Development of a Dual-Mode Microwave-EPR Cavity for Studies of Paramagnetic Systems

用于顺磁系统研究的双模微波 EPR 腔的开发

• 批准号: 2227521
• 金额: --
• 依托单位: CARDIFF UNIVERSITY
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2227521
• 关键词: Development; Dual; Mode; Microwave; EPR

There are many challenges in studying the mechanisms and speciation of reactionintermediates in catalytic systems, particularly under in situ conditions. Quite often thelifetime and concentrations of these species are below the detection limits of theinterrogating spectroscopic technique. This is particularly true for paramagneticreaction intermediates. To address these challenges, we are developing a unique dualmodereactor-resonator for Electron Paramagnetic Resonance (EPR) spectroscopy,utilising the incredibly efficient heating capabilities of microwaves (MWs) to generatevolumetric and rapid sample heating (a temperature jump, or TJ, capability), to betterunderstand the proposed role of MWs in enhancing the rate of reactions and chemicaltransformations. The TE102 mode of a conventional EPR cavity (the resonator) willmonitor the EPR signals whilst a lower frequency TE101 mode will be simultaneouslyaccessed via an external CW or pulsed MW source to induce the sample heating (thereactor). The rapid heating offers multiple benefits, not only to accelerate a reaction, butalso to alter the product distribution and proportion of unstable species and therebyenable TJ-relaxation measurements to be performed using EPR spectroscopy.In this experimental project, we will specifically employ the dual mode resonator toinitially study three key application areas. Firstly, the resonator will be utilised toinvestigate the kinetics of exchange reactions in organic radicals, and particularlyexplore the role and behaviour of the solvent in these electron transfer events. Secondly,we will study a series of low valent transition metal ions for MW assisted cross couplingreactions. In some cases, a proposed MW enhancement of reaction products has beenproposed, and we will seek to investigate the fundamental origins of these proposedaccelerations. Finally, we will also examine the reactive species involved in oxidationcatalysis employing cobalt bearing complexes. These complexes are relevant not only tohomogeneous catalysis, but also as model systems for studies of spin-cross overcompounds, which can be manipulated using the variable in situ heating capabilities ofthe resonator.Understanding the chemistry of reactions shifted far from equilibrium is an importantaspiration in the chemical and physical sciences. Although many T-jump perturbationtechniques are available, the benefits of this in situ rapid heating EPR will provide a newcapability to the UK. Whilst a major focal point of this project is the testing of the dualmodereactor-resonator, applied to problems in reaction kinetics and catalysis, it mustbe recognised that the fundamental knowledge of how MWs interact with materialsremains poorly understood, despite the growing use of MW-radiation in syntheticchemical transformations. It must also be stated that catalysis is an important researcharea within the EPSRC portfolio. Therefore, the research in this project will serve tounderpin both of these major challenges and research areas.

在催化体系中，特别是在原位条件下，研究反应中间体的机理和形态存在许多挑战。这些物种的寿命和浓度往往低于询问光谱技术的检测极限。对于顺磁反应中间体尤其如此。为了应对这些挑战，我们正在为电子顺磁共振（EPR）光谱学开发一种独特的双慢速反应器-谐振器，利用微波（mw）令人难以置信的高效加热能力来产生进化和快速的样品加热（温度跳变，或TJ能力），以更好地理解mw在提高反应速率和化学转化方面的作用。传统EPR腔（谐振器）的TE102模式将监测EPR信号，而较低频率的TE101模式将通过外部连续波或脉冲MW源同时进入，以诱导样品加热（反应堆）。快速加热提供了多种好处，不仅可以加速反应，还可以改变产物的分布和不稳定物质的比例，从而使使用EPR光谱进行tj弛豫测量成为可能。在这个实验项目中，我们将专门使用双模谐振器来初步研究三个关键应用领域。首先，谐振器将用于研究有机自由基交换反应的动力学，特别是探索溶剂在这些电子转移事件中的作用和行为。其次，我们将研究一系列用于微波辅助交叉偶联反应的低价过渡金属离子。在某些情况下，已经提出了一种建议的反应产物的MW增强，我们将寻求调查这些提议的加速的基本起源。最后，我们还将研究使用含钴配合物参与氧化催化的活性物质。这些配合物不仅与均相催化有关，而且作为研究自旋交叉过化合物的模型系统，可以使用谐振器的可变原位加热能力来操纵。理解远离平衡的化学反应是化学和物理科学的一个重要目标。尽管有许多t跳摄动技术可用，但这种原位快速加热EPR的优势将为英国提供一种新的能力。虽然这个项目的一个主要焦点是测试双中速反应器-谐振器，应用于反应动力学和催化问题，但必须认识到，尽管在合成化学转化中越来越多地使用mw辐射，但mw与材料相互作用的基本知识仍然知之甚少。必须指出的是，催化是EPSRC投资组合中的一个重要研究领域。因此，本项目的研究将为这些主要挑战和研究领域提供基础。