{[In2S7]8-}∞ Chain and Isolated HgS4 Planar Unit Constructed One-Dimensional Pentanary Sulfide K2Ba7HgIn4S16 Exhibiting Nonlinear-Optical Activity

EuSi7P10: An Inorganic Supramolecular Nonlinear Optical Crystal Exhibiting Strong Second-Harmonic Generation Response

Inorganic supramolecular compounds are the emergent class of infrared (IR) nonlinear optical (NLO) materials. However, the reported inorganic supramolecular IR NLO pnictides are still scarce. In this work, a new inorganic supramolecular IR NLO phosphide, EuSi7P10, has been synthesized using the metal salt flux method. The structure of EuSi7P10 features an anionic host framework containing the oriented [Si7P16] dual-T2 supertetrahedra with the guest Eu2+ cations filling in the intervals. Additionally, EuSi7P10 exhibits strong phase-matched (PM) second-harmonic generation (SHG) (4.0 × AgGaS2), large birefringence (0.087 @2050 nm), and wide infrared transparency. This study highlights the potential of inorganic supramolecular pnictides for exploring high-performance IR NLO crystals.

A2Hgx(SeO3)y (A = K, Rb, Cs): Three Alkali Metal Mercury Selenites Featuring Unique 1D [HgOm(SeO3)n]∞ Chains

Herein, three alkali metal mercury selenites, K2Hg2(SeO3)3, Rb2Hg2(SeO3)3, and Cs2Hg3(SeO3)4, were successfully obtained by a hydrothermal method. The three compounds featured same one-dimensional (1D) [HgOm(SeO3)n]∞ chain structure that consisting of distorted Hg-O polyhedra and SeO3 triangular pyramids with stereochemically active lone pair (SCALP) electrons. Interestingly, the rich coordination environment of Hg atoms and the size difference of alkali metal cations lead to diverse arrangement of SeO3 groups, which makes them exhibit different birefringence. The band gaps of the three compounds indicate that they are potential ultraviolet (UV) optical materials. Detailed theoretical calculations demonstrate that the combined effects of SeO3 triangular pyramids and Hg-O polyhedra are responsible for the optical characteristics of the reported compounds.

KHg4Ga3S9: A Hg-Based Sulfide with Nonlinear-Optical Activity in the A-MII-MIII-Q (A = Alkali Metal; MII = d10 Metal; MIII = Ga, In; Q = S, Se) System

The search for new high-performance infrared (IR) nonlinear-optical (NLO) materials is a hot topic in the fields of laser chemistry and inorganic solid-state chemistry. Here, a new Hg-based sulfide KHg4Ga3S9 in the family of A-MII-MIII-Q (A = alkali metal; MII = d10 metal; MIII = Ga, In; Q = S, Se) was synthesized. It crystallizes in the orthogonal system of the C2221 structure, which is rare for IR NLO chalcogenides. Its anionic framework {[Hg4Ga3S9]-}∞ is constructed by two types of interconnected helical chains, viz., the inner layer ({[Hg6Ga2S29/3]4/3-}∞) and the outer layer ({[Hg2Ga4S25/3]2/3-}∞). It exhibits a moderate NLO response and a high laser-induced damage threshold. Theoretical calculations indicate that the HgS4 unit accounts for its much larger NLO response compared to RbCd4Ga3S9. The influence of alkali metals and d10 metals on the initial phase-matching wavelength is also discussed. This work provides inspiration for improving the properties of NLO materials' properties.