Solvent-dependent polymorphism in isomeric N-(nitrobenzylidene)iodoanilines.

Three of the nine isomeric N-(nitrobenzylidene)iodoanilines, C13H9IN2O2, have been found, when crystallized from acetone, to yield polymorphs which differ from those obtained upon crystallization from ethanol. In the second polymorph of 2-iodo-N-(2-nitrobenzylidene)aniline, the molecules are disordered across inversion centres in space group C2/c, but there are no direction-specific interactions between the molecules. In the second polymorph of 2-iodo-N-(3-nitrobenzylidene)aniline, the molecules adopt a different conformation from those in the first polymorph, and they are linked into sheets by a combination of a three-centre iodo-nitro interaction and an aromatic pi-pi stacking interaction, both of which are absent from the supramolecular structure of the first polymorph. The second polymorph of 3-iodo-N-(2-nitrobenzylidene)aniline crystallizes with Z' = 2 in space group P2(1), and the molecules are linked into sheets by one C-H...O hydrogen bond and two C-H...pi(arene) hydrogen bonds.