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

锕系元素在元素周期表中表现出最多样化的化学性质，其中关键的核燃料循环元素（U， Np和Pu）是最复杂的。在好氧条件下，+VI (U)和+V （Np）氧化态占主导地位，这些formdioxo锕基离子AnO22+具有线性O=An=O键。虽然这些都是众所周知的广泛的配位化学，但最近发现的一些显著特征挑战了对锕基单元（这里是铀酰）的热力学稳定性和动力学惰性的传统观点和理解。锕系元素的氧化还原化学也很复杂；铀酰(V)离子易发生歧化反应，歧化反应涉及铀酰键的活化和氧原子转移反应，但这一过程的机制尚不清楚。本项目旨在通过采用强sigma给体和几何约束的ansa型环戊二烯基配体来探讨铀酰阳离子中的键合，以影响铀酰单元的反应性。这将改变它的电子结构和反应性，我们将通过发光光谱特别探索其氧化还原化学，包括氧原子转移反应，以了解核回收和处置场景中发生的氧化还原过程。具体目标是：-合成一个新的铀酰（VI）配合物家族，与高价氧前体的ansa-Cp型配体配位。-通过光学/振动光谱和DFT计算探测电子结构。-研究氧- cp铀酰配合物与O原子转移试剂的氧原子转移反应的反应活性。-利用紫外和可见光，利用瞬态吸收和超快发射光谱研究ansa-Cp铀酰配合物的光物理性质。-研究铀酰(V)衍生物的合成路线。

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.