Abstract The molecular and crystal structures of the title compounds, where TMEO-TTP is 2-[4,5-bis(methylthio)1,3-dithiol-2-ylidene]-5-[4,5-ethylenedioxy-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene, have been investigated by X-ray crystal structure analysis. The BDT-TTP skeleton of neutral TMEO-TTP adopts a slightly flat chair conformation. The crystal has a columnar structure, in which the molecules dimerize in a head-to-tail manner. Several S···S contacts shorter than the sum of the van der Waals radii (3.70 Å) are observed along the transverse direction. (TMEO-TTP)[AuBr2]·THF also has a columnar structure in which the donor molecules dimerize. However, “side-by-side” interaction between the donors is prohibited because the AuBr2 anions and the THF molecules are located at the sides of the donor molecules.