| Autor: |
Kuster L; Department of Chemistry, NanoQAM and Centre Québécois de Matériaux Fonctionnels (CQMF), Université du Québec à Montréal, Montréal, Québec H3C 3P8, Canada. nazemi.ali@uqam.ca., Bélanger-Bouliga M; Department of Chemistry, NanoQAM and Centre Québécois de Matériaux Fonctionnels (CQMF), Université du Québec à Montréal, Montréal, Québec H3C 3P8, Canada. nazemi.ali@uqam.ca., Shaw TE; Department of Chemistry, University of Central Florida, Orlando, Florida 32816, USA., Jurca T; Department of Chemistry, University of Central Florida, Orlando, Florida 32816, USA., Nazemi A; Department of Chemistry, NanoQAM and Centre Québécois de Matériaux Fonctionnels (CQMF), Université du Québec à Montréal, Montréal, Québec H3C 3P8, Canada. nazemi.ali@uqam.ca., Frenette M; Department of Chemistry, NanoQAM and Centre Québécois de Matériaux Fonctionnels (CQMF), Université du Québec à Montréal, Montréal, Québec H3C 3P8, Canada. nazemi.ali@uqam.ca. |
| Abstrakt: |
N -Heterocyclic carbenes (NHCs) have emerged as promising ligands for stabilizing metallic complexes, nanoclusters, nanoparticles (NPs) and surfaces. The carbon-metal bond between NHCs and metal atoms plays a crucial role in determining the resulting material's stability, reactivity, function, and electronic properties. Using Raman spectroscopy coupled with density functional theory calculations, we investigate the nature of carbon-metal bonding in NHC-silver and NHC-gold complexes as well as their corresponding NPs. While low wavenumbers are inaccessible to standard infrared spectroscopy, Raman detection reveals previously unreported NHC-Au/Ag bond-stretching vibrations between 154-196 cm -1 . The computationally efficient r 2 SCAN-3c method allows an excellent correlation between experimental and predicted Raman spectra which helps calibrate an accurate description of NHC-metal bonding. While π-backbonding should stabilize the NHC-metal bond, conflicting reports for the presence and absence of π-backbonding are seen in the literature. This debate led us to further investigate experimental and theoretical results to ultimately confirm and quantify the presence of π-backbonding in these systems. Experimentally, an observed decrease in the NHC's CN stretching due to the population of the π* orbital is a good indication for the presence of π-backbonding. Using energy decomposition analysis - natural orbitals for chemical valence (EDA-NOCV), our calculations concur and quantify π-backbonding in these NHC-bound complexes and NPs. Surprisingly, we observe that NPs are less stabilized by π-backbonding compared to their respective complexes-a result that partially explains the weaker NHC-NP bond. The protocol described herein will help optimize metal-carbon bonding in NHC-stabilized metal complexes, nanoparticles and surfaces. |
