Polymorphs and pseudopolymorphs of N, N'-dithio-bisphthalimide

N,N'-Dithiobisphthalimide, C16H8N2O4S2 (I), forms a wide range of polymorphs and solvates (pseudopolymorphs). When (I) is crystallized from methanol it yields a solvent-free polymorph (4), in Pna2(1) with Z' = 1, in which the molecules are linked into chains by a single C-H...O hydrogen bond: crystallization from either acetonitrile or dimethylformamide produces a monoclinic polymorph (5), in P2(1)/c with Z' = 2, also solvent-free, in which the molecules are linked into molecular ladders. Nitromethane forms a monosolvate, C16H8N2O4S2.CH3NO2 (6), in P2(1)/c with Z' = 1, in which the solvent molecules are linked to the molecules of (I) not only via a conventional C-H...O hydrogen bond but also via a polarized multicentre interaction involving all three C-H bonds of the solvent molecule. Chlorobenzene forms a precise hemisolvate, C16H8N2O4S2.0.5C(6)H(5)Cl (7), in P (1) over bar with Z' = 1, while ethylbenzene forms an approximate hemisolvate 2C(16)H(8)N(2)O(4)S(2).0.913C(6)H(5)C(2)H(5).0.087H(2)O (8), in P2(1)/c with eight molecules of (I) per unit cell. In both solvates the molecules of (I) are linked, in (7) by pi...pi stacking interactions augmented by weak C-H...O hydrogen bonds and in (8) by stronger C-H...O hydrogen bonds: the solvent molecules lie in isolated cavities, disordered across inversion centres in (7) and fully ordered in general positions in (8). Crystallization of (I) either from tetrahydrofuran or from wet tert-butanol yields isomorphous solvates (9) and (10), respectively, in C2/c with Z' = 0.5, in which molecules of (I) lie across twofold rotation axes and are linked by pi...pi stacking interactions and very weak C-H...O hydrogen bonds, forming a framework enclosing continuous channels: highly disordered solvent molecules lie within these channels. p-Xylene and toluene form isomorphous hemisolvates (11) and (12) with unit cells metrically very similar to those of (9) and (10), but in P2(1)/n with Z' = 1: in these two solvates the molecules of (I) are linked into a framework by very short C-H...O hydrogen bonds; the solvent molecules lie within continuous channels, but they are localized across inversion centres so that the toluene is disordered across an inversion centre.