Hydro­gen bonding in proton-transfer compounds of 8-quinolinol (oxine) with aromatic sulfonic acids

The crystal structures of the proton-transfer compounds of 8-quinolinol (oxine) with the aromatic sulfonic acids 2-amino­benzene­sulfonic acid (orthanilic acid) and 8-hydroxy-7-iodo­quinoline-5-sulfonic acid (ferron) have been determined. In both 8-hydroxy­quinolinium 2-amino­benzene­sulfonate, C₉H₈NO⁺·C₆H₆NO₃S⁻, (I), and 8-hydroxyquino­linium 8-hydroxy-7-iodo­quinoline-5-sulfonate ses­qui­hydrate, C₉H₈NO⁺·C₉H₆INO₄S⁻·1.5H₂O, (II), extensive hydrogen-bonding interactions, together with significant cation–cation [in (I)] and cation–anion [in (II)] π–π stacking associations, give rise to layered polymer structures.