Covalent bonds share electron pairs between two atoms and make up the skeletons of most organic compounds in single, double and triple bonds. In contrast, examples of one-electron bonds remain scarce, most probably due to their intrinsic weakness^1,2,3,4. Although several pioneering studies have reported one-electron bonds between heteroatoms, direct evidence for one-electron bonds between carbon atoms remains elusive. Here we report the isolation of a compound with a one-electron σ-bond between carbon atoms by means of the one-electron oxidation of a hydrocarbon with an elongated C–C single bond^5,6. The presence of the C•C one-electron σ-bond (2.921(3) Å at 100 K) was confirmed experimentally by single-crystal X-ray diffraction analysis and Raman spectroscopy, and theoretically by density functional theory calculations. The results of this paper unequivocally demonstrate the existence of a C•C one-electron σ-bond, which was postulated nearly a century ago⁷, and can thus be expected to pave the way for further development in different areas of chemistry by probing the boundary between bonded and non-bonded states.

共价键在两个原子之间共享电子对，并以单键、双键和三键构成大多数有机化合物的骨架。相比之下，单电子键的例子仍然很少，很可能是因为它们的固有弱点^1,2,3,4。尽管几项开创性研究已经报道了杂原子之间的单电子键，但碳原子之间存在单电子键的直接证据仍然难以捉摸。在这里，我们报道了通过对具有拉长 C-C 单键的碳氢化合物进行单电子氧化来分离碳原子之间具有单电子 σ 键的化合物^5,6。C•C 单电子σ键（100 K 时为 2.921（3） Å）的存在通过单晶 X 射线衍射分析和拉曼光谱得到实验证实，理论上通过密度泛函理论计算得到证实。本文的结果明确证明了 C•C 单电子σ键的存在，这是近一个世纪前假设的⁷，因此可以预期通过探测键合态和非键合态之间的边界，为化学不同领域的进一步发展铺平道路。