A new bis(ethylenedithio)tetrathiafulvalene chloride: (BEDT-TTF) 2Cl·3H 2O

Abstract

A new BEDT-TTF chloride (BEDT-TTF) 2Cl·3H 2O was obtained by electrochemical oxidation of the donor in dichloroethane solution containing K 2[Cu(OX 2−) 2]·2H 2O (OX 2−: oxalate ion). The compound crystallized in the space group Pcca with a = 32.621(1), b = 6.720(3) and c = 14.894(6) A ̊ . The unit cell contained four units of the compound formula. Close side-by-side contacts of adjacent donor molecules formed a one-dimensional array that was parallel to the b-axis. In this array, the shortest SS distance of 3.47 Å was less than the van der Waals contact of 3.70 Å. The donor molecules were also stacked face-to-face along the c-axis. The shortest SS distance in the stack, however, was 3.76 Å; there was no SS pair closer than the van der Waals contact. The electrical conductivity along the b-axis was c. 90 S cm − at 300 K, and exhibited metallic temperature dependence down to c. 120 K; around this temperature, a metal-insulator transition occurred. One-dimensional charge transport is attributed to the isolated array of BEDT-TTF molecules. When K 2(OX 2−)·H 2O was used as an electrolyte instead of the bis(oxalato)cuprate(II), the known chloride, (BEDT-TTF) 3Cl 2·2H 2O, was obtained.