Synthesis and structure of new layered copper oxide iodides, Sr₂CuO₂I₂ and Sr₂Cu₃O₄I₂

The first layered copper oxide iodides Sr2CuO2I2 and Sr2Cu3O4I2 have been synthesised by reaction of SrO, SrI2 and CuO in evacuated silica ampoules. Sr2CuO2I2 crystallises with a K2NiF4-type structure and contains infinite CuO2 planes separated by double SrI rocksalt layers. Sr2Cu3O4I2 contains sheets of Cu3O4 stoichiometry separated by fluorite Sr2I2 layers. Incorporation of the iodide ion results in an in-plane Cu–O bond distance of 2.015 Å in Sr2CuO2I2 whilst the two distinct copper sites in Sr2Cu3O4I2possess near identical in-plane Cu–O interactions ≈1.96 Å.