A journey into the nature of the sigma C-C single-electron chemical bond

What is it about?

A recent study reported the first experimental evidence suggesting the existence of an unusual type of carbon–carbon bond: a one-electron σ bond in a stable radical cation. Using advanced experimental techniques, including single-crystal X-ray diffraction and electron-density analysis, the authors proposed that two carbon atoms could be connected through this rare bonding interaction. However, theoretical calculations based on conventional density functional theory (DFT) provide a different interpretation: instead of a true C–C bond, they describe the system as two carbon atoms separated by a relatively large distance and interacting only weakly through a non-covalent interaction. This disagreement between experiment and theory highlights the challenges in identifying extremely weak chemical bonds, especially in systems involving radicals, where electrons can be highly delocalized.

Featured Image

Photo by Nigel Hoare on Unsplash

Photo by Nigel Hoare on Unsplash

Why is it important?

Chemical bonds are the fundamental connections that allow atoms to organize into molecules and give rise to the complexity of the natural world. From the formation of water and biological macromolecules to the structure of materials and the reactions that sustain life, understanding how and why atoms interact is central to chemistry and many other scientific disciplines. The debate surrounding this molecule may establish it as an important benchmark system for understanding the limits of chemical bonding concepts and for developing more accurate theories of weak interactions.

Perspectives