Aqua(4-hydroxypyridine-2,6-dicarboxylato)(1,10-phenanothroline)copper(II) 4.5-hydrate

The title compound, [Cu(C7H3NO5)(C12H8N2)(H2O)]·4.5H2O or [Cu(hypydc)(phen)(H2O)]·4.5H2O (phen is 1,10-phenanthroline and hypydcH2 is 4-hydroxypyridine-2,6-dicarboxylic acid), was obtained by the reaction of copper(II) nitrate hexahydrate with the proton-transfer compound (phenH)2(hypydc) in aqueous solution. Both the cationic and the anionic fragments of the proton-transfer compound are involved in complexation. Each CuII atom has a distorted octahedral geometry. It is hexacoordinated by three O atoms and three N atoms, from one phen fragment (as bidentate ligand), one (hypydc)2− unit (as tridentate ligand) and a water molecule. In the crystal structure, O—H⋯O and C—H⋯O hydrogen bonds, and π–π stacking interactions [centroid-to-centroid distance 3.5642 (11) Å] between the phen ring systems, contribute to the formation of a three-dimensional supramolecular structure.

Financial support from Ilam University and the Teacher Training University is gratefully acknowledged.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SU2032).
Aqua(4-hydroxypyridine-2,6-dicarboxylato)(1,10-phenanothroline)copper(II) 4.5-hydrate H. Aghabozorg, E. Motyeian, J. Soleimannejad, M. Ghadermazi and J. Attar Gharamaleki Comment Non-covalent interactions, including hydrogen bonds, are of great importance in stabilizing structures in the solid state. We have synthesized several proton transfer compounds, some with remaining sites as electron donors that can coordinate to metal ions Aghabozorg, Daneshvar et al., 2007 and references therein). A wide range of different hydrogen bonds were observed in these compounds and water molecules of crystallization were also involved in hydrogen bonding. Here, we report on the synthesis and crystal structure of the title compound, (I).
The title complex crystallizes in the orthorhombic space group Fdd2, with sixteen molecules in the unit cell. The molecular structure is shown in Fig. 1. Both the cationic and anionic fragments of the starting proton transfer compound are involved in complexation. Each Cu II atom has a distorted octahedral geometry. It is coordinated by one 1,10-phenanthroline ligand, (phen as bidentate ligand), one 4-hydroxypyridine-2,6-dicarboxylate group, [(hypydc) 2− as a tridentate ligand] and one coordinated water molecule. The axial bond lengths, Cu1-O2 and Cu1-O3 [2.3679 (9) and 2.3205 (11) Å, respectively] are longer than the equitoral metal-ligand bond lengths [1.9996 (8) − 2.0370 (9) Å], probabaly due to the Jahn-Teller effect. The dihedral angle between the planes passing through the (hypydc) 2and (phen) fragments is 83.41 (4)°, indicating that these to units are almost perpendicular to one another.

Experimental
The proton transfer compound, (phenH) 2 (hypydc), was prepared by the reaction of 4-hydroxypyridine-2,6-dicarboxylic acid, hypydcH 2 , with 1,10-phenanthroline, (phen). Cu(NO 3 ) 2 ·6H 2 O (125 mg, 0.5 mmol) in water (20 ml) and the proton transfer compound, (phenH) 2 (hypydc) (500 mg, 1.0 mmol) in water (20 ml), in a 1:2 molar ratio, were mixed. Blue crystals of (I) were obtained by the slow evaporation at room temperature.    Aqua(4-hydroxypyridine-2,6-dicarboxylato)(1,10-phenanothroline)copper(II) 4.5-hydrate Crystal data [Cu(C 7  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.