The preparation of the bis(1,2,3,5-dithiadiazolyl) radicals [S2N2C]-X-[CN2S2], where X is a heterocyclic bridging group (X = piperazine, thiophene, bithiophene) is described. Crystal structures of the piperazine- and bithiophene-bridged diradicals have been determined by single-crystal X-ray diffraction. The two compounds are isostructural, belonging to the monoclinic space group P2(1)/n; for the piperazine derivative a = 5.9913(6) Angstrom, b = 19.1958(16) Angstrom, c = 9.1244(6) Angstrom, beta = 100.314(7)degrees, and Z = 4. For the bithiophene derivative a = 5.9907(17) Angstrom, b = 24.272(3) Angstrom, c = 9.1740(14) Angstrom, beta = 102.961(18)degrees, and Z = 4. The diradicals associate as cofacial dimers which adopt a herringbone packing pattern analogous to that observed previously for the 1,4-phenylene-bridged derivative. in all three structures the herringbone arrays are characterized by a series of close interdimer S-S contacts along the spine. Consistently, the results of extended Huckel band structure calculations indicate highly developed two-dimensional electronic structures.