Scientists confirm stable single-electron bond in carbon compound

Scientists confirm stable single-electron bond in carbon compound
by Riko Seibo
Tokyo, Japan (SPX) Sep 26, 2024

A groundbreaking discovery by researchers at Hokkaido University has validated a century-old theory, confirming the existence of a stable single-electron covalent bond between two carbon atoms. This finding marks a significant step forward in understanding chemical bonding, as the existence of such a bond has long been speculated but never before observed in carbon-based compounds.

In a typical covalent bond, two atoms share a pair of electrons, providing the foundation for most organic compounds. However, in 1931, Nobel laureate Linus Pauling proposed that a weaker type of covalent bond, involving a single unpaired electron, could also exist. Despite some observations of single-electron bonds, one shared between carbon atoms had remained elusive.

The Hokkaido University team isolated a compound where a single electron forms a remarkably stable sigma bond between two carbon atoms. The researchers' work, recently published in 'Nature', demonstrates the first direct evidence of such a bond.

"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," explained Professor Yusuke Ishigaki from Hokkaido University's Department of Chemistry, one of the study's co-authors.

The team created the bond by oxidizing a derivative of hexaphenylethane, a compound known to have a highly stretched paired-electron covalent bond between carbon atoms, in the presence of iodine. This reaction produced dark violet-colored crystals of an iodine salt.

Using X-ray diffraction analysis, the researchers observed that the carbon atoms in the crystals were extremely close together, indicating the presence of single-electron bonds. Raman spectroscopy further confirmed their findings.

"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," said Takuya Shimajiri, the lead author of the paper and now affiliated with the University of Tokyo.

Research Report:Direct evidence for a carbon - carbon one-electron s-bond