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

Abstract

A series of chiral Au₁₃ nanoclusters were synthesized via the direct reduction of achiral dinuclear Au(I) halide complexes ligated by ortho-xylyl-linked bis-N-heterocyclic carbene (NHC) ligands. A broad range of functional groups are tolerated as wingtip substituents, allowing for the synthesis of a variety of functionalized chiral Au₁₃ nanoclusters. Single crystal X-ray crystallography confirmed the molecular formula to be [Au₁₃(bisNHC)₅Cl₂]Cl₃, with a chiral helical arrangement of the five bidentate NHC ligands around the icosahedral Au₁₃ core. This Au₁₃ nanocluster is highly luminescent, with a quantum yield of 23%. The two enantiomers of the Au₁₃ clusters can be separated by chiral HPLC, and the isolated enantiomers were characterized by circular dichroism spectroscopy. The clusters show remarkable stability, including configurational stability, opening the door to further investigation of the effect of chirality on these clusters.