Spectroscopic and Computational Evidence of Intramolecular AuI⋅⋅⋅H+−N Hydrogen Bonding

Abstract

AbstractDespite substantial evidence of short Au⋅⋅⋅H−X contacts derived from a number of X‐ray structures of AuI compounds, the nature of AuI⋅⋅⋅H bonding in these systems has not been clearly understood. Herein, we present the first spectroscopic evidence for an intramolecular AuI⋅⋅⋅H+−N hydrogen bond in a [Cl−Au−L]+ complex, where L is a protonated N‐heterocyclic carbene. The complex was isolated in the gas phase and characterized with helium‐tagging infrared photodissociation (IRPD) spectra, in which H+−N‐mode‐derived bands evidence the intramolecular AuI⋅⋅⋅H+−N bond. Quantum chemical calculations reproduce the experimental IRPD spectra and allow to characterize the intramolecular Au⋅⋅⋅H+−N bonding with a short rAu⋅⋅⋅H distance of 2.17 Å and an interaction energy of approximately −10 kcal mol−1. Various theoretical descriptors of chemical bonding calculated for the Au⋅⋅⋅H+−N interaction provide strong evidence for a hydrogen bond of moderate strength.