Supramolecular Isomerism and Isomorphism in the Structures of 1,4-Butanebisphosphonic Acid and Its Organic Ammonium Salts

1,4-Butanebisphosphonic acid crystallizes as two concomitant polymorphs, a triclinic phase (1a) and
an orthorhombic phase (1b), both comprising pillared-layered hydrogen-bonded networks and exhibiting supramolecular isomerism. Two organic salts of this acid with aniline (2) and p-phenylazoaniline (3) were synthesized and
characterized by X-ray diffraction analysis. Compounds 2 and 3 show supramolecular isomorphism with pillared-bilayered frameworks. Our results demonstrate the potential use of bisphosphonic acids for the synthesis of new
solid materials.