Dimensional Control of Assembling Metal Chalcogenide Clustersnuckolls.chem.columbia.edu/system/files/218/... · Dimensional Control of Assembling Metal Chalcogenide Clusters Natalia

Minireviewdoi.org/10.1002/ejic.202000039

EurJICEuropean Journal of Inorganic Chemistry

Nanoscale Building Blocks | Very Important Paper |

Dimensional Control of Assembling Metal Chalcogenide ClustersNatalia A. Gadjieva,[a] Anouck M. Champsaur,[a] Michael L. Steigerwald,*[a] Xavier Roy,*[a]

and Colin Nuckolls*[a]

Abstract: The ability to synthesize novel functional materialsat the nanoscale relies on the design and synthesis of versatile,tunable, atomically precise building blocks. Clusters of atomsexhibit physical properties beyond those of their constituentatoms, and new phenomena (e.g. electronic, magnetic) canemerge in such materials. This minireview describes a methodto create site-differentiated clusters and presents various syn-thetic approaches toward creating materials from these build-ing blocks. The cobalt selenide clusters fundamental to thisstudy are members of a larger class of clusters with the [M6E8]

1. Introduction

We present here a new class of clusters building blocks andtheir assembly into new tailored materials (Figure 1). Super-atoms are structured clusters of atoms with delocalized elec-tronic structures and atom-like electron characteristics.[1] Theterm can be traced back to the jellium model in which delocali-zation of electrons within cluster is assumed.[2] The definitionof a superatom has since expanded to include additional atomi-cally defined nanoclusters and can be differentiated in threegroups: 1) metalloids (with ideal atomic arrangement in the ele-ments at the molecular level, eg. Al77 and Ga84);[3] 2) non-metal(eg. fullerides); and 3) metal compounds including metal/non-metal bonding in the core assemblies.[4] The latter group willbe the focus in this review article. These superatoms retain theirelectronic and magnetic properties while remaining structurallyintact upon assembly and thus provide a new class of funda-mental building units. Creating nanoscale building blocks formaterials with atomic precision, site-selectivity, and tunable di-mensionality is an immense and largely unmet challenge.[5]

Synthetic methods must be developed to create site-differenti-ated superatoms in order to manipulate their surface ligandsand create extended assemblies in a predetermined way. Exist-ing methods to create such materials rely on self-assembly,solid-state methods, and, to some extent, serendipity. We havesynthesized and studied building blocks of the [M6E8] stoichio-metry (M = metal, E = chalcogen) and have targeted the cobaltselenide superatoms of the [Co6Se8L6] (where L = ligand) type.

[a] Department of Chemistry, Columbia University,3000 Broadway, New York, New York, 10027 USAE-mail: [email protected](s) from the author(s) for this article is/are available on the WWWunder https://doi.org/10.1002/ejic.202000039.

Eur. J. Inorg. Chem. 2020, 1245–1254 © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim1245

stoichiometry (M = metal, E = chalcogen). There are two ways toprepare suitably reactive [M6E8] monomeric clusters for bondedassemblies: (1) incorporating a secondary functionality on thecapping ligand, and (2) introducing removable, reactive ligandson the cluster surface. Rationally designed chemical transforma-tions give us precise control over the extent and dimensionalityof the resulting materials. The new bottom-up approaches to-wards extended solids presented in this minireview reveal howto build from 0-dimensional building blocks into 1-, 2-, and 3-dimensional systems that comprise clusters.

Figure 1. Materials that have been synthesized from the [Co6Se8L6] buildingblock include (clockwise): CO-functionalized [Co6Se8(CO)x(PEt3)6-x] clusters;carbene-inserted [Co6Se8(PEt3)6(CHSiMe3)2] superatoms where the carbene isinserted in the Co-Se bond; 3D MOF prepared through assembly of carboxylicacid functionalized superatom [Co6Se8(PEt2(4-C6H4COOH))6]; isocyanide-linked oligomers ([Co12Se16(CNC6H4NC)(PEt3)10] is shown); fused dimericsuperatoms [Co12Se16(PEt3)10]; and 2D molecular cloth from polymeric super-atoms with [Co6Se8(CNC6H4NC)2(PEt3)4]+ and [Mo6O19]2– as building blocks.

In this minireview, we will first discuss examples of materialscreated from [Co6Se8(PEt3)6] building blocks and then describeextended materials formed from strongly coupled cobalt selen-ide superatoms. The highly specific and chemoselective chemi-cal transformations described in this minireview provide precisecontrol over the delocalization and dimensionality of the mate-

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rials and give rise to controlled reactions in 1-, 2-, and 3-dimen-sions (1D, 2D, and 3D). The focus of this minireview is on atoolbox of regiochemically pure, atomically precise[Co6Se8(CO)x(PEt3)6-x] superatoms. The CO functionalization is asynthetically useful handle that can be easily manipulated todetermine the dimensionality in the desired direction. Throughthese building blocks we have created linked oligomers, fuseddimers by using carbene ligated superatoms, 2D woven poly-mers, and a 3D MOF with superatoms at the nodes (Figure 1).We will also detail the reaction chemistry that produces andthen utilizes these new superatomic building blocks.

Using the following methods we can control and tune thedimensionality and topology of our nanoscale building blocks:(1) solution-phase synthesis that allows us to synthesize CO-substituted superatoms and substitute them with other linkersand ligands, (2) electrocrystallization, a technique that allowsfor the assembly of a large variety of ions into single crystals of

Natalia Gadjieva receiver her B.S. in Chemistry from Radboud University. She received her M.A. from Columbia University in the City of NewYork, where she is currently a Ph.D. student working under the supervision of Prof. Colin Nuckolls. Her doctoral studies are focused onsuperatomic assemblies and organic crystals.

Anouck Champsaur received her B.S. in Chemistry from UC Berkeley, where she worked with Ron Zuckermann on peptoid polymers forprotein-mimetic materials. She obtained her Ph.D. in Chemistry from Columbia University with Colin Nuckolls in 2018. Her graduate researchfocused on the design and synthesis of novel metal chalcogenide clusters for the development of electronic materials with tuned dimensional-ity.

Michael Steigerwald was born in Detroit, Michigan, in 1956. He received both his B.S. and Ph.D. in Chemistry from the California Institute ofTechnology (USA). After an NIH Postdoctoral Fellowship at Princeton, he joined the Solid State Chemistry research department at BellLaboratories in 1985 and became a Distinguished Member of Technical Staff there in 1991. He has been a research scientist in the ChemistryDepartment at Columbia University in the City of NewYork (USA) since 2002.

Xavier Roy is currently Associate Professor of Chemistry at Columbia University. He earned his B.Eng. in Chemical Engineering from EcolePolytechnique of Montreal, and then received his Ph.D. in Chemistry (2011) from the University of British Columbia, under the supervision ofMark MacLachlan. He was an NSERC postdoctoral fellow in Colin Nuckolls′ group at Columbia University before joining the faculty in 2013.

Colin Nuckolls was born at Lakenheath RAF in Great Britain in 1970. He completed his undergraduate studies at the University of Texas atAustin (USA) under the supervision of Prof. Marye Anne Fox, and then received his Ph.D. in Chemistry from Columbia University in the Cityof New York (USA) with Prof. Thomas Katz in 1998. He was an NIH Postdoctoral Fellow under Prof. Julius Rebek, Jr. at the Scripps ResearchInstitute (USA). He joined the faculty at Columbia University in the City of New York (USA) in 2000, and currently is the Sheldon and DorotheaBuckler Professor of Material Science.

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high purity, and (3) traditional solid state synthesis applied tothese nanomateirals.[6]

For example, the [Co6Se8(PEt3)6] cluster with six triethylphos-phine ligands can be thought of as a 0D building block. Thecombination and self-assembly of two such 0D units (the cobaltselenide superatom and C60) form a new material that is analo-gous to an ionic crystal. Furthermore, we can covalently linkthese superatomic building blocks into predetermined shapesand arrangements: linear dimers, linear trimers, and polymers.We have found that the polymers of linked superatoms canform a two-dimensional box weave. To make new buildingblocks, we have developed a new chemical transformation thatfuses two [Co6Se8] cores to form a [Co12Se16] core. This fused[Co12Se16] core exhibits strong electronic coupling, electron de-localization, and quantum confined behavior. This fused dimeris an intermediate en route from molecules to extended solids.In total, the studies described in this minireview tap a new veinof research in creating materials where the coupling between



the subunits can be modulated along with the dimensionality,size, and extent of charge delocalization.

2. Metal Chalcogenide Clusters asSuperatoms

2.1. Superatoms in Materials Chemistry

To get a better understanding of the [Co6Se8]-type superatomwe need to first consider how it fits in the greater superatomfield. Superatoms have previously been defined as “cluster[s]consisting of more than one atom, but acting as a stable unitin some ways analogous to an atom”.[7] The superatom conceptwas first established for aluminum clusters of discrete sizes syn-thesized from gas phase experiments.[1a] Theoretical electronicstructure calculations revealed that the chemically stableanionic cluster [Al13]– has electronic affinities comparable to achlorine atom, and thus as a discrete unit this superatom mim-ics the behavior of individual halogen atoms.[8] A large numberof molecular clusters fit within this superatom definition, suchas fullerenes (1 nm),[9] polyoxometalates (POMs),[10] inorganicatomic clusters with metal chalcogenide cores (0.5–1 nm),[5a,11]

and larger, atomically defined inorganic nanocrystals (up to10 nm) (Figure 2a).[12] In general, superatoms exhibit a widerange of properties depending on their size and composition,for example their properties range from catalysts[13] to unusualmagnetic materials[14] to unusual redox behavior.

Figure 2. (a) Fullerenes, metal chalcogenide superatoms, and large inorganicnanocrystals (redrawn from ref.[28]). (b) Structurally the inorganic [M6E8] coreis composed of an octahedron of metal atoms contained within a cube offace-capping chalcogen atoms. (c) Scheme showing different synthetic routesto synthesize [M6E8] clusters.

The literature is rich with semiconducting inorganic nano-crystals whose size-dependent photophysics and electronicstructures, intrinsic to the nanosized regime, have led to a greatbreadth of useful materials and applications.[15] Several syn-thetic routes have been established to produce the aforemen-tioned nanocrystals with atomic precision such as reactionchemistry, solid state reactions,[16] size-focused methodol-ogy,[17] kinetically controlled monodisperse particle synthe-sis,[18] isolating mixed sizes by ultracentrifugation and chroma-tography,[5d,19] and other methods.[5c,20]


Noncovalent assembly of superatomic building blocks is themost common method of forming materials from them. Nano-particles can assemble through coordination or condensationby functionalizing nanoclusters with appropriate ligands. An ex-ample of this is self-assembly through hydrogen bonds as seenin nanoparticles including gold ones with carboxylic acid func-tionalized ligands.[21] Another example of assembly leading tointeresting emerging properties is that of [Ga84[N(SiMe3)2]20]x–

(x = 3,4), that gained interest due to the conductive and super-conductive behavior.[22] Lastly, we want to point out assemblyvia shape complementarity or charge-transfer, which will be dis-cussed later in the minireview. Quantum dots are important tomention here, where epitaxial connections have been estab-lished that lead to electronically coupled quantum dot lattices.The biggest obstacles in these molecularly linked quantum dotsis long-range structure, and the lack of atomic control over con-nection points. In general, the lack of atomic precision and se-lective ligand removal are issues that plague semiconductinginorganic nanocrystals.

We will limit our discussion in this minireview to atomicallyprecise metal chalcogenide clusters and use the term “supera-tom” predominantly as a structural classification. Metal chalco-genide nanoclusters are generally electron rich and exhibit mul-tiple reversible electron oxidations. Recent studies have shownthat the electronic states of such clusters are much like thoseof atoms, and that surface ligands can modulate their electronaccepting or donating capabilities.[23]

2.2. [M6E8] Clusters as Superatoms

This minireview focuses primarily on [Co6E8(PR3)6] superatomsthat are members of a larger class of clusters with the [M6E8]stoichiometry (M = metal, E = chalcogen). Structurally, the inor-ganic [M6E8] core is composed of an octahedron of metal atomscontained within a cube of face-capping chalcogen atoms (Fig-ure 2b). Passivating ligands L (such as phosphines in the case ofM = Co) coordinate each metal atom to yield [M6E8L6]. Althoughknown since the 1980s,[24] these clusters have only recently re-emerged as identifiable building blocks for extended materialsthanks to efforts in expanding their synthetic tunability. Multi-ple desirable properties like redox activity, large magnetic mo-ments, and luminescence arise in such superatoms.

The [M6E8] core is a constituent fragment of traditional inor-ganic materials with properties such as superconductivity andferromagnetism (e.g., Chevrel phases[25]). Historically the Che-vrel phases are synthesized via high temperature and pressurein the solid state. There are several reports of the ligand-cappedmonomeric analogues of these solid state compounds: (1) di-mensional reduction from the bulk (excision),[24b,26] (2) conden-sation of smaller clusters,[27] and (3) isolation of discrete clustersin the thermal reaction of phosphine chalcogenides with lowvalent transition metals (Figure 2c).[24e,24f ] The latter approachprovides a significant advantage over the former with its mildconditions, fewer steps due to a solution-based synthesis frommolecular components and greater synthetic tunability. Isolat-ing the fundamental building block of the Chevrel phases al-lowed for structural, electronic, and magnetic investigations of



the individual clusters that in turn led to further understandingof the bulk material. Our goal is to exploit the atomically precisebuilding blocks and create new materials, starting with[Co6E8L6].

3. Materials from Superatoms

The preparation of soluble [M6E8] units led to significant advan-ces in the bottom-up synthesis of extended solids. Their prepa-ration also led to several interesting questions, such as: Woulda [M6E8] monomer preserve its structural integrity when heatedto form an extended solid? Phosphine-capped [M6E8] supera-toms were found to convert to solid state transition metal chal-cogenides upon heating, in which the superatom core was se-verely distorted.[29] These very superatoms, interestingly, werethus intermediates between their atomic precursors (phosphinechalcogenides and low valent transition metals) and extendedsemiconducting solids. The question remained: how could a[M6E8] monomer be synthetically manipulated to rationally cre-ate new, interesting materials in which the core is structurallyintact, so that the properties intrinsic to the subunit are pre-served in the material? We answer this question in the sectionsthat follow.

3.1. [M6E8L6] (M = W, Re)

Multiple studies have explored the challenge (for M = W andRe) of using preformed [M6E8] entities as a rationale and facilemethod to impart their unique properties to new materials. Thedominate, common synthetic approach to such solids isthrough metal salt coordination to reactive groups on the cap-ping ligands of the superatoms (for examples, see DiSalvo,[30]

Long,[31] Fedorov,[32] and Zheng[33]). Superatoms with rheniumare particularly prominent in these examples, as their chemistryhas been richly developed: site-differentiated [Re6Se8] supera-toms have been synthesized and extensively studied,[34] as wellas their assembly into oligomers,[35] supramolecular arrays,[36]

and dendrimers.[37] These assemblies, while structurally interest-ing, do not exhibit significant inter-superatom interactions.

3.2. [Co6E8L6]

[Co6E8L6] superatoms are more electron-rich than other metalanalogues and feature L-type rather than X-type metal-cappingligands. Notably, a significant advantage is that the [Co6E8L6]superatom syntheses are mild and from molecular components.In contrast, the rhenium and molybdenum-based superatomsare obtained principally from the dimensional reduction of par-ent solid state compounds. Therefore, the molecules and mate-rials presented herein are assembled from the bottom up; thatis, from atoms to superatoms to solids with control and direc-tion.

Superatoms of the type [Co6E8(PR3)6] are typically synthe-sized from the combination of a low valent metal source andphosphine chalcogenide, such as Co2(CO)8 and R3PE, and canbe isolated as crystalline powders in good yields (Figure 2c).[38]


This method allows for synthetic tunability, with a large rangeof phosphines available, as well as different chalcogens (S, Se,Te). Ligand tunability allows for the incorporation of either reac-tive ligands or shape-directing ligands.[5e,39]

The electronic behavior of [Co6E8(PR3)6] superatoms has beenstudied.[23,40] They are electron rich, with electron-donating ca-pacities depending upon the ligand environment and chalco-gen. The conductance of such superatoms, functionalized withaurophilic contacts (thiomethyl groups) and gold tips has alsobeen reported.[41] The conductance of these molecules is com-plex and oxidation-state dependent. The following sectionbriefly reviews materials prepared from homoleptic[Co6E8(PR3)6] superatoms.

4. 0D Subunits

4.1. Salts from Superatomic Ions

The [Co6E8(PR3)6] superatoms are a 0D subunit. The electron-rich nature of the [Co6E8(PR3)6] superatom makes them idealpartners for electron-deficient and size complementary mol-ecules such as C60 and iron-oxo clusters (of the type [Fe8O4]) toform charge-transfer (CT) salts.[5e,11] In such CT salts, solutionsof components are first separately prepared and combined,then typical solution phase crystallization methods are used toprepare crystals that can then be analyzed crystallographically.The formation of a charge transfer and assembly between elec-tron-rich [Co6Se8(PEt3)6] and electron-deficient C60 exposed anessentially untapped vein of research. The structure of the re-sulting crystalline solid parallels that of an atomic analogue, thecadmium iodide (CdI2) structure type, but on a nanometer scaleinstead of an Ångstrom scale. Furthermore, the material exhibitsactivated electronic transport and magnetic ordering.

Thus, it is possible to build solids from superatomic molec-ular clusters that (1) conserve the structural integrity of theirbuilding blocks, (2) are nanoscale analogues of atomic solidsand (3) exhibit collective electronic and magnetic propertiesdue to interactions between constituent building blocks. Theseearly studies paved the way for a wide range of binary supera-tomic crystals with novel materials properties both in the bulkand in exfoliated form.[39a,41] Neutral nickel telluride clustersand fullerenes for example, form a binary superatomic solid[Ni9Te6(PEt3)8][C60] with a ferromagnetic phase transition.[42]

The magnetic behavior can be manipulated by varying the sizeand shape of the building blocks. This is done by changing theligands on the nickel telluride cluster from triethylphosphine(PEt3) to trimethylphosphine (PMe3), or by using C70 instead ofC60.

Superatomic crystals furthermore show promising applica-tions in thermoelectrics. Studies of [Co6E8(PEt3)6] (E = S, Se, Te)and C60 show that the mean free path increases with a higherorder in a structure, and thus thermal conductivity increaseswith decreasing temperature.[39d] The materials can additionallybe tuned via intercalation of an additional electroactive mol-ecule in an evacuated single crystal that modulates their elec-tronic and thermal transport.[39a] These examples demonstratethe possibility of assembling novel materials from atomicallydefined superatoms.



4.2. Co6E8(PR3)6 Superatoms as Charge Reservoirs

In addition to the 0D building unit of materials as described inthe previous section, electron-rich cobalt chalcogenides canalso be utilized as electronic dopants for a variety of materials.Transition metal dichalcogenides (TMDCs) are part of the 2Dmaterials family of semiconductors of the MX2 type where M isa transition metal, and X is a chalcogen atom. Doping of TMDCscan change the charge density, and thus determine electronic,optical and transport characteristics of the semiconductor,which is often done by introducing dopants.[22b] We reportedthe use of [Co6Se8(PEt3)6] as an electron donor to TMDCs wherefield-effect transistors (FET) made with p-type WSe2 were exam-ined. Upon treatment with the cluster, the p-type materialchanged characteristics to an n-type material, meaning thesemiconductor changed from hole transporting to electrontransporting. This technique also created a p-n junction by par-tially doping TMDCs.

We can also exploit the ability of superatoms to act as acharge reservoir with scanning tunneling microscope-basedbreak-junction. (STM-BJ).[41a,43] These studies paved the way toincorporate clusters into nanoelectronics, but to do so reliably,we have to have the ability to selectively exchange the ligands.The following section presents new methods to create site-dif-ferentiated [Co6E8L6] superatoms in which the desired ligandscan be removed and replaced. This decreases the length scaleof assemblies, increases cluster-to-cluster interactions, and in-troduces significant synthetic tunability that was previously un-attainable. We will discuss how tuning the [Co6E8L6] superatomwill open up the possibility to extend the framework in variousdimensions.

5. 1D Assemblies

In order to create assemblies with control over the dimensional-ity of the material, it is necessary to develop suitable, reactive[Co6Se8] monomers. Literature examples include reactions ofM+ with [Ge9[Si(SiMe3)3]3]–, where the shielding of the core isincomplete.

[44] Other examples include gold clusters linkedthrough bis-thiols,[45] and covalently linked silver clusters.[46]

Our approach was by introducing removable, reactive ligandson the cluster surface. To this end, we synthesized a family ofregiochemically pure, atomically precise carbonylated clustersof the form [Co6Se8(CO)x(PEt3)6-x] (Figure 3a).[47] The CO ligandcan be selectively removed via irradiation with light and substi-tution of suitable ligands.

5.1. Introducing an Exchangeable Ligand

The CO group is a synthetically useful handle that can be easilymanipulated. Previous strategies toward [Co6Se8(PR3)6] super-atoms employed stoichiometric combinations of Co2(CO)8, Se,and phosphine.[38,41c] In a new approach, we included a signifi-cant excess of Se, which effectively decreases the available reac-tive phosphine in the reaction mixture by acting as a phase-transfer catalyst. Using PEt3 as our ligand of choice we obtained[Co6Se8(CO)x(PEt3)6-x] as a mixture, with [Co6Se8(CO)(PEt3)5],


Figure 3. (a) Synthetic scheme towards CO substituted clusters that gives adistribution of isomers: [Co6Se8(CO)x(PEt3)6-x] (ethyl groups omitted for clar-ity). (b) Synthetic scheme of ligand substitution with phosphines and isocyan-ides. (c) scXRD of the linked dimer, [Co12Se16(CNC6H4NC)(PEt3)10][PF6]2, PF6 isomitted for clarity. (d) Magnetic susceptibility of the linked dimer vs. mono-mer [Co12Se16(CNC6H4NC)(PEt3)10][PF6]2 and [Co6Se8(CO)(PEt3)6][PF6] respec-tively, which indicates additive rather than interacting spins of the compo-nent monomers in the linked dimer.

trans- and cis-[Co6Se8(CO)2(PEt3)4] as major products. The prod-ucts are separated using fractional crystallization and columnchromatography. Using identical reagent stoichiometries withPPh3 as a ligand yields a mixture of [Co6Se8(CO)x(PPh3)6-x] su-peratoms with principally trans- and cis-[Co6Se8(CO)4(PPh3)2].The synthesis of tellurium derivatives has also been explored.[47]

The remainder of this minireview focuses on reactions of[Co6Se8(CO)x(PEt3)6-x] superatoms.

5.2. Electronic Structure Investigation

We investigated the effect of ligand substitution on the electrondensity distribution through multi-wavelength anomalous dis-persion (MAD) to better understand the reactivity of CO func-tionalized superatoms.[48] In particular, we used two supera-toms for this experiment, asymmetric [Co6Se8(CO)(PEt3)5] andpseudo-symmetric [Co6Se8(PnBu3)(PEt3)5], and studied the di-rect effect of ligand substitution from PnBu3 to CO.[49] Becausethe CO ligand gives access to new reactivity, the otherwiseidentical superatoms were used to study the effects on theatom site-specific density, and the effects of oxidation on theelectron density distribution.

Both neutral superatoms have a formal mixed-valent config-uration of [4CoIII2CoII], and by oxidizing those, the configurationchanges to [5CoIIICoII]. This leads to all four superatoms havinga core that is delocalized. MAD shows that the oxidation on theCo bound to CO is higher in oxidation than the other sites.[Co6Se8(PnBu3)(PEt3)5] on the other hand shows a meridionalarrangement of the two oxidation states. Additionally, the holecreated by oxidation of the clusters is different for the two spe-cies. [Co6Se8(CO)(PEt3)5] shows a hole on the Se with removal



of one electron, whereas the [Co6Se8(PnBu3)(PEt3)5 shows thehole delocalized on the Co. This revealed the influence of differ-ent ligands on the superatom core. Knowing the reactivitychange by alteration of the ligands is an important step to-wards exploring the materials applications of these clusters.

5.3. Superatomic Oligomers

The position of the CO group directs the formation of predeter-mined shapes and arrangements (Figure 3a). Initial substitu-tions reactions were carried out with simple two electron do-nors such as phosphines and isocyanides (Figure 3b).[47] Thesereactions occur in good yields in solution upon irradiation withvisible light. For example, trans-[Co6Se8(CO)2(PEt3)4] reacts withstoichiometric combinations of Et2PPhSMe and iPrNC, respec-tively, to yield trans-[Co6Se8(Et2PPhSMe)2(PEt3)4] and trans-[Co6Se8(iPrNC)2(PEt3)4]. The same superatom can further betreated with a ditopic linker, CNC6H4NC, to yield trans-[Co6Se8(CNC6H4NC)2(PEt3)4] (an excess must be used in order toprevent oligomerization). The resulting superatom has groupsthat can react further; this will be expanded upon in later sec-tions.

The appropriate combinations of [Co6Se8(CO)(PEt3)5] (cap-ping group), CNC6H4NC (linear linker), and trans-[Co6Se8(CNC6H4NC)2(PEt3)] (linear superatomic linker) yield thesimplest 1D covalent connections of superatoms, a linked dimerand a linear linked trimer: [Co12Se16(CNC6H4NC)(PEt3)10] and[Co18Se24(CNC6H4NC)2(PEt3)14]. The molecular structure of thelinked dimer (obtained by scXRD) is displayed in Figure 3c. Theelectronic and magnetic properties of the ensembles were sub-sequently investigated. The magnetic susceptibility study showsthat the dimeric species has two noninteracting spins from thetwo non-interacting monomeric species. This complements thefindings in cyclic voltammetry (CV), where additive electronicbehavior of the two cores in the dimeric species is observed.

5.4. Exposing and Extending the Core

The superatom core can be linearly extended to a fused dimerthat exhibits strong electronic coupling and electron delocaliza-tion, unlike the previously described linked dimer and trimer.Exposing the same starting monomer [Co6Se8(CO)(PEt3)5] to (tri-methylsilyl)diazomethane (TMSD) leads to a product that nowinvolves both a cobalt atom and an adjacent selenium atombridged by a carbene ligand: [Co6Se8(C(H)SiMe3)(PEt3)5] (Fig-ure 4a).[50] Rather than displaying a terminally bound ligand,this species exhibits chalcogen involvement with a Se–C-Cobinding motif (inset in Figure 4b). A bond length analysis re-veals that the carbon atom of the ligand has inserted into theCo-Se bond of the cluster and the core is significantly distortedas a result of this insertion. This species, while isolable, is con-siderably more reactive than previously made [Co6Se8] type su-peratoms.

This reactivity allows for the carbene (:C(H)SiMe3) to be re-moved without another ligand present, and thus for two coresto fuse directly. [Co6Se8(C(H)SiMe3)(PEt3)5]n[PF6]n (n = 0, 1) losesits carbene to form a dimer that is directly fused via two Co-Se


Figure 4. (a) Reaction of [Co6Se8(CO)(PEt3)5] with (trimethylsilyl)diazomethane(TMSD) that yields a carbene-terminated cluster, [Co6Se8(PEt3)5(CHSiMe3)]. (b)Reaction of the reactive carbene to form the fused dimer [Co12Se16(PEt3)10].(c) scXRD of the carbene-terminated cluster, [Co6Se8(CHSiMe3)(PEt3)5]. Ratherthan displaying a terminally bound ligand, this species exhibits chalcogeninvolvement with a Se–C-Co binding motif. (d) scXRD of the fused dimer,[Co12Se16(PEt3)10]. (e) scXRD of trans-[Co6Se8(CHSi(Me3)2(PEt3)4]. with possibleextension of the core by removing the carbene ligand to form extendedfused 1D wires.

bonds (Figure 4c). This reaction is particularly noteworthy be-cause the conditions to create this important structure are mildand selective. [Co12Se16(PEt3)10] and [Co12Se16(PEt3)10][PF6]2

are prepared from [Co6Se8(C(H)SiMe3)(PEt3)5] and[Co6Se8(C(H)SiMe3)(PEt3)5][PF6], respectively, via two differentroutes. In the first route, a solution of the neutral cluster istreated with an excess of pyridine; in the second route, the 1+carbene adduct is gently heated to 70 °C. The singly oxidizedfused dimer, [Co12Se16(PEt3)10][PF6], can be prepared from asimple redox reaction starting from either neutral or 2+ fuseddimer.

The formation of the dimer raised the question whether it ispossible to extend the structure to get 1D wires where the coreis connected in sequence. To accomplish this, a bis-carbenespecies, trans-[Co6Se8(C(H)SiMe3)2(PEt3)4] was prepared (Fig-ure 4e). There are two feasible approaches to create extendedwires: a solution processed synthesis as described for dimer for-mation, and solid-state synthesis where the carbene ligandcould be removed in vacuo or through heating. Such a solid-state reaction was previously shown with a rhenium species[Re6Se8(PEt3)5(MeCN)]2+ where dynamic vacuum was used to re-move the acetonitrile ligand so that two cores could fuse to-gether.[24a,51] The challenge that remains to produce the 1Dwires is in placing the subsequent cores close enough togetherfor the fusion to happen in the solid state in a reliable andreproducible way.

The electronic behavior of the fused dimer[Co12Se16(PEt3)10]n+ (FD) was studied and compared to that ofan all-phosphine monomer [Co6Se8(PEt3)6]n+ (M), and previ-ously mentioned bridged dimer [Co12Se16(CNC6H4NC)(PEt3)10]n+

(BD). The cyclic voltammograms of all species are shows in Fig-ure 5a. There are two striking features. (1) The redox events areone-electron in FD vs. two-electron in BD suggesting electron



Figure 5. Reproduced with permission from ref.[50] Copyright 2018 American Chemical Society. (a) CV of fused dimer [Co12Se16(PEt3)10]n (FD), aryl-diisocyanidebridged dimer [Co12Se16(PEt3)10(CNC6H4NC)]n (BD), parent monomer [Co6Se8(PEt3)6]n (M), [Co6Se8(PEt3)5(CNC6H3Me2)]n and [Co6Se8(PEt3)5(CO)]n. The red arrowshows the effective band gap as estimated from CV and the blue arrow shows the ΔE1/2 for the dimeric species. (b) Singly occupied orbitals of the tripletstate of the coordinatively unsaturated [Co6Se8(PMe3)5]. One orbital is located on the unsaturated Co, while the other is distributed between Co and Se,suggesting that the Co-Se bond is cleaved upon ligand removal. (c) Calculated HOMO/LUMO splittings of dimer, trimer, tetramer. With further extension ofthe core, the band gap decreases.

delocalization in the fused species. (2) The estimated HOMO/LUMO levels from the electrochemistry reveal a twofold bandgap reduction in FD relative to the monomer. Optical spectro-scopy on these species further reveals striking differences be-tween FD, BD, and M in that FD is easier to excite optically.[50]

Quantum chemical calculations performed on this species, re-viewed in the following section, bring further insight into thissurprising behavior.

5.5. Electronic Structure Calculations

The experimental data on this intriguing fused dimer are sup-plemented with an understanding of the electronic structureusing quantum chemical calculations. Quantum calculations re-veal that [Co6Se8(CO)(PEt3)5] and [Co6Se8(PEt3)6] are a closedshell, singlet species, yet [Co6Se8(PEt3)5] (the proposed interme-diate generated upon loss of a CO) is an open shell, tripletspecies. This triplet is characterized by two singly occupied or-bitals: one is localized on the Co atom and the other is sharedbetween the Co and an adjacent Se atom (Figure 5b). Together,this suggests the breaking of a Co-Se bond upon ligand dissoci-ation and explains the reactivity of such a species with botha triplet carbene (forming [Co6Se8(C(H)SiMe3)(PEt3)5]), and withanother coordinatively unsaturated reaction partner,[Co6Se8(PEt3)5] to form [Co12Se16(PEt3)10].

The emergent properties of the fused dimer sparked our in-terest to extend the structure even further. The density func-tional theory calculated HOMO/LUMO splitting of the monomerand fused dimer are similar to those estimated experimentally


from CV data. The HOMO and LUMO energies of a fused trimerand fused tetramer ([Co18Se24(PMe3)14] and [Co24Se32(PMe3)18],respectively) were also calculated. Upon going from the fuseddimer to fused tetramer, each additional fused [Co6Se8] unitdecreases the HOMO/LUMO splitting of the nanostructure (Fig-ure 5c). The decrease in the band gap of a nanostructure withits core expansion is a well-known phenomenon in nanosci-ence.[52] The observation of this phenomenon with atomicallyprecise metal chalcogenide superatoms, however, is new andexciting.

6. 2D: Molecular Cloth UsingElectrocrystallizationThe development of site-differentiated clusters was a significantadvance toward the programmable connectivity of superatoms.We expand upon the reaction chemistry of discrete dimers andtrimers to access extended, covalent materials with increasingcomplexity at the nanoscale.

Electrocrystallization is a synthetic tool that assembles solidstate materials from molecular components in solution. In theexperimental setup, a weak current slowly oxidizes (or reduces)an electroactive material in the presence of an electrolyte. Overtime, crystalline materials composed of the ionic componentsfrom the solution are assembled at the electrode. This tech-nique thus assembles molecular ions from solution into crystal-line solids of high purity; we wished to extend this technique tosuperatomic ions. Could we use electrocrystallization to createcovalently linked superatomic assemblies of [Co6Se8] units? We



needed appropriate superatomic building blocks that wouldsatisfy the important condition of being reactive upon oxid-ation. Specifically, we required superatoms with labile ligands.Once the appropriate electroactive building block is identified,a variety of parameters can be tuned in the experimental setup:solvent, current magnitude, temperature, and electrolyte.

The CO isomers of [Co6Se8] superatoms are not ideal candi-dates for electrocrystallization themselves due to the sturdinessof the CO ligand upon oxidation of the superatom to 1+ andeven 2+ states. However, the bis-isocyanide superatom previ-ously introduced, trans-[Co6Se8(CNC6H4NC)2(PEt3)4], was foundto be somewhat labile upon oxidation. Trans-[Co6Se8(CNC6H4NC)2(PEt3)4] (exhibiting a trans-arrangement ofcoordinating isocyanide secondary groups) was combined witha shape complementary anionic template [Mo6O19]2– in an elec-trocrystallization cell. The resulting structure is composed oftwo-dimensional interwoven superatom polymer strands thatform a nanoscale box weave (Figure 6a).[53]

Figure 6. Reproduced with permission from ref.[53] Copyright 2017 AmericanChemical Society. (a) SCXRD of the molecular cloth formed from buildingblocks [Co6Se8(CNC6H4NC)2(PEt3)4]+ and [Mo6O19]2–. The triethyl phosphinegroups and hydrogen atoms have been removed to clarify the view. (b) Thetemplation utilizes the 4-fold axis of [Mo6O19]2–. The tetragonal structure ofthe dianionic molecule directs the directionality towards a box weave. (c) Pi-to-pi interactions of overlapping bridging linkers hold the strands in registry.(d) Side view of the crystal packing showing the cationic and anionic layers(a-axis). Note that the ethyl groups from the phosphine subunits, which en-velop the surface of the templating nano-oxides with directional C–H···Ohydrogen bonds, have been omitted in b and d to clarify the view.

As anticipated, the electrocrystallization experiment resultedin a crystalline, ionic solid of high purity from monomeric com-ponents in solution. Unexpectedly, the [Co6Se8] units were co-valently connected in the structure, and with unprecedentedcomplexity. Figure 6 displays the structural details of this mate-rial. In brief, one-dimensional polymers of repeated [Co6Se8]units connected by bis-isocyanide ligands form a two-dimen-sional box weave, whose size is determined by that of the ani-onic template. Each layer of this woven nanomaterial alternateswith a layer of [Mo6O19]2–. The layers are thus held together notonly by shape complementarity but also by ionic interactions.Pi-to-pi stacking of overlapping 1,4-bis-isocyanide linkers dic-tates the crossover points of the weave.


7. 3D Assemblies

Various 3D networks have been synthesized to form MOFs outof metal chalcogenide clusters.[54]

Along with previously described 1D-, and 2D-materials, 3D-crystalline materials were obtained via solvothermal reaction ofa [Co6Se8PEt2(4-C6H4COOH)]6 building block with a divalentzinc source.[55] The carboxylic acid functionalized cluster formstwo types of materials upon reaction with Zn(NO3)2 in whichthe dimensionality is controlled by small alterations in the sol-vent system from DMF/methanol to DMF/ethanol. One of thematerials is a 3D framework, whereas the second consists ofstacked 2D layers, which can be chemically exfoliated to givesoluble free-floating sheets that retain the redox behavior ofthe parent compound.

8. Summary and Outlook

The results presented in this minireview yield a deeper under-standing of the reactivity and tunability of octahedral cobaltselenide clusters. Using the preformed molecular clusters, al-lows component properties to be tuned independently. Theability to manipulate the inter-superatom bonding and interac-tions to expand our traditional periodic table to a third dimen-sion. The subsequent assembly installs synergistic or collectiveelectronic and/or magnetic properties into the material.

Extension in dimensionality has been examined throughfunctionalization of the [Co6Se8(CO)x(PEt3)6-x] superatom build-ing block with various ligands. Linear linked oligomers and corebound dimers, 2D sheets, and 3D MOFs have been made. Weare now exploring applications in these new emerging materi-als. The capability of the superatoms to readily donate electronsmake them charge reservoirs. Having the toolbox to freelychange the ligands as desired through mild reactions has beenan integral finding towards that goal. Furthermore, the 1D wirescould be applied in electronics, where the conductive pathlength can be atomically precise. The extension also gives riseto the possibility for interesting magnetic properties. The 2Dmolecular cloth is a unique nanoscale structure that could beexfoliated electrochemically, as the 2D cloth has a presumedstrength and toughness due to the weave. The 3D MOF couldbe used as electroactive sieves, and its 2D analog could beused as a porous, ultrathin, and redox-active material in energystorage or modified electrodes for catalysis.

AcknowledgmentsWe graciously acknowledge our many collaborators who havehelped us in these projects. C. N. thanks Sheldon and DorotheaBuckler for their generous support. A. C. thanks the Arun Guthi-konda Memorial Fellowship in Organic Chemistry for their gen-erous support of her studies. Support for this research was pro-vided by the Center for Precision Assembly of Superstratic andSuperatomic Solids, an NSF MRSEC (award number DMR-1420634), and the Air Force Office of Scientific Research (awardnumber FA9550-18-1-0020).



Keywords: Chalcogens · Cluster compounds · Nanoscaleatoms · Nanoscale building blocks · Materials chemistry

[1] a) D. E. Bergeron, A. W. Castleman, T. Morisato, S. N. Khanna, Science2004, 304, 84–87; b) D. E. Bergeron, P. J. Roach, A. W. Castleman Jr., N. O.Jones, S. N. Khanna, Science 2005, 307, 231–235.

[2] W. D. Knight, K. Clemenger, W. A. De Heer, W. A. Saunders, M. Y. Chou,M. L. Cohen, Phys. Rev. Lett. 1984, 52, 2141–2143.

[3] A. Schnepf, H. Schnöckel, Angew. Chem. Int. Ed. 2002, 41, 3532–3554;Angew. Chem. 2002, 114, 3682.

[4] P. Jena, Q. Sun, Chem. Rev. 2018, 118, 5755–5870.[5] a) V. Chauhan, A. C. Reber, S. N. Khanna, J. Am. Chem. Soc. 2017, 139,

1871–1877; b) Z. Luo, A. W. Castleman, Acc. Chem. Res. 2014, 47, 2931–2940; c) G. T. Schaaff, R. L. Whetten, J. Phys. Chem. B 1999, 103, 9394–9396; d) Y. Negishi, T. Nakazaki, S. Malola, S. Takano, Y. Niihori, W. Kura-shige, S. Yamazoe, T. Tsukuda, H. Häkkinen, J. Am. Chem. Soc. 2015, 137,1206–1212; e) A. Turkiewicz, D. W. Paley, T. Besara, G. Elbaz, A. Pinkard,T. Siegrist, X. Roy, J. Am. Chem. Soc. 2014, 136, 15873–15876.

[6] P. Batail, K. Boubekeur, M. Fourmigué, J.-C. P. Gabriel, Chem. Mater. 1998,10, 3005–3015.

[7] S. A. Claridge, A. W. Castleman, S. N. Khanna, C. B. Murray, A. Sen, P. S.Weiss, ACS Nano 2009, 3, 244–255.

[8] S. N. Khanna, P. Jena, Chem. Phys. Lett. 1994, 219, 479–483.[9] a) W. Krätschmer, L. D. Lamb, K. Fostiropoulos, D. R. Huffman, Nature

1990, 347, 354–358; b) H. W. Kroto, J. R. Heath, S. C. O'Brien, R. F. Curl,R. E. Smalley, Nature 1985, 318, 162–163; c) X.-J. Kong, L.-S. Long, Z.Zheng, R.-B. Huang, L.-S. Zheng, Acc. Chem. Res. 2010, 43, 201–209.

[10] D.-L. Long, R. Tsunashima, L. Cronin, Angew. Chem. Int. Ed. 2010, 49,1736–1758; Angew. Chem. 2010, 122, 1780.

[11] X. Roy, C.-H. Lee, A. C. Crowther, C. L. Schenck, T. Besara, R. A. Lalancette,T. Siegrist, P. W. Stephens, L. E. Brus, M. L. S. P. Kim, et al., Science 2013,341, 157–160.

[12] a) C. B. Murray, D. J. Norris, M. G. Bawendi, J. Am. Chem. Soc. 1993, 115,8706–8715; b) M. L. Steigerwald, A. P. Alivisatos, J. M. Gibson, T. D. Harris,R. Kortan, A. J. Muller, A. M. Thayer, T. M. Duncan, D. C. Douglass, L. E.Brus, J. Am. Chem. Soc. 1988, 110, 3046–3050.

[13] F. Song, Y. Ding, B. Ma, C. Wang, Q. Wang, X. Du, S. Fu, J. Song, EnergyEnviron. Sci. 2013, 6, 1170.

[14] A. Müller, R. Sessoli, E. Krickemeyer, H. Bögge, J. Meyer, D. Gatteschi, L.Pardi, J. Westphal, K. Hovemeier, R. Rohlfing, et al., Inorg. Chem. 1997,36, 5239–5250.

[15] a) Y. Bi, Y. Yuan, C. L. Exstrom, S. A. Darveau, J. Huang, Nano Lett. 2011,11, 16; b) N. C. Greenham, X. Peng, A. P. Alivisatos, Phys. Rev. 1996, 54,17629–17637; c) A. George, E. S. Shibu, S. M. Maliyekkal, M. S. Bootharaju,T. Pradeep, ACS Appl. Mater. Interfaces 2012, 4, 639–644; d) X. Yuan, Z.Luo, Y. Yu, Q. Yao, J. Xie, Chem. Asian J. 2013, 8, 858–871; e) G. Li, R. Jin,J. Am. Chem. Soc. 2014, 136, 11347–11354; f ) Y. Negishi, M. Mizuno, M.Hirayama, M. Omatoi, T. Takayama, A. Iwase, A. Kudo, Nanoscale 2013, 5,7188.

[16] M. L. Steigerwald, MRS Proc. 1988, 131, 37–43.[17] M. Zhu, E. Lanni, N. Garg, M. E. Bier, R. Jin, J. Am. Chem. Soc. 2008, 130,

1138–1139.[18] a) C. Zeng, Y. Chen, A. Das, R. Jin, J. Phys. Chem. Lett. 2015, 6, 2976–2986;

b) Y. Yu, X. Chen, Q. Yao, Y. Yu, N. Yan, J. Xie, Chem. Mater. 2013, 25, 946–952; c) M. P. Hendricks, M. P. Campos, G. T. Cleveland, I. Jen-La Plante,J. S. Owen, Science 2015, 348, 1226–30; d) R. Jin, H. Qian, Z. Wu, Y. Zhu,M. Zhu, A. Mohanty, N. Garg, J. Phys. Chem. Lett. 2010, 1, 2903–2910.

[19] R. P. Carney, J. Y. Kim, H. Qian, R. Jin, H. Mehenni, F. Stellacci, O. M. Bakr,Nat. Commun. 2011, 2, 335.

[20] a) Z.-Y. Wang, M.-Q. Wang, Y.-L. Li, P. Luo, T.-T. Jia, R.-W. Huang, S.-Q. Zang,T. C. W. Mak, J. Am. Chem. Soc. 2018, 140, 1069–1076; b) C. D. Bain, E. B.Troughton, Y. T. Tao, J. Evall, G. M. Whitesides, R. G. Nuzzo, J. Am. Chem.Soc. 1989, 111, 321–335; c) Y. Yu, Z. Luo, Y. Yu, J. Y. Lee, J. Xie, ACS Nano2012, 6, 7920–7927; d) Y. Negishi, Y. Takasugi, S. Sato, H. Yao, K. Kimura,T. Tsukuda, J. Am. Chem. Soc. 2004, 126, 6518–6519.

[21] B. Yoon, W. D. Luedtke, R. N. Barnett, J. Gao, A. Desireddy, B. E. Conn, T.Bigioni, U. Landman, Nat. Mater. 2014, 13, 807–811.

[22] a) O. N. Bakharev, N. Zelders, H. B. Brom, A. Schnepf, H. Schnöckel, L.Jos de Jongh, Eur. Phys. J. D 2003, 22-27, 101–104; b) O. N. Bakharev, D.


Bono, H. B. Brom, A. Schnepf, H. Schnöckel, L. J. De Jongh, Phys. Rev. Lett.2006, 96, 117002.

[23] See ref.[5a].[24] a) J. R. Long, L. S. McCarty, R. H. Holm, J. Am. Chem. Soc. 1996, 118,

4603–4616; b) Y. V. Mironov, A. V. Virovets, N. G. Naumov, V. N. Ikorskii,V. E. Fedorov, Chem. Eur. J. 2000, 6, 1361–1365; c) F. Cecconi, C. A. Ghil-ardi, S. Midollini, A. Orlandini, P. Zanello, Polyhedron 1986, 5, 2021–2031;d) G. Christou, K. S. Hagen, J. K. Bashkin, R. H. Holm, Inorg. Chem. 1985,24, 1010–1018; e) D. Fenske, J. Ohmer, J. Hachgenei, Angew. Chem. Int.Ed. Engl. 1985, 24, 993–995; Angew. Chem. 1985, 97, 993; f ) B. Hessen, T.Siegrist, T. Palstra, S. M. Tanzler, M. L. Steigerwald, Inorg. Chem. 1993, 32,5165–5169; g) M. L. Steigerwald, T. Siegrist, S. M. Stuczynski, Inorg. Chem.1991, 30, 4940–4945; h) D. Fenske, J. Ohmer, J. Hachgenei, K. Merzweiler,Angew. Chem. Int. Ed. Engl. 1988, 27, 1277–1296; Angew. Chem. 1988,100, 1300; i) T. Saito, H. Imoto, Bull. Chem. Soc. Jpn. 1996, 69, 2403–2417;j) X. Zhang, R. E. McCarley, Inorg. Chem. 1995, 34, 2678–2683; k) G. M.Ehrlich, C. J. Warren, D. A. Vennos, D. M. Ho, R. C. Haushalter, F. J. DiSalvo,Inorg. Chem. 1995, 34, 4454–4459.

[25] R. Chevrel, M. Hirrien, M. Sergent, Polyhedron 1986, 5, 87–94.[26] S. C. Lee, R. H. Holm, Angew. Chem. Int. Ed. Engl. 1990, 29, 840–856;

Angew. Chem. 1990, 102, 868.[27] T. Saito, N. Yamamoto, T. Nagase, T. Tsuboi, K. Kobayashi, T. Yamagata, H.

Imoto, K. Unoura, Inorg. Chem. 1990, 29, 764–770.[28] P. D. Jadzinsky, G. Calero, C. J. Ackerson, D. A. Bushnell, R. D. Kornberg,

Science 2007, 318, 430–433.[29] M. L. Steigerwald, Polyhedron 1994, 13, 1245–1252.[30] S. Jin, F. J. DiSalvo, Chem. Mater. 2002, 14, 3448–3457.[31] a) M. V. Bennett, L. G. Beauvais, M. P. Shores, J. R. Long, J. Am. Chem. Soc.

2001, 123, 8022–8032; b) M. P. Shores, L. G. Beauvais, J. R. Long, J. Am.Chem. Soc. 1999, 121, 775–779.

[32] a) N. G. Naumov, S. B. Artemkina, V. E. Fedorov, D. V. Soldatov, J. A.Ripmeester, Chem. Commun. 2001, 0, 571–572; b) M. S. Tarasenko, N. G.Naumov, D. Y. Naumov, N. V. Kuratieva, V. E. Fedorov, Russ. J. Coord. Chem.2006, 32, 494–503.

[33] H. D. Selby, P. Orto, M. D. Carducci, Z. Zheng, Inorg. Chem. 2002, 41,6175–6177.

[34] a) P. J. Orto, G. S. Nichol, R. Wang, Z. Zheng, Inorg. Chem. 2007, 46, 8436–8438; b) M. W. Willer, J. R. Long, C. C. McLauchlan, R. H. Holm, Inorg.Chem. 1998, 37, 328–333; c) Z. Zheng, J. R. Long, R. H. Holm, J. Am.Chem. Soc. 1997, 119, 2163–2171.

[35] H. D. Selby, Z. Zheng, T. G. Gray, R. H. Holm*, Inorg. Chim. Acta 2001,312, 205–209.

[36] a) H. D. Selby, B. K. Roland, Z. Zheng, Acc. Chem. Res. 2003, 36, 933–944;b) H. D. Selby, P. Orto, Z. Zheng, Polyhedron 2003, 22, 2999–3008.

[37] a) B. K. Roland, H. D. Selby, M. D. Carducci, Z. Zheng, J. Am. Chem. Soc.2002, 124, 3222–3223; b) R. W. and, Z. Zheng, J. Am. Chem. Soc. 1999,121, 3549–3550.

[38] S. M. Stuczynski, Y.-U. Kwon, M. L. Steigerwald, J. Organomet. Chem.1993, 449, 167–172.

[39] a) E. S. O'Brien, M. T. Trinh, R. L. Kann, J. Chen, G. A. Elbaz, A. Masurkar,T. L. Atallah, M. V. Paley, N. Patel, D. W. Paley, et al., Nat. Chem. 2017, 9,1170–1174; b) A. Pinkard, A. M. Champsaur, X. Roy, Acc. Chem. Res. 2018,51, 919–929; c) B. Choi, J. Yu, D. W. Paley, M. T. Trinh, M. V. Paley, J. M.Karch, A. C. Crowther, C.-H. Lee, R. A. Lalancette, X. Zhu, et al., Nano Lett.2016, 16, 1445–1449; d) W.-L. Ong, E. S. O'Brien, P. S. M. Dougherty, D. W.Paley, C. Fred Higgs III, A. J. H. McGaughey, J. A. Malen, X. Roy, Nat. Mater.2017, 16, 83–88; e) C.-H. Lee, L. Liu, C. Bejger, A. Turkiewicz, T. Goko, C. J.Arguello, B. A. Frandsen, S. C. Cheung, T. Medina, T. J. S. Munsie, et al., J.Am. Chem. Soc. 2014, 136, 16926–16931.

[40] a) B. M. Boardman, J. R. Widawsky, Y. S. Park, C. L. Schenck, L. Venkatara-man, M. L. Steigerwald, C. Nuckolls, J. Am. Chem. Soc. 2011, 133, 8455–8457; b) B. J. Reeves, D. M. Shircliff, J. L. Shott, B. M. Boardman, DaltonTrans. 2015, 44, 718–724.

[41] a) B. Choi, B. Capozzi, S. Ahn, A. Turkiewicz, G. Lovat, C. Nuckolls, M. L.Steigerwald, L. Venkataraman, X. Roy, Chem. Sci. 2016, 7, 2701–2705; b)G. Lovat, B. Choi, D. W. Paley, M. L. Steigerwald, L. Venkataraman, X. Roy,Nat. Nanotechnol. 2017, 12, 1050–1054; c) X. Roy, C. L. Schenck, S. Ahn,R. A. Lalancette, L. Venkataraman, C. Nuckolls, M. L. Steigerwald, Angew.Chem. Int. Ed. 2012, 51, 12473–12476; Angew. Chem. 2012, 124, 12641.

[42] A. C. Reber, S. N. Khanna, npj Comput. Mater. 2018, 4, 33.



[43] X. Roy, C. L. Schenck, S. Ahn, R. A. Lalancette, L. Venkataraman, C.Nuckolls, M. L. Steigerwald, Angew. Chem. Int. Ed. 2012, 51, 12627–12627.

[44] a) C. Schenk, F. Henke, G. Santiso-Quiñones, I. Krossing, A. Schnepf, Dal-ton Trans. 2008, 4436–4441; b) F. Henke, C. Schenk, A. Schnepf, DaltonTrans. 2009, 9141–9145; c) C. Schenk, A. Schnepf, Angew. Chem. Int. Ed.2007, 46, 5314–5316; Angew. Chem. 2007, 119, 5408.

[45] T. Lahtinen, E. Hulkko, K. Sokołowska, T. R. Tero, V. Saarnio, J. Lindgren,M. Pettersson, H. Häkkinen, L. Lehtovaara, Nanoscale 2016, 8, 18665–18674.

[46] M. Bodiuzzaman, A. Nag, R. Pradeep Narayanan, A. Chakraborty, R. Bag,G. Paramasivam, G. Natarajan, G. Sekar, S. Ghosh, T. Pradeep, Chem. Com-mun. 2019, 55, 5025–5028.

[47] A. M. Champsaur, A. Velian, D. W. Paley, B. Choi, X. Roy, M. L. Steigerwald,C. Nuckolls, Nano Lett. 2016, 16, 5273–5277.

[48] S.-L. Chang, Springer Series in Solid-state Sciences, Springer-verlag BerlinHeidelberg, 2004, vol. 143.


[49] R. Hernández Sánchez, A. M. Champsaur, B. Choi, S. G. Wang, W. Bu, X.Roy, Y.-S. Chen, M. L. Steigerwald, C. Nuckolls, D. W. Paley, Angew. Chem.Int. Ed. 2018, 57, 13815–13820; Angew. Chem. 2018, 130, 14011.

[50] A. M. Champsaur, T. J. Hochuli, D. W. Paley, C. Nuckolls, M. L. Steigerwald,Nano Lett. 2018, 18, 4564–4569.

[51] Z. Zheng, R. H. Holm, Inorg. Chem. 1997, 36, 5173–5178.[52] a) L. Brus, Appl. Phys. A 1991, 53, 465–474; b) A. P. Alivisatos, Science

1996, 271, 933–937.[53] A. M. Champsaur, D. W. Paley, M. L. Steigerwald, C. Nuckolls, P. Batail, J.

Am. Chem. Soc. 2017, 139, 11718–11721.[54] Y. M. Litvinova, Y. M. Gayfulin, K. A. Kovalenko, D. G. Samsonenko, J.

van Leusen, I. V. Korolkov, V. P. Fedin, Y. V. Mironov, Inorg. Chem. 2018,57, 2072–2084.

[55] A. M. Champsaur, J. Yu, X. Roy, D. W. Paley, M. L. Steigerwald, C. Nuckolls,C. M. Bejger, ACS Cent. Sci. 2017, 3, 1050–1055.

Received: January 14, 2020

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