Temperature dependent chiroptical response of sigmoidal gold clusters: probing the stability of chiral metal clusters.

The stability of chiral metal clusters is of great importance for their practical applications. Herein we select three structurally well-defined gold cluster compounds to probe how structural factors influence the stability of chiral metal clusters upon heating. Through monitoring the variation of CD, UV-vis and NMR spectra at elevated temperatures, the biased chiroptical response of three sigmoidal Au6 clusters is finally ascribed to the synergistic effect of the distinct structural tunability of central diamino ligands, inter-cluster aurophilic interactions and steric hindrance. The rigid skeleton of chiral ligands and the strong metal-metal interaction effectively enhance the stability of asymmetric structural motifs in chiral metal clusters. In addition, some central diamino ligands lead to a destructive decomposition of corresponding chiral clusters in the heating process due to the reduction of Au(i) to Au(0). The relationship between structural characteristics and the stability of chiral clusters addressed in this study will facilitate our understanding on how to achieve stable chiral metal clusters and potentiate their practical applications.