Crystal structures of the 1:1 salts of 2-amino-4-nitro­benzoate with each of (2-hy­droxy­eth­yl)di­methyl­aza­nium, tert-but­yl(2-hy­droxy­eth­yl)aza­nium and 1,3-dihy­droxy-2-(hy­droxy­meth­yl)propan-2-aminium

The crystal and mol­ecular structures of the title mol­ecular salts, C(4)H(12)NO(+)·C(7)H(5)N(2)O(4) (−), (I), C(6)H(16)NO(+)·C(7)H(5)N(2)O(4) (−), (II), and C(4)H(12)NO(3) (+)·C(7)H(5)N(2)O(4) (−), (III), are described. The common feature of these salts is the presence of the 2-amino-4-nitro­benzoate anion, which exhibit non-chemically significant variations in the conformational relationships between the carboxyl­ate and nitro groups, and between these and the benzene rings they are connected to. The number of ammonium-N—H H atoms in the cations increases from one to three in (I) to (III), respectively, and this variation significantly influences the supra­molecular aggregation patterns in the respective crystals. Thus, a linear supra­molecular chain along [100] sustained by charge-assisted tertiary-ammonium-N—H⋯O(carboxyl­ate), hy­droxy-O—H⋯O(carboxyl­ate) and amino-N—H⋯O(carboxyl­ate) hydrogen-bonds is apparent in the crystal of (I). Chains are connected into a three-dimensional architecture by methyl-C—H⋯O(hy­droxy) and π–π inter­actions, the latter between benzene rings [inter-centroid separation = 3.5796 (10) Å]. In the crystal of (II), a supra­molecular tube propagating along [901] arises as a result of charge-assisted secondary-ammonium-N—H⋯O(carboxyl­ate) and hy­droxy-O—H⋯O(carboxyl­ate) hydrogen-bonding. These are connected by methyl­ene- and methyl-C—H⋯O(nitro) and π–π stacking between benzene rings [inter-centroid separation = 3.5226 (10) Å]. Finally, double-layers parallel to (100) sustained by charge-assisted ammonium-N—H⋯O(carboxyl­ate), ammonium-N—H⋯O(hy­droxy) and hy­droxy-O—H⋯O(carboxyl­ate) hydrogen-bonds are apparent in the crystal of (III). These are connected in a three-dimensional architecture by amine-N—H⋯O(nitro) hydrogen-bonds.