Chalcogens-Induced Ag6Z4@Ag36 (Z = S or Se) Core–Shell Nanoclusters: Enlarged Tetrahedral Core and Homochiral Crystallization

Atomically Precise Chiral Metal Nanoclusters for Circularly Polarized Light Detection

Circularly polarized light (CPL) detection is of great significance in various applications such as drug identification, sensing and imaging. Atomically precise chiral metal nanoclusters with intense circular dichroism (CD) signals are promising candidates for CPL detection, which can further facilitate device miniaturization and integration. Herein, we report the preparation of a pair of optically active chiral silver nanoclusters [Ag7(R/S-DMA)2(dpppy)3] (BF4)3 (R/S-Ag7) for direct CPL detection. The crystal structure and molecular formula of R/S-Ag7 clusters are confirmed by single-crystal X-ray diffraction and high-resolution mass spectrometry. R/S-Ag7 clusters exhibit strong CD spectra and CPL both in solution and solid states. When used as the photoactive materials in photodetectors, R/S-Ag7 enables effective discrimination between left-handed circularly polarized and right-handed circularly polarized light at 520 nm with short response time, high responsivity and considerable discrimination ratio. This study is the first report on using atomically precise chiral metal nanoclusters for CPL detection.

Zwitterionic Thiolate-Protected Ag22(0/I) and Ag20(I) Clusters: Assembly, Structural Characterization, and Antibacterial Activity

Zwitterionic thiolate ligands have the potential to introduce novel assembly modes and functions for noble metal clusters. However, their utilization in the synthesis of silver clusters remains understudied, particularly for the clusters containing reductive Ag(0) species. In this article, we report the first synthesis of a mixed-valence silver(0/I) cluster protected by zwitterionic Tab as thiolate ligands (Tab = 4-(trimethylammonio)benzenethiolate), denoted as [Ag22(Tab)24](PF6)20·16CH3OH·6Et2O (Ag22·16CH3OH·6Et2O), alongside an Ag(I) cluster [Ag20(Tab)12(PhCOO)10(MeCN)2(H2O)](PF6)10·11MeCN (Ag20·11MeCN). Ag22 has a distinct hierarchical supratetrahedral structure with a central {Ag6} kernel surrounded by four [Ag4(Tab)6]4+ units. High-resolution electrospray ionization mass spectra demonstrate that Ag22 has two free electrons, indicating a superatomic core. Ag20 has a drum-like [Ag12(Tab)6(PhCOO)6(H2O)]6+ inner core capped by two tetrahedral-like [Ag4(Tab)3(PhCOO)2(MeCN)]2+ units. Ag20 can be transformed into Ag22 after its reaction with NaBH4 in solution. Antibacterial measurements reveal that Ag22 has a significantly lower minimum inhibitory concentration than that of the Ag20 cluster. This work not only extends the stabilization of silver(0/I) clusters to neutral thiol ligands but also offers new materials for the development of novel antibacterial materials.

Micro-Ring Morphology of Ag7NCs and Light-Induced Reversible Interconversion of FCC Ag14NCs via Cu2+ ions-Mediated Particle-Assisted Reversible Interconversion

Despite the remarkable progress made on intercluster conversion in atomically precise metal nanoclusters (MNCs) and their self-organization to develop microscopic molecular architecture with well-defined size and shape, achieving light-induced reversible structural transformation and the development of micro-ring self-assembly in MNCs have, so far, remained elusive. The present investigation touches on these two long-standing quests by showcasing a new route, light-induced Particle-Assisted Reversible Interconversion (PARI) for the reversible transformation from Face Centered Cubic (FCC) Ag14NCs to Ag7NCs. Our studies reveal that the lack of plasmonic silver nanoparticles (AgNPs) in the system results in the formation of Ag7NCs with metallic kernels having centrosymmetric crystal packing. The molecular self-organization of Ag7NCs through various non-covalent interactions such as C-H⋅⋅⋅O, C-H⋅⋅⋅H-C, and C-H⋅⋅⋅π leads to the formation of micro-ring morphology, a unique molecular architecture in MNCs. The in situ generated AgNPs due to the acceleration of the reaction kinetics by Cu2+ ions facilitate the growth of Ag14NCs with FCC metallic kernel. These two structural units of AgNCs show light-induced reversible structural transformation which is also associated with the reversible tuning of their spectroscopic and morphological signatures. This PARI-guided interconversion strategy put forward a most appropriate example of a structure-property relationship in MNCs.

Chemical Flexibility of Atomically Precise Metal Clusters

Ligand-protected metal clusters possess hybrid properties that seamlessly combine an inorganic core with an organic ligand shell, imparting them exceptional chemical flexibility and unlocking remarkable application potential in diverse fields. Leveraging chemical flexibility to expand the library of available materials and stimulate the development of new functionalities is becoming an increasingly pressing requirement. This Review focuses on the origin of chemical flexibility from the structural analysis, including intra-cluster bonding, inter-cluster interactions, cluster-environments interactions, metal-to-ligand ratios, and thermodynamic effects. In the introduction, we briefly outline the development of metal clusters and explain the differences and commonalities of M(I)/M(I/0) coinage metal clusters. Additionally, we distinguish the bonding characteristics of metal atoms in the inorganic core, which give rise to their distinct chemical flexibility. Section 2 delves into the structural analysis, bonding categories, and thermodynamic theories related to metal clusters. In the following sections 3 to 7, we primarily elucidate the mechanisms that trigger chemical flexibility, the dynamic processes in transformation, the resultant alterations in structure, and the ensuing modifications in physical-chemical properties. Section 8 presents the notable applications that have emerged from utilizing metal clusters and their assemblies. Finally, in section 9, we discuss future challenges and opportunities within this area.

Plasmon-emitter coupling in cytosine-rich hairpin DNA-templated silver nanoclusters: Thermal reversibility, white light emission, and dynamics inside live cells

Bio-templated luminescent noble metal nanoclusters (NCs) have attracted great attention for their intriguing physicochemical properties. Continuous efforts are being made to prepare NCs with high fluorescence quantum yield (QY), good biocompatibility, and tunable emission properties for their widespread practical applications as new-generation environment-friendly photoluminescent materials in materials chemistry and biological systems. Herein, we explored the unique photophysical properties of silver nanoclusters (AgNCs) templated by cytosine-rich customized hairpin DNA. Our results indicate that a 36-nucleotide containing hairpin DNA with 20 cytosine (C20) in the loop can encapsulate photostable red-emitting AgNCs with an absolute QY of ∼24%. The luminescent properties in these DNA-templated AgNCs were found to be linked to the coupling between the surface plasmon and the emitter. These AgNCs exhibited excellent thermal sensitivity and were employed to produce high-quality white light emission with an impressive color rendering index of 90 in the presence of dansyl chloride. In addition, the as-prepared luminescent AgNCs possessing excellent biocompatibility can effectively mark the nuclear region of HeLa cells and can be employed as a luminescent probe to monitor the cellular dynamics at a single molecular resolution.

Tailoring the subshell and electronic structure of an atomically precise AuAg alloy nanocluster

Manipulating the atomic-level structure of the subshell of a nanocluster while preserving the inner and outer shell structure is challenging. We present the synthesis and molecular structure of an alkynyl-protected Au34Ag27 nanocluster, which exhibits distinct third shell atomic arrangement, electronic structure, and optical properties from those of the Au34Ag28 nanocluster.

A concise guide to chemical reactions of atomically precise noble metal nanoclusters

Nanoparticles (NPs) with atomic precision, known as nanoclusters (NCs), are an emerging field in materials science in view of their fascinating structure-property relationships. Ultrasmall noble metal NPs have molecule-like properties that make them fundamentally unique compared with their plasmonic counterparts and bulk materials. In this review, we present a comprehensive account of the chemistry of monolayer-protected atomically precise noble metal nanoclusters with a focus on the chemical reactions, their diversity, associated kinetics, and implications. To begin with, we briefly review the history of the evolution of such precision materials. Then the review explores the diverse chemistry of noble metal nanoclusters, including ligand exchange reactions, ligand-induced structural transformations, and reactions with metal ions, metal thiolates, and halocarbons. Just as molecules do, these precision materials also undergo intercluster reactions in solution. Supramolecular forces between these systems facilitate the creation of well-defined hierarchical assemblies, composites, and hybrid materials. We conclude the review with a future perspective and scope of such chemistry.

Three in One: Three Different Molybdates Trapped in a Thiacalix[4]arene Protected Ag72 Nanocluster for Structural Transformation and Photothermal Conversion

Polyoxometalates (POMs) represent crucial intermediates in the formation of insoluble metal oxides from soluble metal ions, however, the rapid hydrolysis-condensation kinetics of MoVI or WVI makes the direct characterization of coexisted molecular species in a given medium extremely difficult. Silver nanoclusters have shown versatile capacity to encapsulate diverse POMs, which provides an alternative scene to appreciate landscape of POMs in atomic precision. Here, we report a thiacalix[4]arene protected silver nanocluster (Ag72b) that simultaneously encapsulates three kinds of molybdates (MoO4 2- , Mo6 O22 8- and Mo7 O25 8- ) in situ transformed from classic Lindqvist Mo6 O19 2- , providing more deep understanding on the structural diversity and condensation growth route of POMs in solution. Ag72b is the first silver nanocluster trapping so many kinds of molybdates, which in turn exert collective template effect to aggregate silver atoms into a nanocluster. The post-reaction of Ag72b with AgOAc or PhCOOAg produces a discrete Ag24 nanocluster (Ag24a) or an Ag28 nanocluster based 1D chain structure (Ag28a), respectively. Moreover, the post-synthesized Ag28a can be utilized as potential ignition material for further application. This work not only provides an important model for unlocking dynamic features of POMs at atom-precise level but also pioneers a promising approach to synthesize silver nanoclusters from known to unknown.

Thiacalix[4]arene-Protected Silver Nanoclusters Encapsulating Different Two-Electron Superatom Oligomers

The subvalent silver kernel represents the nascent state of silver cluster formation, yet the growth mechanism has long been elusive. Herein, two silver nanoclusters (Ag30 and Ag34) coprotected by TC4A4- (H4TC4A = p-tert-butylthiacalix[4]arene) and TBPMT- (TBPMTH = 4-tert-butylbenzenemethanethiol) containing 6e and 4e silver kernels are synthesized and characterized. The trimer of the 2e superatom Ag14 kernel in Ag30 is built from a central Ag6 octahedron sandwiched by two orthogonally oriented Ag5 trigonal bipyramids through sharing vertexes, whereas a double-octahedral Ag10 kernel in Ag34 is a dimer of 2e superatoms. They manifest disparate polyhedron fusion growth patterns at the beginning of the silver cluster formation. Their excellent solution stabilities are contributed by the multisite and multidentate coordination fashion of TC4A4- and the special valence electron structures. This work demonstrates the precise control of silver kernel growth by the solvent strategy and lays a foundation for silver nanocluster application in photothermal conversion.

Total Structure, Electronic Structure and Catalytic Hydrogenation Activity of Metal-Deficient Chiral Polyhydride Cu57 Nanoclusters

Accurate identifying and in-depth understanding of the defect sites in a working nanomaterial could hinge on establishing specific defect-activity relationships. Yet, atomically precise coinage-metal nanoclusters (NCs) possessing surface vacancy defects are scarce primarily owing to challenges in the synthesis and isolation of such defective NCs. Herein we report a mixed-ligand strategy to synthesizing an intrinsically chiral and metal-deficient copper hydride-rich NC [Cu57 H20 (PET)36 (TPP)4 ]+ (Cu57 H20 ). Its total structure (including hydrides) and electronic structure are well established by combined experimental and computational results. Crystal structure reveals Cu57 H20 features a cube-like Cu8 kernel embedded in a corner-missing metal-ligand shell of Cu49 (PET)36 (TPP)4 . Single Cu vacancy defect site occurs at one corner of the shell, evocative of mono-lacunary polyoxometalates. Theoretical calculations demonstrate that the above-mentioned point vacancy causes one surface hydride exposed as an interfacial capping μ3 -H- , which is accessible in chemical reaction, as proved by deuterated experiment. Moreover, Cu57 H20 shows catalytic activity in the hydrogenation of nitroarene. The success of this work opens the way for the research on well-defined chiral metal-deficient Cu and other metal NCs, including exploring their application in asymmetrical catalysis.

Unveiling the Remarkable Stability and Catalytic Activity of a 6-Electron Superatomic Ag30 Nanocluster for CO2 Electroreduction

Nanocluster catalysts face a significant challenge in striking the right balance between stability and catalytic activity. Here, we present a thiacalix[4]arene-protected 6-electron [Ag30(TC4A)4(iPrS)8] nanocluster that demonstrates both high stability and catalytic activity. The Ag30 nanocluster features a metallic core, Ag104+, consisting of two Ag3 triangles and one Ag4 square, shielded by four {Ag5@(TC4A)4} staple motifs. Based on DFT calculations, the Ag104+ metallic kernel can be viewed as a trimer comprising 2-electron superatomic units, exhibiting a valence electron structure similar to that of the Be3 molecule. Notably, this is the first crystallographic evidence of the trimerization of 2-electron superatomic units. Ag30 can reduce CO2 into CO with a Faraday efficiency of 93.4% at -0.9 V versus RHE along with excellent long-term stability. Its catalytic activity is far superior to that of the chain-like AgI polymer ∞1{[H2Ag5(TC4A)(iPrS)3]} (∞1Agn), with the composition similar to Ag30. DFT calculations elucidated the catalytic mechanism to clarify the contrasting catalytic performances of the Ag30 and ∞1Agn polymers and disclosed that the intrinsically higher activity of Ag30 may be due to the greater stability of the dual adsorption mode of the *COOH intermediate on the metallic core.

Cocrystallization of Two Negatively Charged Dimercaptomaleonitrile-Stabilized Silver Nanoclusters

Studies on the assembly of atomically precise metal nanoclusters (NCs) are of great significance in the nanomaterial field, which has attracted increasing interest in the last few decades. Herein, we report the cocrystallization of two negatively charged atom-precise silver nanoclusters, the octahedral [Ag₆₂(MNT)₂₄(TPP)₆]^8- (Ag₆₂) and the truncated-tetrahedral [Ag₂₂(MNT)₁₂(TPP)₄]^4- (Ag₂₂) in a 1:2 ratio (MNT^2- = dimercaptomaleonitrile, TPP = triphenylphosphine). As far as we know, a cocrystal containing two negatively charged NCs has seldom been reported. Single-crystal structure determinations reveal that the component Ag₂₂ and Ag₆₂ NCs both adopt core-shell structures. In addition, the component NCs were separately obtained by adjusting the synthetic conditions. This work enriches the structural diversity of silver NCs and extends the family of cluster-based cocrystals.

Unusual core engineering on a copper hydride nanoball

A neutral polyhydrido copper cluster, [Cu₂₇H₁₅{S₂CNⁿBu₂}₁₂] (abbreviated as [Cu₂₇H₁₅]), was prepared by the reaction of dithiocarbamates (dtc), Cu(I) salts and NaBH₄. The isolated cluster provides insights into core engineering, demonstrating its novel ability to reversibly add or remove one copper atom from the cluster core. Single-crystal X-ray analysis reveals that the new core-shell structure exhibits a Cu₂₄ rhombicuboctahedral outer cage and an inner Cu₃ triangular kernel. The two core-shell clusters, [Cu₂₇H₁₅{S₂CNⁿBu₂}₁₂] and previously published [Cu₂₈H₁₅(S₂CNⁿBu₂)₁₂]⁺ (abbreviated as [Cu₂₈H₁₅]⁺), are only differentiated by one copper atom in their inner core. Importantly, we demonstrate core engineering with the controllable reversible transition between an irregular Cu₄ tetrahedron and a Cu₃ triangle, whilst maintaining their outer Cu₂₄ shell intact. The 15 hydride atoms in [Cu₂₇H₁₅], coordinated in three different modes, are co-incident with the hydride positions in [Cu₂₈H₁₅]⁺. The degradation of [Cu₂₇H₁₅] in solution or the addition of one eq. of Cu(I) ions leads to the conversion of [Cu₂₇H₁₅] into [Cu₂₈H₁₅]⁺, while the reverse transformation can be achieved by the addition of either formic acid or a reducing agent to [Cu₂₈H₁₅]⁺. A dicationic species was observed in the ESI mass spectrum, and the composition is formulated as [Cu₅₆H₃₀(S₂CNⁿBu₂)₂₄]²⁺, a dimer of [Cu₂₇H₁₅(S₂CNⁿBu₂)₁₂ + Cu⁺]₂²⁺. The dimeric species was further explored by DFT calculations, suggesting that the lowest energy structure consists of a [Cu₂₈H₁₅]⁺ and a [Cu₂₇H₁₅] cluster connected through one Cu⁺ atom bridge. As a result, [Cu₂₇H₁₅] is considered an intermediate species in the formation of the more stable [Cu₂₈H₁₅]⁺ nanoball.

Platonic and Archimedean solids in discrete metal-containing clusters

Metal-containing clusters have attracted increasing attention over the past 2-3 decades. This intense interest can be attributed to the fact that these discrete metal aggregates, whose atomically precise structures are resolved by single-crystal X-ray diffraction (SCXRD), often possess intriguing geometrical features (high symmetry, aesthetically pleasing shapes and architectures) and fascinating physical properties, providing invaluable opportunities for the intersection of different disciplines including chemistry, physics, mathematical geometry and materials science. In this review, we attempt to reinterpret and connect these fascinating clusters from the perspective of Platonic and Archimedean solid characteristics, focusing on highly symmetrical and complex metal-containing (metal = Al, Ti, V, Mo, W, U, Mn, Fe, Co, Ni, Pd, Pt, Cu, Ag, Au, lanthanoids (Ln), and actinoids) high-nuclearity clusters, including metal-oxo/hydroxide/chalcogenide clusters and metal clusters (with metal-metal binding) protected by surface organic ligands, such as thiolate, phosphine, alkynyl, carbonyl and nitrogen/oxygen donor ligands. Furthermore, we present the symmetrical beauty of metal cluster structures and the geometrical similarity of different types of clusters and provide a large number of examples to show how to accurately describe the metal clusters from the perspective of highly symmetrical polyhedra. Finally, knowledge and further insights into the design and synthesis of unknown metal clusters are put forward by summarizing these "star" molecules.

Nanocluster Transformation Induced by SbF6- Anions toward Boosting Photochemical Activities

The interactions between SbF₆^- and metal nanoclusters are of significance for customizing clusters from both structure and property aspects; however, the whole-segment monitoring of this customization remains challenging. In this work, by controlling the amount of introduced SbF₆^- anions, the step-by-step nanocluster evolutions from [Pt₁Ag₂₈(S-Adm)₁₈(PPh₃)₄]Cl₂ (Pt₁Ag₂₈-Cl) to [Pt₁Ag₂₈(S-Adm)₁₈(PPh₃)₄](SbF₆)₂ (Pt₁Ag₂₈-SbF₆) and then to [Pt₁Ag₃₀Cl₁(S-Adm)₁₈(PPh₃)₃](SbF₆)₃ (Pt₁Ag₃₀-SbF₆) have been mapped out with X-ray crystallography, with which atomic-level SbF₆^- counterion effects in reconstructing and rearranging nanoclusters are determined. The structure-dependent optical properties, including optical absorption, photoluminescence, and electrochemiluminescence (ECL), of these nanoclusters are then explored. Notably, the Pt₁Ag₃₀-SbF₆ nanocluster was ultrabright with a high phosphorescence quantum yield of 85% in N₂-purged solutions, while Pt₁Ag₂₈ nanoclusters were fluorescent with weaker emission intensities. Furthermore, Pt₁Ag₃₀-SbF₆ displayed superior ECL efficiency over Pt₁Ag₂₈-SbF₆, which was rationalized by its increased effectively exposed reactive facets. Both Pt₁Ag₃₀-SbF₆ and Pt₁Ag₂₈-SbF₆ demonstrated unprecedented high absolute ECL quantum efficiencies at sub-micromolar concentrations. This work is of great significance for revealing the SbF₆^- counterion effects on the control of both structures and luminescent properties.

Synthesis of Two Neutral Silver Alkynyl Nanoclusters by a Single Divalent Tetrahedral Anion Template and a Study of Their Optical Features

The synthesis of nanoclusters from simple structural units is usually a challenging process because of the complexity and unpredictability of the self-assembly process of these types of compounds. Herein, two new neutral 19-nuclearity silver nanoclusters based on alkynyl ligands with the formulas [(CrO₄)@Ag₁₉(C≡C^tBu)₈(Ph₂PO₂)₆(tfa)₃(CH₃OH)₂] (1) and [(SO₄)@Ag₁₉(C≡C^tBu)₈(Ph₂PO₂)₆(tfa)₃(CH₃OH)₂] (2), in which tfa = trifluoroacetate, were synthesized, and their structures were investigated by single-crystal and powder X-ray diffraction, electrospray ionization mass spectrometry, elemental analyses, and Fourier transform infrared spectroscopy. The surface ligands of Ph₂PO₂H and trifluoroacetate were assembled through hydrogen bonding, metal-aromatic interactions, and coordination bonding around 19 silver atoms as the metal skeletons of the nanoclusters. Sulfate and chromate anions, as a template within the metal skeleton of clusters through bonding with silver atoms, stabilized the structure. In addition, the UV-vis absorption spectroscopy, luminescence properties, and thermal stability of the nanoclusters were investigated.

Snapshots of key intermediates unveiling the growth from silver ions to Ag70 nanoclusters

Nanoclusters (NCs) are considered as initial states of condensed matter, and unveiling their formation mechanism is of great importance for directional synthesis of nanomaterials. Here, we initiate the reaction of Ag(i) ions under weak reducing conditions. The prolonged reaction period provides a unique opportunity for revealing the five stages of the growth mechanism of 20-electron superatomic Ag70 NCs by a time-dependent mass technique, that is, aggregate (I) → reduction (II) → decomposition and recombination (III) → fusion (IV) → surface recombination and motif enrichment (V), which is different from the formation process applicable to the gold clusters. More importantly, the key intermediates, Ag14 without free electrons (0e) in the first (stage I) and Ag24 (4e) in the second (stage II), were crystallized and structurally resolved, and the later transformation rate towards Ag70 was further controlled by modulating solvents for easy identification of more intermediates. In a word, we establish a reasonable path of gradual expansion in size and electrons from Ag(i) ions to medium-sized 20e Ag70. This work provides new insights into the formation and evolution of silver NCs, and unveils the corresponding optical properties along with the process.

Sulfide Boosting Near-Unity Photoluminescence Quantum Yield of Silver Nanocluster

Silver nanoclusters have emerged as promising candidates for optoelectronic applications, but their room-temperature photoluminescence quantum yield (PLQY) is far from ideal to access cutting-edge device performance. Herein, two supertetrahedral silver nanoclusters with high PLQY in non-degassed solution at room temperature were constructed by interiorly supporting the core with multiple VO₄^3- and E^2- anions as structure-directing agents and exteriorly protecting the core with a rigid ligand shell of PhC≡C^- and Ph₂PE₂^- (E = S, Ag64-S; E = Se, Ag64-Se). Both clusters have similar outer Ag₅₈ tetrahedral cages and [Ag₆E₄@(VO₄)₄] cores, forming a pair of comparable clusters to decrypt the origin of such a high PLQY, particularly in Ag64-S, where the PLQY reached up to 97%. The stronger suppression effect of inner sulfides for nonradiative decay is critical to boost the PLQY to near unity. Transient absorption spectroscopy is employed to confirm the phosphorescence nature. The quadruple-capping assembly mechanism involving Ag₇ secondary building units on a Ag₃₆ truncated tetrahedron was also established by collision-induced dissociation studies. This work not only provides a strategy of core engineering for the controlled syntheses of silver nanoclusters with high PLQY but also deciphers the origin of a near-unity PLQY, which lays a foundation for fabricating highly phosphorescent silver nanoclusters in the future.

N-Heterocyclic Thione-Protected Ag4 Tetrahedra and Ag8 Cubes Cocrystallized in a Single Crystal

Polynuclear silver clusters have attracted intensive attention in the academic community owing to their rich physicochemical properties. The development of thione-protected silver clusters has been lagging behind the well-explored thiolate-protected silver-sulfide clusters. Herein, we report two N-heterocyclic thione-protected silver clusters: [Ag₄(2-TBI)₆(SO₄)₃]^2- (Ag₄) and [Br@Ag₈(2-TBI)₁₂(SO₄)₂]³⁺ (Ag₈) (2-TBI = 2-thiobenzimidazol), which cocrystallize to form cluster-based molecular crystals with a CaF₂-type structure. The cocrystal shows high thermal stability in air. Notably, the two cluster-based layers are alternately assembled to exhibit a unique k-vector-differential crystallographic arrangement. This work may lay a foundation for synthesis of atomically precise and stable silver clusters using readily available N-heterocyclic thione ligands.

The New Ag-S Cluster [Ag50S13(StBu)20][CF3COO]4 with a Unique hcp Ag14 Kernel and Ag36 Keplerian-Shell-Based Structural Architecture and Its Photoresponsivity

In metal nanoclusters (NCs), the kernel geometry and the nature of the surface protecting ligands are very crucial for their structural stability and properties. The synthesis and structural elucidation of Ag NCs is challenging because the zerovalent oxidation state of Ag is very reactive and prone to oxidization. Here, we report the NC [Ag₅₀S₁₃(S^tBu)₂₀][CF₃COO]₄ with a hexagonal close-packed (hcp) cagelike Ag₁₄ kernel. A truncated cubic shell and an octahedral shell encapsulate the hcp-layered kernel via an interstitial S^2- anionic shell to form an Ag₃₆ Keplerian outer shell of the NC. A theoretical study indicates the stability of this NC in its 4+ charge state and the charge distribution between the kernel and Keplerian shell. The unprecedented electronic structure facilitates its application toward sustainable photoresponse properties. The new insights into this novel Ag NC kernel and Keplerian shell structure may pave the way to understanding the unique structure and developing electronic structure-based applications.

Small symmetry-breaking triggering large chiroptical responses of Ag70 nanoclusters

The origins of the chiroptical activities of inorganic nanostructures have perplexed scientists, and deracemization of high-nuclearity metal nanoclusters (NCs) remains challenging. Here, we report a single-crystal structure of Rac-Ag₇₀ that contains enantiomeric pairs of 70-nuclearity silver clusters with 20 free valence electrons (Ag₇₀), and each of these clusters is a doubly truncated tetrahedron with pseudo-T symmetry. A deracemization method using a chiral metal precursor not only stabilizes Ag₇₀ in solution but also enables monitoring of the gradual enlargement of the electronic circular dichroism (CD) responses and anisotropy factor g_abs. The chiral crystals of R/S-Ag₇₀ in space group P2₁ containing a pseudo-T-symmetric enantiomeric NC show significant kernel-based and shell-based CD responses. The small symmetry breaking of T_d symmetry arising from local distortion of Ag−S motifs and rotation of the apical Ag₃ trigons results in large chiroptical responses. This work opens an avenue to construct chiral medium/large-sized NCs and nanoparticles, which are promising for asymmetric catalysis, nonlinear optics, chiral sensing, and biomedicine.

Having control over the chirality of metal nanoclusters is challenging. Here, the authors report the deracemization of silver nanoclusters and monitor the chiroptical responses.

Atomically precise metal chalcogenide supertetrahedral clusters: frameworks to molecules, and structure to function

Metal chalcogenide supertetrahedral clusters (MCSCs) are of significance for developing crystalline porous framework materials and atomically precise cluster chemistry. Early research interest focused on the synthetic and structural chemistry of MCSC-based porous semiconductor materials with different cluster sizes/compositions and their applications in adsorption-based separation and optoelectronics. More recently, focus has shifted to the cluster chemistry of MCSCs to establish atomically precise structure-composition-property relationships, which are critical for regulating the properties and expanding the applications of MCSCs. Importantly, MCSCs are similar to II-VI or I-III-VI semiconductor nanocrystals (also called quantum dots, QDs) but avoid their inherent size polydispersity and structural ambiguity. Thus, discrete MCSCs, especially those that are solution-processable, could provide models for understanding various issues that cannot be easily clarified using QDs. This review covers three decades of efforts on MCSCs, including advancements in MCSC-based open frameworks (reticular chemistry), the precise structure-property relationships of MCSCs (cluster chemistry), and the functionalization and applications of MCSC-based microcrystals. An outlook on remaining problems to be solved and future trends is also presented.

The mystery of Ph3PS revealed in magic-size Ag–S cluster nucleation

PPh3S was employed to direct the regulation of {Ag32S3} cluster by slowing down the kinetic process of nucleation. The process that Agn(CCBut)m and traces of water induces breakage of PS from [Ag2(Ph3PS)4]2+ to generate {Ag32S3} was established.

Structural rearrangement of Ag60 nanocluster endowing different luminescence performances

It is well known that structure determines property, but obtaining a pair of silver nanoclusters with comparable structures to understand the structure-property relationship is a very challenging task. A new 60-nuclei silver nanocluster (SD/Ag60a) protected by a mixed-ligand shell of ^tBuS^- and o-CH₃OPhCOO^- was obtained and characterized. Single crystal x-ray diffraction reveals that SD/Ag60a has an identical metal nuclearity and core-shell structural type to SD/Ag1 previously reported by our group, whereas the compositions of the core and shell have undergone a rearrangement from an Ag₁₂ cuboctahedron core and an Ag₄₈ rhombicuboctahedron shell in SD/Ag1 to an Ag₁₄ rhombic dodecahedron core and an oval Ag₄₆ shell in SD/Ag60a. The core enlargement from Ag₁₂ to Ag₁₄ originates from the replacement of two S^2- in Ag₁₂S₁₅ by two Ag⁺, which gives a new Ag₁₄S₁₃ core. This result indicates that the metal frameworks of silver nanoclusters have some extent flexibility despite the same nuclearity, which can be influenced by ligands, solvents, anion templates, and others in the embryonic stage of the assembly. Interestingly, different core-shell architectures of Ag₆₀ nanoclusters also significantly endow the different optical absorption bands, photocurrent-generating properties, and luminesecent behaviors. This work not only realizes the regulation of the core-shell structure of silver nanoclusters with the same nuclearity but also provides a comparable model for investigating the relationship of structure-photoelectric properties.

[Ag71(S-tBu)31(Dppm)](SbF6)2: an intermediate-sized metalloid silver nanocluster containing a building block of Ag64

An intermediate-sized atomically precise metalloid silver nanocluster [Ag₇₁(SR)₃₁(Dppm)](SbF₆)₂ (Dppm = bis (diphenylphosphino)methane, SR = S-^tBu) is reported, which comprises one building block Ag₆₄, six SR₅ pentagons, one sole SR ligand, a DppmAg₂ handle, and an Ag₅ lid. Structurally, a decahedron Ag₂₃ kernel is observed in the metalloid silver nanocluster. Moreover, the Ag₆₄ unit provides insights into the growth of large clusters such as Ag₁₃₆(SR)₆₄Cl₃ and Ag₁₄₁(SR)₄₀Br₁₂via assembly. The observed decahedron Ag₂₃ provides a deeper understanding on Marks decahedron in larger nanoclusters, and the [Ag₇₁(S-^tBu)₃₁(Dppm)](SbF₆)₂ uses Ag₆₄ as a building block to predict the structure of larger metalloid nanoclusters.

A New Synthetic Methodology in the Preparation of Bimetallic Chalcogenide Clusters via Cluster-to-Cluster Transformations

A decanuclear silver chalcogenide cluster, [Ag₁₀(Se){Se₂P(OⁱPr)₂}₈] (2) was isolated from a hydride-encapsulated silver diisopropyl diselenophosphates, [Ag₇(H){Se₂P(OⁱPr)₂}₆], under thermal condition. The time-dependent NMR spectroscopy showed that 2 was generated at the first three hours and the hydrido silver cluster was completely consumed after thirty-six hours. This method illustrated as cluster-to-cluster transformations can be applied to prepare selenide-centered decanuclear bimetallic clusters, [Cu_xAg_10-x(Se){Se₂P(OⁱPr)₂}₈] (x = 0-7, 3), via heating [Cu_xAg_7-x(H){Se₂P(OⁱPr)₂}₆] (x = 1-6) at 60 °C. Compositions of 3 were accurately confirmed by the ESI mass spectrometry. While the crystal 2 revealed two un-identical [Ag₁₀(Se){Se₂P(OⁱPr)₂}₈] structures in the asymmetric unit, a co-crystal of [Cu₃Ag₇(Se){Se₂P(OⁱPr)₂}₈]_0.6[Cu₄Ag₆(Se){Se₂P(OⁱPr)₂}₈]_0.4 ([3a]_0.6[3b]_0.4) was eventually characterized by single-crystal X-ray diffraction. Even though compositions of 2, [3a]_0.6[3b]_0.4 and the previous published [Ag₁₀(Se){Se₂P(OEt)₂}₈] (1) are quite similar (10 metals, 1 Se^2-, 8 ligands), their metal core arrangements are completely different. These results show that different synthetic methods by using different starting reagents can affect the structure of the resulting products, leading to polymorphism.

Revealing the chirality origin and homochirality crystallization of Ag14 nanocluster at the molecular level

Although chirality is an ever-present characteristic in biology and some artificial molecules, controlling the chirality and demystifying the chirality origin of complex assemblies remain challenging. Herein, we report two homochiral Ag₁₄ nanoclusters with inherent chirality originated from identical rotation of six square faces on a Ag₈ cube driven by intra-cluster π···π stacking interaction between pntp⁻ (Hpntp = p-nitrothiophenol) ligands. The spontaneous resolution of the racemic (SD/rac-Ag14a) to homochiral nanoclusters (SD/L-Ag14 and SD/R-Ag14) can be realized by re-crystallizing SD/rac-Ag14a in acetonitrile, which promotes the homochiral crystallization in solid state by forming C–H···O/N hydrogen bonds with nitro oxygen atoms in pntp⁻ or aromatic hydrogen atoms in dpph (dpph = 1,6-bis(diphenylphosphino)hexane) on Ag₁₄ nanocluster. This work not only provides strategic guidance for the syntheses of chiral silver nanoclusters in an all-achiral environment, but also deciphers the origin of chirality at molecular level by identifying the special effects of intra- and inter-cluster supramolecular interactions.

The preparation of chiral monolayer-protected metal clusters is interesting for their potential applications in a variety of fields, including catalysis. Here, the authors synthesize chiral Ag₁₄ nanoclusters in an all-achiral environment, and decipher the origin of chirality at the molecular level; the solvent choice is key to achieve homochiral crystallization.

[Au16Ag43H12(SPhCl2)34]5-: An Au-Ag Alloy Nanocluster with 12 Hydrides and Its Enlightenment on Nanocluster Structural Evolution

The structural determination of alloy hydride nanoclusters with high nuclearity remains challenging. We herein report the synthetic procedure and the structural elucidation of an Au-Ag alloy nanocluster with 12 hydride ligands-[Au₁₆Ag₄₃H₁₂(SPhCl₂)₃₄]^5-. The structure of [Au₁₆Ag₄₃H₁₂(SPhCl₂)₃₄]^5- comprises an Au₁₆Ag₃ kernel that is stabilized by 12 hydride ligands, 8 thiol bridges, and 6 Ag_m(SR)_n motif units. The 12 hydride ligands in Au₁₆Ag₄₃ have been confirmed by both ²H NMR and ESI-MS measurements, and their positions have been theoretically evaluated, located at the interlayer between the Au₁₆Ag₃ kernel and the Ag-SR shell. The metastable [Au₁₆Ag₄₃H₁₂(SPhCl₂)₃₄]^5- can convert to [Au₁₂Ag₃₂(SPhCl₂)₃₀]^4- spontaneously. Structurally, the Au₁₆Ag₃ kernel of [Au₁₆Ag₄₃H₁₂(SPhCl₂)₃₄]^5- could be regarded as the overlapping of two hollow Au₈Ag₃ cages via sharing an Ag₃ line, which is in contrast to the solely icosahedral Au₁₂ kernel of [Au₁₂Ag₃₂(SPhCl₂)₃₀]^4-. Besides, the overall construction of Au₁₆Ag₄₃ or Au₁₂Ag₃₂ follows a complementing or overlapping assembly mode, respectively. Overall, the structural anatomy of Au₁₆Ag₄₃H₁₂(SPhCl₂)₃₄ sheds some new insight into the structural evolution of metal nanoclusters.

Two 6/10-connected Cu12S6 cluster-based organic frameworks: crystal structure and proton conduction

Nowadays, although the exploration of proton conductive materials has ranged from traditional sulfonated polymers to novel crystalline solid materials such as MOFs, COFs, and HOFs, research on crystalline cluster-based organic framework materials is very limited. Here, a pair of homologues Cu(i)-based organic framework containing a Cu12S6 cluster, [Cu12(MES)6(H2O)3]n (1) and {[Cu12(MPS)6(H2O)4]·6H2O}n (2) (H2MES = 2-mercaptoethanesulfonate acid and H2MPS = 2-mercaptoethanesulfonate acid), were hydrothermally synthesized under the same conditions and fully investigated for their proton conduction. Their structures were characterized by means of single-crystal X-ray diffraction, elemental analysis, thermogravimetric analyses, and PXRD measurements. The two MOFs show significant structural differences in the topological fashions. MOF 1 has a three-dimensional network and can be simplified into two topology types: a 10-connected gpu structure with a Schläfli symbol (312·426·57) and a 3,12-connected new topology with a point symbol {3·42}2{310·418·519·614·74·9}. MOF 2 also has a three-dimensional framework and topology as a 6-connected pcu primitive cubic network with a Schläfli symbol {412·63}. The two MOFs show different proton conduction parameters, but both indicate temperature-dependent proton conductive features. Intriguingly, the two MOFs exhibit high water stability and their proton conductivities are 3.63 × 10-5 and 2.75 × 10-5 S cm-1 under 333 K and 98% RH, respectively. The suggested mechanism for the synthesis for 1 and 2, and their proton conductivity performance comparison has been discussed in detail. In addition, Hirshfeld surface and fingerprint analysis on the two MOFs were computed to compare contacts between the molecules, which is essential for analyzing the relationships between their hydrogen bonds and proton conductivity properties.

Precise Implantation of an Archimedean Ag@Cu12 Cuboctahedron into a Platonic Cu4Bis(diphenylphosphino)hexane6 Tetrahedron

Precision loading of nanoclusters in confined spaces, which has been enthusiastically pursued in the scientific realm, is still associated with some mysteries of "how", "when", and "why". Here, we isolated two similar heterometallic cluster-in-cage compounds, [Ag@Cu₁₂S₈@Cu₄(dpph)₆]X (X = OH, SD/AgCu16a and X = PF₆, SD/AgCu16b; SD = SunDi), by use of an antigalvanic reaction between organometallic [PhC≡CCu]_n and Ph₃CSH with elemental silver. Both compounds are formed by fitting an Archimedean Ag@Cu₁₂ cuboctahedral cluster into a Platonic Cu₄(dpph)₆ tetrahedral cage [dpph = bis(diphenylphosphino)hexane]. The Ag@Cu₁₂ cluster is a hollow cuboctahedral Cu₁₂ cage filled with a central Ag^I atom, and all eight triangular faces of the Ag@Cu₁₂ cuboctahedron are triply capped by eight S^2- ions, four of which in a tetrahedral array further internally pillar four Cu vertices of the outer Cu₄(dpph)₆ tetrahedron, fixing the cluster in the cage. Both compounds can be deemed as molecular fragments excised from porous nanomaterials filled with discrete nanoclusters, thus providing more details for understanding the confined growth of atomically precise nanoclusters. Electrospray ionization mass spectrometry (ESI-MS) reveals that the AgCu₁₆ cluster is quite stable in CH₂Cl₂ and can stepwise lose dpph ligand in the gas phase under increased collision energy. This work not only presents a precise aggregation of metal atoms in a confined cavity to form a cluster-in-cage compound but also provides deep insights into the binding and geometry matching between clusters and cages in one entity.

Cocrystallization-driven stabilization of metastable nanoclusters: a case study of Pd1Au9

The structural determination of metastable nanoclusters remains challenging, which impedes the in-depth understanding of their structural evolution. Herein, based on a case study of Pd1Au9, we present a "cocrystallization-driven stabilization" approach to stabilize the metastable nanocluster and then determine its atomically precise structure. The [Pd1Au9(TFPP)7Br2]+ nanocluster is unstable in solution and would spontaneously convert to Pd2Au23(TFPP)10Br7. The introduction of Au11(TFPP)7Br3 nanocluster to the crystallization process of [Pd1Au9(TFPP)7Br2]+ gives rise to the cocrystallized Pd1Au9(TFPP)6Br3@Au11(TFPP)7Br3, although the composition of Pd1Au9 changes from [Pd1Au9(TFPP)7Br2]+ to Pd1Au9(TFPP)6Br3 among this cocrystallization. With this approach, the overall structure of the metastable Pd1Au9 has been determined. Owing to the very similar cluster size and surface ligand environment between Au11 and Pd1Au9, the obtained Pd1Au9@Au11 cocrystal exhibits almost the same cell parameters as those of the single crystalized Au11. Overall, the proposed "cocrystallization-driven stabilization" approach hopefully sheds light on the structural determination of more metastable nanoclusters.

Ag48 and Ag50 Nanoclusters: Toward Active-Site Tailoring of Nanocluster Surface Structures

The determination of active sites in metal nanoclusters is of great significance for the in-depth understanding of the structural evolution and the mechanism of physicochemical properties. In this work, the surface active Ag₂(SR)₃ units of the Ag₄₈Cl₁₄(S-Adm)₃₀ nanocluster are determined, and the active-site tailoring of this nanocluster gives rise to two derivative nanoclusters, i.e., the structure-maintained Ag₄₈Cl₁₄(S-Adm)₂₆(S-c-C₆H₁₁)₄ and the structure-growth Ag₅₀Cl₁₆(S-Adm)₂₈(DPPP)₂. Both Ag₄₈ and Ag₅₀ nanoclusters exhibit almost the same cluster framework, but the Ag₂(S-Adm)₃ active units are regulated to Ag₃(S-Adm)₂(DPPP)₁Cl₁ with the transformation from Ag₄₈ to Ag₅₀. The surface active sites on Ag₄₈ are rationalized by analyzing its crystal structure and the ligand-exchange-induced cluster transformation. This study provides some inspiration toward the active-site tailoring of nanocluster surface structures, which is significant for the preparation of new cluster-based nanomaterials with customized structures and enhanced performance.

Thermochromism and piezochromism of an atomically precise high-nuclearity silver sulfide nanocluster

A novel high-nuclearity silver sulfide nanocluster [Ag₅₀S₇(SC₆H₄F)₃₆(dppp)₆]·4DMI, (hereafter abbreviated as 1⋅4DMI) was synthesised. Solvent-free crystals of 1 displayed a completely reversible narrowing and broadening of the optical band gap that was accompanied by visual thermochromism and piezochromism changeovers, when stimulated by varying temperatures between 113 and 413 K or by changing the pressure from 1 atm to 7.5 GPa.

Stable supercapacitor electrode based on two-dimensional high nucleus silver nano-clusters as a green energy source

Atomically precise silver nanoclusters (Ag-NCs) are known as a hot research area owing to their brilliant features and they have attracted an immense amount of research attention over the last year. There is a lack of sufficient understanding about the Ag-NC synthesis mechanisms that result in optimal silver nanoclusters with an appropriate size, shape, and morphology. In addition, the coexisting flexible coordination of silver ions, the argentophilic interactions, and coordination bonds result in a high level of sophistication in the self-assembly process. Furthermore, the expansion of clusters by the organic ligand to form a high dimensional structure could be very interesting and useful for novel applications in particular. In this study, a novel two-dimensional 14-nucleus silver poly-cluster was designed and synthesized by the combination of two synthetic methods. The high nucleus silver cluster units are connected together via tetradecafluoroazelaic acid (CF₂) and this leads to the high stability of the polymer. This highly stable conductive poly-cluster, with bridging groups of difluoromethylene, displays a high energy density (372 F g^-1 at 4.5 A g^-1), excellent cycling stability, and great capacity. This nanocluster shows a high power density and long cycle life over 6000 cycles (95%) and can also tolerate a wide range of scan rates (5 mV s^-1 to 1 V s^-1), meaning it could act as a green energy source.

Multi-Nuclear Rare-Earth-Implanted Tartaric Acid-Functionalized Selenotungstates and Their Fluorescent and Magnetic Properties

A family of multinuclear rare-earth (RE)-implanted H₂tart^2--functionalized selenotungstates (STs) [H₂N(CH₃)₂]₁₃H{[W₂O₅(OH)₂(H₂tart)₂](H₂tart){[W₃O₆RE₂(H₂O)₆][SeW₉O₃₃]₂}₂}·31H₂O [RE = Eu³⁺ (1), Tb³⁺ (2), Dy³⁺ (3), Ho³⁺ (4), Y³⁺ (5); H₄tart = d-tartaric acid] have been afforded by a simple one-pot aqueous reaction and were structurally characterized. Intriguingly, their isomorphous organic-inorganic hybrid anion {[W₂O₅(OH)₂(H₂tart)₂](H₂tart){[W₃O₆RE₂(H₂O)₆][SeW₉O₃₃]₂}₂}^14- includes two sandwich-type {[W₃O₆[RE₂(H₂O)₆][SeW₉O₃₃]₂}^4- dimeric units with a W-O-RE heterometal core, which are further joined by two H₂tart^2--decorated dinuclear tungsten-oxo {W₂O₅(OH)₂(H₂tart)₂} clusters and a bridging H₂tart^2- ligand, contributing to a surprising Mobius band-like configuration. It is worth emphasizing that three H₂tart^2- ligands coordinate with tungsten centers rather than RE cations. For all we know, 1-5 delegate the infrequent RE-implanted STs functionalized by triplicate H₂tart^2- bridges. Furthermore, fluorescent performances of 1-4 as well as magnetic properties of 2-4 have been surveyed. The solid-state fluorescence emission spectra prove that each of them undoubtedly shows the characteristic emission peaks of RE cores, while alternating-current susceptibility measurements suggest field-induced single-molecule magnetic behavior in 3.

Halogenation Regulates Supramolecular Chirality at Hierarchical Levels of Self-Assembled N-Terminal Aromatic Amino Acids

Halogenation brings about dramatic variations to the performance of self-assembled organic species, such as luminescence and crystallinity, but it has seldom been utilized for chirality control. Here we show the halogenation effect of self-assembling organic building units on supramolecular chirality and chiroptical responses. N-terminal aromatic amino acids with different substituted halogen atoms at p-phenylalanine residues self-assembled into one-dimensional fibrous structures. Halogenation induced the emergence of macroscopic chirality regardless of halogen properties like electronegativity, generating exclusive homochiral helical structures. Solid-state X-ray structures and time-dependent density functional theory were utilized for calculated electronic circular dichroism spectra, which evidenced the diverse driving forces to enable chiral molecular arrangements, including H-bonds and halogen bonds. Red-shifted luminescence was observed in brominated building units, giving rise to active circularly polarized luminescence. This work elucidates the multiple roles of halogen in chiral self-assembly systems, which provides insight into the rational control over supramolecular chirality and their chiroptical applications.

Novel silver(i) cluster-based coordination polymers as efficient luminescent thermometers

Two original Ag-based clusters with a multidentate N-containing organic linker have been constructed featuring temperature-dependent luminescence behavior.

A comparative study of [Ag11(iPrS)9(dppb)3]2+ and [Ag15S(sBuS)12(dppb)3]+: templating effect on structure and photoluminescence

Atomically precise silver clusters with tunable photoluminescence (PL) properties have attracted extensive attention due to their great value for basic science and future applications. Here, we report that the addition of a sulfido template into a triangular thiolated silver cluster [Ag11(iPrS)9(dppb)3]·2CF3SO3·CH3OH (Ag11, dppb = 1,4-bis(diphenylphosphino)butane), which is emissive at 660 nm under ambient conditions, produced another silver cluster [S@Ag15(sBuS)12(dppb)3]·CF3SO3·H2O (Ag15) that displays 716 nm emission with a 56 nm redshift aided by the ligand sec-butyl mercaptan. The sulfido template, which affects the geometrical and electronic structures, results in a redshift of Ag11 room-temperature PL as a result of opening up the template-to-metal charge transfer (TMCT) and disturbing the electronic transition between the metal core and ligands at the periphery.

Structural determination of a metastable Ag27 nanocluster and its transformations into Ag8 and Ag29 nanoclusters

The atomically precise structure of a metastable nanocluster, Ag27H11(SPhMe2)12(DPPM)6, was determined, and its transformations into size-reduction Ag8 and size-growth Ag29 nanoclusters have been mapped out.

Assembly of {Co14} nanoclusters from adenine-modified Co4-thiacalix[4]arene units

An adenine-modified Co₄-thiacalix[4]arene unit can serve as a second building unit for fabrication of three Co₁₄ clusters with different structures.