Copper–lead selenite bromides: a new large family of compounds partly having Cu2+ substructures derivable from kagome nets

Abstract

Extensive experiments in the Pb–Cu–Se–O–Br system at 400°C yielded single crystals of nine new compounds (Cu2+Pb6(SeO3)4Br6, Cu2+Pb2(SeO3)2Br2, Cu2+ 3Pb2.4(SeO3)5Br0.8, Cu2+ 2Pb(SeO3)2Br2, Cu2+ 4Pb(SeO3)4Br2, [Cu2+ 9Pb2O4](Cu+Br2)(SeO3)4Br5, [Cu2+ 7PbO3](Cu+Br)0.35(SeO3)3Br4, [Cu2+ 8Pb2O4](Cu+Br)1.5(SeO3)4Br4, [Cu2+ 6Pb3O4](Cu+Pb1.27Br3.54)(SeO3)4Br2), all but one exhibiting new complex layered or open-framework architectures, organized via the host–guest principle. Five of these structures contain only bivalent copper: three with well ordered 2D structures and completely filled atomic positions, two structures have 3D frameworks. The four remaining compounds contain both, Cu2+ and Cu+, and comprise layers formed by edge- and vertex-sharing of oxocentered OCu2+ 4–n Pb n tetrahedra decorated with SeO3 2− and Br− anions. The interlayer spaces are filled by partially disordered Cu+–Br and Pb–Br associations. One remarkable feature of the latter group of compounds is the presence of tetrahedral (Cu2+)4 complexes with arrangements derivable from a kagome network.