Pb8M(BO3)6 (M = Zn, Cd): Two new isostructural lead borates compounds with two-dimensional ∞[Pb8B6O18]2− layer structure

Single crystals of Pb8M(BO3)6 (M = Zn, Cd) have been successfully synthesized by high temperature solution method and their structures are determined by single-crystal X-ray diffraction methods. The compounds crystallize in the trigonal space group R3¯ (No. 148) with unit-cell parameters a = 9.505(6) Å, c = 18.162(9) Å, V = 1421(2) Å3 for the Zn compound and a = 9.5584(16) Å, c = 18.670(3) Å, V = 1477.2(6) Å3 for the Cd compound. Both of the materials represent a new two-dimensional (2D) ∞[Pb8B6O18]2− layer, which is composed of BO3 and PbOx (x = 4, 6) polyhedra. The layers are further bridged by the M2+ (Zn2+, Cd2+) ions, giving rise to a three-dimensional (3D) framework. Thermal analysis, IR spectroscopy, UV–Vis–NIR diffuse reflectance spectra, and band structure calculations are performed on the reported compounds.