"Nanocarbon", a carbon substance with nanometer-sized periodicity such as graphene and carbon nanotubes, is expected as a lightweight and highly functional next-generation material.

　However, the molecules (molecular nanocarbons) that form the partial structure of nanocarbons have been successfully synthesized so far only with relatively simple structures, and they have complicated geometric structures (topologies) such as knots and entanglements. We have not yet synthesized the "topological molecular nanocarbon".

　In this study, we succeeded in synthesizing the carbon knot "all benzene knot" and the carbon knot "all benzene catenane" for the first time in the world by a new method using a silicon atom.In the conventional method, a topological structure was derived using nitrogen atoms and oxygen atoms as a foothold, but in the synthesis strategy of this study, silicon atoms that can be removed later by fluorine treatment were used for "temporary fastening".As a result, a topological molecular nanocarbon consisting only of a carbon skeleton was finally obtained.

　The research group continued to confirm the structures of all-benzene knots and all-benzene catenane that were successfully synthesized by X-ray crystallography, and also revealed that they have peculiar optical properties and dynamic behavior derived from knots and entanglements. I made it.These properties are extremely difficult to discover unless they can be synthesized and isolated.

　This achievement can be said to be an epoch-making achievement that paves the way for the design and synthesis of unexplored nanocarbons with complex topologies predicted by theoretical chemistry.

Paper information:[Science] Topological molecular nanocarbons: all-benzene catenane and trefoil knot