Studies on the Stability of On-top Al_(13)I_n^m(n=1～12,m=–1,0,+1) Clusters

Energetic and electronic structures of the on-top Al13In^m （n = 1 - 1 2, m = -1, 0, ＋1） clusters have been investigated by employing a first-principles pseudo-potential plane wave method. Several parameters such as binding energies, second differences of energy and vertical-electron detachment energies have been adopted to characterize and evaluate the structure stability of Al13In^- （n= 1 - 12） clusters. The optimized models show that the Al13 moieties in the clusters can not retain the original regular icosahedron structure. Results from binding energy and second difference of energy show that Al13In and Al13In^- clusters with even n are more stable than those with odd n in contrast with Al13In^＋ clusters. The calculation of vertical-electron detachment energies （VDE） of Al13In clusters indicates that Al13In and Al13In^- clusters with even n are closer to the closed shell of the Jellium model. Further analysis of electron density of states and electron density differences reveals that the enhanced stability of AI13In^- clusters is not only associated with the closed shell of valence electrons but also with the bonding type between I and associated AI atoms.

Structures and Aromaticity of Three-membered BeXP (X = C, Si, Ge) and CYP (Y = O, S, Se) Rings

Three-membered BeXP （X = C, Si, Ge） and CYP （Y = O, S, Se） rings are theoretically investigated using density functional theory （DFT） methods at the B3LYP/6-311＋G^＊ and B3PW91/6-311＋G^＊ levels of theory. The research results show that the size of atoms has a great influence on the structural stability of these species. The wiberg bond indexs （WBIs） suggest the existence of delocalization in these structures. Negative nucleus-independent chemical shift （NICS） values for these species indicate that a strong ring current exists in these three-membered structures （Cs symmetry）. A detailed molecular orbital （MO） analysis further reveals that a delocalized π MO strengthens the structural stability and makes these species show strong aromatic characters.

Color-texture segmentation using JSEG based on Gaussian mixture modeling

An improved approach for J-value segmentation （JSEG） is presented for unsupervised color image segmentation. Instead of color quantization algorithm, an automatic classification method based on adaptive mean shift （AMS） based clustering is used for nonparametric clustering of image data set. The clustering results are used to construct Gaussian mixture modelling （GMM） of image data for the calculation of soft J value. The region growing algorithm used in JSEG is then applied in segmenting the image based on the multiscale soft J-images. Experiments show that the synergism of JSEG and the soft classification based on AMS based clustering and GMM overcomes the limitations of JSEG successfully and is more robust.

Application of R-Mode Cluster Analysis to Multielement Taxonomy of Early Triassic Conodonts

The multivariate statistical analysis is profitably applicable to the study of conodont multielement taxonomy.R- mode duster analyses of quantitative and 0-1 data are carried out here to classify more than 6000 discrete Lower Triassic conodont specimens belonging to 108 kinds of conodont elements from Western Guangxi . The results of R-mode cluster analysis reveal more directly the relationship among many isolated conodont elements , and they also prove that the results of the logical inference are basically correct,i.e. 108 kinds of conodont elements can be identified into 32 species belonging to 11 genera of conodonts . The application of R- mode duster analysis multielement taxonomy by the method . has brought about 4 significant conclusions , which can be used by conodont researchers as reference .

Synthesis and Crystal Structure of a New Mo/Au/S Cluster [Et_4N][Mo_2S_4(AuPPh_3)(edt)_2]· 0.25Et_2O·0.25MeOH(edt=Ethanedithiolate)

Reactions of the preformed cluster precursor [Et4N]2[Mo2S2（μ-S）2（edt）2] （edt = ethanedithiolate） （1） with [Au（PPh3）Cl] in MeOH/MeCN gave rise to a new heterobimetallic Mo/Au/S cluster [Et4N][Mo2S4（AuPPh3）（edt）2]·0.25Et2O·0.25MeOH （2·0.25Et2O·0.25MeOH）. It was characterized by elemental analysis, IR spectrum and X-ray analysis. 2·0.25Et2O·0.25MeOH crystallizes in the monoclinic system, space group C2/c with a = 20.117（4）, b = 9.2705（19）, c = 44.418（9） A^°, β= 93.19（3）°, V = 8271（3） A^°^3, Z = 8, Dc = 1.794 g/cm^3, T = 193 K, C31.25H43AuMo2NO0.50PS8, Mr = 1116.96, F（000） = 4380, μ（MoKa） = 4.603 mm^-1, S = 1.019, R = 0.0672 and wR = 0.1708 for 7243 observed reflections with I 〉 2σ（I）. The anion of 2 consists of a butterfly-shaped Mo2S4Au core in which one [AuPPh3]^＋ cation is coordinated by one bridging S and two terminal S atoms of the [（edt）2Mo2（S）2（μ-S）2] moiety. The Au（I） center adopts a pseudo-tetrahedral coordination geometry, and the Au-S bond lengths vary from 2.425（2） to 2.898（3）A^°.

Three New d^(10) Coordination Polymers with Arenedisulfonates:Syntheses,Crystal Structures and Luminescent Properties

Three new cadmium or zinc arenedisulfonate complexes [Zn（bpp）2（L）]n 1, { [Cd（bpp）2（1,5-NDS）（H2O）2]·4H2O }n 2 and { [Cd（bpp）2（H2O2）2]·（1,5-NDS） } n 3 （L = 4,4′-bis（2-sulfonatostyryl）biphenyl, bpp = 1,3-di（4-pyd-dyl）propane and 1,5-NDS = 1,5-Naphthalenedisulfonate） have been synthesized from aqueous solution and structurally characterized by infrared spectroscopy, elemental analysis and single-crystal X-ray diffraction. Crystal data for complex 1： space group P21/n, a = 10.559（3）, b = 13.138（4）, c = 17.623（5）A^°, β = 100.852（3）°, V = 2400.9（12） A^°^3 Z = 2, Dc= 1.351 g/cm^3, F（000） = 1016, μ = 0.654 mm^-1, the final R = 0.0412 and wR = 0.0994; Crystal data for complex 2： space group P^-1, a = 8.5642（19）, b = 10.076（3）, c = 12.114（3） A^°, α = 81.623（7）, β = 77.149（8）, γ = 82.787（7）°, V = 1003.6（4） A^°^3 Z = 1, Dc= 1.495 g/cm^3, F（000） = 466,μ = 0.713 mm^3, the final R = 0.0241 and wR = 0.0713; Crystal data for complex 3： space group C2/c, a = 21.6024（15）, b = 9.4608（5）, c = 18.4656（11）A^°, β = 107.359（3）°, V= 3602.0（4）A^°^3 Z = 4, Dc= 1.533 g/cm^3, F（000） = 1704,μ = 0.780 mm^-1, the final R = 0.0229 and wR = 0.0572. The X-ray single diffraction reveals that 1 exhibits a 3D metal-organic framework formed from 2D Zn（bpp）2^2＋ networks connected by L in the third dimension; 2 and 3 possess 3D and 2D architectures constructed from 1D polymeric chains through H-bond. Complexes 1-3 display photoluminescent emissions at 452 and 335 nm, respectively.

Syntheses and Characterizations of(CH_3CH_2CH_2CH_2NH_3)_6(BiI_6)(I)_2I_3 and (NH_3CH_2CH_2NH_3)_2Bi_2I_(10)

The title compounds have been respectively synthesized by solution process and solvothermal reaction, and their crystal structures were determined by X-ray diffraction method. For （CH3CH2CH2CH2NH3）6（BiI6）（I）2I3 1, it crystallizes in tficlinic, space group P1^- with Mr = 2049.76, a = 8.5719（1）, b = 11.7461（3）, c = 15.700（1）A, V = 1451.4（1）A^3, Z = 1, Dc = 2.345 g/cm^3, F（000） = 924, μ（MoKα） = 8.907 mm^-1, T = 293（2） K, the final R = 0.0655 and wR = 0.0804 for 2399 observed reflections with I 〉 2σ（I）. For （NH3CH2CH2NH3）2Bi2I10 2, it crystallizes in monoclinic, space group P21/n with Mr= 1811.20, a = 8.434（4）, b = 13.862（6）, c = 13.362（6）A, V = 1499.9（12）A^3, Z = 2, Dc = 4.010 g/cm^3, F（000） = 1536,μ（MoKα） = 22.007 mm^-1, T = 293（2） K, the final R = 0.0584 and wR = 0.1451 for 1798 observed reflections with I 〉 2σ（I）. The structures of 1 and 2 contain halobismuthate monomer and dimers, respectively. It is noteworthy that the dimers and their organic counters in 2 connect each other by N…I hydrogen bonds to form a layered structure, and the electrostatic interactions and crystal packing forces between layers give rise to the packing of the crystal. The optical absorption spectra of 1 and 2 reveal the appearance of sharp optical gaps of 2.13 and 2.01 eV, respectively.

Synthesis and Crystal Structure of a Model for the Active Sites of Fe-only Hydrogenases:[Fe_2(SCH_2)_2N(3-PhCF_3)(CO)_6]_2

A model compound for the active sites of Fe-only hydrogenases, [Fe2（SCH2）2N（3- PhCF3）（CO）6]2, has been synthesized and structurally characterized by single-crystal X-ray diffraction. It crystallizes in tetragonal, space group P43, with α = 12.6324（3）, b = 12.6324（3）, c = 24.0453（12） A, V = 3837.1（2） A^3, Z= 4, Fe4S4N2C30O12F6H16, Mr= 1062.09, Dc= 1.839 g/cm^3, μ（MoKα） = 1.791 mm^-1, F（000） = 2112, T= 293（2） K, Flack = 0.034（9）, R = 0.0282 and wR = 0.0685 for 8148 observed reflections with I 〉 20（I）. In the title compound, each Fet atom is coordinated by three terminal carbonyl C atoms （Fe-C： 1.783（3）- 1.816（3） A）, two bridging S atoms （Fe-S： 2.2609（7）-2.2757（8） A） and another Fe atom （Fe-Fe 2.5011（5） A）, adopting a distorted octahedral geometry with trans angles ranging from 152.45（11） to 157.77（10）°.

Ligand-controlled First Hyperpolarizabilities of a Series of Tetrahedral Iridium Clusters Ir_4(CO)_9L: a TDDFT Study

A series of tetrahedral iridium carbonyl clusters coordinated by systematically varied series of ligands have been studied by TDDFT method focusing on their electronic and non- linear optical properties. The clusters of Ir4（CO）12 （1）, Ir4（μ-CO）3（CO）9 （2）, Ir4（μ-L）（CO）10 （L = dppm 3, dppe 4, （Ph2P）2CHMe 5, Ph2P（CH2）3PPh2 6） and Ir4（CO）10（phen） （phen = 1,10-phen- anthroline） （7） exhibit the first static hyperpolarizabilities of medium magnitude （βtot-10×10^-30 esu）. The second order nonlinear optical response of the seven clusters increase from 0 to 23 ×10^-30 esu; the high symmetric cluster Ir4（CO）12 debases its symmetry and presents the second order nonlinear optical behavior as the coordination style of some carbonyls changes to bridge style, and then the response increases regularly with the systematical variation of the ligands. The origination of the first hyperpolarizability is discussed by the expanded orbital decomposition scheme. The results suggest the d-d electron transition from the apical iridium atom to the other three Ir atoms inside the metal skeleton, and d-πelectron transitions from metals to carbonyls are responsible for the first hyperpolarizabilities. Particularly, for cluster 7, the charge transfer from d orbitals of iridium to π＊ orbirals of phenanthroline originates the first hyperpolarizabilities.

Synthesis, structures and reaction mechanism of transition metal cluster complexes η~5-RC_5H_4(CO)_2MCo_3(CO)_6(μ-CO)_3

The tetrahedral metal-cluster complexes containing alkylcyclopentadienyl ligand η5-RC5H4(CO)2 MCo3(CO)6(μ-CO)3(M = Mo, W; R=CH3, C2H5, n-C4H9, C6H5CH2) have been synthesized by thermal reaction of metal-metal single-bonded compounds [η5-RC5H4(CO)3M]2 with Co2(CO)8, and characterized by elemental analysis, 1R, 1H NMR and MS spectroscopies. The thermal reaction mechanism is studied and a single-crystal molecular structure of η5-n-C4H9C5H4(CO)2MoCo3(CO)6(μ-CO)3 determined with the X-ray diffraction method. The molecule crystallizes in the space group P21/C with cell parameters a= 1.0088(2), b= 1.3063(3), c=1 8320(5) ran, β = 96.04(2)°; the final deviation factor R = 0.041.

总有—款惹你爱

精妙的设计和构思总是让平凡的东西在世间万物中散发出智慧的光芒，并且没有尽头，无穷无尽。一双鞋、一面镜子、古老的剪纸，当人的智慧关注到它，它们就焕发出新的生命力。不由得你不关注它、喜爱它、拥有它。生活的动力有时就是为了它们，尽管你自己也觉得这样很狭隘，但是就是舍弃不了它。