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 torsion angles are -83.59 (19) and 92.9 (2)degrees. The molecules are linked by C-H . . . O hydrogen bonds and aromatic pi-pi -stacking interactions into a three-dimensional framework. When crystallized from either dichloromethane or ethanol, solvates are formed in which the molecules of the title compound lie across twofold rotation axes in space group C2/c, with N-S-S-N torsion 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-stacking interactions into chains, between which there are continuous channels. Disordered solvent molecules occupy these channels, which account for ca 20% of the unit-cell volume.