Heterometallic AuI 6 AgI 6 Macrocyclic Cluster Templated by a Supramolecular Melamine Dimer

The application of supramolecular templates in aligning atomically precise heterometal arrays is important for pursuing functional materials. Herein, we report that a bilayered supramolecular tri-deprotonated melamine dimer functions as an effective template in the construction of a heterometallic gold(I)-silver(I) macrocyclic cluster [μ6 -(C3 N6 H3 )3- ]2 -AuI 6 AgI 6 . X-ray single crystal structural analysis showed that a crown-like AuI 6 AgI 6 macrocycle is aligned around two parallelly stacked μ6 -(C3 N6 H3 )3- moieties hold together with π-π interactions. Theoretical calculations revealed that the [μ6 -(C3 N6 H3 )3- ]2 motif dominantly contributes to the near-occupied orbitals in the electronic structure, which is closely related to its luminescence properties. This work demonstrates that the supramolecular templates containing multiple symmetric binding sites may present a facile approach in the construction of functional metal clusters.

Alkynyl-Protected Bimetallic Nanoclusters with a Hybrid Mackay Icosahedral Ag42 Cu12 Cl Kernel and an Octahedral Ag22 Cu12 Kernel

A facile strategy that directly reduces alkynyl-silver precursors and copper salts for the synthesis of bimetallic nanoclusters using the weak reducing agent Ph2 SiH2 is demonstrated. Two alkynyl-protected concentric-shell nanoclusters, (Ph4 P)2 [Ag22 Cu12 (C≡CR)28 ] and (Ph4 P)3 [Ag42 Cu12 Cl(C≡CR)36 ] (Ag22 Cu12 and Ag42 Cu12 Cl, R=bis(trifluoromethyl)phenyl), were successfully obtained and characterized by single-crystal X-ray diffraction and electro-spray ionization mass spectrometry. For the first time, a hybrid 55-atom two-shell Mackay icosahedron was found in Ag42 Cu12 Cl, which is icosahedral M54 Cl instead of M55 . The incorporation of a chloride in the metal icosahedron contributes to the stability of the cluster from both electronic and geometric aspects. Alkynyl ligands show various binding-modes including linear "RC≡C-Cu-C≡CR" staple motifs.

Integration of Metal Catalysis and Organocatalysis in a Metal Nanocluster with Anchored Proline

Chiral metal nanoclusters have recently been attracting great attention. It is challenging to realize asymmetric catalysis via atomically precise metal nanoclusters. Herein, we report the synthesis and total structure determination of chiral clusters [Au₇Ag₈(dppf)₃(l-/d-proline)₆](BF₄)₂ (l-/d-Au₇Ag₈). Superatomic clusters l-/d-Au₇Ag₈ display intense and mirror-image Cotton effects in their CD spectra. Density functional theory (DFT) calculations were carried out to understand the correlation between electronic structures and the optical activity of the enantiomeric pair. Surprisingly, the incorporation of proline in a metal nanocluster can significantly promote the catalytic efficiency in asymmetric Aldol reactions. The increase of catalytic activity of Au₇Ag₈ in comparison with organocatalysis by proline is attributed to the cooperative effect of the metal core and prolines, showing the advantages of the integration of metal catalysis and organocatalysis in a metal nanocluster.

Disc-like Silver Nanocluster Ag93 Built with Bicapped Hexagonal Prismatic Ag15 and Ino Decahedral Ag13 Units

The reduction of alkynyl-silver and phosphine-silver precursors with a weak reducing reagent Ph2SiH2 led to the formation of a novel silver nanocluster [Ag93(PPh3)6(C≡CR)50]3+ (R = 4-CH3OC6H4), which is the largest structurally characterized cluster of clusters. This disc-shaped cluster has a Ag69 kernel consisting of a bicapped hexagonal prismatic Ag15 wrapped by six Ino decahedral through edge-sharing. This is the first time to observe that Ino decahedra can be used as building blocks to assemble a cluster of clusters. Moreover, the central silver atom has a coordination number of 14, which is the highest in metal nanoclusters. This work provides a diverse metal packing pattern in metal nanoclusters, which is helpful for the understanding of metal cluster assembling mechanisms.

Structural Engineering toward Gold Nanocluster Catalysis

Atomically precise gold nanoclusters provide great opportunities to explore the relationship between the structure and properties of nanogold catalysts. A nanocluster consists of a metal core and a surface ligand shell, and both the core and shell have significant effects on the catalytic properties. Thanks to their precise structures, the active metal site of the clusters can be readily identified and the effects of ligands on catalysis can be disclosed. In this Minireview, we summarize recent advances in catalytic research of gold nanoclusters, emphasizing four strategies for constructing open metal sites, including by post-treatment, the bulky ligands strategy, the surface geometric mismatch method, and heteroatom doping procedures. We also discuss the effects of ligands on the catalytic activity, selectivity, and stability of gold cluster catalysts. Finally, we present future challenges relating to gold cluster catalysis.

Face-Centered Cubic Silver Nanoclusters Consolidated with Tetradentate Formamidinate Ligands

Growing attention has been paid to nanoclusters with face-centered cubic (fcc) metal kernels, due to its structural similarity to bulk metals. We demonstrate that the use of tetradentate formamidinate ligands facilitate the construction of two fcc silver nanoclusters: [Ag₅₂(5-F-dpf)₁₆Cl₄](SbF₆)₂ (Ag₅₂, 5-F-Hdpf = N,N'-di(5-fluoro-2-pyridinyl)formamidine) and [Ag₅₃(5-Me-dpf)₁₈](NO₃)₅ (Ag₅₃, 5-Me-Hdpf = N,N'-di(5-methyl-2-pyridinyl)formamidine). Single-crystal X-ray structural analysis revealed that the silver atoms in both clusters are in a layer-by-layer arrangement, which can be viewed as a portion of the fcc packing of silver. The nitrogen donors of amidinate ligands selectively passivate the {111} facets. All silver atoms are involved in the fcc packing, that is, no staple motifs are observed due to the linear arrangement of the four N donors of the dpf ligands. The characteristic optical absorption bands of Ag₅₂ and Ag₅₃ have been studied with a time-dependent density functional theory. This work provides a facile access to assembling atomically precise fcc-type nanoclusters and shows the prospect of amidinates as protecting ligands in synthesizing metal nanoclusters.

Identification of the Active Species in Bimetallic Cluster Catalyzed Hydrogenation

Identification of the authentic active species of cluster catalysis is rather challenging, and direct structural evidence is quite valuable and difficult to obtain. Two "isostructural" clusters, Ag₂₅Cu₄Cl₆(dppb)₆(PhC≡C)₁₂(SO₃CF₃)₃ (1) and Ag₂₅Cu₄Cl₆H₈(dppb)₆(PhC≡C)₁₂(SO₃CF₃)₃ (2_H) (dppb is 1,4-bis(diphenylphosphine)butane), have been successfully isolated and structurally characterized. Both these clusters have a centered icosahedron Ag₁₃ core with the same peripheral composition and structure. The only difference is that 2_H has eight hydrides but 1 has none, that is, the kernels are Ag₁₃⁵⁺ and Ag₁₃H₈⁵⁺ in 1 and 2_H, respectively. The catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as a model reaction is assessed with the two clusters. Cluster 2_H is very active with 100% yield within 2 h, whereas 1 shows a very low conversion (∼8%) under the same conditions. Interestingly, high catalytic activity was observed when 1 was converted to 2_H with the oxidation of H₂O₂ under catalytic conditions. The unprecedented transformation of a reduced nanocluster to an Ag(I)Cu(I) bimetallic cluster compound provides an excellent platform to determine the real active cluster in terms of metal cluster catalysis. The present work presents clear structural evidence that the catalytic performance of metal nanoclusters can be modulated by properly regulating the oxidation state of their constituted metal atoms.

[Arf6 regulates endometriotic epithelial-mesenchymal transition and mitochondrial distribution]

Objective: To investigate the role of adenosine diphosphate ribosylation factor 6 (Arf6) in the pathogenesis of endometriosis. Methods: Endometrial tissues were sampled from women who were hospitalized in the Affiliated Hospital of Medical School of Ningbo University and Ningbo Women and Children's Hospital from November 2020 to May 2021 with endometriosis (n=44, endometriosis group) and without endometriosis (n=17, control group). The expression of Arf6 protein in the endometrial tissues was detected by western blot. Endometrial epithelial cells from both groups were primary cultured and the distribution of intracellular mitochondria was detected by immunofluorescence. The expression of Arf6 protein was down-regulated by small interference RNA (siRNA), the distribution of mitochondria in cells with decreased Arf6 protein expression was observed, and the expression of mitochondria-related proteins development and differentiation enhancing factor 1 (DDEF1, also called AMAP1), reactive oxygen species 1 (ROS1) and epithelial-mesenchymal transition (EMT)-related proteins E-cadherin, vimentin were detected. Transwell assay was used to detect the changes in the migration ability of the cells. Results: Compared with the control group, ectopic endometrial tissue of endometriosis group showed high expression of Arf6 protein (0.174±0.019 vs 0.423±0.033; t=29.630, P<0.01); and in ectopic endometrial epithelial cells, mitochondria were distributed near the edge of the cell membrane. While Arf6 expression was down-regulated by siRNA, the distribution of mitochondria in ectopic cells returned to natural, close to the control level. In addition, the expression levels of AMAP1 and ROS1 in ectopic cells after Arf6 protein knockdown were significantly decreased. Transwell assay results indicated that knockdown of Arf6 could reduce the migration ability of ectopic epithelial cells [migration cell count: (34.3±7.5) cells]; and immunofluorescence verified low expression of E-cadherin but high expression of vimentin in ectopic epithelial cells, whereas knockdown of Arf6 protein E-cadherin expression increased but vimentin expression decreased. Conclusions: High expression of Arf6 protein in ectopic endometrial epithelial cells leads to the distribution of mitochondria tending to membrane marginalization, while inducing EMT, which are involved in the mechanism of endoheterosis pathogenesis.

Anion-Directed Regulation of Structures and Luminescence of Heterometallic Clusters

Anions have been used to regulate the structures and luminescence of heterometallic clusters. Introducing ClO₄ ^- into orange-emissive, butterfly-like [(C)(Au-PPhpy₂ )₆ Ag₄ ](BF₄ )₆ (1, PPhpy₂ =bis(2-pyridyl)phenylphosphine) leads to the formation of red-emissive [(C)(Au-PPhpy₂ )₆ Ag₅ (ClO₄ )₃ ](ClO₄ )₄ (2) with a novel trigonal bipyramidal structure; employing PhCO₂ ^- gives yellow-emissive, hexagram-like [(C)(Au-PPhpy₂ )₆ Ag₆ (PhCO₂ )₃ ](BF₄ )₅ (3). Notably, 1 exhibits weak luminescence in CH₂ Cl₂ /CH₃ OH=1 : 1 (v : v) with a quantum yield (QY) of 0.05, whereas it was dramatically increased to 0.49 and 0.83 for 2 and 3, respectively. Theoretical calculation confirms that the involvement of anions in the electronic structures is responsible for the shifts of emission. The high QYs of 2 and 3 are attributed to the protection provided by ligands and anions. This work demonstrates that anions may serve as an extra designable factor beyond just counterions for functional metal clusters.

[Development of a Ranking Tool for Scientificity, Transparency and Applicability of Clinical Practice Guidelines]

Objective: To address the limitations of existing methods and tools for evaluating clinical practice guidelines, we aimed to develop a comprehensive instrument focusing on the three main dimensions of guideline development: scientificity, transparency, applicability. We will use it to rank the guidelines according to the scores. We abbreviated it as STAR, and its reliability, validity and usability were also tested. Methods: A multidisciplinary expert working group was set up, including methodologists, statisticians, journal editors, medical professionals, and others. Scoping review, Delphi methods and hierarchical analysis were used to determine the final checklist of STAR. Results: The new instrument contained 11 domains and 39 items. Intrinsic reliability of each domain was indicated by Cronbach's α coefficient, with a average value of 0.646. The Cohen's kappa coefficients for methodological evaluators and clinical evaluators were 0.783 and 0.618. The overall content validity index was 0.905. The R2 for the criterion validity analysis was 0.76. The average score for usability of the items was 4.6, and the mean time spent to evaluate each guideline was 20 minutes. Conclusion: The instrument has good reliability, validity and evaluating efficiency, and can be used for evaluating and ranking guidelines more comprehensively.

Nitrogen Donor Protection for Atomically Precise Metal Nanoclusters

Surface organic ligands are critical in dictating the structures and properties of atomically precise metal nanoclusters. In contrast to the conventionally used thiolate, phosphine and alkynyl ligands, nitrogen donor ligands have not been used in the protection for well-defined metal nanoclusters until recently. This review focuses on recent developments in atomically precise metal nanoclusters stabilized by different types of nitrogen donor ligands, in which the synthesis, total structure determination and various properties are covered. We hope that this review will provide insights into the rational design of N donor-protected metal nanoclusters in terms of structural and functional modulation.

Structural transformation and catalytic hydrogenation activity of amidinate-protected copper hydride clusters

Copper hydrides are important hydrogenation catalysts, but their poor stability hinders the practical applications. Ligand engineering is an effective strategy to tackle this issue. An amidinate ligand, N,N'-Di(5-trifluoromethyl-2-pyridyl)formamidinate (Tf-dpf) with four N-donors has been applied as a protecting agent in the synthesis of stable copper hydride clusters: Cu₁₁H₃(Tf-dpf)₆(OAc)₂ (Cu₁₁) with three interfacial μ₅-H and [Cu₁₂H₃(Tf-dpf)₆(OAc)₂]·OAc (Cu₁₂) with three interstitial μ₆-H. A solvent-triggered reversible interconversion between Cu₁₁ and Cu₁₂ has been observed thanks to the flexibility of Tf-dpf. Cu₁₁ shows high activity in the reduction of 4-nitrophenol to 4-aminophenol, while Cu₁₂ displays very low activity. Deuteration experiments prove that the type of hydride is the key in dictating the catalytic activity, for the interfacial μ₅-H species in Cu₁₁ are involved in the catalytic cycle whereas the interstitial μ₆-H species in Cu₁₂ are not. This work highlights the role of hydrides with regard to catalytic hydrogenation activity.

Ligand Engineering toward the Trade-Off between Stability and Activity in Cluster Catalysis

We report the structures, stability and catalysis properties of two Ag₂₁ nanoclusters, namely [Ag₂₁ (H₂ BTCA)₃ (O₂ PPh₂ )₆ ]SbF₆ (1) and [Ag₂₁ (C≡CC₆ H₃ -3,5-R₂ )₆ (O₂ PPh₂ )₁₀ ]SbF₆ (2) (H₄ BTCA=p-tert-butylthiacalix[4]arene, R=OMe). Both Ag₂₁ structures possess an identical icosahedral kernel that is surrounded by eight peripheral Ag atoms. Single-crystal structural analysis and ESI-MS revealed that 1 is an 8-electron cluster and 2 has four free electrons. Theoretical results show that the P-symmetry orbitals are found as HOMO-1 and HOMO states in 1, and the frontier unoccupied molecular orbitals (LUMO, LUMO+1 and LUMO+2) show D-character, indicating 1 is a superatomic cluster with an electronically closed shell 1S² 1P⁶ , while 2 has an incomplete shell configuration 1S² 1P² . These two Ag₂₁ clusters show superior stability under ambient conditions, and 1 is robust even at 90 °C in toluene and under oxidative conditions (30 % H₂ O₂ ). Significantly, 2 exhibits much higher activity than 1 as catalyst in the reduction of 4-nitrophenol. This work demonstrates that ligands can influence the electronic structures of silver clusters, and further affect their stability and catalytic performance.

A 59-Electron Non-Magic-Number Gold Nanocluster Au99(C≡CR)40 Showing Unexpectedly High Stability

An atomically resolved gold nanocluster Au₉₉(C≡CC₆H₃-2,4-F₂)₄₀ (Au₉₉) with an unusual 59 valence electrons has been synthesized. Single-crystal X-ray diffraction reveals that its Au₇₉ kernel is a Au₄₉ Marks decahedron capped by two Au₁₅ units. The surface structure of Au₉₉ consists of 20 linear Au(C≡CR)₂ staples. Intercluster interactions are observed between these D₅ symmetric clusters. The existence of an unpaired electron is verified by magnetic measurement. Interestingly, this open-shell gold cluster Au₉₉ stays intact in toluene solution at 80 °C for more than a week, and it has good charging-discharging capability under electrochemical conditions. The compact ligand shell protection around the symmetric core accounts for the high stability. This work suggests that geometric factors may play a crucial role in determining the stability of a metal nanocluster, even though the cluster has an open-shell electronic structure.

Superatomic Orbital Splitting in Coinage Metal Nanoclusters

The superatomic orbital splitting (SOS) method is developed to understand the electronic structures of coinage metal nanoclusters, in which delocalized electron counts are not magic numbers. Because the symmetry of a metal core can significantly affect the electronic structure of a nanocluster, this method takes the shape of the core into account in determining the order of group orbital levels. By taking nanoclusters as superatoms, a highly positively charged core is established by removing the ligands and staples. The superatomic orbitals split into group orbitals at different energy levels because of the nonspherical shape of the cluster core. Therefore, the electron configuration of the nonmagic-number nanocluster can be qualitatively analyzed without quantum chemical calculations, which is very important for understanding the stability of the cluster.

Site-Specified Doping of Silver Atoms into Au25 Nanocluster as Directed by Ligand Binding Preference

For the first time site-specific doping of silver into a spherical Au₂₅ nanocluster has been achieved in [Au₁₉Ag₆(MeOPhS)₁₇(PPh₃)₆] (BF₄)₂ (Au₁₉Ag₆) through a dual-ligand coordination strategy. Single crystal X-ray structural analysis shows that the cluster has a distorted centered icosahedral Au@Au₆Ag₆ core of D₃ symmetry, in contrast to the I_h Au@Au₁₂ kernel in the well-known [Au₂₅(SR)₁₈]⁻ (R = CH₂CH₂Ph). An interesting feature is the coexistence of [Au₂(SPhOMe)₃] dimeric staples and [P–Au–SPhOMe] semi-staples in the title cluster, due to the incorporation of PPh₃. The observation of only one double-charged peak in ESI-TOF-MS confirms the ordered doping of silver atoms. Au₁₉Ag₆ is a 6e system showing a distinct absorption spectrum from [Au₂₅(SR)₁₈]⁻, that is, the HOMO–LUMO transition of Au₁₉Ag₆ is optically forbidden due to the P character of the superatomic frontier orbitals.

For the first time site-specific doping of silver into a spherical Au₂₅ nanocluster has been achieved in [Au₁₉Ag₆(MeOPhS)₁₇(PPh₃)₆] (BF₄)₂. It is a 6e system showing quite a different absorption spectrum from [Au₂₅(SR)₁₈]⁻.

Molecular Gold Nanocluster Au156 Showing Metallic Electron Dynamics

The boundary between molecular and metallic gold nanoclusters is of special interest. The difficulty in obtaining atomically precise nanoclusters larger than 2 nm limits the determination of such a boundary. The synthesis and total structural determination of the largest all-alkynyl-protected gold nanocluster (Ph₄P)₆[Au₁₅₆(C≡CR)₆₀] (R = 4-CF₃C₆H₄-) (Au₁₅₆) are reported. It presents an ideal platform for studying the relationship between the structure and the metallic nature. Au₁₅₆ has a rod shape with the length and width of the kernel being 2.38 and 2.04 nm, respectively. The cluster contains a concentric Au₁₂₆ core structure (Au₄₆@Au₅₀@Au₃₀) protected by 30 linear RC≡C-Au-C≡CR staple motifs. It is interesting that Au₁₅₆ displays multiple excitonic peaks in the steady-state absorption spectrum (molecular) and pump-power-dependent excited-state dynamics as revealed in the transient absorption spectrum (metallic), which indicates that Au₁₅₆ is a critical crossover cluster for the transition from molecular to metallic state. Au₁₅₆ is the smallest-sized gold nanocluster showing metal-like electron dynamics, and it is recognized that the cluster shape is one of the important factors determining the molecular or metallic nature of a gold nanocluster.

Ligand-Protected Au55 with a Novel Structure and Remarkable CO2 Electroreduction Performance

A Au₅₅ nanocluster with the composition of [Au₅₅ (p-MBT)₂₄ (Ph₃ P)₆ ](SbF₆ )₃ (p-MBT=4-methylbenzenethiolate) is synthesized via direct reduction of gold-phosphine and gold-thiolate precursors. Single-crystal X-ray diffraction reveals that this Au₅₅ nanocluster features a face-centered cubic (fcc) Au₅₅ kernel, different from the well-known two-shell cuboctahedral arrangement in Au₅₅ (Ph₃ P)₁₂ Cl₆ . The Au₅₅ cluster shows a wide optical absorption band with optical energy gap (E_g =1.28 eV). It is found that the exclusion of chloride is crucial for the formation of the title cluster, otherwise rod-like [Au₂₅ (SR)₅ (PPh₃ )₁₀ Cl₂ ]²⁺ is obtained. The strategy to run synthetic reaction in the absence of halide leads to new members of phosphine/thiolate co-protected metal nanoclusters. The Au₅₅ nanocluster exhibits high catalytic activity and selectivity for electrochemical reduction of CO₂ to CO; the Faradaic efficiency (FE) reaches 94.1 % at -0.6 V vs. reversible hydrogen electrode (RHE).

Rod-Shaped Silver Supercluster Unveiling Strong Electron Coupling between Substituent Icosahedral Units

The first linear silver supercluster based on icosahedral Ag₁₃ units has been constructed via bridging of dpa ligands: Ag₆₁(dpa)₂₇(SbF₆)₄ (Hdpa = dipyridylamine) (Ag₆₁). Single-crystal X-ray diffraction reveals that this rod-shaped cluster consists of four vertex-sharing Ag₁₃ icosahedra in a linear arrangement. This Ag₆₁ cluster represents the longest one-dimensional metal nanocluster with a resolved structure. Unprecedented electron coupling develops between their constituent Ag₁₃ units. Theoretical studies disclose that the stabilities of the two superclusters are dictated by a strong interaction between the Ag₁₃ units as well as the ligand effect of the dpa-Ag motifs. The quantum size effect accounts for the significant enhancement of the metal-related absorptions and the red shift at the near-infrared region as the length of the cluster increases. This work sheds light on the evolution of one-dimensional materials and an understanding of the electronic communication between the constituent clusters.

Robust Gold Nanocluster Protected with Amidinates for Electrocatalytic CO2 Reduction

The first all-amidinate-protected gold nanocluster [Au₂₈ (Ph-form)₁₂ ](OTf)₂ (Ph-form=N,N'-diphenylformamidinate) (Au₂₈ ) has been synthesized and structurally resolved. Single crystal X-ray diffraction reveals that Au₂₈ has a compact Au₄ @Au₂₄ tetrahedral core-shell structure of T symmetry, which is fully protected by 12 bridging formamidinate ligands. This cluster is quite robust as indicated by the fact that it can stay intact in solution at 80 °C for 6 d. It exhibits excellent catalytic performance for the electroreduction of CO₂ with 96.5 % Faradaic efficiency (FE) at -0.57 V and a maximum TOF of 1731 h^-1 at -0.87 V. Its superior stability is also manifested in the fact that the supported catalyst Au₂₈ /CNTs maintains stable potentials at ca. -0.69 V for 40 h with FE(CO)s>91 %. A superatomic electron configuration of 1S² 1P⁶ 2S² 1D⁴ has been clarified by DFT computations, and the strong gold-ligand binding and geometric shell closure account for the superior stability of Au₂₈ .

Heterometallic Coinage Metal Acetylenediide Clusters Showing Tailored Thermochromic Luminescence

Acetelyenediide (C₂ ^2- ) species have been encapsulated in bimetallic and trimetallic clusters: [(AuL)₆ Ag₇ (C≡C)₃ ](BF₄ )₇ (2) and [(AuL)₆ AgCu₆ (C≡C)₃ ](BF₄ )₇ (3), L=phenylbis(2-pyridyl)phosphine (PPhpy₂ ). Single-crystal X-ray diffraction analysis revealed that they are isostructural and six silver atoms in 2 are replaced with copper in 3. Both clusters have a trefoil skeleton, which can be viewed as three trigonal bipyramidal (LAu-C≡C-AuL)M₂ Ag (M=Ag/Cu) motifs sharing a common silver atom. TDDFT calculations showed Cu-doping significantly increases the energy level of (C₂ -Cu)-involved occupied orbital, thus inducing interesting transition coupling of dual-emission at low temperature. This work not only provides a strategy for constructing heterometallic clusters, but also shows the prospect for pursuing novel thermochromic luminescent materials by incorporating multi-congeneric metal components.

Cluster From Cluster: A Quantitative Approach to Magic Gold Nanoclusters [Au25 (SR)18 ]. Angew Chem Int Ed Engl 2021;60:14415-14419. [PMID: 33829603 DOI: 10.1002/anie.202103290]

High-yield and large-scale synthesis are highly demanded for the studies of gold nanoclusters. We developed a "cluster from cluster" approach to assemble gold nanoclusters with preformed atomically precise Au₁₃ precursors. This facile approach has proved to be very effective in the synthesis of the well-known magic cluster [Au₂₅ (SR)₁₈ ]^- , which could prepare the target cluster in high yield (overall yield up to ≈100 %) at large scale (gram-scale based on gold). This method can be applied in the synthesis of 10 Au₂₅ clusters with different R groups. This work presents an important approach that may be extended to high-yield and large-scale synthesis of other metal nanoclusters.

A stable well-defined copper hydride cluster consolidated with hemilabile phosphines

Copper hydrides are very useful in hydrogenation reactions. We report a stable Stryker-type copper hydride reagent protected by hemilabile phosphines: [Cu8H6(dppy)6](OTf)2 (Cu8-H, dppy = diphenylphosphino-2-pyridine). The metal core of this cluster has a bicapped octahedral configuration, and the copper-bound hydrides each triply bridges over a triangular face of the octahedron. This cluster is attractive due to its facile preparation and excellent stability under ambient conditions. The comparable activity and selectivity both in the stoichiometric and catalytic reactions make Cu8-H a promising alternative to Stryker's reagent.

Enriching Structural Diversity of Alkynyl-Protected Gold Nanoclusters with Chlorides

The synthesis and isolation of alkynyl/chloride-protected gold nanoclusters is described. Silica gel column chromatography is effective in isolating gold nanoclusters from the as-synthesized cluster mixture to give the clusters Na[Au₂₅ L₁₈ ] (Au₂₅ ), [HNEt₃ ]₃ [Au₆₇ L₃₂ Cl₄ ] (Au₆₇ ), [HNEt₃ ]₄ [Au₁₀₆ L₄₀ Cl₁₂ ] (Au₁₀₆ ), L=3,5-bis(trifluoromethyl)-phenylacetylide. Au₆₇ and Au₁₀₆ are new clusters; the structures were determined by X-ray single-crystal diffraction. Au₆₇ contains a distorted Au₁₈ Marks decahedron shelled by an irregular Au₃₂ and further protected with two V-shaped Au₂ L₃ , 13 linear AuL₂ staples and 4 chlorides. Au₆₇ is the first structurally determined 34e superatomic gold nanocluster. Au₁₀₆ is composed of 106 Au atoms co-protected by alkynyls and chlorides. It has a Au₇₉ kernel, like in Au₁₀₂ (p-MBA)₄₄ . The surface structure of Au₁₀₆ includes 20 linear Au-alkynyl staples, 5 Cl-Au-Cl and 2 Cl-Au motifs. These three gold nanoclusters show size-dependent electrochemical properties.

Atomically Precise Preorganization of Open Metal Sites on Gold Nanoclusters with High Catalytic Performance

Gold nanoclusters with surface open sites are crucial for practical applications in catalysis. We have developed a surface geometric mismatch strategy by using mixed ligands of different type of hindrance. When bulky phosphine Ph₃ P and planar dipyridyl amine (Hdpa) are simultaneously used, steric repulsion between the ligands will reduce the ligand coverage of gold clusters. A well-defined access granted gold nanocluster [Au₂₃ (Ph₃ P)₁₀ (dpa)₂ Cl](SO₃ CF₃ )₂ (Au₂₃ , dpa=dipyridylamido) has been successfully synthesized. Single crystal structural determination reveals that Au₂₃ has eight uncoordinated gold atoms in the shape of a distorted bicapped triangular prism. The accessibility of the exposed Au atoms has been confirmed quantitatively by luminescent titration with 2-naphthalenethiol. This cluster has excellent performance toward selective oxidation of benzyl alcohol to benzaldehyde and demonstrates excellent stability due to the protection of negatively charged multidentate ligand dpa.

Total Structure Determination of the Largest Alkynyl-Protected fcc Gold Nanocluster Au110 and the Study on Its Ultrafast Excited-State Dynamics

Great attention has been paid to nanoclusters having face-centered-cubic (fcc) metal kernels, because of the similarity of metal packing to that of bulk gold. So far, there is no precedent example of an all-alkynyl-protected fcc gold nanocluster with more than 100 gold atoms. We report the synthesis and total structure determination of an alkynyl-protected gold nanocluster [NEt₃H]₂[Au₁₁₀(p-CF₃C₆H₄C≡C)₄₈] (Au₁₁₀). It has an fcc Au₈₆ kernel with 24 peripheral Au(C≡CR)₂ staples. The Au₈₆ kernel consists of six close packing layers in the pattern of Au₆:Au₁₆:Au₂₁:Au₂₁:Au₁₆:Au₆. Electronic absorption spectroscopy shows Au₁₁₀ has a molecular-like discrete electronic structure, and transient absorption experiments reveal its nonmetallic nature.

[Establishment of nomogram predicting model for the death risk of extremely severe burn patients and the predictive value]

Objective: To explore the death risk factors of extremely severe burn patients, establish a death risk nomogram predicting model, and investigate the predictive value for death risk of extremely severe burn patients. Methods: The medical records of 231 extremely severe burn patients (190 males and 41 females, aged 18-60 years) who were admitted to the Institute of Burn Research of the First Affiliated Hospital of Army Medical University from January 2010 to October 2018 and met the inclusion criteria were analyzed retrospectively. According to the final outcome, the patients were divided into survival group of 173 patients and death group of 58 patients. The sex, age, severity of inhalation injury, total burn area, full-thickness burn area, burn index, rehydration coefficient and urine volume coefficient of the first and second 24 h after injury, the first base excess, shock index, and hematocrit (HCT) after admission, whether to have pre-hospital fluid infusion, use of ventilator, and use of continuous renal replacement therapy (CRRT), and abbreviated burn severity index (ABSI ) and Baux score on admission of patients in the two groups were recorded or calculated. According to the use of ventilator, the patients were divided into with ventilator group of 131 patients and without ventilator group of 100 patients, and the death, total burn surface area, burn index, incidence and severity of inhalation injury were recorded. According to the use of CRRT, the patients were divided into with CRRT group of 59 patients and without CRRT group of 172 patients, and the death, total burn surface area, and burn index were recorded. Data were statistically analyzed with t test, chi-square test, and Mann-Whitney U test to screen the death related factors of patients. The indexes with statistically significant differences between survival group and death group were included in the multivariate logistic regression analysis to screen the independent death risk factors of patients, and the death risk nomogram predicting model was constructed based on the results.The Bootstrap method was used to validate the death risk nomogram predicting model internally. The predictive value of the nomogram model for predicting death risk of patients was detected by drawing calibration graph and calculating concordance index, and the death risk scores of 231 patients were acquired according to the death risk nomogram model. The receiver's operating characteristic (ROC) curve was drawn, and the optimal threshold and the sensitivity and specificity of optimal threshold in the ROC curve and the area under the curve were calculated. Results: (1) There were statistically significant differences in burn index, ABSI on admission, severity of inhalation injury, total burn area, full-thickness burn area, rehydration coefficient at the first 24 h after injury, use of ventilator, use of CRRT, and Baux score on admission of patients between the two groups (Z=-7.696, -7.031, χ(2)=18.304, 63.065, 23.300, 13.073, 34.240, 59.586, t=-7.536, P<0.01). (2) There were statistically significant differences in death, incidence and severity of inhalation injury, total burn area, and burn index of patients between with ventilator group and without ventilator group (χ(2)=34.240, 17.394, 25.479, Z=-6.557, -7.049, P<0.01). (3) There were statistically significant differences in death, total burn area, and burn index of patients between with CRRT group and without CRRT group (χ(2)=62.982, Z= -47.421, -6.678, P<0.01). (4) The use of ventilator, use of CRRT, and burn index were independent risk factors for the death of extremely severe burn patients (odds ratio=3.277, 5.587, 1.067, 95% confidence interval=1.073-10.008, 2.384-13.093, 1.038-1.096, P<0.05 or P<0.01). (5) The initial concordance index of nomogram predicting model was 0.90 and the corrected concordance index was 0.89. The concordance indexes before and after correction were higher and similar, which showed that the nomogram had good concordance and predictive effect. The optimum threshold of ROC curve was 0.23, the sensitivity and specificity of optimum threshold were 86.0% and 80.0%, respectively, and the area under ROC curve was 0.90 (95% confidence interval=0.86-0.94, P<0.01). Conclusions: Severe burns and damage and/or failure of organ are the main death causes of extremely severe burn patients. The death risk nomogram predicting model established on the basis of use of ventilator, use of CRRT, and burn index have good predictive ability for death of extremely severe burn patients.

Homoleptic alkynyl-protected gold nanoclusters with unusual compositions and structures

We report two novel homoleptic alkynyl-protected gold nanoclusters, which were synthesized by direct reduction of AuC[triple bond, length as m-dash]CR. Single-crystal X-ray structural analysis reveals that they have compositions of Au42(C[triple bond, length as m-dash]CC6H4-2-CF3)22 (1) and Au50(C[triple bond, length as m-dash]C6H4-3-F)26 (2), respectively. Cluster 2 is the first Au50 nanocluster, and the metal-to-ligand ratios of 1 and 2 are different from those of known Aun(SR)m or Aux(C[triple bond, length as m-dash]CR)y nanoclusters. In addition, the metal kernels of these two clusters are built up unprecedented units. This work offers further insights into the synthesis of all-alkynyl-protected gold nanoclusters via a direct reduction method.

Notch signaling is involved in regulation of LPS-induced macrophage apoptosis through JNK/NF-kB signaling pathway

Notch signaling plays a critical role in the development and function of macrophages. The aim of the present study was to investigate the relationship between Notch signaling pathway and macrophage apoptosis after LPS stimulation. In RAW 264.7 cells, the mRNA expression of Jagged1, Hes1, Hes 5 and GM-CSF, and protein expression of NICD1 and GM-CSF were increased after LPS stimulation. Inhibition of Notch signaling by γ-secretase inhibitor DAPT and the suppression of Notch1 expression using siRNA both significantly prevented LPS induced activation of JNK and NF-kB, and simultaneously the expression of GM-CSF was also down regulated significantly. JNK inhibitor SP600125 was used to block the phosphorylation of JNK signaling, Western blot results showed that the activation of NF-kB was blocked and expression of GM-CSF was down-regulated. Finally, flow cytometry analyses showed that the Notch signaling was involved in the regulation of macrophage apoptosis after LPS stimulation. Our study showed that the Notch signaling pathway was activated and involved in the regulation of macrophage apoptosis after LPS stimulation through JNK/ NF-kB signaling regulated GM-CSF expression.

Isomerization in Alkynyl-Protected Gold Nanoclusters

We report the controlled synthesis and structures of two isomeric gold nanoclusters, whose compositions are determined to be Au₂₃(C≡CBu^t)₁₅ (denoted as Au₂₃-1 and Au₂₃-2) by single-crystal X-ray diffraction and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. This is the first time isomerism is discovered in alkynyl-protected gold nanoclusters. The metal-to-ligand ratios in these two clusters are different from known Au_n(SR)_m systems and have not been observed in the Au_x(C≡CPh)_y family. This pair of isomers exhibits different optical properties, although they have similar structures and identical components. For both Au₂₃ clusters, time-dependent density functional theory calculations revealed the frontier orbitals highest occupied molecular orbital (HOMO)-1, HOMO, and lowest unoccupied molecular orbital (LUMO) are mainly constructed from the Au₁₅ kernel and V-shaped alkynyl-gold motifs. The HOMO → LUMO transition of Au₂₃-1 is optically forbidden, whereas it is allowed in Au₂₃-2. It is also found that Au₂₃-2 cluster can be transformed to Au₂₃-1 spontaneously under ambient conditions. This work offers further insight into the synthesis and isomerism of all-alkynyl-protected gold nanoclusters and will stimulate more investigation of isomeric metal nanoclusters.

Ultrastable hydrido gold nanoclusters with the protection of phosphines

Two phosphine-protected gold nanoclusters with an unprecedented hetero superatomic Au₂₀ core have been isolated. The presence of hydrides is evidenced by mass spectrometry and NMR spectroscopy.

[Au7Ag9(dppf)3(CF3CO2)7BF4]n: a linear nanocluster polymer from molecular Au7Ag8 clusters covalently linked by silver atoms

We report the total structure determination of a covalently bonded nanocluster polymer [Au7Ag9(dppf)3(CF3CO2)7BF4]n (1). This features a one-dimensional linear chain, consisting of unique molecular building blocks, Au7Ag8(dppf)3(CF3CO2)7 clusters, which are linked together by Ag-O bonds rather than Au-Au interactions or bidentate organic bridges as previously reported.

The stability enhancement factor beyond eight-electron shell closure in thiacalix[4]arene-protected silver clusters

Destroying coordination open sites may significantly enhance the stability of metal nanoclusters.

We report the synthesis and structures of two 34-atom metal nanoclusters, namely [Ag₃₄(BTCA)₃(C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CBu^t)₉(tfa)₄(CH₃OH)₃]SbF₆ and [AuAg₃₃(BTCA)₃(C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> CBu^t)₉(tfa)₄(CH₃OH)₃]SbF₆, where H₄BTCA is p-tert-butylthiacalix[4]arene and tfa is trifluoroacetate. Their compositions and structures have been determined by single-crystal X-ray structural analysis and ESI-MS. The cationic cluster consists of a centered icosahedron M@Ag₁₂ (M = Ag or Au) core that is surrounded by 21 peripheral silver atoms. Surrounding protection is provided by four kinds of ligands, including three BTCA, nine ^tBuC Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C, four tfa, and three methanol solvent ligands. It was found that the Ag₅@BTCA μ₅-coordination motif of thiacalixarene is critical for high stability of the title clusters, and extra stability enhancement can be achieved by doping a gold atom at the center of the silver cluster. This work suggests that coordination saturation should be taken into account in addition to electronic and geometric factors for analyzing metal nanocluster stabilities.

Monitoring the growth of Ag–S clusters through crystallization of intermediate clusters

We report a series of Ag–S nanoscale clusters in an attempt to understand the growth process of Ag₂S clusters.

[Anemia status of Chinese rural women of reproductive age in 2012]

Objective: To study the hemoglobin concentration, anemia status and its determinant factors among Chinese rural women of reproductive age in 2012. Methods: This was a cross-sectional study. The data was obtained from the National Free Preconception Health Examination Project (NFPHEP). A total of 712 101 Chinese rural reproductive age women aged 21-49 years old who came from 193 counties of 30 provinces were included. The demographic characteristics were obtained from questionnaires. Hemoglobin concentration was measured using the cyanomethemoglobin method. The definition of anemia we used was recommended by World Health Organization, and was adjusted according to altitude level. The hemoglobin concentration level, the prevalence of anemia and its 95% CI was calculated. Determinant factors of anemia such as demographic characteristics and histories of pregnancy and miscarriage were analyzed using logistic regression. Results: In 2012, the level of hemoglobin concentration in Chinese rural women of reproductive age was (127.77±13.47) g/L, with the lowest in 21-24 years group, which was (127.54±13.54) g/L, and highest in 35-39 years group, which was (128.39±14.12) g/L. In terms of region, the hemoglobin concentration level was lowest in central south, which was (125.79±12.00) g/L, and highest in southwest, which was (129.91±14.37) g/L. The prevalence of anemia in Chinese rural women of reproductive age was 24.80%, with the highest seen in 21-24 years, which was 25.92% (95% CI: 25.74%-26.11%), and lowest in 30-34 years, which was 23.61% (95% CI: 23.37%-23.85%). The prevalence in northwest (28.31%, 95% CI: 28.01%-28.61%) was the highest among all regions, and the prevalence in east (20.88%, 95% CI: 20.68%-21.09%) was the lowest. Conclusions: The prevalence of anemia in Chinese rural reproductive age women was 24.80% in 2012. The anemia prevalence was higher among women who were young, had low educational level, and lived in northwest region.

Alkynyl Approach toward the Protection of Metal Nanoclusters

The past decades have witnessed great advances in the synthesis, structure determination, and properties investigation of coinage metal nanoclusters. These monodisperse clusters have well-defined molecular structures, which is advantageous in correlating structures and properties. Metal nanoclusters are large molecules consisting of many components, so it is a big challenge to prepare them in a rational way. Strenuous efforts have been made to control their geometric and electronic structures, in order to optimize their various properties. A metal nanocluster normally contains a metal core and a peripheral ligand shell. The ligands do not only function as simple stabilizing agents. It has been revealed that these ligands are able to influence the formation processes of the nanoclusters, and they may also dictate the sizes, shapes, and properties of nanoclusters. There are mainly three types of ligands that are widely used as surface anchors on coinage metal nanoclusters: thiolates, phosphines, and halides. Recent ligand engineering has extended the scope to alkynyl ligands. As alkynyl ligands are versatile in interacting with metal atoms, interesting alkynyl-metal interfacial structures including linear, L-shaped, and V-shaped staple motifs can be generated, as well as a series of novel coinage metal nanoclusters that exhibit intriguing molecular geometries. The staple motifs do not simply resemble the surface structures of thiolate-protected nanoclusters, because the incorporation of alkynyl ligands may significantly alter diverse properties of nanoclusters. Compared with thiolate-protected gold nanoclusters, alkynyl-protected ones with identical metal cores exhibit distinctly different absorption profiles and show much improved catalytic activities for semihydrogenation of alkynes. In addition, the participation of alkynyl ligands could profoundly affect the luminescent properties of nanoclusters. These "ligand effects" are mainly attributed to the different nature of alkynyl ligands, as electronic perturbation through π-conjugated units may largely modulate the electronic structure of the whole cluster. In this Account, we describe the development of coinage metal nanoclusters protected with alkynyl ligands. We will first briefly bring up the emergence of alkynyl ligands as anchoring groups on the surfaces of nanoclusters. Then we present the direct reduction method for the synthesis of the following four categories of nanoclusters: (a) gold nanoclusters with mixed-ligand shells, (b) all alkynyl-protected gold nanoclusters, (c) heterobimetallic gold nanoclusters, and (d) silver nanoclusters. Their molecular structures are described, and their various alkynyl-metal interfacial structures are compared with thiolate-metal staples. Finally, ligand effects on the properties of the clusters, including optical absorption, luminescence, and catalysis, are discussed. The alkynyl ligands play an important role in terms of both structural and property aspects. We believe this Account will attract increasing attention to alkynyl ligands, which have shown promising potential in generating new structures and properties of coinage metal nanoclusters.

Vitamin D Status and Patient Outcomes after Knee or Hip Surgery: A Meta-Analysis

BACKGROUND

This study evaluates the effect of vitamin D status in patient outcomes after hip or knee joint surgery.

METHOD

Literature search was carried out in electronic databases, and study selection followed predetermined eligibility criteria. Data were extracted from relevant studies and meta-analyses of standardized mean differences between hypovitaminosis D (vitamin D deficiency or insufficiency) and euvitaminosis D in assessment scores of patient-reported outcomes were performed.

RESULTS

A total of 12 studies (2,593 patients; age 69.89 years [95% CI 68.07-71.70]; 35.95% [29.43-42.46] males) were included in the meta-analysis. The prevalence of hypovitaminosis D (vitamin D deficiency or insufficiency) was 33.18% [25.10-41.26], but the combined prevalence of deficiency and insufficiency was 46.99 [34.02-59.96]. Hospital stay was 1.09 days [-0.39 to 2.56] longer in the hypovitaminosis D group compared to the euvitaminosis D group. Preoperatively, Harris Hip Score (HHS) and Knee Society Score were significantly lower (p = 0.001 and p = 0.00001, respectively) in the hypovitaminosis D group than in the euvitaminosis D group. Postoperatively, HHS (p = 0.004) score was significantly lower in the hypovitaminosis D group than in the euvitaminosis D group.

CONCLUSION

The prevalence of hypovitaminosis D is high in osteoarthritis patients undergoing knee or hip surgery. Vitamin D deficiency may affect the outcomes of orthopedic joint surgery. However, randomized trial/s will be required to confirm these findings.

[Percutaneous vertebroplasty and open vertebroplasty for metastatic spinal tumor]

OBJECTIVE

To explore the clinical application and therapeutic effect of percutaneous vertebroplasty(PVP) and open vertebroplasty for metastatic spinal tumor.

METHODS

The clinical data of 126 patients with metastatic spinal tumor underwent surgery and obtained follow-up from January 2012 to March 2016 were retrospectively analyzed. These 126 cases were divided into two groups according to different operative methods. The metastatic tumor of 43 cases encroached vertebral canal oppressing spinal cord and nerve root, they were treated with open operation(open vertebroplasty group);and other 83 cases without obviously spinal cord or nerve root compression, or unfit for open operation, were treated with PVP (percutaneous vertebroplasty group) . VAS score, ECOG and Frankel grade were used to evaluate the pain and neurofunction in two groups.All out-hospital patients were followed up every 3 months for 1 time. X-ray, CT, MRI were examined in follow-up.

RESULTS

A total of 112 vertebrae underwent PVP with the median surgical time of 50 min;VAS scores decreased significantly at 2 days after operation, which maintained till 1 month later; ECOG grade at 1 month decreased significantly;44 of 112 vertebrae suffered from asymptomatic bone cement leakage, no complications such as nerve injury or pulmonary embolism was found; the median survival time was 16 months. While for open vertebroplasty group, the median surgical time was 160 min and blood loss was 1 000 ml; postoperative VAS scores and ECOG grade at 1 month decreased significantly. Postoperative Frankel grade of 36 patients got improvement in 41 patients with spinal cord functional disturbance(87.8%); and 29 of 40 patients with incompleteness out of motor function were full recovery(76.3%); 12 cases (27.9%) occurred complications and the median survival time was 11 months.

CONCLUSIONS

The different vertebroplasty treatments can be selected for patients with metastatic spinal tumor, which can relieve the pain, improve the nerve function, reconstruct the spinal stabilization, maintain the local control and raise the life quality.

[Advances in the research of application of urine output monitoring in prevention and treatment of burn shock]

Fluid therapy is a crucial treatment for patients with extensive burn, which affects patients'prognosis directly. Accurate urine output measurement plays an irreplaceable role in guiding fluid resuscitation in clinic. As one of the best indexes in traditional burn resuscitation, urine output comprehensively reflects systemic circulation. However, it doesn't fully reflect all the specific chapters of microcirculation and systemic circulation and deficient cellular oxygen metabolism exactly. We need to use urine output combined with other shock parameters to ensure adequate fluid replacement. Currently, the most common way of urine output monitoring is manual measurement. The article reviews the application of urine output monitoring in guiding fluid resuscitation of burn shock.