Crystal structure and physical properties of (EDS-TTF)2FeBr4

Crystal structure, transport and magnetic properties of (EDS-TTF)2FeBr4 (EDS-TTF: ethylenediselenotetrathiafulvalene) are reported. Between one-dimensional columns of donors and quasi square-lattices of FeBr4 anions, close Br⋯Se van der Waals contacts and CH⋯Br type hydrogen bonds are observed. This salt shows high room-temperature conductivity and metal–insulator transition at ca. 250 K (σRT=400 S cm−1, EA=380 K). The magnetic susceptibility obeys the Curie–Weiss law (C=4.58 emu K mol−1, Θ=−0.9 K) without showing any magnetic transition down to 1.8 K. The weak π–d interaction can be due to the small contribution of Se 4p orbitals to the HOMO of EDS-TTF.