sigma-Aromatic Actinide-Actinide Bonding: A New Frontier in f-Block Chemistry

The Periodic Table is mainly composed of metals. Thus, metal-metal bonding is a vast burgeoning field that is fundamental to driving step-changes in our understanding of structure, bonding, reactivity, and magnetism. Over 177 years the s-, p-, and d-blocks have produced numerous routinely isolable examples of varied metal-metal bonding motifs. In contrast, isolable actinide-actinide (An-An) bonding, one of the top goals of synthetic An-chemistry, has remained elusive in all that time, precluding assessment of reactivity patterns that are a central tenet of understanding metal-metal bonding. This adventurous project aims to exploit our recent discovery of molecular isolable thorium-thorium bonding (Nature 2021, 598, 72-75), which describes surprising sigma-aromatic bonding to record principal quantum number 6 and 7th row of the Periodic Table and multi-electron small molecule activation reactivity. Building on our preliminary result, this project seeks to expand the range of An-An complexes, determine their reactivity trends, and probe their electronic structure and physicochemical properties using a comprehensive range of experimental and theoretical characterisation techniques. This will involve a wide range of project partners and national and international research facilities brought together into a cohesive and interleaved approach. This research is strategically important with respect to the nuclear sector, as it will retain a skilled ECR and train two new ones in a known UK skills-shortage area, and together with stakeholders we will develop 'best practice' methods for handling radioactive elements, thus promoting knowledge transfer at the academia:industry interface. By studying the compounds outlined in the project, new applications of analytical techniques will be developed, and the resulting methodological advances will develop the capability and health of those disciplines in-house, and also more broadly because those techniques involve facilities and researchers that work across many other areas that could benefit from the transfer of new working ways. This project is timely to develop and our preliminary results show the work is achievable and impactful. Thus, we request funds commensurate with the scope and ambition of the proposed work to develop this promising area in order to capitalise on our breakthrough, stay at the international forefront of this newly created and exciting field, and generate results of international significance to An-chemistry.