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1.
Density functional GGA-PW91 method with DNP basis set is applied to optimize the geometries of Ag n H (n = 1–10) clusters. For the lowest energy geometries of Ag n H (n = 1–10) clusters, the hydrogen atom prefers to occupy the two-fold coordination bridge site except the occupation of single-fold coordination site in AgH cluster. After adsorption of hydrogen atom, most Ag n structures are slightly perturbed and only the Ag6 structure in Ag6H cluster is distorted obviously. The Ag–Ag bond is strengthened and the strength of Ag–H bond exhibits a clear odd–even oscillation like the strength of Au–H bond in Au n H clusters, indicating that the hydrogen atom is more favorable to be adsorbed by odd-numbered pure silver clusters. The adsorption strength of small silver cluster toward H atom is obviously weaker than that of small gold cluster toward H atom due to the strong scalar relativistic effect in small gold cluster. The pronounced odd–even alternation of the magnetic moments is observed in Ag n H systems, indicating that the Ag n H clusters possess tunable magnetic properties by adsorbing hydrogen atom onto odd-numbered or even-numbered small silver cluster.  相似文献   

2.
An all-electron scalar relativistic calculation on Cu n H (n = 1–13) clusters has been performed by using density functional theory with the generalized gradient approximation at the PW91 level. Our results reveal that the hydrogen atom prefers to occupy the two fold coordination site for Cu n H (n = 2, 4–6, 8, 10–13) clusters, the single fold coordination site for Cu n H (n = 1, 3, 7) and the three fold coordination site for Cu9H cluster. For all Cu n H clusters, only the Cu11 structure in Cu11H is distorted obviously. After adsorption, the Cu–Cu bond is strengthened and the Cu–H bond of odd-numbered Cu n H clusters is relatively stronger than that of adjacent even-numbered Cu n H clusters. The Cu–Cu bond-length and Cu–H bond-length for all Cu n H clusters of our work are significantly shorter than those of previous work. This discrepancy can be explained in terms of the scalar relativistic effect. The most favorable adsorption between small copper clusters and hydrogen atom takes place in the case that hydrogen atom is adsorbed onto an odd-numbered pure Cu n cluster and becomes Cu n H cluster with even number of valence electrons. The odd–even alteration of magnetic moments is observed in Cu n H clusters and may provide the material with tunable code capacity of “0” and “1” by adsorbing a hydrogen atom onto odd- or even-numbered copper clusters.  相似文献   

3.
The geometries, electronic, and magnetic properties of the Au7Hn (n = 1–10) clusters have been systematically investigated by using relativistic all-electron density functional theory with generalized gradient approximation. It is found that the Au7 on the whole retains its triangle structure after hydrogen atoms adsorption and adsorbing hydrogen atoms can stabilize the Au7 structure. The Au7H7 cluster is much higher stability than the neighboring clusters. The pronounced even–odd alternation of the magnetic moments is observed in the Au7Hn systems indicating Au7Hn clusters possess tunable magnetic properties by adding even or odd number of H atoms.  相似文献   

4.
Density functional theory has been performed to investigate the interaction of H2 and Pdn clusters (n = 1–7). The local minima configurations for different H2 molecule approach modes towards Pdn clusters are presented. Our results show that in some cases H2 is physically adsorbed around Pd atom, and in other cases H2 is dissociated to be H atoms. Except for PdH2, Pdn clusters with H atoms dissociatively adsorbed are most stable. For these most stable PdnH2 clusters (n  2), the binding energy of hydrogen atom decreases as the number of Pd atom increases until n = 4, and when n  4, the binding energy almost keeps constant with the H atoms bound sites changing from Pd–Pd bonds to Pd triangle planes. Besides, the adsorption of H2 on other low-lying isomers of Pdn clusters is also discussed.  相似文献   

5.
We perform density functional theory calculations using Gaussian atomic-orbital methods within the generalized gradient approximation for the exchange and correlation to study the interactions in the bare and hydrogenated platinum clusters. The minimum-energy structures, binding energies, relative stabilities, vibrational frequencies and the highest occupied and lowest unoccupied molecular-orbital gaps of PtnHm (n = 1–5, m = 0–2) clusters are calculated and compared with previously studied pure platinum and hydrogenated platinum clusters. We investigate any magic behavior in hydrogenated platinum clusters and find that Pt4H2 is more stable than its neighboring sizes. The lowest energy structure of Pt4 is found to be a distorted tetrahedron and that of Pt5 is found to be a bridge site capped tetrahedron which is a new global minimum for Pt5 cluster. The successive addition of H atoms to Ptn clusters leads to an oscillatory change in the magnetic moment of Pt3–Pt5 clusters.  相似文献   

6.
The lowest-energy configurations, electronic structures and magnetic moments of small Lu n (n = 2–20) clusters have been investigated within the framework of density functional theory. The results show that Lu n (n = 4, 8, 13, and 18) clusters are more stable than their respective neighbors, and structural transformation reveals at n = 16. As the number of atoms increases, the magnetic moments increase in an alternating fashion until they reach a maximum of 4.00 μB for Lu8 clusters, followed by even–odd oscillation between 0.00 and 1.00 μB over the range n = 9–20.  相似文献   

7.
The geometries, stabilities, and electronic properties of Au n La (n = 2–8) clusters have been systematically investigated by using density-functional theory. The results show that the doped La atom prefers to locate at the center site with the number of Au atom increasing from 2 to 8. Furthermore, the Au n La clusters are more stable than the Au n+1 clusters. The charges transfer from La atom to Au atoms at n = 2–4, but charge-transferring is reversed at n = 5.  相似文献   

8.
《Solid State Sciences》2012,14(5):611-615
Three new ionic crystals based on Keggin anion and mixed-valent diruthenium tetracetate, [Ru2(CH3CO2)4(H2O)2]2[HnXW12O40]·[Ru2(CH3CO2)4(H2O)Cl]·12H2O {X = B, n = 3 (1); X = Si, n = 2 (2); X = Ge, n = 2 (3)}, have been prepared in acidic aqueous solution at about pH 3.0 by reaction of K4BW12O40·mH2O, K8SiW11O39·mH2O and K8GeW11O39·mH2O with diruthenium tetracetate Ru2(CH3COO)4Cl, respectively, and their structures were determined by X-Ray diffraction analysis. They are isostructural structure with the ratio of heteropolytungstate anion, Ru2(CH3CO2)4+ cation and neutral molecular Ru2(CH3CO2)4Cl of 1:2:1. The cyclic voltammetry in 0.5 M KNO3 aqueous solution at pH 3.0 show the respective electrochemical behaviors of the W-centers and Ru2-centers for these three complexes. Magnetic data analysis shows that diruthenium units display the ground state electronic configuration π*2δ* with large positive D value.  相似文献   

9.
Reactions of substituted pyridylalkanol 6-CH3PyCH2CH(OH)R (R = Ph (L1H), R = 4-CH3C6H4 (L2H), R = 4-OCH3C6H4 (L3H), R = 4-ClC6H4 (L4H), R = 4-BrC6H4 (L5H), R = 4-CF3C6H4 (L6H)) with Ru3(CO)12 in refluxing tetrahydrofuran afforded the corresponding ruthenium carbonyl complexes [6-CH3PyCH2CHRO]2Ru3(CO)8 (R = Ph ( 1a ), R = 4-CH3C6H4 ( 1b ), R = 4-OCH3C6H4 ( 1c ), R = 4-ClC6H4 ( 1d ), R = 4-BrC6H4 ( 1e ), R = 4-CF3C6H4 ( 1f )) in good yields. These ruthenium complexes were well characterized using elemental analysis and Fourier transform infrared and NMR spectroscopies. Furthermore, their crystal structures were determined using single-crystal X-ray diffraction analysis. Complexes 1a – 1f were found to be highly active toward oxidation of a wide range of primary and secondary alcohols to corresponding aldehydes and ketones within 5 minutes in the presence of N-methylmorpholine-N-oxide as oxidant.  相似文献   

10.
New Schiff base (H2L) ligand is prepared via condensation of o-phthaldehyde and 2-aminophenol. The metal complexes of Cr(III), Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) with the ligand are prepared in good yield from the reaction of the ligand with the corresponding metal salts. They are characterized based on elemental analyses, IR, solid reflectance, magnetic moment, electron spin resonance (ESR), molar conductance, 1H NMR and thermal analysis (TGA). From the elemental analyses data, the complexes are proposed to have the general formulae [M(L)(H2O)nyH2O (where M = Mn(II) (n = 0, y = 1), Fe(II) (n = y = 0), Co(II) (n = 2, y = 0), Ni(II) (n = y = 2), Cu(II) (n = 0, y = 2) and Zn(II) (n = y = 0), and [MCl(L)(H2O)]·yH2O (where M = Cr(III) and Fe(III), y = 1–2). The molar conductance data reveal that all the metal chelates are non-electrolytes. IR spectra show that H2L is coordinated to the metal ions in a bi-negatively tetradentate manner with ONNO donor sites of the azomethine N and deprotonated phenolic-OH. This is supported by the 1H NMR and ESR data. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral (Cr(III), Fe(III), Co(II) and Ni(II) complexes), tetrahedral (Mn(II), Fe(II) and Zn(II) complexes) and square planar (Cu(II) complex). The thermal behaviour of these chelates is studied and the activation thermodynamic parameters, such as, E*, ΔH*, ΔS* and ΔG* are calculated from the DrTGA curves using Coats-Redfern method. The parent Schiff base and its eight metal complexes are assayed against two fungal and two bacterial species. With respect to antifungal activity, the parent Schiff base and four metal complexes inhibited the growth of the tested fungi at different rates. Ni(II) complex is the most inhibitory metal complex, followed by Cr(III) complex, parent Schiff base then Co(II) complex. With regard to bacteria, only two of the tested metal complexes (Mn(II) and Fe(II)) weakly inhibit the growth of the two tested bacteria.  相似文献   

11.
Reactions of pyridine imines [C5H4N‐2‐C(H) = N‐C6H4‐R] [R = H (1), CH3 (2), OMe (3), CF3 (4), Cl (5), Br (6)] with Ru3(CO)12 in refluxing toluene gave the corresponding dinuclear ruthenium carbonyl complexes of the type {μη2‐CH[(2‐C5H4N)(N‐C6H4‐R)]}2Ru2(CO)4(μ‐CO) [R = H (7); CH3 (8); OMe (9); CF3 (10); Cl (11); Br (12)]. All six novel complexes were separated by chromatography, and fully characterized by elemental analysis, IR, NMR spectroscopy. Molecular structures of 7, 10, 11, and 12 were determined by X‐ray crystal diffraction. Further, the catalytic performance of these complexes was also tested. The combination of {μη2‐CH[(2‐C5H4N)(N‐C6H4‐R)]}2Ru2(CO)4(μ‐CO) and NMO afforded an efficient catalytic system for the oxidation of a variety secondary alcohols.  相似文献   

12.
The adsorption and dissociation of molecular oxygen on spinel CuCr2O4 (100) surface were carried out by first-principles calculations based on density functional theory (DFT). The calculated results indicate that the Cr site is most favorable for atomic oxygen adsorption, with an adsorption energy of 402.8 kJ/mol. For molecular oxygen adsorption, there are three types of favorable interaction modes: O2 forms bonds with the Cu site or O2 binds to two Cr sites or O2 interacts with both Cu and Cr sites simultaneously. The lowest activation energy (Ea = 35.4 kJ/mol) was found through exploring possible reaction pathways for O2 dissociation. The relationship between Ea and reaction enthalpy (ΔH) for O2 dissociation adsorption reactions fits Brønsted-Evans-Polanyi (BEP) behavior.  相似文献   

13.
Mixed-chelate complexes of ruthenium have been synthesized using tridentate Schiff-base ligands (TDLs) derived from condensation of 2-aminophenol or 2-aminobenzoic acid with aldehydes (salicyldehyde, 2-pyridinecarboxaldehyde), and tmeda (tetramethylethylenediamine). [RuIII(hpsd)(tmeda)(H2O)]+ (1), [RuIII(hppc)(tmeda)(H2O)]2+ (2), [RuIII(cpsd)(tmeda)(H2O)]+ (3) and [RuIII(cppc)(tmeda)(H2O)]2+ (4) complexes (where hpsd2− = N-(hydroxyphenyl)salicylaldiminato); hppc = N-(2-hydroxyphenylpyridine-2-carboxaldiminato); cpsd2− = (N-(2-carboxyphenyl)salicylaldiminato); cppc = N-2-carboxyphenylpyridine-2-carboxaldiminato) were characterized by microanalysis, spectral (IR and UV–vis), conductance, magnetic moment and electrochemical studies. Complexes 14 catalyzed the epoxidation of cyclohexene, styrene, 4-chlorostyrene, 4-methylstyrene, 4-methoxystyrene, 4-nitrostyrene, cis- and trans-stilbenes effectively at ambient temperature using tert-butylhydroperoxide (t-BuOOH) as terminal oxidant. On the basis of Hammett correlation (log krel vs. σ+) and product analysis, a mechanism involving intermediacy of a [Ru–O–OBut] radicaloid species is proposed for the catalytic epoxidation process.  相似文献   

14.
Abstract  Two new coordination polymers, [CoL(bpp)] n (1) and [MnL(bipy)] n ·0.25nH2L·0.5nH2O (2) (H2L = 1,3-adamantanediacetic acid, bpp = 1,3-bis(4-pyridyl)propane, bipy = 4,4′-bipyridine), were synthesized and characterized by single crystal X-ray diffraction, IR spectroscopy, and thermal analysis. Complex 1 is an one-dimensional (1D) chain structure of Co(II) bridged by L2− as well as bpp. Complex 2 consists of a two-dimensional (2D) (3,6)-connected topology layer structure. Variable temperature magnetic susceptibility measurements in the range of 2–300 K reveal the existence of weak antiferromagnetic interactions in two complexes with J = −1.74 cm−1, g = 2.26 for 1 and J = −0.10 cm−1, g = 1.67 for 2. Index abstract  Two mental-organic frameworks, namely [CoL(bpp)] n (1) and [MnL(bipy)] n ·0.25nH2L·0.5nH2O (2) (H2L = 1,3-adamantanediacetic acid, bpp = 1,3-bis(4-pyridyl)propane, bipy = 4,4′-bipyridine), have been synthesized based on 1,3-adamantanediacetic acid and N-donor coligand with metal ions Co(II) and Mn(II). The magnetic measurement of the two polymers reveals typical antiferromagnetism exchange. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

15.
The structural, energetic and magnetic properties of MnC(M = Fe, Co, Ni, Cu, n = 1–6) clusters are systematically investigated by density-functional calculations. We found that the ground-state geometrical structures of MnC clusters are different from those of pure Mn+1 clusters. Fe4C, Ni2C and Cu4C possess relatively higher stabilities. Doping of a C atom enhances the binding energy of Mn clusters, and the binding energies of Fen-C, Con-C and Nin-C are stronger than that of Cun-C.  相似文献   

16.
Using density functional theory we present a systematic study of the electronic and magnetic properties of various nickel clusters and two small bimetallic clusters, Ni n Co m and Ni n Fe m (n + m ≤ 6). A detail study of binding energy, magnetic moment and stability function of pure nickel clusters of nuclearity (N) 40–60 have been performed. We observe that the magic numbers occur at N = 43, 46, 49, 53, 55, and 58, which correspond to the most stable clusters. We find that, with increase in substitution of Co and Fe atoms in Ni cluster, while Ni n Co m becomes more stable, the Ni n Fe m clusters become less stable. The significant enhancement of average magnetic moment and suppression of local magnetic moment of nickel atoms are found in both clusters with increase in Co and Fe concentration.  相似文献   

17.
An all-electron scalar relativistic calculation on Au n AgCO (n = 1–12) clusters has been performed using density functional theory with the generalized gradient approximation at PW91 level. The introduction of impurity silver weakens the adsorption, and, however, promotes the reactivity enhancement of CO molecule. The CO molecule is relatively more favorable to be adsorbed by the odd-numbered Au n Ag clusters with closed-shell electronic structure. The values of chemical hardness indicate that the Au n AgCO cluster is less stable than the corresponding Au n+1CO cluster chemically. This picture of the influence of impurity silver on the adsorption behavior of Au n Ag (n = 1–12) clusters toward CO molecule is consistent with previous experimental work (Haeck et al. in J Phys Chem A 115:2103, 2011), in which the cluster’s reaction probability toward CO molecule is reduced upon substitution of gold atoms for silver and the clusters with closed electronic shell are the most reactive toward CO molecule.  相似文献   

18.
The difurylphosphido-bridged dinuclear complex [Ru2(CO)6(μ-PFu2)(μ-η12-Fu)] (Fu = 2-furyl) 1 readily reacts with two equivalents of each of the terminal alkynes HC≡CR (R = Fc, p-C6H4Fc, p-C6H4NO2, Fc = Fe(η5-C5H5)(η5-C5H4)) by an interesting head-to-tail ynyl coupling with a furan group to form a series of phosphido-bridged diruthenium compounds containing a novel furyl-substituted C4 hydrocarbyl chain of stoichiometry [Ru2(CO)4(μ-PFu2){μ-η1123-RCC(H)C(R)C(H)Fu}] (R = Fc 2, p-C6H4Fc 3, p-C6H4NO2 4) in moderate to good yields. Reaction of 1 with an equimolar amount of HC≡CFc and HC≡C(p-C6H4NO2) afforded a pair of isomers of [Ru2(CO)4(μ-PFu2){μ-η1123-R1CC(H)C(R2)C(H)Fu}] (R1 = Fc, R2 = p-C6H4NO2 5a; R1 = p-C6H4NO2, R2 = Fc 5b) together with a small mixture of 4. X-ray crystal structures of 2, 3, 5a and 5b are reported. All of these new alkyne-derived dinuclear complexes are electron precise with 34 cluster valence electrons in which the μ-η12-furyl ligand acts as a three-electron donor and the μ-phosphido Ru2 framework is retained in the products upon alkyne coupling reactions. The resulting organic fragment of each complex is coordinated to the Ru atoms via a π, a π-allyl and two σ bonds, and donates seven electrons to the metal core. Dedicated to the memory of Professor F. Albert Cotton.  相似文献   

19.
The interaction of ammonia with Ben (n < 1–10) clusters has been investigated by density functional theory and ab initio calculations. The main conclusion is that, regardless of the size of the Be cluster, neither the structure of ammonia nor that of the Be clusters are preserved due to a systematic dissociation of its N H bonds and a spontaneous H-shift toward the available Be atoms. This H migration not only leads to rather stable Be H bonds, but dramatically enhances the strength of the Be N bonds as well. Accordingly, the maximum stability is found for the interaction with the beryllium trimer, leading to a complex with three N Be and three Be H bonds. Another maximum in stability, although lower than that reached for n = 3, is found for the Be heptamer, since from n = 6, a new N Be bond is formed, so that complexes from n = 6 to n = 10 are characterized by the formation of a NBe4 moiety, whose stability reaches a maximum at n = 7. The bonding characteristics of the different species formed are analyzed by means of AIM, NBO, ELF and AdNDP approaches.  相似文献   

20.
Deuterated dinuclear ruthenium(II,III) 3,4,5-tri(ethoxy-d 5)benzoate, [Ru2{3,4,5-(C2D5O)3C6H2-COO}4Cl] n , was synthesized by a reaction of [Ru2(C2H5COO)4Cl] n and 3,4,5-tri(ethoxy-d 5)benzoic acid and characterized by single-crystal X-ray analysis as well as IR, UV-VIS, and 1H NMR spectra, and compared with those of the undeuterated complex [Ru2{3,4,5-(C2H5O)3C6H2COO}4Cl] n . Single-crystal X-ray analysis showed that chloride ligands bridge the dinuclear ruthenium(II,III) units at the axial positions to form a zigzag chain molecule with the Ru1-Cl-Ru2 angle of 123.82(4)°. 1H NMR spectra in CD2Cl2 displayed a broad signal attributable to o-H atoms on the phenyl rings of the benzoate ligands from approximately δ = 23 to δ = 32 at 25°C and several signals from approximately δ = −50 to δ = 50 at −80°C. These spectra show the preservation of the polymeric or oligomeric chain structure in dichloromethane, which is supported by the solution behavior confirmed by the UV-VIS spectra and electronic conductance.  相似文献   

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