New low-dimensional molecular conductors based on bis(ethylenedithio)tetrathiafulvalene radical cation salts with octahedral metal complex anion [ReIVCl6]2–

Abstract

Three new radical cation salts of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with the magnetic metal complex anion [Re^IVCl₆]^2–, viz., β-(BEDT-TTF)₂[ReCl₆] (1), α´-(BEDT TTF)₄[ReCl₆]•(DCE)₂ (2), and δ-(BEDT-TTF)₄[ReCl₆]_1.33•(CB)_0.67 (3) (DCE is dichloroethane, CB is chlorobenzene), were synthesized for the first time. The X-ray diffraction analyses of the obtained crystals at room and low temperatures showed that all of them had the sandwich structure characteristic of alternating anionic and cationic layers, which is characteristic of conducting radical cation salts. The structural phase transition accompanied by unit cell tripling and decreasing the symmetry from monoclinic to triclinic in the low-temperature phase occurs in the crystals of salt 2. The transition is related to modulated displacements of both [Re^IVCl₆]^2– anions and BEDT-TTF radical cations. A specific feature of the crystals of salt 3 is a strong positional disorder in the anionic layer, which is expressed as a random distribution of [Re^IVCl₆]^2– anions and CB solvent molecules in a ratio of 2 : 1 along the channels in the ordered cationic framework.