New structural insights into the stability of Au22(SR)16 nanocluster under ring model guidance

Abstract

This study presents thorough structural insights into the stability of crystallized Au₂₂(SAdm)₁₆ (HSAdm = 1-adamantanethiol) nanocluster. With the recently developed Ring Model for describing the interaction between inner gold cores and outer protecting ligands in thiolate-protected gold nanoclusters, the experimental spontaneous transformation from the crystallized Au₂₂(SAdm)₁₆ to Au₂₁(SAdm)₁₅ could be well understood as structurally unfavorable for the current Au₂₂(SAdm)₁₆ and could also be attributed to the weaker aurophilic interaction between the inner Au₄ core and the surrounding rings in Au₂₂(SAdm)₁₆ over that in Au₂₁(SAdm)₁₅. Furthermore, with the Ring Model and the grand unified model, two new Au₂₂(SCH₃)₁₆ isomers with evident lower energies, higher HOMO–LUMO gaps as well as distinct optical properties over the available crystallized isomer were obtained. This study deepens the current knowledge on the structure of the Au₂₂(SR)₁₆ cluster from a new structural point of view and also confirms the validity as well as practicability of the Ring Model in understanding and predicting the stable structures of thiolate-protected gold nanoclusters.