Synthesis, crystal structure, optical properties and theoretical calculations of a new potassium lead pentaborate, KPbB5O9

A new potassium lead pentaborate compound, KPbB5O9 has been synthesized by standard solid-state reaction for the first time. Its structure has been determined by single-crystal X-ray diffraction method. It crystallizes in the monoclinic space group P21/c with lattice constants a = 6.717(3) Å, b = 8.389(3) Å, c = 13.686(5) Å, β = 94.679(4)° and Z = 4. The structure consists of double ring B5O9 units, KO8 and PbO6 polyhedra. The PbO6 polyhedra linked together via corner-sharing O atom forming novel infinite ∞[PbO6] chains along the b axis. Thermal analyses, IR spectroscopy and UV-vis-NIR diffuse reflectance spectrum, and band structure calculation were performed.