catena-Poly[[[tetraaquacopper(II)]-μ-4,4′-bipyridyl-κ2 N:N′] tetrafluoridosuccinate tetrahydrate]

In the title compound, {[Cu(C10H8N2)(H2O)4](C4F4O4)·4H2O}n, the CuII atom adopts an elongated octahedral geometry because of the Jahn–Teller effect. Both cation and anion have crystallographic twofold rotation symmetry with the twofold axes passing through the Cu and N atoms and through the midpoint of the central C—C bond. The 4,4′-bipyridyl ligand links the CuII atoms into a linear chain along the b axis. O—H⋯O hydrogen-bonding interactions between the cationic chains and the tetrafluoridosuccinate anions and the free water molecules generate a three-dimensional supramolecular network.

In the title compound, {[Cu(C 10 H 8 N 2 )(H 2 O) 4 ](C 4 F 4 O 4 )Á-4H 2 O} n , the Cu II atom adopts an elongated octahedral geometry because of the Jahn-Teller effect. Both cation and anion have crystallographic twofold rotation symmetry with the twofold axes passing through the Cu and N atoms and through the midpoint of the central C-C bond. The 4,4 0bipyridyl ligand links the Cu II atoms into a linear chain along the b axis. O-HÁ Á ÁO hydrogen-bonding interactions between the cationic chains and the tetrafluoridosuccinate anions and the free water molecules generate a three-dimensional supramolecular network.
Recently, the construction of hybrid framework materials using perfluorinated ligands has attracted much attention based on reports of interesting gas storage properties for such materials containing porous surfaces with exposed fluorine atoms (Yang et al., 2007). Tetrafluorosuccinic acid, as a perfluorinated dicarboxylate ligand, is an excellent candidate for the construction of hybrid frameworks with diverse structures (Hulvey et al., 2009) and with which the title compound, Cu(C 10 H 8 N 2 )(H 2 O) 4 .C 4 F 4 O 4 .4H 2 O, was hydrothermally prepared from Cu(NO 3 ) 2 .3H 2 O and 4,4′-bipyridyl as coligand.
Both cation and anion have crystallographic 2-fold rotation symmetry with the 2-fold axes passing through Cu1, N1 and N2 and through the midpoint of the central C-C bond. The metal adopts a tetragonally elongated octahedral geometry because of the Jahn-Teller effect. The O4 atom occupies the elongated vertex with a Cu1-O4 distance of 2.462 (2) Å.
The O1, N1 and N2 atoms occupy the equatorial plane with a Cu1-O1 distance of 1.976 (2) Å and Cu1-N1 and Cu1-N2 distances of 2.019 (3) and 2.027 (3) Å respectively ( Figure 1). Adjacent Cu II centers are bridged by 4,4′-bipy ligands to generate a one-dimensional linear chain structure parallel to the b axis. As shown in Figure 2 and Table 1, O-H···O hydrogen-bonding interactions between the cationic one-dimensional chains and the tetrafluorosuccinate anions and the free water molecules generate a three-dimensional supramolecular network.

Experimental
A mixture of tetrafluorosuccinic acid (18.7 mg), 4,4′-bipyridyl (24.7 mg) and Cu(NO 3 ) 2 .3H 2 O (15.2 mg) was dissolved in water (8 ml) and stirred for 0.5 h at room temperature. It was then sealed in a 25 ml Teflon-lined stainless steel reactor and heated at 393 K for 48 h. Blue crystals suitable for X-ray analysis were obtained after cooling the solution to room temperature. The yield is ca 70% based on Cu 2+ .

Refinement
H atoms on O were located in difference maps and the O-H distances adjusted to 0.82 Å while H atoms on C were positioned geometrically with C-H = 0.93 Å. All were allowed to ride on their respective parent atoms with U iso (H) = 1.2 Ueq(C or O).

Figure 1
ORTEP drawing showing the coordination sphere of the Cu 2+ center in the title compound with 50% probability displacement ellipsoids. Symmetry codes i: 1-x,y,1.5-z; ii: x,1+y,z; iii: x,1-y,z; iv: 0.5-z,0.5-y,1-z.  View down the c axis of the three-dimensional hydrogen bonding supramolecular network of the title compound.

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.