Abstract
In a previous study, the X-ray structure of the title compound, C9H12N2O7P2·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 mol-ecule crystallizes in a zwitterionic form with cationic imidazolium[1,2a]pyridine and anionic phospho-nate groups. The dihedral angle formed by the planes of the pyridine and imidazole rings is 3.55 (9)°. A short intra-molecular C-H⋯O contact is present. In the crystal, mol-ecules are linked by O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds and π-π inter-actions [centroid-to-centroid distance = 3.5822 (11) Å], forming a three-dimensional structure.