New Perspectives on the Electronic and Geometric Structure of Au70S20(PPh3)12 Cluster: Superatomic-Network Core Protected by Novel Au12(µ3-S)10 Staple Motifs.

Zhimei Tian,Longjiu Cheng,Yangyang Xu

doi:10.3390/nano9081132

Zhimei Tian, Longjiu Cheng + Show 1 more

Open Access

https://doi.org/10.3390/nano9081132

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Abstract

In order to increase the understanding of the recently synthesized Au70S20(PPh3)12 cluster, we used the divide and protect concept and superatom network model (SAN) to study the electronic and geometric of the cluster. According to the experimental coordinates of the cluster, the study of Au70S20(PPh3)12 cluster was carried out using density functional theory calculations. Based on the superatom complex (SAC) model, the number of the valence electrons of the cluster is 30. It is not the number of valence electrons satisfied for a magic cluster. According to the concept of divide and protect, Au70S20(PPh3)12 cluster can be viewed as Au-core protected by various staple motifs. On the basis of SAN model, the Au-core is composed of a union of 2e-superatoms, and 2e-superatoms can be Au3, Au4, Au5, or Au6. Au70S20(PPh3)12 cluster should contain fifteen 2e-superatoms on the basis of SAN model. On analyzing the chemical bonding features of Au70S20(PPh3)12, we showed that the electronic structure of it has a network of fifteen 2e-superatoms, abbreviated as 15 × 2e SAN. On the basis of the divide and protect concept, Au70S20(PPh3)12 cluster can be viewed as Au4616+[Au12(µ3-S)108−]2[PPh3]12. The Au4616+ core is composed of one Au2212+ innermost core and ten surrounding 2e-Au4 superatoms. The Au2212+ innermost core can either be viewed as a network of five 2e-Au6 superatoms, or be considered as a 10e-superatomic molecule. This new segmentation method can properly explain the structure and stability of Au70S20(PPh3)12 cluster. A novel extended staple motif [Au12(µ3-S)10]8− was discovered, which is a half-cage with ten µ3-S units and six teeth. The six teeth staple motif enriches the family of staple motifs in ligand-protected Au clusters. Au70S20(PPh3)12 cluster derives its stability from SAN model and aurophilic interactions. Inspired by the half-cage motif, we design three core-in-cage clusters with cage staple motifs, Cu6@Au12(μ3-S)8, Ag6@Au12(μ3-S)8 and Au6@Au12(μ3-S)8, which exhibit high thermostability and may be synthesized in future.

Highlights

Due to the applications in catalysis, optoelectronics, and photoluminescence, ligand-protected gold (Au-L) nanoclusters have drew much attention in both experiment [1,2,3,4,5,6] and theory [7,8,9,10,11].The synthesis of Au-L clusters contributes much to many areas of science and technology because they have interesting structures [12,13]
According to the segmentation analysis in Supplementary Materials, Au70S20(PCH3)12 cluster is divided into three parts as Figures 2 and 3 show
Worth noting is that [Au12(μ3-S)10]8− motif has six branches, which is obviously different from common staple motif and it is unprecedented in Aum(SR)n clusters

Summary

Introduction

The synthesis of Au-L clusters contributes much to many areas of science and technology because they have interesting structures [12,13]. In the past few years, the metalloid thiolate-protected Au nanoclusters with μ3-S atoms have extended the family and potential applications of Au-L clusters. A large metalloid Au108S24(PPh3) cluster with 24 μ3-S has been revealed, which consists of an octahedral Au44 core, an Au48S24 shell and 16 Au(PPh3) elements [20]. Kenzler et al has synthesized an intermediate size metalloid gold cluster Au70S20(PPh3), revealing an Au22 core surrounded by the Au48S20(PPh3) shell [21]. It is necessary to give a detailed study for the cluster, which may help to deeply understand the stability and structural nature of the cluster

Methods

Results

Conclusion