Transition Metal Clusters Research Articles

Thermodynamics of Transition Metal Ion Binding to Proteins.

Modeling the thermodynamics of a transition metal (TM) ion assembly be it in proteins or in coordination complexes affords us a better understanding of the assembly and function of metalloclusters in diverse application areas including metal organic framework design, TM-based catalyst design, the trafficking of TM ions in biological systems, and drug design in metalloprotein platforms. While the structural details of TM ions bound to metalloproteins are generally well understood via experimental and computational approaches, accurate studies describing the thermodynamics of TM ion binding are rare. Herein, we demonstrate that we can obtain accurate structural and absolute binding free energies of Co2+ and Ni2+ to the enzyme glyoxalase I using an optimized 12-6-4 (m12-6-4) potential. Critically, this model simultaneously reproduces the solvation free energy of the individual TM ions and reproduces the thermodynamics of TM ion-ligand coordination as well as the thermodynamics of TM ion binding to a protein active site unlike extant models. We find the incorporation of the thermodynamics associated with protonation state changes for the TM ion (un)binding to be crucial. The high accuracy of m12-6-4 potential in this study presents an accurate route to explore more complicated processes associated with TM cluster assembly and TM ion transport.

Bismuth for Controlled Assembly/Disassembly of Transition-Metal Oxo Clusters, Defining Reaction Pathways in Inorganic Synthesis and Nature.

Trivalent bismuth is a unique heavy p-block ion. It is highly insoluble in water, due to strong hydrolysis tendencies, and known for low toxicity. Its lone pair is structure-directing, providing framework materials with structural flexibility, leading to piezoelectric and multiferroic function. The flexibility it provides is also advantageous for dopants and vacancies, giving rise to conductivity, luminescence, color, and catalytic properties. We are exploiting Bi3+ in a completely different way, as a knob to "tune" the solubility and stability of transition-metal oxo clusters. The lone pair allows capping and isolation of metastable cluster forms for solid-state and solution characterization. With controlled release of the bismuth (via bismuth oxyhalide metathesis), the metal oxo clusters can be retained in aqueous solution, and we can track their reaction pathways and conversion to related metal oxyhydroxides. Here we present isolation of a bismuth-stabilized MnIV cluster, fully formulated [MnIV6Bi2KO9(CH3COO)10(H2O)3(NO3)2] (Mn6Bi2). In addition to characterization by single-crystal X-ray diffraction, solution characterization in acetonitrile and acetonitrile-acetic acid by small-angle X-ray scattering (SAXS) and electrospray ionization mass spectrometry shows high stability and the tendency of Mn6Bi2 to link into chains by bridging the bismuth (and potassium) caps with nitrate and acetate ligands. On the other hand, the dissolution of Mn6Bi2 in water, with and without metathesis of the bismuth, leads to the precipitation of related oxyhydroxide phases, which we characterized by transmission electron microscopy (TEM), electron diffraction, and energy-dispersive spectroscopy, and the conversion pathway by SAXS. Without removal of bismuth, amorphous manganese/bismuth oxyhydroxides precipitate within a day. On the other hand, metathesis of BiOBr yields a solution containing soluble manganese oxyhydroxide prenucleation clusters that assemble and precipitate over 10 days. This allows tracking of the reaction pathway via SAXS. We observe one-dimensional growth of species, followed by the precipitation of nanocrystalline hollandite (identified by TEM). The hollandite is presumably templated by the K+, originally in the crystalline lattice of Mn6Bi2. In this Forum Article that combines new results and prospective, we compare these results to prior studies in which we first introduced the use of capping Bi3+ to stabilize reactive clusters, followed by destabilization to understand reaction pathways in synthesis and low-temperature geochemistry.

Switchable Two-Dimensional Waveguiding Abilities of Luminescent Hybrid Nanocomposites for Active Solar Concentrators.

Passing from fossil energy sources to renewable ones, meanwhile answering the increasing world energy demand, will require innovative and low-cost technologies. Smart photovoltaic windows could fulfill our needs in this matter. Their transparency can be controlled to manage solar energy and regulate interior temperature and illumination. Here, we present the one-pot synthesis of polymer-dispersed liquid crystals (PDLCs), in which highly red-NIR phosphorescent transition metal clusters are selectively embedded, either in the polymer, in the liquid crystal, or in both phases. The PDLC matrix is used as a tunable waveguide to transfer the emitted light from nanoclusters to the edge of the device, where solar cells could be placed to convert it into electricity. Edge emission is obtained in both "off" and "on" states, with a maximum intensity for the scattering "off" one. These doped PDLCs showing photo-activity features and high stability under voltage represent key stepping stones for integration in buildings, displays, and many other technologies.

Colour centre controlled formation of stable sub-nanometer transition metal clusters on TiO2 nanosheet for high efficient H2 production

The transition elements (Fe, Co, Ni) are important substitutes for noble metals as the co-catalysts in hydrogen evolution reaction. Enhancing the atom utilization efficiency is highly desirable, but preparation and preservation of the transition metal catalysts with the size downscaling to sub-nanometer are challenging. In this work, Fe, Co and Ni clusters with subnano size as co-catalysts are synthesized by controllable growth on 2D ultrathin TiO2(B) nanosheets for hydrogen evolution using a photo deposition method. The ultra-small Fe, Co, and Ni co-catalysts on the TiO2(B) nanosheets exhibit remarkably enhanced photo activities, compared to that with the best Pt loading. It is found that the oxygen bridge vacancies act as the colour centres locating at the position adjacent to the O1-Ti1 sites on the TiO2(B) (0 0 1) surface. The photo-colouration and photo-bleaching have significantly impact on the nucleation and growth of the metallic clusters. The high density and uniform dispersion of the sub-nano-sized transition metal clusters benefits for the photo reduction under light irradiation, as well as efficient carrier separation, leading to a great improvement of the photo activity.

Progress on Electron Counting Rules of Clusters

The equations calculating the number of valence electrons on the boranes and heteroboranes are different from other simple condensed clusters such as the condensed organometallics and transition metal clusters. The equations calculating the number of valence electrons greatly differ between the condensed boranes and heteroboranes with the non-condensed boranes and heteroboranes too. These equations calculating the number of valence electrons on simple condensed clusters are all derived from the noble gas rule and Wade’s rule in the theory. The noble gas rule and Wade’s rule could be also applied to the high-nuclearity transition metal clusters, the equation details calculating the number of valence electrons is studied. The application ranges of the noble gas rule, Wade’s rule, and 6m+2n electron rule are extended. The calculating results are satisfying comparing with actual facts.

Recent Advances in First‐Row Transition Metal Clusters for Photocatalytic Water Splitting

AbstractWater splitting based on first‐row transition metal (3d) photocatalysts is a cost‐effective technology for the conversion of abundant solar energy into useful energy on a large scale. The catalytic core of photosynthetic enzymes is a cubic CaMn4O5 cluster. Illuminated by natural photosynthesis, artificial solar water splitting photocatalysts composed of metal clusters are now being designed and tested. Ideally, such photocatalysts composed of atomically precise metal clusters with regular crystal structures are promising model catalysts that can be used to study structure–performance relationships. Recent advances based on metal cluster designs have improved our understanding of photoinduced charge separation and catalytic water redox reactions. This Minireview summarizes the recent advances in 3d metal cluster photocatalysts with well‐defined structures for photocatalytic water splitting and focuses on different clusters with tunable structures that are capable of achieving better photocatalytic properties.

Interaction of carbon monoxide with doped metal clusters

Highlight of experimental and computational studies about the interaction of CO with transition and coinage metal clusters, particularly discussing the influence of dopant atoms.

Band gap and magnetic engineering of penta-graphene via adsorption of small transition clusters.

Penta-graphene has been intensively studied owing to its superior properties such as being an intrinsic semiconductor and having two dimensional stability. However, the nonmagnetic character makes it difficult for straightforward application in the fields of spintronic or information storage. Here, the deposition effects of Fe-group and Co-group transition metal (TM = Fe, Ru, Os; Co, Rh, Ir) clusters on the penta-graphene have been systemically investigated for their electronic and magnetic properties by using density functional theory (DFT) calculations. We found that the TM deposition stability on penta-graphene is overall greater than that on graphene. Importantly, TM adatoms (adclusters) not only change penta-graphene from being a wide band-gap semiconductor to a narrow band-gap semiconductor, but also introduce large magnetic moments into systems simultaneously. It is worth noting that the Ir5 cluster on penta-graphene is a good candidate for realizing the magnetic half-metallic materials. Our calculated results demonstrate that adatoms can exhibit large out-of-plane magnetic anisotropy energy, e.g., the Os adatom presents the largest value of 113 meV. Therefore, from the application point of view, magnetic functionalization of penta-graphene by TM clusters facilitates its application as a spintronic device or a high-density information storage device.

Investigation of the Magnetic and Electronic Properties of Copper Nanocluster Cu14 Contaminated with Fe, Ni and Co

We have presented density functional calculations of the electronic structures and magnetic properties of bimetallics nanoclusters Cu14-nMn (n=1-3) (M=Fe, Ni and Co) in the FCC crystal structure. For the calculations of the physical properties of the compounds, we have used the full potential linearized augmented plane wave method. The magnetic nature, semiconducting, half metallicity and metalloid of transition metals clusters in the FCC crystal structure are investigated. Results show that studied systems have ferromagnetic properties against Cu14Cluster. It is found that band gap of the clusters decreases with doping of atoms compared to pure cluster Cu14, Particularly for Fe. These calculations show that Cu14 and Cu12Co2 are metals, while Cu13Fe, Cu12Fe2, Cu13Co, Cu11Co3 and Cu11Ni3 are half-metals and Cu11Fe3 and Cu12Ni2 are metalloid. Between these clusters, Cu13Ni is semiconductor. The spin polarization and the magnetic moment of the systems are dependent on number and type of the host transition metal atoms. The Cu13Ni has maximum spin polarization and stability. These results provide a new candidate for applications this series of compounds as dilute magnetic clusters and half-metal in spintronic devices.

Heavy chalcogenide-transition metal clusters as coordination polymer nodes.

While metal–oxygen clusters are widely used as secondary building units in the construction of coordination polymers or metal–organic frameworks, multimetallic nodes with heavier chalcogenide atoms (S, Se, and Te) are comparatively untapped. The lower electronegativity of heavy chalcogenides means that transition metal clusters of these elements generally exhibit enhanced coupling, delocalization, and redox-flexibility. Leveraging these features in coordination polymers provides these materials with extraordinary properties in catalysis, conductivity, magnetism, and photoactivity. In this perspective, we summarize common transition metal heavy chalcogenide building blocks including polynuclear metal nodes with organothiolate/selenolate or anionic heavy chalcogenide atoms. Based on recent discoveries, we also outline potential challenges and opportunities for applications in this field.

Ligand architecture for triangular metal complexes: a high oxidation state Ni3 cluster with proximal metal arrangement.

A new multidentate tetraanionic ligand platform for supporting trinuclear transition metal clusters has been developed. Two trisphenoxide phosphinimide ligands bind three Ni centers in a triangular arrangement. The phosphinimide donors bridge in μ3 fashion and the phenoxides complete a pseudo-square planar coordination sphere around each metal center. Electrochemical studies reveal two pseudo-reversible oxidation events at notably low potentials (-0.80 V and +0.05 V). The one electron oxidized species was characterized structurally, and it is assigned as a NiIII-containing cluster.

On the influence of exact exchange on transition metal superatoms.

The electronic structure of A7C (A = Hg, Pd, V, Cr, Mn, Fe, Ni, Cu; C = 0, ±1, ±2) clusters has been determined using density functional theory methods. The A7C (A = Hg, Pd, Cr, Cu; C = 0, ±1, ±2) clusters all conform to the existing superatomic model, with a sufficiently stabilised local structure to prevent perturbation upon the introduction of exact exchange to the exchange correlation functional. For the A7C (A = Mn, Fe, Ni; C = 0, ±1, ±2) clusters the incorporation of exact exchange separates the atomic s- and d-electrons, leading to a net increase in the number of superatomic electrons. Conversely the incorporation of exact exchange into the exchange correlation functional decreases the number of superatomic electrons for the V7C (C = 0, ±1, ±2) clusters, owing to the radial extension of the d-orbitals influencing their ability to contribute into superatomic shells.

Investigation of the Magnetic and Electronic Properties of Copper Nanocluster Cu14 Contaminated with Fe, Ni and Co

We have presented density functional calculations of the electronic structures and magnetic properties of bimetallics nanoclusters Cu14-nMn (n=1-3) (M=Fe, Ni and Co) in the FCC crystal structure. For the calculations of the physical properties of the compounds, we have used the full potential linearized augmented plane wave method. The magnetic nature, semiconducting, half metallicity and metalloid of transition metals clusters in the FCC crystal structure are investigated. Results show that studied systems have ferromagnetic properties against Cu14Cluster. It is found that band gap of the clusters decreases with doping of atoms compared to pure cluster Cu14, Particularly for Fe. These calculations show that Cu14 and Cu12Co2 are metals, while Cu13Fe, Cu12Fe2, Cu13Co, Cu11Co3 and Cu11Ni3 are half-metals and Cu11Fe3 and Cu12Ni2 are metalloid. Between these clusters, Cu13Ni is semiconductor. The spin polarization and the magnetic moment of the systems are dependent on number and type of the host transition metal atoms. The Cu13Ni has maximum spin polarization and stability. These results provide a new candidate for applications this series of compounds as dilute magnetic clusters and half-metal in spintronic devices.

Ab initio investigation of the atomistic descriptors in the activation of small molecules on 3d transition-metal 13-atom clusters: The example of H2, CO, H2O, and CO2.

The identification of the most important descriptors that drive the activation CO2 on transition-metal (TM) catalysts is a crucial step toward the conversion of CO2 into value-added chemicals; however, our atomistic understanding is far from satisfactory. Thus, aiming at the potential use of TM clusters in the conversion of CO2, we report density functional theory calculations of CO2, CO, H2O, and H2 adsorption on TM13 clusters (TM = Fe, Co, Ni, and Cu). Among the descriptors to evaluate the activation of the studied molecules, we found that the bond lengths increase, angles decrease, and their energetic variations upon the adsorption are the most important ones. From the structural response in anionic gas-phase molecules, the charge transfer toward CO2 and CO is pointed as relevant in their activation, and our results and analyses suggest that the adsorption on 3d TM13 clusters promote this charge donation process, decreasing in the order Fe13 > Co13 > Ni13 > Cu13. For CO2 and CO on Cu13, the activation was observed for highest energy configurations, indicating that is necessarily an additional driving force to occur the molecular activation on this material. Also, energetic parameters, adsorption energy, and interaction energy indicated that the strength of the adsorption is not necessarily proportional to the activation; it is difficult to point out these parameters as descriptors. Our results also provide interesting insights about steps of the CO2 reduction mechanism within the context of the modified Fischer-Tropsch synthesis.

Why do Bimetallic Clusters have more Chemical Reactivity? Study the VnNim (2 ≤ n + m ≤ 6) Clusters as the Nano Species

This article gives you proof that bimetallic transition metal clusters with the difference in electronegativity are better catalysts than monoatomic one. To prove this fact, a study of ethylene adsorption on bimetallic clusters vanadium-nickel VnNim (2≤n+m≤6) has been demonstrated. Our result shows that hardness has a quite good linear correlation with the non-Lewis of VnNi (n=1-5) cluster (R2=0.99). This finding is important, because this is the first time in literature that presents an orbital explanation for hardness. It is possible to see the results of both nickel doped in vanadium cluster and also vanadium doped in nickel cluster. The maximum interaction for these species is for one nickel substituted alloy, VnNi (n=1-5). This finding corresponds to the lowest energy gap between HOMO of bimetallic clusters and LUMO of ethylene, according to Fukui equation of reactivity. A successful demonstration has been performed by extrapolation of theoretical results to predict the best mixing of two metals which reveals that V8Ni cluster is the best that is in accordance with the experimental results of mixing vanadium with nickel as catalysis in industry. We have also demonstrated that the larger bimetallic cluster has more conductivity and reactivity which is the demonstration of nano character.

Temperature dependence of spherical electron transfer in a nanosized [Fe14] complex

The study of transition metal clusters exhibiting fast electron hopping or delocalization remains challenging, because intermetallic communications mediated through bridging ligands are normally weak. Herein, we report the synthesis of a nanosized complex, [Fe(Tp)(CN)3]8[Fe(H2O)(DMSO)]6 (abbreviated as [Fe14], Tp−, hydrotris(pyrazolyl)borate; DMSO, dimethyl sulfoxide), which has a fluctuating valence due to two mobile d-electrons in its atomic layer shell. The rate of electron transfer of [Fe14] complex demonstrates the Arrhenius-type temperature dependence in the nanosized spheric surface, wherein high-spin centers are ferromagnetically coupled, producing an S = 14 ground state. The electron-hopping rate at room temperature is faster than the time scale of Mössbauer measurements (<~10−8 s). Partial reduction of N-terminal high spin FeIII sites and electron mediation ability of CN ligands lead to the observation of both an extensive electron transfer and magnetic coupling properties in a precisely atomic layered shell structure of a nanosized [Fe14] complex.

Understanding supported noble metal catalysts using first-principles calculations.

Heterogeneous catalysis on supported and nonsupported nanoparticles is of fundamental importance in the energy and chemical conversion industries. Rather than laboratory analysis, first-principles calculations give us an atomic-level understanding of the structure and reactivity of nanoparticles and supports, greatly reducing the efforts of screening and design. However, unlike catalysis on low index single crystalline surfaces, nanoparticle catalysis relies on the tandem properties of a support material as well as the metal cluster itself, often with charge transfer processes being of key importance. In this perspective, we examine current state-of-the-art quantum-chemical research for the modeling of reactions that utilize small transition metal clusters on metal oxide supports. This should provide readers with useful insights when dealing with chemical reactions on such systems, before discussing the possibilities and challenges in the field.

Jahn-Teller and Pseudo Jahn-Teller Effects: Influences on the Electronic Structures of Small Transition, Main Group and Mixed Metal Clusters

The present review article focuses on the impact of the Jahn-Teller effect (JTE) including hidden JTE and pseudo JTE on the ground and low-lying electronic structures of small transition, main group, and mixed metal clusters. The discussions are based on the results acquired from the quantum chemical analysis involving complete active space multiconfiguration self-consistent field (CASMCSCF or CASSCF) together with multireference singles and doubles configuration interaction (MRSDCI) theories. Related computational results from density functional (DFT) and coupled cluster (CC) theories, and the available experimental evidences on the JT-distorted structures are also included for comparative analysis. The role of the relativistic effects on several heavy metal clusters is discussed in detail, since these effects could lead to either enhancement or the quenching of the JTE. The final section of the review manifests the JT-distortion of several mixed metal clusters of icosahedral symmetry and they are explained through a much simpler shell structure (jellium) model.

Tools for Prescreening the Most Active Sites on Ir and Rh Clusters toward C-H Bond Cleavage of Ethane: NBO Charges and Wiberg Bond Indexes.

B3LYP calculations were carried out to study the insertion of iridium (Ir) and rhodium (Rh) clusters into a C–H bond of ethane, which is often the rate-limiting step of the catalytic cycle of oxidative dehydrogenation of ethane. Our previous research on Ir catalysis correlates the diffusivity of the lowest unoccupied molecular orbital of the Ir clusters and the relative activities of the various catalytic sites. The drawback of this research is that the molecular orbital visualization is qualitative rather than quantitative. Therefore, in this study on C–H bond activation by the Ir and Rh clusters, we conducted analyses of natural bond orbital (NBO) charges and Wiberg bond indexes (WBIs), both of which are not only quantitative but also independent of the basis sets. We found strong correlation between the NBO charges, the WBIs, and the relative activities of the various catalytic sites on the Ir and Rh clusters. Analyses of the NBO charges and the WBIs provide a fast and reliable means of prescreening the most active sites on the Ir and Rh clusters and potentially on other similar transition-metal clusters that activate the C–H bonds of ethane and other light alkanes.

Supramolecular Anchoring of Octahedral Molybdenum Clusters onto Graphene and Their Synergies in Photocatalytic Water Reduction.

Dihydrogen (H2) production from sunlight should become one of the most important energy production means in the future. To reach this goal, low-cost and efficient photocatalysts still need to be discovered. Here we show that red near-IR luminescent metal cluster anions, once combined with pyrene-containing cations, are able to photocatalytically produce molecular hydrogen from water. The pyrene moieties act simultaneously as energy transmitters and as supramolecular linkers between the cluster anions and graphene. This association results in a hybrid material combining the emission abilities of pyrene and cluster moieties with the electronic conduction efficiency of graphene. Hydrogen evolution reaction (HER) studies show that this association induces a significant increase of H2 production compared to that produced separately by clusters or graphene. Considering the versatility of the strategy described to design this photocatalytic hybrid material, transition-metal clusters are promising candidates to develop new, environmentally friendly, and low-cost photocatalysts for HER.