Functionalising metal surfaces with N-heterocyclic carbenes

自20世纪90年代初首次报道N-杂环卡宾的合成以来，N-杂环卡宾已被广泛应用于修饰均相过渡金属络合物和催化剂的反应活性和选择性。NHC具有作为强Sigma供体和弱pi受体的能力，它们与一系列元素强烈结合，并且与磷酸盐和硫代酸盐相比具有更好的氧化稳定性。此外，NHCS的功能化综合起来也相对容易。在金属纳米颗粒或扩展金属表面上的NHCS的研究日益迅速。表面结合的NHC在生物、电化学和催化等领域具有广阔的应用前景。NHC稳定的Au表面已经被证明比传统的硫酸盐为基础的单分子膜在物理和化学上更坚固。这是一个与凯瑟琳·克鲁登教授和休·霍顿教授(加拿大女王大学)合作的项目。由Crudden团队合成的NHC将在超高真空中蒸气沉积到一系列金属表面(如铜和钯)。用程序升温脱附(TPD)、高分辨电子能量损失谱(HREELS)和扫描隧道显微镜(STM)对化学气相沉积NHC涂层金属表面的热稳定性、分子取向和堆积进行了表征。这些结果将被Horton团队对溶液沉积的NHCs的平行研究所增强。研究了NHC修饰的金属表面在多相催化和缓蚀方面的应用潜力。

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.