Physical and chemical properties of MDSe-TTF and EDSe-TTF salts

The Se-containing unsymmetrical donor, MDSe-TTF and EDSe-TTF, were synthesized. 0-(MDSe-TTF)2Au(CN)2 and (MDSe-TTF)2AuI2 are metallic down to 15K and 40K respectively and in the former salt, the metal-insulator transition is suppressed down to 0.4K under 2kbar. The ESR measurements show that the intensity of (EDSe-TTF)2AuI2 remains finite at 4K, while (EDT-TTF)2AuI2 has a distinct TMI=40K. The Se-introduced donor salts show the metallic behaviors down to lower temperatures, compared with S-introduced analogue. Not only AuI2 and Au(CN)2 salts but also other salts are presented.