Ba2ZnSc(BO3)3 and Ba4Zn5Sc2(BO3)8: First Examples of Borates in Zn-Sc-B-O System Featuring Special Structure Configuration
Abstract
First examples of borates in the Zn-Sc-B-O system, Ba2ZnSc(BO3)3 and Ba4Zn5Sc2(BO3)8, were synthesized through high-temperature solution method. Ba2ZnSc(BO3)3 can be described as the ZnO4 tetrahedra connecting with the ScO6 octahedra to form a [ZnScO9]13- dimer, which further bonds with seven BO3 triangles to form a 2∞[ZnSc(BO3)3] layer, then the Ba atoms distribute in the voids between the layers. While in Ba4Zn5Sc2(BO3)8, the Zn-O chains composed of 4- and 6-coordinated Zn atoms link with the Sc2O8 dimers to form a Zn-Sc-O layer, then the BO3 triangles and the Ba atoms fill in the voids between the layers. Interestingly, the special [Zn2(BO3)6]14- cluster is found in Ba2ZnSc(BO3)3, which is different from 2D layers or 3D frameworks of Zn-B-O configurations in other zincoborates. Moreover, the lowest-coordinated ScO5 polyhedra, as well as coexistence of two kinds of ZnOn units (n= 4 or 6), are firstly observed in Ba4Zn5Sc2(BO3)8. The fascinating results can promote the design of novel borates with the BO3 units and enrich the borate structure chemistry.