8-Hydroxyquinolinium trichlorido(pyridine-2,6-dicarboxylic acid-κ3O,N,O′)copper(II) dihydrate

The title compound, (C9H8NO)[CuCl3(C7H5NO4)]·2H2O, was prepared by reacting CuII acetate dihydrate, solid 8-hydroxyquinoline (8-HQ), and solid pyridine-2,6-dicarboxylic acid (H2pydc), in a 1:1:1 molar ratio, in an aqueous solution of dilute hydrochloric acid. The CuII atom exhibits a distorted CuO2NCl3 octahedral geometry, coordinating two oxygen atoms and one nitrogen atom from the tridentate H2pydc ligand and three chloride atoms; the nitrogen atom and one chloride atom occupy the axial positions with Cu—N and Cu—Cl bond lengths of 2.011 (2) Å and 2.2067 (9) Å, respectively. In the equatorial plane, the oxygen and chloride atoms are arranged in a cis configuration, with Cu—O bond lengths of 2.366 (2) and 2.424 (2) Å, and Cu—Cl bond lengths of 2.4190 (10) and 2.3688 (11) Å. The asymmetric unit contains 8-HQ+ as a counter-ion and two uncoordinated water molecules. The crystal structure features strong O—H...O and O—H...Cl hydrogen bonds as well as weak interactions including C—H...O, C—H...Cl, Cu—Cl...π, and π–π, which result in a three-dimensional network. A Hirshfeld surface analysis indicates that the most important contributions to the crystal packing involving the main residues are from H...Cl/Cl...H interactions, contributing 40.3% for the anion. Weak H...H contacts contribute 13.2% for the cation and 28.6% for the anion.