Thiolate-Protected Au₂₀(SR)₁₆ Cluster: Prolate Au₈ Core with New [Au₃(SR)₄] Staple Motif

Abstract

The precise atomic structure of the recently synthesized "magic cluster" Au(20)(SR)(16) is predicted using ab initio calculations and global-minimum searches. The cluster contains a prolate Au(8) core and four level-3 extended staple motifs (-RS-Au-RS-Au-RS-Au-RS-). The simulated optical absorption spectra of the lowest-energy structures are in good agreement with the measured spectrum. The Au(20)(SR)(16) cluster, with a low Au/SR ratio of 1.25:1, may represent a structural evolution from core-free homoleptic clusters [Au(SR)](N) to core-stacked clusters.

Au13(8e): A secondary block for describing a special group of liganded gold clusters containing icosahedral Au13 motifs

“…Such a secondary block, noted as Au 13 10 Cl 2 ] 1+ decrease from +3 to +1 with the increase of the number of secondary blocks Au 13 (8e) from 1 to 3. Based on this trend, a new cluster, Au 49 (PR 3 ) 10 (SR) 15 Cl 2 with four secondary blocks Au 13 (8e), is predicted.…”

“…[1][2][3][4] From 1970s to the present, a large number of liganded gold nanoclusters have been synthesized and their structures have been determined via X-ray crystallography [5][6][7][8][9][10] or predicted by density functional theory (DFT) computation. [11][12][13][14][15][16][17] Although total structural determination and prediction of numerous ligand-protected gold nanoclusters have been accomplished, understanding of structural stabilities and evolution of many seemingly-unrelated structures of the liganded gold nanoclusters remains to be an active area of research. In 1970s, the Wade-Mingos electron-counting rule was proposed and later employed in the cluster chemistry.…”

“…Such a generic rule of thumb can be used to characterize the stabilities and structural evolution of liganded gold clusters. Among the 71 ligand-protected clusters, there is a special group of liganded gold nanoclusters all containing one or several icosahedral Au 13 Figure S1. The AdNDP analysis ( Figure S2) also confirms that the Au 13 (8e) can be decomposed into four elementary blocks.…”

“…The AdNDP analysis ( Figure S2) also confirms that the Au 13 (8e) can be decomposed into four elementary blocks. Note that this decomposition is not intended to reflect the electronic structure of the Au 13 core at the molecular level ( Figure S3) but simply to indicate that the 8e valence electrons of Au 13 (8e) can be viewed as a sum of four pairs of valence electrons of the four elementary blocks. The elementary blocks Au 3 (2e) and Au 4 (2e) can be also viewed as electron shell closure species, in analogue of that of the stable He atom.…”

“…As such, 91 variants of valence states (named as I 1 -I 91 ) for the secondary block Au 13 (8e) can be identified (see Table S1). In addition, the structural evolution of [Au 13 15 Cl 2 is predicted based on the structural trend obtained with the three experimentally synthesized clusters.…”