The title compound, C(5)H(6)N(3)O(2) (+)·ClO(4) (-), is comprised of discrete perchlorate anions and 2-amino-3-nitro-pyridinium cations. The anion has a typical tetra-hedral geometry while the cation presents a nearly planar [maximum deviation = 0.007 (8) Å] pyridinium ring. Undulating [C(5)H(6)N(3)O(2) (+)](n) chains extending along the c-axis direction are linked via N-H⋯O hydrogen bonds. The...

In the crystal structure of the title compound, C(6)H(7)N(2)O(2) (+)·NO(3) (-), the cations are linked via C-H⋯O hydrogen bonds, forming infinite chains running along the b axis. These chains are further linked through N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds to the nitrate anions, forming well-separated infinite planar layers parallel to (001).