Pressure-Induced Superconductivity in (MDT-TS)(AuI2) 0.441 [MDT- TS = 5H-2-(1,3-diselenol-2-ylidene)1,3,4,6-tetrathiapentalene]: A New Organic Superconductor Possessing an Incommensurate Anion Lattice

A selenium-containing TTF-type electron donor, MDT-TS [5H-2-(1,3-diselenol-2-ylidene)-1,3,4,6tetrathiapentalene] was effectively synthesized by a two-step reaction and utilized for electrocrystallization with an AuI2- anion. The resulting salt, (MDT-TS)(AuI2)0.441, has a unique crystal packing, in which the donor subcell and the anion lattice are incommensurate. Although the salt has relatively high conductivity at room temperature (600 S cm-1), it showed a metal-insulator (MI) transition at TMI = 50 K. Application of hydrostatic pressure suppressed the MI transition, and at 11.4 kbar (MDT-TS)(AuI2)0.441 showed a superconducting transition at Tc = 4.7 K.