Hydrothermal syntheses, crystal structures and luminescence properties of three new metal diphosphonates with layered structure

摘要

Three new divalent metal(II) diphosphonates with layered structure, [Cd _(2.5)(L)(H _2O) _2F]·H _2O (1), [Cd _(3.5)(HL)(L)] (2) and [Sn _3O(L)] (3) (H _4L = C _6H _(11)N(CH _2PO _3H _2) _2), have been hydrothermally synthesized and structurally characterized by X-ray single-crystal diffraction, X-ray powder diffraction as well as with infrared spectroscopy, elemental and thermogravimetric analysis. For compound 1, each Cd(II) atoms are octahedrally coordinated [Cd(1)O _4NF, Cd(2)O _5F, Cd(3)O _6]. These cadmium octahedra form a 1D chain along the b-axis through edge- and corner-sharing, and such chains are further interlinked by CPO _3 tetrahedra via corner-sharing to form a 2D layer. In compound 2, the interconnection of Cd(1)O _6, Cd(2)O _5N(1), Cd(3)O _6 and Cd(4)O _5N(2) polyhedra via bridging diphosphonate ligands leads to a 2D Cd(II) phosphonate layer, which is analogous to that of compound 1. The structure of compound 3 shows a novel layered structure, in which the interconnection of three SnO _3 trigonal pyramids via the bridging oxygen atom forms a trimer, the so-built trimers are bridged by the diphosphonate ligands into a 2D Sn(II) phosphonate layer. In all three compounds, the organic groups of the ligands are oriented toward the interlayer space. Luminescence properties of compounds 1 and 2 have also been studied.