Ultralarge Stokes Shift Phosphorescence Artificial Harvesting Supramolecular System with Near-Infrared Emission

A two-step sequential phosphorescence harvesting system with ultralarge Stokes shift and near-infrared (NIR) emission at 825 nm is successfully constructed by racemic 1,2-diaminocyclohexan-derived 6-bromoisoquinoline (BQ), cucurbit[8]uril (CB[8]), and amphipathic sulfonatocalix[4]arene (SC4AD) via cascaded assembly strategy in aqueous solution. In virtue of the confinement effect of CB[8] with rigid cavity, BQ can generate an emerging phosphorescent emission at 555 nm. Subsequently, the binary BQ subset of CB[8] further assemblies with SC4AD to form close-packed spherical aggregate, which contributes to the dramatic enhancement of phosphorescence emission intensity approximate to 30 times with prolonged lifetime from 21.3 mu s to 0.364 ms. Notably, the BQ subset of CB[8]@SC4AD assembly can serve as an energy donor to conduct stepwise phosphorescence harvesting process through successive introduction of primary acceptors, cyanine 5 (Cy5) or nile blue (NiB), and secondary acceptor, heptamethine cyanine (IR780). The final aggregate with remarkable ultralarge Stokes shift (approximate to 525 nm) and long-lived NIR photoluminescence (PL) emission at 825 nm is further employed as imaging agent for NIR cell labeling.

Automated summary

A two-step sequential phosphorescence harvesting system with ultralarge Stokes shift and near-infrared emission is successfully constructed using racemic 1,2-diaminocyclohexan-derived 6-bromoisoquinoline, cucurbit[8]uril, and amphipathic sulfonatocalix[4]arene via cascaded assembly strategy. The system shows significant enhancement of phosphorescence emission intensity and can be used for NIR cell labeling.