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 K 2 Zn(IO 3 ) 3 (I 2 O 5 (OH))(IO 2 (OH))(H 2 O) (KZIOH) was synthesized by coupling distorted ZnO 6 octahedra with three diverse asymmetrical chromophores to assemble “tumbler-like” clusters, [Zn(IO 3 )(I 2 O 5 (OH))], which was the first noncentrosymmetric (NCS) and polar iodate containing isolated [IO 3 ], [I 2 O 5 (OH)], and [IO 2 (OH)]. KZIOH exhibits the strongest SHG response (∼12 × KH 2 PO 4 (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.