Seeing the Light with Manganese - Unveiling Catalysis by an Earth Abundant Metal

催化剂在现代化学中起着至关重要的作用。从根本上说，它们提高了化学反应的速度和选择性，从而减少了不必要的副产品。随着这一过程效率的提高，化学工业严重依赖催化剂来制备支撑我们现代生活的药品、农用化学品和塑料(仅举几个应用)也就不足为奇了。因此，如果一个过程要以最高的效率运行，那么为给定的反应选择最活跃的催化剂是极其重要的。然而，选择最活跃的催化剂是极其困难的。如果没有详细的实验，就不可能预测哪种化学结构和条件的确切组合将具有最理想的性能。对催化剂如何运行(机理)，特别是如何发生化学键的活化和形成有了详细的了解，这为化学家确定不同的反应物如何与催化剂相互作用提供了重要的见解。通过对机理的全面了解，可以对反应方案和如何改善催化剂的结构做出详细和知情的预测。这项研究计划侧重于使用一种新的方法来研究地壳中丰富的金属催化过程的机理。我们发现了一种研究催化反应的新方法，它有可能彻底改变获得机理洞察力的方式。使用一个基于过渡金属锰的系统，我们已经展示了通常通过强加热活化的催化剂如何在光作用下活化。我们将这种洞察力与时间分辨红外光谱相结合，其中激活催化剂的光是由激光脉冲提供的。紧随其后的第二个激光脉冲(所谓的泵浦-探测延迟)在化学反应期间检查催化剂的结构。由于利用光的过程是高度选择性的，我们产生了高浓度的化学物种，这些化学物种实际上负责反应，因此可以研究它们的行为。到目前为止，我们的研究是在卢瑟福·阿普尔顿实验室的中央激光设施进行的，泵浦探测的延迟从皮秒(万亿分之一秒)到毫秒(百分之一秒)。这让人们对支持锰催化的化学过程有了前所未有的洞察。这项提议旨在以两种方式加强这一独特的洞察力：首先，我们将在约克开发设施，提供补充方法，以检查从一纳秒(十亿分之一秒)到几个小时发生的反应。通过结合不同实验方法的数据，我们将能够研究支撑催化作用的过程，时间超过16个数量级。打个比方，如果我们想象我们测量的最短时间是一秒，那么我们最长的时间应该是14亿年后！其次，我们将开发新的方法，利用光来激活化学反应中不同阶段的一系列不同的催化反应。依靠相关领域的进展，我们将能够启动一系列重要的催化过程，然后研究它们在同样广泛的时间范围内的行为。最后，我们将整合最先进的机器人实验，以加快我们的发现进程。这项计划将带来对反应的新见解，提供有关催化剂行为的独特信息，这是通过其他方式无法获得的。这反过来将允许以知情的方式改善催化剂结构和反应条件，以便使用最有效的系统。

Catalysts play a vital role in modern chemistry. Fundamentally, they increase the speed of a chemical reaction as well as its selectivity, resulting in fewer unwanted byproducts. As this increases the efficiency of a process, it is not surprising that the chemical industry relies heavily on catalysts to prepare the pharmaceuticals, agrochemicals and plastics (to name but a few applications) which underpin our modern lives. The selection of the most active catalyst for a given reaction is therefore extremely important if a process is to operate at peak efficiency. However, the selection of the most active catalyst is incredibly difficult. It is impossible to predict without detailed experimentation which exact combination of chemical structures and conditions will have the most desirable properties. Armed with a detailed understanding of how the catalyst operates (the mechanism) and in particular how chemical bond activation and formation occurs provides important insight for the chemist to determine how the different reactants interact with the catalyst. With a comprehensive view of mechanism, detailed and informed predictions can then be made on the reaction protocol and how to improve the structure of the catalyst.This programme of research focuses on employing a new method to study the mechanisms which underpin processes catalysed by metals that are abundant in the Earth's crust. We have discovered a new method to study catalytic reactions which has the potential to revolutionise how mechanistic insight is obtained. Using a system based on the transition metal manganese, we have shown how a catalyst that is normally activated by strong heating can be activated by light. We have coupled this insight with time-resolved infra-red spectroscopy, in which the light that activates the catalyst is provided by a laser pulse. A second laser pulse, which follows a short time later (the so-called pump-probe delay), then examines the catalyst structure as it reacts during the chemical reaction. As the process of using light is highly selective we generate high concentrations of the chemical species which are actually responsible for the reaction and so can study their behaviour. Our studies so far have been performed at the Central Laser Facility at the Rutherford Appleton Laboratory where pump-probe delays from a picosecond (a trillionth of a second) to a millisecond (a hundredth of a second). This gives unprecedented insight into the chemical process which underpin catalysis by manganese. This proposal aims to build on this unique insight in two ways: Firstly, we will develop facilities in York which provide complementary methods to examine the reactions occurring from a nanosecond (a billionth of a second) to several hours. By combining the data from the different experimental methods we will be able to study the processes which underpin catalysis over 16 orders of magnitude in time. To give an analogy, if we imagined our shortest time measurement was one second, then our longest would be 1.4 billion years later! Secondly, we will develop new methods using light to activate a host of different catalytic reactions at different stages in the chemical reactions. By relying on advancements in a related field that have shown how light can be used as a trigger to selectively activate acids and related groups, we will be able to initiate a host of important catalytic processes and then study their behaviour over the same wide range of timescales.Finally, we will integrate state-of-the-art robotic experimentation to accelerate our discovery process. This programme will result in new insight into reactions, providing unique information about the behaviour of catalysts which cannot be obtained by other means. This will, in turn, permit the catalyst structure and reaction conditions to improved in an informed manner so that the most efficient systems are used.