Ln2(O2CCH2PO3)2(H2O)3 · H2O (Ln = La, Pr, Nd, Sm): Layered lanthanide phosphonoacetates containing two-dimensional –Ln–O– linkages

Four novel isostructural lanthanide phosphonate compounds with formula Ln2(O2CCH2PO3)2(H2O)3 · H2O [Ln = La (1), Pr (2), Nd (3), Sm (4)] have been prepared through hydrothermal reactions of phosphonoacetate acid and lanthanide nitrates. All show layered structures made up of {LnO9} polyhedra and {CPO3} tetrahedra with the lattice water molecules locating between the layers. Within the layer, chains of edge-sharing {LnO9} polyhedra are connected via corner-sharing by phosphonate oxygens forming a two-dimensional –Ln–O– linkage. Thermal analyses and XRD measurements reveal that the framework structures can be maintained up to 400 °C.