An unsymmetrical tetrathiafulvalene with a fused 1,2,5-thiadiazole ring and methylthio groups.

The title compound, 5-(4,5-dimethylthio-1,3-dithiol-2-ylidene)-1,3-diaza-2,4,6-trithiapentalene (4,5-dimethylthio [1,2,5]thiadiazolotetrathiafulvalene, molecular formula C(8)H(6)N(2)S(7)) crystallizes in the P2(1)/n space group with one molecule in the asymmetric unit. The molecular framework is planar within 0.19 A. The molecules form a head-to-tail type of pi-stacking dimer with an interplanar distance is 3.50(1) A, where methylthio groups face away from each other. The molecules are also linked by weak intermolecular S...S heteroatom interactions [3.497(1) and 3.572(1) A] to construct a unique one-dimensional molecular tape structure.