From NaGa(IO 3 ) 3 F to NaGa(IO 3 ) 2 F 2 and NaGa(IO 3 ) 4 : The Effects of Chemical Substitution between F - Anions and IO 3 - Groups on the Structures and Properties of Gallium Iodates.

Introducing F - anions or substituting F - anions with IO 3 - 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 3 - for F - anions on structures and properties remains rarely explored. Herein, two new gallium iodates, NaGa(IO 3 ) 2 F 2 ( 1 ) and NaGa(IO 3 ) 4 ( 2 ), were successfully designed and synthesized based on NaGa(IO 3 ) 3 F by introducing more F - anions and replacing F - anions with IO 3 groups, respectively. Structurally, in compound 1 , the adjacent [GaF 3 (IO 3 ) 3 ] 3- polyanions are connected in an antiparallel manner, resulting in a complete cancellation of local polarity. While in compound 2 , all IO 3 groups in 2D [Ga(IO 3 ) 4 ] ∞ - layers are aligned, leading to large macroscopic polarization. Additionally, chemical substitution also results in a qualitative improvement in the functional properties of compound 2 . 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 3 - groups on the structures and properties are discussed in detail.