More than 75 years after its initial discovery, scientists have created an organometallic molecule containing the transuranium element berkelium.
According to a new study, the electronic signature of the actinide element acts differently than lanthanides, which is what scientists previously expected.
Understanding the atomic behavior of transuranium elements can help scientists tackle real-world issues like nuclear waste storage and remediation.
In December 1949, University of California at Berkeley chemist Glenn Seaborg, along with Stanley Thompson and Albert Ghiorso, bombarded an isotope of the actinide americium, only discovered five years prior, with helium nuclei in a cyclotron. This created an entirely new element known (fittingly) as berkelium, and was one major step toward Seaborg’s eventual Nobel Prize win in 1951 for his discoveries of transuranium (i.e. elements with a higher atomic number of 92) elements.
However, that was only the beginning of berkelium’s story, and now more than 75 years later, scientists from the same laboratory that first discovered the element—the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab)— along with scientists from the University of Buffalo and Alexandru Ioan Cuza University in Romania has successfully created the first organometallic molecule to contain the heavy element berkelium.
During the process, they discovered something unexpected about this particular f-block element on the periodic table that could help us understand transuranium elements more broadly as well as provide insights into methods for tackling nuclear waste remediation. The results were published late last month in the journalScience.
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“This is the first time that evidence for the formation of a chemical bond between berkelium and carbon has been obtained,” Berkeley Lab’s Stefan Minasian, senior author of the study, said in a press statement. “The discovery provides new understanding of how berkelium and other actinides behave relative to their peers in the periodic table.”
For decades the Berkeley Lab has been creating organometallic compounds of actinides because the resulting molecules usually have high symmetries and multiple covalent bonds with carbon, but creating such a molecule with berkelium wasn’t easy due to the element’s scarcity. According to Berkeley Lab, only minute amounts of the element are produced every year (in fact, only two reactors in the world can make it) and is sensitive to air and moisture—in other words, there was little room for error.
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Luckily, the team successfully trapped a berkelium atom between two cyclooctatetraene (COT) ligands, which Chemistry World describes as a kind of “organometallic sandwich.” What makes berkelium interesting compared to other actinides is that it has a tetravalent oxidation state (a positive charge of +4) that’s stabilized by the berkelium–carbon bonds. This makes its behavior different from the lanthanide terbium, which is located above actinides in the periodic table.
“The electronic structure calculations, as well as the experimental observations, show that berkelocene is unlike its lanthanide analogs, which disrupts long-held assumptions about the chemical and physical properties of transplutonium elements,” University of Buffalo’s Jochen Autschbach, co-author of the study who performed the electronic signature calculations, said in a press statement.
The authors further state that understanding the behavior changes across actinides can help us understand “the underlying logic that nature is using to organize matter at the atomic level,” Minasian says. This could help future efforts of solving problems with nuclear waste storage and remediation, which is especially important as countries reinvest in nuclear energy in the existential race toward a net-zero carbon emission world.
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Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.