Ce2AgYb5/3Se6, La2CuErTe5, and Ce2CuTmTe5: Three new quaternary interlanthanide chalcogenides

Three new ordered quaternary interlanthanide chalcogenides, Ce2AgYb5/3Se6, La2CuErTe5, and Ce2CuTmTe5, have been prepared by direct reaction of the elements in molten NaBr at 900 °C. Each compound forms a new structure-type. The Ce2AgYb5/3Se6 structure consists of ∞2{[AgYb5/6Se6]6–}∞2{[AgYb5/6Se6]6–} layers intercalated by Ce3+ cations. These layers are composed of ∞1{[Yb5/3Se6]7–}∞1{[Yb5/3Se6]7–} quadruplet ribbons of [YbSe6]9– octahedra and infinite ∞1{[AgSe6]11–}∞1{[AgSe6]11–} double chains of [AgSe5]9–. The La2CuErTe5 structure is made of one-dimensional ∞1{[CuErTe5]6–}∞1{[CuErTe5]6–} ribbons separated by La3+ cations. These ribbons are formed by cis -edge sharing ∞1{[CuTe2]3–}∞1{[CuTe2]3–} tetrahedral chains and trans -edge sharing ∞1{[ErTe4]5–}∞1{[ErTe4]5–} chains. While La2CuErTe5 crystallizes in the orthorhombic space group Pnma , Ce2CuTmTe5 crystallizes in the monoclinic space group C 2/m . The latter crystal structure is assembled from ∞2{[CuTmTe5]6–}∞2{[CuTmTe5]6–} layers intercalated by Ce3+ cations. These layers consist of single ∞1{[TmTe4]5–}∞1{[TmTe4]5–} chains connected to each other through dimers or pseudo-double chains.