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-oxo- piperidinium hexafluorophosphate Jeanette A. Krause, a * Daoli Zhao, a Sayandev Chatterjee, a ‡ Bonnie M. Yeung, a William B. Connick a and Sibrina N. Collins b a Department of Chemistry, University of Cincinnati, Cincinnati, OH 45221-0172, USA, and b Department of Chemistry, College of Wooster, Wooster, OH 44691, USA Correspondence e-mail: jeanette.krause@uc.edu Received 22 February 2013 Accepted 9 April 2013 Different extended packing motifs of dichlorido[2-(pyridin-2- yl)-1,10-phenanthroline]copper(II), [CuCl 2 (C 17 H 11 N 3 )], 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 -stacking arrangement, with interlayer distances of 3.674 (3) and 3.679 (3) A ˚ for forms (I) and (II), respectively. The reaction of diprotonated Pt(tmpip 2 NCN)Cl [tmpip 2 NCN = 2,6-bis- (2,2,6,6-tetramethylpiperidylmethyl)benzyl] with AgPF 6 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), C 9 H 18 NO + PF 6  - C 17 H 11 N 3 , (III). The extended packing maximizes – inter- actions in a parallel face-to-face arrangement, with an interlayer stacking distance of 3.4960 (14) A ˚ . Comment Our ongoing research efforts primarily focus on utilizing bi- and tridentate chelating imine-based ligands: (i) to tune the electronic nature of square-planar d 8 -electron and octahedral d 6 -electron late transition metals for promising multi-redox catalytic applications and to explore their photophysical properties (see, for example, Pt complexes: Chatterjee et al. , 2012; Chatterjee, Krause, Connick et al., 2010; Chatterjee, Krause, Oliver et al., 2010; Green et al., 2005; Grove et al. , 2008; Jude, Carroll & Connick, 2003; Jude, Krause Bauer & Connick, 2003; Pd complexes: Tastan et al., 2006); (ii) to bridge multiple metal centres to form more elaborate molecular architectures (Jude et al. , 2005; Willison et al., 2008); and (iii) to continue our studies utilizing coinage metals (Collins et al. , 2007). Our most recent focus has been the tridentate ligand 2-(pyridin-2-yl)-1,10-phenanthroline (php). We report here the synthesis and solid-state structure of Cu(php)Cl 2 in the triclinic, (I), and monoclinic, (II), forms, obtained from different crystallization media. In addition, the neutral php ligand can act as a hydrogen-bond acceptor to an oxopiper- idinium salt, as illustrated in 2,2,6,6-tetramethyl-4-oxopiper- idinium hexafluorophosphate–2-(pyridin-2-yl)-1,10-phenan- throline (1/1), (III). The crystallization medium plays a critical role in influen- cing the solid-state packing motifs that molecules adopt. Most often this is accomplished by solvents participating in close- contact interactions (e.g. hydrogen-bonding or – inter- actions) with the complex of interest, or residing in channels or cavities created by the surrounding complexes, as found for vapour- and anion-sensing crystals (Grove et al. , 2008; Taylor, 2011). However, there can be instances, as in the present study, where the solvent, instead of affecting the close contacts, modifies the extended motif adopted. These differences in packing can be attributed to differences in the physical properties (e.g. electronegativity and pK a ) introduced by the new solvent (Aakero ¨y et al. , 2009, 2010). The reaction of CuCl 2 2H 2 O with php results in the formation of Cu(php)Cl 2 . Two crystallographic forms of Cu- metal-organic compounds 498 # 2013 International Union of Crystallography doi:10.1107/S0108270113009773 Acta Cryst. (2013). C69, 498–502 Acta Crystallographica Section C Crystal Structure Communications ISSN 0108-2701 ‡ Current address: Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA 99357, USA.