The Science
A research team has discovered a new molecule containing the heavy element berkelium. Called "berkelocene," it is the first organometallic molecule containing berkelium. Organometallic molecules contain bonds between a carbon atom and a metal atom. Berkelium is a heavy element. It belongs to the actinide series shown near the bottom of the Periodic Table of Elements. Other actinides include uranium and plutonium. Berkelium and other actinides that do not occur naturally can only be created in nuclear reactors or accelerators. It is rare to create organometallic molecules with heavy elements in the actinide series. This research is the first time that scientists have found evidence of a chemical bond between carbon and berkelium.
The Impact
When actinides form organometallic compounds, the metal atoms form bonds with the carbon atoms. These bonds help scientists study the unique electronic structures of heavy elements. The structures provide insights into how matter is organized on the atomic level. Scientists wanted to create berkelocene to understand the bonds between carbon and berkelium. However, the element berkelium is extremely rare and only available in minute quantities. In addition, berkelium is highly radioactive, and organometallic compounds are reactive towards the water and oxygen in air. To overcome these challenges, the researchers developed specialized equipment to handle berkelocene. This study countered long-held theories about the chemistry of actinides. It will help scientists develop better models showing how their behavior changes across the Periodic Table. Improving these models can help scientists tackle issues related to the long-term storage and clean up of nuclear waste.
Summary
The Heavy Element Chemistry group at the Department of Energy's (DOE) Lawrence Berkeley National Laboratory (LBNL) has targeted the discovery of organometallic compounds of the actinides for many years. However, this is the first time that scientists have created this type of molecule with berkelium. Berkelium is a synthetic heavy element that is highly radioactive, with only very small amounts created each year. The scientists on this study used a combination of 0.3 mg of isotopes from the National Isotope Development Center at DOE's Oak Ridge National Laboratory. They also used specialized facilities at LBNL for handling air-sensitive and radioactive materials to create berkelocene. The scientists found that the molecule has a symmetrical structure with a berkelium atom sandwiched between two 8-membered carbon rings. Calculations then showed that the berkelium atom had a larger positive charge than expected. This result conflicted with the long-held theory that berkelium would behave like terbium, the element above it on the Periodic Table. This breakthrough disrupts long-held theories about the chemistry of the heavy elements.
Funding
This work was supported by the DOE Office of Science, Office of Basic Energy Sciences. Computational resources were provided by the Center for Computational Research of the University at Buffalo. This research used resources from the Advanced Light Source (a DOE Office of Science User Facility) and the National Isotope Development Center, which is managed by the DOE Isotope Program.