Two polymorphic forms of a mixed zinc/copper biquinoline dihydrogenphosphate

Two polymorphic forms of a mixed zinc/copper biquinoline dihydrogenphosphate are presented, showing almost identical monomeric units, viz. (2,2′-biquinoline-κ²N,N′)bis­(di­hydrogen­phos­phato-κO)copper(II)/zinc(II), formulated as [Zn_xCu_1−x(H₂PO₄)₂(C₁₈H₁₂N₂)], with x = 0.88 (1) and 0.90 (2). The cation is tetra­hedrally coordinated to a chelating biquinoline system and two diprotonated phosphate anions. The structures differ mainly in their inter­molecular hydrogen-bonding inter­actions, leading to different packing schemes. No significant evidence of stress due to the Zn/Cu solid solution formation was detected.

(2,2′-Biquinoline-κ²N,N′)bis­(nitrato-κ²O,O′)copper(II)

In the title monomer, [Cu(NO₃)₂(C₁₈H₁₂N₂)], the six-coordinated Cu^II atom lies on a twofold axis which bisects one of the ligands (a chelating biquinoline) and duplicates the remaining ligand, a chelating nitrate. The latter binds in a very asymmetric way, consistent with a Jahn–Teller distortion in the coordination polyhedron which, due to the triple chelation, is extremely distorted and difficult to describe in terms of any regular model.