Naphthalene-1,4,5,8-tetra-carboxylic acid 1,8-anhydride-4,4'-bipyridine (1/1).

The title compound, C(14)H(6)O(7)·C(10)H(8)N(2), has been hydro-thermally synthesized. Structural ananlysis indicates that the crystals are produced by cocrystallization of naphthalene-1,4,5,8-tetra-carboxylic acid 1,8-anhydride and 4,4'-bipyridine (bpy) mol-ecules. The crystal packing is stabilized by inter-molecular O-H⋯N and C-H⋯O hydrogen bonds and π-π stacking inter-actions [centroid-centroid distances = 3.5846 (9) Å].

1-(2',4'-Difluoro-biphenyl-4-yl)ethanone.

In the crystal structure of the title compound, C(14)H(10)F(2)O, the dihedral angles between the benzene rings in the two crystallographically independent mol-ecules are 46.9 (2) and 47.6 (2)°. The mol-ecules are linked into dimers by C-H⋯F inter-actions and these dimers are further stacked into columns along the b axis by π-π inter-actions between the benzene rings [centroid-centroid distance = 3.8221 Å; the dihedral angle between the planes of these rings is 4.87 (2)°]. In addition, C-F⋯π interactions also contribute to the crystal packing (C⋯centroid distance = 3.5919 Å).

Diaqua-bis(8-chloro-1,3-dimethyl-2,6-dioxo-1,2,3,6-tetra-hydro-7H-purinato-κN)copper(II) dihydrate.

The title mononuclear copper(II) complex, [Cu(C(7)H(6)ClN(4)O(2))(2)(H(2)O)(2)]·2H(2)O, based on 8-chloro-theophylline (HCt), has the Cu atom at a center of symmetry in a slightly distorted trans square-planar geometry coordinated by two N atoms of two deprotonated HCt ligands and two O atoms of water mol-ecules. The crystal packing is stabilized by hydrogen bonds involving deprotonated HCt ligands, coordinated water mol-ecules and uncoordinated solvent water mol-ecules.