Energy and structure of copper clusters (n=70-150) studied by the Monte Carlo computer simulation

The structure and binding energy of copper clusters of the size range 70 to 150 were studied by using the embeddedatom method. The stability of the structure of the clusters was studied by calculating the average binding energy per atom, first difference energy and second difference energy of copper cluster. Most of the copper clusters of the size n=70-150 adopt an icosahedral structure. The results show that the trends are in agreement with theoretic prediction for copper clusters. The most stable structures for copper clusters are found at n=77, 90, 95, 131, 139.

Cluster size and substrate temperature affecting thin film formation during copper cluster deposition on a Si(001) surface

The soft deposition of Cu clusters on a Si （001） surface was studied by molecular dynamics simulations. The embedded atom method, the Stillinger-Weber and the Lennar-Jones potentials were used to describe the interactions between the cluster atoms, between the substrate atoms, and between the cluster and the substrate atoms, respectively. The Cu13, Cu55, and Cu147 clusters were investigated at different substrate temperatures. We found that the substrate temperature had a significant effect on the Cn147 cluster. For smaller Cu13 and Cu55 clusters, the substrate temperature in the range of study appeared to have little effect on the mean center-of-mass height. The clusters showed better degrees of epitaxy at 800 K. With the same substrate temperature, the Cu55 cluster demonstrated the highest degree of epitaxy, followed by Cu147 and then Cu13 clusters. In addition, the Cu55 cluster showed the lowest mean center-of-mass height. These results suggested that the Cu55 cluster is a better choice for the thin-film formation among the clusters considered. Our studies may provide insight into the formation of desired Cu thin films on a Si substrate.

Molecular dynamics simulation of thermodynamical properties of copper clusters

The melting and freezing processes of CUN （N =180, 256, 360, 408, 500, 628 and 736） nanoclnsters are simulated by using micro-canonical molecular dynamics simulation technique, The potential energies and the heat capacities as a function of temperature are obtained. The results reveal that the melting and freezing points increase almost linearly with the atom number in the cluster increasing. All copper nanoclusters have negative heat capacity around the melting and freezing points, and hysteresis effect in the melting/freezing transition is derived in CUN nanoclusters for the first time.

A Density Functional Study for the Reaction Mechanism of CO Oxidation on the Copper Cluster

We have studied the reaction mechanism of CO oxidation on the Cu13 cluster via density functional theory. There are two main reaction pathways to be considered： Eley-Rideal（ER） and Langmuir-Hinshelwood（LH） mechanisms, respectively. According to these two main reaction mechanisms, we have obtained five reaction pathways for the first CO oxidation（denoted as RER1,RER2, RLH1, RLH2 and RLH3, respectively）： RER1 is COgas ＋ O2（ads） → O（ads） ＋ CO2（gas）; RER2 is COgas ＋ O2（ads） → CO3（ads） → O（ads） ＋ CO2（gas）; RLH1 refers to CO（ads） ＋ O2（ads） → O（ads） ＋ CO2（gas）; RLH2 refers to CO（ads） ＋ O2（ads） → OOCO（ads） → O（ads） ＋ CO2（gas） and RLH3 refers to O2（ads） ＋ CO（ads）→ O（ads） ＋ O（ads） ＋ CO（ads） → O（ads） ＋ CO2（gas）. These pathways have low energy barriers and are strongly exothermic, suggesting the Cu13 cluster is very favorable catalyst for the first CO oxidation. However, there are higher energy barriers of 99. 8 and 45.4 kJ/mol in the process of producing and decomposing intermediates along the RLH2 and RER2, indicating that RER1, RLH1 and RLH3 are superior pathways with lower energy barriers, especially the RER1 channel. Thereafter, the second CO is more prone to react with the remaining oxygen atom on Cu13 along the ER channel in comparison with the LH pathway, in which the moderate barrier is 70.0 kJ/mol and it is exothermic by 59.6 kJ/mol. Furthermore, the interaction between the absorbate and cluster is analyzed by electronic analysis to gain insights into high activity of the copper cluster.

Enhancing solar-driven overall water splitting via both sacrifice and noble metal free photocatalysis: copper cluster/boron-doped carbon nitride catalysts

The major impediment to the additional industrialization of water splitting is the high cost of the co-catalyst made of noble metals and the sacrificial reagent. A binary photocatalytic system, consisting of B-doped g-C_(3)N_(4) nanosheets(Cu_(20)@BCN-X) and atomically accurate copper clusters, is designed in this study. The copper clusters serve as co-catalysts for H_(2) evolution and exhibit Pt-like activity, whereas the nanosheets serve as carriers and semiconductor components for O_(2) evolution. Such binary system, created using simple techniques, demonstrates hydrogen bonding interactions that promote synergistic effects and efficient binding and charge transfer across the interface between the two components. Band position manipulation of carbon nitride nanosheets demonstrates a Z-scheme charge transfer mechanism between the nanosheets and copper clusters. This photocatalytic system can accomplish the photocatalytic overall water splitting process(259.9 μmol g^(-1)h^(-1)of H_(2) and 129.4 μmol g^(-1)h^(-1)of O_(2)) without using sacrificial agents or noble metal co-catalysts. This work lays the foundation for the design of overall water splitting catalysts by precisely manipulating the energy levels, and it also paves the way for commercialized photocatalytic catalysts that do not require noble metals or sacrificial chemicals.

Catalytic epoxidation of olefin over supramolecular compounds of molybdenum oxide clusters and a copper complex

The catalytic epoxidation of olefin was investigated on two copper complex-modified molybdenum oxides with a 3D supramolecular structure, [Cu（bipy）]4[Mo15O47].2H2O （1） and [Cu1（bix）][（Cu1bix） （δ-MoVl8O26）0.5] （2） （bipy = 4,4＇-bipyridine, bix = 1,4-bis（imidazole-1-ylmethyl）benzene）. Both compounds were catalytically active and stable for the epoxidation of cyclooctene, 1-octene, and styrene with tert-butyl hydroperoxide （t-BuOOH） as oxidant. The excellent catalytic performance was attributed to the presence of stable coordination bonds between the molybdenum oxide and copper complex, which resulted in the formation of easily accessible Mo species with high electropositivity. In addition, the copper complex also acted as an active site for the activation of t-BuOOH, thus im- proving these copper complex-modified polyoxometalates.

The reactivity of O_(2) with copper cluster anions Cu_(n)^(-)(n = 7-20):Leveling effect of spin accommodation

The activation of molecular oxygen is an important step in metal-catalyzed oxidation reactions and a hot subject for the research of gas-phase metal clusters.It is known that the Ag and Au clusters readily re-act with O_(2)when they have open shell electronic structures.Distinct from this,here we observed Cu_(n)^(-)(n=7−20)clusters of both open and closed shells possess high reactivity with O_(2)with few exceptions.In a combination with ab initio calculations,we demonstrate that the activation of O_(2)on the even-and odd-sized Cu_(n)^(-)clusters follows the single and double electron transfer models,respectively.Such phe-nomenon of metal clusters with different basicity to activate oxygen is enabled by the leveling effect of spin accommodation.The activity of Cu_(n)^(-)clusters is correlated to the HOMO level,and for the close-shell clusters is also governed by the vertical spin excitation energy(VSE).In encountering the attack of dioxygen,the activity of the copper cluster anions not only depends on their basicity to donate electrons,but also closely associated with the cluster sizes.Small copper clusters Cu_(n)^(-)(n=7−13)can dissociate O_(2)spontaneously,while large clusters require extra energies and display close relationship between the reaction rates and electronic vertical detachment energies(VDE).Our work illuminates a novel reaction mechanism between Cu_(n)^(-)clusters and O_(2),which sheds light in manipulating the activity and stability of coinage clusters by controlling the spin and charge states.

Synthesis and Crystal Structure of Dinuclear Copper Cluster Compound ［Cu（dtp）PPh_3］_2

The title compound [Cu(dtp) PPh3]2 (dtp=S2,P(OEt)2) was prepared by heating the mononuclear compound Cu(dtp)(PPh3)2 in CH3CN solution.It crystallizes in the triclinic space group P1 with parameters a=9.71 6(5),b=11.026(5),c=12.475(4) A.α=78.16(3)°,β=102. 64(4), γ=114.34(4)°,V=1178(1)A 3,Z=1,Dc=1.44 g/cm3,MoKα(λ=0.71069 A) μ=12. 48cm-1,F(000)=528.Final R=0.041.Rω= 0. 052 for 3653 unique intensity data(I≥3σ(I)).The molecule of the title compound can be viewed as a centrosymmetric dimer with two[Cu(dtp)(PPh3)] units,which are bridged by two S atoms belonging to the dtp ligands.The exact planar[Cu2S2] core and two[CuS2P] four-membered rings form a chair conformation.The Cu…Cu distance is 2.991(5) A.

EPR Study of a New Crystal of the Binuclear Copper(Ⅱ) Cluster Compound- Cu_2(α-C_(10)H_7CH_2CO_2)_4-(DMF)_2 ·(DMF)_2·H_2O

In this paper, single crystal EPR study of a new binuclear copper (Ⅱ) cluster compound-[Cu2(α-C(10) H7CH2CO2)4 (DMF)2]·[DMF]2·H2O](DMF= (CH3)2NCOH) at room temperature is reported. The lines of △Ms=±1 allowing transition and △M=2 forbiding transition are shown in EPR spectra. The experimental data are consistent with the calculated results by the leastsquares fitting prograrn in three principal planes of g and D tensors. The spin Hamiltonian parameters are as follows: gx=2. 1482, gy=2. 0529 ,gz=2. 3905, D= 0. 348 cm￣(-1) and E =0. 01 cm-1. The diagrams of the energy levels have been obtained when the magnetic field is oriented to three principal axes. The polycrystal EPR spectra have been measured at room temperature and 77K, respectively.and the parameters of these spectra are given (g∥= 2. 094, g⊥= 2. 425, D= 0. 37 cm-1,E=0). The parameter of the isotropic magnetic exchange interaction J=-254cm-1 is determined, and that of the anisotropic magnetic exchange J1=-153 cm-1 is calculated. The average magnetic susceptibility of the polycrystal sample χ= 1. 39 ×10-6 (c. g. s) has been measured by Faraday powder method. Thus the average magnetic mornent μ=1. 43 B. M. can be calculated. It is shown that the exchange interactions between the metal ions of the binuclear copper(Ⅱ) cluster compound are confirmed antiferromagnetic In nature.

One Novel Tetranuclear Copper Cluster by 2-(1H-Pyrazol-3-yl)pyridine:Synthesis, Structure and Properties

A novel tetranuclear copper cluster[Cu4(μ-L)6Cl2]was constructed by 2-(1H-pyrazol-3-yl)pyridine(HL)under hydrothermal conditions,and structurally concluded by single-crystal X-ray diffractions,elemental analyses and IR spectra.The title complex 1 was of triclinic system,space group■,C24H18ClCu2 N9,Mr=595.01,a=9.6497(13),b=11.4133(7),c=13.0919(15)?,α=99.166(7),β=108.707(11),γ=111.974(9)°,V=1200.7(2)?3,Z=2,Dc=1.997 g/cm^3,F(000)=706,μ(MoKα)=3.203 nm-1,Rint=0.0404,R=0.0536 and wR=0.1490 for4890 observed reflections with I>2σ(I).In this structure,complex 1 was the unimolecule with unprecedented tetranuclear cluster,which was expanded into a 2D network by wide-ranging C-H…Cl intermolecular hydrogen bonds and further exhibited a 3D supramolecular architecture based onπ-πstacking interactions.In addition,the complex was thermally stable up to 300℃and the solid state fluorescent property of 1 was examined and compared with the ligand.

EPR Study of a New Crystal of the Binuclear Copper（Ⅱ） Cluster Compound－〔Cu2(α－C10H7CH2CO2)4－（DMF）2〕·（DMF）2·H2O

In this paper, single crystal EPR study of a new binuclear copper (Ⅱ) cluster compound-[Cu2(α-C(10) H7CH2CO2)4 (DMF)2]·[DMF]2·H2O](DMF= (CH3)2NCOH) at room temperature is reported. The lines of △Ms=±1 allowing transition and △M=2 forbiding transition are shown in EPR spectra. The experimental data are consistent with the calculated results by the leastsquares fitting prograrn in three principal planes of g and D tensors. The spin Hamiltonian parameters are as follows: gx=2. 1482, gy=2. 0529 ,gz=2. 3905, D= 0. 348 cm￣(-1) and E =0. 01 cm-1. The diagrams of the energy levels have been obtained when the magnetic field is oriented to three principal axes. The polycrystal EPR spectra have been measured at room temperature and 77K, respectively.and the parameters of these spectra are given (g∥= 2. 094, g⊥= 2. 425, D= 0. 37 cm-1,E=0). The parameter of the isotropic magnetic exchange interaction J=-254cm-1 is determined, and that of the anisotropic magnetic exchange J1=-153 cm-1 is calculated. The average magnetic susceptibility of the polycrystal sample χ= 1. 39 ×10-6 (c. g. s) has been measured by Faraday powder method. Thus the average magnetic mornent μ=1. 43 B. M. can be calculated. It is shown that the exchange interactions between the metal ions of the binuclear copper(Ⅱ) cluster compound are confirmed antiferromagnetic In nature.

Structures, stabilities and magnetic moment of small copper-nickel clusters

This paper obtains the lowest-energy geometric structures and the electronic and magnetic properties of small CuNiN clusters by using all-electron density functional theory. The calculated results reveal that the Cu atom prefers to occupy the apical site when N ≤ 9 and for the clusters with N = 10, the Cu atom starts to encapsulate in the cage. The CuNi7 and CuNi9 are magic clusters. The magnetism correlates closely with the symmetry of the clusters. For these clusters, the charge tends to transfer from the nickel atoms to the copper atoms. It finds that the doping of Cu atom decreases the stability of pure NiN clusters.

Computer simulation of the bombardment of a copper film on graphene with argon clusters

The process of graphene cleaning of a copper film by bombarding it with Ar_（13） clusters is investigated by the molecular dynamics method.The kinetic energies of the clusters are 5,10,20,and 30 eV and the incident angles are θ= 90°,75°,60°,45°,and 0°.It is obtained that the cluster energy should be in the interval 20 eV-30 eV for effective graphene cleaning.There is no cleaning effect at vertical incidence（θ =0°） of Ar_（13） clusters.The bombardments at 45° and 90° incident angles are the most effective on a moderate and large amount of deposited copper,respectively.

Synthesis and Crystal Structure of a Novel Hetero-six-nuclear Copper-iron Cluster Containing Ferroceylphenyl Groups

A new hetero-six-nuclear cluster was synthesized and determined by X-ray diffraction technique. The four-carboxylate groups are bound to the Cu(II) atoms to form Cu(OR)4Cu paddle-wheel-type cage between two DMF as the basis for the cluster. The distance of two copper(II) atoms is 2.642 ?, and they are bridged by the carboxylate groups. A huge system plane was auto-assembled by four host molecules and two Cu (II) ions, which was observed in the crystal structure.

Structures and Electronic Properties of Cu_N (N≤13) Clusters

A systematic study on the structures and electronic properties of copper clusters has been performed using the density functional theory. In the calculation, there are many isomers near the ground state for small copper clusters. Our results show that the three-dimensional isomers of copper clusters start from Cu7 cluster and then show a tendency to form more compact structures. The results of the formation energy and the second derivative of binding energy with duster size show that besides N = 8, N =11 is also a magic number. Furthermore, it is the first time to find that the ground state of 11-atom clusters is a biplanar structure as same as the 13-atom cluster. The clear odd-even alternation as cluster size for the formation energy indicates the stability of electronic close shell existed in the range studied.

In situ Preparation of Tri-Fe(Ⅲ) and Bi-Cu(Ⅱ) Clusters from Benzoyl Peroxide Reacting with Metal Powders

Three crystal architectures, including one organic compound of benzoyl peroxide（Ⅰ） and two clusters of tri-iron（Ⅲ） and bi-cupper（Ⅱ） with benzoic ligands（2 and 3）, were self-assembled by an in situ redox way of benzoyl peroxide oxidants reacting with Mo, Fe and Cu powders, respectively. X-ray crystallographic results show that both the asymmetry tri-iron（Ⅲ） cluster and the benzoylperoxide crystal architecture（2 and 1） with complicated 3D networks were constructed by intermolecular hydrogen-bonding interactions. Contrarily, the symmetrical bi-copper（Ⅱ） cluster crystal architecture（3）, only with π-π stacking between paralleled phenyl groups and without any intermolecular hydrogen-bonding interactions, only presented an 1D zigzag chain along the a-axis.

Synthesis, Crystal Structure and Spectroscopic Properties of an Octanuclear V-S-Cu Cluster {V_2S_6Cu_6}(PPh_3)_6(O)_2·2CH_2Cl_2·CH_3OH with a Metal-sulfur Dodecahedral Cage

A new octanuclear VSCu cluster {V2S6Cu6}(PPh3)6(O)22CH2Cl2CH3OH 1 has been prepared by extraction with CH2Cl2 of a solid mixture of (NH4)3VS4, Cu(PPh3)2Cl and NEt4Br, and its structure has been determined by single-crystal X-ray diffraction. Crystallographic data: C111H98Cl4Cu6O3P6S6V2, Mr = 2248.99, triclinic space group P , a = 13.751(6), b = 15.509(4), c = 15.642(5) ? a =114.34(2), b = 98.35(3), g = 110.43(3) , V = 2679.83 3, Z = 1, Dc = 1.538 g/cm3, F(000) = 1262, m (MoKa) = 16.9 cm-1, the final R = 0.079 and Rw = 0.083 for 5504 observed reflections with I > 2s(I). The structural determination shows that the skeleton can be described as a metal-sulfur dodecahedral cage fused by two incomplete cubane-like [VS3Cu3] subunits centrosymmetrically connected by CuS and weak CuCu bonds. The six copper and two vanadium atoms display a slightly distorted cubic array with a m4-S atom on each face of the metal cube. The selected IR, electronic and 51V NMR spectra have also been reported.

Synthesis and Crystal Structure of an Incomplete Cubane-like Heterobimetallic Cluster [（η^5-C5Me5）2Mo2（μ3-S）（μ-S）3（CuCl）]

The reaction of[（η^5-C5Me5）2Mo2（μ3-S）（μ-S）3（CuCl）]1 with Na2S in MeCN produced a trinuclear cluster [（η^5-C5Me5）2Mo2（μ3-S）（μ-S）3（CuCl）] 2. 2 crystallizes in the monoclinic system, space group P21/c with a = 15.563（3）, b = 8.9547（18）, c = 17.846（4） A, β = 101.29（3）°, V = 2438.9（9） A^3, Z = 4, Dc = 1.878 g/cm^3, T = 193（2） K, C20H30ClCuMo2S4, Mr = 689.60, F（000） = 1376, μ（MoKa） = 2.335 mm ^-1, S = 1.050, R = 0.0305 and wR = 0.0688 for 4033 observed reflections with I 〉 20-（I）. In the structure of 2, one [（η^5-C5Me5）2Mo2（μ-S）2S] moiety and one CuCI unit are assembled into an incomplete cubane-like [Mo2S4Cu] core framework, in which the Cu center adopts a distorted tetrahedral geometry coordinated by one ,μ3-S atom, two μ-S atoms and one terminal chloride. The two Mo…Cu contacts are 2.7519（7） and 2.7689（8） A, respectively.

Synthesis and Crystal Structure of Tetrakis (4-methylpyridine) bis(μ_4-pentathio)-tetracopper(Ⅰ) (4-methylpyridine) solvate

The red chunk title compound [Cu4(S5)2(4-Mepy) 4]?4-Mepy) was obtained by the reaction of copper powder with sulfur powder, potassium sulfide and excess 4-methylpyridine at ambient temperature and normal atmosphere. Its structure was determined by single-crystal X-ray diffraction analysis, and the crystal data for the compound: triclinic, P , a = 9.7442(2), b = 14.124(3), c = 15.410 (3) ? ?= 98.96(3), ?= 93.82(3), ?= 94.08(3)? V = 2083.7(7) ?3, Z = 2, Dc = 1.66 g/cm3, (MoK? = 1.31mm-1, F(000) = 1052,C30H35N5S10Cu4,Mr = 1040.45. The structure was refined to R = 0.0393 and wR = 0.1158 for 9281 independent reflections. The title crystal consists of a neutral complex molecule [Cu4(S5)2(4-CH3C5H4N)4] and a 4-methylpyridine solvent molecule. In the neutral complex, the four Cu atoms are in a distorted tetrahedral arrangement and the nonbonding Cu…Cu distances in the copper tetrahedron range from 3.1414 to 3.8488 , and the CuS bond lengths vary from 2.2839 to 2.3670 ?

Synthesis and Crystal Structure of an Octa-nuclear V-Cu-S Cluster:[VS_3O(CuPBu_3)_2(CuSPBu_3)]_2

The title compound has been synthesized by reaction of (NH4)3VS4,CuCl, and PBu3 in CH2Cl2 and its structure was determined by single crystal X-raydiffraction. Crystallographic data: C72 H162 Cu6O2P6S8V2, Mr= 1985. 57, monoclinicspace group C2/c, a= 17. 864(3), b= 25. 946(8), c= 24.071 (7),β= 112. 79(2)°,V = 10285. 9, Z= 4, Dc= 1. 28 g/cm3, F(000) = 4192, μ(MoKa) = 16. 7 cm-1,the final R=0.065 and Rw =0.074 for 4051 unique reflections with I> 3σ(I). Thestructure can be described as a metal-sulfur dodecahedral cage fused by two incompletecubane-like VS3Cu3 units connected by Cu - S bonds. The Cu - S bonds within theasymmetric VS3Cu3 unit are slightly shorter than those linking the two centrosymmetrically related VS3Cu3 units. The six copper and two vanadium atoms display asomewhat distorted cubane array with a μ4-S atom on each face of the metal cubane.