Hochdrucksynthese von Cd(NH3)2[B3O5(NH3)]2: ein grundlegender Weg in die Substanzklasse der Amminborate

The First High-Pressure Chromium Oxonitridoborate CrB4 O6 N-an Unexpected Link to Nitridosilicate-Chemistry

CrB₄O₆N crystallizes in the non‐centrosymmetric space group P6₃mc (no. 186) with the lattice parameters a=5.1036(1), c=8.3519(3) Å, and a volume of 188.40(1) ų. It was synthesized in a high‐pressure/high‐temperature experiment at 7 GPa and 1673 K and represents the first high‐pressure oxonitridoborate. It is built up of starlike‐shaped entities of four BO₃N tetrahedra, connected via one common nitrogen atom that resembles the fourfold‐coordinated nitrogen atoms in the homeotypic nitridosilicates MYbSi₄N₇ (M=Sr, Ba). Building up a network with channels that contain the Cr³⁺ ions, CrB₄O₆N contains for the first time a tetrahedral building unit in contrast to trigonal planar B(O/N)₃ entities in all other known oxonitridoborates. The structural relations as well as the results of spectroscopic measurements and calculations on the chromium oxonitridoborate are discussed.

Cs4 B4 O3 F10 : First Fluorooxoborate with [BF4 ] Involving Heteroanionic Units and Extremely Low Melting Point

Herein, a new congruently melting mixed-anion compound Cs₄ B₄ O₃ F₁₀ has been characterized as the first fluorooxoborate with [BF₄ ] involving heteroanionic units. Compound Cs₄ B₄ O₃ F₁₀ possesses two highly fluorinated anionic clusters and therefore its formula can be expressed as Cs₃ (B₃ O₃ F₆ ) ⋅ Cs(BF₄ ). The influence of [BF₄ ] units on micro-symmetry and structural evolution was discussed based on the parent compound. More importantly, Cs₄ B₄ O₃ F₁₀ shows the lowest melting point among all the available borates and thus sets a new record for such system. This work is of great significance to enrich and tailor the structure of borates using perfluorinated [BF₄ ] units.

Two Covalent Ultraviolet Nonlinear Optical Crystals

Nonlinear optical (NLO) crystals are the vital components of laser science and technology, as they can convert lasers in common wavelengths into new wavelength bands for ultraviolet (UV), IR, and even terahertz laser output. Known UV NLO crystals mainly focus on crystals containing cations, but covalent crystals have rarely been reported. Here we report two covalent NLO crystals, B₂ O₃ I and B₂ O₃ II. According to the first-principles calculations, B₂ O₃ I and II have extremely short absorption edges of about 134 nm and 141 nm, large NLO coefficients of d₂₂ =1.38 pm/V and d₂₄ =0.702 pm/V, as well as sufficient birefringences of 0.037 and 0.031, respectively. Notably, the absorption edges are almost the shortest among NLO crystals. Meanwhile, the NLO coefficients are evidently larger than that of another well-known covalent NLO crystal α-SiO₂ and are comparable to those of the commercial UV NLO crystal LiBO₃ with Li⁺ cation. Furthermore, the birefringences are significantly larger than that of α-SiO₂ , which are favorable to the phase matching for both crystals. These results reveal that B₂ O₃ I and B₂ O₃ II are excellent candidates for UV NLO applications. In-depth calculations are carried out to reveal the origin of excellent NLO properties. These covalent crystals provide a new direction for the research of UV NLO crystals.