The Power of Packing: Metallization of an Organic Semiconductor

Benzoquino-bis-1,2,3-dithiazole 5 is a closed shell, antiaromatic 16π-electron zwitterion with a small HOMO–LUMO gap. Its crystal structure consists of planar ribbon-like molecular arrays packed into offset layers to generate a “brick-wall” motif with strong 2D interlayer electronic interactions. The spread of the valence and conduction bands, coupled with the narrow HOMO–LUMO gap, affords a small band gap semiconductor with σRT = 1 × 10–3 S cm–1 and Eact = 0.14 eV for transport within the brick-wall arrays. Closure of the band gap to form an all-organic molecular metal with σRT > 101 S cm–1 can be achieved by the application of pressure to 8 GPa.