3-(2-Chloro-ethyl)-2-methyl-4-oxo-4H-pyrido[1,2-a]pyrimidinium 2,4,6-trinitro-phenolate.

In the cation of the title salt, C(11)H(12)ClN(2)O(+)·C(6)H(2)N(3)O(7) (-), the chloro-ethyl side chain is in a syn conformation, nearly orthogonal to the pyrimidine ring, with a dihedral angle of 78.9 (6)° between the plane of the chloro-ethyl chain and the pyrimidine ring. The dihedral angle between the fused rings is 4.3 (3)°. In the picrate anion, the benzene mean plane makes dihedral angles of 26.7 (1), 33.6 (2) and 5.3 (6)° with the two o-NO(2) groups and the p-NO(2) group, respectively. Extensive hydrogen-bond inter-actions occur between the cation-anion pair which help to establish the crystal packing. A three-center O⋯(H,H)-(N,C) acceptor hydrogen bond is observed between the phenolate O atom of the picrate anion and the amine and methyl groups of the cation. An N-H⋯(O,O) bifurcated hydrogen bond is observed between the amine group and two O atoms from the phenolate and o-NO(2) groups.