X-ray and synchrotron diffraction studies of 2-(pyridin-2-yl)-1,10-phenanthroline in the role of ligand for two copper polymorphs or hydrogen bonded with 2,2,6,6-tetra­methyl-4-oxopiperidinium hexa­fluoro­phosphate

Different extended packing motifs of dichlorido[2-(pyridin-2-yl)-1,10-phenanthroline]copper(II), [CuCl₂(C₁₇H₁₁N₃)], are obtained, depending on the crystallization conditions. A triclinic form, (I), is obtained from di­methyl­formamide–diethyl ether or methanol, whereas crystallization from di­methyl­formamide–water yields a monoclinic form, (II). In each case, the Cu^II centre is in a five-coordinate distorted square-pyramidal geometry. The extended packing for both forms can be described as a highly offset π-stacking arrangement, with inter­layer distances of 3.674 (3) and 3.679 (3) Å for forms (I) and (II), respectively. The reaction of diprotonated Pt(tmpip₂NCN)Cl [tmpip₂NCN = 2,6-bis­(2,2,6,6-tetra­methyl­piperidylmeth­yl)benzyl] with AgPF₆ under acidic conditions, followed by the addition of 2-(pyridin-2-yl)-1,10-phenanthroline, results in a hydrogen-bonded cocrystal, 2,2,6,6-tetra­methyl-4-oxopiperidinium hexa­fluoro­phosphate–2-(pyridin-2-yl)-1,10-phenanthroline (1/1), C₉H₁₈NO⁺·PF₆⁻·C₁₇H₁₁N₃, (III). The extended packing maximizes π–π inter­actions in a parallel face-to-face arrangement, with an inter­layer stacking distance of 3.4960 (14) Å.