Scientists Synthesize 'Berkelocene,' Advancing Actinide Chemistry

In March 2025, scientists at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) announced the synthesis of "berkelocene," the first organometallic molecule incorporating the heavy element berkelium. This achievement provides new insights into the chemistry of actinide elements and may influence future approaches to nuclear waste management.

Berkelium, with atomic number 97, is a synthetic, highly radioactive element first produced in 1949 at the University of California, Berkeley. Due to its scarcity and radioactivity, berkelium has been primarily used in scientific research, particularly in the synthesis of heavier transuranium and superheavy elements.

The research team synthesized berkelocene using 0.3 milligrams of berkelium-249, an isotope with a half-life of 330 days. The molecule features a berkelium atom sandwiched between two eight-membered carbon rings, forming a symmetrical structure analogous to the previously known "uranocene." This configuration was confirmed through single-crystal X-ray diffraction experiments. Electronic structure calculations revealed that the berkelium atom in berkelocene exhibits a tetravalent oxidation state (+4), stabilized by berkelium–carbon bonds. This finding challenges traditional assumptions about the chemical behavior of actinide elements, particularly those beyond uranium in the periodic table.

"This is the first time that evidence for the formation of a chemical bond between berkelium and carbon has been obtained," said Stefan Minasian, a scientist in Berkeley Lab's Chemical Sciences Division and one of the study's co-corresponding authors. "The discovery provides new understanding of how berkelium and other actinides behave relative to their peers in the periodic table."

Understanding the chemistry of heavy elements like berkelium is crucial for addressing challenges related to nuclear waste storage and remediation. The discovery of berkelocene provides new insights into the behavior of actinides, which can inform the development of more effective methods for separating and managing radioactive waste. For instance, advancements in the purification of berkelium-249 have led to faster and more efficient separation techniques, which could be applied to other actinides in the future.

The synthesis of berkelocene required meticulous planning and the implementation of robust safety measures to protect researchers and the environment. Handling radioactive elements like berkelium presents unique risks, particularly due to their high radioactivity and the potential for exposure. The research team at Berkeley Lab employed custom-designed gloveboxes to create an air-free environment necessary for the safe manipulation of air-sensitive and radioactive materials. This innovation highlights the importance of developing enhanced safety protocols in nuclear research.

The discovery of berkelocene builds upon previous research into actinide chemistry. In the 1960s and 1970s, chemists synthesized organometallic complexes containing actinides such as uranium, thorium, protactinium, neptunium, and plutonium. However, berkelium, with its atomic number 97, had evaded similar characterization until now. This breakthrough represents a significant advancement in the understanding of actinide chemistry.

The synthesis and characterization of berkelocene mark a significant milestone in the field of nuclear chemistry. This discovery not only enhances the understanding of actinide behavior but also has potential applications in improving nuclear waste management practices. As research continues, the insights gained from berkelocene may lead to further advancements in both fundamental chemistry and practical applications related to radioactive materials.