New Organic Superconductors Consisting of an Unprecedented π-Electron Donor

The synthesis and electrochemical properties of a new organic donor, (1,4-dioxan-2,3-diyldithio)dihydrotetrathiafulvalene (DODHT), and the crystal structures and physical properties of its superconducting salts are described. The DODHT molecule has the bulky dioxane ring condensed by cis fusion, and the reduced π-electron system of DODHT, as compared with conventional tetrachalcogenafulvalene donors, leads to both the weak electron-donating ability and the large on-site Coulomb energy. Nevertheless, DODHT produces the superconducting AsF6 and PF6 salts, which are isostructural and exhibit superconducting transitions at 3.3 and 3.1 K, respectively, under 16.5 kbar.