Semiconducting charge-transfer salts of BEDT-TTF [bis(ethylenedithio)tetrathiafulvalene] with hexachlorometallate(IV) anions

Abstract

Two new crystalline charge-transfer salts of BEDT-TTF [bis(ethylenedithio)tetrathiafulvalene] containing hexachlorometallate anions of 5d elements have been synthesised, characterised structurally and their magnetic and conducting behaviour investigated. α-(BEDT-TTF) ₄ [ReCl ₆ ]C ₆ H ₅ CN is triclinic [P; a=9.455(2), b=11.306(3), c=18.193(5) Å; α=101.85(2), β=92.74(2), γ=110.52(2)°; Z=1]. Its structure consists of alternate layers of BEDT-TTF and of [ReCl6 ]2- C6H5CN, the former consisting of two crystallographically independent stacks, in one of which the molecules carry a charge close to +1 while in the other they are approximately neutral. The cations lie between the [ReCl6 ]2- moieties while the neutral molecules are closest to the C6H5CN species showing that the structure is determined by electrostatic interactions. (BEDT-TTF)2 [IrCl6 ] is likewise triclinic [P; a=8.721(1), b=10.257(2), c=11.086(2) Å; α=111.00(1), β=98.31(1), γ=103.32(1)°; Z=1]. Its packing motif is new among BEDT-TTF salts, containing no discrete layers of anions and cations. Face-to-face BEDT-TTF dimers form an infinite three-dimensional network. Both compounds are semiconducting and their magnetic properties are dominated by the Curie–Weiss behaviour of the anions.