Bottom-up design and assembly with superatomic building blocks

Constructing specific structures from the bottom up with artificial units is an important interdisciplinary topic involving physics,chemistry,materials,and so on.In this work,we theoretically demonstrated the feasibility of using superatoms as building blocks to assemble a complex at atomic-level precision.By using a series of actinide-based endohedral metallofullerene(EMF)superatoms that can form one,two,three and four chemical bonds,a planar complex with intra-and inter-molecular interactions was assembled on the Au(111)surface.This complex is composed of two parts,containing ten and eight superatoms,respectively.The electronic structure analysis shows that the electron density inside each part is connected and the closed-shell electronic arrangement system is designed.There is also an obvious van der Waals boundary by physical adsorption between the two parts,and a stable complex is formed.Since this complex is realized by the first-principles calculations of quantum mechanics,our results help not only achieve atomic-level precision construction with artificial superatomic units but also maintain atomic-level functional properties.

How ligand coordination and superatomic-states accommodate the structure and property of a metal cluster:Cu_(4)(dppy)_(4)Cl_(2)vs.Cu_(21)(dppy)_(10)with altered photoluminescence

We have synthesized two copper nanoclusters(NCs)with a protection of the same ligand diphenylphosphino-2-pyridine(C_(17)H_(14)NP,dppy for short),formulated as Cu_(4)(dppy)_(4)Cl_(2)and Cu21(dppy)10,respectively.The former one bears a distorted tetrahedron Cu4 core with its six edges fully protected by chlorine and dppy ligands,while the latter presents a symmetric Cu_(21)core on which ten dppy molecules function as monolayer protection via well-organized monodentate or bidentate coordination.Interestingly,the Cu_(4)(dppy)_(4)Cl_(2)cluster exhibits a strong yellow emission at∼577 nm,while Cu_(21)(dppy)_(10)displays dual emissions in purple(∼368 nm)and green(∼516 nm)regions respectively.In combination with TD-DFT calculations,we demonstrate the origin of altered emissions and unique stability of the two copper nanoclusters pertaining to the ligand coordination and metallic superatomic states.

Designing topological and correlated 2D magnetic states via superatomic lattice constructions of zirconium dichloride

Magnetic materials could realize the intriguing quantum anomalous Hall effect and metal-to-insulator transition when combined with band topology or electronic correlation,which have broad prospects in quantum information,spintronics,and valleytronics.Here,we propose the approach of designing novel two-dimensional(2D)magnetic states via d-orbital-based superatomic lattices.Specifically,we chose triangular zirconium dichloride disks as superatoms to construct the honeycomb superatomic lattices.Using first-principles calculations,we identified a series of 2D magnetic states with varying sizes of superatoms.We found the non-uniform stoichiometries and geometric effect of superatomic lattice give rise to spin-polarized charges arranged in different magnetic configurations,containing ferromagnetic coloring triangles,antiferromagnetic honeycomb,and ferromagnetic kagome lattices.Attractively,these magnetic states are endowed with nontrivial band topology or strong correlation,forming an ideal Chern insulator or antiferromagnetic Dirac Mott insulator.Our work not only reveals the potential of d-orbital-based superatoms for generating unusual magnetic configurations,but also supplies a new avenue for material engineering at the nanoscale.

Organic ligand mediated evolution from superalkalis to superatomic molecules and nanowires

Superatoms are considered as promising building blocks for customizing superatomic molecules and cluster-assembly nanomaterials due to their tunable electronic structures and functionalities.Electron counting rules,which mainly adjust the shell-filling of clusters,are classical strategies in designing superatoms.Here,by employing the density functional theory(DFT)calculations,we proved that the 1,4-phenylene diisocyanide(CNC_(6)H_(4)NC)ligand could dramatically reduce the adiabatic ionization potentials(AlPs)of the aluminum-based clusters,which have 39,40,and 41 valence electrons,respectively,to give rise to superalkali species without changing their shell-filling.Moreover,the rigid structure of the ligand can be used as a bridge firmly linking the same or different aluminum-based clusters to form superatomic molecules and nanowires.In particular,the bridging process was observed to enhance their nonlinear optical(NLO)responses,which can be further promoted by the oriented external electric field(OEEF).Also,the stable cluster-assembly XAl_(12)(CNC_(6)H_(4)NC)(X=Al,C,and P)nanowires were constructed,which exhibit strong absorption in the visible light region.These findings not only suggest an effective ligand-field strategy in superatom design but also unveil the geometrical and electronic evolution from the CNC_(6)H_(4)NC-based superatoms to superatomic molecules and nanomaterials.

B_(111),B_(112),_(B113),and B_(114):The most stable core-shell borospherenes with an icosahedral B_(12) core at the center exhibiting superatomic behaviors

Boron allotropes are known to be predominately constructed by icosahedral B_(12) cages,while icosahedral-B_(12) stuffing proves to effectively improve the stability of fullerene-like boron nanoclusters in the size range between B_(98)–B_(102).However,the thermodynamically most stable core-shell borospherenes with a B_(12) icosahedron at the center still remains unknown.Based on the structural motif of D5h C_(70) and extensive first-principles theory calculations,we predict herein the high-symmetry C5v B111+(3)which satisfies the Wade’s n+1 and n+2 skeletal electron counting rules exactly and the approximately electron sufficient Cs B_(111)(4),Cs B_(112)(5),Cs B_(113)(6),and Cs B_(114)(7)which are the most stable neutral core-shell borospherenes with a B_(12) icosahedron at the center reported to date in the size range between B_(68)–B_(130),with Cs B112(5)being the thermodynamically most favorite species in the series.Detailed orbital and bonding analyses indicate that these spherically aromatic species all contain a negatively charged icosahedral B_(122)−core at the center which exhibits typical superatomic behaviors in the electronic configuration of 1S21P61D101F8,with its dangling valences saturated by twelve radial B-B 2c-2eσbonds between the B_(12) inner core and the B_(70) outer shell.The infrared(IR)and Raman spectra of the concerned species are computationally simulated to facilitate their future characterizations.

Ligand accommodation causes altered reactivity of silver clusters with iodomethane:superatomic stability of Ag_(9)I_(2)^(+)in mimicking XeF_(2)

Exploring metal cluster reactivity with alkyl halides enables to understand the related chemical mechanism of metal surfaces in terms of active sites.Here we report a study of Ag_(n)^(+)(n=1-27)clusters reacting with iodomethane by a flow tube apparatus in tandem with a customized triple quadrupole mass spectrometer.Strong even/odd alternation of the Ag_(n)^(+)is observed in their reactions with CH_(3)I,where silver clusters with even-number,Ag_(2n)^(+),find favorable products of Ag_(2n)I_(1,3)^(+)series,while the Ag_(2n−1)^(+)clusters form Ag_(2n−1)I_(2,4)^(+)products.Interestingly,Ag_(9)^(+)shows up with prominent mass abundance but allows for the formation of Ag_(9)I_(2)^(+),which finds an echo with the formation of Ag_(10)I_(3)^(+).We illustrate the enhanced stability of Ag_(9)I_(2)^(+)and Ag_(10)I_(3)^(+)by showing their significantly enlarged highest occupied molecular orbital(HOMO)-lowest unoccupied molecular orbital(LUMO)gaps and balanced charge distribution compared with the bare metal clusters,respectively.Also elucidated,is the superatomic nature of these bare and iodinated silver clusters,especially Ag_(9)I_(2)^(+)which mimics the rare-gas compound XeF_(2).This study expands a vivid example of special and general superatoms,and enriches the general knowledge on how a ligand stabilizes a metal cluster.

Evolution of all-carboxylate-protected superatomic Ag clusters confined in Ti-organic cages

In this study,the size of the titanium organic cage was controlled to achieve the restricted growth from a single Ag(I)atom(Ag@Ti_(5))to rare all-carboxylate-protected superatomic Ag cluster(Ag6@Ti_(6)).The classical octahedral Ag_(6)^(4+) cluster with two delocalized electrons(2e)has been encapsulated in a Ti6 organic cage,which shows high stability in air and dimethyformamide(DMF).Furthermore,larger 2e nested double-tetrahedra Ag clusters(Ag_(8)^(6+) and Ag_(9)^(7+))protected using a tetrahedral hollow metalloligand framework(Ag_(8)@Ti_(4) and Ag_(9)@Ti_(4))were obtained.Electrospray ionization mass spectrometry(ESI-MS)and density functional theory(DFT)calculations confirmed that there are two delocalized electrons on these small Ag clusters.This study provides a new form of protection for superatomic Ag clusters and provides a feasible strategy for the development of stable Ag clusters.

Superatomic Signature and Reactivity of Silver Clusters with Oxygen:Double Magic Ag_(17)^– with Geometric and Electronic Shell Closure

Understanding the stability and reactivity of silver clusters toward oxygen provides insights to design new materials of coinage metals with atomic precision.Herein,we report a systematic study on anionic silver clusters,Ag_(n)^(−)(n=10-34),by reacting them with O_(2) under multiple-collision conditions.Mass spectrometry observation presents the odd-even alternation effect on the reaction rates of these Agn−clusters.

Layer-by-layer alloying of NIR-Ⅱ emissive M50(Au/Ag/Cu)superatomic nanocluster

The intermetallic synergy plays a critical role in exploring the chemical-physical properties of metal nanoclusters.However,the controlled doping or layer-by-layer alloying of atom-precise metal nanoclusters(NCs)has long been a challenging pursuit.In this work,two novel alloy nanoclusters[PPh_(4)]_(4)[Ag_(32)Cu_(18)(PFBT)_(36)]((AgCu)_(50))and[PPh_(4)]_(4)[Au_(12)Ag_(20)Cu_(18)(PFBT)_(36)](Au_(12)(AgCu)_(38)),where PFBT is pentafluorobenzenethiolate,with shell-by-shell configuration of M_(12)@Ag_(20)@Cu_(18)(PFBT)_(36)(M=Ag/Au)were synthesized by a facile one-pot co-reduction method.Notably,a fingerprint library of[Ag_(50)−xCux(PFBT)_(36)]^(4−)(x=0 to 50)from Ag_(50)to Cu_(50)has been successfully established as revealed by electrospray ionization mass spectrometry.Single-crystal X-ray diffraction analysis of trimetallic Au_(12)(AgCu)_(38)confirmed the layer-by-layer alloying under reducing conditions.What is more,(AgCu)_(50)and Au12(AgCu)_(38)both show broad photoluminescence(PL)peak in the second near-infrared(NIR-II)window,and the Au doping in the innermost shell considerably enhances the photoluminescence intensity.This work not only offers an insight in the process of metal cluster alloying but also provides a platform to study the doping-directed PL properties in the multimetallic cluster system.

Effects of 5f-elements on electronic structures and spectroscopic properties of gold superatom model

5f-elements encaged in a gold superatomic cluster are capable of giving rise to unique optical properties due to their hyperactive valence electrons and great radial components of 5f/6d orbitals. Herein, we review our first-principles studies on electronic structures and spectroscopic properties of a series of actinide-embedded gold superatomic clusters with different dimensions. The three-dimensional（3D） and two-dimensional（2D） superatom clusters possess the 18-electron configuration of 1S21P61D10 and 10-electron configuration of 1S21P41D4, respectively. Importantly, their electronic absorption spectra can also be effectively explained by the superatom orbitals. Specifically, the charge transfer（CT） transitions involved in surface-enhance Raman spectroscopy（SERS） spectra for 3D and 2D structures are both from the filled 1D orbitals, providing the enhancement factors of the order of ～ 10^4 at 488 nm and ～ 10^5 at 456 nm, respectively. This work implies that the superatomic orbital transitions involved in 5f-elements can not only lead to a remarkable spectroscopic performance, but also a new direction for optical design in the future.

Solvent field regulated superhalogen in pure and doped gold cluster anions

Condensed-phase synthesis of atomically precise clusters has become a vital branch of cluster science,where solvents are indispensable in the synthesis process.Herein,by employing the density functional theory(DFT)calculations and molecular dynamics(MD)simulations,we demonstrated that polar solvents not only provide an important environment to stabilize clusters,but they can also dramatically alter the electronic property of cluster anions forming novel superhalogen anions.Such a regulation effect was first verified in small model gas-phase pure and doped gold cluster anions,which was further evidenced in a real experimentally synthesized Au18 nanocluster.Different solvation models reveal that the solvent field,which is a noninvasive methodology different from conventional electron-counting rules,can be considered as a novel external field to remarkably increase the electron-binding capability of cluster anions while maintaining their geometrical and electronic structures.Considering the indispensability and convenient availability of the solvents,present findings may boost the potential applications of superatoms in constructing super oxidizers in the condensed phase.

Actinide-embedded gold superatom models： Electronic structure, spectroscopic properties, and applications in surface-enhanced Raman scattering

Actinide elements encaged in a superatomic cluster can exhibit unique properties due to their hyperactive valence electrons. Herein, the electronic and spectroscopic properties of Th@Au14 are predicted and compared with that of the isoelectronic entities [Ac@Au14]- and [Pa@Au14]＋ using density functional theory. The calculation results indicate that these clusters all adopt a closed- shell superatomic 18-electron configuration of the 1S21p61D10 Jellium state. The absorption spectrum of Th@Au14 can be interpreted by the Jelliumatic orbital model. In addition, calculated spectra of pyridine-Th@Au14 complexes in the blue laser band exhibit strong peaks attributable to charge transfer （CT） from the metal to the pyridine molecule. These charge-transfer bands lead to a resonant surface-enhanced Raman scattering （SERS） enhancement of -104. This work suggests a basis for designing and synthesizing SERS substrate materials based on actinide-embedded gold superatom models.

Actinide endohedral boron clusters： A closed-shell electronic structure of U@B40

The distinctive electronic bonding properties of actinide-containing clusters have made them the subject of increased attention. Herein, we use density functional theory calculations to examine a unique actinide-encapsulated U@B40 cage structure, revealing that it exhibits a 32-electron （1S2P61Dl01FTM） closed-shell singlet configuration in which all s, p, d, and f shells of the U atom are filled. Furthermore, the binding energy of 8.22 eV calculated for this cluster implies considerable stability, and the simulated infrared and Raman spectra feature U-B40 stretching and pure B40 breathing vibration modes, respectively. These spectral characteristics may aid future experimental investigations. Thus, this work not only describes a new member of the superatomic family, but also provides a method of encapsulating radioactive actinides.

Spin accommodation and reactivity of nickel clusters with oxygen:Aromatic and magnetic metalloxocube Ni_(13)O_(8)^(±)

Due to challenges in preparing pure metal clusters and in controlling reactions,the oxides produced by metal clusters reacting with oxygen are often different from traditional ion-molecule products in the gas phase and their reactivity pattern is also largely unveiled yet.In this work,utilizing a customized Re-TOFMS having a home-made cluster source and a flow tube reactor,we have observed the gaseous reactions of Nin±clusters with oxygen and found magic clusters of Ni_(13)O_(8)±that dominate the mass distributions.By quantum chemistry calculations,we find that both Ni_(13)O_(8)−and Ni_(13)O_(8)+clusters bear a regular cubic structure with 8 oxygen anchoring the eight angles,however,they have rather different spin accommodations.The Ni_(13)O_(8)−clusters have 15 unpaired spin-up electrons exhibiting cubic aromaticity and decent ferromagnetism,while the Ni_(13)O_(8)+clusters take a lower-spin ground state(11 unpaired electrons),with spin-down population on the central Ni atom pertaining to ferrimagnetism.This is a class of metalloxocube clusters that hold properties of aromaticity and ferromagnetism/ferrimagnetism charcterized by a few spin electrons,which embodies the bonding nature of superatomic compounds and enables to develop cluster-genetic materials of multi-functionality.

Chlorine-passivated superatom Al37clusters for nonlinear optics

Utilizing a facile top-down synthetic procedure, here we report the finding of a chlorine-passivated Al_(37) superatom cluster. It is demonstrated that the presence of electrophilic groups, severing as protecting ligands, alters the valence electron count of the metallic core and stabilize the as-prepared aluminum clusters especially when even-numbered chlorine atoms are located at equilibrium positions. Following the discussion regarding their reasonable stabilities, we illustrate the feasible reaction pathways in forming such chlorine-passivated Al_(37) superatom clusters which bear delocalized superatomic orbitals with five valence 3P^5 electrons shifting to the chlorine ligands indicative of a closed electron shell 2F^(14) of the metal core. The successful synthesis of such chlorine-protected aluminum clusters evidences the compatibility of general theory of cluster chemistry in both gas phase and wet chemistry. Such simple-ligand-protected aluminum clusters exhibit reverse-saturated-absorption(RSA) nonlinear optical property pertaining to electronic transitions within the discrete energy states of cluster materials.

超原子组装诱导的从绝缘体到半导体性质转变:一个理论研究（英文）

硼基超原子通向功能材料的一个途径是组装.我们通过密度泛函理论研究了典型的硼基超原子B_(40)之间的相互作用.结果显示,在不同的低聚物中两个B_(40)之间不同的朝向方式会导致电子结构改变,但它们都部分保持了超原子性质.这是因为单体中靠内壳层的超原子轨道仍保持其在超原子中的电子局域性,而价壳层的超原子轨道由于超原子间成键或反键杂化而不能保持孤立超原子的轨道形状.在部分保持超原子性质的情况下, B_(40)超原子的组装可以相应实现从绝缘体到半导体的转变.带隙的减小是由"主量子数"为2的超原子轨道杂化成键导致的.我们的发现凸显了超原子间相互作用,会带来不同于单体的协同效应.因此,这一研究将有助于新型材料和器件的发展,尤其在以超原子为功能单元的组装材料研究方面将发挥积极作用.

Single-photon-level light storage with distributed Rydberg excitations in cold atoms

We present an improved version of the superatom(SA)model to examine the slow-light dynamics of a few-photons signal field in cold Rydberg atoms with van der Waals(vdW)interactions.A main feature of this version is that it promises consistent estimations on total Rydberg excitations based on dynamic equations of SAs or atoms.We consider two specific cases in which the incident signal field contains more photons with a smaller detuning or less photons with a larger detuning so as to realize the single-photon-level light storage.It is found that vdW interactions play a significant role even for the slow-light dynamics of a single-photon signal field as distributed Rydberg excitations are inevitable in the picture of dark-state polariton.Moreover,the stored(retrieved)signal field exhibits a clearly asymmetric(more symmetric)profile because its leading and trailing edges undergo different(identical)traveling journeys,and higher storage/retrieval efficiencies with well preserved profiles apply only to weaker and well detuned signal fields.These findings are crucial to understand the nontrivial interplay of single-photon-level light storage and distributed Rydberg excitations.

Direct assembly between closed-shell coinage metal superatoms

Bottom-up constructing all-metal functional materials is challenging,because the metal clusters are prone to lose their original structures during coalensence.In this work,we report that closed-shell coinage metal superatoms can achieve direct chemical bonding without losing their electronic properties.The reason is that the supermolecule formed by two superatoms has the same number of bonding and anti-bonding supermolecular orbitals,in which the bonding orbitals contribute to bonding and the antibonding orbitals with anti-phase orbitals delocalized over each monomer to maintain the individual geometric and electronic structural properties.Further analysis indicates the interactions between two superatoms are too weak to break the structure of monomers,which is confirmed by the first-principles molecular dynamics simulations.With these superatoms as the basic units,a series of robust one-dimensional and two-dimensional nanostructures are fabricated.Our findings provide a general strategy to take advantage of superatoms in regulating bonding compared to natural atoms,which paves the way for the bottom-up design of materials with collective properties.

Copper-hydride nanoclusters with enhanced stability by N- heterocyclic carbenes

Copper-hydrides have been intensively studied for a long time due to their utilization in a variety of technologically important chemical transformations.Nevertheless,poor stability of the species severely hinders its isolation,storage and operation,which is worse for nano-sized ones.We report here an unprecedented strategy to access to ultrastable copper-hydride nanoclusters(NCs),namely,using bidentate N-heterocyclic carbenes as stabilizing ligands in addition to thiolates.In this work,a simple synthetic protocol was developed to synthesize the first large copper-hydride nanoclusters(NCs)stabilized by N-heterocyclic carbenes(NHCs).The NC,with the formula of Cu3i(RS)25(NHC)3H6(NHC=1,4-bis(1-benzyl-1 H-benzimidazol-1-ium-3-yl)butane,RS=4-fluorothiophenol),was fully characterized by high resolution Fourier transform ion cyclotron resonance mass spectrum,nuclear magnetic resonance,ultra-violet visible spectroscopy,density functional theory(DFT)calculations and single-crystal X-ray crystallography.Structurally,the title cluster exhibits unprecedented Cu4 tetrahedron-based vertex-sharing(TBVS)superstructure(fusion of six Cu4 tetrahedra).Moreover,the ultrahigh thermal stability renders the cluster a model system to highlight the power of NHCs(even other carbenes)in controlling geometrical,electronic and surface structure of polyhydrido copper clusters.

Preparation and Reaction of Naked Metal Clusters for Catalysis and Genetic Materials

Metal clusters that contain a small number of atoms usually present unique properties with dramatic dependence on their sizes,geometric structures,and compositions.The studies of naked metal clusters are devoted to develop new catalysts and functional materials of atomic precision,and enable to improve the fundamental theory of structure chemistry and to understand the basic reactions and properties bridging the gap between atoms and bulk materials.In particular,some interesting superatom clusters have received reasonable research interest indicative of materials gene of clusters.Here in this review,we simply summarize the preparation,stability,and reactivity of naked metal clusters with a few examples displayed.Hopefully it serves as a modest spur to stimulate more interest of related investigations in this field.