2,2,4-Trimethyl-7-nitro-2,3-dihydro-1H-1,5-benzodiazepin-5-ium perchlorate.

In the title mol-ecular salt, C(12)H(16)N(3)O(2) (+)·ClO(4) (-), the nitro group is close to being coplanar with the benzene ring [dihedral angle = 8.1 (3)°]. The seven-membered ring has a maximum deviation of 0.502 (3) Å at the C atom between the dimethyl- and methyl-substituted C atoms. In the crystal, the components are linked into infinite sheets lying parallel to the bc plane by N-H⋯O and C-H⋯O hydrogen bonds. A short O⋯N contact of 2.896 (4) Å occurs within the sheets and a short O⋯O contact of 2.608 (4) Å occurs between the sheets.