Trimetallic Clusters Research Articles

Trimetallic FeNiCu Atomic Clusters Supported on Carbon Matrix: Highly Active Catalysts for C3H6-SCR of NO.

C3H6-SCR denitrification technology faces catalyst deactivation problems and low catalytic performance at medium-low temperatures. This study utilized the intermetallic synergies to prepare atomic cluster catalysts (FeNiCu/NC) by anchoring Fe-Ni-Cu on a carbon matrix to enhance the C3H6-SCR performance at medium-low temperatures. The synergistic effect of the Fe-Ni-Cu is reflected in the differences in the physicochemical properties of the catalysts, which is proved by several characterization techniques. Results showed that the FeNiCu/NC catalyst had a larger surface area (541.4 m2/g) and there were no metal oxides on the surface of the catalyst but abundant defective sites that anchored Fe/Ni/Cu atoms through N atoms to form M-Nx active sites and atomic clusters. The hollow carbon morphology provides sufficient active sites for C3H6-SCR. The coordination environments of active sites were M-Nx-C, Fe2/FeCu2/FeNi2, Ni3/NiFe/NiCu2, and Cu4/CuFe2/CuNi2, where the synergistic action of trimetal leads to the presence of Fe-Ni-Cu-Nx-C. The synergistic action of the Fe-Ni-Cu significantly improved the C3H6-SCR performance at medium-low temperatures. The FeNiCu/NC exhibited an 81% NO conversion at 150 °C under 2% O2, 15% and 20% higher than FeNi/NC and FeCu/NC catalysts, respectively. Even at 4% O2, the FeNiCu/NC catalyst was active to remove 78% NO and achieve a 93% N2 selectivity at 150 °C and maintained a 100% NO conversion at 300-425 °C. The DRIFTS results demonstrated that NO and C3H6 could combine with active O at metal cluster, M-Nx, or defective oxygen sites to produce various intermediate species, wherein acetates and nitrates were the main active intermediates. Based on the DRIFTS results, a reaction pathway for C3H6-SCR over the FeNiCu/NC catalyst was proposed.

Osmium and ruthenium carbonyl clusters containing arsine, arsenide, and arsinidene ligands

The reactivity of trimetallic clusters [Os3(CO)10(NCMe)2], [M3(CO)10(µ-dppm)] [M = Os, Ru; dppm = bis(diphenylphosphino)methane] and [Os3(CO)8{µ3-Ph2PCH2PPh(C6H4)}(µ-H)] with triphenylarsine (AsPh3) has been investigated. The labile [Os3(CO)10(NCMe)2] reacts with AsPh3 at room temperature to give 1,2-[Os3(CO)10(AsPh3)2] (1) in good yield. Thermolysis of 1 in refluxing toluene affords the known clusters [Os3(CO)11(AsPh3)] (2), [Os3(CO)9(µ-AsPh2)(µ3,η2-C6H4)(µ-H)] (3) and [Os3(CO)7(µ-AsPh2)2(µ3,η2-C6H4)] (4). Treatment of [Os3(CO)10(µ-dppm)] with AsPh3 in refluxing toluene affords [Os3(CO)9(AsPh3)(µ-dppm)] (5) as the major product together with [Os3(CO)7(AsPh3){µ3-Ph2PCH2PPh(C6H4)}(µ-H)] (6). Control experiment shows that 5 is a precursor of 6 as the former converts to the latter under similar experimental conditions. The same reaction affords 5 as the sole product when it is carried out in refluxing benzene. Cluster 5 and 6 can also be obtained in similar yield by treating [Os3(CO)8{µ3-Ph2PCH2PPh(C6H4)}(µ-H)] with AsPh3 at room temperature. On the other hand, the reaction of [Ru3(CO)10(µ-dppm)] with AsPh3 in refluxing toluene furnishes only [Ru4(CO)8(µ-CO)(μ4-AsPh)(µ4,η2-C6H4)(µ-dppm)] (7) in low yield. Cluster 7 can also be obtained by heating [Ru3(CO)9(AsPh3)(µ-dppm)] in refluxing toluene. It contains a phenylarsinidene and a benzyne ligands that were formed by AsC bond cleavage during the reaction. The molecular structures of all the new products have been established by X-ray crystallography.

Mechanism study of trimetallic single-cluster catalysts loaded on graphdiyne for highly efficient oxygen-reduction reactions

Single-cluster catalysts (SCCs) have become a research hotspot due to their abundant active sites and tunable interatomic electronic structure, demonstrating excellent catalytic properties. However, the diversity of metal species in SCCs leads to unclear intrinsic activity toward metals and interaction between different metal species. In this manuscript, the impact of a series of precious metal-based (Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au) trimetallic SCCs loaded on graphdiyne (UxVyWz@GDY) on the performance of the oxygen reduction reaction (ORR) is investigated using first-principles. The results show that the 18 holes of graphdiyne (GDY) efficiently achieve uniform doping of trimetallic clusters. In the UxVyWz@GDY structure, Pt3@GDY, Pt2Pd@GDY, and AuPdPt@GDY displayed high thermodynamic limit potentials near the top of the volcano plot at 0.79 eV, 0.80 eV, and 0.82 eV, respectively. These catalysts also show low overpotentials of 0.44 V, 0.43 V and 0.50 V, respectively. Deeper scrutiny of the interaction mechanism between *OH and the catalytic sites on Pt3@GDY, Pt2Pd@GDY, and AuPdPt@GDY unveils the pivotal role of electron transfer and intermetallic interactions in modulating the d-band center. Notably, the observed left shift of the d-band center in these catalysts, leading to the generation of more electron-deficient centers, effectively mitigates the issue of over-absorption between *OH and metal active sites, thereby significantly enhancing *OH desorption. This work provides inspiration for the efficient design of trimetallic SCCs.

Metal-Organic Frameworks for Enhanced Hydrogen Generation from Syngas: A Density Functional Theory Approach.

Although methane poses environmental concerns, it is employed in hydrogen production processes such as steam-methane reforming (SMR), which has an issue of by-products released. Initiatives are being pursued to address CO and CO2 emissions using carbon capture methods, with the goal of minimizing environmental harm while improving pure hydrogen generation from syngas. In this study, porous coordination network (PCN-250) has been studied for its selective adsorption property towards CO, CO2 and H2O as syngas mixture to obtain pure hydrogen. For this purpose, the trimetallic cluster node Fe2M (where Fe2 represents the 3+ oxidation state and M is Cr(II), Mn(II), Fe(II), Co(II), Ni(II), and Zn(II)) has been considered. Fe(III) in combination with metal atoms like Cr(II), Co(II), or Ni(II) has been found to exhibit enhanced adsorption properties towards CO, CO2 and H2O. The molecule with the strongest interaction was found to be H2O over Fe(III)2Zn(II) cluster and weakest interaction was found between H2 and Fe(III)2Ni(II). Charge transfer, natural bond orbital (NBO) and spin density analyses reveal the electronic structural properties of this combination, leading to enhanced adsorption of CO and CO2.

When the Ferrocene Analogy Breaks Down: Metallocene Transmetallation Chemistry

AbstractFerrocene 1 and its dianionic Fe(bis)(dicarbollide) analogue 2 are classical compounds that display unusual stability. These compounds are not known to undergo transmetallation chemistry of the Fe‐center and have been used extensively as chemical building blocks with consistent integrity. In this manuscript we describe the preparation of a charge compensated Fe(bis)(dicarbollide) species 3 Fe and its unprecedented transmetallation chemistry to Ir. Such reactions are hitherto unknown for any transition metal metallocene or metallacarborane complex. Additionally, we show that 3 Fe can be deprotonated to afford the corresponding bis(NHC) Li‐carbenoid 5 that also displays unique reactivity. When 5 is reacted with [Ir(COD)Cl]2 it also undergoes a rapid transmetallation of the ferrocene “like” core to afford 6 but with the added twist that the Li‐carbenoid moiety stays intact and does not transmetalate. However, when 6 is subsequently treated with CuCl, the Li‐carbenoid transmetalates to Cu, which allows the controlled formation of the corresponding heterobimetallic Ir/Cu aggregate. Lastly, when Li‐carbenoid 5 is treated directly with CuCl, a double transmetallation occurs from both Fe to Cu and Li‐carbenoid to Cu, resulting in the trimetallic Cu cluster 8. These novel reactions pave the way for new synthetic methods to build complicated polymetallic clusters in a controlled fashion.

When the Ferrocene Analogy Breaks Down: Metallocene Transmetallation Chemistry.

Ferrocene 1 and its dianionic Fe(bis)(dicarbollide) analogue 2 are classical compounds that display unusual stability. These compounds are not known to undergo transmetalation chemistry of the Fe-center and have been used extensively as chemical building blocks with consistent integrity. In this manuscript we describe the preparation of a charge compensated Fe(bis)(dicarbollide) species 3Fe and its unprecedented transmetallation chemistry to Ir. Such reactions are hitherto unknown for any transition metal metallocene or metallacarborane complex. Additionally, we show that 3Fe can be deprotonated to afford the corresponding bis(NHC) Li-carbenoid 5 that also displays unique reactivity. When 5 is reacted with [Ir(COD)Cl]2 it also undergoes a rapid transmetalation of the ferrocene "like" core to afford 6 but with the added twist that the Li-carbenoid moiety stays intact and does not transmetalate. However, when 6 is subsequently treated with CuCl the Li-carbenoid transmetalates to Cu, which allows the controlled formation of the corresponding heterobimetallic Ir/Cu aggregate. Lastly, when Li-carbenoid 5 is treated directly with CuCl, a double transmetallation occurs from both Fe to Cu and Li-carbenoid to Cu, resulting in the trimetallic Cu cluster 8. These novel reactions pave the way for new synthetic methods to build complicated polymetallic clusters in a controlled fashion.

Metal‐Rich Metallaboranes: Synthesis, Structure, and Bonding of Heteronuclear Trimetallic Clusters containing (μ3‐BH) Ligand

AbstractBuilding upon our earlier results on the chemistry of nido‐1,2‐[(Cp*RuH)2B3H7] (Cp*=ɳ5‐C5Me5) (nido‐1) with different transition metal carbonyls, we continued to investigate the reactivity with group 7 metal carbonyls under photolytic condition. Photolysis of nido‐1 with [Mn2(CO)10] led to the isolation of a trimetallic [(Cp*Ru)2{Mn(CO)3}(μ‐H)(μ‐CO)3(μ3‐BH)] (2) cluster with a triply bridging borylene moiety. Cluster 2 is a rare example of a tetrahedral cluster having hydrido(hydroborylene) moiety. In an attempt to synthesize the Re analogue of 2, a similar reaction was carried out with [Re2(CO)10] that yielded the trimetallic [(Cp*Ru)2{Re(CO)3}(μ‐H)(μ‐CO)3(μ3‐BH)] (3) cluster having a triply bridging borylene unit. Along with 3, a trimetallic square pyramid cluster [(Cp*Ru)2{Re(CO)3}(μ‐H)2(μ‐CO)(μ3,ɳ2‐B2H5)] (4), and heterotrimetallic hydride clusters [{Cp*Ru(CO)2}‐{Re(CO)4}2(μ‐H)] (5) and [{Cp*Ru(CO)}{Re(CO)4}2(μ‐H)3] (6) were isolated. Cluster 4 is a unique example of a M2M′B2 cluster having diboron capped Ru2Re‐triangle. The hydride clusters 5 and 6 have triangular RuRe2 frameworks with one and three μ‐Hs respectively. All the clusters have been characterized by using mass spectrometry, 1H, 11B{1H}, 13C{1H} NMR and IR spectroscopies analyses and the structures of clusters 2–6 have been unambiguously established by XRD analyses. Furthermore, to understand the electronic, structural, and bonding features of the synthesized metal‐rich clusters, DFT calculations have been performed.

Reductive reactivity of a Zn(I) − Zn(I)-bonded compound toward white phosphorus and beyond

This work reports the selective reduction of a number of small molecules by a Zn(I) − Zn(I)-bonded compound. Reaction of dizinc compound [L2Zn2] [L = CH3C(2,6-iPr2C6H3N)CHC(CH3)(NCH2CH2PPh2)] with white phosphorus generated a trimetallic cluster [(LZn)3(μ, κ2: κ2: κ1-P7)], which contained a zinc-coordinated Zintl ion [P7]3−. The low valent Zn(I) compound [L2Zn2] could also reduce 1-azidoadamantane and diphenyl disulfide to selectively afford Zn(II) hexazene complex [L2Zn2(μ-1,6-Ad2-N6)] and thiolate derivative [LZnSPh], respectively. In contrast, oxidation reaction selectively occurred at the pendant phosphine of ligand backbone when reacting [L2Zn2] with elemental sulfur, whereas Zn(I) − Zn(I) bond remained intact.

Trimetallic Chalcogenide Species: Synthesis, Structures, and Bonding.

In an attempt to isolate boron-containing tri-niobium polychalcogenide species, we have carried out prolonged thermolysis reactions of [Cp*NbCl4] (Cp* = ɳ5-C5Me5) with four equivalents of Li[BH2E3] (E = Se or S). In the case of the heavier chalcogen (Se), the reaction led to the isolation of the tri-niobium cubane-like cluster [(NbCp*)3(μ3-Se)3(BH)(μ-Se)3] (1) and the homocubane-like cluster [(NbCp*)3(μ3-Se)3(μ-Se)3(BH)(μ-Se)] (2). Interestingly, the tri-niobium framework of 1 stabilizes a selenaborate {Se3BH}- ligand. A selenium atom is further introduced between boron and one of the selenium atoms of 1 to yield cluster 2. On the other hand, the reaction with the sulfur-containing borate adduct [LiBH2S3] afforded the trimetallic clusters [(NbCp*)3(μ-S)4{μ-S2(BH)}] (3) and [(NbCp*)3(μ-S)4{μ-S2(S)}] (4). Both clusters 3 and 4 have an Nb3S6 core, which further stabilizes {BH} and mono-sulfur units, respectively, through bi-chalcogen coordination. All of these species were characterized by 11B{1H}, 1H, and 13C{1H} NMR spectroscopy, mass spectrometry, infrared (IR) spectroscopy, and single-crystal X-ray crystallography. Moreover, theoretical investigations revealed that the triangular Nb3 framework is aromatic in nature and plays a vital role in the stabilization of the borate, borane, and chalcogen units.

High-Voltage Symmetric Nonaqueous Redox Flow Battery Based on Modularly Tunable [Ru2M(μ3-O)(CH3CO2)6(py)3] (M = Ru, Mn, Co, Ni, Zn) Cluster Compounds with Multielectron Storage Capability

Redox flow batteries (RFBs) provide an attractive solution for large-scale energy buffering and storage. This report describes the development of nonaqueous RFBs based on trimetallic coordination cluster compounds: [Ru2M(μ3-O)(CH3CO2)6(py)3] (M = Ru, Mn, Co, Ni, Zn). The all-ruthenium complex exhibited stable battery cycles in anolyte–catholyte symmetric operation, with rarely observed multielectron storage in a single molecule. Moreover, the complex holds modularly tunable synthetic handles for systematic improvements in solubility and redox potentials. An optimized battery stack containing [Ru3(μ3-O)(CH3CO2)6(py)3]+ anolyte and [Ru2Co(μ3-O)(CH3CO2)6(py)3] catholyte yielded stable cycles with a discharge voltage of 2.4 V, comparable to the state-of-the-art nonaqueous RFBs. Explanation for the exceptional stability of the charged states and prediction of systematic tunability of the redox potentials of the cluster compounds were assisted by DFT calculations.

Vanadium-Based Trimetallic Metal-Organic-Framework Family as Extremely High-Performing and Ultrastable Electrocatalysts for Water Splitting.

This is the first time that the pore-space-partition (PSP) strategy is being successfully applied in the electrochemical field for water splitting, realizing the highly efficient construction of a series of ultrastable pristine MOF electrocatalysts. On integrating the vanadium-based trimetallic building cluster (M2V), the target M2V-MOFs exhibit excellent electrocatalytic activity for HER, OER, and water splitting. In particular, ultralow overpotentials of 314 and 198 mV for Fe2V-MOF as OER and HER electrocatalysts, respectively, can drive a current density of 10 mA cm-2. The fabricated Fe2V-MOF||Pt/C two-electrode configuration for the overall water splitting yields a current density of 10 mA cm-2 at only 1.6 V vs RHE, which is superior to that of the commercial IrO2||Pt/C couple. Notably, high structural and chemical stabilities still can be observed in alkaline condition. This work opens up an exciting pathway to design efficient and stable electrocatalysts based on pristine MOF by integrating the PSP strategy and multimetallic centers.

Multimetallic Permethylpentalene Hydride Complexes.

The synthesis and characterization of group 4 permethylpentalene (Pn* = C8Me6) hydride complexes are explored; in all cases, multimetallic hydride clusters were obtained. Group 4 lithium metal hydride clusters were obtained when reacting the metal dihalides with hydride transfer reagents such as LiAlH4, and these species featured an unusual hexagonal bipyramidal structural motif. Only the zirconium analogue was found to undergo hydride exchange in the presence of deuterium. In contrast, a trimetallic titanium hydride cluster was isolated on reaction of the titanium dialkyl with hydrogen. This diamagnetic, mixed valence species was characterized in the solid state, as well as by solution electron paramagnetic resonance and nuclear magnetic resonance spectroscopy. The structure was further probed and corroborated by density functional theory calculations, which illustrated the formation of a metal-cluster bonding orbital responsible for the diamagnetism of the complex. These permethylpentalene hydride complexes have divergent structural motifs and reactivity in comparison with related classical cyclopentadienyl analogues.

Capture the missing: formation of (PbBi3)− and {[AuPb5Bi3]2}4− via atom exchange or reorganization of the pseudo‐tetrahedral Zintl anion (Pb2Bi2)2−

Abstract(Pseudo‐)tetrahedral p‐block atom units have been attracting the interest of many scientists, mainly regarding their use as elegant starting materials for compounds with larger molecular or extended architectures. The isoelectronic four‐atomic species that were addressed so far span the range from neutral P4, As4, and AsP3, via the homoatomic Si44− anion and its heavier congeners, to heteroatomic Zintl anions (TrPn3)2− or (Tt2Pn2)2− (Tr = Ga, In, Tl; Tt = Si, Ge, Sn, Pb; Pn = P, As, Sb, Bi). Hence, (Pb2Bi2)2− in the salt [K(crypt‐222)]2(Pb2Bi2)·en (en = ethane‐1,2‐diamine) is isoelectronic and isostructural to white phosphorus, but it exhibits significantly different properties owing to its charge and the different nature of the involved atoms, which affects its stability and reactivity. The recently reported compound [K(crypt‐222)]3[Au{η2‐(Pb2Bi2)}2] (A), isolated from reactions of the binary anion with [AuMePPh3] in en, possesses two intact pseudo‐tetrahedral (Pb2Bi2)2− moieties. In this work, however, the same reaction of [AuMePPh3] with [K(crypt‐222)]2(Pb2Bi2)·en in pyridine instead of en, and subsequent layering with tetrahydrofuran or toluene, yielded two compounds comprising Zintl anions that have not yet been reported to occur in condensed phase. One of them is the (PbBi3)− anion, which crystallizes in the triple salt [K(crypt‐222)]4[(PbBi3)(Pb2Bi2)(AuMe2)]·6py (1). The second is the Pb/Bi moiety in the cluster anion {[AuPb5Bi3]2}4−, which was obtained in the compound [K(crypt‐222)]4{[AuPb5Bi3]2}·2py (2). Density functional theory calculations confirm that the (PbBi3)− monoanion results from an atom exchange reaction whereas {[AuPb5Bi3]2}4− was formed upon more significant reorganization of the reactant (Pb2Bi2)2− in the presence of Au(I) ions. The trimetallic cluster is the yet missing, heaviest homolog of a series of isostructural species. The new compounds were accessed by a careful selection of the solvent mixtures used for crystallization, which demonstrates the importance of a thorough control of the reaction space.Key Points Reactions of (pseudo‐)tetrahedral anions of p‐block (semi‐)metals with transition metal compounds were proven to be a very versatile access of larger multimetallic clusters; we report on the formation and isolation of two predicted, yet so far elusive, species of both types of heterometallic molecules, (PbBi3)− and [(Au2Pb5Bi3)]4−. By means of computational studies applying high‐level density functional theory (DFT) methods, we were able to rationalize the formation of the uncommon anion (PbBi3)−, which is the first monoanionic (pseudo‐)tetrahedral molecule. This study confirms both the need and usefulness of DFT calculations in cluster chemistry. Bi‐ or trimetallic cluster compounds may serve as starting materials for new intermetallic phases or act as reactive species in solution or in the gas phase for bond activation themselves. Hence, the understanding of their formation and access on the one hand, and the expansion of the elemental combinations contribute to reach such goals for materials science.

Exploring trimetallic clusters containing alkali and alkaline earth metal atoms with high activity for nitrogen activation

Activation of dinitrogen (N2) is the critical step in nitrogen reduction reaction (NRR) in ammonia synthesis. In this paper, reaction mechanisms of N2 activation on trimetallic clusters Mo2M (M = Li, Na, K, Mg, and Ca) and Mo3−xCax (x = 2–3) were systematically studied by density functional theory calculations. Unlike Mo2 which is inert to N2, clusters with alkali or alkaline earth metal atoms have much higher reactivity toward N2 in terms of both thermodynamics and kinetics. Particularly, in one reaction path of N2 with MoCa2, all the intermediates and transition states are well below the energy sum of the reactants, indicating that the dissociation of N2 on MoCa2 can take place spontaneously in gas-phase reactions. N2 transfers on clusters with different coordination modes, and the N−N bond is gradually activated. When N2 is bonded with three metal atoms with end-on: side-on: side-on coordination mode, it is fully activated and easily dissociated into two adsorbed N atoms. These results may serve as a prototype to design single-cluster catalysts with a trimetallic center for nitrogen activation and conversion.

Computational study of Cu n AgAu (n = 1–4) clusters invoking DFT based descriptors

Abstract Metallic clusters have shown potential uses in science and technology especially in the domain of photovoltaics, biomedical and catalysis. The noble metal based clusters like Cu, Ag, and Au exhibits notable structural, electronic and optical properties. In this work, we have examined physico-chemical behaviours of tri-metallic clusters Cu n AgAu (n = 1–4) by using density functional theory (DFT) technique. Conceptual DFT based descriptors of these clusters are calculated and analysed. HOMO–LUMO gap at n = 2, 3 and 4 are found as 1.667, 1.610 and 1.785 eV, respectively. It states that these clusters can be used in optoelectronic and photovoltaic devices. HOMO–LUMO energy gap, hardness and electronegativity of CunAgAu clusters exhibit an odd–even fluctuation behaviour with the cluster size, n. Molecular hardness of Cu n AgAu cluster shows linear relationship with energy gap whereas molecular softness exhibits an inverse relationship.

Trimetallic clusters in the sumanene bowl for dinitrogen activation.

It is of great importance to find catalysts for the nitrogen reduction reaction (NRR) with high stability and reactivity. A series of M3 clusters (M = Ti, Zr, V, and Nb) supported on sumanene (C21H12) were designed as potential catalysts for the NRR by taking advantage of the high reactivity of trimetallic clusters and the unique geometric and electronic properties of sumanene, a bowl-like organic molecule. Detailed mechanisms of NN bond cleavage on C21H12-M3 were investigated by DFT calculations and compared with those on bare M3 clusters. M3 in the sumanene bowl is very stable with large binding energies, which prohibits the cohesion of M3 into M6. In the bowl, M3 has a (quasi-) equilateral triangle structure with lengthened M-M bonds, which is particularly beneficial to the N2 transfer process on Ti3 and V3 clusters. The N-N bond can be dissociated by both M3 and C21H12-M3 clusters without the overall energy barriers. A blurring effect is found in which some geometric and electronic properties of different metal types become similar when M3 is supported on the substrate. Our work demonstrates that sumanene is a suitable substrate to support M3 in the activation of N2 with enhanced stability and maintained a high level of reactivity compared to bare M3.

Facile N≡N Bond Cleavage by Anionic Trimetallic Clusters V3-x Tax C4- (x=0-3): A DFT Study.

Activation of N2 on anionic trimetallic V3-x Tax C4- (x=0-3) clusters was theoretically studied employing density functional theory. For all studied clusters, initial adsorption of N2 (end-on) on one of the metal atoms (denoted as Site 1) is transferred to an of end-on: side-on: side-on coordination on three metal atoms, prior to N2 dissociation. The whole reaction is exothermic and has no global energy barriers, indicating that the dissociation of N2 is facile under mild conditions. The reaction process can be divided into two processes: N2 transfer (TRF) and N-N dissociation (DIS). For V-series clusters, which has a V atom on Site 1, the rate-determining step is DIS, while for Ta-series clusters with a Ta on Site 1, TRF may be the rate-determining step or has energy barriers similar to those of DIS. The overall energy barriers for heteronuclear V2 TaC4- and VTa2 C4- clusters are lower than those for homonuclear V3 C4- and Ta3 C4- , showing that the doping effect is beneficial for the activation and dissociation of N2 . In particular, V-Ta2 C4- has low energy barriers in both TRF and DIS, and it has the highest N2 adsorption energy and a high reaction heat release. Therefore, a trimetallic heteronuclear V-series cluster, V-Ta2 C4- , is suggested to have high reactivity to N2 activation, and may serve as a prototype for designing related catalysts at a molecular level.

Molecular dynamics and DFT study of 38-atom coinage metal clusters

The thermal behavior of 38-atom mono-, bi-, and trimetallic clusters consisting of Cu, Ag, and Au atoms, is analyzed employing molecular dynamics simulations and DFT calculations for selected cluster compositions. Low-energy structures were singled out to perform NVT molecular dynamics simulations at several temperatures, using the Andersen thermostat for temperature control. The caloric curve is used to estimate the melting temperature and the specific heat. The pair distribution function g(r) of the solid and liquid-phase clusters is examined at different temperatures. When comparing the estimated melting points (Tm) among the monatomic clusters, the order becomes TmCu38>TmAg38>TmAu38. For bimetallic clusters, an increase of Tm is observed for Cu-Au compared to their monatomic counterparts, while the opposite occurs for Cu-Ag clusters. For trimetallic clusters, two low-energy isomers of the Cu36Ag1Au1 cluster are investigated. In this case, Tm is estimated to be 475 K, for the two isomers with the lowest-energy and second-to-lowest energy, respectively. For all the clusters studied, the pair distribution function g(r) shows that the first peak position is not shifted as an effect of temperature and its maximum value varies with composition, while the second peak essentially vanishes upon melting. The common-neighbor analysis (CNA) technique is used to analyze the local structural changes for the trimetallic clusters, again demonstrating a clear structural change upon melting. The HOMO-LUMO energy gap indicates that the trimetallic isomers' behavior is metallic, while the average binding energy show these clusters' energetic stability to be similar.

Heterometallic Coinage Metal Acetylenediide Clusters Showing Tailored Thermochromic Luminescence

Acetelyenediide (C2 2- ) species have been encapsulated in bimetallic and trimetallic clusters: [(AuL)6 Ag7 (C≡C)3 ](BF4 )7 (2) and [(AuL)6 AgCu6 (C≡C)3 ](BF4 )7 (3), L=phenylbis(2-pyridyl)phosphine (PPhpy2 ). Single-crystal X-ray diffraction analysis revealed that they are isostructural and six silver atoms in 2 are replaced with copper in 3. Both clusters have a trefoil skeleton, which can be viewed as three trigonal bipyramidal (LAu-C≡C-AuL)M2 Ag (M=Ag/Cu) motifs sharing a common silver atom. TDDFT calculations showed Cu-doping significantly increases the energy level of (C2 -Cu)-involved occupied orbital, thus inducing interesting transition coupling of dual-emission at low temperature. This work not only provides a strategy for constructing heterometallic clusters, but also shows the prospect for pursuing novel thermochromic luminescent materials by incorporating multi-congeneric metal components.

Heterometallic Coinage Metal Acetylenediide Clusters Showing Tailored Thermochromic Luminescence

AbstractAcetelyenediide (C22−) species have been encapsulated in bimetallic and trimetallic clusters: [(AuL)6Ag7(C≡C)3](BF4)7 (2) and [(AuL)6AgCu6(C≡C)3](BF4)7 (3), L=phenylbis(2‐pyridyl)phosphine (PPhpy2). Single‐crystal X‐ray diffraction analysis revealed that they are isostructural and six silver atoms in 2 are replaced with copper in 3. Both clusters have a trefoil skeleton, which can be viewed as three trigonal bipyramidal (LAu‐C≡C‐AuL)M2Ag (M=Ag/Cu) motifs sharing a common silver atom. TDDFT calculations showed Cu‐doping significantly increases the energy level of (C2‐Cu)‐involved occupied orbital, thus inducing interesting transition coupling of dual‐emission at low temperature. This work not only provides a strategy for constructing heterometallic clusters, but also shows the prospect for pursuing novel thermochromic luminescent materials by incorporating multi‐congeneric metal components.