Self-Assembled Monolayers of N-Heterocyclic Olefins on Au(111).

Self-assembled monolayers (SAMs) of N-heterocyclic olefins (NHOs) have been prepared on Au(111) and their thermal stability, adsorption geometry, and molecular order were characterized by X-ray photoelectron spectroscopy, polarized X-ray absorption spectroscopy, scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. The strong σ-bond character of NHO anchoring to Au induced high geometrical flexibility that enabled a flat-lying adsorption geometry via coordination to a gold adatom. The flat-lying adsorption geometry was utilized to further increase the surface interaction of the NHO monolayer by backbone functionalization with methyl groups that induced high thermal stability and a large impact on work-function values, which outperformed that of N-heterocyclic carbenes. STM measurements, supported by DFT modeling, identified that the NHOs were self-assembled in dimers, trimers, and tetramers constructed of two, three, and four complexes of NHO-Au-adatom. This self-assembly pattern was correlated to strong NHO-Au interactions and steric hindrance between adsorbates, demonstrating the crucial influence of the carbon-metal σ-bond on monolayer properties. © 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.

Citation

Iris Berg, Luca Schio, Justus Reitz, Elena Molteni, Linoy Lahav, Carolina Gutiérrez Bolaños, Andrea Goldoni, Cesare Grazioli, Guido Fratesi, Max M Hansmann, Luca Floreano, Elad Gross. Self-Assembled Monolayers of N-Heterocyclic Olefins on Au(111). Angewandte Chemie (International ed. in English). 2023 Nov 13;62(46):e202311832

PMID: 37743324

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