Hydrothermal Synthesis, Crystal Structure and Characterizations of Four New Metal Phosphonates with Layered Structure

By using piperazine as a structure-directing agent, four new metal phosphonates with layered structure, [pzH(2)](0.5)[ML(H2O)]center dot 1.5H(2)O [M = Co (1), Ni (2), Zn (3)] and [pz](0.5)[Sb2L2]center dot H2O (4) (H3L = 2-hydroxyphosphonoacetic acid; pz = piperazine), have been hydrothermally synthesized and structurally characterized by single-crystal and Powder X-ray diffraction, infrared spectroscopy, elemental analysis and thermogravimetric analysis. Compounds 1-3 are isostructural octahedra and tetrahedra connected by and comprise MO6 octahedra and CPO3 [O3PCH(OH)CO2](3-) to form a 2D layered structure with one-dimensional channel system along the a axis direction. In compound 4, two SbO4E trigonal bipyramids (E is a lone pair of electrons which occupy an axial position) are interconnected into a dimer by corner-sharing. The so-built dimers are bridged by the CPO3 tetrahedra into a 2D layered structure with a one-dimensional channel system in the c axis direction. The protonated piperazine cations for compounds 1-3 and the piperazine molecules for compound 4 are located between two adjacent layers.