Superatomic Clusters Research Articles

Strong ferroelectricity in one-dimensional materials self-assembled by superatomic metal halide clusters

Strong ferroelectricity in one-dimensional materials self-assembled by superatomic metal halide clusters

Superatomic Layer of Cubic Mo4S4 Clusters Connected by Cl Cross-Linking.

Superatomic clusters - assemblies of atoms with various sizes, shapes, and compositions - can form hierarchical architectures that exhibit emergent electronic properties not found in their individual units. In particular, cubic M4X4 clusters of chalcogenides (M = transition metal; X = chalcogen) are recognized as versatile building blocks for 3D structures with tunable morphologies and electronic properties. However, tetrahedral M4X4 clusters rarely assemble into 2D architectures, which could offer a distinct class of functional materials from their 3D analogues. Here, this work reports the preparation of 2D Mo8S8Cl11, a superatomic layer with a sandwich structure consisting of Mo4S4 clusters interconnected through Cl cross-linking. The vapor-phase reaction inside nanotubes promotes the selective growth of Mo8S8Cl11 nanoribbons, allowing detailed characterization via transmission electron microscopy. This methodology can be applied to the growth of layered structures containing Mo8S8Cl11 at the micrometer scale. This work has demonstrated that mono- and few-layer Mo8S8Cl11 can be prepared by exfoliation of parent solids. Electronic structure calculations indicate that the 2D monolayer has quasi-flat bands, giving rise to an indirect-to-direct bandgap transition under mechanical strain. Furthermore, scanning electrochemical microscopy reveals the potential of the layered structures as highly efficient catalysts for the hydrogen-evolution reaction.

Group superatoms: A new concept in cluster science

A promising research area in nanomaterials is the use of superatomic clusters as building blocks for creating novel molecules or materials with tailored properties. However, assembling these superatoms into functional materials is challenging, and a thorough understanding of this process is still lacking. In this study, we introduce a new concept called the “superatomic family,” which refers to superatoms that share similar valence electron structures but differ in size. We demonstrate this concept with the synthesized [Au6{Ni3(CO)6}4]2− cluster and the designed [Au16{Ni6(CO)10}4]2− and [Au31{Ni10(CO)15}4]5− clusters. These serve as analogs to simple hydrocarbons, such as methane (CH4), silicon hydride (SiH4), and germanium hydride (GeH4). In these supermolecular structures, the central cores of Au6, Au16, and Au31 exhibit the formation of superatomic SP3 hybridized orbitals, which influence the molecular shape and bonding. Moreover, we explored superatomic bonding involving SP3–SP3 hybridized cores, representing a single superatomic bond between members of the superatomic family, analogous to CH3–SiH3 bonds. By integrating the concept of group superatoms into the Lewis structure framework, we present a powerful approach for predicting and engineering cluster properties, thus opening a vast landscape of nanomaterial design possibilities.

Filling the gaps in icosahedral superatomic metal clusters.

Chemically modified superatoms have emerged as promising candidates in the new periodic table, in which Au13 and its doped M n Au13- n have been widely studied. However, their important counterpart, Ag13 artificial element, has not yet been synthesized. In this work, we report the synthesis of Ag13 nanoclusters using strong chelating ability and rigid ligands, that fills the gaps in the icosahedral superatomic metal clusters. After further doping Ag13 template with different degrees of Au atoms, we gained insight into the evolution of their optical properties. Theoretical calculations show that the kernel metal doping can modulate the transition of the excited-state electronic structure, and the electron transfer process changes from local excitation (LE) to charge transfer (CT) to LE. This study not only enriches the families of artificial superatoms, but also contributes to the understanding of the electronic states of superatomic clusters.

Ba4@Sn56]36- as a Main-Group Second-Order Superatom. Interpenetrated Dodecahedrons as a Three-Dimensional Cluster-of-Clusters Structure.

Superatomic clusters are relevant species to further understanding of bonding and structural properties of atomically precise molecular nanoparticles. Here, we explore the characteristics of ligand-free [Ba4@Sn56]36- Zintl-ion, as a three-dimensional aggregate of clusters featuring four fused Ba@Sn19 building units as an extension of the understanding in linear and cyclic superatomic cluster arrays. We provide a rational picture of the electronic shell in [Ba4@Sn56]36- as a cluster-of-clusters motif through the recently introduced second-order superatom approach, as a three-dimensional aggregation of superatomic clusters where their shells are able to interact. The electronic structure features both tangential and radial shells from the four building Ba@Sn19 units, leading to a set of 1S'21P'61D'101F'14 and higher angular momentum shells and a second set of 2S'22P'62D'102F'142G'8 second-order shells. Thus, the current approach serves to encourage the rationalization of molecular materials conceived from cluster building blocks toward a rational guide for synthetic efforts.

Anion Photoelectron Spectroscopy and Quantum Chemistry Calculations of Gas-Phase TaSi17̅ and TaSi18̅ Clusters: Structural Determination, Bonding Characteristics, and Multiplicity of Structural Forms.

This study explores the structures and chemical bonding properties of TaSi17̅ and TaSi18̅ clusters by employing anion photoelectron spectroscopy and theoretical computations. Utilizing CALYPSO and ABCluster programs for initial structure prediction, B3LYP hybrid functional for optimization, and CCSD(T)/def2-TZVPPD level for energy calculations, the research identifies the most stable isomers of these clusters. Key findings include the identification of two coexisting low-energy isomers for TaSi17̅, exhibiting Ta-endohedral fullerene-like cage structures, and the lowest-energy structures of TaSi17̅ and TaSi18̅ anions can be considered as derived from the TaSi16̅ superatom cluster. The study enhances the understanding of group 14 element chemistry and guides the design of novel inorganic metallic compounds, potentially impacting materials science.

Assignment of individual structures from intermetalloid nickel gallium cluster ensembles

Poorly selective mixed-metal cluster synthesis and separation yield reaction solutions of inseparable intermetalloid cluster mixtures, which are often discarded. High-resolution mass spectrometry, however, can provide precise compositional data of such product mixtures. Structure assignments can be achieved by advanced computational screening and consideration of the complete structural space. Here, we experimentally verify structure and composition of a whole cluster ensemble by combining a set of spectroscopic techniques. Our study case are the very similar nickel/gallium clusters of M12, M13 and M14 core composition Ni6+xGa6+y (x + y ≤ 2). The rationalization of structure, bonding and reactivity is built upon the organometallic superatom cluster [Ni6Ga6](Cp*)6 = [Ga6](NiCp*)6 (1; Cp* = C5Me5). The structural conclusions are validated by reactivity tests using carbon monoxide, which selectively binds to Ni sites, whereas (triisopropylsilyl)acetylene selectively binds to Ga sites.

Chemical properties of superatomic Li3O clusters from a density functional theory perspective: formation of chloride and adsorption behavior on graphynes.

Superatomic clusters have received a lot of attention due to their ability to mimic the electronic configurations of individual atoms. Despite numerous studies of these clusters, their ability to mimic the chemical properties of individual atoms is still unclear. This also applies for Li3O/Li3O+ clusters which simulate the Na atom and its ion, but their capabilities to form a salt or be adsorbed on surfaces remain unexplored. In this work, a density functional theory investigation was performed to study the chemical formation and adsorption behavior of the superatomic Li3O cluster. The results show that Li3O mimics the chemical properties of the sodium element to form Li3O chloride and be adsorbed on graphdiyne and γ-graphyne with similar binding energy as the sodium adsorbate cases. Beyond the isolated cluster individuals, superatoms are demonstrated as elements from the 3D periodic table to construct compounds and attach onto solid surfaces.

Tuning the electronic structure of gold cluster-assembled materials by altering organophosphine ligands.

Superatomic clusters can be assembled to build bulk matter, where the individual characteristics are preserved. The main benefit of these materials over conventional bulk species is the capability to tailor their features by altering the physicochemical identities of individual clusters. Electronic properties of metal clusters can be modified by a protective shell of ligands that attach to the surface and make the whole nanoparticle soluble in organic or aqueous solvents. In the present work, we demonstrate that properly chosen ligands provide not only steric protection from aggregation but also tune the redox activity of metal clusters. We investigate the role of the ligands in electronic structure tunability and ligand-field splitting. Our first-principles calculations agree with the experiments, showing that phosphine-protected gold materials are small gap semiconductors. The obtained bandgaps strongly depend on the ligand used. Hence, using phosphine and organophosphine ligands should be feasible and promising while designing the novel superatom-based materials since the desired range of the bandgap might be achieved (by the proper choice of the ligand).

Atomically precise alkynyl-protected Ag19Cu2 nanoclusters: synthesis, structure analysis, and electrocatalytic CO2 reduction application.

We report the synthesis, structure analysis, and electrocatalytic CO2 reduction application of Ag19Cu2(CCArF)12(PPh3)6Cl6 (abbreviated as Ag19Cu2, CCArF: 3,5-bis(trifluoromethyl)phenylacetylene) nanoclusters. Ag19Cu2 has characteristic absorbance features and is a superatomic cluster with 2 free valence electrons. Single-crystal X-ray diffraction (SC-XRD) revealed that the metal core of Ag19Cu2 is composed of an Ag11Cu2 icosahedron connected by two Ag4 tetrahedra at the two terminals of the Cu-Ag-Cu axis. Notably, Ag19Cu2 exhibited excellent catalytic performance in the electrochemical CO2 reduction reaction (eCO2RR), manifested by a high CO faradaic efficiency of 95.26% and a large CO current density of 257.2 mA cm-2 at -1.3 V. In addition. Ag19Cu2 showed robust long-term stability, with no significant drop in current density and FECO after 14 h of continuous operation. Density functional theory (DFT) calculations disclosed that the high selectivity of Ag19Cu2 for CO in the eCO2RR process is due to the shedding of the -CCArF ligand from the Ag atom at the very center of the Ag4 unit, exposing the active site. This study enriches the potpourri of alkynyl-protected bimetallic nanoclusters and also highlights the great advantages of using atomically precise metal nanoclusters to probe the atomic-level structure-performance relationship in the catalytic field.

"Sergeants-and-soldiers" principle in the synthesis of intrinsically chiral Au13 clusters.

Surface ligand modification on atomically precise metal clusters is one of the important strategies not only to stabilize monodisperse clusters, but also to derive unique optical and electronic properties. The chiral coordination of surface ligands on clusters controls the global chirality in clusters giving rise to unambiguous optical activity including circular dichroism (CD) and circularly polarized luminescence (CPL). Stereoselective synthesis of intrinsically chiral clusters has been achieved by the use of chiral ligands stabilizing one-handed clusters selectively. Herein, we investigate the effect of chiral ligand coordination on the deracemization of intrinsically chiral Au13 superatom clusters. The mixture of achiral bis(diphenylphosphino)ethane (DPPE) and chiral (R,R)-1,2-bis[(2-methoxyphenyl)phenylphosphino]ethane (R-DIPAMP) led to the formation of a mixture of [Au13(R-DIPAMP)x(DPPE)5-xCl2]3+ clusters with varied x-values (x = 0-5). Reverse phase HPLC successfully fractionalized the mixture into solutions composed of single component Au13 clusters depending on the x-values. The separated Au13 clusters afforded similar optical activity to that of [Au13(R-DIPAMP)5Cl2]3+ in the CD study regardless of x-values (x = 1-4). The DFT calculation supports that the coordination of a single DIPAM ligand is enough to bias the twisting direction in the Au13 superatom with dictating the tortional orientation of other four DPPE ligands. The emergence of the "sergeants-and-soldiers principle", wherein a small number of chiral ligands determine the chiral orientation of other achiral ligands, is thus demonstrated in the synthesis of intrinsically chiral Au13 clusters.

Synthesis and crystallization of a carboxylate functionalized N-heterocyclic carbene-based Au13 cluster with strong photo-luminescence.

Here we report the synthesis and crystallization of a -COOH-capped N-heterocyclic carbene (NHC)-protected Au13 cluster. The single-crystal structure of the -COOH-capped NHC-Au13 cluster reveals a classic icosahedral core with one Au atom in its center. The icosahedral core is surrounded by five NHC ligands with pseudo C5 symmetry and exposed carboxyls in a pentagonal antiprism fashion. The detailed formula of the Au cluster was identified as Au13(bi-NHC carboxyl)5Cl2 (hereafter abbreviated as Au13-c). The density functional theory (DFT) calculations confirm that Au13-c is an electronically stable eight-electron super-atom cluster and elucidate its optical transitions in the UV-Vis range. The Au13-c cluster exhibits excellent thermal and chemical stability under bio-relevant conditions. Additionally, this cluster shows a strong red emission in DMF and H2O with an excellent quantum yield (QY) of 40% and 12.6%, respectively. The high QY of Au13-c enables its use in cell imaging on both cancer and noncancerous cells.

Superatomic Ag58 nanoclusters incorporating a [MS4@Ag12]2+ (M = Mo or W) kernel show aggregation-induced emission

In core-shell silver nanoclusters, the control of core structure presents a more formidable challenge compared to that of the shell structure. Here, we report the successful synthesis and characterization of four distinct silver thiolate nanoclusters [MS4@Ag12@Ag46S24(dppb)12] (M = Mo or W), each incorporating a cup-like [MS4@Ag12]2+ kernel. These nanoclusters were meticulously prepared using (NH4)2MoS4 or (NH4)2WS4 as both a template and a controlled source of S2− ions. Remarkably, we have observed a unique configuration within these eight-electron superatomic Ag58 nanoclusters, where the zero-valent Ag atoms reside exclusively within the inner [MS4@Ag12]2+ kernel. This stands in contrast to other superatomic clusters possessing an Ag(0) core. Notably, the introduction of phenyl-containing compounds during the synthesis process induced a transformation in the space group symmetry from C2/c to I4¯. This transformative effect was found to originate from the interplay between adjacent 1,4-bis(diphenylphosphino)butane (dppb) ligands, which facilitated enhanced emission through aggregation-induced intermolecular interactions, specifically C−H···π interactions. Collectively, our findings contribute substantively to the understanding of the intricate relationship between nanocluster structures and their corresponding properties, shedding light on the crucial roles played by templates and diphosphine ligands in this context.

Chiral Hydride Cu18 Clusters Transform to Superatomic Cu15Ag4 Clusters: Circularly Polarized Luminescence Lighting.

The manipulation of metal cluster enantiomers and their reconstruction remain challenging. Here, for the first time, we report an enantiomeric pair of hydride copper clusters [Cu18H(R/S-PEA)12](BF4)5 (R/S-Cu18H) made using designed chiral ligands. By manipulation of R/S-Cu18H with Ag+ ions, H- ions are released, leading to the reconstruction of 15 Cu atoms. Moreover, 4 Ag atoms replaced Cu atoms at the specific sites, resulting in the formation of homochiral [Cu15Ag4(R/S-PEA)12](BF4)5 (R/S-Cu15Ag4) with an isomorphic metal skeleton. This process was accompanied by a reduction reaction generating two free valence elections in the chiral alloying counterparts, which displayed orange emission. The solid-state R/S-Cu15Ag4 exhibited a photoluminescence quantum yield of 7.02% and excellent circularly polarized luminescence. The chiral transformations were resolved by single-crystal X-ray diffraction. The development of chiral copper hydride precursor-based metal clusters with chiroptical activities holds tremendous promise for advancing the field of optoelectronics and enabling new applications in lighting, displays, and beyond.

Exploring hydrogen adsorption on nanocluster systems: Insights from DFT calculations of Au[formula omitted] ([formula omitted] = Sc-Ni)

The superatomic cluster Au102+ is the smallest known replica of the golden pyramid Au20, and its complex analogues, Au9M2+ (M = Sc-Ni), have exhibited stable and intriguing electronic properties. In this study, we employ density-functional theory (DFT) to investigate the interaction between hydrogen molecules and Au9M2+ clusters. Our DFT calculations reveal that the structures of these clusters are influenced by the dissociative adsorption of H2, but not by the molecular adsorption. By conducting a comprehensive analysis, we show that the preferred adsorption configuration is a result of the competition between various factors, including the surface/encapsulated position, relative electronegativity, and coordination number of atoms. Although Au9M2+-2H (M = Sc, Ti, Mn, and Fe) are remarkably more stable than their corresponding Au9M2+-H2 configurations, different activation energies ranging from 0.15 to 0.99 eV are required during the dissociative reaction pathway. The finding results shed light on the mechanisms underlying the preferred adsorption site of hydrogen on the studied species and provide insights into adsorption kinetics that can aid further theoretical and experimental studies of hydrogenation in nanostructured materials.

Motif-to-Core Nucleation in a Decahedral Evolution Pattern.

The atomic precision of ultrasmall metal nanoclusters has opened the door to elucidating the structural evolution principles of metal nanomaterials at the molecular level. Here, we report a novel set of super-atomic Ag clusters, including [Ag19(TBBT)16(DPPP)4]+ (Ag19), [Ag22(DMAT)8(DPPM)4Cl8]2+ (Ag22), Ag26(SPh3,5-CF3)15(DPPF)4Cl5 (Ag26), and [Ag30(DMAT)12(DPPP)4Cl8]2+ (Ag30). The core structures of these clusters correspond to one decahedral Ag7, perpendicular bi-decahedrons, three-dimensional penta-decahedrons, and hexa-decahedrons, respectively. The Ag atoms in AgS2 blocks show a strong correlation with the decahedral cores: the five equatorial Ag atoms in the decahedral Ag7 core of Ag19 all adopt the AgS2 coordination, while the Ag atoms in AgS2 blocks of Ag22, Ag26, and Ag30 unexceptionally constitute additional decahedral structures with the core Ag atoms. Specifically, two and four core Ag atoms of Ag26 and Ag30 clusters occupy positions that highly resemble that of Ag (in AgS2 motifs) of Ag22. The strong structural correlation demonstrates the motif-to-core evolution of the surface Ag (on AgS2) to build extra-decahedral blocks. Density functional theory calculations indicate that the 2e, 4e, 6e, and 8e clusters (from Ag19 to Ag30) adopt 1S2, 1S21P2, 1S21P4, and 1S21P6 electron configurations, all of which feature excellent super-atomic characters.

Alkynyl-protected Ag20 Rh2 Nanocluster with Atomic Precision: Structure Analysis and Tri-functionality Catalytic Application.

We report the overall structure and trifunctionality catalytic application of an atomically precise alloy nanocluster of Ag20 Rh2 (C≡C-t Bu)16 (CF3 CO2 )6 (H2 O)2 (abbreviated as Ag20 Rh2 hereafter). Ag20 Rh2 has a twisted rod-like structure, where a Ag4 @Rh2 kernel is connected by two twisted Ag8 cubes on two sides. Ag20 Rh2 is a superatomic cluster with four free valence electrons, and it has characteristic absorbance feature. Interestingly, Ag20 Rh2 exhibited superior catalytic performance than the larger AgRh nanoparticle counterparts in electrochemical hydrogen evolution reaction (HER), reduction of 4-nitrophenol, and the methyl orange degradation reaction. Such intriguing catalytic properties are attributed to the more exposed active sites from the ultrasmall nanoclusters than relatively large nanoparticles. This study not only enriches the family member of alkynyl-protected AgRh nanoclusters with atomic precision, but also highlights the great advantages of employing nanoclusters as efficient catalysts for multiple functionalities.

Elucidating the Structures of Intermediate Fragments during Stepwise Dissociation of Monolayer-Protected Silver Clusters.

Fragmentation dynamics of ligated coinage metal clusters reflects their structural and bonding properties. So far methodological challenges limited probing structures of the fragments. Herein, we resolve the geometric structures of the primary fragments of [Ag29 L12 ]3- , i.e. [Ag24 L9 ]2- , [Ag19 L6 ]- and [Ag5 L3 ]- (L is 1,3-benzene dithiolate). For this, we used trapped ion mobility mass spectrometry to determine collision cross sections of the fragments and compared them to structures calculated by density functional theory. We also report that following two sequential [Ag5 L3 ]- elimination steps, further dissociation of [Ag19 L6 ]- also involves a new channel of Ag2 loss and Ag-S and C-S bond cleavages. This reflects a competition between retaining the electronic stability of 8 e- superatom cluster cores and increasing steric strain of ligands and staples. These results are also of potential interest for future soft-landing deposition studies aimed at probing catalytic behavior of Ag clusters on supports.

Elucidating the Structures of Intermediate Fragments during Stepwise Dissociation of Monolayer‐Protected Silver Clusters

AbstractFragmentation dynamics of ligated coinage metal clusters reflects their structural and bonding properties. So far methodological challenges limited probing structures of the fragments. Herein, we resolve the geometric structures of the primary fragments of [Ag29L12]3−, i.e. [Ag24L9]2−, [Ag19L6]− and [Ag5L3]− (L is 1,3‐benzene dithiolate). For this, we used trapped ion mobility mass spectrometry to determine collision cross sections of the fragments and compared them to structures calculated by density functional theory. We also report that following two sequential [Ag5L3]− elimination steps, further dissociation of [Ag19L6]− also involves a new channel of Ag2 loss and Ag−S and C−S bond cleavages. This reflects a competition between retaining the electronic stability of 8 e− superatom cluster cores and increasing steric strain of ligands and staples. These results are also of potential interest for future soft‐landing deposition studies aimed at probing catalytic behavior of Ag clusters on supports.

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

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