Gwyneth Perseveranda

The quest for knowledge takes time and this discovery is a testament of it.


Chemists from Hokkaido University, or Hokudai, have identified the existence of a single electron in a carbon-carbon compound.

Covalent bonds, characterized by the sharing of electrons between two atoms, are the building blocks of the majority of organic compounds such as proteins and carbohydrates.

Current understanding suggests that the existence of covalent bonds emerging from a single, unpaired electron is possible; however, these single-electron bonds would likely be much weaker in comparison to a standard covalent bond, which are formed by a pair of electrons.

This unusual bonding behavior has been observed between a few other atoms such as phosphorus, copper, and boron, but never in carbon or hydrogen.

Since then, the search for one-electron bonds in carbon has consistently posed a challenge to scientists.

“The nature of single-electron bonds between two carbon atoms is essential to gain a deeper understanding of chemical bonding theories and would provide further insights into chemical reactions,” Yusuke Ishigaki of the Department of Chemistry at Hokudai said.

Ishigaki’s team then crystallized the compound to capture it in a stable and observable form. 

Then, they oxidized a derivative of hexaphenylethane, a material particularly used in molecular structures and photochemistry, composed of a stretched paired-electron bond between two carbon atoms, through iodine, which resulted in the formation of dark violet crystals of salt.

The team used X-ray diffraction analysis to study the cystals and found that the carbon atoms were extremely close together, indicating single-electron covalent bonds.

The identified single-electron covalent bonds were confirmed through the use of Raman spectroscopy.

“These results thus constitute the first piece of experimental evidence for a carbon-carbon single-electron covalent bond, which can be expected to pave the way for further developments of the chemistry of this scarcely-explored type of bonding,” Takuya Shimajiri, lead author of the paper said.

He also hopes that the existence of single-electron bonds will aid chemists in better understanding of the basic nature of chemical bonds.

“We aim to clarify what a covalent bond is—specifically, at what point does a bond qualify as covalent, and at what point does it not,” Shimajiri said.