Crystal structure of poly[bis­(μ-nicotinamide-κ(2) N (1):O)bis­(μ-4-nitro­benzoato-κ(2) O (1):O (1′))zinc]

The asymmetric unit of the title coordination polymer, [Zn(C(7)H(4)NO(4))(2)(C(6)H(6)N(2)O)(2)](n), contains two 4-nitro­benzoate (NB) anions and two nicotinamide (NA) ligands. The Zn(II) 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 Zn(II) 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), R (2) (2)(20) and R (6) (6)(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.