Bis(2,6-diaminopyridin-1-ium) hexaaquacobalt(II) disulfate dihydrate

In the title compound, (C5H8N3)2[Co(H2O)6](SO4)2·2H2O, the complete complex cation is generated by crystallographic inversion symmetry, such that the CoII cation is octahedrally coordinated by six water molecules. The organic cation is essentially planar, with a maximum deviation of 0.013 (1) Å. In the crystal structure, the ions and molecules are linked into a pseudo-layered three-dimensional supramolecular network via O—H⋯O and N—H⋯O hydrogen bonds. Weak intermolecular π–π interactions further stabilize the crystal structure [centroid–centroid distance = 3.5231 (4) Å].

In the title compound, (C 5 H 8 N 3 ) 2 [Co(H 2 O) 6 ](SO 4 ) 2 Á2H 2 O, the complete complex cation is generated by crystallographic inversion symmetry, such that the Co II cation is octahedrally coordinated by six water molecules. The organic cation is essentially planar, with a maximum deviation of 0.013 (1) Å . In the crystal structure, the ions and molecules are linked into a pseudo-layered three-dimensional supramolecular network via O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds. Weak intermolecularinteractions further stabilize the crystal structure [centroid-centroid distance = 3.5231 (4) Å ].
The asymmetric unit of the title complex comprises of half of hexaaquacobalt(II) cation, a protonated 2,6-diaminopyridin-1-ium cation, a sulphate anion and a water molecule of crystallization. The complete complex ( The crystal structure is mainly stabilized by a network of O-H···O and N-H···O hydrogen bonds (Table 2). In this network, the water molecule O atoms and organic N atoms act as donors whereas the sulphate O atoms provide the most extensive part as acceptors. A three-dimensional supramolecular structure (Fig. 2) is built up in such an arrangement that the 2,6-diaminopyridinium organic layers are sandwiched between layers formed through the remaining ions and water molecules. The crystal structure is further stabilized by weak intermolecular Cg1···Cg1 interactions [Cg1···Cg1 = 3.5231 (4) Å; symmetry codes: x-1/2, y, -z+3/2 and x+1/2, y, -z+3/2] where Cg1 is the centroid of C1-C5/N1 pyridine ring.

Experimental
In a round bottom flask was added with stirring 1,4-dioxane (25 ml), 2,6-diaminopyridine (0.02 mol, 2.2 g) and CoSO 4 .7H 2 O (0.01 mol, 2.8 g) dissolved in water. The concoction was refluxed for 24 h and a red solution was then formed. Red blocks of (I) were formed overnight at room temperature. The filtrate was washed with 1,4-dioxane and dried at 333 K.

Refinement
All H-atoms were located from difference Fourier map and allowed to refine freely [ranges of C-H = 0.938 (13) Fig. 1. The molecular structure of (I), showing 50% probability displacement ellipsoids for non-H atoms. The suffix A corresponds to the symmetry code [-x+1, -y+1, -z+1]. Fig. 2. The crystal structure of (I), viewed along the b axis, showing the three-dimensional supramolecular structure. Intermolecular interactions have been shown as dashed lines.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1)K.
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 > 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.

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