N-heterocyclic carbenes on metal surfaces - towards applications in corrosion inhibition and catalysis

这项建议旨在研究N-杂环卡宾(NHCS)在许多重要技术领域的应用，包括缓蚀、金属表面刻蚀和对映体选择性多相催化。这是一个催化表面科学家(Chris Baddeley教授，圣安德鲁斯)与金属有机化学和材料科学专家(Cathy Crudden教授，安大略省女王大学)以及表面和材料化学(Hugh Horton教授，安大略省女王大学)的合作项目。NHC是一类令人兴奋的分子，自20世纪90年代以来已成功地广泛应用于均相催化。最近，人们对使用NHCS稳定过渡金属纳米颗粒和扩展金属表面的兴趣迅速增加。NHCS的一个非常吸引人的特点是它们高度灵活的合成。这使得在NHCS的分子结构中引入官能团以调整其性质变得相对简单。这一领域的一个关键进展是Crudden的小组开发了一系列合成方法来生产碳酸盐形式的稳定的NHCS。我们的工作表明，这种类型的NHC可以在超高真空中蒸气沉积到金属表面(Baddeley)，也可以从溶液中沉积(Horton)。自20世纪80年代以来，金属表面自组装单分子膜(SAM)的产生导致了许多重要的应用。通常，自组装膜由硫代修饰的金表面组成。Crudden和Horton表明，Au上的NHCS在化学和热稳定性方面优于它们的硫酸盐类似物。Baddeley能够测量Au-Carbene键的强度，并表明在硫代自组装膜中它明显强于Au-S键。该项目旨在通过多种方式开发NHC改性金属的化学和热稳定性。Baddeley将使用扫描隧道显微镜、高分辨率电子能量损失光谱和程序升温脱附等补充技术来量化NHC在金属表面的吸附能量，以表征被吸附的NHC分子的取向、堆积和热稳定性。为了将NHCS应用于缓蚀领域，将研究NHCS对氧化物表面的刻蚀能力和对金属表面的钝化能力。手性NHC在金属表面的吸附将被研究，目的是开发对映体选择性的多相催化剂--即能够产生有机分子的一个镜像形式而不是另一个镜像形式的催化剂。对映体选择性催化在制药和农用化学品工业中非常重要，但到目前为止，多相催化剂在工业规模上的影响很小。

This proposal aims to examine the utility of N-heterocyclic carbenes (NHCs) in a number of technologically important areas including corrosion inhibition, etching of metal surfaces and enantioselective heterogeneous catalysis. This is a collaborative project between a catalytic surface scientist (Prof. Chris Baddeley, St Andrews) and experts in organometallic chemistry and materials science (Prof. Cathy Crudden, Queen's University, Ontario) and surface and materials chemistry (Prof. Hugh Horton, Queen's University, Ontario).NHCs are an exciting class of molecules that have been successfully and extensively employed in homogeneous catalysis since the 1990s. There has recently been a rapid increase in interest in the use of NHCs for the stabilisation of transition metal nanoparticles and extended metal surfaces. A very attractive feature of NHCs is their highly flexible synthesis. This makes it relatively straightforward to introduce functionality into the molecular structure of NHCs in order to tailor their properties. A key advance in this area was the development by Crudden's group of synthetic methods to produce bench stable NHCs in the carbonate form. Our work showed that NHCs of this type could be vapour deposited in ultrahigh vacuum onto metal surfaces (Baddeley) as well as being deposited from solution (Horton). Since the 1980s the creation of self-assembled monolayers (SAMs) on metal surfaces has led to many important applications. Commonly, SAMs consist of thiolate modified Au surfaces. Crudden and Horton showed that NHCs on Au outperform their thiolate analogues in terms of chemical and thermal stability. Baddeley was able to measure the strength of the Au-carbene bond and show that it is significantly stronger than the Au-S bond in thiolate SAMs. This project aims to exploit the chemical and thermal stability of NHC modified metals in a number of ways. Baddeley will use the complementary techniques of scanning tunnelling microscopy, high resolution electron energy loss spectroscopy and temperature programmed desorption to quantify the adsorption energy of NHCs on metal surfaces, to characterise the orientation, packing and thermal stability of adsorbed NHC molecules. The ability of NHCs to etch oxide surfaces and to passivate metal surfaces will be investigated with the objective of applying NHCs in the field of corrosion inhibition. The adsorption of chiral NHCs onto metal surfaces will be investigated with the aim of developing enantioselective heterogeneous catalysts - i.e. catalysts capable of producing one mirror image form of an organic molecule and not the other. Enantioselective catalysis is extremely important in the pharmaceutical and agrochemicals industries, but, to date, heterogeneous catalysts have made little impact on an industrial scale.