Crystal structure of poly[bis(μ-nicotinamide-κ2N1:O)bis(μ-4-nitrobenzoato-κ2O1:O1′)zinc]

The asymmetric unit of the title coordination polymer, [Zn(C7H4NO4)2(C6H6N2O)2]n, contains two 4-nitrobenzoate (NB) anions and two nicotinamide (NA) ligands. The ZnII atom has a slightly distorted octahedral coordination sphere. In the equatorial plane, it is coordinated by three carboxylate O atoms of the NB anions and one O atom of one of the two NA ligands. The axial positions are occupied by the pyridine N atoms of the two NA ligands. In the two NB anions, the carboxylate groups are twisted away from the attached benzene rings by 13.8 (2) and 13.4 (2)°, while the benzene rings are oriented at a dihedral angle of 11.5 (2)°. The dihedral angle between the NA rings is 10.3 (1)°. Only one of the two NB anions and one of the two NA ligands bridge adjacent ZnII ions through eight- and twelve-membered rings, respectively, forming polymeric chains running along the a-axis direction. In the crystal, N—H ... O hydrogen bonds link adjacent chains, enclosing R(16), R22(20) and R66(16) ring motifs, forming layers parallel to (01-1). The layers are linked via a number of C—H...O hydrogen bonds, forming a three-dimensional network.