Two Hydroxyfluorooxoborates Achieving Deep-Ultraviolet Cutoff Edges and Moderate Birefringence by Assembling Multi-Anionic Groups.

Assembling multi-anionic groups is conducive to utilizing respective advantage to achieve the enhancement of optical performance. Two new hydroxyfluorooxoborates, Ama2-Rb 2 B 3 O 3 F 4 (OH) and K 8 Cs 2 B 15 O 14 (OH) 7 F 20  ⋅ H 2 O with [B 3 O 3 F 4 (OH)] six-membered rings were synthesized for the first time. The title compounds exhibit short ultraviolet cutoff edges (<200 nm) and K 8 Cs 2 B 15 O 14 (OH) 7 F 20  ⋅ H 2 O possesses a moderate experimental refractive index difference of 0.051@546 nm.