Browse
Submit Data
Databases
API
Help

Dataset Information

21 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Absolute configuration retention of a configurationally labile ligand during dynamic processes of thiolate protected gold clusters.

ABSTRACT: Monolayer protected metal clusters are dynamic nanoscale objects. For example, the chiral Au₃₈(2-PET)₂₄ cluster (2-PET: 2-phenylethylthiolate) racemizes at moderate temperature. In addition, ligands and metal atoms can easily exchange between clusters. Such processes are important for applications of monolayer protected metal clusters; however, the mechanistic study of such processes turns out to be challenging. Here we use a configurationally labile, axially chiral ligand, biphenyl-2,2'-dithiol (R/S-BiDi), as a probe to study dynamic cluster processes. It is shown that the ligand exchange of free R/S-BiDi on a chiral Au₃₈(2-PET)₂₄ cluster is diastereospecific. Using chiral chromatography, isolated single diastereomers of the type anticlockwise/clockwise-Au₃₈(2-PET)₂₂(R/S-BiDi)₁ could be isolated. Upon heating, the cluster framework racemizes, while the R/S-BiDi ligand does not. These findings demonstrate that during cluster racemization and/or ligand exchange between clusters, the R/S-BiDi ligand is sufficiently confined, thus preventing its racemization, and exclude the possibility that the ligand desorbs from the cluster surface.

SUBMITTER: Wang Y

PROVIDER: S-EPMC8278927 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Ligand Migration from Cluster to Support: A Crucial Factor for Catalysis by Thiolate-protected Gold Clusters.

Project description:Thiolate protected metal clusters are valuable precursors for the design of tailored nanosized catalysts. Their performance can be tuned precisely at atomic level, e.?g. by the configuration/type of ligands or by partial/complete removal of the ligand shell through controlled pre-treatment steps. However, the interaction between the ligand shell and the oxide support, as well as ligand removal by oxidative pre-treatment, are still poorly understood. Typically, it was assumed that the thiolate ligands are simply converted into SO2, CO2 and H2O. Herein, we report the first detailed observation of sulfur ligand migration from Au to the oxide support upon deposition and oxidative pre-treatment, employing mainly S K-edge XANES. Consequently, thiolate ligand migration not only produces clean Au cluster surfaces but also the surrounding oxide support is modified by sulfur-containing species, with pronounced effects on catalytic properties.

| S-EPMC6348379 | biostudies-other

A Novel Physical Approach for Cationic-Thiolate Protected Fluorescent Gold Nanoparticles.

Project description:Knowledge on the synthesis of cationically charged fluorescent gold nanoparticles (Au NPs) is limited because the electrostatic repulsion between cationic ligands on the surface of NP hinders the formation of small Au NPs (usually less than ca. 2?nm) during nucleation in solvents. We herein propose a novel methodology for a synthesis of water-dispersible, cationic-thiolate protected fluorescent Au NPs by the sputtering of Au into liquid matrix containing thiolate ligands. By controlling mercaptan concentration the size and photophysical characteristics of Au NPs were directly controlled, resulting in near IR fluorescence with a 0.9% of absolute quantum yield. Cationically charged fluorescent metal NPs are promising, especially in biological fields, and this work provides a novel methodology towards the synthesis of a new series of functional metal NPs.

| S-EPMC4612736 | biostudies-literature

Thiolate-Protected Gold Nanoparticles Via Physical Approach: Unusual Structural and Photophysical Characteristics.

Project description:Here we report a novel physical approach for thiolate-protected fluorescent gold nanoparticles with a controlled size of the order of a few nanometers. This approach is based on a sputtering of gold into a liquid matrix containing thiolate ligand as a stabilizer at various concentrations, thus no reductant was used. The size of the gold nanoparticles was successfully controlled to range from 1.6 to 7.4 nm by adjusting the thiol concentrations. Surface plasmon absorption was observed in larger nanoparticles, but it was not observed in smaller ones. Such smaller nanoparticles fluoresced at around 670 nm with a small spectral shift according to their size, however, the diameter (1.6-2.7 nm) was very strange to show such red emission compared with photophysical characteristics of reported gold cluster or nanoparticles synthesized by chemical method. By detailed investigations using TEM, HAADF-STEM, XPS, and TGA, and size fractionation by size exclusion chromatography, we finally arrived at the plausible mechanism for the origin of unusual fluorescence property; the obtained gold nanoparticles are not single-crystal and are composed of aggregates of very small components such as multinuclear gold clusters or complexes.

| S-EPMC4947912 | biostudies-literature

Structural and theoretical basis for ligand exchange on thiolate monolayer protected gold nanoclusters.

Project description:Ligand exchange reactions are widely used for imparting new functionality on or integrating nanoparticles into devices. Thiolate-for-thiolate ligand exchange in monolayer protected gold nanoclusters has been used for over a decade; however, a firm structural basis of this reaction has been lacking. Herein, we present the first single-crystal X-ray structure of a partially exchanged Au(102)(p-MBA)(40)(p-BBT)(4) (p-MBA = para-mercaptobenzoic acid, p-BBT = para-bromobenzene thiol) with p-BBT as the incoming ligand. The crystal structure shows that 2 of the 22 symmetry-unique p-MBA ligand sites are partially exchanged to p-BBT under the initial fast kinetics in a 5 min timescale exchange reaction. Each of these ligand-binding sites is bonded to a different solvent-exposed Au atom, suggesting an associative mechanism for the initial ligand exchange. Density functional theory calculations modeling both thiol and thiolate incoming ligands postulate a mechanistic pathway for thiol-based ligand exchange. The discrete modification of a small set of ligand binding sites suggests Au(102)(p-MBA)(44) as a powerful platform for surface chemical engineering.

| S-EPMC4624284 | biostudies-literature

Iodine activation: a general method for catalytic enhancement of thiolate monolayer-protected metal clusters.

Project description:To enhance catalytic activity, the present study details a general approach for partial thiolate ligand removal from monolayer-protected clusters (MPCs) by straightforward in situ addition of iodine. Two model reactions are examined to illustrate the effects on the catalytic activity of glutathione (SG)-capped Au MPCs serving as a catalyst for the NaBH4 reduction of 4-nitrophenol to 4-aminophenol and SG-capped Pd MPCs serving as a catalyst for the hydrogenation/isomerization of allyl alcohol. Iodine addition promoted partial thiolate ligand removal from both MPCs and improved the catalytic properties, presumably due to greater surface exposure of the metal cores as a result of ligand dissociation. The rate of 4-nitrophenol reduction increased from 0.066 min-1 in the absence of I2 to 0.505 min-1 in the presence of 2.0 equivalents I2 (equivalents based on total ligated glutathione). The reaction of allyl alcohol to produce 1-propanol and propanal was similarly accelerated as indicated by the increase in turnover frequency from 131 to 230 moles products per moles catalyst per h by addition of 0.2 equivalents I2. In both reactions, as the amount of I2 added increases the catalyst recyclability decreases due to catalyst instability. Low equivalents of I2 are optimal when considering both reaction rate and catalyst recyclability.

| S-EPMC7350617 | biostudies-literature

Combinatorial discovery of cosolvent systems for production of narrow dispersion thiolate-protected gold nanoparticles.

Project description:The effect of aqueous solvent concentration in the synthesis of water-soluble thiolate-protected gold nanoparticles (AuNPs) was investigated for 13 water-miscible solvents and three thiolate ligands (p-mercaptobenzoic acid, thiomalic acid, and glutathione). The results were analyzed by construction of heat maps that rank each reaction result for polydispersity. When solvents were organized in the heat map according to their Dimroth-Reichardt ET parameter (an approximate measure of polarity), two "hot spots" become apparent that are independent of the ligand used. We speculate that one hot spot may arise in part from the metal chelation or coordination ability of solvents that include diglyme, 1,2-dimethoxyethane, 1,4-dioxane, and tetrahydrofuran. The second hot spot arises at concentrations of alcohols including 2-propanol and 1-butanol that appear to selectively precipitate a growing product, presumably stopping its growth at a certain size. We observe some tightly dispersed products that appear novel. Overall, this study expands the number of tightly dispersed water-soluble AuNPs that can be directly synthesized.

| S-EPMC4294592 | biostudies-literature

Chiral Inversion of Thiolate-Protected Gold Nanoclusters via Core Reconstruction without Breaking a Au-S Bond.

Project description:On the basis of density functional theory computations of the well-known chiral Au38(SR)24 nanocluster and its Pd- and Ag-doped derivatives, we propose here a mechanism for chiral inversion that does not require the breaking of a metal-sulfur bond at the metal-ligand interface but features a collective rotation of the gold core. The calculated energy barriers for this mechanism for Au38 and Pd-doped Au38 are in the range of 1-1.5 eV, significantly lower than barriers involving the breakage of Au-S bonds (2.5 eV). For Ag-doped Au38, barriers for both mechanisms are similar (1.3-1.5 eV). Inversion barriers for a larger chiral Au144(SR)60 are much higher (2.5-2.8 eV). Our computed barriers are in good agreement with racemization barriers estimated from existing experiments for bare and doped Au38. These results highlight the sensitivity of chiral inversion to the size, structure, and metal composition of the metal core and sensitivity to the detailed structure of the metal-thiolate interface. Our work also predicts that enantiopure Au144(SR)60 clusters would be promising materials for applications requiring high resistance to chiral inversion.

| S-EPMC6727375 | biostudies-literature

A unified view of ligand-protected gold clusters as superatom complexes.

Project description:Synthesis, characterization, and functionalization of self-assembled, ligand-stabilized gold nanoparticles are long-standing issues in the chemistry of nanomaterials. Factors driving the thermodynamic stability of well documented discrete sizes are largely unknown. Herein, we provide a unified view of principles that underlie the stability of particles protected by thiolate (SR) or phosphine and halide (PR(3), X) ligands. The picture has emerged from analysis of large-scale density functional theory calculations of structurally characterized compounds, namely Au(102)(SR)(44), Au(39)(PR(3))(14)X(6)(-), Au(11)(PR(3))(7)X(3), and Au(13)(PR(3))(10)X(2)(3+), where X is either a halogen or a thiolate. Attributable to a compact, symmetric core and complete steric protection, each compound has a filled spherical electronic shell and a major energy gap to unoccupied states. Consequently, the exceptional stability is best described by a "noble-gas superatom" analogy. The explanatory power of this concept is shown by its application to many monomeric and oligomeric compounds of precisely known composition and structure, and its predictive power is indicated through suggestions offered for a series of anomalously stable cluster compositions which are still awaiting a precise structure determination.

| S-EPMC2442568 | biostudies-literature

Controlled reduction for size selective synthesis of thiolate-protected gold nanoclusters Aun(n?=?20, 24, 39, 40).

Project description:This work presents a controlled reduction method for the selective synthesis of different sized gold nanoclusters protected by thiolate (SR?=?SC2H4Ph). Starting with Au(III) salt, all the syntheses of Aun(SR)m nanoclusters with (n, m)?=?(20, 16), (24, 20), (39, 29), and (40, 30) necessitate experimental conditions of slow stirring and slow reduction of Au(I) intermediate species. By controlling the reaction kinetics for the reduction of Au(I) into clusters by NaBH4, different sized gold nanoclusters are selectively obtained. Two factors are identified to be important for the selective growth of Au20, Au24, and Au39/40 nanoclusters, including the stirring speed of the Au(I) solution and the NaBH4 addition speed during the step of Au(I) reduction to clusters. When comparing with the synthesis of Au25(SC2H4Ph)18 nanoclusters, we further identified that the reduction degree of Au(I) by NaBH4 also plays an important role in controlling cluster size. Overall, our results demonstrate the feasibility of attaining new sizes of gold nanoclusters via a controlled reduction route.

| S-EPMC3503687 | biostudies-literature

Absolute configuration of odorine.

Project description:The title compound, known as odorine or roxburghiline {systematic name: (S)-N-[(R)-1-cinnamoylpyrrolidin-2-yl]-2-methyl-butanamide}, C(18)H(24)N(2)O(2), is a nitro-genous compound isolated from the leaves of Aglaia odorata. The absolute configuration was determined by refinement of the Flack parameter with data collected using Cu Kα radiation showing positions 2 and 2' to be S and R, respectively. The pyrrolidine ring adopts an envelope conformation. In the crystal, mol-ecules are linked into chains along [010] by inter-molecular N-H⋯O hydrogen bonds.

| S-EPMC3007931 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data