Room-temperature chemical synthesis of C(2)

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 chemical synthesis of C(2) from a hypervalent alkynyl-λ(3)-iodane in a flask at room temperature or below, providing experimental evidence to support theoretical predictions that C(2) has a singlet biradical character with a quadruple bond, thus settling a long-standing controversy between experimental and theoretical chemists, and that C(2) serves as a molecular element in the bottom-up chemical synthesis of nanocarbons such as graphite, carbon nanotubes, and C(60).