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161.
A regular polyhedron is isomorphic to a cluster on which every face has same number of bonds and every atom has an equal number of coordinating atoms. A general strategy for generating the eigenvectors and the eigenvalues of regular polyhedra is given. Not sign analyses are also performed on the eigenvectors of regular polyhedra. The results provide us a quick way to grasp the topological feature of the electronic structure of clusters having interesting topology. 相似文献
162.
The crystal structure of Zr3N4 is shown to crystallize in the centrosymmetric space group Pnam rather than in the noncentrosymmetric space group Pna21. 相似文献
163.
The reaction of Os3(CO)10(NCMe)[Si(OMe)3](-H),1, with PMe2Ph yielded the new complex Os3(CO)10(PMe2Ph)[Si(OMe)3](-H),2 by substitution of the MeCn ligand with the phosphine ligand. When heated to 125°C compound2 was decarbonylated and transformed into the new unsaturated cluster complex Os3(CO)8[-PMe2(C6H4)][Si(OMe)3](-H)2,3 in 54% yield. Compound3 was characterized by a single crystal X-ray diffraction analysis, osmium bonds. The phenyl ring of the phosphine ligand has undergoneortho-metallation by a neighboring metal atom. A terminally coordinated Si(OMe)3 ligand is coordinated to the third osmium atom. The cluster is unsaturated by the amount of 2 electrons, and there is an open coordination site on the siloxyl substituted osmium atom that is partially filled by a weak interaction with one of the -bonds of theortho-metalled phenyl ring. Complex3 reacts with CO at 1 atm to reform compound2 in 85% yield in 5 h at 40°C. Crystal Data: for3: space group = P21/n,a = 9.911(2) Å,b = 18.451(6) Å,c = 14.872(2) Å, = 95.64(2)°,Z = 4, 1994 reflections,R = 0.028. 相似文献
164.
The polyoxo rare-earth core
(Ln = Y, Gd, and Yb) has been synthesized from the appropriate rare-earth chloride hydrate and K2Se and Se in dmf (dimethylformamide). The cluster core is ligated with a variety of polyselenido chains in addition to a number of dmf molecules. The structure of the Gd8(dmf)13(4-O)(3-OH)12(Se3)(Se4)2(Se5)2 cluster, 1, was determined by X-ray diffraction methods. It is similar to an Eu cluster previously characterized. Two new clusters, Yb8(dmf)11(4-O)(3-OH)12(Se4)2(Se5)2Cl2·dmf, 2, and Y8(dmf)12(4-O)(3-OH)12(Se4)4Cl2·6 dmf, 3, have also been synthesized and characterized. Clusters 2 and 3 have the same octanuclear core of rare-earth atoms as the Gd cluster but contain two chloro ligands in two isomeric conformations in place of the Se
3
2-
ring in the Gd cluster. The geometry of the Ln
8 core is described as a triangulated dodecahedron with 3-OH groups capping the 12 faces. A 4-O atom centers the cluster with close contacts to four Ln atoms in an approximate tetrahedral arrangement. Pertinent crystallographic data are: Compound 1, monoclinic,
, a= 14.410(3) Å, b = 24.439(5) Å, c = 28.927(6) Å, = 101.05(3)°, V = 9998(3) Å3, T = 106(2) K, Z = 4; Compound 2, orthorhombic,
, a = 17.049(9) Å, b = 24.68(1) Å, c = 45.03(2)Å, V = 18,945(16) Å3, T = 153(2) K, Z = 8; Compound 3, monoclinic, C
2h
5
-P21/c, a =18.728(l) Å, b = 29.263( 1) Å, c = 20.548(1) Å, = 90.144(1)°, V = 11,261(1) Å3, T = 153(2) K, Z = 4. 相似文献
165.
晶态氮化碳薄膜的低温合成 总被引:1,自引:0,他引:1
The synthesis of carbon nitride films at low temperature has been investigated using pulsed arc discharge from methanol solution with nitrogen atmosphere. Raman spectra and X-ray diffraction (XRD) analysis suggest that crystalline carbon nitride films may be prepared at low substrate temperature (220 ℃). At same time, the substrate temperature has a significantly effect on the nitrogen content and structure of the films. Increasing substrate temperature (300 ℃) would decrease the content of nitrogen in the films and result in a formation of carbon films. 相似文献
166.
《Electroanalysis》2006,18(15):1493-1498
Titanium nitride was used as pH‐sensitive material to fabricate all solid‐state pH electrode. The fabrication and the response performance of the pH electrode were described in the paper. The TiN film electrode showed a linear response in the pH range of 2–12 with a near‐Nenstian response (?55 mV/pH). The response time was within 1 min, and the electrode had good reproducibility, stability and low sensitivities for different species. Compared with the glass pH electrode, the electrode exhibited some advantages, for example, without activation, rapid response and high mechanical strength. In addition, the electrode performed excellently in a corrosion medium containing F?(1 M). Electrochemical behaviors of TiN electrode in Britton‐Robinson buffers were studied with Electrochemical Impedance Spectroscopy (EIS). 相似文献
167.
Lieve A. De Bock Boris Treiger Ludo Van der Auwera René E. Van Grieken 《Mikrochimica acta》1998,128(3-4):191-200
To reveal useful environmental information which is contained in large analytical data sets, an approach, based on the successive application of hierarchical cluster analysis and factor analysis, is proposed. Estimation criteria to determine the most suitable number of clusters and/or factors, are discussed and the interpretation of the cluster and factor analyses results is performed using visual techniques. The data sets were obtained by scanning electron microscope-energy-dispersive X-ray analysis of individual North Sea aerosol particles. 相似文献
168.
Marx T Mosel B Pantenburg I Hagen S Schulze H Wesemann L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(18):4472-4478
The tetrasubstituted polyanions of platinum, palladium, and gold [M(SnB(11)H(11))(4)](x-) (x=6, M=Pd, Pt; x=5, M=Au) have been prepared and characterized by single-crystal X-ray diffraction, elemental analysis, IR, Raman, (11)B, and (119)Sn heteronuclear NMR spectroscopy. In the case of the platinum derivative [Bu(3)MeN](6)[Pt(SnB(11)H(11))(4)] (2) (119)Sn M?ssbauer spectroscopy has been carried out. The isolated salts are stable towards moisture and air and the complexes 2 and 3 were treated with 1,3-bis(diphenylphosphino)propane (dppp) to give the respective substitution products [Bu(3)MeN](2)[(dppp)M(SnB(11)H(11))(2)] (M=Pd, Pt). 相似文献
169.
The composition, overall stability constant and molar absorptivity of the chelate of gallium(III) ion with semimethylthymol blue, SMTB, were determined spectrophotometrically in acetate buffer (pH 4.5–5). A violet Ga(SMTB) chelate was formed with logarithmic overall stability constant of 18.0±0.1 (I=0.1) and molar absorptivity of 4.25×104l mol–1cm–1 (max 580 nm). SMTB is proposed as a new reagent for the spectrophotometric determination of micro-molar amounts of gallium(III). The colour development depends on time, temperature, pH and buffer species. The interference of different cations, anions and organic acids on gallium(III) determination was also investigated. Beer's law was obeyed for 3.5–31.3 gGa(III)/25ml (0.14–1.25 g ml–1). SMTB was used for the spectrophotometric determination of gallium in different grade minerals and ores and the results were of acceptable error and relative standard deviation. Comparison between the two suggested methods and atomic absorption spectrometry for Ga(III) determination was carried out. 相似文献
170.
Bradley D. Fahlman Andrew D. Daniels Gustavo E. Scuseria Andrew R. Barron 《Journal of Cluster Science》2002,13(4):587-599
Thermodynamic and mechanistic features of the chalcogen exchange reaction between [RGa(
3-Te)]4 and elemental sulfur or selenium have been studied employing density functional theory (DFT) calculations using the BL3YP basis set and Stuttgart pseudopotentials. For [MeGa(
3-E)]4 (E=S, Se, Te) the correlation between the calculated parameters and diffraction data for their isolable analogs is greater than 98%. Each step of the conversion of [MeGa(
3-Te)]4 to [MeGa(
3-E)]4 via [Me4Ga4(
3-Te)4–x
(
3-E)
x
] (E=S, Se) is predicted to occur as a series of isolated reactions. The entropy change for each chalcogen exchange is small in magnitude and corresponds to the degree of cage distortion within the cubane molecules. Calculations performed on [MeGa(
3-Te)]4...S8 and [MeGa(
3-Te)]4-S suggest that an increase in electrophilicity of the gallium next to a surface bound tellurium may result in nucleophilic cage opening for which intermediate structures are calculated. 相似文献