Crystal structure of zwitterionic 3-(2-hydroxy-2-phosphonato-2-phosphonoethyl)imidazo[1,2-a]-pyridin-1-ium monohydrate (minodronic acid monohydrate): a redetermination

In a previous study, the X-ray structure of the title compound, C9H12N2O7P2 center dot H2O, was reported [Takeuchi et al., (1998). Chem. Pharm. Bull. 46,1703-1709], but neither atomic coordinates nor details of the geometry were published. The structure has been redetermined with high precision as its detailed knowledge is essential to elucidate the presumed polymorphism of minodronic acid monohydrate at room temperature. The molecule crystallizes in a zwitterionic form with cationic imidazolium[1,2a]pyridine and anionic phosphonate groups. The dihedral angle formed by the planes of the pyridine and imidazole rings is 3.55 (9)degrees. A short intramolecular C H center dot center dot center dot O contact is present. In the crystal, molecules are linked by O-H center dot center dot center dot O, N-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds and pi-pi interactions [centroid-to-centroid distance = 3.5822 (11) angstrom], forming a three-dimensional structure.