Cycloparaphenylene–Helicene Conjugates with Donor–Acceptor Structure for Bioimaging

Two cycloparaphenylene-helicene conjugates with one or two [7]helicene moieties are designed and synthesized using a highly efficient cyclocondensation reaction. Configurationally stable enantiomers with P/M-configurations or P,P/M,M-configurations were isolated using high-performance liquid chromatography technique. The reported conjugates exhibit remarkable chiroptical properties and bright emission at long wavelength beyond 600 nm, as a result of the combination of cycloparaphenylene and helicene units, and the presence of a donor-acceptor structure. It is discovered that the nanoparticles prepared from one of the conjugates could be stably present in A549 cells with minimal cytotoxicity, and lysosomally colocalized for live cell imaging. This study may shed light on the application of chiral carbon nanohoops in the biological systems.