Structure-control of valence electron isomerism in the f-block

f-嵌段中价电子异构的结构控制

• 批准号: EP/Y006534/1
• 负责人: Conrad Goodwin
• 金额: $ 74.24万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FY006534%2F1
• 关键词: Structure; control; valence; electron; isomerism

The valence electron configuration of a metal describes the relative ordering and properties of the highest-energy electrons - those that are available for bonding with other elements, and thus it is these which largely dictate the physicochemical properties of metal-containing materials. For much of the Periodic Table, some known principles can guide the design criteria needed to produce a given electron configuration of the element in question and result in desirable properties. The oxidation state of the metal - the (formal) number of electrons the metal has lost versus the neutral configuration, and the geometry of bound ligands are two of the most important features which can be controlled. This project seeks to develop the redox chemistry of the lanthanides, and early actinide (thorium, uranium, neptunium, plutonium) elements towards a deeper understanding of the design criteria which dictate the valence electron configurations of these metals in lower oxidation states.Lanthanide and actinide elements (the f-block) occupy a position in the Periodic Table where the valence electrons in metal ions reside in highly angular 4f- and 5f-orbitals, which show poor radial extent and thus the bonding between these elements and others is typically quite weak. It is these characteristics which engender the unique physical properties typical of these metals (e.g. applications in magnetism and optical spectroscopy). Simply, a 3+ metal ion in a molecule may have f n valence electrons, where n is three less than the neutral configuration, and there is little which may be done to change the chemical properties of the remaining f-electrons substantially (though their physics may be altered).Developments the chemistry of f-block redox chemistry over the last 20 years have produced examples of all the lanthanides (except Pm), as well as thorium, uranium, neptunium, and plutonium in the 2+ oxidation state, many of these for the first time. This remarkable pace of advancement has overturned many preconceptions about the redox properties of these elements, but has raised questions that this project seeks to address.For some elements, the valence electron configuration of 2+ ions follows the example above with f n+1 valence electrons where n is three less than the neutral atomic configuration. Samarium, europium and ytterbium are examples of this and are often termed "traditional" 2+ lanthanide ions due to this behaviour. For other elements (such as cerium), all examples of molecular 2+ complexes feature an electron configuration described as: f n d1, where n is still three less than the neutral atomic configuration, and one electron resides in a d-orbital (for cerium 2+: f1 d1). As d-orbitals are fundamentally different to f-orbitals (larger radial extent, more diffuse, different magnetic properties), the physicochemical properties of cerium 2+ molecules (which have two metal valence electrons - f1 d1), should differ substantially from molecules with praseodymium 3+ which also features two metal valence electrons (f2). Some elements such as uranium have been shown to accommodate both types of electron configuration in the 2+ oxidation state: f n+1, and also f n d1. The underlying properties which drive the preference for one configuration over the other are poorly known, and is an under explored topic at the forefront of synthetic chemistry.This project will produce examples across the f-block of metal 2+ compounds, determine their valence electron configurations, and use a combination of magnetic and spectroscopic techniques to identify the properties which direct the formation and stability of specific configurations. These results will have applications in the fields of spintronics and quantum technologies which rely on the control of spins by developing new routes to giant molecular spins, and produce fundamental advances in f-block coordination chemistry foundational to future advances in their reactivities.

金属的价电子构型描述了最高能量电子的相对有序性和性质，这些电子可用于与其他元素键合，因此这些电子在很大程度上决定了含金属材料的物理化学性质。对于元素周期表的大部分，一些已知的原理可以指导产生所讨论的元素的给定电子构型所需的设计标准，并产生期望的性质。金属的氧化态-金属相对于中性构型失去的（形式）电子数，以及结合配体的几何形状是可以控制的两个最重要的特征。这个项目旨在发展镧系元素和早期锕系元素的氧化还原化学（钍，铀，镎，钚）元素的设计标准，决定了这些金属在较低的氧化态的价电子配置的更深入的理解。镧系元素和锕系元素（f区）占据周期表中的位置，其中金属离子中的价电子位于高角度的4f和5 f轨道中，其表现出较差的径向范围，因此这些元件和其它元件之间的结合通常非常弱。正是这些特性产生了这些金属特有的独特物理性质（例如在磁性和光谱学中的应用）。简单地说，分子中的3+金属离子可以具有f-n价电子，其中n比中性构型小3，并且几乎不可能实质上改变剩余f-电子的化学性质（尽管它们的物理性质可能会改变）。在过去的20年里，f区氧化还原化学的发展已经产生了所有镧系元素的例子。（除了Pm），以及钍，铀，镎和钚的2+氧化态，其中许多是第一次。这一惊人的进展速度推翻了许多关于这些元素氧化还原性质的成见，但也提出了本项目试图解决的问题。对于某些元素，2+离子的价电子构型遵循上面的例子，具有f n+1个价电子，其中n比中性原子构型小3。钐、铕和镱就是这样的例子，由于这种行为，它们通常被称为“传统的”2+镧系元素离子。对于其他元素（如铈），所有2+配合物的电子构型都描述为：f n d1，其中n仍然比中性原子构型小3，并且一个电子位于d轨道（对于铈2+：f1 d1）。由于d-轨道与f-轨道根本不同（更大的径向范围，更扩散，不同的磁性），铈2+分子（具有两个金属价电子- f1 d1）的物理化学性质应该与具有Praseo 3+的分子有很大不同，Praseo 3+也具有两个金属价电子（f2）。有些元素，如铀，在2+氧化态下可以容纳两种类型的电子构型：f n+1和f n d1。该项目将产生金属2+化合物f-区的例子，确定它们的价电子构型，并使用磁性和光谱技术的组合来识别指导特定构型形成和稳定性的性质。这些结果将在自旋电子学和量子技术领域中得到应用，这些技术依赖于通过开发巨大分子自旋的新途径来控制自旋，并在f-区配位化学中产生根本性的进展，这是其反应性未来发展的基础。