BaPO₃Cl: a Metal Phosphate Chloride with Infinite [PO₃]_∞ Chains

We adopted a chemical substitution strategy to design a particular anionic structure with large optical anisotropy in phosphate. Specifically, we replaced one O^2– in Ba₃P₃O₁₀Cl by two Cl^–, leading to the formation of a new compound of BaPO₃Cl (P2₁/c). Notably, this compound is the first metal phosphate chloride featuring infinite [PO₃]_∞ chains, and it displays good chemical and thermal stability, as well as a short UV cutoff edge (<200 nm) and relatively large birefringence.