Abstract

Two polymorphic forms of a mixed zinc/copper biquinoline dihydrogenphosphate are presented, showing almost identical monomeric units, viz. (2,2′-biquinoline-2 N,N′)bis-(di-hydrogen-phos- phato-O)copper(II)/zinc(II), formulated as [Zn x Cu1-x (H2PO4)2(C18H12N2)], with x = 0.88 (1) and 0.90 (2). The cation is tetra-hedrally coordinated to a chelating biquinoline system and two diprotonated phosphate anions. The structures differ mainly in their inter-molecular hydrogen-bonding inter-actions, leading to different packing schemes. No significant evidence of stress due to the Zn/Cu solid solution formation was detected. © International Union of Crystallography 2007.