Synthesis, Characterization, and Crystal Structure of Dicalcium Glutarylbis(phosphonate) Dihydrate: A Covalently Pillared Layer Structure with the Potential for Epitaxial Growth on Hydroxyapatite.
A new bis(acylphosphonate), glutarylbis(phosphonate) (GlBP), was synthesized. Sodium and calcium salts of the GlBP, disodium dihydrogen glutarylbis(phosphonate), NaHO(3)PC(O)(CH(2))(3)C(O)PO(3)HNa, and dicalcium glutarylbis(phosphonate) dihydrate, Ca(2)[O(3)PC(O)(CH(2))(3)C(O)PO(3)].2H(2)O, were prepared and characterized by chemical analyses, thermogravimetry and Fourier transform infrared spectroscopy (FTIR). The crystal structure of the Ca salt was determined by single-crystal X-ray diffraction. The crystals are orthorhombic with a = 10.970(1) Å, b = 23.694(2) Å, c = 5.580(1) Å, space group Pnma, and Z = 4. This study provides the first example of a structure of a calcium complex involving a nongeminal bis(phosphonate). The structure can be described in terms of a covalently pillared layer-type arrangement of neutral Ca-GlBP-Ca units along the b-axis. Each oxygen atom of the phosphonate group is bonded to a different Ca ion, and each Ca in turn is linked to three phosphonate groups. The Ca octahedra and the phosphonate tetrahedra form a two-dimensional polar sheet perpendicular to the b-axis. The chelate bonds involving the keto groups appear to be important links in the stabilization of the structure and, in turn, to the biological activity of bis(acylphosphonates). A near-perfect lattice match, found between the Ca phosphonate layer and the major crystal faces of hydroxyapatite, indicates that epitaxial growth or incorporation of GlBP can occur on the apatitic surface which may be the mode of action in the inhibition of calcification.
Mathew
Mathai
M
Paffenbarger Research Center, American Dental Association Health Foundation, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, National Institute of Dental Research's Craniofacial and Skeletal Diseases Branch Research Associate Program at the National Institute of Standards and Technology, Gaithersburg, Maryland 20899, Department of Pharmaceutical Chemistry, School of Pharmacy, The Hebrew University of Jerusalem, Jerusalem, Israel, Department of Pharmaceutics, School of Pharmacy, The Hebrew University of Jerusalem, Jerusalem, Israel, and Department of Pediatrics, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
Fowler
Bruce O.
BO
Breuer
Eli
E
Golomb
Gershon
G
Alferiev
Ivan S.
IS
Eidelman
Naomi
N