Syntheses, structures and electrical properties of cation radical salts based on TTF derivatives containing O, S and Se

Some chemical modifications of TTF-based donor molecules are described. (TMET-STF)2Au(CN)2 is isostructural with the Bechgaard salt and has a quasi one-dimensional electronic structure. We have investigated the pressure effect on the electric resistivity. The metal-insulator transition at 18 K is easily suppressed under pressure (>ca. 2.9 kbar). At ambient pressure, the low-temperature X-ray crystal analyses down to 10 K indicate an enhancement of one-dimensional character. GaCl4 and FeCl4 salts of TOST are metallic down to 4.2 K and have the κ-type structure. The AuBr2 salt of SO is metallic down to 1.5 K and isostructural with β″-(BEDT-TTF)2AuBr2.