Belt-shaped cyclonaphthylenes

The recent development of cyclo-para-phenylenes has demonstrated the feasibility of radial π systems in nanohoop structures, especially in the crystalline state. However, in contrast to macrocyclic molecules with benzene units, which have a several-decades-long history, macrocycles composed solely of naphthylene units (the smallest acene) have been much less explored. Although two examples of cyclonaphthylenes have been reported to date, neither possesses a radial π system. We herein report the first example of belt-shaped cyclonaphthylenes with curved π systems. The molecule, [8]cyclo-amphi-naphthylene, is linked at the 2,6-positions of the naphthylene units, thus affording belt-shaped molecules. Although the molecular structures are flexible, which allows for rotation of the naphthylene units in solution, they can be rigidified with the aid of methylene bridges to afford persistent molecular structures in solution. Being persistent: Cyclonaphthylene nanohoops have been synthesized and characterized in solution and in the solid state. The naphthylene units in [8]cyclo-amphi-naphthylene, prepared by linking naphthylene units at the 2,6-positions, can undergo rotation, but rigidification with the aid of methylene bridges affords persistent molecular structures in solution.