Enantiopure Conducting Salts of Dimethylbis(ethylenedithio)tetrathiafulvalene (DM-BEDT-TTF) with the Hexachlororhenate(IV) Anion


  • Dedicated to Professor Marius Andruh on the occasion of his 60th birthday


The enantiopure radical cation salts [(S,S)-DM-BEDT-TTF]4[ReCl6] ([(S,S)-1]4[ReCl6]) and [(R,R)-DM-BEDT-TTF]4[ReCl6] ([(R,R)-1]4[ReCl6]) [DM-BEDT-TTF = dimethylbis(ethylenedithio)tetrathiafulvalene] have been prepared by electrocrystallization of the chiral precursor DM-BEDT-TTF in the presence of NBu4[ReCl5(pyrazine)] (NBu4 = tetra-n-butylammonium cation; pyz = pyrazine) as supporting electrolyte. The single-crystal X-ray analysis shows that the compounds crystallize in the triclinic system, non-centrosymmetric space group P1, and that the donors arrange in parallel columns. The four independent donor molecules possess approximate charges of +1, +1/2, +1/2 and 0, according to the structural parameter analysis and band-structure calculations, which also support the semiconducting behaviour of the materials. The rhenium(IV) ion in both compounds is six-coordinate with six chloro atoms that describe a slightly distorted octahedral environment with Re–Cl distances that cover the short range 2.348–2.374 Å. Magnetic measurements on polycrystalline samples of [(S,S)-1]4[ReCl6] and [(R,R)-1]4[ReCl6] have been investigated in the temperature range 2–295 K. They are practically identical and confirm the presence of high-spin S = 3/2 [ReCl6]2– isolated monomers together with a Pauli paramagnetism, typical of this kind of system. The magnetic susceptibility data are thoroughly reproduced over the whole temperature range with a simple model of isolated S = 3/2 ions with a zero-field splitting plus a temperature-independent paramagnetism (TIP), and the best-fit parameters being gRe = 1.875(2), |D| = 4.50(3) cm–1 and TIP = 3630(20)×10–6 cm3 mol–1 (2D is the energy gap between the MS = ±3/2 and MS = ±1/2 Kramers doublets).