SrB₅O₇F₃ Functionalized with [B₅O₉F₃]⁶⁻ Chromophores: Accelerating the Rational Design of Deep‐Ultraviolet Nonlinear Optical Materials

Abstract

Fluorooxoborates, benefiting from the large optical band gap, high anisotropy, and ever‐greater possibility to form non‐centrosymmetric structures activated by the large polarization of [BO_x F_4−x ]^{(x +1)−} building blocks, have been considered as the new fertile fields for searching the ultraviolet (UV) and deep‐UV nonlinear optical (NLO) materials. Herein, we report the first asymmetric alkaline‐earth metal fluorooxoborate SrB₅O₇F₃, which is rationally designed by taking the classic Sr₂Be₂B₂O₇ (SBBO) as a maternal structure. Its [B₅O₉F₃]⁶⁻ fundamental building block with near‐planar configuration composed by two edge‐sharing [B₃O₆F₂]⁵⁻ rings in SrB₅O₇F₃ has not been reported in any other borates. Solid state ¹⁹F and ¹¹B magic‐angle spinning NMR spectroscopy verifies the presence of covalent B−F bonds in SrB₅O₇F₃. Property characterizations reveal that SrB₅O₇F₃ possesses the optical properties required for deep‐UV NLO applications, which make SrB₅O₇F₃ a promising crystal that could produce deep‐UV coherent light by the direct SHG process.