catena-Poly[[di­aqua­bis­(4-formyl­benzoato-κO¹)copper(II)]-μ-pyrazine-κ²N: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 octa­hedral coordination sphere. In the equatorial plane, it is coordinated by two carboxyl­ate O atoms of two symmetry-related monodentate formyl­benzoate anions and by two N atoms of the bridging pyrazine ligand, which is bis­ected by the twofold rotation axis. The axial positions are occupied by two O atoms of the coordinating water mol­ecules. In the formyl­benzoate anion, the carboxyl­ate 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 intra­molecular O—H...O hydrogen bonds link the water mol­ecules to the carboxyl­ate O atoms. In the crystal, O—H_water...O_water hydrogen bonds link adjacent chains into layers parallel to the bc plane. The layers are linked via C—H_pyrazine...O_form­yl hydrogen bonds, forming a three-dimensional network. There are also weak C—H...π inter­actions present.

catena-Poly[[aqua­bis­(4-formyl­benzoato-κ²O¹,O^1′)cadmium]-μ-pyrazine-κ²N:N′]

The polymeric title compound, [Cd(C₈H₅O₃)₂(C₄H₄N₂)(H₂O)]_n, contains two 4-formyl­benzoate (FB) anions, one pyrazine mol­ecule and one coordinating water mol­ecule; the FB anions act as bidentate ligands. The O atom, the aldehyde H atom and the benzene ring of one of the FB anions are disordered over two positions. The O atoms were freely refined [refined occupancy ratio 0.79 (2):0.21 (2)], while the aldehyde H atoms and the benzene ring atoms were refined with fixed occupancy ratios of 0.8:0.2 and 0.5:0.5, respectively. In the ordered FB anion, the carboxyl­ate group is twisted away from the attached benzene ring (A) by 22.7 (8)°. In the disordered FB anion, the corresponding angles are 15.6 (10) and 11.4 (11)° for rings B and B′, respectively. Benzene rings A and B are oriented at a dihedral angle of 24.2 (7), A and B′ at 43.0 (8)°. The pyrazine ring makes dihedral angles of 67.5 (4), 89.6 (7) and 86.2 (7)°, respectively, with benzene rings A, B and B′. The pyrazine ligands bridge the Cd^II cations, forming polymeric chains running along the b-axis direction. In the crystal, O—H_water ... O_{carboxyl­ate} hydrogen bonds link adjacent chains into layers parallel to the bc plane. These layers are linked via C—H_pyrazine ... O_form­yl hydrogen bonds, forming a three-dimensional network. π–π interactions [centroid–centroid distances = 3.870 (11)–3.951 (5) Å] further stabilize the crystal structure. There is also a weak C—H...π inter­action present.

catena-Poly[[di­aqua­bis­(4-formyl­benzo­ato-κO¹)nickel(II)]-μ-pyrazine-κ²N:N′]

In the title polymeric compound, [Ni(C₈H₅O₃)₂(C₄H₄N₂)(H₂O)₂]_n, the Ni^II atom is located on a twofold rotation axis and has a slightly distorted octa­hedral coordination sphere. In the equatorial plane, it is coordinated by two carboxyl­ate O atoms of two symmetry-related monodentate formyl­benzoate anions and by two N atoms of the bridging pyrazine ligand, which is bis­ected by the twofold rotation axis. The axial positions are occupied by two O atoms of the coordinating water mol­ecules. In the formyl­benzoate anion, the carboxyl­ate group is twisted away from the attached benzene ring by 7.0 (6)°, while the benzene and pyrazine rings are oriented at a dihedral angle of 66.2 (3)°. The pyrazine ligands bridge the Ni^II cations, forming polymeric chains running along the b-axis direction. Intra­molecular O—H...O hydrogen bonds link the water ligands to the carboxyl­ate O atoms. In the crystal, water–water O—H...O hydrogen bonds link adjacent chains into layers parallel to the bc plane. Pyrazine–formyl C—H...O hydrogen bonds link the layers, forming a three-dimensional network. There are also weak C—H...π inter­actions present. The title compound is isotypic with the copper(II) complex [Çelik et al. (2014a). Acta Cryst. E70, m4–m5].