2-Amino-5-chloropyridinium 4-aminobenzoate

In the title molecular salt, C5H6ClN2 +·C7H6NO2 −, the cations and anions are connected by cation-to-anion and anion-to-anion N—H⋯O hydrogen bonds into a three-dimensional network. The dihedral angle between the ring and the CO2 group in the anion is 7.14 (7)°.

In the title molecular salt, C 5 H 6 ClN 2 + ÁC 7 H 6 NO 2 À , the cations and anions are connected by cation-to-anion and anion-toanion N-HÁ Á ÁO hydrogen bonds into a three-dimensional network. The dihedral angle between the ring and the CO 2 group in the anion is 7.14 (7) .
The ORTEP plot of the molecule is shown in Fig.1. The structure can be described as segregated (C 5 H 6 ClN 2 ) + .
(C 7 H 6 NO 2 )groups and connected via N-H···O hydrogen bonds (Blessing, 1986;Brown, 1976). The dihedral angle between the chloropyridinium ring and aminobenzoate group is 51.5 (7)°. The external bond angle [N1-C2-N2=] 118.1 (1)° at the attached amino group in pyridinium moiety is slightly widened due to the hydrogen bond formation between the ionic groups.
A dimer formation occurs through N-H···O hydrogen bonds between the symmetry related molecules (Fig.2). N-H···O type of hydrogen bonds stabilize the molecules in the unit cell.

Experimental
Methanol solutions of 2-amino-5-chloropyridine (64.28 mg, Aldrich) and 4-aminobenzoic acid (68.57 mg, Merck) were mixed together and stirred for about 1 h to get a homogeneous mixture. The resulting solution was allowed to evaporate at 303 K slowly in a water bath which has a temperature accuracy of ± 0.01°C at ambient atmosphere. Brown colour crystals with developed morphology of title compound were obtained after 12 days.

Refinement
H atoms bonded to aromatic C and N atoms were positioned geometrically (N-H = 0.86 Å and C-H = 0.93 Å) and allowed to ride on their parent atoms,with U iso (H) = 1.2U eq (C,N). The H atoms of the two NH 2 groups were freely refined.  The molecular structure of the title compound, showing the atomic numbering and displacement ellipsoids drawn at 30% probability level.

Figure 2
The crystal packing of the molecules viewed down a axis. 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.