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-tetrathiafulvalenothio quinone-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 comparativ ely 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 susceptibili ties (chi(p)'s) of the Cu complexes were composed of both a component due t o the localized Cu spins obeying the Curie-Weiss law and a temperature-inde pendent chi(p) due to the conducting pi electrons on the 1- or 2-stacked co lumns. From the Curie constants obtained, the degrees of intramolecular ele ctron transfer from 1 and 2 to CuBr2 moieties were estimated at ca. 90% and 60%, respectively. The small, negative Weiss temperatures suggest very wea k antiferromagnetic interactions among the Cu spins on the CuBr2 moieties.