Pb[PtBi6I12] – Infinite Chains of Heavy Atom Clusters

Abstract

Reaction of Bi with Pb, Pt and BiI3 above 330 °C yielded shiny, black, air insensitive crystals of the subiodide Pb[PtBi6I12]. Pb[PtBi6I12] crystallizes in the rhombohedral space group R3 with lattice parameters a = 1585.39(5) pm and c = 1098.77(3) pm at room temperature. The compound consists of cuboctahedral [PtBi6I12]2– clusters and Pb2+ cations in octahedral coordination between trigonal faces of two cuboctahedra, which concatenate them into linear chains. Six weaker Bi···I inter-cluster bridges per cluster connect the chains. The structure can be interpreted as a superstructure of the NaCl structure type, with iodide and platinum(–II) as anions and bismuth(II) and lead(II) as cations, leaving 18 out of 39 cation positions unoccupied. The arrangement of the cuboctahedral clusters follows the motif of a body-centered cubic packing. Pb[PtBi6I12] is a semiconductor with a measured bandgap of 0.69 eV. Full-relativistic DFT calculations indicate a topologically trivial bandgap of 0.58 eV.