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 dichlorido2‐(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.