Functionalising metal surfaces with N-heterocyclic carbenes

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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.