Poly[aqua[μ3-(pyridin-1-ium-3,5-diyl)diphosphonato-κ3O:O′:O′′][μ2-(pyridin-1-ium-3,5-diyl)diphosphonato-κ2O:O′]calcium(II)]

Abstract

The rigid organic ligand (pyridine-3,5-diyl)diphosphonic acid has been used to create the title novel three-dimensional coordination polymer, [Ca(C5H6NO6P2)2(H2O)]n. The six-coordinate calcium ion is in a distorted octahedral environment, formed by five phosphonate O atoms from five different (pyridin-1-ium-3,5-diyl)diphosphonate ligands, two of which are unique, and one water O atom. Two crystallographically independent acid monoanions,L1 andL2, serve to link metal centres using two different coordination modes,viz.η2μ2and η3μ3, respectively. The latter ligand,L2, forms a strongly undulated two-dimensional framework parallel to the crystallographicbcplane, whereas the former ligand,L1, is utilized in the formation of one-dimensional helical chains in the [010] direction. The two sublattices ofL1 andL2 interweave at the Ca2+ions to form a three-dimensional framework. In addition, multiple O—H...O and N—H...O hydrogen bonds stabilize the three-dimensional coordination network. Topologically, the three-dimensional framework can be simplified as a very unusual (2,3,5)-connected three-nodal net represented by the Schläfli symbol (4·82)(4·88·10)(8).