Pb 2 Al 2 B 3 O 8 F 3 : structure and properties of a new fluoroaluminoborate with non-traditional chain-like B 3 O 8 groups.

A new fluoroaluminoborate, Pb 2 Al 2 B 3 O 8 F 3 , with a non-traditional chain, [B 3 O 8 ] 7- , was synthesized by high temperature reactions in closed systems for the first time. Different from the traditional [B 3 O 8 ] 7- ring [(3:Δ + 2T)], the [B 3 O 8 ] 7- in Pb 2 Al 2 B 3 O 8 F 3 is chain-like [(3:2Δ + T)]. In the structure, the chain-like [B 3 O 8 ] 7- group bonds with [AlO 4 F 2 ] 7- polyhedra to form the [AlB 3 O 10 F 2 ] 8- cluster, and the cluster further interconnects to form a three-dimensional framework. The effect of cations on B-O configuration was explored by analyzing available aluminum borates to provide a useful reference for the synthesis of new aluminoborate or fluoroaluminoborate. In addition, first-principles calculations were performed to investigate the relationship between the crystal structure and the optical properties.