New Metal Iodates: Syntheses, Structures, and Characterizations of Noncentrosymmetric La(IO3)3 and NaYI4O12 and Centrosymmetric β-Cs2I4O11 and Rb2I6O15(OH)2·H2O

A series of new alkali metal indium iodates with isolated or extended anions

Systematic explorations of new phases in the A(I)-In(III)-I(V)-O system by hydrothermal reactions led to five new compounds, namely, AIn(IO(3))(4) (A = Li, Na), Rb(3)In(IO(3))(6) and A(2)HIn(IO(3))(6) (A = Rb, Cs). The structure of AIn(IO(3))(4) (A = Li, Na) contains one-dimensional [In(IO(3))(4)](-) chains separated by Li(+) or Na(+) cations. In both compounds, each In(3+) cation is octahedrally coordinated by six IO(3)(-) anions, neighboring In(3+) cations are interconnected by bidentate bridging iodate anions into 1D chains. The structures of Rb(3)In(IO(3))(6) and A(2)HIn(IO(3))(6) (A = Rb, Cs) all feature isolated [In(IO(3))(6)](3-) anions with alkali metal ions (and H(+) ions) as spacers. Both optical diffuse reflectance spectrum measurements and band structure calculations based on DFT methods indicate that LiIn(IO(3))(4), NaIn(IO(3))(4), and Rb(2)HIn(IO(3))(6) are insulators.

Two-dimensional dysprosium(III) triiodate(V) dihydrate, Dy(IO(3))(3)(H(2)O)·H(2)O

During our research into novel nonlinear optical materials using 1,10-phenanthroline as an appending ligand on lanthanide iodates, crystals of an infinite layered Dy(III) iodate compound, Dy(IO(3))(3)(H(2)O)·H(2)O, were obtained under hydro-thermal conditions. The Dy(III) cation has a dicapped trigonal prismatic coordination environment consisting of one water O atom and seven other O atoms from seven iodate anions. These iodate anions bridge the Dy(III) cations into a two-dimensional structure. Through O-H⋯O hydrogen bonds, all of these layers stack along [111], giving a supra-molecular channel, with the solvent water mol-ecules filling the voids.

Polar or nonpolar? A+ cation polarity control in A2Ti(IO3)6 (A = Li, Na, K, Rb, Cs, Tl)

We have synthesized a series of new alkali-metal or Tl(+) titanium iodates, A(2)Ti(IO(3))(6) (A = Li, Na, K, Rb, Cs, Tl). Interestingly the Li and Na phases are noncentrosymmetric (NCS) and polar, whereas the K, Rb, Cs, and Tl analogues are centrosymmetric (CS) and nonpolar. We are able to explain the change from NCS polar to CS nonpolar using cation-size arguments, coordination requirements, and bond valence concepts. The six materials are topologically similar, consisting of TiO(6) octahedra, each of which is bonded to six IO(3) polyhedra. These polyhedral groups are separated by the A(+) cations. Our calculations on Na(2)Ti(IO(3))(6) indicate that polarization reversal is energetically very unfavorable, rendering the material polar but not ferroelectric. For all of the materials, synthesis, structural characterization, electronic structure analysis, infrared spectra, UV-vis and thermogravimetric measurements, and ion-exchange reactions are reported. For the polar materials, second-harmonic generation, piezoelectricity, and polarization measurements were performed. Crystal data: Li(2)Ti(IO(3))(6): hexagonal, space group P6(3) (No. 173), a = b = 9.3834(11) A, c = 5.1183(6) A, Z = 1. Na(2)Ti(IO(3))(6): hexagonal, space group P6(3) (No. 173), a = b = 9.649(3) A, c = 5.198(3) A, Z = 1. K(2)Ti(IO(3))(6): trigonal, space group R3 (No. 148), a = b = 11.2703(6) A, c = 11.3514(11) A, Z = 3. Rb(2)Ti(IO(3))(6): trigonal, space group R3 (No. 148), a = b = 11.3757(16) A, c = 11.426(3) A, Z = 3. Cs(2)Ti(IO(3))(6): trigonal, space group R3 (No. 148), a = b = 11.6726(5) A, c = 11.6399(10) A, Z = 3. Tl(2)Ti(IO(3))(6): trigonal, space group R3 (No. 148), a = b = 11.4167(6) A, c = 11.3953(11) A, Z = 3.

Synthesis, Structure, Characterization, and Calculations of Two New Sn2+−W6+−oxides, Sn2WO5 and Sn3WO6

Two new Sn2+-W6+-oxides, Sn2WO5 and Sn3WO6, have been synthesized hydrothermally, and their structures have been determined by single-crystal X-ray diffraction methods. Both materials exhibit layered structural topologies consisting of two edge-shared WO6 octahedra connected to SnO3 and SnO4 polyhedra. Both the W6+ and Sn2+ cations are in locally asymmetric coordination environments attributable to second-order Jahn-Teller effects. Infrared and Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, and thermogravimetric analysis were also performed on the reported materials. Theoretical calculations using the tight binding linear muffin tin orbital method agree with the observed electronic properties of these materials and indicate that the stereoactive lone pair on the Sn2+ is similar for both materials. Crystal data: Sn2WO5, monoclinic, space group P21/n (No. 14), a = 7.994(2) A, b = 13.712(4) A, c = 10.383(3) A, beta = 110.507(3) degrees , V = 1066.0(5) A3, and Z = 4; Sn3WO6, monoclinic, C2/c (No. 15), a = 12.758(3) A, b = 8.0838(16) A, c = 13.865(3) A, beta = 112.49(3) degrees , V = 1321.2(5) A3, and Z = 8.

Structural Polarity Induced by Cooperative Hydrogen Bonding and Lone-Pair Alignment in the Molecular Uranyl Iodate Na2[UO2(IO3)4(H2O)]

Na2[UO2(IO3)4(H2O)] has been synthesized under mild hydrothermal conditions. Its structure consists of Na+ cations and [UO2(IO3)4(H2O)](2-) anions. The [UO2(IO3)4(H2O)](2-) anions are formed from the coordination of a nearly linear uranyl, UO2(2+), cation by four monodentate IO(3-) anions and a coordinating water molecule to yield a pentagonal bipyramidal environment around the uranium center. The water molecules form intermolecular hydrogen bonds with the terminal oxo atoms of neighboring [UO2(IO3)4(H2O)](2-) anions to yield one-dimensional chains that extend down the b axis. There are two crystallographically unique iodate anions in the structure of Na2[UO2(IO3)4(H2O)]. One of these anions is aligned so that the lone-pair of electrons is also directed along the b axis. The overall structure is therefore polar, owing to the cooperative alignment of both the hydrogen bonds and the lone-pair of electrons on iodate. The polarity of the monoclinic space group C2 (a = 11.3810(12) A, b = 8.0547(8) A, c = 7.6515(8) A, beta = 90.102(2) degrees , Z = 2, T = 193 K) found for this compound is consistent with the structure. Second-harmonic generation of 532 nm light from a 1064 nm laser source yields a response of approximately 16x alpha-SiO2.