Room-Temperature Chemical Synthesis of C2

Diatomic carbon (C 2 ) is historically an elusive chemical species. It has long been believed that the generation of C 2 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 C 2 in the ground state is experimentally inaccessible. Here, we present the first “chemical” synthesis of C 2 in a flask at room temperature or below , providing the first experimental evidence to support theoretical predictions that (1) C 2 has a singlet biradical character with a quadruple bond, thus settling a long-standing controversy between experimental and theoretical chemists, and that (2) C 2 serves as a molecular element in the formation of sp 2 -carbon allotropes such as graphite, carbon nanotubes and C 60 .