Chiroptical activity of Au₁₃ clusters: experimental and theoretical understanding of the origin of helical charge movements

Abstract

Ligand-protected gold clusters with an asymmetric nature have emerged as a novel class of chiral compounds, but the origins of their chiroptical activities associated with helical charge movements in electronic...

Synthesis and enantioseparation of chiral Au13 nanoclusters protected by bis-N-heterocyclic carbene ligands

“…These clusters have a similar icosahedral structure to previously reported Au 13 clusters, including those ligated by monodentate, 18 bis-NHC 19 and bisphosphine ligands. 11 A variety of wingtip groups were compatible with nanocluster formation, allowing for the isolation of clusters incorporating diverse functionality (3c-e). The chirality of cluster 3a in the solid-state was investigated by X-ray crystallography, where it was discerned that chirality results from a helical arrangement of the surface ligands that is dictated by the choice of a bidentate ligand.…”

“…10 Smaller Au 13 nanoclusters can also be prepared with achiral phosphine ligands depending on their orientation around the core. Shichibu and Konishi described this situation for [Au 13 (dppe) 11 in which the ve dppe ligands take up a propeller-like arrangement. 12 However, successful resolution of the individual enantiomers by chiral HPLC was not achieved, possibly due to fast racemization of these clusters in solution.…”

“…S1 †). 11,18 The molecular formula of the cluster [3a]Cl 3 was conrmed by ESI-MS, which showed a dominant molecular ion peak at 1741.26 m/z corresponding to [Au 13 (bisNHC Bn ) 5 Cl 2 ] 3+ (Fig. 2B).…”

“…Shichibu and Konishi described this situation for [Au 13 (dppe) 5 Cl 5 ] 3+ (dppe = 1,2-bis(diphenylphosphino)ethane), 11 in which the five dppe ligands take up a propeller-like arrangement. 12 However, successful resolution of the individual enantiomers by chiral HPLC was not achieved, possibly due to fast racemization of these clusters in solution. The only examples of resolvable chiral Au clusters stabilized by phosphine ligands require the use of inherently chiral ligands.…”

A Review of State of the Art in Phosphine Ligated Gold Clusters and Application in Catalysis

“…Torsional twist of the two pentagonal, equatorial Au 5 rings in the Au 13 core, characterized by the torsional angle, 𝜃, leading to the achiral or chiral nature. Reproduced with permission [219]. Copyright 2021, Royal Society of Chemistry.…”