Crossing the Insulator-to-Metal Barrier with a Thiazyl Radical Conductor

The layered-sheet architecture of the crystal structure of the fluoro-substituted oxobenzene-bridged bisdithiazolyl radical FBBO affords a 2D π-electronic structure with a large calculated bandwidth. The material displays high electrical conductivity for a f = 1/2 system, with σ­(300 K) = 2 × 10–2 S cm–1. While the conductivity is thermally activated at ambient pressure, with Eact = 0.10 eV at 300 K, indicative of a Mott insulating state, Eact is eliminated at 3 GPa, suggesting the formation of a metallic state. The onset of metallization is supported by infrared measurements, which show closure of the Mott-Hubbard gap above 3 GPa.