Di-μ-hydroxido-κ4 O:O-di-μ-perchlorato-κ4 O:O′-bis[(2,2′-bipyridine-κ2 N,N′)copper(II)]

In the title binuclear copper(II) complex, [Cu2(ClO4)2(OH)2(C10H8N2)2], the CuII ion is coordinated in the form of a Jahn–Teller distorted octahedron by two bipyridine N atoms, two perchlorate O atoms and two hydroxide O atoms, and displays a distorted octahedral geometry. The molecule belongs to the symmetry point group C 2h. The CuII ion is located on a twofold rotation axis and the hydroxide and perchlorate ligands are located on a mirror plane. Within the dinuclear molecule, the Cu⋯Cu separation is 2.8614 (7) Å. The crystal structure exhibits O—H⋯O, C—H⋯O and π–π [centroid–centroid distance = 3.5374 (13) Å] interactions.

In the title binuclear copper(II) complex, [Cu 2 (ClO 4 ) 2 (OH) 2 -(C 10 H 8 N 2 ) 2 ], the Cu II ion is coordinated in the form of a Jahn-Teller distorted octahedron by two bipyridine N atoms, two perchlorate O atoms and two hydroxide O atoms, and displays a distorted octahedral geometry. The molecule belongs to the symmetry point group C 2h . The Cu II ion is located on a twofold rotation axis and the hydroxide and perchlorate ligands are located on a mirror plane. Within the dinuclear molecule, the CuÁ Á ÁCu separation is 2.8614 (7) Å . The crystal structure exhibits O-HÁ Á ÁO, C-HÁ Á ÁO and -[centroid-centroid distance = 3.5374 (13) Å ] interactions.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
Copper complexes have received much attention because of their interesting interactions with biological ligands to generate stable mixed coordinated complexes, which play a key role in life processes such as enzymatic catalysis, storage and conveyance of the matter, transfer of copper ions (Müller et al., 2003;Lo et al., 2000). In the molecular structure of the title compound ( Fig. 1), the bond distances Cu1-N1 = 1.9865 (16) Å and Cu1-O1 = 1.9097 (13) Å agree with the reported similar structures (Shaikh et al., 2012;Wang et al., 2010). Each Cu (II) cation is hexa-coordinated with two N atoms of bipyridine, two hydroxyl group O atoms bridging the copper cations and two O atoms of perchlorate anions, showing distorted octahedral environment (Fig. 1). The molecule belongs to the symmetry point group C 2h . The two copper anions are separated by a distance of 2.8614 (7) Å, indicating a strong Cu II ···Cu II interaction which is comparable with the Cu II ···Cu II distance in the reported structure (Li et al., 2009).

Experimental
To a solution of 2,2′-bipyridine (0.25 g, 1.60 mM) in 10 mL methanol, Cu(ClO 4 ) 2 . 6H 2 O (0.59 g, 1.60 mM) in 10 mL of methanol, was slowly added dropwise with constant stirring. The mixture was stirred well at room temperature for about 3 h, the formed blue solution was then concentrated to one third of its volume, washed well (with water, methanol and ether) and dried under vacuum. The complex was then recrystallized in ethanol by the slow evaporation method to obtain X-ray quality single crystals of the complex, which appeared gradually after several days.

Refinement
The H atom of the hydroxyl O atom was located in a difference Fourier map and refined with the O1-H1 distance restrained to 0.82 (1)Å. All other H atoms were positioned geometrically and refined using riding model, with C-H = 0.93 Å and U iso (H) = 1.2U eq (C).
One reflection (1 1 0) was omitted from the final cycles of refinement owing to poor agreement.

Computing details
Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004  The molecular structure of the title compound, with atom labels and 30% probability displacement ellipsoids for non-H atoms. Symmetry codes : (a) -2-x, y, -1-z; (b) -2-x, -y, -1-z; (c) x, -y, z.  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 > 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.  (9) 0.0312 (9) −0.0004 (7) 0.0143 (7) 0.0011 (7)