Two-component molecular crystals composed of chloronitrobenzoic acids and 4-aminopyridine

The crystal structures of the four isomeric organic salts 4-aminopyridinium 2-chloro-4-nitrobenzoate, (I), 4-aminopyridinium 2-chloro-5-nitrobenzoate, (II), 4-aminopyridinium 5-chloro-2-nitrobenzoate, (III), and 4-aminopyridinium 4-chloro-2-nitrobenzoate, (IV), all C(5)H(7)N(2)+ x C(7)H(3)ClNO(4)-, are presented. Compound (I) has one intramolecular hydrogen bond, one intermolecular C-H* * *O hydrogen bond and pi-pi-stacking interactions. Compound (II) has N-H* * *O, C-H* * *O and C-H* * *Cl hydrogen bonds, and Cl* * *O-C electrostatic interactions. Compound (III) has N-H* * *O and C-H* * *O hydrogen bonds. Compound (IV) has a pi-pi-stacking interaction, but no C-H* * *O hydrogen bonds.