BaB 2 P 2 O 8 F 2 : A Fluoroborophosphate with [B 2 P 2 O 8 F 2 ] ∞ Layers and Deep-Ultraviolet Cutoff Edge.

A fluoroborophosphate, BaB 2 P 2 O 8 F 2 , was successfully obtained. Its structure contains a novel [B 2 P 2 O 8 F 2 ] ∞ layer containing six-membered rings, which is formed by the fundamental building block composed of three types of non-π-conjugated groups, [PO 4 ], [BO 4 ], and [BO 2 F 2 ]. BaB 2 P 2 O 8 F 2 has a deep-ultraviolet (DUV) cutoff edge (λ < 200 nm) and a tiny birefringence (Δ n = 0.007 at 532 nm), which originates from the constituent non-π-conjugated groups. The title compound enriches the versatility of the fluoroborophosphates, encouraging further research into DUV materials in fluoroborophosphate systems.