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 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 ²₂(20) and R⁶₆(16) ring motifs, forming layers parallel to (011). The layers are linked via a number of C - H⋯O hydrogen bonds, forming a three-dimensional network.