共查询到20条相似文献,搜索用时 204 毫秒
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Earl L. Muetterties 《Journal of organometallic chemistry》1980,200(1):177-190
Metal cluster chemistry is one of the most rapidly developing areas of inorganic and organometallic chemistry. Prior to 1960 only a few metal clusters were well characterized. However, shortly after the early development of boron cluster chemistry, the field of metal cluster chemistry began to grow at a very rapid rate and a structural and a qualitative theoretical understanding of clusters came quickly. Analyzed here is the chemistry and the general significance of clusters with particular emphasis on the cluster research within my group. The importance of coordinately unsaturated, very reactive metal clusters is the major subject of discussion. 相似文献
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A novel hydroxo-lanthanide cluster organic framework, Sm3L8(μ 3-OH)(H2O)·H2O (1), derived from the 4-pyridin-4-ylbenzoic acid (HL) has been hydrothermally made and structurally characterized by single crystal X-ray diffraction. Structure analysis shows the hexanuclear Sm6 cluster unit is composed of inorganic tetranuclear hydroxo [Sm4(OH)2]10+ (Sm4) cluster and dimeric [Sm2(COO)4]2+ (Sm2) core. The Sm6 cluster units are connected by L ligands to form a 2D Ln-based cluster organic framework. From the topological point of view, the layer architecture can be described as 4-connected sql net. Furthermore, the elemental analysis, PXRD, IR and TGA are also studied. 相似文献
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This paper describes the simple experimental method of size determination of gas clusters in molecular beams formed from supersonic jets. Mean cluster size N is calculated from broadening of the transverse profile of beam intensity at a fixed distance behind the skimmer. The described method allows determining the mean sizes of the clusters of any pure gases. It does not require the building of some special models, or determination of empirical constants. Due to the high intensity of the supersonic beams, the measurements do not require any complex highly sensitive equipment. The effectiveness of the present method is validated by measurements in a cluster beams of test gases (easily condensable CO2, Ar, and weakly condensable N2) and the beam of C2H4 (ethylene), formed from a supersonic jet behind conical nozzles. The certainty of measured characteristics is confirmed by the results of numerical simulations. By using the described method the mean cluster sizes from 50 to 2000 molecules per cluster were determined. The correctness of the obtained cluster sizes of CO2 and Ar is proved by comparison with results of other authors, obtained by other experimental methods, and estimations according to the empirical correlations using condensation scaling parameter Г*. 相似文献
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Brian T. Sterenberg Ravindranath Ramachandran Richard J. Puddephatt 《Journal of Cluster Science》2001,12(1):49-59
The tetranuclear platinum cluster complexes [Pt4(-CO)3(-dppm)3(PPh3)]2+ and [Pt4(-H)(-CO)2(-dppm)3(PPh3)]+ have been prepared by cluster expansion. They have butterfly structures and are fluxional. 相似文献
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We describe a method for locating clusters of geometrically similar conformers in ensembles of chemical conformations. We first calculate the pairwise interconformational distance matrix in either torsional or Cartesian space and then use an agglomerative, single-link clustering method to define a hierarchy of clusterings in the same space. Especially good clusterings are distinguished by high values of the separation ratio: the ratio of the shortest intercluster distance to the characteristic threshold distance defining the clustering. We also discuss other statistics. The method has been embodied in a program called XCluster, which can display the distance matrix, the hierarchy of clusterings, and the clustering statistics in a variety of formats. XCluster can also write out the clustered conformations for subsequent or simultaneous viewing with a molecular visualization program. We demonstrate the sorts of insight that this approach affords with examples obtained from conformational search and molecular dynamics procedures. © 1994 by John Wiley & Sons, Inc. 相似文献
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K. Hirao 《Theoretical chemistry accounts》1987,71(2-3):231-236
Numerical examples illustrate the SAC and SAC-CI results for correlatioin energies compared to those from full CI calculations of Bauschlicher and Taylor. 相似文献
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A novel cluster organic framework, Er3Cu5I4L10(H2O) (1, L = 4-pyridin-3-yl-benzonate), has been hydrothermally made and structurally characterized by single crystal X-ray diffraction. Structure analysis shows [Er3(COO)6]3+ (Er3) clusters are linked by carboxylate groups generating one dimensional wave-like chain, which further extended by Cu5I4 + (Cu5) clusters into three dimensional heterometallic cluster organic framework. From the perspective of topology, such framework defines a new (7,9)-connected net, considering Er3 and Cu5 cores as the nodes. Furthermore, the elemental analysis, powder X-ray diffraction, infrared spectra and thermogravimetric analysis are also studied. 相似文献
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Reactions between tungsten halides are discussed along the series of compounds WCl6 → WCl4 → W6Cl12 ↔ W6Cl18 → [W6CCl18]n− ← [W3Cl13]u−, focusing on the two closely related tungsten chloride compounds whose structures compromise the well-known octahedro W6Cl18 cluster and the carbon-centered triprismo W6CCl18 cluster. Both clusters can be regarded as being built by merging two trigonal [W3Cl13]u− units in different ways. Syntheses, structural transformation reactions, and concepts regarding electronic structures are
reported. 相似文献
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Piero Frediani Ugo Matteoli Mario Bianchi Franco Piacenti Gloria Menchi 《Journal of organometallic chemistry》1978,150(2):273-278
Tetraruthenium dodecacarbonyl tetrahydride and some of its phosphine-substituted derivatives have been tested as homogeneous hydrogenation catalysts. The hydrogenation of cyclohexanone in the presence of H4Ru4(CO)12 is first order with respect to the catalyst concentration, the substrate concentration and the partial pressure of hydrogen. The ruthenium cluster is recovered unchanged at the end of the reaction. 相似文献
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Crippen GM 《Journal of computational chemistry》2004,25(10):1305-1312
Distance geometry has been a broadly useful tool for dealing with conformational calculations. Customarily each atom is represented as a point, constraints on the distances between some atoms are obtained from experimental or theoretical sources, and then a random sampling of conformations can be calculated that are consistent with the constraints. Although these methods can be applied to small proteins having on the order of 1000 atoms, for some purposes it is advantageous to view the problem at lower resolution. Here distance geometry is generalized to deal with distances between sets of points. In the end, much of the same techniques produce a sampling of different configurations of these sets of points subject to distance constraints, but now the radii of gyration of the different sets play an important role. A simple example is given of how the packing constraints for polypeptide chains combine with loose distance constraints to give good calculated protein conformers at a very low resolution. 相似文献