Triclinic and orthorhombic polymorphs of 2-iodo-4-nitro­aniline: interplay of hydrogen bonds, nitro...I interactions and aromatic [pi]-[pi]-stacking interactions

In the triclinic polymorph of 2-iodo-4-nitro­aniline, C₆H₅IN₂O₂, space group P, the mol­ecules are linked by paired N-­H...O hydrogen bonds into C(8)[R(6)] chains of rings. These chains are linked into sheets by nitro...I interactions, and the sheets are pairwise linked by aromatic [pi]-[pi]-stacking interactions. In the orthorhombic polymorph, space group Pbca, the mol­ecules are linked by single N-H...O hydrogen bonds into spiral C(8) chains; the chains are linked by nitro...O interactions into sheets, each of which is linked to its two immediate neighbours by aromatic [pi]-[pi]-stacking inter­actions, so producing a continuous three-dimensional ­structure.