K3V2O3F4(IO3)3: a high-performance SHG crystal containing both five and six-coordinated V5+ cations†
Abstract
The combination of d0 transition metal oxofluorides with iodate anions helps to synthesize polar crystals. Herein, a novel polar crystal, K3V2O3F4(IO3)3, which is the first metal vanadium iodate with two types of V5+-centered polyhedra (VO4F2 octahedron and VO3F2 trigonal bipyramid), has been prepared hydrothermally. It crystallizes in the polar space group of Cmc21 and its structure displays an unprecedented 0D [V2O3F4(IO3)3]3− anion, which is composed of Λ-shaped cis-[VO2F2(IO3)2]3− and [VO2F2(IO3)]2− anions interconnected via the corner-sharing of one oxo anion. The synergy gained from the VO4F2, VO3F2 and IO3 groups resulted in K3V2O3F4(IO3)3 exhibiting both a strong second-harmonic generation (SHG) response (1.3 × KTiOPO4) 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.