Hydrothermal synthesis and crystal structures of Nd(IO3)3 and Al(IO3)3

Two metal iodates, Nd(IO3)3 and Al(IO3)3, have been prepared by hydrothermal reactions at 170 °C. The X-ray single-crystal structural analysis showed that Nd(IO3)3 presented here is a new polymorph crystallizing in a monoclinic space group P21/n with a = 8.859(1) Å, b = 5.9296(5) Å, c = 15.301(3) Å, β = 96.95(1)°, Z = 4. Al(IO3)3 crystallizes in a non-centrosymmetric group P63 with a = 9.003(1) Å, c = 5.2406(5) Å, Z = 2. The crystal structure of Nd(IO3)3 consists of 1D chains of edge-sharing NdO9 polyhedra, which are stitched into slabs through the bridging IO3− groups; and slabs are held together via the weak IO bonds resulting in a 3D framework. Al(IO3)3 is characterized by the slightly distorted AlO6 octahedra that are bridged by IO3− groups giving rise to a 3D polar network. Infrared spectra further confirmed that both compounds contain low symmetric IO3− groups.