Octacationic Cage

We report the synthesis and characterization of a three-dimensional tetraphenylethene-based octacationic cage that shows host-guest recognition of polycyclic aromatic hydrocarbons (e.g. coronene) in organic media and water-soluble dyes (e.g. sulforhodamine 101) in aqueous media through CH⋅⋅⋅π, π-π, and/or electrostatic interactions. The cage⊃coronene exhibits a cuboid internal cavity with a size of approximately 17.2×11.0×6.96 Å and a "hamburger"-type host-guest complex, which is hierarchically stacked into 1D nanotubes and a 3D supramolecular framework. The free cage possesses a similar cavity in the crystalline state. Furthermore, a host-guest complex formed between the octacationic cage and sulforhodamine 101 had a higher absolute quantum yield (Φ =28.5 %), larger excitation-emission gap (Δλ =211 nm), and longer emission lifetime (τ=7.0 ns) as compared to the guest (Φ =10.5 %; Δλ =11 nm; τ=4.9 ns), and purer emission (Δλ =38 nm) as compared to the host (Δλ =111 nm).