An antimony(iii) borate with large birefringence exhibiting unwonted [B5O11] fundamental building blocks and dimeric [Sb2O6] clusters

Abstract

A new birefringent crystal SbB₅O₉ has been synthesized by combining π-conjugated [B₃O₆] groups and Sb³⁺ cations with SCALP. It exhibits the unwonted [B₅O₁₁] fundamental building block (FBB) and dimeric [Sb₂O₆] cluster. Remarkably, SbB₅O₉ exhibits a short UV cutoff edge (below 240 nm) and a large birefringence (Δn = 0.151 @ 1064 nm) which is even better than that of the well-known commercial birefringent material α-BaB₂O₄ (α-BBO) (Δn = 0.122 @ 532 nm). First-principles calculations show that the birefringence enhancement mainly originates from the highly distorted [Sb₂O₆] dimer and π-conjugated B–O anionic groups.