New insight into the electronic shell of Au-38(SR)(24): a superatomic molecule

National Key Basic Research Program of China [2011CB921404]; National Natural Science Foundation of China [20903001, 21121003, 21273008, 21233007, 91021004]; CAS [XDB01020300]; 211 Project; outstanding youth foundation of Anhui UniversityBased on the recently proposed super valence bond model, in which superatoms can compose superatomic molecules by sharing valence pairs and nuclei for shell closure, the 23c-14e bi-icosahedral Au-23((+9)) core of Au-38(SR)(24) is proved to be a superatomic molecule. Molecular orbital analysis reveals that the Au-23((+9)) core is an exact analogue of the F-2 molecule in electronic configuration. Chemical bonding analysis by the adaptive natural density partitioning method confirms the superatomic molecule bonding framework of Au-38(24)(SR) in a straightforward manner

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

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

Evolution of 4e-Superatom Networks in Au₄(AuL)_1–12 Nanoclusters (L = Cl, SH, PH₂, SCH₃)

Ligand-protected gold (Au–L) nanoclusters have been widely studied due to their interesting optical, electronic, and charging properties. The superatom concept (SAC) and superatom-network (SAN) model are the two known tools, which are used to explain the electronic stability of Au–L nanoclusters. Ever since the crystal determination of the Au₁₀₂(SR)₄₄ cluster, there have been many subsequently crystallized Au–L nanoclusters. However, the size evolution of the superatom network in Au–L nanoclusters is still little known because of a lack of experimental data. To give a direct and overall view of size evolution of the superatom networks in Au–L clusters, the 4e Au₄(AuL)_1–12 (L = Cl, SH, PH₂, SCH₃) system is taken as a test case. The global minimum geometries have been explored using a first principle global minimization technique, namely, genetic algorithm from density functional theory geometry optimization (GA-DFT). The superatom networks in these structures are composed by two of the Au₃, Au₄, Au₅, or Au₆ 2e-superatoms protected by staple motifs. The SAN model is used to explain the chemical bonding patterns, which are verified by chemical bonding analysis based on the adaptive natural density partitioning (AdNDP) method. The clusters which have triangular Au₃ and tetrahedral Au₄ superatoms are also analyzed by the recently proposed grand unified model. The aromatic analysis on the basis of nucleus-independent chemical shifts (NICS) method indicates that the superatoms in SANs of the clusters are highly aromatic. This work gives a clear size-evolution of the 4e-superatom networks for Au–L clusters with 1 to 12 ligands, which discovers the growth mechanism of Au–L clusters with different ligands

Size Evolution of the 2e-Superatom in Ligand-Protected Au Nanoclusters: Au₂‑(AuL)_1–12 (L = Cl, SH, SCH₃, PH₂, and P(CH₃)₂)

Ligand-protected gold (Au-L) nanoclusters have attracted much attention due to their unique properties, and the superatom concept as a significantly well-known concept to explain the electronic stability was suggested. Although there has been a lot of major progress in this field, size evolution of the superatom is still little known because of limited experimental data. To give a direct and overall view of size evolution of the superatom in Au-L clusters, the Au₂-(AuL)_1–12 (L = Cl, SH, SCH₃, PH₂, P­(CH₃)₂) system is taken as a test case. The global minimum geometries are studied by using a method combining the genetic algorithm with density functional theory. The gold cores in these structures consist of Au₃, Au₄, Au₅, and Au₆ 2e-superatoms protected by staple motifs. The 2e-superatoms were confirmed by chemical bonding analysis using the adaptive natural density partitioning method. The aromatic properties of the center of these compounds have been explored by the nucleus-independent chemical shift method, which indicates that the superatoms are highly aromatic. This work gives a clear size evolution of the 2e-superatomic Au-L clusters with 1 to 12 ligands, which discovers the growth mechanism of Au-L clusters with different ligands

Tetrahedral Au₁₇⁺: A Superatomic Molecule with a Au₁₃ FCC Core

A unique tetrahedral structure of Au₁₇⁺ (<i>T</i>_d) is found by using first-principles global optimization, which lies 0.40 eV lower in energy than the previously known structure and has a fairly large HOMO–LUMO gap (1.46 eV) at the TPSS/def2-TZVP level. For neutral Au₁₇, this tetrahedral structure is distorted to <i>D</i>_2d symmetry but is also 0.18 eV lower in energy than the previous flat cage structure. Au₁₇⁺ (<i>T</i>_d) has a FCC Au₁₃ octahedral core, and the other four gold atoms are above its four triangular faces. Magic electronic stability of the cluster is explained by the super valence bond model, of which it can be seen as a superatomic molecule in the electronic structure. Moreover, the cluster can also be viewed as a network of eight 2e-superatoms. This Au₁₇⁺ cluster mimics the behavior of the Au₂₀ pyramid, known as a unique one among the family of gold clusters since its discovery in 2003, in electronic structures

New insight into the electronic shell of Au38(SR)24: A superatomic molecule

Based on the recently proposed super valence bond model, in which superatoms can compose superatomic molecules by sharing valence pairs and nuclei for shell closure, the 23c-14e bi-icosahedral Au23(+9) core of Au38(SR)24 is proved to be a superatomic molecule. Molecular orbital analysis reveals that the Au23(+9) core is an exact analogue of the F2 molecule in electronic configuration. Chemical bonding analysis by the adaptive natural density partitioning method confirms the superatomic molecule bonding framework of Au38(SR) 24 in a straightforward manner. ? 2013 The Royal Society of Chemistry

Electronic Stability of Phosphine-Protected Au₂₀ Nanocluster: Superatomic Bonding

A recent experiment reported that a newly crystallized phosphine-protected Au₂₀ nanocluster [Au₂₀(PPhy₂)₁₀Cl₄]­Cl₂ [PPhpy₂ = bis­(2-pyridyl)­phenylphosphine] owns a very stable Au₂₀ core, but the number of valence electrons of the Au₂₀ core is 14e, which is not predicted by the superatom model. So we apply the density functional theory to further study this cluster from its molecular orbital and chemical bonding. The results suggest that the Au₂₀⁽⁺⁶⁾ core is an analogue of the F₂ molecule based on the super valence bond model, and the 20-center–14-electron Au₂₀⁽⁺⁶⁾ core can be taken as a superatomic molecule bonded by two 11-center–7-electron superatoms, where the two 11c superatoms share two Au atoms and two electrons to meet an 8-electron closed shell for each. The electronic shell closure enhances the stability of the Au₂₀ core, besides the PN bridges. Exceptionally, the theoretical HOMO–LUMO gap (1.03 eV) disagrees with the experimental value (2.24 eV), and some possible reasons for this big difference are analyzed in this paper