Structural insights for the design of new borate–phosphates: synthesis, crystal structure and optical properties of Pb4O(BO3)(PO4) and Bi4O3(BO3)(PO4)
Two new metal borate–phosphates, Pb4O(BO3)(PO4) (1) and Bi4O3(BO3)(PO4) (2), have been successfully designed and synthesized. The structures of the title compounds were determined by single-crystal X-ray diffraction. The title compounds have similar crystal structures consisting of oxygen-centered (OPb4) or (OBi4) tetrahedra as well as isolated BO3 and PO4 groups. Structural comparison and the Madelung energy calculation indicate that the title compounds also exhibit a strong correlation with the known metal borates and phosphates. In addition, a strategy of BO3–PO4 substitution is proposed for designing new borate–phosphates. Thermal analyses, IR spectroscopy and UV-vis-NIR diffuse reflectance spectroscopy have also been performed.