Einsteinium coordination complex isolated for the first time

Einsteinium is the heaviest element in the periodic table that can be made in sufficient quantities for conventional chemistry experiments. Only a handful of compounds of this incredibly rare element have ever been isolated, and they’ve all been simple inorganics such as oxides and halides. But after 6 years of planning, researchers have finally created an einsteinium coordination complex (Nature 2021, DOI: 10.1038/s41586-020-03179-3). “I don’t believe we’ve seen any study on an isolated molecular complex” of einsteinium before, says Rebecca J. Abergel of Lawrence Berkeley National Laboratory and the University of California, Berkeley, who co-led the research with Stosh A. Kozimor of Los Alamos National Laboratory. The researchers worked with less than 200 ng of ²⁵⁴Es, which was produced at Oak Ridge National Laboratory’s High Flux Isotope Reactor by firing neutrons into a curium target. This relatively stable einsteinium isotope has a half-life of 276 days. The team treated ²⁵⁴Es with a hydroxypyri­dinone-based ligand to form an eight-coordinate complex and then carried out luminescence spectroscopy and X-ray absorption spectroscopy experiments. The scientists measured the first bond length involving einsteinium and confirmed that the complex was in the +3 oxidation state. The research helps fill data gaps in the actinide series of elements and should enable researchers to better understand chemical and physical trends across the series.