5-nitrosalicylic acid and its proton-transfer compounds with aliphatic Lewis bases

The crystal structures of the proton- transfer compounds of 5- nitrosalicylic acid ( 5- nsa) with morpholine ( morph), hexamethylenetetramine ( hmt), and ethylenediamine ( en) have been determined and their solid- state packing structures described. The compounds are [( morph)(+)( 5- nsa)(-)] 1, [( hmt)(+)( 5- nsa)(-) . H2O] 2, and [( en) (2+) 2( 5- nsa)(-) . H2O] 3. In all compounds, protonation of the hetero- nitrogen of the Lewis base occurs. With 1, the 5- nsa anions and the morpholine cations lie, respectively, in or across crystallographic mirror planes and are linked within the planes by hydrogen- bonding interactions through the aminium group and the carboxylic and phenolic oxygens of the anionic 5- nsa species giving a two- dimensional sheet polymer. Compound 2 is an unusual structure with the planar 5- nsa anions lying within pseudo mirror planes and cyclically linked by duplex water bridges through a single carboxylate oxygen into centrosymmetric dimers. The hmt cation molecules are disordered across the pseudo mirror and are strongly linked by N+ - H ... O hydrogen bonds only to the water molecules with peripheral weak hmt C - H ... O hydrogen bonds extending the dimer within and between the dimer planes. Compound 3 is a network polymer comprised of the 5- nsa anions, the en dianions, and the water molecule in an extensive hydrogen- bonded structure.