catena-Poly[[aquabis[N-(pyridin-3-yl)isonicotinamide-κN 1]copper(II)]-μ-fumarato-κ2 O 1:O 4]

In the title compound, [Cu(C4H2O4)(C11H9N3O)2(H2O)]n, CuII ions on crystallographic twofold rotation axes are coordinated in a square pyramidal environment by two trans O atoms belonging to two monodentate fumarate anions, two trans isonicotinamide pyridyl N-donor atoms from monodentate, pendant 3-pyridylisonicotinamide (3-pina) ligands, and one apical aqua ligand, also sited on the crystallographic twofold rotation axis. The exobidentate fumarate ligands form [Cu(fumarate)(3-pina)2(H2O)]n coordination polymer chains that are arranged parallel to [001]. In the crystal, these polymeric chains are anchored into supramolecular layers parallel to (100) by O—H⋯O hydrogen bonds between aqua ligands and unligating fumarate O atoms, and N—H⋯O(=C) hydrogen bonds between 3-pina ligands. In turn, the layers aggregate by weak C—H⋯N and C—H⋯O hydrogen bonds, affording a three-dimensional network.

The asymmetric unit of the title compound contains a divalent copper atom and an aqua ligand on a crystallographic twofold rotation axis, a 3-pina ligand, and one half of a fumarate ligand whose centroid rests on a crystallographic inversion centre. The copper atom is square pyramidally coordinated ( Fig. 1), with the basal plane containing trans isonicotinamide pyridyl N atom donors from two 3-pina ligands and trans O atom donors from monodentate carboxylate groups belonging to two fumarate ligands. The aqua ligand is located in the apical position.
The Cu atoms are linked by exobidentate, bis(monodentate) fumarate ligands to form [Cu(fumarate)(3-pina) 2 (H 2 O)] n coordination polymer chains that are oriented parallel to [0 0 1] (Fig. 2). Each individual chain is anchored to two others via O-H···O pairwise hydrogen bonding (Table 1) between aqua ligands and unligated fumarate O atoms, thereby constructing supramolecular two-dimensional layers arranged parallel to the bc crystal planes (Fig. 3). The stability of the layer motifs is enhanced by N-H···O hydrogen bonding between amide groups of adjacent 3-pina ligands (Fig. 4). In turn the layers stack along [1 0 0] in an AAA pattern via C-H···N interactions mediated by unligated 3-pyridyl N atoms belonging to the pendant 3-pina ligands (Fig. 5), thus forming the three-dimensional structure of the title compound which is also stabilized by weak C-H···O interactions.

Refinement
All H atoms bound to C atoms were placed in calculated positions, with C-H = 0.95 Å, and refined in riding mode with U iso = 1.2U eq (C). The H atom within the amide group of the 3-pina ligand was found in a difference Fourier map, restrained with N-H = 0.90 (2) Å and refined with U iso = 1.2U eq (N). The H atoms within the aqua ligand were found in a difference Fourier map, restrained with O-H = 0.85 (2) Å and refined with U iso = 1.2U eq (O).

Figure 1
The coordination environment of the title compound, showing 50% probability ellipsoids and atom numbering scheme.
Hydrogen atom positions are shown as grey sticks. Color codes: dark blue Cu, red O, light blue N, black C, pink H.

catena-Poly[[aquabis[N-(pyridin-3-yl)isonicotinamide-κN 1 ]copper(II)]-µ-fumarato-κ 2 O 1 :O 4 ]
Crystal data 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.