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1.
Synthesis of atom‐precise alloy nanoclusters with uniform composition is challenging when the alloying atoms are similar in size (for example, Ag and Au). A galvanic exchange strategy has been devised to produce a compositionally uniform [Ag24Au(SR)18]? cluster (SR: thiolate) using a pure [Ag25(SR)18]? cluster as a template. Conversely, the direct synthesis of Ag24Au cluster leads to a mixture of [Ag25?xAux(SR)18]?, x=1–8. Mass spectrometry and crystallography of [Ag24Au(SR)18]? reveal the presence of the Au heteroatom at the Ag25 center, forming Ag24Au. The successful exchange of the central Ag of Ag25 with Au causes perturbations in the Ag25 crystal structure, which are reflected in the absorption, luminescence, and ambient stability of the particle. These properties are compared with those of Ag25 and Ag24Pd clusters with same ligand and structural framework, providing new insights into the modulation of cluster properties with dopants at the single‐atom level.  相似文献   

2.
Precise atomic structure of metal nanoclusters (NCs) is fundamental for elucidating the structure–property relationships and the inherent size‐evolution principles. Reported here is the largest known FCC‐based (FCC=face centered cubic) silver nanocluster, [Ag100(SC6H33,4F2)48(PPh3)8]?: the first all‐octahedral symmetric nesting Ag nanocluster with a four‐layered Ag6@Ag38@Ag48S24@Ag8S24P8 structure, consistent symmetry elements, and a unique rhombicuboctahedral morphology distinct from theoretical predictions and previously reported FCC‐based Ag clusters. DFT studies revealed extensive interlayer interactions and degenerate frontier orbitals. The FCC‐based Russian nesting doll model constitutes a new platform for the study of the size‐evolution principles of Ag NCs.  相似文献   

3.
Decreasing the core size is one of the best ways to study the evolution from AuI complexes into Au nanoclusters. Toward this goal, we successfully synthesized the [Au18(SC6H11)14] nanocluster using the [Au18(SG)14] (SG=L ‐glutathione) nanocluster as the starting material to react with cyclohexylthiol, and determined the X‐ray structure of the cyclohexylthiol‐protected [Au18(C6H11S)14] nanocluster. The [Au18(SR)14] cluster has a Au9 bi‐octahedral kernel (or inner core). This Au9 inner core is built by two octahedral Au6 cores sharing one triangular face. One transitional gold atom is found in the Au9 core, which can also be considered as part of the Au4(SR)5 staple motif. These findings offer new insight in terms of understanding the evolution from [AuI(SR)] complexes into Au nanoclusters.  相似文献   

4.
The first atomically and structurally precise silver‐nanoclusters stabilized by Se‐donor ligands, [Ag20{Se2P(OiPr)2}12] ( 3 ) and [Ag21{Se2P(OEt)2}12]+( 4 ), were isolated by ligand replacement reaction of [Ag20{S2P(Oi Pr)2}12] ( 1 ) and [Ag21{S2P(Oi Pr)2}12]+ ( 2 ), respectively. Furthermore, doping reactions of 4 with Au(PPh3)Cl resulted in the formation of [AuAg20{Se2P(OEt)2}12]+ ( 5 ). Structures of 3 , 4 , and 5 were determined by single‐crystal X‐ray diffraction. The anatomy of cluster 3 with an Ag20 core having C 3 symmetry is very similar to that of its dithiophosphate analogue 1 . Clusters 4 and 5 exhibit an Ag21 and Au@Ag20 core of Oh symmetry composed of eight silver capping atoms in a cubic arrangement and encapsulating an Ag13 and Au@Ag12 centered icosahedron, respectively. Both ligand exchange and heteroatom doping result in significant changes in optical and emissive properties for chalcogen‐passivated silver nanoparticles, which have been theoretically confirmed as 8‐electron superatoms.  相似文献   

5.
Precise atomic structure of metal nanoclusters (NCs) is fundamental for elucidating the structure–property relationships and the inherent size-evolution principles. Reported here is the largest known FCC-based (FCC=face centered cubic) silver nanocluster, [Ag100(SC6H33,4F2)48(PPh3)8]: the first all-octahedral symmetric nesting Ag nanocluster with a four-layered Ag6@Ag38@Ag48S24@Ag8S24P8 structure, consistent symmetry elements, and a unique rhombicuboctahedral morphology distinct from theoretical predictions and previously reported FCC-based Ag clusters. DFT studies revealed extensive interlayer interactions and degenerate frontier orbitals. The FCC-based Russian nesting doll model constitutes a new platform for the study of the size-evolution principles of Ag NCs.  相似文献   

6.
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.  相似文献   

7.
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 Ih 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].  相似文献   

8.
Gas‐phase photoelectron spectroscopy (PES) was conducted on [XAg24(SPhMe2)18]? (X=Ag, Au) and [YAg24(SPhMe2)18]2? (Y=Pd, Pt), which have a formal superatomic core (X@Ag12)5+ or (Y@Ag12)4+ with icosahedral symmetry. PES results show that superatomic orbitals in the (Au@Ag12)5+ core remain unshifted with respect to those in the (Ag@Ag12)5+ core, whereas the orbitals in the (Y@Ag12)4+ (Y = Pd, Pt) core shift up in energy by about 1.4 eV. The remarkable doping effect of a single Y atom (Y=Pd, Pt) on the electronic structure of the chemically modified (Ag@Ag12)5+ superatom was reproduced by theoretical calculations on simplified model systems and was ascribed to 1) the weaker binding of valence electrons in Y@(Ag+)12 compared to Ag+@(Ag+)12 due to the reduction in formal charge of the core potential, and 2) the upward shift of the apparent vacuum level due to the presence of a repulsive Coulomb barrier between [YAg24(SPhMe2)18]? and electron.  相似文献   

9.
The synthesis of Naumann's AgI/AgIII mixed valence salt [AgI]+[AgIII(CF3)4] ( Ag-1 ) is revisited. Ag-1 is now safely available in half gram scale upon 2e oxidation of AgF in presence of CF3SiMe3 and ambient air. In addition to its unprecedented crystallographic characterization, the use of Ag-1 to build the novel AgI/AgIII salts [ Ag (bpy)2] -1 , [ Ag (18-crown-6)2] -1 , [ Ag -crypt-222] -1 and [ Ag (PCy3)2] -1 is herein reported, alongside their characterization by NMR, single crystal X-ray diffraction (Sc-XRD) and elemental analysis (EA). The utility of the currently affordable Ag-1 in gold(I) catalysis was demonstrated by the excellent catalytic activity displayed by [{ Au (PPh3)}2(μ-Cl)] -1 and [ Au (PPh3)] -1 in the 5-exo-dig cyclization of N-propargylbenzamide ( 2 ). These cationic AuI catalysts are accessible from (PPh3)AuCl and Ag-1 , and outperform the activity of the well-known benchmark catalyst (PPh3)AuNTf2.  相似文献   

10.
The [AuxAg16-x(SAdm)8(Dppe)2] nanocluster with aggregation-induced emission (AIE) was synthesized from a non-fluorescent [Au9Ag12(SAdm)4(Dppm)6Cl6](SbF6)3 nanocluster via a ligand-exchange engineering (Dppe=1,2-Bis(diphenylphosphino)ethane, Dppm=Bis(diphenylphosphino)methane, HSAdm=1-Adamantanethiol). The nanocluster has a Au-doped icosahedral AuxAg13-x core, capped by two Ag(SR)3, one Ag(SR)2 and two Dppe ligands. By changing the achiral Dppe ligand into a chiral dbpb ligand ((2S,3S)-(-)-Bis(diphenylphosphino)butane or (2R,3R)-(+)-2,3-Bis(diphenylphosphino)butane), chiral nanoclusters are obtained. ESI-MS and UV-vis spectroscopy were performed to track the reaction. This work provides guidance for the construction of new clusters by etching clusters with multidentate phosphine ligands.  相似文献   

11.
The synthesis and structure of atomically precise Au130?xAgx (average x=98) alloy nanoclusters protected by 55 ligands of 4‐tert‐butylbenzenethiolate are reported. This large alloy structure has a decahedral M54 (M=Au/Ag) core. The Au atoms are localized in the truncated Marks decahedron. In the core, a drum of Ag‐rich sites is found, which is enclosed by a Marks decahedral cage of Au‐rich sites. The surface is exclusively Ag?SR; X‐ray absorption fine structure analysis supports the absence of Au?S bonds. The optical absorption spectrum shows a strong peak at 523 nm, seemingly a plasmon peak, but fs spectroscopic analysis indicates its non‐plasmon nature. The non‐metallicity of the Au130?xAgx nanocluster has set up a benchmark to study the transition to metallic state in the size evolution of bimetallic nanoclusters. The localized Au/Ag binary architecture in such a large alloy nanocluster provides atomic‐level insights into the Au?Ag bonds in bimetallic nanoclusters.  相似文献   

12.
The X-ray structural study of the reaction product of equimolar amounts of [Au3Cu2(C2Ph)6]. [{Au(C2Ph)} n ], and [Ag(C2Ph)} n ] revealed two bimetallic anionic [N(PPh3)2] + [Au3Ag2(C2Ph)6] and [N(PPh3)2]+[Au3Cu2 (C2 Pg)6] — clusters co-crystallized in one asymmetric unit. Each cluster has trigonal bipyramidal geometry with three gold atoms occupying equatorial planes and two silver or copper atoms in the apical positions. Our earlier conclusion based upon spectroscopic characterization describing the product of be above reaction as trimetallic cluster containing three coinage-metals with an overall composition [Au3CuAg(C2Ph)6], was erroneous.Presented at the 210th ACS Meeting, August 19–24, 1995, Chicago, Illinois.  相似文献   

13.
The change in the valence state of nanocluster can induce remarkable changes in the properties and structure. However, achieving the valence state changes in nanoclusters is still a challenge. In this work, we use Cu2+ as dopant to “oxidize” [Ag62S12(SBut)32]2+ (4 free electrons) to obtain the new nanocluster: [Ag62−xCuxS12(SBut)32]4+ with 2 free electrons. As revealed by its structure, the [Ag62−xCuxS12(SBut)32]4+ (x=10∼21) has a similar structure to that of [Ag62S12(SBut)32]2+ precursor and all the Cu atoms occupy the surface site of nanocluster. It′s worth noting that with the Cu atoms doping, the [Ag62−xCuxS12(SBut)32]4+ nanocluster is more stable than [Ag62S12(SBut)32]2+ at higher temperature and in electrochemical cycle. This result has laid a foundation for the subsequent application and exploration. Overall, this work reveals crystals structure of a new Ag−Cu nanocluster and offers a new insight into the electron reduction/oxidation of nanocluster.  相似文献   

14.
Small Agn nanoclusters (n<10) have been emerging as promising materials as sensing, biolabeling, and catalysis because of their unique electronic states and optical properties. However, studying synthesis, structure determination, and exploration of their properties remain major challenges as a result of the low stability of small Ag nanoclusters. Herein, we synthesized an atomically precise face‐centered‐cubic‐type small {Ag7}5+ nanocluster supported by a novel triangular hollow polyoxometalate (POM) framework [Si3W27O96]18?. The cluster showed unique {Ag7}5+‐to‐POM charge transfer bands in both visible and UV light regions. Furthermore, this small {Ag7}5+ nanocluster exhibited an unprecedented ultrastability in solution, despite having exposed Ag sites that can be accessed by small molecules, such as O2, water, and solvents.  相似文献   

15.
The conventional synthetic methodology for atomically precise gold nanoclusters by using reduction in solution offers only the thermodynamically most stable nanoclusters. Herein, a solubility-driven isolation strategy is reported to access a metastable gold cluster. The cluster, with the composition of [Au9(PPh3)8]+ ( 1 ), displays an unusual, nearly perfect body-centered cubic (bcc) structure. As revealed by ESI-MS and UV/Vis measurements, the cluster is metastable in solution and converts to the well-known [Au11(PPh3)8Cl2]+ ( 2 ) within just 90 min. DFT calculations revealed that although both 1 and 2 are eight-electron superatoms, there is a driving force to convert 1 to 2 as shown by the increased cohesion and larger HOMO–LUMO energy gap of 2 . The isolation and crystallization of the metastable gold cluster were achieved in a biphasic reaction system in which reduction of gold precursors and crystallization of 1 took place concurrently. This synthetic protocol represents a successful strategy for investigations of other metastable species in metal nanocluster chemistry.  相似文献   

16.
The betain‐like carbodiphosphorane CS2 adduct S2CC(PPh3)2 ( 1 ) reacts with Ag(I) salts which contain weakly coordinating anions such as [BF4]? or [Al{OC(CF3)3}4]? to produce the cluster compounds [Ag6{S2CC(PPh3)2}4][BF4]6 ( 2 ) and [Ag4{S2CC(PPh3)2}4][Al{OC(CF3)3}4]4 ( 3 ), respectively, as orange yellow crystals containing solvent molecules. In the solid state the Ag4 unit in 3 forms a tetrahedron, and in the Ag6 core of 2 two of the opposite edges of the tetrahedron are bridged by Ag+ ions. The clusters are held together by argentophilic interactions, and each sulfur atom of 1 is coordinated to four (as in 2 ) or three (as in 3 ) silver atoms. The compounds are characterized by IR and 31P NMR spectroscopic studies and by X‐ray diffraction analyses.  相似文献   

17.
Two heteroctanuclear Au4Ag4 cluster complexes of 4,5-diethynylacridin-9-one (H2L) were prepared through the self-assembly reactions of [Au(tht)2](CF3SO3), Ag(tht)(CF3SO3), H2L and PPh3 or PPh2Py (2-(diphenylphosphino)pyridine). The Au4Ag4 cluster consists of a [Au4L4]4− and four [Ag(PPh3)]+ or [Ag(PPh2Py)]+ units with Au4L4 framework exhibiting a twisted paper clip structure. In CH2Cl2 solutions at ambient temperature, both compounds show ligand fluorescence at ca. 463 nm as well as phosphorescence at 650 nm for 1 and 630 nm for 2 resulting from admixture of 3IL (intraligand) of L ligand, 3LMCT (from L ligand to Au4Ag4) and 3MC (metal-cluster) triplet states. Crystals or crystalline powders manifest bright yellow-green phosphorescence with vibronic-structured emission bands at 530 (568sh) nm for complex 1 and 536 (576sh) nm for complex 2. Upon mechanical grinding, yellow-green emission in the crystalline state is dramatically converted to red luminescence centered at ca. 610 nm with a drastic redshift of the emission after crystal packing is destroyed.  相似文献   

18.
In a new oxidative route, Ag+[Al(ORF)4]? (RF=C(CF3)3) and metallic indium were sonicated in aromatic solvents, such as fluorobenzene (PhF), to give a precipitate of silver metal and highly soluble [In(PhF)n]+ salts (n=2, 3) with the weakly coordinating [Al(ORF)4]? anion in quantitative yield. The In+ salt and the known analogous Ga+[Al(ORF)4]? were used to synthesize a series of homoleptic PR3 phosphane complexes [M(PR3)n]+, that is, the weakly PPh3‐bridged [(Ph3P)3In–(PPh3)–In(PPh3)3]2+ that essentially contains two independent [In(PPh3)3]+ cations or, with increasing bulk of the phosphane, the carbene‐analogous [M(PtBu3)2]+ (M=Ga, In) cations. The MI? P distances are 27 to 29 pm longer for indium, and thus considerably longer than the difference between their tabulated radii (18 pm). The structure, formation, and frontier orbitals of these complexes were investigated by calculations at the BP86/SV(P), B3LYP/def2‐TZVPP, MP2/def2‐TZVPP, and SCS‐MP2/def2‐TZVPP levels.  相似文献   

19.
Herein, we report the synthesis and atomic structure of the cluster‐assembled [Au60Se2(Ph3P)10(SeR)15]+ material. Five icosahedral Au13 building blocks from a closed gold ring with Au–Se–Au linkages. Interestingly, two Se atoms (without the phenyl tail) locate in the center of the cluster, stabilized by the Se‐(Au)5 interactions. The ring‐like nanocluster is unprecedented in previous experimental and theoretical studies of gold nanocluster structures. In addition, our optical and electrochemical studies show that the electronic properties of the icosahedral Au13 units still remain unchanged in the penta‐twinned Au60 nanocluster, and this new material might be a promising in optical limiting material. This work offers a basis for deep understanding on controlling the cluster‐assembled materials for tailoring their functionalities.  相似文献   

20.
H2Ru33-S)(CO)9 is deprotonated by K[HBBus3] to give cluster anions which react with [O{Au(PPh3)}3]+ or with AuCl(PPh3)/T1+ to give HRu3Au(μ3-S)(CO)9(PPh3) (1) and Ru3Au23-S)(CO)9(PPh3)2 (3). A similar sequence with HRu33-SBut)(CO)9 leads to Ru3Au(μ3-SBut)(CO)9(PPh3) (2) as the main product although some 1 also forms, indicating SC cleavage competes with deprotonation of HRu33-SBut)(CO)9 by [HBBus3]?. The X-ray crystal structures of 1, 2 and 3 are described; (1) and (2) have “butterfly” AuRu3 cores with markedly different hinge angles of 119 and 148° respectively, while 3 has a trigonal-bipyramidal Au2Ru3 skeleton. All three clusters have the sulphur atom symmetrically bridging the Ru3 triangular face.  相似文献   

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