Abstract Crystal structure analyses, measurements of transport and magnetic properties, and low-temperature X-ray studies of new organic conductors: (ChTM-TTP)2AuBr2, (ChTM-TTP)2GaCl4, and (ChTM-TTP)ReO4, where ChTM-TTP is 2-[4,5-(1,2-cyclohexylenedithio)-1,3-dithiol-2-ylidene]-5-[4,5-bis (methylthio)-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene, have been carried out. In these compounds, the donors form quasi-one-dimensional columns with dimerization induced by the steric hindrance of the 1,2-cyclohexylene unit. The crystal structures and the energy band structures of both AuBr2- and GaCl4- salts are similar to those of the Bechgaard salts. The electrical resistivity and the thermoelectric power show metallic behavior above 100 K for the AuBr2- salt and above 150 K for the GaCl4- salt. The results of the ESR spin susceptibility, the static magnetic susceptibility, and the low-temperature X-ray studies indicate that the ground states of both salts are antiferromagnetic insulators. The Néel temperatures are about 38 K for the AuBr2- salt and about 32 K for the GaCl4- salt. These salts are the first materials showing an antiferromagnetic state among the TTP series conductors. In (ChTM-TTP)2X (X = Au(CN)2, AuBr2, and GaCl4), the strength of the dimerization is related to the charge localization temperature. For the ReO4- salt, the donor to anion ratio is 1 : 1 in spite of the tetrahedral anion being similar to the GaCl4- anion. Although the interstack interactions are not small, the degree of charge transfer of the donor molecule is +1; thus this salt has an energy gap at the Fermi level, in agreement with the semiconducting transport behavior.