Ba10LuB18O32F13: the first example of borate in the Lu–B–O–F system with the unprecedented FBB [B9O22]

Abstract

A new alkaline-earth and rare-earth borate fluoride, Ba₁₀LuB₁₈O₃₂F₁₃, the first example of borate in the Lu–B–O–F system, has been successfully synthesized in a high-temperature vacuum system. It crystallizes in the orthorhombic system, with the Fmm2 space group and the parameters a = 16.5749(6) Å, b = 16.7644(9) Å, c = 13.6222(6) Å, and Z = 4. It represents a new fundamental building block (FBB), [B₉O₂₂], with the notation 9:[2(4:2Δ + 2T) + T], in which two [BO₃] triangles and two [BO₄] tetrahedra are enclosed into a [B₄O₁₀] ring and every two [B₄O₁₀] rings are bridged by a [BO₄] tetrahedron. The [B₉O₂₂] FBBs are further condensed into a 3D network with two types of channels that accommodate Ba²⁺ and Lu²⁺ cations. The UV cut-off edge is below 190 nm, indicating the application potential of Ba₁₀LuB₁₈O₃₂F₁₃ in the DUV region. Additionally, to further explore the structural novelty of Ba₁₀LuB₁₈O₃₂F₁₃, a comparison with all anhydrous borates with 18 boron atoms in their chemical formula was carried out. The fascinating results indicate that [B₉O₂₂] has been discovered for the first time, enriching borate fluoride structure chemistry.