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，从而减少了不需要的副产物。由于这提高了一个过程的效率，因此毫不奇怪，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（仅举几例）。因此，如果一个过程要以最高效率运行，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非常困难的。没有详细的实验，就不可能预测化学结构和条件的确切组合会产生最理想的性质。对催化剂如何运作（机制），特别是化学键如何激活和形成的详细了解，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。有了对机理的全面了解，就可以对反应方案和如何改进催化剂结构进行详细和知情的预测。这个研究方案的重点是采用一种新方法来研究由地壳中丰富的金属催化的过程的机制。我们已经发现了一种研究催化反应的新方法，它有可能彻底改变如何获得机械洞察力。使用基于过渡金属锰的系统，我们展示了通常由强加热激活的催化剂如何被光激活。我们将这种见解与时间分辨红外光谱学结合起来，其中激活催化剂的光是由激光脉冲提供的。第二个激光脉冲，在很短的时间之后（所谓的泵-探针延迟），然后检查在化学反应中反应的催化剂结构。由于使用光的过程是高度选择性的，我们产生高浓度的化学物质，这些化学物质实际上负责反应，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备上进行的，泵浦探测器的延迟从皮秒（万亿分之一秒）到毫秒（百分之一秒）不等。这使人们对锰催化作用的化学过程有了前所未有的了解。该提案旨在以两种方式建立这种独特的见解：首先，我们将在约克开发设施，提供补充方法来检查从纳秒（十亿分之一秒）到几个小时发生的反应。通过结合来自不同实验方法的数据，我们将能够在时间上研究超过16个数量级的催化过程。打个比方，如果我们想象我们最短的时间是一秒，那么最长的时间将是14亿年之后！其次，我们将开发新的方法，利用光在化学反应的不同阶段激活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，然后在相同的时间尺度范围内研究它们的行为。这些进展已经表明，光可以作为一个触发器，选择性地激活酸和相关基团。最后，我们将整合最先进的机器人实验来加速我们的发现过程。该程序将导致对反应的新见解，提供有关催化剂行为的独特信息，这些信息无法通过其他方法获得。反过来，这将使催化剂结构和反应条件以知情的方式得到改善，从而使用最有效的系统。

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.