Designing a Strong Second-Harmonic Generation Polar Iodate by the Structure-Directing Properties of the “Tumbler-like” [Zn(IO3)(I2O5(OH))] Polyanions

Materials with second-harmonic generation (SHG) properties have attracted great attention in the field of photon technology. However, synthesis of materials with strong SHG responses and polar structure still faces enormous challenges. Herein, a new iodate K2Zn(IO3)3(I2O5(OH))(IO2(OH))(H2O) (KZIOH) was synthesized by coupling distorted ZnO6 octahedra with three diverse asymmetrical chromophores to assemble “tumbler-like” clusters, [Zn(IO3)(I2O5(OH))], which was the first noncentrosymmetric (NCS) and polar iodate containing isolated [IO3], [I2O5(OH)], and [IO2(OH)]. KZIOH exhibits the strongest SHG response (∼12 × KH2PO4 (KDP)@1064 nm) among the polyiodates with two or more types of isolate units and a short ultraviolet cutoff edge (262 nm). It also possesses a moderate birefringence (0.055@532 nm) and a wide band gap (4.0 eV), indicating KZIOH is a promising SHG material. Theoretical calculations and crystal structure analysis show that the asymmetric and top-heavy configurations of I–O groups around Zn-centered octahedral units with the aid of hydrogen bonding favor its polar structure and strong SHG response.