Dianilinium bis(pyridine-2,6-dicarboxylato-κ3 O 2,N,O 6)cuprate(II) hexahydrate

The asymmetric unit of the title complex, (C6H8N)2[Cu(C7H3NO4)2]·6H2O, contains half a copper(II)–dipicolinate complex located on a twofold rotation axis, one protonated aniline molecule and three solvent water molecules. The CuII atom is coordinated by four O atoms and two N atoms from two dipicolinate ligands in a distorted octahedral environment. In the crystal, the components are linked into a three-dimensional framework by intermolecular O—H⋯O and N—H⋯O interactions.

The asymmetric unit of the title complex, (C 6 H 8 N) 2 [Cu(C 7 H 3-NO 4 ) 2 ]Á6H 2 O, contains half a copper(II)-dipicolinate complex located on a twofold rotation axis, one protonated aniline molecule and three solvent water molecules. The Cu II atom is coordinated by four O atoms and two N atoms from two dipicolinate ligands in a distorted octahedral environment. In the crystal, the components are linked into a threedimensional framework by intermolecular O-HÁ Á ÁO and N-HÁ Á ÁO interactions.

Support for this study by Ferdowsi University of Mashhad is gratefully acknowledged.
Dipicolinic acid is a beneficial compound for the human organism and it is involved in several essential biochemical processes. It shows various biological functions and is a suitable ligand for modeling potential pharmacological compounds because of its low toxicity and amphiphilic nature (Crans, 2000). In recent years, syntheses and crystal structures of a large number of complexes with dipicolinic acid and some amino compounds have been reported (Aghabozorg et al., 2008;Tabatabaee, 2010). Here, we present the preparation and the crystal structure of the title compund, (C 6  There are extensive intermolecular O-H···O, N-H···O and weak C-H···O hydrogen bonds, which increases the stability of the crystal structure ( Fig. 2).

Experimental
The title compound was synthesized by the reaction of copper(II) acetate, pyridine-2,6-dicarboxylic acid (pydcH 2 ) and aniline in aqueous solution in a 1:1:1 molar ratio. Green crystals of the title compound were obtained by slow evaporation of the solvent at room temperature.

Refinement
The H atoms of the water molecules were found in difference Fourier maps and the O-H bond lengths were constrained to 0.85 Å. The positions of the water molecules were optimized using rigid-body constraints (SHELXL AFIX 6). The H atoms from C-H groups were placed in calculated positions. The carbon H atoms were refined in riding model approximation with U iso (H) = 1.2U eq (C) whereas the water hydrogens were treated with 1.5U eq (O).

Figure 1
Molecular structure and atom labeling scheme for title compound with displacement ellipsoids at the 50% probability level. Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. 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 > 2σ(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq