Extra Silver Atom Triggers Room‐Temperature Photoluminescence in Atomically Precise Radarlike Silver Clusters

Luminescent metal clusters show promise for applications in imaging and sensing. However, promoting emission from metal clusters at room temperature is a challenging task owing to the lack of an efficient approach to suppress the nonradiative decay process in metal cores. We report herein that the addition of a silver atom into a metal interstice of the radarlike thiolated silver cluster [Ag₂₇(S^tBu)₁₄(S)₂(CF₃COO)₉(DMAc)₄]?DMAc ( NC1 , DMAc=dimethylacetamide), which is non‐emissive under ambient conditions, produced another silver cluster [Ag₂₈(AdmS)₁₄(S)₂(CF₃COO)₁₀(H₂O)₄] ( NC2 ) that displayed bright green room‐temperature photoluminescence aided by the new ligand 1‐adamantanethiol (AdmSH). The 28th Ag atom, which hardly affects the geometrical and electronic structures of the Ag–S skeleton, triggered the emission of green light as a result of the rigidity of the cluster structure.     

Extra Silver Atom Triggers Room-Temperature Photoluminescence in Atomically Precise Radarlike Silver Clusters

Luminescent metal clusters show promise for applications in imaging and sensing. However, promoting emission from metal clusters at room temperature is a challenging task owing to the lack of an efficient approach to suppress the nonradiative decay process in metal cores. We report herein that the addition of a silver atom into a metal interstice of the radarlike thiolated silver cluster [Ag₂₇(S^tBu)₁₄(S)₂(CF₃COO)₉(DMAc)₄]⋅DMAc ( NC1 , DMAc=dimethylacetamide), which is non-emissive under ambient conditions, produced another silver cluster [Ag₂₈(AdmS)₁₄(S)₂(CF₃COO)₁₀(H₂O)₄] ( NC2 ) that displayed bright green room-temperature photoluminescence aided by the new ligand 1-adamantanethiol (AdmSH). The 28th Ag atom, which hardly affects the geometrical and electronic structures of the Ag–S skeleton, triggered the emission of green light as a result of the rigidity of the cluster structure.     

Pyridine dicarbanion-bonded Ag13 organometallic nanoclusters: synthesis and on-surface oxidative coupling reaction

Highly reactive organometallic nanoclusters in situ generated in metal-catalyzed reactions are pivotal in the comprehension of catalytic mechanisms. Herein, we develop a two-step synthetic method to achieve three unprecedented aryl dicarbanion-bonded Ag₁₃ nanoclusters by using protective macrocyclic ligands. Firstly, various aryl dicarbanion–Ag₄ cluster intermediates are acquired via a silver-mediated annulation reaction within a macrocyclic ligand. These Ag₄ cluster precursors are released from the surrounding macrocycle by protonation, and further undergo an inter-cluster coupling to generate bipyridine products and low-valence silver atoms. The remaining resurgent diide–Ag₄ clusters assemble with low-valence silver atoms to yield a series of organometallic Ag₁₃ nanoclusters. These Ag₁₃ nanoclusters feature a unique open-shell electronic structure as well as a chiral cluster architecture due to the asymmetric arrangements of surrounding aryl dianion ligands. Furthermore, the pyridyl diide ligands on the surface of the nanocluster further experience an intra-cluster oxidative coupling to produce bipyridine coupling products and large nanoparticles. The coupling reaction-driven cluster-to-cluster transformation is comprehensively tracked by high resolution mass spectroscopy. This work is not only reminiscent of the detailed evolution of cluster species upon the occurrence of coupling reactions, but also reproduces novel inter- and intra-cluster coupling steps at different reaction stages.

Unprecedented pyridine dicarbanion-bonded Ag₁₃ nanoclusters were constructed according to a macrocycle-involved two-step synthetic protocol.     

Au57Ag53(C≡CPh)40Br12: A Large Nanocluster with C1 Symmetry

The controlled synthesis and structure determination of a bimetallic nanocluster Au₅₇Ag₅₃(C≡CPh)₄₀Br₁₂ (Au₅₇Ag₅₃) is presented. The metal core has a four‐shell Au₂M₃@Au₃₄@Ag₅₁ @Au₂₀ (M=1/3 Au+2/3 Ag) architecture. In contrast to the previously reported large nanoclusters that have highly symmetric kernel structures, the metal atoms in Au₅₇Ag₅₃ are arranged in an irregular manner with C₁ symmetry. This cluster exhibits excellent thermal stability and is robust under oxidative or basic conditions. The silver precursors play a key role in dictating the structures of the nanoclusters, which suggests the importance of the counteranions used.     

Crystal structure of a NIR‐Emitting DNA‐Stabilized Ag16 Nanocluster

DNA has been used as a scaffold to stabilize small, atomically monodisperse silver nanoclusters, which have attracted attention due to their intriguing photophysical properties. Herein, we describe the X‐ray crystal structure of a DNA‐encapsulated, near‐infrared emitting Ag₁₆ nanocluster (DNA–Ag₁₆NC). The asymmetric unit of the crystal contains two DNA–Ag₁₆NCs and the crystal packing between the DNA–Ag₁₆NCs is promoted by several interactions, such as two silver‐mediated base pairs between 3′‐terminal adenines, two phosphate–Ca²⁺–phosphate interactions, and π‐stacking between two neighboring thymines. Each Ag₁₆NC is confined by two DNA decamers that take on a horse‐shoe‐like conformation and is almost fully shielded from the solvent environment. This structural insight will aid in the determination of the structure/photophysical property relationship for this class of emitters and opens up new research opportunities in fluorescence imaging and sensing using noble‐metal clusters.     

Alternating Array Stacking of Ag26Au and Ag24Au Nanoclusters

An assembly strategy for metal nanoclusters using electrostatic interactions with weak interactions, such as C?H???π and π???π interactions in which cationic [Ag₂₆Au(2‐EBT)₁₈(PPh₃)₆]⁺ and anionic [Ag₂₄Au(2‐EBT)₁₈]^? nanoclusters gather and assemble in an unusual alternating array stacking structure is presented. [Ag₂₆Au(2‐EBT)₁₈(PPh₃)₆]⁺ [Ag₂₄Au(2‐EBT)₁₈]^? is a new compound type, a double nanocluster ion compound (DNIC). A single nanocluster ion compound (SNIC) [PPh₄]⁺ [Ag₂₄Au(2‐EBT)₁₈]^? was also synthesized, having a k‐vector‐differential crystallographic arrangement. [PPh₄]⁺ [Ag₂₄Au(2,4‐DMBT)₁₈]^? adopts a different assembly mode from both [Ag₂₆Au(2‐EBT)₁₈(PPh₃)₆]⁺ [Ag₂₄Au(2‐EBT)₁₈]^? and [PPh₄]⁺ [Ag₂₄Au(2‐EBT)₁₈]^?. Thus, the striking packing differences of [Ag₂₆Au(2‐EBT)₁₈(PPh₃)₆]⁺ [Ag₂₄Au(2‐EBT)₁₈]^?, [PPh₄]⁺ [Ag₂₄Au(2‐EBT)₁₈]^? and the existing [PPh₄]⁺ [Ag₂₄Au(2,4‐DMBT)₁₈]^? from each other indicate the notable influence of ligands and counterions on the self‐assembly of nanoclusters.     

Rhombicuboctahedral Ag100: Four-Layered Octahedral Silver Nanocluster Adopting the Russian Nesting Doll Model

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(SC₆H₃^3,4F₂)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.     

Münzmetallcluster mit verbrückenden Imido‐ und Amidoliganden: [{Li(dme)3}4][Cu18(NPh)11] und [Ag6(NHPh)4(PnPr3)6Cl2]

Copper and Silver Clusters with Bridging Imido and Amido Ligands From the reactions of copper and silver chloride with tertiary phosphines and lithiated aniline the compounds [{Li(dme)₃}₄][Cu₁₈(NPh)₁₁] ( 1 ) and [Ag₆(NHPh)₄(PⁿPr₃)₆Cl₂] ( 2 ) were obtained. The structure of the anion in 1 is closely related to the structures of the reported clusters [Cu₁₂(NPh)₈]^4– [1] and [Cu₂₄(NPh)₁₄]^4– [2]: 1 represents the third phenyl imido bridged copper cluster which contains parallel Cu₃‐ and Cu₆‐planes. The dimeric compound 2 consists of two Ag₃ units with bridging phenyl amido ligands. Two chloride and six phosphine ligands complete the ligand sphere and shield the metal core effectively.     

Rhombicuboctahedral Ag100: Four‐Layered Octahedral Silver Nanocluster Adopting the Russian Nesting Doll Model

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(SC₆H₃^3,4F₂)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.     

Formation of an Alkynyl-Protected Ag112 Silver Nanocluster as Promoted by Chloride Released In Situ from CH2Cl2

By directly reducing alkynyl–silver precursors, we successfully obtained a large alkynyl-protected silver nanocluster, (C₇H₁₇ClN)₃[Ag₁₁₂Cl₆(C≡CAr)₅₁], which is hitherto the largest structurally characterized silver nanocluster in the alkynyl family. The cluster exhibits four concentric core–shell structures (Ag₁₃@Ag₄₂@Ag₄₈@Ag₉), and four types of alkynyl–silver binding modes are observed. Chloride was found to be critical for the stabilization and formation of the silver nanocluster. The release of chloride ions in situ from CH₂Cl₂ solvent has been confirmed by mass spectrometry. This study suggests that the combination of alkynyl and halide ligands will pave a new way for the synthesis of large silver nanoclusters.     

Discrete Silver(I)‐Palladium(II)‐Oxo Nanoclusters, {Ag4Pd13} and {Ag5Pd15}, and the Role of Metal–Metal Bonding Induced by Cation Confinement

We introduce the class of discrete silver(I)‐palladium(II)‐oxo nanoclusters with the preparation of {Ag₄Pd₁₃} and {Ag₅Pd₁₅}. Both polyanions represent the first examples of noble metal‐capped polyoxo‐noble‐metalates in a fully inorganic assembly, featuring an unprecedented host–guest mode containing hetero‐ and homometallic Ag–Pd and Ag–Ag bonding interactions. Comprehensive theoretical calculations suggest that the Ag–Pd metallic bonds originate partially from surface confinement of Ag^I guest ions onto the anionic polyoxopalladate host that is induced by strong electrostatic forces. This work opens the field of fully inorganic silver‐palladium‐oxo nanoclusters, which can be considered as discrete mixed noble metal precursors for the formation of monodisperse core–shell nanoparticles, with high relevance for catalysis.     

Formation of an Alkynyl‐Protected Ag112 Silver Nanocluster as Promoted by Chloride Released In Situ from CH2Cl2

By directly reducing alkynyl–silver precursors, we successfully obtained a large alkynyl‐protected silver nanocluster, (C₇H₁₇ClN)₃[Ag₁₁₂Cl₆(C≡CAr)₅₁], which is hitherto the largest structurally characterized silver nanocluster in the alkynyl family. The cluster exhibits four concentric core–shell structures (Ag₁₃@Ag₄₂@Ag₄₈@Ag₉), and four types of alkynyl–silver binding modes are observed. Chloride was found to be critical for the stabilization and formation of the silver nanocluster. The release of chloride ions in situ from CH₂Cl₂ solvent has been confirmed by mass spectrometry. This study suggests that the combination of alkynyl and halide ligands will pave a new way for the synthesis of large silver nanoclusters.     

Fabrication of a family of atomically precise silver nanoclusters via dual-level kinetic control

The controllable preparation of metal nanoclusters in high yield is an essential prerequisite for their fundamental research and extensive application. Here a synthetic approach termed “dual-level kinetic control” was developed to fabricate a family of new silver nanoclusters. The introduction of secondary ligands was first exploited to retard the reduction rate and accomplish the first-level kinetic control. And the cooling of the reaction was performed to further slow the reduction down and accomplish the second-level kinetic control. A family of atomically precise silver nanoclusters (including [Ag₂₅(SR)₁₈]⁻, [Ag₃₄(SR)₁₈(DPPP)₃Cl₄]²⁺, [Ag₃₆(SR)₂₆S₄]²⁺, [Ag₃₇(SR)₂₅Cl₁]⁺, and [Ag₅₂(SR)₂₈Cl₄]²⁺) were controllably prepared and structurally determined. The developed “dual-level kinetic control” hopefully acts as a powerful synthetic tool to manufacture more nanoclusters with unprecedented compositions, structures, and properties.

A dual-level kinetic control was exploited to fabricate a family of atomically precise silver nanoclusters.     

Templated Atom‐Precise Galvanic Synthesis and Structure Elucidation of a [Ag24Au(SR)18]− Nanocluster

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 [Ag_25?xAu_x(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.     

T-symmetric 40-nucleus silver clusters assembled by hetero-anions

We report two anion-templated Ag₄₀ clusters, [Ag₄₀(E)₄(SO₄){S₂P(OEt)₂}₂₄](PF₆)₆ (E = S, 1 ; Se, 2 ). The anionic templates were generated in situ from the decomposition of dithiophosphate (dtp) ligands. The extrusion of sulfur undergoes disproportionation reactions to generate sulfide and sulfate anions, which provide the source of templates in the subsequent cluster assembly reactions. Two Ag₄₀ clusters display high similarity in their structures. The sulfide (selenide) anions and the central sulfate anion reveal a six-coordinate and a rare dodecametallic dodecaconnective pattern, respectively. Four near-equivalent [Ag₁₀(E){S₂P(OEt)₂}₆]²⁺ motifs were assembled via the connection of central sulfate anion to construct Ag₄₀ clusters. The cluster cation, [Ag₄₀(E)₄(SO₄){S₂P(OEt)₂}₂₄]⁶⁺, displayed in T symmetry, is unprecedented in anion-templated silver clusters.     

Tandem Silver Cluster Isomerism and Mixed Linkers to Modulate the Photoluminescence of Cluster‐Assembled Materials

Silver chalcogenolate cluster assembled materials (SCAMs) are a category of promising light‐emitting materials the luminescence of which can be modulated by variation of their building blocks (cluster nodes and organic linkers). The transformation of a singly emissive [Ag₁₂(SBu^t)₈(CF₃COO)₄(bpy)₄]_n (Ag₁₂bpy, bpy=4,4′‐bipyridine) into a dual‐emissive [(Ag₁₂(SBu^t)₆(CF₃COO)₆(bpy)₃)]_n (Ag₁₂bpy‐2) via cluster‐node isomerization, the critical importance of which was highlighted in dictating the photoluminescence properties of SCAMs. Moreover, the newly obtained Ag₁₂bpy‐2 served to construct visual thermochromic Ag₁₂bpy‐2/NH₂ by a mixed‐linker synthesis, together with dichromatic core–shell Ag₁₂bpy‐2@Ag₁₂bpy‐NH₂‐2 via solvent‐assisted linker exchange. This work provides insight into the significance of metal arrangement on physical properties of nanoclusters.     

An All‐Alkynyl Protected 74‐Nuclei Silver(I)–Copper(I)‐Oxo Nanocluster: Oxo‐Induced Hierarchical Bimetal Aggregation and Anisotropic Surface Ligand Orientation

The hardness of oxo ions (O^2?) means that coinage‐metal (Cu, Ag, Au) clusters supported by oxo ions (O^2?) are rare. Herein, a novel μ₄‐oxo supported all‐alkynyl‐protected silver(I)–copper(I) nanocluster [Ag_74?xCu_xO₁₂(PhC≡C)₅₀] ( NC‐1 , avg. x=37.9) is characterized. NC‐1 is the highest nuclearity silver–copper heterometallic cluster and contains an unprecedented twelve interstitial μ₄‐oxo ions. The oxo ions originate from the reduction of nitrate ions by NaBH₄. The oxo ions induce the hierarchical aggregation of Cu^I and Ag^I ions in the cluster, forming the unique regioselective distribution of two different metal ions. The anisotropic ligand coverage on the surface is caused by the jigsaw‐puzzle‐like cluster packing incorporating rare intermolecular C?H???metal agostic interactions and solvent molecules. This work not only reveals a new category of high‐nuclearity coinage‐metal clusters but shows the special clustering effect of oxo ions in the assembly of coinage‐metal clusters.     

Adamantyl‐ and Furanyl‐Protected Nanoscale Silver Sulfide Clusters

The silver salts of 1‐adamantanethiol (AdSH) and furan‐2‐ylmethanethiol (FurCH₂SH) were successfully applied as building blocks for ligand‐protected Ag₂S nanoclusters. The reaction of the silver thiolates [AgSAd]_x and [AgSCH₂Fur]_x with S(SiMe₃)₂ and 1,5‐bis(diphenylphosphino)pentane (dpppt) afforded three different clusters with 58, 94 and, 190 silver atoms. The intensely colored compounds [Ag₅₈S₁₃(SAd)₃₂] ( 1 ), [Ag₉₄S₃₄(SAd)₂₆(dpppt)₆] ( 2 ), and [Ag₁₉₀S₅₈(SCH₂Fur)₇₄(dpppt)₈] ( 3 ) were structurally characterized by single‐crystal X‐ray diffraction and exhibit different cluster core geometries and ligand shells. The diameters of the well‐defined sphere‐shaped nanoclusters range from 2.2 nm to 3.5 nm.     

Different Silver Nanoparticles in One Crystal: Ag210(iPrPhS)71(Ph3P)5Cl and Ag211(iPrPhS)71(Ph3P)6Cl

Two pure silver nanoparticles (Ag₂₁₀(ⁱPrPhS)₇₁(Ph₃P)₅Cl and Ag₂₁₁(ⁱPrPhS)₇₁(Ph₃P)₆Cl labeled as SD/Ag210 and SD/Ag211 (SD=SunDi), were found to co‐crystallize in forming compound 1 . Single‐crystal X‐ray diffraction (SCXRD) revealed that they differ by only one Ag(PPh₃). Their four‐shell nanoparticles consist of three pure Ag metal shells (Ag₁₉@Ag₅₂@Ag₄₅) shielded by a silver‐organic Ag₈₉(ⁱPrPhS)₇₁Cl[Ag(Ph₃P)]_n outermost shell. The number (n) of Ag(Ph₃P) is five for SD/Ag210 and six for SD/Ag211. The pseudo‐fivefold symmetric Ag nanoparticles exhibit surface plasmon absorption similar to a true metallic state but at the nanoscale. This work exemplifies the important effects of phosphine in stabilizing large silver nanoparticles; and offers a platform to investigate the origin of differences in nanoscale metal materials, even differing by only one metal atom; it also sheds light on the regioselective binding of auxiliary Ph₃P on the surface of silver nanoparticles.     

Isolation of Homo-/Mixed-Valence Ag12, Ag29, and Ag8 Clusters Stabilized by Cyclic Alkyl(amino) Carbene-Anchored Monoanionic Phosphorus Ligand

Silver clusters are attractive candidates for their promising optical properties, and biomedical activities. Herein, we report on the first syntheses and isolation of three homo-/mixed-valence silver nanoclusters (NCs) with Ag₁₂Cl₃, Ag₂₉, and Ag₈ cores [((cAAC)P)₆Ag₁₂Cl₃](OTf)₃ ( 1 ), [((cAAC)P)₆Ag₂₉] ( 2 ), and [((cAAC)P)₄Ag₈] ( 3 ) having three-/twofold symmetry, employing cyclic alkyl(amino) carbene (cAAC)-supported phosphinidenide (cAACP⁻) as the π-accepting stabilizing ligand. The average diameters of Ag NCs 1 , and 2 are approximately 1.6 to 2 nm. The redox non-innocent mono-atomic phosphorus anions (P⁻) anchored with cAAC ligands are generated in situ by the reaction of AgOTf with a boryl-phosphaalkene (cAAC)P−B(NⁱPr₂)₂ through cleavage of the P−B bond with the help of a triflate anion (OTf⁻) as a weak nucleophile. Equivalent number of the (cAAC)P⁻ anions generated in situ are oxidized to produce the corresponding bis-phosphinidene (cAAC)₂P₂ leading to the generation of Ag⁰ ions in solution for the formation of the unprecedented mixed-valence Ag NC 2 . Complex 3 is achieved by treating potassium phosphinidenide cAACPK with AgNTf₂. The ligand field and the steric hindrance of the (cAAC)P units play crucial roles in stabilizing complexes 1 – 3 , further providing a three- ( 1 , 2 )/two- ( 3 ) fold stand. The Ag₁₂Cl₃ NC ( 1 ) with a tricationic core [Ag^I₁₂Cl₃] was found to be diamagnetic, and fluorescent, emitting green light at 563 nm when excited at 400 nm. In contrast, the neutral Ag₂₉ ( 2 ) and Ag₈ ( 3 ) clusters were found to be paramagnetic, and NMR silent showing characteristic EPR signals for Ag⁰ at room temperature.