2,3-Diaminopyridinium 4-methoxyquinoline-2-carboxylate

In the 4-methoxyquinoline-2-carboxylate anion of the title salt, C5H8N3 +·C11H8NO3 −, the dihedral angle between the quinoline ring system and the carboxylate group is 16.54 (15)°. In the crystal, the cations and anions are linked via N—H⋯O and N—H⋯N hydrogen bonds, forming a centrosymmetric 2 + 2 aggregate with R 2 2(9) and R 4 2(8) ring motifs. These units are further connected via N—H⋯O hydrogen bonds into a layer parallel to the bc plane. The crystal structure is also stabilized by weak C—H⋯O hydrogen bonds and π–π interactions between pyridine rings [centroid–centroid distance = 3.5886 (8) Å] and between pyridine and benzene rings [centroid–centroid distance = 3.6328 (8) Å].


Experimental
Hot methanol solutions (20 ml) of 2,3-diaminopyrimidine (27 mg, Aldrich) and 4-Methoxy-2-quinolinecarboxylic acid (50 mg, Merck) were mixed and warmed over a heating magnetic stirrer hotplate for a few minutes. The resulting solution was allowed to cool slowly at room temperature and crystals of the title compound (I) appeared after a few days.

Refinement
N-bound H Atoms were located in a difference Fourier maps and refined freely [N-H = 0.88 (2)-0.936 (18) Å]. The remaining hydrogen atoms were positioned (C-H = 0.95 and 0.98 Å) and refined using a riding model, with U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C). A rotating-group model was used for the methyl group.

Figure 1
The molecular structure of the title compound with atom labels with 50% probability displacement ellipsoids.

Figure 2
The crystal packing of the title compound. The H atoms not involved in the intermolecular interactions (dashed lines) have been omitted for clarity.

2,3-Diaminopyridinium 4-methoxyquinoline-2-carboxylate
Crystal data Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.