Conformational polymorphism of (E,E)-N,N′-bis(4-nitrobenzylidene)benzene-1,4-diamine

Abstract

Two polymorphs of (E,E)-N,N'-bis(4-nitrobenzylidene)benzene-1,4-diamine, C(20)H(14)N(4)O(4), (I), have been identified. In each case, the molecule lies across a crystallographic inversion centre. The supramolecular structure of the first polymorph, (I-1), features stacking based on π-π interactions assisted by weak hydrogen bonds involving the nitro groups. The second polymorph, (I-2), displays a perpendicular arrangement of molecules linked via the nitro groups, combined with weak C-H···O hydrogen bonds. Both crystal structures are compared with that of the carbon analogue (E,E)-1,4-bis[2-(4-nitrophenyl)ethenyl]benzene, (II).