The goal of this workshop is to identify opportunities emerging from recent heavy element discoveries that can transform conventional actinide chemistry and potentially establish new paradigms in science, in general. Results published in the past few years show that plutonium (Pu) and the other heavy elements have more extensive electron transfer chemistry than previously envisioned. These discoveries suggest that understanding heavy element redox processes could lead to major advances in electron transfer science across the periodic table.

Background. Fundamental research campaigns within the field of Heavy Element Chemistry have historically provided the U.S., the Atomic Energy Commission (AEC), and the Department of Energy (DOE) with insight and understanding that led to creative solutions for complicated technical problems in energy and national security since the discovery of plutonium (Pu) in 1940. These challenges continue today, with the chemistry of actinide elements occupying central roles in many areas that influence our quality of life. Actinides are key components for the DOE's mission in energy security. They are fuels in nuclear power generation, plutonium (238Pu) is a valuable heat source used in space exploration, and americium (241Am) and californium (252Cf) play critical roles within the fossil fuel industry as neutron sources for oil and gas exploration. The science of the 5f-elements is also critical for national security, underpinning the safety, security, and effectiveness of the U.S. nuclear weapons stockpile. Also, heavy element chemistry is important in terms of identifying and reducing global threats from weapons of mass destruction, in terms of nonproliferation, and in mounting calculated responses to domestic and international nuclear emergencies. These energy and national security endeavors - unfortunately - created several environmental issues, most of which are associated with waste from nuclear facilities run by the Office of Science, Office of Nuclear Energy, and National Nuclear Security Agency (NNSA).

Critical for managing the situations described above is developing a fundamental understanding of actinides. Knowledge on this front leads to responsible and informed policies regarding all actinide technologies and technical solutions for actinide-centered problems. From this perspective, the Office of Basic Energy Sciences in the Chemical Sciences, Geosciences, and Biosciences Division (BES/CSGB) plays a unique role within the Office of Science and for the Office of Nuclear Energy, NNSA, and the community of scientists working throughout the world. The global community looks to BES/CSGB for guidance and continued excellence in advancing the fundamental understanding of actinides.

An emerging area in actinide science in need of BES/CSGB’s attention is actinide electron transfer chemistry. Almost every relevant actinide technologically relies - at some point - on the actinide electron transfer reaction. This spans (1) using actinides in nuclear power to achieve energy security, (2) modeling mobility, assessing hazard, and controlling the fate and transport of actinides in the environment, and (3) carrying out large-scale uranium and plutonium oxide and metal production. Surprising discoveries over the last decade - led primarily by BES/CSGB - have revealed a vast intellectual void associated with actinide redox chemistry. For example, creative synthetic strategies have been recently developed that provided access to actinide elements in unusual oxidation states, those typically ignored as being too reactive to be relevant. Overshadowing those breakthroughs is the discovery of new oxidation states for almost all of the f-elements, many of which have been assumed for over 100 years to be inaccessible. The implication that f-elements can access new oxidation states suggests that there is a subfield of heavy element redox chemistry that has been hidden for the last century. Synthetically accessing, spectroscopically characterizing, and computationally evaluating these unconventional actinide species will likely open new doors in heavy element chemistry and potentially equip researchers to deal better with legacy issues from the Cold War, newly emerging problems associated with actinide elements today, and future f-element challenges that the next-generation nuclear workforce will encounter. This workshop directly addresses this intellectual shortfall and seeks to:

1) Outline new opportunities for accessing actinides in unconventional oxidation states.
2) Identify new spectroscopic tools that can be used to characterize transient actinide species
in unconventional oxidation states.
3) Investigate how actinide redox chemistry can be controlled to direct reactivity, speciation,
mobility, and isotope fractionation in complex matrixes (e.g. in molten salts, biological
media, and the environment).
4) Determine opportunities (and challenges) for computationally modeling the dynamics of
actinide redox reactions.
5) Identify the impact of heavy element electron transfer chemistry in other areas of science,
beyond the actinide 5f-block.

This workshop will deliver a manuscript written by its participants and submitted to a peer-reviewed journal. We hope that this document has value on two fronts. At headquarters, the document will provide community input to BES/CSGB in support of its strategic planning efforts within the area of actinide electron transfer chemistry. In the scientific community, the document will stimulate communication between researchers in neighboring fields and inspire science that generates innovative solutions to emerging challenges facing the DOE in heavy element chemistry.