Advanced applications of SXD in structural evolution in molecular systems, and towards chemical applications of LMX

我们对固体状态下分子结合的方式感兴趣。这可以通过各种有利的相互作用发生，但我们最感兴趣的是氢键，它是这些分子间相互作用中最强的。我们用来进行这些研究的方法是衍射和计算化学。衍射-一种阐明晶体材料内部分子结构的方法-使用X射线（家庭实验室中的常规）和中子（仅在中心设施中可用）进行。我们建议在这里做的工作集中在衍射研究，并包括一个特别强调中子衍射。中子衍射在我们的工作中很重要，因为它提供了确定分子结构中重要氢原子位置的明确方法（一般来说，X射线在这方面要差得多）。由于我们对分子间氢键及其详细行为感兴趣，并且由于氢原子对氢键的形成和理解至关重要，因此在我们的工作中显然需要中子衍射。多年来，我们开展了利用变温单晶衍射测量的广泛研究计划，特别强调应用中子衍射方法研究分子系统中氢原子的行为。我们寻找氢原子的奇怪或有趣的行为，包括它们可能是移动的的情况（质子转移）或以其他方式能够在氢键内调节-如果我们能够调节氢键的性质，我们就可以对材料的性质施加很多控制，甚至包括改变它们的颜色或电学性质等。我们利用氢键创造的结构体系本身就具有有用的性质，例如空腔，我们的部分工作涉及尝试创造具有空腔的分子材料，然后尝试将气体放入这些空腔中，并从中取出，这具有许多潜在的应用。这一切都不容易做到--我们系统的结构化学非常灵活，并不总是适合于精确设计分子结合在一起的方式，但我们有很多技术来增加实现这一点的机会。在我们想做的工作中，我们将这些中子衍射方法应用于一系列具有各种潜在有趣特征的氢键材料。然而，由于我们正在研究结构如何随着条件的变化而变化（例如，如果我们加热或冷却样品，或者如果我们向它施加压力），这对中子衍射来说是一个挑战。事实上，直到最近，这些文书才能够解决这一问题。我们希望在ISIS中子源的SXD仪器上进行的工作已经通过仪器和数据收集技术的开创性进展而成为可能，现在通常允许在几个小时到一天左右的时间内获得我们感兴趣的许多系统的中子单晶衍射数据。作为这项工作的一部分，我们还将研究可能超出升级后的SXD仪器范围的系统，但这些系统将为在ISIS第二目标站上建造的LMX仪器提供重要数据和具有挑战性的目标。学生将参与这个项目，并将有机会在家庭实验室和SXD设施与那里的科学家一起广泛工作，帮助发现结构科学课程中一些令人兴奋的科学，同时也获得了在化学领域使用SXD仪器的经验，这将对我们自己研究这些特定材料的小组之外的化学有用。

We are interested in the way molecules hold together in the solid state. This can happen by various favourable interactions, but the one we are most interested in is hydrogen bonding, which is amongst the strongest of these intermolecular interactions. The methods we use to carry out these studies are diffraction and computational chemistry. The diffraction - a way of elucidating molecular structure inside crystalline materials - is carried out using both X-rays (routine in the home laboratory) and neutrons (only available at central facilities). The work we propose to do here focuses on diffraction studies, and includes a particular emphasis on neutron diffraction. Neutron diffraction is important in our work as it gives the definitive means of locating the important hydrogen atoms in our molecular structures (X-rays are much less good at this in general). Since we are interested in the intermolecular hydrogen bonds and their detailed behaviour, and since hydrogen atoms are vital to the formation and understanding of hydrogen bonds, the need for neutron diffraction in our work is clear.Over many years we have carried out an extensive programme of research exploiting variable temperature single crystal diffraction measurements, with a particular emphasis on applying neutron diffraction methods to the study of hydrogen atom behaviour in molecular systems. We look for odd or interesting behaviour of the hydrogen atoms, including situations where they may be mobile (proton transfer) or otherwise able to be tuned within hydrogen bonds - if we can tune the nature of hydrogen bonds we can exert a lot of control over the properties of materials, even including changing their colour, or electrical properties, etc. In parallel with this, the architecture of the structures we create using hydrogen bonds can have useful properties in themselves, such as cavities, and part of our work involves trying to create molecular materials with cavities and then trying to put gases in and out of these, with many potential applications. None of this is easy to do - the structural chemistry of our systems is very flexible and does not always lend itself to precise design of the way in which molecules hold together, but we have many techniques for increasing our chances of making this happen.In the work we want to do here, we apply these neutron diffraction methods to a range of hydrogen-bonded material that have various potentially interesting features. However, since we are doing to be looking at how structures might change as the conditions are changed (for example if we heat or cool the sample, or if we apply pressure to it), this is a challenge for neutron diffraction. In fact it is only very recently that the instruments - have been capable of tackling this problem. The work we want to do on the SXD instrument at the ISIS neutron source has been made possible by pioneering advances in instrumentation and data collection techniques, which now routinely allow neutron single crystal diffraction data to be obtained in periods from a few hours to a day or so for many of the systems in which we are interested. As part of this work we will also study systems that are probably beyond the scope of even the upgraded SXD instrument, but these will provide important data and challenging targets for the LMX instrument being built on the ISIS Second Target Station.A student will work on this project, and will have the chance to work both in the home laboratory and extensively at the SXD Facility with the scientists there, to help discover some exciting science in the programme of structural science, but also gain experience of using the SXD instrument in the area of chemistry, which will be useful to chemistry beyond out own group studying these specific materials.