New low-dimensional organic metals of (BEDT-ATD)2X(THF) (X = PF6, AsF6), stable at low temperature

The cation radical salts with a new electron donor 4,11-bis(4′,5′-ethylenedithio-1′,3′-dithiol-2′-ylidene)-4,11-dihydroanthra[2,3-c] [1,2,5]thiadiazole (BEDT-ATD) have been prepared by an electrochemical oxidation in tetrahydrofuran (THF). The salts with PF6− and AsF6− anions were obtained as (BEDT-ATD)2X(THF) (X = PF6, AsF6). The electrical resistivities at room temperature were 0.04 and 0.02 Ω cm for the PF6 salt and the AsF6 salt, respectively. Both salts showed a metal-like behavior in the electrical conduction. The spin susceptibility revealed a Pauli paramagnetism down to 3 K, indicating a metallic state. A semiconducting phase appeared by applying pressure above 2.5 kbar.