ZrF 2 (IO 3 ) 2 and RbGaF 3 (IO 3 ): Two Promising Birefringent Crystals Featuring 1D Metal-Fluoride Cationic Chains and Wide Bandgaps.

Herein, two novel metal iodate-fluorides, ZrF ₂ (IO ₃ ) ₂ and RbGaF ₃ (IO ₃ ), have been prepared via hydrothermal reactions. In the structure of ZrF ₂ (IO ₃ ) ₂ , neighboring Zr atoms are connected via a pair of F atoms into the one-dimensional (1D) [ZrF ₂ ] ²⁺ cationic chain, which further attaches two iodate groups forming 1D ZrF ₂ (IO ₃ ) ₂ , whereas the 1D cationic chain in RbGaF ₃ (IO ₃ ) is [GaF] ²⁺ , formatted by the bridging of Ga ³⁺ cations and axial F ^- anions, which further connect with one iodate group and two terminal F ^- anions into 1D [GaF ₃ (IO ₃ )] ^- anionic chains. According to the experimental characterization and theoretical calculations, both of them exhibit wide bandgaps (4.24 and 4.61 eV), short absorption edges (242 and 216 nm), and large birefringence (Δ n _cal = 0.329 @1064 nm and Δ n _cal = 0.174 @1064 nm for ZrF ₂ (IO ₃ ) ₂ and RbGaF ₃ (IO ₃ ), respectively), indicating that they can be candidates as UV birefringent materials.