A team of researchers at Hokkaido University and the University of Tokyo has made a groundbreaking discovery, confirming a century-old theory proposed by Nobel Laureate Linus Pauling. They have successfully isolated a compound containing a stable single-electron covalent bond between two carbon atoms, a feat that has eluded scientists for decades. This remarkable achievement marks a significant leap in our understanding of chemical bonding.
Covalent bonds, where two atoms share a pair of electrons, form the foundation of most organic compounds. In 1931, Pauling theorized that covalent bonds formed by just a single, unpaired electron could exist, but these single-electron bonds would be significantly weaker than standard paired-electron bonds. While single-electron bonds have been observed in other elements, their existence in carbon or hydrogen, the building blocks of life, has remained elusive.
The Hokkaido University research team focused on a derivative of hexaphenylethane, a compound containing a stretched out paired-electron covalent bond between two carbon atoms. By subjecting this compound to an oxidation reaction in the presence of iodine, they produced dark violet crystals of an iodine salt. Through X-ray diffraction analysis, the researchers observed that the carbon atoms in these crystals were unusually close together, hinting at the presence of single-electron covalent bonds. This hypothesis was further confirmed using Raman spectroscopy.
The discovery of a stable single-electron bond between two carbon atoms is a significant breakthrough. It validates Pauling’s theory and offers a deeper understanding of chemical bonding mechanisms. This finding holds immense potential for advancing our knowledge of chemical reactions and opens new avenues for exploring the chemistry of this previously unexplored type of bonding.
“Elucidating the nature of single-electron sigma-bonds between two carbon atoms is essential to gain a deeper understanding of chemical-bonding theories and would provide further insights into chemical reactions,” explains Professor Yusuke Ishigaki of Hokkaido University, a co-author of the study. The lead author, Takuya Shimajiri, now at the University of Tokyo, states that “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.”
This groundbreaking research, published in the journal Nature, is funded by various organizations including the Masason Foundation, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), the Japan Society for the Promotion of Science (JSPS), and the Japan Science and Technology Agency (JST). The discovery of a single-electron bond in a carbon-based compound marks a significant milestone in the field of chemistry and promises to unlock exciting new possibilities for the future.
