SrB 5 O 7 F 3 Functionalized with [B 5 O 9 F 3 ] 6− Chromophores: Accelerating the Rational Design of Deep‐Ultraviolet Nonlinear Optical Materials

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 SrB 5 O 7 F 3 , which is rationally designed by taking the classic Sr 2 Be 2 B 2 O 7 (SBBO) as a maternal structure. Its [B 5 O 9 F 3 ] 6− fundamental building block with near‐planar configuration composed by two edge‐sharing [B 3 O 6 F 2 ] 5− rings in SrB 5 O 7 F 3 has not been reported in any other borates. Solid state 19 F and 11 B magic‐angle spinning NMR spectroscopy verifies the presence of covalent B−F bonds in SrB 5 O 7 F 3 . Property characterizations reveal that SrB 5 O 7 F 3 possesses the optical properties required for deep‐UV NLO applications, which make SrB 5 O 7 F 3 a promising crystal that could produce deep‐UV coherent light by the direct SHG process.