Room-Temperature Chemical Synthesis of C2

Diatomic carbon (C₂) is historically an elusive chemical species. It has long been believed that the generation of C₂ requires extremely high “physical” energy, such as an electric carbon arc or multiple photon excitation, and so it has been the general consensus that the inherent nature of C₂ in the ground state is experimentally inaccessible. Here, we present the first “chemical” synthesis of C₂ in a flask at room temperature or below, providing the first experimental evidence to support theoretical predictions that (1) C₂ has a singlet biradical character with a quadruple bond, thus settling a long-standing controversy between experimental and theoretical chemists, and that (2) C₂ serves as a molecular element in the formation of sp²-carbon allotropes such as graphite, carbon nanotubes and C₆₀.