Metal iodates attract much research attention due to their applications as promising second-order nonlinear optical (NLO) materials.  

Great effects have been made in order to synthesize new metal iodates with excellent second harmonic generation (SHG) properties. It has long been known as effective routes to combine d⁰ transition metal ions or cations containing lone-pair electrons such as Pb²⁺ and Bi³⁺ with the iodate anions in designing NCS metal iodates.  

Other strategies usually adopted are the introduction of transition metal ions with a square-planar MO₄ geometry (M = Pd²⁺ or Au³⁺) into iodates or the polymerization of IO₃^- groups into polyiodate anions, which has already led to a range of NCS or polar structures with good SHG properties. 

Prof. MAO Jianggao and his group from the State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, have obtained the first metal iodate fluoride, i.e. Bi(IO₃)F₂ with a very strong SHG effect through the introduction of F^- as an independent anion into bismuth iodate.  

The structure of Bi(IO₃)F₂ features a novel 3D network, in which [BiF₂]⁺ framework gives rise to the favorable alignment of the IO₃ groups.  

Bi(IO₃)F₂ displays a rather wide transmittance window and exhibits very strong second harmonic generation (SHG) responses of about 11.5×KDP under 1064 nm laser radiation and 1.0×KTP under 2.05 μm laser radiation.  

The preliminary investigation indicates that Bi(IO₃)F₂ is a promising nonlinear optical (NLO) material in the visible and mid-IR regions. 

The team believes that metal iodate fluorides can be a new class of potential NLO materials and their study has shed some new light on the idea of designing new SHG materials based on metal iodates through the introduction of fluoride anions. 

The work has been published as a communication entitled “Bi(IO₃)F₂: The First Metal Iodate Fluoride with a Very Strong Second Harmonic Generation Effect” in Angew. Chem. Int. Ed. 

 [BiF₂]⁺ framework in Bi(IO₃)F₂ gives rise to the favorable alignment of the IO₃ groups and a very strong SHG effect (Image by Prof. MAO’s group)