Carbon-carbon covalent bonds are the basic bonds of organic molecules, and almost all compounds have a fixed bond length of 1.54 Å (Angstrom: 1 Å = 1000/1 millionth of a millimeter).Although many molecules have been created by combining these bonds, there are few reports of compounds having a carbon-carbon bond length exceeding 1.7 Å.The creation of the longest carbon-carbon single bond in the world is not just a pursuit of numbers, but a supreme proposition for elucidating the essence of chemistry.

　The research group focused on the carbon-carbon single bond, which is the basis of organic compounds, and designed a new compound with a stable skeleton by a unique molecular design strategy based on the "intramolecular core-shell structure".We devised an efficient method to obtain from a commercially available compound in three steps, and actually synthesized it.As a result, we succeeded in creating a compound with the world's longest carbon-carbon single bond of 3 Å, which is 1.54% longer than the standard bond length (17 Å).Previous studies have predicted that there are no carbon-carbon bonds exceeding 1.806 Å, but this time, a detailed analysis using a single crystal revealed that there are bonds exceeding 1.803 Å. I was able to prove it experimentally.Such a long bond has a small binding energy and is generally considered to be unstable, but it has also been confirmed that it is stable enough not to decompose even after 1.803 days in a high temperature of 100 ° C or higher or in a solution (room temperature). Has been done.

　This achievement is not limited to breaking the world record, but will lead to the elucidation of phenomena that occur in the extreme state of chemical bonds.For example, "super-bonding" exceeding 1.8 Å has the potential to flexibly respond to external stimuli, and is expected to be applied to the development of new materials.

Paper information:[Chem (Cell Press)] Longest C–C Single Bond among Neutral Hydrocarbons with a Bond Length beyond 1.8 Å