Aromatic Bridged Bis(triphenylamine) Cascade Assembly Achieved Tunable Nanosupramolecular Morphology and NIR Targeted Cell Imaging

Possessing four cationic pyridium groups, phenyl-bridged bis(triphenylamine) derivatives (G1, G2) were encapsulated by cucurbit[8]uril (CB[8]) at a 1:2 stoichiometry to form the network-like organic two-dimensional nanosheet, which could efficiently enhance the near-infrared (NIR) luminescence and companies with a red-shift from 750 to 810 nm for G1. Benefiting from the supramolecular multivalent interaction, α-cyclodextrin modified hyaluronic acid (HACD) and G1/CB[8] formed nanoparticles to further enhance NIR luminescence behaviors. Compared with the short rigid aromatic bridged bis(triphenylamine) derivative (G2), the supramolecular assembly derived from G1 with long flexible cationic arms gives a larger Stokes shift, which further coassembles with the phosphorescent bromophenylpyridinium derivative/CB[8] pseudorotaxane, leading to efficient phosphorescent resonance energy transfer (PRET). Especially, the nanoparticle showed delayed NIR fluorescence under 308 nm light excitation with an ultralarge Stokes shift up to 502 nm, which was successfully applied in targeted NIR cell imaging.