Enantiopure Chiral Au13 Nanoclusters Stabilized by Ditopic N-Heterocyclic Carbenes: Synthesis, Characterization, and Electrocatalytic Reduction of CO2

A series of chiral Au-13 nanoclusters were synthesized via the direct reduction of chiral dinuclear Au(I) halide complexes ligated by chiral dioxalone-linked bis-N-heterocyclic carbene (bisNHC) ligands. Electrospray ionization mass spectrometry, nuclear magnetic resonance spectroscopy, and density functional theory (DFT) calculations confirmed the molecular formula to be [Au-13(bisNHC)(4)I-4](+), with a chiral arrangement of the four ditopic NHC ligands around the icosahedral Au-13 core. Circular dichroism (CD) spectroscopy of the two enantiomers of the Au-13 clusters shows distinct mirror images of the enantiomers and supports chirality transfer from ligands to the metal core. A plausible model structure was built with the assistance of theoretical analysis, and DFT calculations were employed to explain the origin of the optical and CD activities and their dependence on the binding arrangement of the ditopic bisNHC ligands. The clusters show remarkable stability with minimal decomposition in various solutions both at elevated and room temperatures. The potential of these clusters as nanocatalysts in the electrocatalytic reduction of CO2 to CO is described.