Chemistry research breakthrough that could improve nuclear waste recycling technologies

Researchers from The University of Manchester have taken a major step forward by describing the quantitative modelling of the electronic structure of a family of uranium nitride compounds – a process that could in the future help with nuclear waste recycling technologies.

This research has been published in the leading multi-disciplinary journal Nature Communications.

“In this nuclear age, there is a pressing need for improved extraction agents for nuclear waste separations and recycling technologies,” explained Professor Steve Liddle, Head of Inorganic Chemistry and Co-Director of the Centre for Radiochemistry Research at The University of Manchester.

“To achieve this, a much better understanding of the electronic structure of actinide complexes is needed since this impacts on how these elements interact with extractants.

“However, quantifying the electronic structure of these elements in molecules is a major challenge because many complex electronic effects become very important and of similar magnitude to each other with heavy elements.

“This makes their modeling very complex and much more difficult than for more routinely probed elements such as the transition metals.

“This means that traditional descriptions of the electronic structure of actinide elements are often of a qualitative nature – but this is precisely the area where quantitative models are needed because our understanding of core chemical concepts become increasingly nebulous at the foot of the periodic table.”

Many members of the team had previously reported uranium nitride and oxo complexes where the molecules are essentially the same except for swapping a single nitrogen atom for an oxygen. The team realised that the symmetry of the complexes and oxidation state of the uranium ions rendered them ideal systems from which to develop quantitative models.

“However, the problem was that in order to move from qualitative to quantitative regimes a large family of molecules would be required to make the method robust, but their synthesis was not reliable,” added Professor Liddle.

“Fortunately, the team identified a new and reliable way to make the uranium nitride complexes. This enabled a large family of molecules to be prepared, which then gave the necessary platform from which to develop a robust quantitative model.

“With a family of 15 nitride and oxo complexes, a wide range of state-of-the-art techniques available at Manchester were deployed. Using variable temperature magnetisation studies the researchers were able to gain key information about the some of the lowest-lying electronic states of the molecules.

“Electron paramagnetic resonance spectroscopy, based in the national service at Manchester, was then used to further build a picture about the lowest-lying electronic states.

“Finally, near-infrared spectroscopy provided information on the rest of the full electronic structure by probing electronic transitions into states above the ones probed by the first two techniques. In order to make sense of a wealth of experimental data advanced ab initio calculations were used to build a rough picture of the electronic structures of these complexes, which was then refined using the experimentally obtained data to provide a final quantitive picture of the electronic structure.”

The project was also supported by the Royal Society, the Engineering and Physical Sciences Research Council, the European Research Council, The Universities of Manchester and Nottingham, the EPSRC UK National EPR Facility, and the National Nuclear Laboratory.

The paper, ‘Molecular and electronic structure of terminal and alkali metal-capped uranium(V) nitride complexes,’ was published in Nature Communications. doi:10.1038/ncomms13773

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Stephen Liddle

21 December 2016

Originally published in
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    By: Stephen Liddle

    Steve Liddle is Professor and Head of Inorganic Chemistry and co-Director of the Centre for Radiochemistry Research at The University of Manchester. He was born in Sunderland in the North East of England and obtained his BSc (Hons) in 1997 and PhD (Prof. W. Clegg) in 2000 from Newcastle University. After postdoctoral fellowships at Edinburgh University (Dr P. Bailey), Newcastle University (Dr K. Izod) as the Wilfred Hall Research Fellow, and Nottingham University (Prof. P. Arnold) he was appointed to a fixed-term Lectureship at Nottingham University in 2007. He subsequently took up a Royal Society University Research Fellowship (2007-2015) with a proleptic Lectureship, and he was promoted to Associate Professor and Reader in 2010 and Professor of Inorganic Chemistry in 2013. He moved to The University of Manchester in 2015. He was elected a Fellow of the Royal Society of Chemistry in 2011 and as Vice President to the Executive Committee of the European Rare Earth and Actinide Society (2012-now). He was Chairman of COST Action CM1006, a 22 country 120 research group network for f-block chemistry (2011-2015), and he is a National Co-ordinating Centre for Public Engagement Ambassador and advisor to the Commonwealth Scholarship Commission. He was one of the Periodic Videos team awarded the IChemE Petronas award for excellence in education and training in 2008. He was awarded the RSC Sir Edward Frankland Fellowship and the RSC Radiochemistry Group Bill Newton Awards in 2011, and in 2014 he was a recipient of a Rising Star Award at the 41st International Conference on Coordination Chemistry. He was awarded the RSC Corday-Morgan prize in 2015. He was awarded a European Research Council (ERC) Starter Grant in 2009 and a ERC Consolidator Grant in 2014. He currently holds an EPSRC Established Career Fellowship (2015-2020). He is a board member of Philosophical Transactions A of the Royal Society and Inorganics and he has published over 150 research articles, reviews, and book chapters.

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