Wikipedia
Cyclobis(paraquat-p-phenylene)
Cyclobis(paraquat-p-phenylene) (formally a derivative of paraquat) belongs to the class of cyclophanes, and consists of aromatic units bridged by methylene bridges. It is able to incorporate small guest molecule and has played an important role in host-guest chemistry and supramolecular chemistry.
The cyclophane is also referred to as Stoddart's blue box because its inventor, J. Fraser Stoddart, illustrates the electron-poor areas of molecules in a blue shade.