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A multi-component mixed acid was prepared by simulating the composition of exhaust gas recirculation condensate, and the effects of the multi-component mixed acid solution on the mechanical properties, apparent morphology and thermal stability of silicone rubber, fluororubber and ethylene-acrylate rubber were investigated. The results showed that after corrosion, the mechanical properties and surface morphology of fluororubber and ethylene-acrylate rubber remained good, while cracks appeared on the surface of silicone rubber and its tensile strength and elongation at break decreased significantly by 86.6% and 90.3%, respectively. Thermal stability of fluororubber remained good, while the initial decomposition temperature of ethylene-acrylate rubber and silicone rubber increased.

A 'passivated precursor' approach is developed for the efficient synthesis and isolation of all‐alkynyl‐protected gold nanoclusters. Direct reduction of dpa‐passivated precursor Au‐dpa (Hdpa=2,2'‐dipyridylamine) in one‐pot under ambient conditions gives a series of clusters including Au22(C≡CR)18 (R=−C6H4−2−F), Au36(C≡CR)24, Au44(C≡CR)28, Au130(C≡CR)50, and Au144(C≡CR)60. These clusters can be well separated via column chromatography. The overall isolation yield of this series of clusters is 40 % (based on gold), which is much improved in comparison with previous approaches. It is notable that the molecular structure of the giant cluster Au130(C≡CR)50 is revealed, which presents important information for understanding the structure of the mysterious Au130 nanoclusters. Theoretical calculations indicated Au130(C≡CR)50 has a smaller HOMO‐LUMO gap than Au130(S−C6H4−4−CH3)50. This facile and reliable synthetic approach will greatly accelerate further studies on all‐alkynyl‐protected gold nanoclusters. [ABSTRACT FROM AUTHOR]

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‐(C3N6H3)3−]2−AuI6AgI6. X‐ray single crystal structural analysis showed that a crown‐like AuI6AgI6 macrocycle is aligned around two parallelly stacked μ6‐(C3N6H3)3− moieties hold together with π–π interactions. Theoretical calculations revealed that the [μ6‐(C3N6H3)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. [ABSTRACT FROM AUTHOR]

A facile strategy that directly reduces alkynyl‐silver precursors and copper salts for the synthesis of bimetallic nanoclusters using the weak reducing agent Ph2SiH2 is demonstrated. Two alkynyl‐protected concentric‐shell nanoclusters, (Ph4P)2[Ag22Cu12(C≡CR)28] and (Ph4P)3[Ag42Cu12Cl(C≡CR)36] (Ag22Cu12 and Ag42Cu12Cl, 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 Ag42Cu12Cl, which is icosahedral M54Cl 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. [ABSTRACT FROM AUTHOR]

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 unit wrapped by six Ino decahedra through edge‐sharing. This is the first time that Ino decahedra are used as a building block 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 understanding metal cluster assembling mechanisms. [ABSTRACT FROM AUTHOR]

A Au55 nanocluster with the composition of [Au55(p‐MBT)24(Ph3P)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(Ph3P)12Cl6. The Au55 cluster shows a wide optical absorption band with optical energy gap (Eg=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)10Cl2]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). [ABSTRACT FROM AUTHOR]

A 'passivated precursor' approach is developed for the efficient synthesis and isolation of all‐alkynyl‐protected gold nanoclusters. Direct reduction of dpa‐passivated precursor Au‐dpa (Hdpa=2,2'‐dipyridylamine) in one‐pot under ambient conditions gives a series of clusters including Au22(C≡CR)18 (R=−C6H4−2−F), Au36(C≡CR)24, Au44(C≡CR)28, Au130(C≡CR)50, and Au144(C≡CR)60. These clusters can be well separated via column chromatography. The overall isolation yield of this series of clusters is 40 % (based on gold), which is much improved in comparison with previous approaches. It is notable that the molecular structure of the giant cluster Au130(C≡CR)50 is revealed, which presents important information for understanding the structure of the mysterious Au130 nanoclusters. Theoretical calculations indicated Au130(C≡CR)50 has a smaller HOMO‐LUMO gap than Au130(S−C6H4−4−CH3)50. This facile and reliable synthetic approach will greatly accelerate further studies on all‐alkynyl‐protected gold nanoclusters. [ABSTRACT FROM AUTHOR]

Due to the stability issue, It is difficult to prepare a silver nanocluster bearing functional sites, especially at a large scale. We report the synthesis and structure of a stable silver nanocluster bearing multiple surface aldehyde groups [Ag21(Ph2PO2)10(p‐CHOPhC≡C)6]SbF6, which allows for postsynthesis modification such as surface functionalization through aldimine condensation to give homochiral clusters. Remarkably, the preparation of this cluster can be done in ~90 % high yield at gram scale, which facilitates further studies and potential applications. Through DFT calculations and geometric structure analysis, the high stability of this cluster is attributed to the geometric closure and electronic structure. This is the first time that an effective one‐pot method has been developed to synthesize functional silver nanoclusters in high yield. The title cluster will be useful in the development of a variety of cluster‐based materials. [ABSTRACT FROM AUTHOR]

It is challenging to attain strong near-infrared (NIR) emissive gold nanoclusters. Here we show a rod-shaped cluster with the composition of [Au 28 (p-MBT) 14 (Hdppa) 3 ](SO 3 CF 3 ) 2 (1 for short, Hdppa is N,N-bis(diphenylphosphino)amine, p-MBT is 4-methylbenzenethiolate) has been synthesized. Single crystal X-ray structural analysis reveals that it has a rod-like face-centered cubic (fcc) Au 22 kernel built from two interpenetrating bicapped cuboctahedral Au 15 units. 1 features NIR luminescence with an emission maximum at 920 nm, and the photoluminescence quantum yield (PLQY) is 12%, which is 30-fold of [Au 21 (m-MBT) 12 (Hdppa) 2 ]SO 3 CF 3 (2, m-MBT is 3-methylbenzenethiolate) with a similar composition and 60-fold of Au 30 S(S‑t‑Bu) 18 with a similar structure. time-dependent DFT(TDDFT)calculations reveal that the luminescence of 1 is associated with the Au 22 kernel. The small Stokes shift of 1 indicates that it has a very small excited state structural distortion, leading to high radiative decay rate (k r ) probability. The emission of cluster 1 is a mixture of phosphorescence and thermally activated delayed fluorescence(TADF), and the enhancement of the NIR emission is mainly due to the promotion of k r rather than the inhibition of k nr . This work demonstrates that the metal kernel and the surface structure are both very important for cluster-based NIR luminescence materials., (© 2024. The Author(s).)

A 'passivated precursor' approach is developed for the efficient synthesis and isolation of all-alkynyl-protected gold nanoclusters. Direct reduction of dpa-passivated precursor Au-dpa (Hdpa=2,2'-dipyridylamine) in one-pot under ambient conditions gives a series of clusters including Au 22 (C≡CR) 18 (R=-C 6 H 4 -2-F), Au 36 (C≡CR) 24 , Au 44 (C≡CR) 28 , Au 130 (C≡CR) 50 , and Au 144 (C≡CR) 60 . These clusters can be well separated via column chromatography. The overall isolation yield of this series of clusters is 40 % (based on gold), which is much improved in comparison with previous approaches. It is notable that the molecular structure of the giant cluster Au 130 (C≡CR) 50 is revealed, which presents important information for understanding the structure of the mysterious Au 130 nanoclusters. Theoretical calculations indicated Au 130 (C≡CR) 50 has a smaller HOMO-LUMO gap than Au 130 (S-C 6 H 4 -4-CH 3 ) 50 . This facile and reliable synthetic approach will greatly accelerate further studies on all-alkynyl-protected gold nanoclusters., (© 2024 Wiley-VCH GmbH.)

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 [μ 6 -(C 3 N 6 H 3 ) 3- ] 2 -Au I 6 Ag I 6 . X-ray single crystal structural analysis showed that a crown-like Au I 6 Ag I 6 macrocycle is aligned around two parallelly stacked μ 6 -(C 3 N 6 H 3 ) 3- moieties hold together with π-π interactions. Theoretical calculations revealed that the [μ 6 -(C 3 N 6 H 3 ) 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., (© 2023 Wiley-VCH GmbH.)

A facile strategy that directly reduces alkynyl-silver precursors and copper salts for the synthesis of bimetallic nanoclusters using the weak reducing agent Ph 2 SiH 2 is demonstrated. Two alkynyl-protected concentric-shell nanoclusters, (Ph 4 P) 2 [Ag 22 Cu 12 (C≡CR) 28 ] and (Ph 4 P) 3 [Ag 42 Cu 12 Cl(C≡CR) 36 ] (Ag 22 Cu 12 and Ag 42 Cu 12 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 Ag 42 Cu 12 Cl, which is icosahedral M 54 Cl instead of M 55 . 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., (© 2023 Wiley-VCH GmbH.)

The reduction of alkynyl-silver and phosphine-silver precursors with a weak reducing reagent Ph 2 SiH 2 led to the formation of a novel silver nanocluster [Ag 93 (PPh 3 ) 6 (C≡CR) 50 ] 3+ (R=4-CH 3 OC 6 H 4 ), which is the largest structurally characterized cluster of clusters. This disc-shaped cluster has a Ag 69 kernel consisting of a bicapped hexagonal prismatic Ag 15 unit wrapped by six Ino decahedra through edge-sharing. This is the first time that Ino decahedra are used as a building block 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 understanding metal cluster assembling mechanisms., (© 2023 Wiley-VCH GmbH.)

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., (© 2022 Wiley-VCH GmbH.)

Anions have been used to regulate the structures and luminescence of heterometallic clusters. Introducing ClO 4 - into orange-emissive, butterfly-like [(C)(Au-PPhpy 2 ) 6 Ag 4 ](BF 4 ) 6 (1, PPhpy 2 =bis(2-pyridyl)phenylphosphine) leads to the formation of red-emissive [(C)(Au-PPhpy 2 ) 6 Ag 5 (ClO 4 ) 3 ](ClO 4 ) 4 (2) with a novel trigonal bipyramidal structure; employing PhCO 2 - gives yellow-emissive, hexagram-like [(C)(Au-PPhpy 2 ) 6 Ag 6 (PhCO 2 ) 3 ](BF 4 ) 5 (3). Notably, 1 exhibits weak luminescence in CH 2 Cl 2 /CH 3 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., (© 2022 Wiley-VCH GmbH.)

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., (© 2022 Wiley-VCH GmbH.)

For the first time site-specific doping of silver into a spherical Au 25 nanocluster has been achieved in [Au 19 Ag 6 (MeOPhS) 17 (PPh 3 ) 6 ] (BF 4 ) 2 (Au 19 Ag 6 ) through a dual-ligand coordination strategy. Single crystal X-ray structural analysis shows that the cluster has a distorted centered icosahedral Au@Au 6 Ag 6 core of D 3 symmetry, in contrast to the I h Au@Au 12 kernel in the well-known [Au 25 (SR) 18 ] - (R = CH 2 CH 2 Ph). An interesting feature is the coexistence of [Au 2 (SPhOMe) 3 ] dimeric staples and [P-Au-SPhOMe] semi-staples in the title cluster, due to the incorporation of PPh 3 . The observation of only one double-charged peak in ESI-TOF-MS confirms the ordered doping of silver atoms. Au 19 Ag 6 is a 6e system showing a distinct absorption spectrum from [Au 25 (SR) 18 ] - , that is, the HOMO-LUMO transition of Au 19 Ag 6 is optically forbidden due to the P character of the superatomic frontier orbitals., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

An atomically resolved gold nanocluster Au 99 (C≡CC 6 H 3 -2,4-F 2 ) 40 ( Au 99 ) with an unusual 59 valence electrons has been synthesized. Single-crystal X-ray diffraction reveals that its Au 79 kernel is a Au 49 Marks decahedron capped by two Au 15 units. The surface structure of Au 99 consists of 20 linear Au(C≡CR) 2 staples. Intercluster interactions are observed between these D 5 symmetric clusters. The existence of an unpaired electron is verified by magnetic measurement. Interestingly, this open-shell gold cluster Au 99 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.

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 (Ph 4 P) 6 [Au 156 (C≡CR) 60 ] (R = 4-CF 3 C 6 H 4 -) ( Au 156 ) are reported. It presents an ideal platform for studying the relationship between the structure and the metallic nature. Au 156 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 Au 126 core structure (Au 46 @Au 50 @Au 30 ) protected by 30 linear RC≡C-Au-C≡CR staple motifs. It is interesting that Au 156 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 Au 156 is a critical crossover cluster for the transition from molecular to metallic state. Au 156 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.

A Au 55 nanocluster with the composition of [Au 55 (p-MBT) 24 (Ph 3 P) 6 ](SbF 6 ) 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 Au 55 nanocluster features a face-centered cubic (fcc) Au 55 kernel, different from the well-known two-shell cuboctahedral arrangement in Au 55 (Ph 3 P) 12 Cl 6 . The Au 55 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 [Au 25 (SR) 5 (PPh 3 ) 10 Cl 2 ] 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 Au 55 nanocluster exhibits high catalytic activity and selectivity for electrochemical reduction of CO 2 to CO; the Faradaic efficiency (FE) reaches 94.1 % at -0.6 V vs. reversible hydrogen electrode (RHE)., (© 2021 Wiley-VCH GmbH.)