Heteronuclear Metal Clusters Research Articles

Alloy Reconstruction in Pyrolytic Bowknot-like Heteronuclear CoFe Clusters for Electrocatalytic Application.

The construction of doped molecular clusters is an intriguing way to perform bimetallic doping for electrocatalysts. However, efficiently harnessing the benefits of a doping strategy and alloy engineering to create a nanostructure for electrocatalytic application at the molecular level has consistently posed a challenge. Here we propose an in situ reconstruction strategy aimed at producing an alloy nanostructure through a pyrolysis process, originating from bowknot-like heterometallic clusters. The Schiff base, denoted as ligand L1 (o-vanillin ethylenediamine), was introduced as a precursor to coordinate Fe and Co metals, thereby yielding a heteronuclear metal cluster [(FeCo)(L1)2O]CH3CN. Subsequently, a comprehensive investigation of the in situ reconstruction process [(FeCo)(L1)2O](CH3CN) → [(FeCo)(L1)2O] → [M-O-M/M-O] [CH3+/CH3O+/H2C═N/C2H5+/C4H4+] → [FeCo/Fe3O4/Fe2O3/Co3O4][carbon layer] led to the formation of MOx/CoFe@NC-700 during the pyrolysis. This process reveals that the metals Fe and Co in the clusters undergo partly in situ evolution into FeCo alloys, resulting in the successful preparation of MOx/CoFe@NC (M = Fe, Co) nanomaterials that leverage the advantages of both doping strategies and alloy engineering. The synergistic interaction between alloy particles and metal oxides establishes active sites that contribute to the excellent oxygen evolution (OER) and hydrogen evolution (HER) catalytic behaviors. Notably, these materials exhibit outstanding OER and HER properties under alkaline conditions, with overpotentials of 191 and 88 mV for OER and HER, respectively, at 10 mA cm-2. Investigation of the in situ conversion of Schiff base bimetal clusters into alloy materials through pyrolysis offers a novel strategy for advancing electrocatalytic applications.

Catalytic NO Reduction by Noble-Metal-Free Vanadium-Aluminum Oxide Cluster Anions.

By using state-of-the-art mass spectrometry and guided by the newly discovered single-electron mechanism (SEM; e.g., Ti3+ + 2NO → Ti4+-O•- + N2O), we determined experimentally that the vanadium-aluminum oxide clusters V4-xAlxO10-x- (x = 1-3) can catalyze the reduction of NO by CO and substantiated theoretically that the SEM still prevails in driving the catalysis. This finding marks an important step in cluster science in which a noble metal had been demonstrated to be indispensable in NO activation mediated by heteronuclear metal clusters. The results provide new insights into the SEM in which active V-Al cooperative communication favors the transfer of an unpaired electron from the V atom to NO attached to the Al atom on which the reduction reaction actually takes place. This study provides a clear picture for improving our understanding of related heterogeneous catalysis, and the electron hopping behavior induced by NO adsorption could be a fundamental chemistry for driving NO reduction.

Diffusion Monte Carlo investigation of electronic structure properties for 13-atom alkali metal clusters

Electronic structure properties of 13-atom icosahedral alkali metal clusters (X13, X = Li, Na, K, Rb, and Cs) were investigated with the Diffusion Monte Carlo (DMC) and Density Functional Theory (DFT) methods. The overall results of vertical ionization energies, vertical electron affinities and dissociation energies are in good agreement with theoretical/experimental values found in the literature for these clusters. However, the DFT approach investigated, B3LYP, provides larger discrepancies than DMC for dissociation energies. In this case, empirical dispersion corrections seem important to improve the binding energy data from DFT. We also considered heteronuclear alkali metal clusters such as YX12, where the Y atom was placed at the center and also at the face of the initial icosahedral structure of X13. To our knowledge, the results for such heteronuclear clusters are being reported for the first time, providing an important initial step for understanding these systems. This work demonstrates that face-type YX12 clusters are usually more strongly bonded than the respective center-type structures, except for LiNa12, CsRb12, and KCs12 (according to DMC results). In addition, the trends evidenced in binding energies are analysed in details.

Series of TM-OFs as a Platform for Efficient Catalysis and Multifunctional Luminescence Sensing.

Three novel porous transition-metal-organic frameworks (TM-OFs), formulated as [Co3(DCPN)2(μ2-OH2)4(H2O)4](DMF)2 (1), [Cd3(DCPN)2(μ2-OH2)4(H2O)4](DMF)2 (2), and [CdK(DCPN)(DMA)] (3), have been successfully prepared via solvothermal conditions based on a 5-(3',6'-dicarboxylic phenyl) nicotinic carboxylic acid (H3DCPN) ligand. 1 and 2 both have the same porous 3D network structure with the point symbol of {410·614·84}·{45·6}2 based on trinuclear ({Co3} or {Cd3}) clusters, indicating a one-dimensional porous channel, and possess excellent water and thermal stability; 3 also displays a porous 3D network structure with a 4-connected sra topology based on the heteronuclear metal cluster {CdK}. Complex 1 can be used to load Pd nanoparticles (Pd NPs) via a wetness impregnation strategy to obtain Pd@1. The reduction of nitrophenols (2-NP, 3-NP, 4-NP) by Pd@1 in aqueous solution shows outstanding conversion, excellent rate constants (k), and remarkable cycling stability due to the synergistic effect of complex 1 and Pd NPs. Luminescence sensing tests confirmed that 2 is a reliable multifunctional chemical sensor with high selectivity and sensitivity for low concentrations of Fe3+, Cr2O72-, CPFX, and NFX. Specifically, 2 shows a fluorescence enhancement behavior toward fluoroquinolone antibiotics (CPFX and NFX), which has not been reported previously in the literature. Moreover, the rational mechanism of fluorescence sensing was also systematically investigated by various detection means and theoretical calculations.

Mutual functionalization of dinitrogen and methane mediated by heteronuclear metal cluster anions CoTaC2.

The direct coupling of dinitrogen (N2) and methane (CH4) to construct the N–C bond is a fascinating but challenging approach for the energy-saving synthesis of N-containing organic compounds. Herein we identified a likely reaction pathway for N–C coupling from N2 and CH4 mediated by heteronuclear metal cluster anions CoTaC2−, which starts with the dissociative adsorption of N2 on CoTaC2− to generate a Taδ+–Ntδ− (terminal-nitrogen) Lewis acid–base pair (LABP), followed by the further activation of CH4 by CoTaC2N2− to construct the N–C bond. The N Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N cleavage by CoTaC2− affording two N atoms with strong charge buffering ability plays a key part, which facilitates the H3C–H cleavage via the LABP mechanism and the N–C formation via a CH3 migration mechanism. A novel Nt triggering strategy to couple N2 and CH4 molecules using metal clusters was accordingly proposed, which provides a new idea for the direct synthesis of N-containing compounds.

Thermodynamics of Al2M3 (M = 3d Element) Metal Clusters in the Frame of DFT Quantum-Chemical Modeling

The standard thermodynamic parameters of formation (ΔfH°(298 K), ΔfS°(298 K), and ΔfG°(298 K)) for p,d-metal clusters of Al2M3 (M = 3d) stoichiometry and the standard enthalpy, entropy, and Gibbs free energy of their formation reactions from monoatomic species in the gas phase were calculated by the hybrid density functional (DFT) method in OPBE/TZVP approximation and Gaussian09 software. Such reactions were found to be exothermic with an enthalpy factor, and the thus-formed heteronuclear metal clusters are distinguished by a high thermal stability. Both the individual thermodynamic characteristics of the considered metal clusters and the thermodynamic parameters of their formation reactions were found to have intricate variation dynamics depending on the nature of 3d element.

Design of a graphene nitrene two-dimensional catalyst providing a well-defined site accommodating up to three metals, with application to N2 reduction electrocatalysis.

We consider here a novel two-dimensional catalyst M3-C2N that we apply to electrocatalytic N2 reduction. Using the PBE-D3 flavor of density functional theory (DFT), we studied 12 choices for the M3 metal clusters to find two cases: homonuclear Rh3-C2N and heteronuclear Co2Mo-C2N that are particularly promising for electrocatalytic reduction of N2.

Crystal Structures, Magnetic Properties, and Theoretical Investigations of Three Linear Cluster Complexes with Pyridine-2-Amidoxime

Three novel trinuclear mixed-transition-metal complexes of Fe(III), Co(III, II), Ni(II) and Cr(III)), with pyridine-2-amidoxime (Hpa) ligand are synthesized, i.e. [FeNi2(pa)6]Cl·15H2O (1), [CrNi2(pa)6]OH·5H2O (2), and [CoCo2(pa)6]NO3 (3). These complexes are characterized by variable-temperature magnetic susceptibility, electrochemistry, and single crystal X-ray diffraction methods. 1 and 2 are heteronuclear metal clusters in the perfect linear arrangement, i.e. [NiII⋯FeIII⋯NiII and [NiII⋯CrIII⋯NiII] respectively, while 3 is linear [CoII⋯CoIII⋯CoII] trinuclear. Theoretical calculations are employed to successfully account for the experimental results of the variable temperature magnetic susceptibility.

Photoelectron Velocity-Map Imaging and Theoretical Studies of Heterotrinuclear Metal Carbonyls V2Ni(CO)n- (n = 6-10).

Photoelectron velocity-map imaging spectroscopy was conducted for the heterotrinuclear metal carbonyls V2Ni(CO)n- (n = 6-10). Electronic structure calculations were performed to understand the experimental spectral features. The binding motif of a V-V-Ni chain with two side-on-bonded carbonyls and two bridging carbonyls is favored in the n = 6-9 clusters. A V2Ni triangle core structure is formed at n = 10 with the involvement of two carbonyls with the carbon atom triply coordinated to metal atoms, three bridging carbonyls, and five terminal carbonyls, in which CO bonding configurations mirror the adsorption features in the three-fold hollow, bridging, and atop sites on the closely packed surface, respectively. The present study provides a stepwise picture for molecular level understanding of CO bonding on heteronuclear metal clusters, which is directly relevant to the elementary processes of CO on the alloy surfaces/interfaces.

Molecular structure of hexatomic heteronuclear (AlFe) metal clusters as determined by the DFT quantum-chemical calculation

Geometric parameters of molecular structures of hexatomic heteronuclear (AlFe) clusters with various number of aluminum atoms (Al2Fe4 and Al3Fe3) were calculated using the density functional hybrid method in the OPBE/TZVP approximation. It was found that the first of these clusters is able to exist in nine and the second in twenty structural modifications substantially differing from each other in their stability and geometric parameters. The values of bond lengths, planar and dihedral (torsion) angles for some of these modifications are given.

Density Functional Theory Investigation on the Nucleation of Homo- and Heteronuclear Metal Clusters on Defective Graphene

Nucleation of homo- (Ni, Pd, Re, Pt) and heterometallic (Ni–Pd, Re–Pt) clusters on monovacancy sites of a graphene sheet has been investigated by means of periodic density functional theory calculations. It is shown that a vacant site in graphene is an effective nucleation center for both the monometallic and bimetallic clusters, whose characteristics are described in terms of structural distortions, nucleation energetics, affinities between different metal atoms, metal–carbon interactions, and ease of diffusion of metal atoms on graphene.

Substituting Fe for two of the four Mn ions in photosystem II-effects on water-oxidation.

We have investigated the interaction of Fe(II) cations with Ca-depleted PSII membranes (PSII[-Ca,4Mn]) in the dark and found that Fe(II) incubation removes 2 of 4Mn ions from the tetranuclear Mn cluster of the photosynthetic O2-evolving complex (OEC). The reduction of Mn ions in PSII(-Ca,4Mn) by Fe(II) and the concomitant release of two Mn(II) cations is accompanied by the binding of newly generated Fe(III) in at least one vacated Mn site. Flash-induced chlorophyll (Chl) fluorescence yield measurements of this new 2Mn/nFe cluster (PSII[-Ca,2Mn,nFe]) show that charge recombination in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) occurs between Qa (-) and the remaining Mn/Fe cluster (but not YZ (●)) in the OEC, and extraction of 2Mn occurs uniformly in all PSII complexes. No O2 evolution is observed, but the heteronuclear metal cluster in PSII(-Ca,2Mn,nFe) samples is still able to supply electrons for reduction of the exogenous electron acceptor, 2,6-dichlorophrenolindophenol, by photooxidizing water and producing H2O2 in the absence of an exogenous donor as seen previously with PSII(-Ca,4Mn). Selective extraction of Mn or Fe cations from the 2Mn/nFe heteronuclear cluster demonstrates that the high-affinity Mn-binding site is occupied by one of the iron cations. It is notable that partial water-oxidation function still occurs when only two Mn cations are present in the PSII OEC.

Thermal formation of mixed‐metal inorganic complexes at atmospheric pressure

Atmospheric-pressure thermal desorption ionization (APTDI), a new variant on older ionization methods, is employed to generate gas-phase ions from inorganic and organometallic compounds. The method is compared to conventional electrospray ionization (ESI) of these compounds and found in most cases examined to yield simpler mass spectra which are useful in the characterization of the pure compounds. Cluster formation, however, is prominent in these spectra and mixtures of V(IV)O(salen), Ni(II)(salen) and Co(II)(salen) show mixed-metal cluster ions. This makes APTDI a way to prepare gas-phase ions which contain multiple selected metal atoms and ligands. Such mixed-metal complexes can be mass-selected and structurally characterized by tandem mass spectrometry. Strong contrasts are evident in the dissociation behavior of homonuclear and heteronuclear metal clusters, the latter showing accompanying redox processes. The chemical reactivity accompanying collision-induced dissociation (CID) of some of the mixed-metal clusters is typified by the protonated species H+[NiVO(salen)], which undergoes a formal oxidation process (hydrogen atom loss) to give the molecular radical cation of Ni(salen). This ionization method may provide a new route to unique inorganic compounds on surfaces through soft landing of appropriate cluster ions. The contrasting behavior of the ESI and APTDI processes is evident in the salens where ESI shows simple Bronsted acid/base chemistry, no mixed-metal clusters and no redox chemistry.

Studies of metal exchange reactions: the synthesis and structures of heteronuclear metal clusters containing the indenyl ligand (μ 3-CR)Co 2M(CO) 8(η 5- Ind)(R=H,CH 3,C 6H 5,COOC 2H 5; M=Mo,W)

The novel tetrahedral clusters ( μ 3-CR)Co 2M(CO) 8(η 5-Ind) (M=Mo,W; R=H, CH 3, C 6H 5, COOC 2H 5) 5– 12 containing the indenyl ligand were isolated from reactions of tricobalt clusters (μ 3-CR)Co 3(CO) 9 (R=H, CH 3, C 6H 5, COOC 2H 5) and K(η 5-Ind)M(CO) 3 (M=Mo,W) under mild conditions. The cluster complex (μ 3-CC 6H 5)CoMo 2(CO) 7(η 5-Ind)(η 5-Cp (Cp*=C 5H 4C(O)CH 3) 16 was obtained via the stepwise metal exchange reaction of complex (μ 3-CC 6H 5)Co 2Mo(CO) 8(η 5-Ind) 9 with Na(η 5-CpMo(CO) 3, but the reaction of (μ 3-CC 6H 5)Co 2Mo(CO) 8(η 5-Cp*) 15 with K(η 5-Ind)Mo(CO) 3 yielded only 9. The crystal structures of compounds 7, 9 and 13 were established by single crystal X-ray diffraction methods and show structural evidence for “slippage” of the indenyl ring.

Tetrahedral and heteronuclear transition metal clusters through isolobal displacements and functional transformations

The isolobal reaction of the tetrahedral cluster Ph2C2Co2(CO)6with η5-CHOC5H4(CO)3MNa (M = Mo, W) yields η5-CHOC5H4MCoC2Ph2(CO)5 [(1) M = Mo, (2) M = W], whereas M–M singly-bonded dimers [η5-RC5H4- M(CO)3]2 [M = Mo, R = Ac; M = Mo, W, R = CHO] react with Co2(CO)8 to give η5-AcC5H4MoCo3(CO)11(7) and η5-C5H5MCo3(CO)11 [(8) M = Mo, (9) M = W], respectively. While (1) and (2) react with 2,4-dinitrophenylhydrazine to give phenylhydrazone derivatives η5-2,4-(NO2)2C6H3NHN=CHC5H4MCoC2Ph2(CO)5 [(3) M = Mo, (4) M = W], treatment of η5-AcC5H4MCoFe(CO)8(μ3-S) with 2,4-dinitrophenylhydrazine produces corresponding derivatives η5-2,4-(NO2)2C6H3NHN=C(Me)C5H4MCoFe(CO)8(μ3-S) [(5) M = Mo, (6) M = W]. In addition, the cyclopentadienylformaldehyde ligand in the η5-CHOC5H4MoCoFe(CO)8(μ3-S) cluster can be decarbonylated in the presence of Co2(CO)8 to give the parent cluster η5-C5H5MoCoFe(CO)8(μ3-S)(10). This observation, together with the formation of (8) and (9) in the presence of Co2(CO)8 can be explained by the proposed mechanism.

Novel tetrahedral and heteronuclear transition metal clusters prepared via single and double isolobal displacements

Ten transition metal cluster complexes with parent and substituted cyclopentadienyl ligands, [(η5-C5H4 CH2CH2)2O][MFeCoS(CO)8]2 (2 M = Mo; 3 M = W), (η5-C5H5)(η5-RC5H4)MFeNiS(CO)5 (5 M = Mo, R = Me; 6 M = W, R = H), (η5-C5H5)[η5-C5H4C(O)CH2]2[WFeNiS(CO)5][WFeCoS(CO)8] (8), (η5-C5H5)2[η5-C5H4 C(O)CH2]2[WFeNiS(CO)5]2 (9), (η5-RC5H4)[(η5-C5H4CH2CH2)2O][Mo2FeS(CO)7][MoFeCoS (CO)8] (10 R = MeCO; 12 R = MeO2C), (η5-RC5H4)2[(η5-C5H4CH2CH2)2O][Mo2FeS(CO)7]2 (11 R = MeCO; 13 R = MeO2C), were synthesized through single and double isolobal displacements and characterized by elemental analyses, i.r., 1H-n.m.r. and MS techniques.

Short-lived metal clusters in aqueous solutions: formation, identification, and properties

The formation and properties of short-lived homo- and heteronuclear metal clusters in aqueous solutions were investigated by pulse radiolysis. These species arise in early stages of the aggregation of metal atoms and ions in unusual oxidation states. The conditions favoring the formation of positively charged “magic” clusters and intermediate heterometallic clusters were elucidated.

Synthesis of Triangular and Tetrahedral Heteronuclear Metal Clusters Using Hydride Complexes of Cyclopentadienylrhodium and -ruthenium as the Precursors

Photochemical and/or thermal reactions of Cp*Rh(H)2(SiEt3)2 (Cp* = η5-C5Me5) with the dimeric metal complexes [CpNi(CO)]2 (Cp = η5-C5H5), [CpCo(NO)]2, [CpRu(CO)2]2, and [CpFe(CO)2]2 yielded the tri...

Heteronuclear metal cluster complexes with a new coordination mode of the Fe 2S 2(CO) 6 unit. Synthesis, structure and possible reaction pathway of the first FeCuS cluster compound, [Fe 6Cu 5S 6(CO) 18(PPh 3)2] −

The first iron-copper-sulfur cluster compound [Et 4N][Fe 6Cu 5(μ 4-S) 6(CO) 18(PPh 3) 2] ( 1) is prepared by the reaction of [Et 4N][CuCl 2PPh 3] with Li 2[Fe 2S 2(CO) 6] in mixed solvents of MeCNCH 3OH. 1·MeCN crystallizes in the monoclinic, space group Pn with a = 12.426(3), b = 15.572(4), c = 20.709(4) Å;β= 90.14(2)°; V= 4007.2 Å 3; Z= 2, D c = 1.80 g cm −3, and R 1 = 0.032, R 2 = 0.037 for 3319 independent reflections ( I>3σ( I)). The anion of 1 contains an undeca-nuclear FeCuS core with Fe 1 and Cu I, [Fe 6Cu 5(μ 4-S) 6] −, which consists of a central trigonal bipyramid composed of five copper atoms in the center and three ‘butterfly’ type Fe 2S 2 units chelating to the copper atoms of the central Cu 5 trigonal bipyramid along the pseudo- D 3 axis resulting in pseudo- D 3 symmetry. All the sulfur atoms in 1 are μ 4-S, linking to two iron and two copper atoms. Around the core, twelve terminal carbonyls, six bridging CO groups and two PPh 3 ligands meet the requirement of four-coordination of the copper atoms and five-coordination of the iron atoms. FeS and CuS distances are 2.28–2.36 and 2.24–2.51 Å, respectively. There are fifteen MM bonds in 1, including three FeFe of 2.5 Å, six CuFe of 2.7 Å and six CuCu of 2.6 Å. The Fe 2S 2(CO) 6 units in 1 take a new coordination mode in that each unit coordinates to four metal atoms by its two sulfur atoms in a μ 4-type fashion. A possible reaction pathway for 1 via the formation of two reactive fragments is proposed and discussed.

The synthesis of heteronuclear transition metal clusters derived from alkylidyne tricobalt cluster precursors: I. The reaction of (μ 3-CCl)Co 3(CO) 9 with transition metal carbonyl anions. The crystal and molecular structure of (μ 3-CCl)Co 2Mo(CO) 8(η 5-C 5H 5)

Metal exchange reactions were used to produce heterometallic clusters derived from alkylidyne tricobalt precursors. Reaction of the cluster (μ 3-CCl)Co 3(CO) 9 with the potassium salt of (η 5-C 5H 5)Mo(CO) 3 − produced (μ 3-CH)CoMo 2(η 5-C 5H 5) 2(CO) 7, and (μ 3-CH)Co 2Mo(η 5-C 5H 5)(CO) 8 in an overall yield of 35%. The use of the bis(triphenylphosphine)iminium cation as the counterion leads, after work-up, to products with the reactive apical group intact. The structure of (μ 3-CCl)Co 2Mo(η 5-C 5H 5)(CO) 8, ( 1), has been determined. Use of (η 5-C 5H 5)Cr(CO) 3 − or (η 5-C 5H 5)W(CO) 3 − also gives substituted products, but in lower yields. The Mn(CO) 5 − anion effects reduction of the starting cluster rather than yielding substituted products.