catena-Poly[[[triaquacopper(II)]-μ2-pyrazine-2,3-dicarboxylato] monohydrate]

The Cu atom in the title complex, {[Cu(C6H2N2O4)(H2O)3]·H2O}n or {[Cu(L)(H2O)3]·H2O}n (L is pyrazine-2,3-dicarboxylate), displays octahedral coordination formed by the ligand L and three coordinated water molecules. The ligand L is tridentate, with one N atom of the pyrazine ring and one O atom of one carboxylate group forming a chelate ring, whereas one O atom from the second carboxylate group is coordinated to another Cu atom. The ligand L links molecules to form an infinite chain parallel to the [101] direction. The chains are further linked through O—H⋯O and O—H⋯N hydrogen bonds involving the water molecules to build up a three-dimensional network.

The Cu atom in the title complex, {[Cu(C 6 H 2 N 2 O 4 )(H 2 O) 3 ]Á-H 2 O} n or {[Cu(L)(H 2 O) 3 ]ÁH 2 O} n (L is pyrazine-2,3-dicarboxylate), displays octahedral coordination formed by the ligand L and three coordinated water molecules. The ligand L is tridentate, with one N atom of the pyrazine ring and one O atom of one carboxylate group forming a chelate ring, whereas one O atom from the second carboxylate group is coordinated to another Cu atom. The ligand L links molecules to form an infinite chain parallel to the [101] direction. The chains are further linked through O-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds involving the water molecules to build up a threedimensional network.
The Cu II ion displays octahedral coordination formed by the one L ligand and three coordinated water molecules. The ligand L is tridentate with the N atom of the pyridine ring and one O atom of one carboxylate forming a chelate ring whereas one O atom from the second carboxylate is coordinated to another Cu atom (Fig. 1). Then the ligand L links molecules to form an infinite chain parallel to the [1 O 1] direction. The chains are further linked through O-H···O and O-H···N involving the water molecules to build up a three dimensionnal network (Table 1).

S2. Experimental
L (0.031 g, 0.018 mmol), CuSO4 (0.018 g, 0.016 mmol) and NaOH(0.048 mmol,0.12 mmol), were added in a mixed solvent of ethanol, the mixture was heated for three hours under reflux. during the process stirring and influx were required. The resultant was then filtered to give a pure solution which was infiltrated by diethyl ether freely in a closed vessel, two weeks later some single crystals of the size suitable for X-Ray diffraction analysis.

S3. Refinement
All H atoms attached to C atoms were fixed geometrically and treated as riding with C-H = 0.93 Å and U iso (H) = 1.2U eq (C). H atoms of water molecule were located in difference Fourier maps and included in the subsequent refinement  View of compound (I) with the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms have been omitted for clarity. [Symmetry codes: (i) x -1/2, 1/2 -y, z -1/2; (ii) 1/2 + x, 1/2 -y, 1/2 + z]

catena-Poly[[[triaquacopper(II)]-µ 2 -pyrazine-2,3-dicarboxylato] monohydrate]
Crystal data [Cu(C 6  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.67 e Å −3 Δρ min = −1.08 e Å −3 Absolute structure: Flack (1983), 758 Friedel pairs Absolute structure parameter: −0.04 (2) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.