Formation Mechanism of Au(SR).

Understanding the formation mechanism is crucial for the synthesis and regulation of thiolate-protected gold nanoclusters at the atomic level. In this study, we elucidate the formation mechanism of a specially structured Au(SR) cluster with a Au(SR) ring. Utilizing density functional theory calculations, we propose an intermolecular coupling and hydrolysis reaction mechanism to elucidate the formation of Au(SR) within the NaBH system. Additionally, we formulate a molecular-like reaction equation to elucidate the size evolution of thiolate-protected gold nanoclusters, ranging from 0 Au(SR) to 4 Au(SR) clusters during the initial nucleation stage of growth. Notably, 0 Au(SR) exhibits a ring-in-ring structure, deviating from the conventional interlocked catenane ring. Furthermore, we delineate the formation pathway of 4 Au(SR), leveraging 0 Au(SR) as a seed based on the bottom-up reaction equation. These systematic investigations into the formation mechanism of 4 Au(SR) are pivotal for comprehending the NaBH reduction and hydrolysis process and elucidating the structure-property relationship of Au(SR). To the best of our knowledge, this represents the great theoretical exploration of the growth pathway from ring-in-ring structures to small gold clusters, offering valuable insights into the precise synthesis of gold clusters.