K(3)V(2)O(3)F(4)(IO(3))(3): a high-performance SHG crystal containing both five and six-coordinated V(5+) cations

The combination of d(0) transition metal oxofluorides with iodate anions helps to synthesize polar crystals. Herein, a novel polar crystal, K(3)V(2)O(3)F(4)(IO(3))(3), which is the first metal vanadium iodate with two types of V(5+)-centered polyhedra (VO(4)F(2) octahedron and VO(3)F(2) trigonal bipyramid), has been prepared hydrothermally. It crystallizes in the polar space group of Cmc2(1) and its structure displays an unprecedented 0D [V(2)O(3)F(4)(IO(3))(3)](3−) anion, which is composed of Λ-shaped cis-[VO(2)F(2)(IO(3))(2)](3−) and [VO(2)F(2)(IO(3))](2−) anions interconnected via the corner-sharing of one oxo anion. The synergy gained from the VO(4)F(2), VO(3)F(2) and IO(3) groups resulted in K(3)V(2)O(3)F(4)(IO(3))(3) exhibiting both a strong second-harmonic generation (SHG) response (1.3 × KTiOPO(4)) under 2050 nm laser irradiation and a large birefringence (0.158 @ 2050 nm). This study provides a facile route for designing SHG materials by assembling various vanadium oxide-fluoride motifs and iodate anions into one compound.