Privileged metal cluster complexes
Gas-phase reactions of rhodium and platinum clusters with common ligand molecules in forming metal complexes, showing privileged cluster complexes with adaptive electron delocalization.
Chemistry↗
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Discovery of correlated electron molecular orbital materials using graph representations
Correlated electron molecular orbital (CEMO) materials host emergent electronic states built from molecular orbitals localized over clusters of transition metal ions yet have historically been discovered sporadically and generally been treated as isolated case studies. Here we establish CEMO materials as a systematically discoverable class and introduce a graph-based framework to identify, classify, and organize transition-metal cluster motifs in inorganic solids. Starting from crystal structures in the Materials Project, we construct transition metal connectivity graphs, extract cluster motifs using a bond-cutting algorithm, and determine cluster point groups, effective cluster sublattice dimensionality, and translational symmetry. Applying this approach in a high-throughput screen of 34,548 compounds yields 5,306 cluster-containing materials, including 2,627 stable or metastable compounds with isolated clusters and 984 materials featuring mixed-metal clusters. The resulting dataset reveals symmetry and element dependent trends in cluster formation. By integrating cluster classification with flat band lattice topology and battery-relevant information, we provide further relevant information to multiple scientific communities. The accompanying open dataset, Cluster Finder software, and interactive web platform enable systematic exploration of cluster driven electronic phenomena and establish a general pathway for discovering correlated quantum materials and functional materials with cluster-based or extended metal-metal bonding in inorganic solids.
Akhond, Md. Rajbanul [Department of Chemistry, 800↗
The Many-Body Expansion for Metals: II. Nonadditive Terms in Clusters Composed of Metals with n s 1 , n s 2 , and n s 2 p 1 Configurations
The many-body expansion (MBE) was applied to homometallic and heterometallic trimers of metals with ns 1 , ns 2 , and ns 2 p 1 configurations to investigate its convergence, the magnitude and nature (stabilizing/destabilizing) of the individual terms and seek an understanding of their variation across the different families of clusters. In particular, we examined the series of alkali metals (Li 3 , Na 3 , K 3 , Li 2 Na, LiNa 2 ), alkali metal borides (Li 2 B and LiB 2 ), and alkaline earth metals (Be 3 , Be 2 Mg, BeMg 3 , and Mg 3 ) trimers, as well as sodium clusters Na n , n = 2–5. Here, we found that there is no uniform contribution (stabilizing or destabilizing) across the series in the different families of trimers. For instance, the 2-B term stabilizes the ground states of the Na 3 (doublet), Na 4 (singlet), and Na 5 (doublet) clusters, and the 3-B term destabilizes them; however, the opposite holds for the quartet state of the Li 3 , Li 2 Na, LiNa 2 , and Na 3 clusters (destabilizing 2-B, stabilizing 3-B). Substituting Li with B in the quartet state of Li 3 results in a significant reduction of the 3-B term amounting to 16% (Li 2 B) and 5% (LiB 3 ) of the binding energy. On the contrary, the ground states of the alkaline earth metal clusters (Be 3 , Be 2 Mg, BeMg 3 , and Mg 3 ) are stabilized by the 3-B term, while the 2-B term destabilizes them. Overall, we find that the 3-B terms significantly stabilize the high-spin multiplicity states of the ns 1 configurations and the low-spin states of the ns 2 configurations. Finally, as the size of the metal increases, the contribution of the 3-B term to the binding energy decreases due to the longer metal–metal bond distances.
Alkali metals↗
Molecular orbital symmetry-driven trimer formation in Kagome correlated electron materials
Correlated electron materials with molecular orbital states extending over transition metal clusters can host multiferroicity, spin frustration, and unconventional insulating phases. However, the fundamental criteria that govern cluster formation and stability remain unclear. Here, we identify a symmetry, correlation, and electron-filling-driven criteria that stabilize triangular metal trimers in materials displaying transition metal Kagome patterns. Using density functional theory and chemical bonding analysis, we show that trimer formation emerges when 6–8 electrons occupy molecular orbitals derived from transition metal d-states, achieving near-complete filling of bonding states while avoiding antibonding occupation, and correlations are of intermediate strength. This principle explains the stability of Nb 3 X 8 (X = Cl, Br, I), and more broadly, our findings offer a general design rule to obtain quantum materials with quantum states extended across transition metal clusters.
Kumari, Varsha [Indiana Univ., Bloomington, IN (Un↗
Structure and Synthesizability of Iron–Sulfur Metal–Organic Frameworks
Sulfur-based metal–organic frameworks (MOFs) and coordination polymers (CPs) are an emerging class of hybrid materials that have received growing attention due to their magnetic, conductive, and catalytic properties with potential applications in electrocatalysis and energy storage. In this work, we report a high-throughput virtual screening protocol to predict the synthesizability of candidate metal–sulfur MOFs/CPs by computing the thermodynamically stable structures resulting from a particular combination of metal cluster, linker, cation, and synthetic conditions. Free energies are computed by using all-atom classical mechanical thermodynamic integration. Low-free-energy structures are refined using ab initio density functional theory, and pair distribution functions and powder X-ray diffraction patterns are calculated to complement and guide experimental structure determination. We validate the computational approach by retrospective predictions of the stable structure produced by experimental syntheses, and a subsequent screen predicts Fe 4 S 4 -BDT–TPP as a new thermodynamically stable one-dimensional (1D) CP comprising a redox-active Fe 4 S 4 cluster, a 1,4-benzenedithiolate (BDT) linker, and a tetraphenylphosphonium (TPP) countercation. Furthermore, this material is experimentally synthesized, and the 1D chain structure of the crystal is confirmed using microcrystal electron diffraction. The computational screening pipeline is generically transferable to neutral and ionic MOFs/CPs comprising arbitrary metal clusters, linkers, cations, and synthetic conditions, and we make it freely available as an open source tool to guide and accelerate the discovery and engineering of novel porous materials.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Operando Unveiling of Hydrogen Spillover Mechanisms on Tungsten Oxide Surfaces
Hydrogen spillover is an important process in catalytic hydrogenation reactions, facilitating H 2 activation and modulating surface chemistry of reducible oxide catalysts. This study focuses on the operando unveiling of platinum-induced hydrogen spillover on monoclinic tungsten trioxide (γ-WO 3 ), employing ambient pressure X-ray photoelectron spectroscopy, density functional theory calculations and microkinetic modeling to investigate the dynamic evolution of surface states at varied temperatures. At room temperature, hydrogen spillover results in the formation of W 5+ and hydrogen intermediates (hydroxyl species and adsorbed water), facilitated by Pt metal clusters. With increasing temperature, water desorption, reverse hydrogen spillover and surface-to-bulk diffusion of hydrogen atoms compete with each other, leading initially to reoxidation and then further reduction of W atoms in the near-surface. The combined experimental results and simulations provide a comprehensive understanding of the mechanisms underlying hydrogen interaction with reducible metal oxides, lending insights of relevance to the design of enhanced hydrogenation catalysts.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Trafficking of a nitrogenase FeMo-cofactor assembly intermediate
The maturation of the unique FeMo-cofactor of molybdenum nitrogenase is a multistep process requiring the sequential action of a series of maturase complexes. As a final step, the NifEN complex forms FeMo-cofactor from the precursor NifB-co, also called L-cluster, through replacement of an apical iron ion by molybdenum and the attachment of an organic homocitrate ligand. NifB-co is delivered by a small cofactor chaperone, NifX, and initially bound near the surface of the maturase NifEN. Here, we report high-resolution cryo-electron microscopy structures of NifEN in complex with NifX, showing NifB-co binding to NifEN in full detail, capturing both interacting partners in the act of cluster transfer. In a dynamic transfer complex, the large metal cluster is coordinated by single residues from both NifEN and NifX. In silico studies concur with these structures but suggest a third, internal conversion site where cluster maturation likely takes place.
metalloproteins↗
Electrochemical production of H 2 O 2 on palladium-based clusters driven by metal–support interaction
Utilizing palladium (Pd) clusters as active sites offers a promising route to minimize noble metal consumption in electrochemical hydrogen peroxide (H 2 O 2 ) production. In this work, we present a synthesis approach for anchoring Pd-based clusters onto carbon-supported CeO 2 nanosubstrates to enable efficient H 2 O 2 generation via the two-electron oxygen reduction reaction (ORR) pathway. By systematically adjusting Pd loading, we evaluated its impact on H 2 O 2 yield and production rate. The catalyst with the lowest Pd content (0.027 wt%) exhibited outstanding performance, achieving 97% H 2 O 2 selectivity, 94.2 faradaic efficiency at 0.7 V vs. RHE, and a peak production rate of 195.8 mol g Pd −1 h −1 . A formulation containing 0.35 wt% Pd delivered a peak ORR mass activity nearly three times as high as that of commercial 10 wt% Pd/C, while retaining comparable electrochemical stability. These enhancements are attributed to synergistic effects among isolated PdO clusters, CeO 2 nanocrystals, and the conductive carbon support, which together facilitate oxygen adsorption and promote the two-electron ORR pathway. Analysis after accelerated durability testing further revealed a tendency toward cluster agglomeration and mass transfer from smaller to larger nanocrystals, indicative of a coarsening mechanism. Overall, this study underscores the promise of low-Pd PdO–CeO 2 –carbon hybrid catalysts for scalable and efficient H 2 O 2 electrosynthesis, while highlighting stability as a critical area for future improvement.
36 MATERIALS SCIENCE↗
Developing Lanthanide-Nitrate Cluster Chemistry toward Rare Earth Separations
Nitrate-decorated hexamers with a [Ln 6 (μ 6 -O)(μ 3 –OH) 8 ] 8+ core have been reported for nearly every lanthanide ion and are used as precursors for the assembly of functional metal–organic frameworks. Yet, few studies have examined the correlation between the solution and solid-state species, and the formation of mixed-metal clusters. Toward this end, a series of homo- and heterometal lanthanide nitrate hexamers was prepared via pH adjustment of aqueous lanthanide nitrate solutions. Examination of the homometallic europium solutions using Small Angle X-ray Scattering and nESI-MS showed that lower order complexes dominate lanthanide speciation in nitrate media. Yet, powder X-ray diffraction data of the precipitated phase confirmed the formation of [Ln 6 (μ 6 -O)(μ 3 -OH) 8 (NO 3 ) 6 (H 2 O) 12 ]·2(NO 3 )·n(H 2 O), Ln 6 , for Ln = Eu and Tb. For heterometal systems, analysis of the solid-state product by ICP–MS showed the selective incorporation of the heavier rare earths into Ln 6 . Selectivity was quantified by calculating an average separation factor, which is defined as the ratio of recovery factors of both metals. Further examination of the luminescence behavior of mixed metal [Tb 6–x Eu x (μ 6 -O)(μ 3 -OH) 8 (NO 3 ) 6 (H 2 O) 12 ]·2(NO 3 )·n(H 2 O), with x = 1.1–3.6, showed that the relative intensities of the peaks at 489 nm (terbium, 5 D 4 → 7 F 6 ) and 690 nm (europium, 5 D 0 → 7 F 4 ) trend with the percent incorporation of europium and terbium into the cluster.
anions↗
Tailoring Cu-Zr gradient nanoglass structures: Influence of nanoparticle size and cooling rates on glass-glass interfaces
The study of gradient nanoglasses (GNGs) has gained attention due to their unique mechanical properties and potential applications in advanced materials. This study employs molecular dynamics simulations to synthesize a GNG using Cu-Zr metallic glass nanoparticles (NPs) sized from 3 to 15 nm. The NPs were produced by melting and quenching metallic clusters at a relatively slow quench rate of 10 9 K/s. The synthesis of GNG is elucidated along with the characterization of its heterogeneous metallic glass nanostructure. A seamless GNG structure is formed through cold compression of Cu 64 Zr 36 amorphous NPs of varying sizes. The influence of NP size on the GNG structure is investigated, utilizing deeply relaxed NPs, which exhibit a characteristic Cu segregation pattern on their surfaces. The results highlight an increase in structural heterogeneity due to heterogeneous mass transport and the development of local composition and density variations caused by Cu segregation at glass-glass interfaces (GGIs). A reduction in NP size is correlated with decreased Cu atomic displacements and local density at GGIs, suggesting that larger NPs may produce stronger GGIs. This research presents a novel methodology for synthesizing heterogeneous metallic glasses, demonstrating the capacity to control and customize nanostructure heterogeneity through the manipulation of NP sizes and cooling rates. Furthermore, these findings enhance our understanding of structural evolution during nanoglass synthesis and lay the foundation for further exploration in nanomaterial synthesis and characterization.
36 MATERIALS SCIENCE↗
Activation and electrochemical reduction of carbon dioxide by transition metal atom-doped copper clusters
Doping transition metals in Cu 13 clusters enhance CO 2 reduction by altering electronic and magnetic properties, lowering overpotentials by ∼20%.
Mohanta, Manish Kumar [Department of Physics, Virg↗
Au147(SPh)30(PPh3)12: A Geometrically Closed, but Electronically Open Triple‐Shell Icosahedral Gold Cluster and its Geometrically Open Counterpart
The aesthetic platonic solids have been known since ancient times, and the structure of all five platonic solids is also found in chemical compounds. While gold sub-nanometer clusters and gold nanoparticles with an icosahedral structure have been known for a long time to exist, a multi-shell icosahedral gold cluster at the intermediate size between 13 and thousands of atoms has been elusive. Here we present the synthesis and crystallographic characterization of the first triple-shell icosahedral metal cluster, Au147(SPh)30(PPh3)12 1. The gold core in 1 is stabilized by phosphines and thiolates, but surprisingly no staple motifs are formed. A second cluster, Au146(SPh)30(PPh3)12 2, cocrystallizes and is identified as having a closed electronic shell but can be considered as a geometrically open pendant of 1. The unique clusters are characterized experimentally by EDX, UV/vis, DLS, and EPR and theoretically by quantum chemical calculations.
Strienz, Markus↗
Introducing metal–sulfur active sites in metal–organic frameworks via post-synthetic modification for hydrogenation catalysis
Metal–sulfur active sites play a central role in catalytic processes such as hydrogenation and dehydrogenation, yet the majority of active sites in these compounds reside on the surfaces and edges of catalyst particles, limiting overall efficiency. Here we present a strategy to embed metal–sulfur active sites into metal–organic frameworks (MOFs) by converting bridging or terminal chloride ligands into hydroxide and subsequently into sulfide groups through post-synthetic modification. We apply this method to two representative MOF families: one featuring one-dimensional metal–chloride chains and another containing discrete multinuclear metal clusters. Crystallographic and spectroscopic analyses confirm structural integrity and sulfide incorporation, and the transformation is monitored by in situ total scattering methods. The sulfided MOFs display enhanced catalytic activity in the selective hydrogenation of nitroarenes using molecular hydrogen. Density functional theory calculations indicate that sulfur incorporation promotes homolytic metal–ligand bond cleavage and facilitates H 2 activation. This work establishes an approach to construct MOFs featuring accessible metal–sulfide sites.
Catalyst synthesis↗
Monodisperse Cu Nanoparticles Supported on a Versatile Metal–Organic Framework for Electrocatalytic Reduction of CO 2
Rare-earth metal–organic frameworks (REMOFs) based on polynuclear metal clusters are an emerging class of materials that have shown promise for CO 2 capture and conversion. Here, in this work, copper nanoparticles (CuNPs) were successfully installed on a cluster-based Y(III) MOF to yield a composite material, CuNP-Y-TBAP. The abundance of Cu binding sites on the Y(III) clusters allowed a remarkably high Cu loading to be achieved, and electron microscopy demonstrated that the MOF-supported CuNPs are exceptionally small and monodisperse. CuNP-Y-TBAP was found to be an active heterogeneous catalyst for electrochemical reduction of CO 2 , yielding CO and CH 4 as the primary CO 2 reduction products.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Structure of human MUTYH and functional profiling of cancer-associated variants reveal an allosteric network between its [4Fe-4S] cluster cofactor and active site required for DNA repair
Abstract MUTYH is a clinically important DNA glycosylase that thwarts mutations by initiating base-excision repair at 8-oxoguanine (OG):A lesions. The roles for its [4Fe-4S] cofactor in DNA repair remain enigmatic. Functional profiling of cancer-associated variants near the [4Fe-4S] cofactor reveals that most variations abrogate both retention of the cofactor and enzyme activity. Surprisingly, R241Q and N238S retained the metal cluster and bound substrate DNA tightly, but were completely inactive. We determine the crystal structure of human MUTYH bound to a transition state mimic and this shows that Arg241 and Asn238 build an H-bond network connecting the [4Fe-4S] cluster to the catalytic Asp236 that mediates base excision. The structure of the bacterial MutY variant R149Q, along with molecular dynamics simulations of the human enzyme, support a model in which the cofactor functions to position and activate the catalytic Asp. These results suggest that allosteric cross-talk between the DNA binding [4Fe-4S] cofactor and the base excision site of MUTYH regulate its DNA repair function.
Science & Technology - Other Topics↗
Three rate-determining protein roles in photosynthetic O 2 -evolution addressed by time-resolved experiments on genetically modified photosystems
Light-driven water splitting by plants, algae and cyanobacteria is pivotal for global bioenergetics and biomass formation. A manganese cluster bound to the photosystem II proteins catalyzes the complex reaction at high rate, but the rate-determining factors are insufficiently understood. Here we trace the oxygen-evolution transition by time-resolved polarography and infrared spectroscopy for cyanobacterial photosystems genetically modified at two strategic sites, complemented by computational chemistry. Our results highlight three rate-determining roles of the protein environment of the metal cluster: acceleration of proton-coupled electron transfer, acceleration of substrate-water insertion after O 2 -formation, and balancing of rate-determining enthalpic and entropic contributions. Whereas in general the substrate-water insertion step may be unresolvable in time-resolved experiments, here it likely becomes traceable because of deceleration by genetic modification. Our results may stimulate new time-resolved experiments on substrate-water insertion in photosynthesis, clarification of enthalpy-entropy compensation in enzyme catalysis, and knowledge-guided development of inorganic catalyst materials.
Bioenergetics↗
Reconstruction and Dissolution of Copper Catalysts during Electrocatalytic Nitrate Reduction
Copper-based electrocatalysts are widely explored for electrochemical nitrate remediation, yet their stability under operating conditions remains poorly understood. While nanoscale and subnanoscale Cu motifs are known to restructure during the nitrate reduction reaction (NO 3 RR), how these transformations translate into irreversible material loss remains unclear. Here, we quantify Cu dissolution during NO 3 RR as a function of catalyst architecture and electrolyte chemistry using two model systems: single-atom Cu (Cu 1 ) and Cu nanoparticles (Cu NP ). Time-resolved leaching measurements, integrated with in situ X-ray absorption spectroscopy (XAS), reveal measurable Cu loss for both catalysts during NO 3 RR. Dissolution is concentrated at the initiation of electrolysis, coinciding with rapid restructuring, and depends strongly on morphology, with Cu NP consistently exhibiting greater Cu loss than Cu 1 . In situ XAS reveals that Cu 1 forms transient metallic clusters under reduction that largely redisperse upon returning to open-circuit voltage, whereas Cu NP undergoes reduction of an oxidized surface layer accompanied by sustained Cu loss during electrolysis. Notably, the presence of nitrate significantly intensifies restructuring and Cu loss, highlighting the critical role of electrolyte composition. Furthermore, these findings establish a direct link between electrochemical restructuring and Cu dissolution, unveiling electrolyte-dependent interactions as key determinants of catalyst durability in electrochemical nitrate conversion.
36 MATERIALS SCIENCE↗
Iron-molybdenum cofactor synthesis by a thermophilic nitrogenase devoid of the scaffold NifEN
The maturation and installation of the active site metal cluster (FeMo-co, Fe 7 S 9 CMo- R -homocitrate) in Mo-dependent nitrogenase requires the protein product of the nifB gene for production of the FeS cluster precursor (NifB-co, [Fe 8 S 9 C]) and the action of the maturase complex composed of the protein products from the nifE and nifN genes. However, some putative diazotrophic bacteria, like Roseiflexus sp. RS-1, lack the nifEN genes, suggesting an alternative pathway for maturation of FeMo-co that does not require NifEN. In this study, the Roseiflexus NifH, NifB, and apo-NifDK proteins produced in Escherichia coli are shown to be sufficient for FeMo-co maturation and insertion into the NifDK protein to achieve active nitrogenase. The E. coli expressed NifDK RS contained P-clusters but was devoid of FeMo-co (referred to as apo-NifDK RS ). Apo-NifDK RS could be activated for N 2 reduction by addition of preformed FeMo-co. Further, it was found that apo-NifDK RS plus E. coli produced NifB RS and NifH RS were sufficient to yield active NifDK RS when incubated with the necessary substrates (homocitrate, molybdate, and S -adenosylmethionine [SAM]), demonstrating that these proteins can replace the need for NifEN in maturation of Mo-nitrogenase. The E. coli produced NifH RS and NifB RS proteins were independently shown to be functional. The reconstituted NifDK RS demonstrated reduction of N 2 , protons, and acetylene in ratios observed for Azotobacter vinelandii NifDK. These findings reveal a distinct NifEN-independent pathway for nitrogenase activation involving NifH RS , NifB RS , and apo-NifDK RS .
Payá-Tormo, Lucía↗