1:1 complexes of dimethylthio- and ethylenedithio-tetrathiafulvalenothioquinone-1,3-dithiolemethides with CuBr2 as a new type of pi/d molecular system.

The reaction of dimethylthio- (1) and ethylenedithio-tetrathiafulvalenothioquinone-1,3-dithiolemethides (2) with CuBr2 gave 1:1 complexes between the donors and CuBr2, 1·CuBr2 and 2·CuBr2, in which the Cu atom of CuBr2 binds to the thiocarbonyl S atom in 1 and 2. The electrical conductivity (σ) of 1·CuBr2 at room temperature was ca. 10-5 S cm-1, while a comparatively high value of 4.0 S cm-1 was obtained for 2·CuBr2, whose temperature dependence of σ exhibited, however, semiconducting behavior with a very small activation energy of 0.18 eV. The observed paramagnetic susceptibilities (χp's) of the Cu complexes were composed of both a component due to the localized Cu spins obeying the Curie−Weiss law and a temperature-independent χp due to the conducting π electrons on the 1- or 2-stacked columns. From the Curie constants obtained, the degrees of intramolecular electron transfer from 1 and 2 to CuBr2 moieties were estimated at ca. 90% and 60%, respectively. The small, negative Weiss temperatures suggest ve...