Oxalic acid-pyridine-4-carbonitrile (1/2).
In the title compound, 2C(6)H(4)N(2)·C(2)H(2)O(4), the oxalic acid mol-ecule lies about an inversion center. The pyridine ring of the pyridine-4-carbonitrile mol-ecule is almost planar, the largest deviation from the least-squares plane being 0.006 (1) Å; the nitrile N atom deviates from this plane by 0.114 (1) Å. In the crystal, the oxalic acid mol-ecules and the pyridine-4-carbonitrile mol-ecules form stacks. Neighboring mol-ecules within the stacks are related by translation in the a direction, with inter-planar distances of 3.183 (1) and 3.331 (2) Å, respectively. Each oxalic acid mol-ecule forms strong O-H⋯N hydrogen bonds with two mol-ecules of pyridine-4-carbonitrile. Besides this, there are also weak C-H⋯O inter-actions.
College of Chemistry and Chemical Engineering, Southeast University, Nanjing 210096,  People's Republic of China.
Wen-Ni
WN
Zheng