Open AccessSpectroscopic Evidence for a Covalent Sigma Au–C Bond on Au Surfaces Using 13C Isotope Labeling
Author(s) -
Huaiguang Li,
Gabriel Kopiec,
Frank Müller,
Frauke Nyßen,
Kyoko Shimizu,
Marcel Ceccato,
Kim Daasbjerg,
Nicolas Plumeré
Publication year - 2021
Publication title -
jacs au
Language(s) - English
Resource type - Journals
ISSN - 2691-3704
DOI - 10.1021/jacsau.0c00108
Subject(s) - covalent bond , raman spectroscopy , chemistry , magic angle spinning , crystallography , nuclear magnetic resonance spectroscopy , materials science , stereochemistry , organic chemistry , physics , optics
The Au-C linkage has been demonstrated as a robust interface for coupling thin organic films on Au surfaces. However, the nature of the Au-C interaction remains elusive up to now. Surface-enhanced Raman spectroscopy was previously used to assign a band at 412 cm -1 as a covalent sigma Au-C bond for films generated by spontaneous reduction of the 4-nitrobenzenediazonium salt on Au nanoparticles. However, this assignment is disputed based on our isotopic shift study. We now provide direct evidence for covalent Au-C bonds on the surface of Au nanoparticles using 13 C cross-polarization/magic angle spinning solid-state NMR spectroscopy combined with isotope substitution. A 13 C NMR shift at 165 ppm was identified as an aromatic carbon linked to the gold surface, while the shift at 148 ppm was attributed to C-C junctions in the arylated organic film. This demonstration of the covalent sigma Au-C bond fills the gap in metal-C bonds for organic films on surfaces, and it has great practical and theoretical significance in understanding and designing a molecular junction based on the Au-C bond.