Directing Intrinsic Chirality in Gold Nanoclusters: Preferential Formation of Stable Enantiopure Clusters in High Yield and Experimentally Unveiling the “Super” Chirality of Au$_{144}$

Abstract

Chiral gold nanoclusters offer significant potential for exploring chirality at a fundamental level and for exploiting their applications in sensing and catalysis. However, their widespread use is impeded by low yields in synthesis, tedious separation procedures of their enantiomeric forms, and limited thermal stability. In this study, we investigated the direct synthesis of enantiopure chiral nanoclusters using the chiral ligand 2-MeBuSH in the fabrication of Au$_{25}$, Au$_{38}$, and Au$_{144}$ nanoclusters. Notably, this approach leads to the unexpected formation of intrinsically chiral clusters with high yields for chiral Au$_{38}$ and Au$_{144}$ nanoclusters. Experimental evaluation of chiral activity by circular dichroism (CD) spectroscopy corroborates previous theoretical calculations, highlighting the stronger CD signal exhibited by Au$_{144}$ compared to Au$_{38}$ or Au$_{25}$. Furthermore, the formation of a single enantiomeric form is experimentally confirmed by comparing it with intrinsically chiral Au$_{38}$(2-PET)$_{24}$ (2-PET: 2-phenylethanethiol) and is supported theoretically for both Au$_{38}$ and Au$_{144}$. Moreover, the prepared chiral clusters show stability against diastereoisomerization, up to temperatures of 80°C. Thus, our findings not only demonstrate the selective preparation of enantiopure, intrinsically chiral, and highly stable thiolate-protected Au nanoclusters through careful ligand design but also support the predicted “super” chirality in the Au$_{144}$ cluster, encompassing hierarchical chirality in ligands, staple configuration, and core structure