title: Ammonium 1-hydroxy-2-(2-pyridinio)ethane-1,1-diyldiphosphonate dihydrate and potassium 1-hydroxy-2-(2-pyridinio)ethane-1,1-diyldiphosphonate dihydrate.
abstract: The crystal structures of the title compounds, ammonium risedronate dihydrate, NH4+.C7H10NO7P2-.2H2O, (I), and potassium risedronate dihydrate, K+.C7H10NO7P2-.2H2O, (II), have been determined from single-crystal X-ray data collected at 120 K. Compound (I) forms a three-dimensional hydrogen-bonded network which connects the ammonium and risedronate ions and the water molecules. In compound (II), the K+ ions are seven-coordinated in a capped distorted trigonal prism. The coordination polyhedra form chains by corner-sharing, and these chains are connected by phosphonate groups into layers in the ac plane. The layers are stacked and connected by hydrogen bonds in the b direction. The risedronate conformation is determined by intramolecular interactions fine-tuned by crystal packing effects. All H-atom donors in both structures are involved in hydrogen bonding, with D...A distances between 2.510 (2) and 3.009 (2) A.
authors.affiliation: Department of Chemistry, Technical University of Denmark, DK-2800 Lyngby, Denmark. kenny@kemi.dtu.dk
authors.forename: Kenny
authors.initials: K
authors.lastname: Stahl
authors.forename: Jette
authors.initials: J
authors.lastname: Oddershede
authors.forename: Herbert
authors.initials: H
authors.lastname: Preikschat
authors.forename: Erik
authors.initials: E
authors.lastname: Fischer
authors.forename: Jacob S
authors.initials: JS
authors.lastname: Bennekou
mesh_terms: D003461:Crystallography; D006860:Hydrogen Bonding; D008958:Models, Molecular; D063065:Organophosphonates / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*
chemical_list: D063065:Organophosphonates; D011725:Pyridines; D000644:Quaternary Ammonium Compounds; C515685:potassium 1-hydroxy-2-(2-pyridinio)ethane-1,1-diyldiphosphonate dihydrate