Search results for "superatom"
showing 9 items of 39 documents
Silver Sulfide Nanoclusters and the Superatom Model
2015
The superatom model of electron-shell closings has been widely used to explain the stability of noble-metal nanoclusters of few nanometers, including thiolate-protected Au and Ag nanoclusters. The presence of core sulfur atoms in silver sulfide (Ag–S) nanoclusters renders them a class of clusters with distinctive properties as compared to typical noble-metal clusters. Here, it is natural to ask whether the superatom model is still applicable for the Ag–S nanoclusters with mixed metal and nonmetal core atoms. To address this question, we applied density functional simulations to analyze a series of Ag–S nanoclusters: Ag14S(SPh)12(PPh3)8, Ag14(SC6H3F2)12(PPh3)8, Ag70S16(SPh)34(PhCO2)4(triphos…
Copper-hydride nanoclusters with enhanced stability by N-heterocyclic carbenes
2021
AbstractCopper-hydrides have been intensively studied for a long time due to their utilization in a variety of technologically important chemical transformations. Nevertheless, poor stability of the species severely hinders its isolation, storage and operation, which is worse for nano-sized ones. We report here an unprecedented strategy to access to ultrastable copper-hydride nanoclusters (NCs), namely, using bidentate N-heterocyclic carbenes as stabilizing ligands in addition to thiolates. In this work, a simple synthetic protocol was developed to synthesize the first large copper-hydride nanoclusters (NCs) stabilized by N-heterocyclic carbenes (NHCs). The NC, with the formula of Cu31(RS)2…
Thiol-Stabilized Atomically Precise, Superatomic Silver Nanoparticles for Catalyzing Cycloisomerization of Alkynyl Amines
2018
Abstract Both the electronic and surface structures of metal nanomaterials play critical roles in determining their chemical properties. However, the non-molecular nature of conventional nanoparticles makes it extremely challenging to understand the molecular mechanism behind many of their unique electronic and surface properties. In this work, we report the synthesis, molecular and electronic structures of an atomically precise nanoparticle, [Ag206L72]q (L = thiolate, halide; q = charge). With a four-shell Ag7@Ag32@Ag77@Ag90 Ino-decahedral structure having a nearly perfect D5h symmetry, the metal core of the nanoparticle is co-stabilized by 68 thiolate and 4 halide ligands. Both electroche…
Ag44(EBT)26(TPP)4 Nanoclusters with Tailored Molecular and Electronic Structure
2021
Although atomically precise metalloid nanoclusters (NCs) of identical size with distinctly different molecular structures are highly desirable to understand the structural effects on the intriguing optical and photophysical properties, their synthesis remains highly challenging. Herein, we employed phosphine and thiol capping ligands featuring appropriate steric effects and synthesized a charge‐neutral Ag NC with the formula, Ag 44 (EBT) 26 (TPP) 4 (EBT: 2‐ethylbenzenethiolate; TPP: triphenylphosphine). The single‐crystal X‐ray structure reveals that this NC has a hollow metal core of Ag 12 @Ag 20 and a metal‐ligand shell of Ag 12 (EBT) 26 (TPP) 4 . The presence of mixed ligands and long V‐…
Electronic shell structures in bare and protected metal nanoclusters
2016
This short review discusses the concept of the electronic shell structure in the context of metal nanoclusters. Electronic shell structure is a natural consequence of quantization of fermionic states in a quantum confinement, where the symmetry of the confining potential creates energetically close-lying sets of states that reflect the symmetry of the potential. It was introduced in cluster physics in early 1980s and initially influenced greatly by the related model of nuclear shell structure from 1950’s. Three application areas are discussed consisting of free gas phase clusters, clusters supported by insulating oxides or oxide thin films, and clusters that are synthesized by wet chemistry…
Structural Evolution of Atomically Precise Thiolated Bimetallic [Au12+nCu32(SR)30+n]4– (n = 0, 2, 4, 6) Nanoclusters
2014
A series of all-thiol stabilized bimetallic Au-Cu nanoclusters, [Au(12+n)Cu32(SR)(30+n)](4-) (n = 0, 2, 4, 6 and SR = SPhCF3), are successfully synthesized and characterized by X-ray single-crystal analysis and density functional theory (DFT) calculations. Each cluster consists of a Keplerate two-shell Au12@Cu20 core protected by (6 - n) units of Cu2(SR)5 and n units of Cu2Au(SR)6 (n = 0, 2, 4, 6) motifs on its surface. The size and structural evolution of the clusters is atomically controlled by the Au precursors and countercations used in the syntheses. The clusters exhibit similar optical absorption properties that are not dependent on the number of surface Cu2Au(SR)6 units. Although DFT…
Electronic Structure and Optical Properties of the Intrinsically Chiral 16-Electron Superatom Complex [Au20(PP3)4]4+
2014
The recently solved crystal structure of the [Au20(PP3)4]Cl4 cluster (PP3: tris(2-(diphenylphophino)ethyl)phosphine) is examined using density functional theory (DFT). The Au20 core of the cluster is intrinsically chiral by the arrangement of the Au atoms. This is in contrast to the chirality of thiolate-protected gold clusters, in which the protecting Au-thiolate units are arranged in chiral patterns on achiral cores. We interpret the electronic structure of the [Au20(PP3)4]Cl4 cluster in terms of the superatom complex model. The 16-electron cluster cannot be interpreted as a dimer of 8-electron clusters (which are magic). Instead, a superatomic electron configuration of 1S(2) 1P(6) 1D(6) …
A DFT Study of Linear Gold–Thiolate Superclusters Absorbing in the Therapeutic NIR Window
2015
A series of linear clusters up to an aspect ratio of 1:6, formed as multimers of smaller clusters with an icosahedral Au13(5+) core having an eight-electron superatom configuration, are computationally predicted to have a greatly enhanced size-dependent absorption in the near-infrared (NIR) region extending to the biologically important NIR window. A novel structural model is presented for the previously isolated thiol-stabilized Au54(SR)30 cluster, where the metal core is formed as a heterodimer of the cores of the known Au25(SR)18(-/0) and Au38(SR)24 clusters.
The electronic structure of Ge9[Si(SiMe3)3]3-: a superantiatom complex.
2012
We report on the electronic structure of Ge(9)[Si(SiMe(3))(3)](3)(-). Systematic density functional theory analysis of the electronic shell structure of the cluster and its derivatives reveals that the Ge(9)[Si(SiMe(3))(3)](3)(-) and its neutral counterpart have electronic shells that can be explained using the superatom model. The ligand-core interaction of these complexes is distinctly different from previously identified gold, gallium, and aluminium superatom complexes, indicating an electron-donating rather than electron-withdrawing ligand. We modify the electron-counting rule for this case and introduce a simple picture for superatom and superantiatom complexes. Discussions comparing s…