Synergistic Effect of Bridging Thiolate and Hub Atoms for the Aromaticity Driven Symmetry Breaking in Atomically Precise Gold Nanocluster

Abstract

The symmetry of atomically precise nanoclusters is influenced by the specific geometry of the kernel and the arrangement of staple motifs. To understanding the role of ligand and its effect on the breaking of symmetry during ligand exchange transformation, it is necessary to have a mechanism of transformation in an atomically precise manner. Herein, we report the structural transformation from bipyramidal kernel to icosahedral kernel via ligand exchange. The transformation of [Au23(CHT)16]− to [Au25(2-NPT)18]− through ligand (aromatic) exchange revealed two important principles. First, the combined effort of experimental and theoretical study on structural analysis elucidated the mechanism of this structural transformation where “bridging thiolate” and “hub” gold atoms play a crucial role. Second, we have found that the higher crystal symmetry of the Au23 cluster is broken to lower crystal symmetry during the ligand exchange process. This showed that during ligand exchange, the hub atoms and μ3-S atoms get distorted and contributed to the ligand-staple motif formation. These phenomena specified that the ligand effects might be the pivotal factor to impose lower symmetry of the crystal system in the product clusters.

Tailoring the Electron–Phonon Interaction in Au25(SR)18 Nanoclusters via Ligand Engineering and Insight into Luminescence

“…The synthesis of Au 25 (PET) 18 – and Au 25 (BM) 18 – followed a previously reported one-pot method . The synthesis of Au 25 (SPh) 18 – and Au 25 (3,5-DMBT) 18 – was achieved by a previously reported ligand-induced structure transformation method …”

Control over Ligand-Exchange Positions of Thiolate-Protected Gold Nanoclusters Using Steric Repulsion of Protecting Ligands

“…Organic ligands on inorganic nanomaterials, such as metal nanoparticles or metal nanoclusters (NCs), play important roles such as in preventing aggregation and tuning interparticle interactions. − More crucial roles of organic ligands emerged by decreasing the size of nanomaterials. Protecting ligands of metal NCs with a size of less than 2 nm affects the structures of NCs because of the high specific surface area of NCs. − Because the physicochemical properties and reactivities of metal NCs are sensitive to their structures, ligand effects on the structures of metal NCs have been investigated by changing the protecting ligands, mainly through ligand-exchange reactions. − In particular, ligand-exchange reactions in atomically precise thiolate-protected gold NCs [denoted Au n (SR) m ] have been investigated because of their variety of physicochemical properties and structures, depending on the thiolate ligands. − For example, the optical properties of Au 25 (SR) 18 , one of the most general and stable gold NCs, can be tuned by changing the thiolate ligands − because of structural deformation of Au 25 clusters. In addition, ligand-exchange-induced structural transformation has also been scrutinized to obtain mechanistic insights into structural changes. ,− In these transformations, intermolecular interactions between the protecting ligands on metal NCs are an important factor in regulating the structures of Au n (SR) m . , Therefore, if precise control over ligand-exchange reactivities is achieved for regulating the interactions between protecting ligands, structural perturbation to obtain desired properties would be possible.…”

Selective formation of [Au23(SPhtBu)17]0, [Au26Pd(SPhtBu)20]0 and [Au24Pt(SC2H4Ph)7(SPhtBu)11]0 by controlling ligand-exchange reaction

“…For such a geometric structure, formation of a core–shell structure with Pd as the core and Au as the shell typically dose not occur. Although the chemical composition of the final product is affected by the reaction path, 63,64 this geometric factor appears to be largely related to the fact that Au 27 Pd(SPh t Bu) 20 and Au 26 Pd 2 (SPh t Bu) 20 were not formed in our experiments.…”