To effectively relate structure and function, nanocarbon scientists must first obtain structurally uniform nanocarbons—ideally as single molecules. The fabrication of functional materials in nanotechnology, optics, electronics, and biomedical applications requires the construction of structurally uniform nanocarbons.
Molecular nanocarbon science, a bottom-up approach to generating nanocarbons using synthetic organic chemistry, is an essential tool to achieve this goal. However, the molecular nanocarbons synthesized so far have simple structures such as a ring, a shell, or a belt.
It is necessary to develop new methods to synthesize molecular nanocarbons with more complex structures to realize unexplored and theoretically predicted nanocarbons.
A group of researchers led by Kenichiro Itami (Professor, Nagoya University), Yasutomo Segawa (Associate Professor, Institute for Molecular Science) and Yuh Hijikata (Specially Appointed Associate Professor, ICReDD) have now synthesized a belt-shaped molecular nanocarbon with a twisted Möbius band topology, i.e. a Möbius carbon nanobelt.
The Möbius carbon nanobelt was a dream molecule in the scientific community after we reported the first chemical synthesis of a carbon nanobelt—an ultrashort carbon nanotube—in 2017. Molecular Belt’ when tightened with a twist. It’s another amazingly beautiful molecule.
Kenichiro Itami, Professor, Nagoya University
The properties and molecular motions of a twisted Möbius carbon nanobelt should differ significantly from those of a normal belt topology. Creating that twist, however, is easier said than done.
We knew from our previous synthesis of carbon nanoribbons that the strain energy is the main hurdle in the synthesis. Furthermore, the additional twist within the belt structure makes the strain energy of the final target molecule even higher. The key to success in the actual synthesis was our molecular design and detailed study of the reaction conditions.
Yasutomo Segawa, Associate Professor, Institute of Molecular Science
Yasutomo Segawa is co-leader of the project.
The rational synthetic route was discovered through a theoretical analysis of the enormous strain arising from the belt shape and twisted molecular structure of the Möbius carbon nanobelt. A newly developed functionalization reaction, a Z-selective Wittig reaction sequence, and a strain-inducing nickel-mediated homocoupling reaction were used to fabricate the Möbius carbon nanobelt.
The twist unit of the Möbius band moves rapidly around the Möbius carbon nanobelt molecule in solution, according to spectroscopic analysis and molecular dynamics simulation. Using chiral separation and circular dichroism spectroscopy, the topological chirality resulting from the Möbius structure was confirmed experimentally.
New forms of carbon and nanocarbons have continually opened doors to new science and technology, leading to the discovery of extraordinary (and often unpredictable) properties, functions, and uses throughout history.
The current work is a breakthrough achievement that lays the foundation for the development of nanocarbon materials with complex topological structures, as well as for the emergence of novel materials science based on Möbius topology.
Segawa, Y. et al. (2022) Synthesis of a Möbius carbon nanobelt. natural synthesis. doi.org/10.1038/s44160-022-00075-8.