Solvated and solvent-free forms of N,N '-dithiodiphthalimide

N,N'-Dithiodiphthalimide, C16H8N2O4S2, crystallizes from ethyl acetate with two independent molecules in the asymmetric unit, in which the N-S-S-N tor sion angles are -83.59 (19) and 92.9 (2)degrees. The molecules are linked b y C-H . . . O hydrogen bonds and aromatic pi-pi -stacking interactions into a three-dimensional framework. When crystallized from either dichlorometha ne or ethanol, solvates are formed in which the molecules of the title comp ound lie across twofold rotation axes in space group C2/c, with N-S-S-N tor sion angles of 93.54 (7) and 96.14 (11)degrees. There are no hydrogen bonds in these solvates, but the molecules are linked by aromatic pi-pis-stackin g interactions into chains, between which there are continuous channels. Di sordered solvent molecules occupy these channels, which account for ca 20% of the unit-cell volume.