Functionalising metal surfaces with N-heterocyclic carbenes

自20世纪90年代初首次报道其合成以来，N-杂环卡宾（NHC）已被广泛应用于调节均相过渡金属配合物和催化剂的反应性和选择性。NHC具有充当强的σ-供体和弱的π-受体的能力，它们与一系列元素强烈结合，并且与例如膦和硫醇盐相比具有改善的氧化稳定性。此外，在合成上相对容易官能化NHC。金属纳米颗粒或扩展金属表面上的NHC的研究日益迅速。表面结合的NHC在生物学、电化学和催化应用中显示出前景。NHC稳定的Au表面已被证明比传统的基于硫醇盐的单分子膜在物理和化学上更坚固。这是一个与Cathleen Crudden和Hugh Horton教授（加拿大皇后大学）合作的项目。由Crudden小组合成的NHC将在真空中气相沉积到一系列金属表面（例如Cu和Pd）上。通过程序升温脱附（TPD）、高分辨率电子能量损失谱（HREELS）和扫描隧道显微镜（STM）表征通过化学气相沉积制备的NHC覆盖的金属表面的热稳定性、分子取向和堆积。这些结果将通过霍顿小组对溶液沉积的NHC的平行研究得到补充。利用NHC改性的金属表面在多相催化和缓蚀应用的潜力将被检查。

Since the first reports of their synthesis in the early 1990s, N-heterocyclic carbenes (NHCs) have been applied extensively in modifying the reactivity and selectivity of homogeneous transition metal complexes and catalysts. NHCs have the ability to act as strong Sigma-donors and weak pi-acceptors, they bind strongly to a range of elements and have improved oxidative stability compared to e.g. phosphines and thiolates. In addition, it is synthetically relatively easy to functionalise NHCs. Studies of NHCs on metal nanoparticles or extended metal surfaces are increasingly rapidly. Surface bound NHCs have shown promise in biological, electrochemical and catalytic applications. NHC stabilised Au surfaces have been shown to be more physically and chemically robust than traditional thiolate-based monolayers. This is a collaborative project with Professors Cathleen Crudden and Hugh Horton (Queen's University, Canada). NHCs synthesised by Crudden's group will be vapour deposited in ultrahigh vacuum onto a range of metal surfaces (e.g. Cu and Pd). The thermal stability, molecular orientation and packing of NHC covered metal surfaces prepared by chemical vapour deposition will be characterised by temperature programmed desorption (TPD), high resolution electron energy loss spectroscopy (HREELS) and scanning tunnelling microscopy (STM). These results will be augmented by parallel studies of solution deposited NHCs by Horton's group. The potential to exploit NHC modified metal surfaces for applications in heterogeneous catalysis and corrosion inhibition will be examined.