Development of a Dynamic Nuclear Polarisation based NMR techniques for the rapid detection and characterisation of reaction intermediates.

开发基于动态核极化的 NMR 技术，用于快速检测和表征反应中间体。

• 批准号: EP/F022530/1
• 负责人: S Duckett
• 金额: $ 33.75万
• 依托单位: University of York
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FF022530%2F1
• 关键词: Development; Dynamic; Nuclear; Polarisation; based

Project SummarySummary Catalysis mediated by compounds of the transition metal elements is an extremely important area of inorganic chemistry and is the corner stone of virtually the entire chemicals industry. Central to the ability to refine and optimise any catalytic system is a detailed knowledge of the pathways by which the reaction proceeds. One technique commonly used in the study of these types of reaction and for the observation of catalytic intermediates is nuclear magnetic resonance (NMR) spectroscopy. This technique utilises the phenomenon of nuclear magnetism to detect molecules containing atoms with magnetically active nuclei. Nuclei of isotopes such as 1H, 13C, 15N and 31P can therefore be thought of as tiny bar magnets. When placed in the field of a strong magnet, such as that found inside an NMR spectrometer, the bar magnets can either align to reinforce or oppose the main field with the result that states of differing energies are produced. Transitions between these states can be achieved by the absorption of radio frequency signals. These frequencies are a characteristic feature of the chemical environment of the nuclei and ultimately can be used to identify the contributing compound. The sensitivity of this technique is however greatly limited.In this project we will utilise a new technique called dynamic nuclear polarisation (DNP) to increase the sensitivity of the NMR method by a factor that will approach 10,000 and allow the detection and characterisation of low concentration reactive compounds that would otherwise not be observable. Our aim is to established procedures and methodologies that will allow us to sensitise by DNP a suitable precursor substrate compound that subsequently undergoes chemical reactions, using the NDP derived signals as a probe to detect that passage of the substrate through transient intermediates involved in the reaction mechanism. This will enable us follow their reactivity and gain an understanding of the sequence of fundamental reaction steps involved in the catalytic cycle.In order to achieve this however, new NMR experiments must be designed in order to efficiently utilise the signal generated by the DNP method involving the implementation of state-of-the-art rapid scan (in collaboration with Prof Frydman of the Weizmann Institute, Israel) and selective observation methods. We will also need to design and build a sampling handling system that mixes the DNP sensitised materials with other compounds involved in the reaction of study and delivers the reaction mixture in a controlled manner into the region of the NMR spectrometer where measurements will be taken.We will first target simple reactions involving metal containing compounds that yield stable products as a testing ground for these new techniques and will then follow onto to study catalytic reactions. Our initial choice of system is the widely used alkene metathesis reaction catalysed by Grubb's catalyst (Nobel prize 2005) using DNP sensitised alkenes to probe the metallic compounds involved in the catalytic reaction mechanism. Some of the intermediates have already been observed an identified but much work can still be achieved. Therefore this system acts as an ideal proving ground for these methods. Later will be extend our study to another high value reaction, the Heck reaction and focus on the system catalysed by palladium containing P,C-palladcyclic complexes. Here, very little is known about the exact mechanism of operation or the route by which the catalyst is activated.This work will have significant impact, not only on the immediate catalytic chemistry community, but the techniques developed will also have spin-off applications in other fields such as biological NMR research and other areas of analytical chemistry where limited sample size is a major problem.

项目概述过渡金属元素化合物催化是无机化学的一个极其重要的领域，几乎是整个化学工业的基石。精炼和优化任何催化系统的能力的核心是对反应进行的路径的详细了解。研究这些类型的反应和观察催化中间体的一种常用技术是核磁共振(核磁共振)光谱。这项技术利用核磁现象来检测含有具有磁性活性核的原子的分子。因此，1H、13C、15N和31P等同位素的原子核可以被认为是微小的条形磁铁。当放置在强磁铁的磁场中时，如在核磁共振光谱仪中发现的那样，条形磁铁可以对准以加强或对抗主场，结果是产生不同能量的状态。这些状态之间的转换可以通过吸收射频信号来实现。这些频率是核化学环境的一个特征，最终可用于识别贡献化合物。然而，这项技术的灵敏度是非常有限的。在这个项目中，我们将使用一种名为动态核极化(DNP)的新技术，将核磁共振方法的灵敏度提高到接近10,000倍，并允许检测和表征原本无法观察到的低浓度活性化合物。我们的目标是建立程序和方法，使我们能够用DNP敏化合适的前体底物化合物，然后进行化学反应，使用NDP衍生的信号作为探针来检测底物通过参与反应机制的瞬时中间体的通道。这将使我们能够跟踪它们的反应性，并了解催化循环中涉及的基本反应步骤的顺序。然而，为了实现这一点，必须设计新的核磁共振实验，以便有效地利用DNP方法产生的信号，该方法涉及实施最先进的快速扫描(与以色列魏兹曼研究所的Frydman教授合作)和选择性观察方法。我们还需要设计和建立一个采样处理系统，将DNP敏感材料与参与研究反应的其他化合物混合，并以受控的方式将反应混合物输送到核磁共振光谱仪的区域进行测量。我们将首先针对涉及产生稳定产品的金属化合物的简单反应作为这些新技术的试验场，然后再研究催化反应。我们最初选择的体系是广泛使用的由格拉布的催化剂(2005年诺贝尔奖)催化的烯烃歧化反应，使用DNP敏化的烯烃来探索催化反应机理中涉及的金属化合物。一些中间体已经被观察和鉴定，但仍有许多工作要完成。因此，该系统为这些方法提供了一个理想的试验场。以后我们将把研究扩展到另一个高价值的反应--Heck反应，并重点研究含钯的P，C-齐聚环配合物催化体系。在这里，人们对催化剂的确切操作机制或活化途径知之甚少。这项工作不仅将对直接催化化学界产生重大影响，而且所开发的技术还将在其他领域产生副产品应用，如生物核磁共振研究和其他分析化学领域，在这些领域，样品容量有限是一个主要问题。

项目成果

Investigating pyridazine and phthalazine exchange in a series of iridium complexes in order to define their role in the catalytic transfer of magnetisation from para-hydrogen.

• DOI: 10.1039/c5sc00756a
• 发表时间: 2015-07-01
• 期刊: Chemical science
• 影响因子: 8.4
• 作者: Appleby KM;Mewis RE;Olaru AM;Green GGR;Fairlamb IJS;Duckett SB
• 通讯作者: Duckett SB

Improving the hyperpolarization of (31)P nuclei by synthetic design.

通过合成设计改善（31）P核的超极化。

• DOI: 10.1021/acs.jpcb.5b00686
• 发表时间: 2015-04-16
• 期刊: JOURNAL OF PHYSICAL CHEMISTRY B
• 影响因子: 3.3
• 作者: Burns, Michael J.;Rayner, Peter J.;Green, Gary G. R.;Highton, Louise A. R.;Mewis, Ryan E.;Duckett, Simon B.
• 通讯作者: Duckett, Simon B.

Improving NMR and MRI sensitivity with parahydrogen.

使用仲氢提高 NMR 和 MRI 灵敏度。

• DOI: 10.1007/128_2012_388
• 发表时间: 2013
• 期刊: Topics in current chemistry
• 影响因子: 8.6
• 作者: Duckett SB