NaB 3 O 4 F(OH): A Hydroxyfluorooxoborate with One-Dimensional Chain Featuring Large Birefringence and Short Ultraviolet Cutoff Edge.

A new sodium hydroxyfluorooxoborate, NaB 3 O 4 F(OH) (NBOFH), was discovered and synthesized. NBOFH features the unprecedented [B 3 O 4 F(OH)] infinite chain constructed by the novel fundamental building block (FBB) of [B 3 O 5 F(OH)]. NBOFH has a large birefringence of 0.097 at 1064 nm and short ultraviolet (UV) cutoff edge below 200 nm. First-principles calculations and response electron distribution anisotropy (REDA) were performed to explain the structure-property relationships. This work provides a novel strategy for the synthesis of deep-ultraviolet birefringent crystals and enriches the structural diversity of the emerging hydroxyfluorooxoborates.