α‑AgI₃O₈ and β‑AgI₃O₈ with Large SHG Responses: Polymerization of IO₃ Groups into the I₃O₈ Polyiodate Anion

Two new noncentrosymmetric isomeric silver polyiodates, namely, α-AgI₃O₈ (<i>Pnc</i>2) and β-AgI₃O₈ (<i>I</i>4̅), have been synthesized through the hydrothermal reactions of AgNO₃ with I₂O₅. Both isomers exhibit layered structures that are constructed from I₃O₈^– anions interconnected by Ag⁺ cations. The main structural difference between the two isomers lies in the different stacking fashions of [AgI₃O₈] layers along the <i>c</i> axis in order to meet the requirements of their space groups. Powder second-harmonic generation (SHG) measurements indicate that α-AgI₃O₈ and β-AgI₃O₈ are both phase-matchable materials with large SHG responses of approximately 9.0 and 8.0 times that of KH₂PO₄, respectively. UV–vis–NIR transmission spectra show that the cutoff absorption edges are 328 nm for α-AgI₃O₈ and 345 nm for β-AgI₃O₈. Thermal stability studies demonstrate that both isomers are thermally stable up to about 370 °C. Theoretical calculations based on DFT methods for the two AgI₃O₈ phases as well as the NaI₃O₈ analogue have been performed

Acentric La₃(IO₃)₈(OH) and La(IO₃)₂(NO₃): Partial Substitution of Iodate Anions in La(IO₃)₃ by Hydroxide or Nitrate Anion

Partial substitution of iodate anions in La­(IO₃)₃ by OH^– or NO₃^– anion led to acentric La₃(IO₃)₈(OH) and chiral La­(IO₃)₂(NO₃). The structure of La₃(IO₃)₈(OH) can be seen as a complex three-dimensional (3D) network composed of two-dimensional [La₃(IO₃)₂(OH)]⁶⁺ cationic layers that are further bridged by remaining iodate anions, or alternatively as a 3D network composed of one-dimensional [La₃(IO₃)₆(OH)]²⁺ cationic columns being further interconnected by additional iodate anions, while the structure of La­(IO₃)₂(NO₃) can be seen as a novel 3D structure with planar NO₃ groups serving as linkage between the [La₃(IO₃)₆]³⁺ triple layers. Compared to La­(IO₃)₃, both compounds show considerably wide band gaps and enhanced thermal stability. La­(IO₃)₂(NO₃) shows a moderate second harmonic generation (SHG) response of ∼0.6 times that of KDP (KH₂PO₄), a wide band gap of 4.23 eV, and a high LDT value (22 × AgGaS₂). Optical property measurements, thermal analysis, as well as theoretical calculations on SHG origin, were performed. It can be deduced that partial substitution of iodate anions can be a facile route to design new noncentrosymmetric metal iodates with novel structure and potential application

Syntheses, Characterization, and Optical Properties of Centrosymmetric Ba₃(BS₃)_1.5(MS₃)_0.5 and Noncentrosymmetric Ba₃(BQ₃)(SbQ₃)

The most advanced UV–vis and IR NLO materials are usually borates and chalcogenides, respectively. But thioborates, especially thio-borometalates, are extremely rare. Here, four new such compounds are discovered by solid state reactions representing 0D structures constructed by isolated BQ₃ trigonal planes and discrete MQ₃ pyramids with Ba²⁺ cations filling among them, centrosymmetric monoclinic <i>P</i>2₁<i>/c</i> Ba₃(BS₃)_1.5(MS₃)_0.5 (M = Sb, Bi) <b>1</b>, <b>2</b> with <i>a</i> = 12.9255(9), 12.946(2) Å; <i>b</i> = 21.139(2), 21.170(2)­Å; <i>c</i> = 8.4194(6), 8.4207(8) Å; β = 101.739(5), 101.688(7)°; <i>V</i> = 2252.3(3), 2259.9(3) ų and noncentrosymmetric hexagonal <i>P</i>6̅2<i>m</i> Ba₃(BQ₃)­(SbQ₃) (Q = S, Se) <b>3</b>, <b>4</b> with <i>a</i> = <i>b</i> = 17.0560(9), 17.720(4) Å; <i>c</i> = 10.9040(9), 11.251(3) Å; <i>V</i> = 2747.1(3), 3060(2) ų. <b>3</b> exhibits the strongest SHG among thioborates that is about three times that of the benchmark AgGaS₂ at 2.05 μm. <b>1</b> and <b>3</b> also show an interesting structure relationship correlated to the size mismatching of the anionic building units that can be controlled by the experimental loading ratio of B:Sb. Syntheses, structure characterizations, and electronic structures based on the density functional theory calculations are reported