Reinterpretation of Three Crystal Structures of Alkali Oxoiodate(V) – Description of the [I₃O₈]^–Anion and the Infinite 2D [I₃O₈^–]_∞Anion

Abstract

International audienceTwo Cs2(IO3)(I3O8) polymorph phases and the Rb2(I3O8)- (IO3)(HIO3)2(H2O) compound were prepared by hydrothermal syntheses and characterised by X-ray single crystal diffraction. α-Cs2(IO3)- (I3O8) crystallises in the hexagonal space group P63 (a = 7.366(1) Å; c = 13.883(1) Å; V = 652.3(1) Å3; Z' = 2) whereas β-Cs2(IO3)(I3O8) crystallises in monoclinic space group P21/n (a = 12.733(1) Å; b = 7.437(1) Å; c = 14.359(2) Å; β = 106.98(1)°; V = 1300.4(2) Å3; Z = 4) and Rb2(I3O8)(IO3)(HIO3)2(H2O) in triclinic space group P1¯ (a = 7.043(1) Å, b = 7.496(1) Å, c = 18.203(3) Å; α = 79.70(2)°; β = 85.04(2)°; γ = 70.66 (1)°; V = 891.8(2) Å3; Z = 2). β-Cs2(IO3)(I3O8) and Rb2(I3O8)(IO3)(HIO3)2(H2O) reveal the presence of [I3O8]- anion. These compounds have already been characterised as β-Cs2I4O11 and Rb2I6O15(OH)2*(H2O) for which the descriptions do not reflect the chemical structure. The previous descriptions are based on different choices for the I-O bonding character. In Rb2(I3O8)(IO3)(HIO3)2(H2O), the shortest I***O interaction (2.316(5) Å) observed between a [IO3 -] anion and HIO3 is in the same range of I-O bond length (2.201(4) Å) in the [I3O8]- anion. Bond valence calculations clearly show three classes of I-O interactions. Finally, DFT calculations coupled to the Electron Localisation Function analysis were performed to describe chemical schemes of these bonds, which justified our chemical description of the structures. The non-centrosymmetric α-Cs2(IO3)(I3O8) compound, revealed the presence of the infinite two-dimensional [I3O8 -]∞, which was obtained by condensation of iodate anions

REI5O14 (RE=Y and Gd): Promising SHG Materials Featuring the Semicircle‐Shaped I5O143− Polyiodate Anion

“…Each mirror‐symmetric I 5 O 14 pentamer contains one I(1)O 4 , two I(2a)O 4 , and two I(3a)O 3 units that are interconnected through corner‐sharing (Figure a). The I−O bonds of the I−O−I bridges (1.952(18)–2.423(18) Å) are longer than terminal I−O bonds (1.76(3)–1.82(3) Å), which are comparable with those of metal polyiodates reported previously . Each I 5 O 14 pentamer forms a hexadentate chelation with a Gd atom and also bridges with two other Gd atoms.…”

Titanyl Iodate – A Promising Material for Infrared Nonlinear Optics Showing Structural Similarities with KTP

“…[7,13] properties, as well as their ferroelectric, piezoelectric, and pyroelectric properties, [14][15][16][17][18][19][20][21][22] and these studies have recently been resumed in the 2000s. [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] The nonlinearity of KTP and its isotypes has been explained by the hyperpolarizability of the titanyl bonds. [40,41] So, in order to obtain a crystal with high nonlinear susceptibility, the molecular or ionic arrangement has to contain a periodic system of polarizable free electrons.…”

Recent advances on second-order NLO materials based on metal iodates

“…[85]. It should be mentioned that the I 5+ cation of the [IO 2 ] + layer is coordinated by four oxo atoms in a square planar geometry and all other I 5+ cations are also four-coordinated but in a quadrangular pyramidal environment (I O 1.993Å), each oxygen atom bridges with two I 5+ cation and no terminal I O bonds is found, such 2D layer is very different from the I 3 O 8 − layer in ␣-CsI 4 O 9 mentioned earlier [76]. Unfortunately, the SHG effect of Pb 3 (IO 3 )OCl 3 was not measured.…”

“…With the inclusion of the long I O contacts (I O = 2.323-2.441Å), the structure of ␤-Cs 2 I 4 O 11 can be described as a pseudo-three dimensional crystal structure consisting of asymmetric IO 3 and IO 4 groups separated by Cs + cations, whereas Rb 2 I 6 O 15 (OH) 2 ·H 2 O exhibits a 1D chain composed of IO 3 and IO 4 polyhedra, [I 2 O 5 (OH)] − dimers, and IO 2 (OH) polyhedra. In 2010, Gautier-Luneau et al re-synthesized both forms of Cs 2 I 4 O 11 and Rb 2 I 6 O 15 (OH) 2 ·H 2 O and reinterpreted the structures of above three compounds[76]. According to his calculations the long I O bonds large than 2.31Å should be considered as intermolecular interaction and should be excluded as the intra-molecular bonds, hence both Rb 2 I 6 O 15 (OH) 2 ·H 2 O and ␤-…”

“…Later, a number of NLO materials based on ternary metal iodates such as anhydrous divalent M(IO 3 ) 2 (M = Mg, Zn, Hg) [63,65], and trivalent metal iodates such as La(IO 3 ) 3 [68] and ␣-In(IO 3 ) 3 [66] were obtained, but they have twinning or phase transition problems, hence a lot of research efforts have been devoted to the explorations for new metal iodates with enhanced SHG performance and higher thermal stability. A number of metal iodates containing polyiodate anions (I O I bridges) possess very large SHG effects [73][74][75][76]. Several synthetic strategies have been developed successfully to design new metal iodates with excellent SHG properties, such as the introduction of other lone pair containing cations such as Pb 2+ and Bi 3+ [78][79][80][81][82][83][84][85][86][87], octahedrally coordination d 0 -TM cations such as Ti 4+ , V 5+ , Mo 6+ , and the d 8 -TMO 4 square planar units into the metal iodate systems [117][118][119].…”