The first barium lead oxychloride Ba27Pb8O8Cl54 with new isolated [Pb4O4] clusters

The new oxychloride, Ba 27 Pb 8 O 8 Cl 54 , has been synthesized by a high temperature solution method. It crystallizes as cubic brown block with unit-cell a  = 22.547(2), space group Fm 3 ¯ m (No. 225). It features a complicated three-dimensional network composed of [Ba 20 O 4 Cl 92 ] and [Ba 14 O 8 Cl 36 ] units sharing one Ba atom and its coordination atoms, which is inserted by new isolated [Pb 4 O 4 ] clusters. The UV–Vis-IR diffuse reflectance spectrum exhibits that its optical band gap is about 3.9 eV. In this paper, the structural features, thermal behaviors and optical properties were systemically studied.