Dynamics of weak interactions in the ligand layer of meta-mercaptobenzoic acid protected gold nanoclusters Au68(m-MBA)32 and Au144(m-MBA)40

Atomically precise metal nanoclusters, stabilized and functionalized by organic ligands, are emerging nanomaterials with potential applications in plasmonics, nano-electronics, bio-imaging, nanocatalysis, and as therapeutic agents or drug carriers in nanomedicine. The ligand layer has an important role in modifying the physico-chemical properties of the clusters and in defining the interactions between the clusters and the environment. While this role is well recognized from a great deal of experimental studies, there is very little theoretical information on dynamical processes within the layer itself. Here, we have performed extensive molecular dynamics simulations, with forces calculated…

Towards Atomically Precise Supported Catalysts from Monolayer‐Protected Clusters: The Critical Role of the Support

Abstract Controlling the size and uniformity of metal clusters with atomic precision is essential for fine‐tuning their catalytic properties, however for clusters deposited on supports, such control is challenging. Here, by combining X‐ray absorption spectroscopy and density functional theory calculations, it is shown that supports play a crucial role in the evolution of monolayer‐protected clusters into catalysts. Based on the acidic nature of the support, cluster‐support interactions lead either to fragmentation of the cluster into isolated Au–ligand species or ligand‐free metallic Au0 clusters. On Lewis acidic supports that bind metals strongly, the latter transformation occurs while pre…

Selective Acrolein Hydrogenation over Ligand-Protected Gold Clusters : A Venus Flytrap Mechanism

The catalytic partial hydrogenation of α,β-unsaturated aldehydes is an ideal reaction to understand the selectivity between two different functional groups Here the two functional groups are C═C and C═O, and the hydrogenation of C═O is preferentially desired due to the importance of the issuing products, unsaturated alcohols, in fine-chemical industries. Using density functional theory calculations, we investigate the catalytic competency toward this reaction of a Au nanocluster in the presence of protecting ligands that offer higher stability and the possibility for the uniform distribution of size-selected clusters in the catalytic system. meta-Mercaptobenzoic-acid-protected-protected Au …

Cover Feature: Towards Atomically Precise Supported Catalysts from Monolayer‐Protected Clusters: The Critical Role of the Support (Chem. Eur. J. 31/2020)

Support work function as a descriptor and predictor for the charge and morphology of deposited Au nanoparticles

We show, using density functional theory calculations, that the charge, magnetic moment, and morphology of deposited Au nanoclusters can be tuned widely by doping the oxide support with aliovalent cations and anions. As model systems, we have considered Aun (n = 1, 2, or 20) deposited on doped MgO and MgO/Mo supports. The supports have been substitutionally doped with varying concentrations θ of F, Al, N, Na, or Li. At θ = 2.78%, by varying the dopant species, we are able to tune the charge of the Au monomer between −0.84e and +0.21e, the Au dimer between −0.87e and −0.16e, and, most interestingly, Au20 between −3.97e and +0.49e. These ranges can be further extended by varying θ. These chan…

Support work function as a descriptor and predictor for the charge and morphology of deposited Au nanoparticles.

We show, using density functional theory calculations, that the charge, magnetic moment, and morphology of deposited Au nanoclusters can be tuned widely by doping the oxide support with aliovalent cations and anions. As model systems, we have considered Aun (n = 1, 2, or 20) deposited on doped MgO and MgO/Mo supports. The supports have been substitutionally doped with varying concentrations θ of F, Al, N, Na, or Li. At θ = 2.78%, by varying the dopant species, we are able to tune the charge of the Au monomer between −0.84e and +0.21e, the Au dimer between −0.87e and −0.16e, and, most interestingly, Au20 between −3.97e and +0.49e. These ranges can be further extended by varying θ. These chan…

Computational Criteria for Hydrogen Evolution Activity on Ligand-Protected Au25-Based Nanoclusters

The hydrogen evolution reaction (HER) is a critical reaction in addressing climate change; however, it requires catalysts to be generated on an industrial scale. Nanomaterials offer several advantages over conventional HER catalysts, including the possibility of atomic precision in tailoring the intrinsic activity. Ligand-protected metal clusters, such as the thiolate-protected MAu24(SR)18 (where M is Au, Cu, Pd), are of particular interest as not only are they electrocatalytically active toward HER, but the charge state and composition can be precisely tuned. Here, we present a comprehensive computational study examining how the charge state and dopants affect the catalytic activity of [MA…

Atomically Precise, Thiolated Copper–Hydride Nanoclusters as Single-Site Hydrogenation Catalysts for Ketones in Mild Conditions

Copper-hydrides are known catalysts for several technologically important reactions such as hydrogenation of CO, hydroamination of alkenes and alkynes, and chemoselective hydrogenation of unsaturated ketones to unsaturated alcohols. Stabilizing copper-based particles by ligand chemistry to nanometer scale is an appealing route to make active catalysts with optimized material economy; however, it has been long believed that the ligand-metal interface, particularly if sulfur-containing thiols are used as stabilizing agent, may poison the catalyst. We report here a discovery of an ambient-stable thiolate-protected copper-hydride nanocluster [Cu25H10(SPhCl2)18]3- that readily catalyzes hydrogen…

Addressing Dynamics at Catalytic Heterogeneous Interfaces with DFT-MD: Anomalous Temperature Distributions from Commonly Used Thermostats.

Density functional theory-based molecular dynamics (DFT-MD) has been widely used for studying the chemistry of heterogeneous interfacial systems under operational conditions. We report frequently overlooked errors in thermostated or constant-temperature DFT-MD simulations applied to study (electro)catalytic chemistry. Our results demonstrate that commonly used thermostats such as Nose−Hoover, Berendsen, and simple velocity rescaling methods fail to provide are liable temperature description for systems considered. Instead, nonconstant temperatures and large temperature gradients within the different parts of the system are observed. The errors are not a “feature” of any particular code but …

Binding Behavior of Carbonmonoxide to Gold Atoms on Ag(001)

AbstractThe adsorption behavior of single CO molecules at 4 K bound to Au adatoms on a Ag(001) metal surface is studied with scanning tunneling microscopy (STM) and inelastic electron tunneling spectroscopy (IETS). In contrast to earlier observations two different binding configurations are observed—one on top of a Au adatom and the other one adsorbed laterally to Au on Ag(001). Moreover, IETS reveals different low-energy vibrational energies for the two binding sites as compared to the one for a single CO molecule bound to Ag(001). Density functional theory (DFT) calculations of the adsorption energies, the diffusion barriers, and the vibrational frequencies of the CO molecule on the diffe…

Dynamics of weak interactions in the ligand layer of meta-mercaptobenzoic acid protected gold nanoclusters Au68(m-MBA)32 and Au144(m-MBA)40

Atomically precise metal nanoclusters, stabilized and functionalized by organic ligands, are emerging nanomaterials with potential applications in plasmonics, nano-electronics, bio-imaging, nanocatalysis, and as therapeutic agents or drug carriers in nanomedicine. The ligand layer has an important role in modifying the physico-chemical properties of the clusters and in defining the interactions between the clusters and the environment. While this role is well recognized from a great deal of experimental studies, there is very little theoretical information on dynamical processes within the layer itself. Here, we have performed extensive molecular dynamics simulations, with forces calculated…

CCDC 1851619: Experimental Crystal Structure Determination

Related Article: Cunfa Sun, Nisha Mammen, Sami Kaappa, Peng Yuan, Guocheng Deng, Chaowei Zhao, Juanzhu Yan, Sami Malola, Karoliina Honkala, Hannu Häkkinen, Boon K. Teo, Nanfeng Zheng|2019|ACS Nano|13|5975|doi:10.1021/acsnano.9b02052