Crystal structures, and electrical conduction and magnetic properties in CuCl4 salts of dimethylthio- and ethylenedithio-tetrathiafulvalenothioquinone-1,3-dithiolemethides

Abstract

The reaction of dimethylthio- (1) and ethylenedithio-tetrathiafulvalenothioquinone-1,3-dithiolemethides (2) with CuCl2 afforded the corresponding CuCl4 salts, (1)2·CuCl4 and (2)3·CuCl4. For (1)2·CuCl4 the 1 molecules are stacked to form a one-dimensional column, and in each column the neighboring 1 molecules are dimerized. On the other hand, the 2 molecules in (2)3·CuCl4 are stacked one-dimensionally in a triad unit. The CuCl4 ions intervene between the 1- or 2-stacked columns in each case. The electrical resistivities (ρ) for single crystals of (1)2·CuCl4 and (2)3·CuCl4 were 3 × 104 and 0.6 Ω cm at room temperature, respectively. The ρ value of (2)3·CuCl4 increased continuously on cooling, and its activation energy was 0.15 eV, which became gradually smaller with increasing applied pressure. For (1)2·CuCl4 the Cu(II) spins on the CuCl4 ions were only present whilst (2)3·CuCl4 involved both conducting π electrons on the 2-stacked column and localized Cu(II) spins on the CuCl4 ions which did not interact with each other between 300 and ca. 170 K, but below ca. 170 K the conducting π electrons disappeared, presumably as a result of interaction with the localized d spins.