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The Schiff base compounds N,N'-bis[(E)-quinoxalin-2-ylmethylidene]propane-1,3-diamine, C(21)H(18)N(6), (I), and N,N'-bis[(E)-quinoxalin-2-ylmethylidene]butane-1,4-diamine, C(22)H(20)N(6), (II), crystallize in the monoclinic crystal system. These molecules have crystallographically imposed symmetry. Compound (I) is located on a crystallographic twofold axis and (II) is located on an inversion centre. The molecular conformations of these crystal structures are stabilized by aromatic pi-pi stacking interactions.

In the title mol-ecule, C(16)H(11)N(5), the mean planes of the quinoxaline and indazole fragments form a dihedral angle of 10.62 (5)°. In the crystal, weak inter-molecular N-H⋯N hydrogen bonds link the mol-ecules into zigzag chains extending in the [001] direction. The crystal packing also exhibits π-π inter-actions [centroid-centroid distances of 3.7080 (2) and 3.8220 (5) Å], which form stacks of the mol-ecules parallel to the a axis.

The asymmetric unit of the title compound, C(11)H(8)N(4), contains two independent mol-ecules. In the crystal structure, inter-molecular N-H⋯N hydrogen bonds link mol-ecules into ribbons extended in the [100] direction.

In the mol-ecule of the title compound, C(20)H(16)N(6), the central C-C bond lies on a crystallographic inversion centre. The quinoxalidine ring is nearly planar, with a maximum deviation of 0.021 (2) Å from the mean plane. The crystal structure is stabilized by inter-molecular C-H⋯N inter-actions, leading to the formation of a layer-like structure, which extends along the a axis.