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Carbon has an extremely rare form known as carbyne—a highly reactive state in which carbon exhibits unusual electronic properties. Until recently, scientists have faced significant challenges in isolating and characterizing these transient carbon species, particularly a highly variant known as carbon(I) radicals. A research team led by Dr. Tiow-Gan Ong at the Institute of Chemistry, Academia Sinica, has successfully synthesized and isolated a cationic carbon(I) radical species, [1-CDC]•+, by performing a single-electron transfer (SET) reaction between a carbodicarbene (CDC) and strongly electron-deficient 3-fluoronitrobenzene. The structure and electronic properties of [1-CDC]•+ were confirmed using electron paramagnetic resonance (EPR) spectroscopy, single crystal X-ray diffraction, and quantum chemical calculations. Reactivity studies reveal that this radical species effectively promotes various C-O and C-C cross-coupling reactions, particularly with electron-deficient aryl halides. The research findings not only expand the understanding of carbon(I) radical chemistry but also open new avenues for radical methodologies in organic synthesis and catalysis.

The research has been published on June 13, 2025, in Nature Synthesis. The research was carried out by Dr. Wen-Ching Chen and Dr. Yi-Chen Chan, as well as Ph.D. student He-Xin Xiao. The work was a collaborative effort with Professor Yun-Wei Chiang of the Department of Chemistry at National Tsing Hua University, Professor Gernot Frenking at the Philipps-Universität Marburg, Germany, and Professor Lili Zhao at the Nanjing University, China. The research was supported by Investigator Project Grant (Academia Sinica) and the Science Vanguard Research Program (National Science and Technology Council).