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N ‐Heterocyclic Carbene Self‐assembled Monolayers on Copper and Gold: Dramatic Effect of Wingtip Groups on Binding, Orientation and Assembly
Author(s) -
Larrea Christian R.,
Baddeley Christopher J.,
Narouz Mina R.,
Mosey Nicholas J.,
Horton J. Hugh,
Crudden Cathleen M.
Publication year - 2017
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201701045
Subject(s) - monolayer , chemistry , copper , scanning tunneling microscope , desorption , isopropyl , adsorption , self assembled monolayer , carbene , crystallography , self assembly , photochemistry , stereochemistry , organic chemistry , catalysis , nanotechnology , materials science , biochemistry
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 E des =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) 2 Cu species by extraction of a copper atom from the surface after annealing.