Experts at The University of Nottingham are the first to create a stable version of a ‘trophy molecule’ that has eluded scientists for decades. In research published in journal Science, the team of chemists at Nottingham has shown that they can prepare a terminal uranium nitride compound which is stable at room temperature and can be stored in jars in crystallized or powder form.
Previous attempts to prepare uranium-nitrogen triple bonds have required temperatures as low as 5 Kelvin (-268 °C) — roughly the equivalent temperature of interstellar space — and have therefore been difficult to work with and manipulate, requiring specialist equipment and techniques.
The breakthrough could have future implications for the nuclear energy industry — uranium nitride materials may potentially offer a viable alternative to the current mixed oxide nuclear fuels used in reactors since nitrides exhibit superior high densities, melting points, and thermal conductivities and the process the scientists used to make the compound could offer a cleaner, low temperature route than methods currently used.
The research has been led by Dr Stephen Liddle in the School of Chemistry and much of the practical work was completed by PhD student David King. The work was also supported by colleagues at the University of Manchester.
onia with uranium under high temperatures and pressures. Unfortunately, however, the harsh reaction conditions used in the preparation introduces impurities which are difficult to remove. In recent years scientists have therefore focussed their attention on using low temperature, molecular methods but all previous attempts resulted in bridging, rather than the target terminal, nitrides.
The Nottingham team’s method involved using a very ‘bulky’ nitrogen ligand (an organic molecule bonded to a metal) to wrap around the uranium centre and to create a protective pocket in which the nitride nitrogen can sit. The nitride was stabilised during the synthesis by the presence of a weakly bound sodium cation (positively charged ion) which blocked the nitride from reacting with any other elements. In the final stage, the sodium was gently teased away, removing it from the structure and leaving the final, stable uranium nitride triple bond.
via ‘Trophy molecule’ breakthrough.
