title: 2-Amino-5-methyl-pyridinium 6-oxo-1,6-dihydro-pyridine-2-carboxyl-ate.
abstract: The anion of the title salt, C(6)H(9)N(2) (+)·C(6)H(4)NO(3) (-), undergoes an enol-to-keto tautomerism during the crystallization. In the crystal structure, the cation and anion are held together by a relatively short N-H⋯O hydrogen bond, and the two anions are further connected to each other by a pair of N-H⋯O hydrogen bonds with an R(2) (2)(8) ring motif, thus forming a centrosymmetric 2 + 2 aggregate. The aggregates are further linked through weak N-H⋯O and C-H⋯O hydrogen bonds, resulting a three-dimensional network.
authors.affiliation: School of Physics, Universiti Sains Malaysia, 11800 USM, Penang,  Malaysia.
authors.forename: Kaliyaperumal
authors.initials: K
authors.lastname: Thanigaimani
authors.forename: Abbas
authors.initials: A
authors.lastname: Farhadikoutenaei
authors.forename: Nuridayanti Che
authors.initials: NC
authors.lastname: Khalib
authors.forename: Suhana
authors.initials: S
authors.lastname: Arshad
authors.forename: Ibrahim Abdul
authors.initials: IA
authors.lastname: Razak