2,2'-Dimeth-oxy-6,6'-dinitro-biphen-yl.

In the title compound, C(14)H(12)N(2)O(6), the half mol-ecule in the asymmetric unit of the cell is completed by a crystallographic twofold rotation axis, and the two benzene rings of the complete mol-ecule make a dihedral angle of 60.5 (3)°. Furthermore, inter-molecular weak C-H⋯O hydrogen bonds link adjacent mol-ecules, forming a two-dimensional sheet. These sheets are stablized by face-to-face weak π-π contacts [centroid-centroid distance = 3.682 (1) Å] between the nearly parallel [dihedral angle = 0.12 (7)°] benzene rings of the neighboring mol-ecules, resulting in a three-dimensional network.

N,N-Bis(2-hydroxy-benzyl-idene)-2,2'-bipyridyl-3,3'-dicarbohydrazide.

In the title compound, C(26)H(20)N(6)O(4), the two aroylhydrazone side groups exist as diastereomeres, both in the keto form in the crystal structure. The aroylhydrazone units support the mol-ecular conformation through an intra-molecular N-H⋯O hydrogen bond. Two mol-ecules are connected into a centrosymmetric dimer by inter-molecular N-H⋯N hydrogen bonds. These dimers are connected into chains along the a axis by inter-molecular O-H⋯O hydrogen bonds. The combination of these hydrogen bonds results in layers in the bc plane. The layers are further linked by weak C-H⋯π contacts to form a three-dimensional network structure.

6,6'-Dimeth-oxy-2,2',3,3',5-penta-nitro-1,1'-biphen-yl.

In the axially chiral title compound, C(14)H(9)N(5)O(12), the dihedral angle between the two benzene rings is 86.0 (8)°. In the crystal structure, the mol-ecules display a two-dimensional framework formed by weak inter-molecular C-H⋯O hydrogen bonds.