Copper and zinc complexes with 2,3-pyridinedicarboxylic acid or 2,3-pyrazinedicarboxylic acid: Polymer structures and magnetic properties

Structure of a dinuclear cadmium complex with 2,2'-bi-pyridine, monodentate nitrate and 3-carb-oxy-6-methyl-pyridine-2-carboxyl-ate ligands: intra-molecular carbon-yl(lone pair)⋯π(ring) and nitrate(π)⋯π(ring) inter-actions

The centrosymmetric dinuclear complex bis-(μ-3-carb-oxy-6-methyl-pyridine-2-carboxyl-ato)-κ(3) N,O (2):O (2);κ(3) O (2):N,O (2)-bis-[(2,2'-bi-pyridine-κ(2) N,N')(nitrato-κO)cadmium] methanol monosolvate, [Cd2(C8H6NO4)2(NO3)2(C10H8N2)2]·CH3OH, was isolated as colourless crystals from the reaction of Cd(NO3)2·4H2O, 6-methyl-pyridine-2,3-di-carb-oxy-lic acid (mepydcH2) and 2,2'-bi-pyridine in methanol. The asymmetric unit consists of a Cd(II) cation bound to a μ-κ(3) N,O (2):O (2)-mepydcH(-) anion, an N,N'-bidentate 2,2'-bi-pyridine group and an O-mono-dentate nitrate anion, and is completed with a methanol solvent mol-ecule at half-occupancy. The Cd complex unit is linked to its centrosymmetric image through a bridging mepydcH(-) carboxyl-ate O atom to complete the dinuclear complex mol-ecule. Despite a significant variation in the coordination angles, indicating a considerable departure from octa-hedral coordination geometry about the Cd(II) atom, the Cd-O and Cd-N distances in this complex are surprisingly similar. The crystal structure consists of O-H⋯O hydrogen-bonded chains parallel to a, further bound by C-H⋯O contacts along b to form planar two-dimensional arrays parallel to (001). The juxtaposed planes form inter-stitial columnar voids that are filled by the methanol solvent mol-ecules. These in turn inter-act with the complex mol-ecules to further stabilize the structure. A search in the literature showed that complexes with the mepydcH(-) ligand are rare and complexes reported previously with this ligand do not adopt the μ-κ(3) coordination mode found in the title compound.

Hexaaqua-zinc(II) bis-[tris-(3-carb-oxy-pyridine-2-carboxyl-ato)zincate(II)]

The title compound, [Zn(H(2)O)(6)][Zn(C(7)H(4)NO(4))(3)](2), consists of two [Zn(py-2,3-dcH)(3)](-) anions (py-2,3-dcH is 3-carboxy-pyridine-2-carboxylate) and one [Zn(H(2)O)(6)](2+) cation. The anion is a six-coordinate complex located on a threefold rotation axis with a slightly distorted octa-hedral geometry around Zn(2+) ion. The cation is also six-coordinate with an octa-hedral geometry around the Zn atom, located at a axis. Non-covalent inter-actions such as π-π stacking [centroid-centroid distance = 3.828 (4)Å] and O-H⋯O hydrogen bonds play important roles in stabilizing the supra-molecular structure.

Poly[[(N,N-dimethyl-formamide-κO)(μ(3)-pyrazine-2,3-dicarboxyl-ato-κN,O:O:O)copper(II)] monohydrate]

In the title compound, {[Cu(C(6)H(2)N(2)O(4))(C(3)H(7)NO)]·H(2)O}(n), the Cu(II) atom is coordinated by an N,O-bidentate pyrazine-2,3-dicarboxyl-ate (pzdc) dianion, two O atoms from two other pzdc anions and one O atom from the dimethlyformamide ligand, forming a distorted square-pyramidal CuNO(4) geometry. The polymeric character of the structure is established by the formation of layers parallel to (100) via bridging pzdc ligands. O-H⋯O hydrogen bonding between water mol-ecules and uncoordinated carboxyl-ate O atoms leads to additional stabilization of the structure.