The first metal iodate fluoride, Bi(IO )F , with a strong second harmonic generation (SHG) effect has been prepared. Bi(IO )F crystallizes in the polar space group C2 and features a three-dimensional [BiF ] cationic framework with IO groups capping the inner walls of the one-dimensional tunnels. This [BiF ] cationic framework acts as a template for the assembly of the polar IO units in a favorable superposed fashion, which leads to the polar structure of the material. Bi(IO )F displays a rather wide transmittance window (0.3-11 μm) and exhibits a very strong SHG response that is about 11.5 times larger than that of KH PO (KDP) under 1064 nm laser radiation and the same as that of KTiOPO (KTP) under 2.05 μm laser radiation. Preliminary investigations indicate that Bi(IO )F is a promising nonlinear optical material in the visible and mid-IR region.

Four new potassium vanadyl iodates based on lone-pair-containing IO3 and second-order Jahn−Teller distorted VO5 or VO6 asymmetric units, namely, α-KVO2(IO3)2(H2O) (Pbca), β-KVO2(IO3)2(H2O) (P212121), K4[(VO)(IO3)5]2(HIO3)(H2O)2 ·H2O (P1), and K(VO)2O2(IO3)3 ( Ima2) have been successfully synthesized by hydrothermal reactions. α-KVO2(IO3)2(H2O) and β-KVO2(IO3)2(H2O) exhibit two different types of 1D [VO2(IO3)2]− anionic chains. Neighboring VO6 octahedra in the α-phase are corner-sharing into a 1D chain with the IO3 groups attached on both sides of the chain in a uni- or bidentate bridging fashion, whereas those of VO5 polyhedra in the β-phase are bridged by IO3 groups into a right-handed helical chain with remaining IO3 groups being grafted unidentately on both sides of the helical chain. The structure of K4[(VO)(IO3)5]2(HIO3)(H2O)2 ·H2O contains novel isolated [(VO)(IO3)5]2− units composed of one VO6 octahedron linked to five IO3 groups and one terminal O2− anion. The structure of K(VO)2O2(IO3)3 exhibits a 1D [(VO)2O2(IO3)3]− chain in which neighboring VO6 octahedra are interconnected by both oxo and bridging iodate anions. Most interestingly, three of four compounds are noncentrosymmetric (NCS), and K(VO)2O2(IO3)3 displays a very strong second-harmonic generation response of about 3.6 × KTP, which is phase matchable. It also has high thermal stability, a wide transparent region and moderate hardness as well as an excellent growth habit. Thermal analyses and optical and ferroelectric properties as well as theoretical calculations have also been performed.

Two new noncentrosymmetric isomeric silver polyiodates, namely, α-AgI3O8 (Pnc2) and β-AgI3O8 (I4̅), 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 c 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.