Resonating valence-bond ground state in a phenalenyl-based neutral radical conductor

An organic material composed of neutral free radicals based on the spirobiphenalenyl system exhibits a room temperature conductivity of 0.3 siemens per centimeter and a high-symmetry crystal structure. It displays the temperature-independent Pauli pararnagnetism characteristic of a metal with a magnetic susceptibility that implies a density of states at the Fermi level of 15.5 states per electron volt per mole. Extended Huckel calculations indicate that the solid is a three-dimensional organic metal with a band width of ~0.5 electron volts. However, the compound shows activated conductivity (activation energy, 0.054 electron volts) and an optical energy gap of 0.34 electron volts. We argue that these apparently contradictory properties are best resolved in terms of the resonating valence-bond ground state originally suggested by Pauling, but with the modifications introduced by Anderson.
The familiar properties of inorganic metals, such as the inverse temperature dependence of their conductivity, are well understood in terms of band theory, in which valence electrons populate delocalized states [...]