La2(CN2)3 – the missing link of rare-earth carbodiimides, prepared through an efficient synthetic route and its Ce3+ activated photoluminescence

Abstract

Rare-earth (RE) carbodiimides according to the composition RE₂(CN₂)₃ have been reported for the whole series of RE elements, all prepared by solid-state metathesis (SSM) reactions. Only one compound, La₂(CN₂)₃, could not be made by this way of synthesis. Herein, we report the preparation of La₂(CN₂)₃ by using lanthanum cyanurate as a single-source precursor. The conversion of the precursor is analyzed by thermoanalytical studies. The crystal structure of the precursor and the novel La₂(CN₂)₃ are characterized by X-ray diffraction techniques. La₂(CN₂)₃ is represented by a distinct crystal structure with a dodecahedral environment of the La³⁺ ion. Having the knowledge of the last missing rare-earth carbodiimide, we herein present a summary of all existing RE₂(CN₂)₃ compounds, including their structural relationships. Doping with Ce³⁺ leads to the La₂(CN₂)₃:Ce³⁺ phosphor, which is reported with its photoluminescence properties.