Interfaces of Ionic Liquid Systems

离子液体是一种熔点低于100℃的熔盐。它们结构的多样性导致了结合不同性质的阳离子和阴离子几乎无限的可能性。这就允许在大范围内调整其物理化学性质，并使其适应特定的应用。在最初关注IL的体性质之后，IL与其环境的界面的重要性也在许多应用领域得到了认可，特别是在催化方面的新概念。由于它们的蒸气压低，离子液体可以通过超高真空的方法进行研究，离子液体表面科学领域在过去几年中已经开始建立起来。申请人小组对这一发展做出了重大贡献，特别是使用角度分辨x射线光电子能谱。然而，虽然目前可用的研究包含特定系统的特定属性的信息，但仍然缺乏潜在机制和驱动力的总体图景。对IL/气体（真空）和IL/固体界面以及IL多相系统中的过程的性质的过程和机制缺乏基本的理解，这决定了本项目的阶段：将研究四个具体主题：1)表面组成、取向和富集效应的温度依赖性；研究了IL表面的分子取向，二元IL混合物的表面组成，以及体积液-液相变对表面取向的影响。这些效应的温度依赖性在许多应用中都是至关重要的，但到目前为止，在表面相关的研究中大多被忽视。2)金属配合物的溶解：旨在发展一般概念，以克服许多金属配合物在il中的低溶解度，并控制这些配合物的表面活性。我们将应用具有il型基团的配合体，并研究含金属配合物的il。3)离子液体/载体相互作用：关注IL与固体载体或与第二IL表面的界面，利用由成熟的和新的原位技术从气相沉积的超薄IL膜。4)监测离子液体体系中的化学反应：利用x射线光电子能谱进行现场监测的潜力。我们将讨论il之间的反应，il中游离碱卟啉的金属化，以及il中气态小分子和溶解金属配合物的吸附和反应。

Ionic liquids (ILs) are molten salts with a melting point below 100°C. Their structural diversity results into nearly unlimited possibilities to combine cations and anions with different properties. This allows tailoring their physico-chemical properties over a wide range and adapting them to specific applications. After an initial focus on the bulk properties of ILs, the importance of the interface of an IL with its environment has also been recognized for a large number of application areas, in particular also for new concepts in catalysis. Due to their low vapour pressure, ILs can be investigated by ultrahigh vacuum-based methods and the area of Ionic Liquid Surface Science has started to establish itself within the last years. The applicants group has significantly contributed to this development, in particular using angle-resolved X-ray photoelectron spectroscopy. However, while the presently available studies contain information on the specific properties of particular systems, a general picture of the underlying mechanisms and driving forces is still missing. This lack of fundamental understanding of processes and mechanisms governing the properties of IL/gas (vacuum) and IL/solid interfaces, and of processes in IL multiphase systems define the stage for this project: Four specific topics will be investigated: 1) Temperature-dependence of surface composition, orientation and enrichment effects: addresses molecular orientation at IL surfaces, surface composition of binary IL mixtures, and the influence of bulk liquid-liquid phase transitions on surface orientation. The temperature dependences of these effects are of pivotal importance for many applications, but up to now have been mostly ignored in surface-related studies. 2) Dissolution of metal complexes: aims at developing general concepts to overcome the low solubility of many metal complexes in ILs and to control surface activity of these complexes. We will apply complex ligands with IL-type moieties and study metal-complex-containing ILs. 3) Ionic liquid/support interactions: concern the interfaces of ILs with solid supports or with the surface of a second IL, making use of ultra-thin IL films deposited by established and new in situ techniques from the gas phase. 4) Monitoring of chemical reactions in ionic liquid-based systems: exploits the potential of X-ray photoelectron spectroscopy for in situ monitoring. We will address reactions between ILs, the metalation of free base porphyrins in ILs, and adsorption and reaction of small gaseous molecules in ILs and at dissolved metal complexes.