Coordination polymeric structures in the sodium salt of 4-chloro-3-nitro­benzoic acid and the sodium and potassium salts of 4-nitro­anthranilic acid

The hydrated sodium salt of 4-chloro-3-nitro­benzoic acid and the hydrated sodium and potassium salts of 2-amino-4-nitro­benzoic acid are stabilized by intra- and inter­molecular hydrogen bonding and strong [pi]-[pi] ring inter­actions. Na centres are linked through centrosymmetric four-membered duplex water bridges and through 18-membered duplex head-to-tail ligand bridges. Similar centrosymmetric bridges are found in the potassium salt.