Polyhedral metallocalixarene nanocage clusters based on pure Ti(
iv
) ions are to our knowledge unknown hitherto. Herein we report the first Ti(
iv
)-based metallocalixarene nanocage cluster by ...assembling a Ti
13
O
14
cage with six
t
-butylcalix4arene molecules. Notably, the cluster exhibits extraordinary stability in high-concentration acid/alkali solutions and can act as a stable photocatalyst to catalyze the oxidation of ammonia to imines.
The first Ti(
iv
)-based metallocalixarene nanocage cluster was obtained using
t
-butylcalix4arene as the ligand, which has extraordinary chemical stability and can act as a stable photocatalyst to catalyze the oxidation of ammonia to imine.
Developing catalysts with both useful enantioselectivities and million turnover numbers (TONs) for asymmetric hydrogenation of ketones is attractive for industrial production of high-value bioactive ...chiral entities but remains a challenging. Herein, we report an ultra-efficient anionic Ir-catalyst integrated with the concept of multidentate ligation for asymmetric hydrogenation of ketones. Biocatalysis-like efficacy of up to 99% ee (enantiomeric excess), 13,425,000 TON (turnover number) and 224 s
TOF (turnover frequency) were documented for benchmark acetophenone. Up to 1,000,000 TON and 99% ee were achieved for challenging pyridyl alkyl ketone where at most 10,000 TONs are previously reported. The anionic Ir-catalyst showed a novel preferred ONa/MH instead of NNa/MH bifunctional mechanism. A selective industrial route to enantiopure nicotine has been established using this anionic Ir-catalyst for the key asymmetric hydrogenation step at 500 kg batch scale, providing 40 tons scale of product.
Furanodiene is a natural terpenoid isolated from Rhizoma Curcumae, a well-known Chinese medicinal herb that presents anticancer effects in various types of cancer cell lines. In this study, we have ...successfully established zebrafish xenografts with 5 various human cancer cell lines; and validated these models with anti-cancer drugs used clinically for treating human cancer patients. We found that Furanodiene was therapeutically effective for human JF 305 pancreatic cancer cells and MCF-7 breast cancer cells xenotranplanted into zebrafish. Furanodiene showed a markedly synergistic anti-cancer effect when used in combination with 5-FU (5-Fluorouracil) for both human breast cancer MDA-MB-231 cells and human liver cancer BEL-7402 cells xenotransplanted into zebrafish. Unexpectedly, Furanodiene reversed multiple drug resistance in the zebrafish xenotransplanted with cis-Platinum-resistant human non-small cell lung cancer cells and Adriamycin-resistant human breast cancer cells. Furanodiene played its anti-cancer effects through anti-angiogenesis and inducing ROS production, DNA strand breaks and apoptosis. Furanodiene suppresseed efflux transporter Pgp (P-glycoprotein) function and reduced Pgp protein level, but no effect on Pgp related gene (MDR1) expression. These results suggest sensitizition and synergistic anti-cancer effects of Furanodiene that is worthy of a further investigation.
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Doping Cd atom(s) into gold clusters is very promising in both theoretical study and practical applications. However, it has long been a challenge to synthesize heavily Cd-doped AuCd bimetallic ...clusters and thereby reveal their structure-property correlations. Herein a novel AuCd bimetallic cluster: Au
Cd
(SC
H
)
(SC
H
denotes deprotonated cyclohexanethiol) with a Cd to Au atomic ratio of 1:1 is reported. The precise structure of the cluster determined by single crystal X-ray diffraction demonstrates that it has a unique hexatetrahedron Au
core and a distinctive shell. Intriguingly, due to the special protecting motifs, the cluster exhibits high stability in various conditions studied, indicating that the geometric structure is crucial in determining the stability of the cluster. Most importantly, the photothermal property of the cluster has been investigated in comparison with those of M
-kernel (M denotes metal atoms) clusters, and the results imply that the compactness and the Cd atom doping of the core play important roles in dictating the photothermal effect of the cluster. The authors believe that this work will provide some ideas for the rational design of clusters with high stability and excellent photothermal property.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Dinitrogen activation in ammonia (NH3) synthesis usually obeys either the dissociative or associative route. We report here a combination of dissociative and associative routes over a titanium ...carbonitride (TiCN)-promoted Ru-based catalyst to achieve an outstanding NH3 synthesis rate. The developed Ru/3TiCN/ZrH2 catalyst shows a superior NH3 synthesis rate of 25.6 mmol gcat –1 h–1 at 400 °C and 1 MPa. Our studies reveal that TiCN transfers electrons to the Ru centers and reduces the aggregation of Ru metal particles to generate more B5 sites, thus accelerating the dissociation of N2 to form NH3 via a dissociative route. Meanwhile, the facile formation of nitrogen vacancies on TiCN assisted by Ru enables the associative mechanism initiated with N2 hydrogenation to form *NNH. The synergistic effect of Ru and TiCN on N2 activation via integrating the dissociative and associative mechanisms accounts for the superior NH3 synthesis rate of our catalyst under mild conditions.
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Ammonia synthesis is structure sensitive, and a minute change in the catalyst structure would cause a dramatic change in activity. To date, none of the studies reveal the metal size effect at a ...subnanometer scale on NH3 synthesis, and such investigation remains a challenge. Here, we report the synthesis of Ru catalysts with sizes ranging from single atoms, atomic clusters (ACCs), sub-nanometric clusters, to nanoparticles (NPs) by adjusting precursor and/or loading of Ru. Sub-nanometric Ru catalysts not only exhibit performance different from that of NPs but also follow a different route for N2 activation. The strong intra-cluster interaction of Ru atomic clusters enables the formation of strong interactions of Ru d-orbitals with the σ and π orbitals of N2 molecules, resulting in N2 activation over Ru ACCs to occur more easily than that over Ru NPs. Consequently, Ru ACCs display an unprecedentedly high NH3 synthesis rate and large turnover frequency at mild conditions.
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•Ru size effect at a subnanometer scale on NH3 synthesis was studied•NH3 synthesis rate varies with the Ru size decreasing to sub-nanometric level•Ru atomic clusters could effectively tune the N2 activation pathway
Ammonia synthesis is a structure-sensitive reaction, and its activity depends on the metal size. With the fast development of subnanometer catalysis, it is of great importance to investigate the metal size effect at a subnanometer scale on NH3 synthesis. Hence, we report multiscale Ru catalysts on NH3 synthesis with sizes ranging from single atoms, atomic clusters, sub-nanometric clusters, to nanoparticles. Our studies show that as the size of Ru entities decreases to sub-nanometric level, B5 and/or terrace sites decrease, which leads to a change of N2 activation route. The strong intra-cluster interaction in Ru atomic clusters catalyst induces strong interaction of Ru d-orbitals with the σ and π orbitals of N2 molecules, which results in N2 activation over Ru atomic clusters to occur much more easily than that over Ru nanoparticles. The findings have significant implications for the design of structure-sensitive catalysts for NH3 synthesis under mild conditions.
A series of Ru catalysts were prepared with Ru sizes ranging from single atoms, atomic clusters, sub-nanometric clusters, to nanoparticles. Among them, the sub-nanometric Ru catalysts not only exhibit performance different from that of Ru nanoparticles but also follow a different route for N2 conversion to NH3.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The structure, composition, and atomic distribution of nanoalloys under operating conditions are of significant importance for their catalytic activity. In the present work, we use ab initio ...molecular dynamics simulations to understand the structural behavior of Au–Pd nanoalloys supported on rutile TiO2 under different conditions. We find that the Au–Pd structure is strongly dependent on the redox properties of the support, originating from strong metal–support interactions. Under reducing conditions, Pd atoms are inclined to move toward the metal/oxide interface, as indicated by a significant increase of Pd–Ti bonds. This could be attributed to the charge localization at the interface that leads to Coulomb attractions to positively charged Pd atoms. In contrast, under oxidizing conditions, Pd atoms would rather stay inside or on the exterior of the nanoparticle. Moreover, Pd atoms on the alloy surface can be stabilized by hydrogen adsorption, forming Pd–H bonds, which are stronger than Au–H bonds. Our work offers critical insights into the structure and redox properties of Au–Pd nanoalloy catalysts under working conditions.
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High-valence Ti(iv)-based metallocalixarene coordination cages that are linked by oriented ancillary ligands are unknown so far. Herein, the first family of tunable calixarene-based coordination ...cages of Ti(iv) with a framework formula Ti12(OiPr)12(TBC4)6L6 have been assembled from six {Ti2(OiPr)2(TBC4)}2+ nodes and six pyridinedicarboxylic ligands. Furthermore, the {Ti12L6} cage showed strong photocatalytic H2 evolution activity, and DFT studies were performed to explore its electronic structure.
Inducing the surface enrichment of active noble metal can not only help to stabilize the catalyst but also modify the catalytic performance of the catalyst through electronic and geometric effects. ...Herein, we report the
in situ
surface enrichment of Ir on IrRu alloy during the oxygen evolution reaction (OER). The surface enrichment of Ir was probed by
ex situ
high-resolution transmission electron microscopy (HRTEM),
in situ
X-ray absorption spectroscopy (XAS), and electrochemical Cu stripping, leading to complementary characterizations of the dynamic reconstruction of the IrRu alloy during OER. Guided by the density functional theory (DFT), an IrRu alloy with low Ir content (20 wt%) was constructed, which displayed a low overpotential of only 230 mV to deliver an OER current density of 10 mA cm
−2
in 0.1 M HClO
4
solution and maintained stable performance for over 20 h. To investigate the practical application potential, a proton exchange membrane (PEM) water electrolyzer using the IrRu alloy as the anode catalyst was assembled, which required a low cell voltage of only 1.48 V to generate a current density of 1 A cm
−2
.
Inducing the surface enrichment of active noble metal can not only help to stabilize the catalyst but also modify the catalytic performance of the catalyst through electronic and geometric effects.
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30.
Double σ‑Aromaticity in a Planar Zinc-Doped Gold Cluster: Au9Zn Kulichenko, Maksim; Chen, Wei-Jia; Zhang, Yang-Yang ...
The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory,
06/2021, Volume:
125, Issue:
21
Journal Article
Peer reviewed
The strong relativistic effects result in many interesting chemical and physical properties for gold and gold compounds. One of the most surprising findings has been that small gold clusters prefer ...planar structures. Dopants can be used to tune the electronic and structural properties of gold nanoclusters. Here we report an experimental and theoretical investigation of a Zn-doped gold cluster, Au9Zn–. Photoelectron spectroscopy reveals that Au9Zn– is a highly stable electronic system with an electron binding energy of 4.27 eV. Quantum chemical studies show that the global minimum of Au9Zn– has a D 3h structure with a closed-shell electron configuration (1A1’), which can be viewed as replacing the central Au atom by Zn in the open-shell parent Au10 – cluster. The high electronic stability of Au9Zn– is corroborated by its extremely large HOMO–LUMO gap of 3.3 eV. Chemical bonding analyses revealed that the D 3h Au9Zn– are bonded by two sets of delocalized σ bonds, giving rise to double σ aromaticity and its remarkable stability. Two planar low-lying isomers are also observed, corresponding to a similar triangular structure with the Zn atom on the edge and another one with one of the corner Au atoms moved to the edge of the triangle.
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