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.