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Molecular corking is a phenomenon where a molecule selectively binds to the catalytic atom of a single-atom alloy (SAA) and prevents the recombination of atomized gas molecules at the surface of a metal, functionally trapping them. A necessary feature of a molecular cork is strong, yet reversible binding and thermal stability. There is active experimental and theoretical research on potential candidates, which rank the viability of molecular corks based on their ability to donate electrons into sigma bonds and accept back-donation from the metal via pi bonding. This is often assessed experimentally and computationally using chemical shifts in NMR of selenium and phosphorus adducts as well as other metal complexes. A prime candidate for this purpose are N-heterocyclic carbenes (NHC). However, there have been few studies that perform bond decomposition analysis of periodic quantum mechanical calculations to qualify if the observed chemical shifts in NMR and binding strengths on metals are in fact due to sigma donation and pi back bonding. Moreover, the role of conformational flexibility plays in reported NMR chemical shifts is relatively unexplored. Using periodic vdW-DFT calculations and localized bonding MOs extracted from periodic plane-wave basis sets, along with molecular calculations, we seek to answer these questions for simple, but representative molecular systems bound to Cu-Pd SAA surfaces.
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This content will become publicly available on August 19, 2026
N-heterocyclic carbenes: A versatile molecular family
N-Heterocyclic carbenes (NHCs) are an interesting family of molecules that have potential applications in hydrogen storage via the “molecular corking effect”. Benefits of using NHC backbones as molecular corks include their modularity via functionalization and synthetic diversity. Changing the functional groups can lead to new properties depending on their donation or withdrawal of electron density. Additionally, mono- and di-protonation of the carbene on the various backbones was observed to have significant effects on their proton affinity. We hypothesize that proton affinity can be utilized to understand the sigma donation effects of the evaluated molecules, which are expected to be predictive of the bond strength of an NHC to a surface.
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- Award ID(s):
- 2142874
- PAR ID:
- 10652036
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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