Theoretical predictions and electronic properties of thiolate-protected gold nanocluster: Au44(SR)32

Abstract

Thiolate-protected gold nanoclusters have received extensive attention both experimentally and theoretically due to their excellent physical and chemical properties. However, comprehending the geometric structure of thiolate-protected gold nanoclusters remains a challenging task. Predicting the structural configuration of these ligand-protected gold nanoclusters can enhance our understanding of this class of materials. Due to the current lack of knowledge regarding the structure of Au44(SR)32, we employed the grand unified model (GUM) for gold core stacking and the ring model to describe interfacial interactions between gold cores and the protection motifs. Based on these models, we successfully predicted the geometric structure of Au44(SR)32 clusters and demonstrated partial reproducibility between the calculated absorption spectra and experimental results. Furthermore, by analyzing the energy levels and molecular orbitals, we have identified that the absorption spectra of Au44(SR)32 arise from d→d and d→sp transitions, with the low-energy state primarily resulting from Au44-to-core transitions and the high-energy state from Au44-to-ligand transitions. These findings not only enhance our understanding of Au44(SR)32 clusters but also validate the effectiveness and applicability of GUM and ring model in predicting stable structures of thiolate-protected gold nanoclusters.