Electrical conducting and magnetic properties in FeBr4 salts of dimethylthio- and ethylenedithio-tetrathiafulvalenothioquinone-1, 3-dithiolemethides

The reaction of new donor molecules, dimethylthio- (la) and ethylenedithio- tetrathiafulvalenothioquinone-1, 3-dithiolemethides (Ib) with FeBr3 in CH3C N/CS2, afforded the corresponding FeBr4 salts (1a . FeBr4 and 1b . FeBr4). From the X-ray structure analysis of 1a . FeBr4 the la molecules are strong ly dimerized, but stacked one-onedimensionally. The FeBr4 ion are inserted between the la stacks, but separated from each other. The room-temperature electrical conductivities (sigma (n)'s) on the compressed pellets of 1a . F eBr4 and 1b . FeBr4 were < 10(-5) and 10(-3) S . cm(-1), respectively. The paramagnetic susceptibilities (chi (p)'s) obeyed a Curie-Weiss law (chi (p) = C/(T - theta); C = 4.61 emu.K.mol(-1) and theta = -5.4 K for 1a . FeBr4, and C = 4.55 emu.K.mol(-1) and theta = -31.2 K for 1b . FeBr4, respectivel y.