Highly conducting 1:1 radical cation salts: (DMTSA)X with X = NO₃ and BF₄

(DMTSA)NO₃ and -BF₄ show high conductivity at room temperature, in spite of fully ionic salt of 1:1 stoichiometry with uniform segregated stack column structure. DMTSA denotes 2,3-dimethyltetraseleno-anthracene. The NO₃ salt is semiconducting below room temperature, and the BF₄ salt is metallic above 220 K and semiconducting at lower temperatures. We found that their magnetic susceptibility is paramagnetic and independent of temperature from 300 K down to 10 K in common. The obtained magnetic property can not be attributed to conduction electrons but discussed in terms of Mott insulating state. Furthermore, high pressure experiment reveals that the NO₃ salt is not semiconducting but rather semi-metallic, and more that the BF₄ salt shows a small conductive anomaly around 70 K and maintains metallic at low temperatures under the pressure of 0.5 GPa.