Ba2ZnSc(BO3)3 and Ba4Zn5Sc2(BO3)8: first examples of borates in the Zn-Sc-B-O system featuring special structure configurations

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