Reactions of metal chloride or sulfate and the sodium salt of 5-nitrosalicylic acid (5-nsa) in aqueous solution result in isomorphous complexes of type [M(H2O)(5)(5-nsa)](+) (5-nsa)(-) center dot H2O [M = Mg (1), Zn (2), Co (3), Ni (4)] in the solid state. Structural analyses of these compounds reveal that the cationic moiety is a monomeric complex in which the metal is coordinated by five aqua ligands and one carboxylato O-atom from the 5-nitrosalicylato ligand, forming a slightly distorted octahedron. The crystal packing exhibits ionic parts assembled through extensive hydrogen bonding. The metal-bonded cationic moiety and the non-ligating anionic one are also engaged in pi-stacking interactions which contribute to the crystal cohesion. The anchoring of the individual ionic subunits through pi-pi stacking and hydrogen bonding results in a 3D supramolecular architecture.