Abstract

The crystal structures of the proton-transfer compounds of 3,5-dinitrosalicylic acid (dnsa) with ammonia (two polymorphs) and a series of common aliphatic amines (methylamine, triethylamine, hexamethylenetetramine and ethylenediamine) have been determined and the hydrogen-bonding associations in each analysed. The compounds are [(NH₄)⁺(dnsa)^-] (1A, 1B), [(CH₃NH₃)⁺(dnsa)^-] (2), [{(C₂H₅)₃NH}⁺(dnsa)^-] (3), [(C₆H₁₂ N₄H)⁺(dnsa)^-] (4) and [{(CH₂ NH₃) ₂}²⁺(dnsa)^2-·H₂O] (5). It is of interest that with hydrate (5) the phenolic proton of dnsa is also lost on reaction, giving a rare dianionic species. In all compounds, protonation of the amino group of the Lewis base occurs, with subsequent hydrogen bonding via this and other hydrogens variously to the carboxylic, nitro and phenolic oxygens of dnsa, and in the case of (5), the lattice water. The result is the formation of simple linear associations with the tertiary amines, or network polymers with the less-substituted examples. Short intramolecular hydrogen bonds between the phenolic group and the carboxylate group are found in all compounds except (5), with the proton localized on the carboxylate oxygen rather than on the phenolic oxygen, but in the case of (3), delocalized within the hydrogen bond.