N-heterocyclic carbene self-assembled monolayers on copper and gold : dramatic effect of wingtip groups on binding, orientation and assembly
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Self-assembled monolayers of N-heterocyclic carbenes (NHCs) on copper are reported. The monolayer structure is highly dependent on the N,N-substituents on the NHC. On both Cu(111) and Au(111), bulky isopropyl substituents force the NHC to bind perpendicular to the metal surface while methyl- or ethyl-substituted NHCs lie flat. Temperature-programmed desorption studies show that the NHC binds to Cu(111) with a desorption energy of Edes=152±10 kJ mol−1. NHCs that bind upright desorb cleanly, while flat-lying NHCs decompose leaving adsorbed organic residues. Scanning tunneling microscopy of methylated NHCs reveals arrays of covalently linked dimers which transform into adsorbed (NHC)2Cu species by extraction of a copper atom from the surface after annealing.
Larrea , C R , Baddeley , C J , Narouz , M R , Mosey , N J , Horton , J H & Crudden , C M 2017 , ' N-heterocyclic carbene self-assembled monolayers on copper and gold : dramatic effect of wingtip groups on binding, orientation and assembly ' ChemPhysChem , vol 18 , no. 24 , pp. 3536–3539 . DOI: 10.1002/cphc.201701045
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Funding: EPSRC PhD studentship (EP/M506631/1).
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