The design and optimization of fluorescent molecules has driven the ability to interrogate complex biological events in real time. Notably, most advances in bioimaging fluorophores are based on optimization of core structures that have been known for over a century. Recently, new synthetic methods have resulted in an explosion of nonplanar conjugated macrocyclic molecules with unique optical properties yet to be harnessed in a biological context. Herein we report the synthesis of the first aqueous-soluble carbon nanohoop (i.e., a macrocyclic slice of a carbon nanotube prepared via organic synthesis) and demonstrate its bioimaging capabilities in live cells. Moreover, we illustrate that these scaffolds can be easily modified by well-established “click” chemistry to enable targeted live cell imaging. This work establishes the nanohoops as an exciting new class of macrocyclic fluorophores poised for further development as novel bioimaging tools.

Upon exposure to Scholl reaction conditions, cycloparaphenylenes undergo facile strain-relieving rearrangements and ring-openings.

The unique optoelectronic properties and smooth, rigid pores of macrocycles with radially oriented p systems render them fascinating candidates for the design of novel mechanically interlocked molecules with new properties.T wo high-yielding strategies are used to prepare nanohoop [2]rotaxanes,which owing to the p-rich macrocycle are highly emissive. Then, metal coordination, an intrinsic property afforded by the resulting mechanical bond, can lead to molecular shuttling as well as modulate the observed fluorescence in both organic and aqueous conditions.Inspired by these findings,aself-immolative [2]rotaxane was then designed that self-destructs in the presence of an analyte,e liciting as trong fluorescent turn-on response,s erving as proof-of-concept for an ew type of molecular sensing material. More broadly,this work highlights the conceptual advantages of combining compact p-rich macrocyclic frameworks with mechanical bonds formed via active-template syntheses.