From NaGa(IO)F to NaGa(IO)F and NaGa(IO): The Effects of Chemical Substitution between F Anions and IO Groups on the Structures and Properties of Gallium Iodates.

Introducing F anions or substituting F anions with IO groups has been proven to be ideal strategies for designing novel noncentrosymmetric (NCS) and polar materials, yet systematic investigation into the effect of F anions or the substitution of IO for F anions on structures and properties remains rarely explored. Herein, two new gallium iodates, NaGa(IO)F () and NaGa(IO) (), were successfully designed and synthesized based on NaGa(IO)F by introducing more F anions and replacing F anions with IO groups, respectively. Structurally, in compound , the adjacent [GaF(IO)] polyanions are connected in an antiparallel manner, resulting in a complete cancellation of local polarity. While in compound , all IO groups in 2D [Ga(IO)] layers are aligned, leading to large macroscopic polarization. Additionally, chemical substitution also results in a qualitative improvement in the functional properties of compound . It possesses strong SHG response (12 × KDP @1064 nm) and broad optical transparency, coupled with large birefringence (0.21 @1064 nm), showcasing its promise as a promising nonlinear optical (NLO) crystal. The effects of chemical substitution between F anions and IO groups on the structures and properties are discussed in detail.