Modulating the reactivity of uranyl by manipulating the O=U=O bond angle in uranyl ansa-type cyclopentadienyl complexes

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The actinide elements display some of the most diverse chemistry encountered anywhere in the Periodic Table, with the key nuclear fuel cycle elements (U, Np and Pu) being the most complex. In aerobic conditions, the +VI (U) and +V (Np) oxidation states dominates and these formdioxo actinyl ions AnO22+ with linear O=An=O bonds. While these have well known andextensive coordination chemistry, there are some remarkable features that have been recentlydiscovered challenging the traditional view and understanding of the thermodynamic stability andkinetic inertness of the actinyl unit (here, uranyl). The redox chemistry of the actinides is also complex;uranyl(V) ions are susceptible to disproportionation and these reactions involve activation of the uranyl bond and oxygen atom transfer reactions, yet the mechanisms for such processes remain unclear. This project aims to probe the bonding in the uranyl cation by employing strongly sigma donating and geometrically constrained ansa-type cyclopentadienyl ligands to influence the reactivity of the uranyl unit. This will alter its electronic structure and reactivity, where we will probe its redox chemistry by luminescence spectroscopy in particular, including oxygen atom transfer reactions, to understand redox processes that occur in nuclear recycle and disposal scenarios.Specific aims are to:- Synthesise a new family of uranyl(VI) complexes coordinated to ansa-Cp type ligands from high valent oxo precursors.- Probe of the electronic structure by optical/ vibrational spectroscopies and DFT calculations.- Investigate the reactivity of the ansa-Cp uranyl complexes for oxygen atom transfer reactions with O atom transfer reagents.- Investigate the photophysics of the ansa-Cp uranyl complexes using UV and visible light using transient absorption and ultrafast emission spectroscopies.- Investigate synthetic routes to uranyl(V) derivatives.