Scientists at Los Alamos National Laboratory brought together experimental and theory capabilities to isolate and characterize the first example of a compound in which americium (Am) is bonded to a molecule containing an unpaired electron called a “radical ligand.”
Molecules with unpaired electrons are extremely reactive, making the task of isolating them especially challenging when scientists are working on very small scales (approximately 5 milligrams of americium). Despite this drawback, the unpaired electrons enable new types of chemical bonding and reactions that would otherwise be impossible.
Importantly, the americium compound bonds differently than similar lanthanide compounds — a rare and noteworthy finding published in the Journal of the American Chemical Society. Fundamental studies that uncover subtle differences in bonding, reactivity and electronic structure, as this paper does, can enable future advances in chemical separation technology.
Why this matters: The nuclear industry could cut down on waste volume and storage timescales — plus optimize fuel recycling — if it had more effective ways to separate americium from chemically similar lanthanides in used fuel.
- In used fuel, americium decays slowly compared to most of the fission products.
- Americium is a significant contributor to long-term waste storage hazards, and proposed processes to “burn-up” (transmute) americium into elements/isotopes that pose less long-term hazards are hampered by the neutron-poisoning nature of lanthanides.
What they did:
- In work led by postdoctoral researchers Maria Beltrán-Leiva and Daniel Lussier, the team characterized the bonding interactions in these compounds experimentally by X-ray crystallography, various forms of spectroscopy and electrochemistry, as well as through quantum chemical calculations.
- The studies revealed that americium binds to that radical molecule more tightly than its lanthanide counterparts, proving that radical ligands can amplify subtle electron differences between otherwise similar metals (americium and lanthanides). Such molecules could provide new strategies for selectively binding specific elements.
Funding: U.S. Department of Energy, Office of Basic Energy Sciences, Heavy Element Chemistry Program; and the Laboratory’s Glenn T. Seaborg Institute (postdoctoral fellowships).
LA-UR-26-25205
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