Isomers and polymorphs of (E,E)-1,4-bis(nitrophenyl)-2,3-diaza-1,3-butadienes

The structures of five of the possible six isomers of (E, E)1,4-bis(nitrophenyl)-2,3-diaza-1,3-butadiene are reported, including two polymorphs of one of the isomers. (E, E)-1,4Bis(2-nitrophenyl)-2,3-diaza-1,3-butadiene, C14H10N4O4 ( I), crystallizes in two polymorphic forms (Ia) and (Ib) in which the molecules lie across centres of inversion in space groups P2(1)/n and P2(1)/c, respectively: the molecules in (Ia) and (Ib) are linked into chains by aromatic pi (...) pi stacking interactions and C-H (...) pi(arene) hydrogen bonds, respectively. Molecules of (E,E)-1-(2-nitrophenyl)-4-(3-nitrophenyl)-2,3-diaza-1,3-butadiene (II) are linked into sheets by two independent C-H (...) O hydrogen bonds. The molecules of (E, E)-1,4-bis(3-nitrophenyl)- 2,3-diaza-1,3- butadiene (III) lie across inversion centres in the space group P2(1)/n, and a combination of a C-H (...) O hydrogen bond and a pi (...) pi stacking interaction links the molecules into sheets. A total of four independent C H (...) O hydrogen bonds link the molecules of (E, E)-1-(3-nitrophenyl)- 4-(4-nitrophenyl)-2,3-diaza-1,3-butadiene (IV) into sheets. In (E,E)-1,4-bis(4-nitrophenyl)-2,3-diaza-1,3-butadiene (V) the molecules, which lie across centres of inversion in the space group P2(1)/n, are linked by just two independent C-H (...) O hydrogen bonds into a three-dimensional framework.