Direct evidence for a carbon-carbon one-electron σ-bond

Area of Science:

• Organic Chemistry
• Physical Chemistry
• Chemical Bonding Theory

Background:

• Covalent bonds (single, double, triple) form the basis of organic chemistry.
• One-electron bonds are rare and poorly understood, with limited evidence, especially between carbon atoms.

Purpose of the Study:

• To provide direct experimental and theoretical evidence for the existence of a one-electron sigma bond between carbon atoms (C•C).
• To investigate the properties and stability of such a bond.

Main Methods:

• One-electron oxidation of a hydrocarbon with a pre-existing elongated C-C single bond.
• Experimental confirmation using single-crystal X-ray diffraction and Raman spectroscopy.
• Theoretical validation through density functional theory (DFT) calculations.

Main Results:

• Isolation and characterization of a compound featuring a C•C one-electron sigma bond.
• Experimental bond length determined as 2.921(3) Å at 100 K.
• DFT calculations corroborated the existence and nature of the C•C one-electron sigma bond.

Conclusions:

• Unequivocal demonstration of the C•C one-electron sigma bond, a concept postulated nearly a century ago.
• This finding expands the understanding of chemical bonding, bridging the gap between bonded and non-bonded states.
• Potential to inspire new developments in organic chemistry and materials science.