The Power of Packing: Metallization of an Organic Semiconductor

Benzoquino-bis-1,2,3-dithiazole <b>5</b> 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 σ<sub>RT</sub> = 1 × 10<sup>–3</sup> S cm<sup>–1</sup> and <i>E</i><sub>act</sub> = 0.14 eV for transport within the brick-wall arrays. Closure of the band gap to form an all-organic molecular metal with σ<sub>RT</sub> > 10<sup>1</sup> S cm<sup>–1</sup> can be achieved by the application of pressure to 8 GPa.