A new compound in the BEDT-TTF family [BEDT-TTF = bis-(ethyl-enedi-thio)-tetra-thia-fulvalene] with a tetra-thio-cyanato-cuprate(II) anion, (BEDT-TTF)4[Cu(NCS)4]

Christophe Faulmann; Benoît Cormary; Lydie Valade; Kane Jacob; Dominique de Caro

doi:10.1107/S2056989018015293

A new compound in the BEDT-TTF family [BEDT-TTF = bis-(ethyl-enedi-thio)-tetra-thia-fulvalene] with a tetra-thio-cyanato-cuprate(II) anion, (BEDT-TTF)₄[Cu(NCS)₄]

Acta Crystallogr E Crystallogr Commun. 2018 Nov 9;74(Pt 12):1755-1758. doi: 10.1107/S2056989018015293. eCollection 2018 Dec 1.

Authors

Christophe Faulmann¹, Benoît Cormary¹, Lydie Valade¹, Kane Jacob¹, Dominique de Caro¹

Affiliation

¹ CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, BP44099, 31077 Toulouse Cedex 4, France, Université de Toulouse, UPS, INPT, 31077 Toulouse Cedex 4, France.

Abstract

A new phase combining BEDT-TTF and [Cu(NCS)₄]^2- as the counter-anion, namely bis-[bis(ethyl-enedi-thio)-tetra-thia-fulvalenium] tetra-thio-cyanato-cuprate(II) bis-[bis(ethyl-ene-di-thio)-tetra-thia-fulvalene], (C₁₀H₈S₈)₂[Cu(NCS)₄]·2C₁₀H₈S₈ or (BEDT-TTF)₄[Cu(NCS)₄] was obtained during a galvanostatic electrocrystallization process. As previously observed with BEDT-TTF-based compounds with oxalatometallate anions, the BEDT-TTF mol-ecules in (BEDT-TTF)₄[Cu(NCS)₄] exhibit the so-called pseudo-κ arrangement, with two BEDT-TTF mol-ecules being positively charged and two electronically neutral. The bond lengths and angles in the two unique BEDT-TTF mol-ecules differ slightly. The crystal structure consists of layers of BEDT-TTF mol-ecules extending parallel to (001). The width of this layer corresponds to the length of the a axis [16.9036 (17) Å]. The BEDT-TTF layers are separated by layers of centrosymmetric square-planar [Cu(NCS)₄]^2- dianions.

Keywords: BEDT-TTF; Cu(NCS)2; crystal structure; pseudo-κ arrangement; superconductor.