title: 2-Amino-pyridinium 2-meth-oxy-carbonyl-4,6-dinitro-phenolate.
abstract: In the title mol-ecular salt, C(5)H(7)N(2) (+)·C(8)H(5)N(2)O(7) (-), the 2-amino-pyridinium cation is essentially planar, with a maximium deviation of 0.015 (1) Å, while the 2-meth-oxy-carbonyl-4,6-dinitro-phenolate anion is slightly twisted away from planarity, with a maximium deviation of 0.187 (1) Å. Deprotonation of the hy-droxy O atom was observed. The cation and anion are connected by four bifurcated N-H⋯(O,O) hydrogen bonds, forming a mol-ecular proton-transfer adduct. The dihedral angle between the pyridinium ring in the cation and the benzene ring in the anion is 3.65 (6)°. Every adduct connects to six neighboring adducts by N-H⋯O and C-H⋯O hydrogen bonds, yielding extended layers parallel to the bc plane. There is a weak π-π inter-action between the benzene rings of two neighboring anions; the inter-planar spacing and the centroid-centroid separation are 3.309 (1) and 3.69 (1) Å, respectively.
authors.affiliation: College of Materials Science & Engineering, Huaqiao University, Xiamen 361021,  People's Republic of China.
authors.forename: Dong-Liang
authors.initials: DL
authors.lastname: Wu
authors.forename: Zi-Jing
authors.initials: ZJ
authors.lastname: Xiao