SrB5 O7 F3 Functionalized with [B5 O9 F3 ]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 [BOx F4-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 SrB5 O7 F3 , which is rationally designed by taking the classic Sr2 Be2 B2 O7 (SBBO) as a maternal structure. Its [B5 O9 F3 ]6- fundamental building block with near-planar configuration composed by two edge-sharing [B3 O6 F2 ]5- rings in SrB5 O7 F3 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 SrB5 O7 F3 . Property characterizations reveal that SrB5 O7 F3 possesses the optical properties required for deep-UV NLO applications, which make SrB5 O7 F3 a promising crystal that could produce deep-UV coherent light by the direct SHG process.