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 (sigma) 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 sigma exhibited, however, semiconducting behavior with a very small activation energy of 0.18 eV. The observed paramagnetic susceptibilities (chi(p)'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 chi(p) due to the conducting pi 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 very weak antiferromagnetic interactions among the Cu spins on the CuBr2 moieties.