Revealing structural isomerism in a nanocluster remains significant but challenging. Herein, we have obtained a pair of structural isomers, [AuAg(SR)(dppm)X]-C and [AuAg(SR)(dppm)X]-Ac [dppm = bis(diphenyphosphino)methane; HSR = 1-adamantanethiol/ tert-butylmercaptan; X = Br/Cl; C stands for one of the structural isomers being chiral; Ac stands for another being achiral], that show different structures as well as different chiralities. These structures are determined by single-crystal X-ray diffraction and further confirmed by high-resolution electrospray ionization mass spectrometry. On the basis of the isomeric structures, the most important finding is the different arrangements of the AuAg@Au metal core, leading to changes in the overall shape of the cluster, which is responsible for structural isomerism. Meanwhile, the two enantiomers of [AuAg(SR)(dppm)X]-C are separated by high-performance liquid chromatography. Our work will contribute to a deeper understanding of the structural isomerism in noble-metal nanoclusters and enrich the chiral nanocluster.
Atomically precise nanoclusters (APNCs), as ideal model catalysts, revealed great advantages to deep-understand of reaction mechanisms in heterogeneous catalysis. Boosting the activity of APNCs is the most critical issue under the premise of maintaining structure invariance. Herein, utilizing Metal-Support Interaction (MSI) strategy, we prepared an excellent and recyclable catalyst for aerobic oxidation by combination of an otherwise inert nanocluster [Pd 3 Cl(PPh 2 ) 2 (PPh 3 ) 3 ] + [SbF 6 ] À (denoted as Pd 3 Cl) with functional titanate nanotubes (TNT). The promising Pd 3 Cl/TNT composite gives rise to excellent conversion with 100% selectivity without any additives at 30 8C under an oxygen pressure. This result is unprecedented in ligand-on nanocluster catalysts without high temperature calcination. The distinct difference between their activities of Pd 3 Cl/TNT composite and fresh Pd 3 Cl nanocluster is explained by the presence of the MSI effect, as confirmed using X-ray photoelectron spectroscopy (XPS) analysis. Theoretical simulations are further carried out to elucidate the catalytic mechanism, indicating the MSI effect promotes the crucial b-H elimination step in both kinetic and thermodynamic aspects. This work presents the example of atomic-level understanding of the effect of MSI on facilitating the APNCs catalytic properties.
The valence self-regulation of sulfur from the “−2” valence state in thiols to the “−1” valence state in hydroxylated thiolates has been accomplished using the Pt1Ag28 nanocluster as a platform—the first time that the “−1” valent sulfur has been detected as S−1. Two previously unknown nanoclusters, Pt1Ag28(SR)20 and Pt1Ag28(SR)18(HO-SR)2 (where SR represents 2-adamantanethiol), have been synthesized and characterized—in the latter nanocluster, the presence of hydroxyl induces the valence regulation of two special S atoms from “−2” (in SR) to “−1” valence state in the HO-S(Ag)R. Because of the contrasting nature of the capping ligands in these two nanoclusters [i.e., only SR in Pt1Ag28(SR)20 or both SR- and HO-SR- in Pt1Ag28(SR)18(HO-SR)2], they exhibit differing shell architectures, even though their cores (Pt1Ag12) are in the same icosahedral configuration. Single-crystal x-ray diffraction analysis revealed their 1:1 cocrystallization, and mass spectrometry verified the presence of hydroxyls on Pt1Ag28(SR)18(HO-SR)2.
Understanding the microbial and chemical
diversities, as well as
what affects these diversities, is important for modern manufacturing
of traditional fermented foods. In this work, Chinese dark teas (CDTs)
that are traditional microbial fermented beverages with relatively
high sample diversity were collected. Microbial DNA amplicon sequencing
and mass spectrometry-based untargeted metabolomics show that the
CDT microbial β diversity, as well as the nonvolatile chemical
α and β diversities, is determined by the primary impact
factors of geography and manufacturing procedures, in particular,
latitude and pile fermentation after blending. A large number of metabolites
sharing between CDTs and fungi were discovered by Feature-based Molecular
Networking (FBMN) on the Global Natural Products Social Molecular
Networking (GNPS) web platform. These molecules, such as prenylated
cyclic dipeptides and B-vitamins, are functionally important for nutrition,
biofunctions, and flavor. Molecular networking has revealed patterns
in metabolite profiles on a chemical family level in addition to individual
structures.
Understanding the ligand effects in the nanocluster (NC) range is crucial for tailoring the properties. We herein report on the crystal structure of the Au 15 Ag 3 (SPhMe 2 ) 14 nanocluster. Compared with the previously reported Au 15 Au 3 -(SC 6 H 11 ) 14 nanocluster, Au 15 Ag 3 (SPhMe 2 ) 14 exhibits a different crystal and electronic structure, which further affects the optical spectra because of the ligand effect. In combination with density functional theory (DFT) calculations, the differences in the [a]
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