catena-Poly[[di-aqua-bis-(4-formyl-benzoato-κO (1))copper(II)]-μ-pyrazine-κ(2) N:N'].

In the title polymeric compound, [Cu(C8H5O3)2(C4H4N2)(H2O)2] n , the Cu(II) atom is located on a twofold rotation axis and has a slightly distorted octa-hedral coordination sphere. In the equatorial plane, it is coordinated by two carboxyl-ate O atoms of two symmetry-related monodentate formyl-benzoate anions and by two N atoms of the bridging pyrazine ligand, which is bis-ected by the twofold rotation axis. The axial positions are occupied by two O atoms of the coordinating water mol-ecules. In the formyl-benzoate anion, the carboxyl-ate group is twisted away from the attached benzene ring by 6.2 (2)°, while the benzene and pyrazine rings are oriented at a dihedral angle of 68.91 (8)°. The pyrazine ligands bridge the Cu(II) cations, forming polymeric chains running along the b-axis direction. Strong intra-molecular O-H⋯O hydrogen bonds link the water mol-ecules to the carboxyl-ate O atoms. In the crystal, O-Hwater⋯Owater hydrogen bonds link adjacent chains into layers parallel to the bc plane. The layers are linked via C-Hpyrazine⋯Oform-yl hydrogen bonds, forming a three-dimensional network. There are also weak C-H⋯π inter-actions present.