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991.
Equilibrium geometries, interaction energies, and charge transfer for the intermolecular interactions between BrF and HnX (HF, H2O, and NH3) were studied at the MP2/6-311++G(3d,3p) level. The halogen-bonded geometry and hydrogen-bonded geometry are observed in these interactions. The calculated interaction energies show that the halogen-bonded structures are more stable than the corresponding hydrogen-bonded structures. To study the nature of the intermolecular interactions, symmetry-adapted perturbation theory (SAPT) calculations were carried out and the results indicate that the halogen bonding interactions are dominantly inductive energy in nature, while electrostatic energy governs the hydrogen bonding interactions. 相似文献
992.
The intermolecular potential function of Smith–Thakkar type for C60 has been proposed, and its expression is as followsThe unit of u(r) is J/mol, r is the distance between two C60 molecules center and the unit is nm. Some properties of C60 in the gas and crystal have been studied using the interaction potential of Smith–Thakkar type, such as stability of C60 crystals, virial coefficient and lattice dynamics. 相似文献
993.
994.
995.
996.
Anusuya Choudhury Fuqiang JinDengjin Wang Zhe WangGuoyou Xu Dieu NguyenJohn Castoro Michael E PiercePat N Confalone 《Tetrahedron letters》2003,44(2):247-250
Anti-HIV agent β-F-ddA (1) has been synthesized starting from readily available non-sugar, (S)-(+)-Dihydro-5-(hydroxymethyl)-2-(3H)-furanone (4). A highly syn-stereoselective fluorination of the hydroxy lactone 2 generates the key intermediate fluorolactone 5 in a short and concise synthetic sequence. Reduction of 5 followed by bromination generates the aglycon which is glycosylated to generate F-ddA by amination and deprotection. Steric bulk of the 5-protecting group has minimal effect on the steric course of glycosylation. 相似文献
997.
M. G. Fan Y. C. Liang Y. F. Ming J. X. Chen T. Ye Q. Y. Zhang B. A. Xu S. Jin 《Research on Chemical Intermediates》1998,24(9):961-971
Photophysical behavior of spiro[1,3,3-trimethylindolino-2,3′-naphtho[2,1-b]-1,4-oxazine] (SP1) and spiro[1,3,3,2′-tetramethylindolino-2,3′-naphtho[2,1-b]-1,4-oxazine] (SP2) were studied. The fluorescent species and their spectra of SP1 and SP2 in polar solvents (acetonitrile and methanol) and non-polar solvent (cyclohexane) were investigated. The fluorescence decay
in polar solvents was studied by picosecond time-correlated single photon counting. In most cases, fluorescence decay obeyed
triexponential decay kinetics. The major fluorescent species is an excited intermediate which has similar conformation as
its precursor (1
SP
*) formed after the bond cleavage between spirocarbon and oxygen in oxazine ring. The effects of molecular structure and solvent
polarity on fluorescence spectra and fluorescence decay lifetime were studied. 相似文献
998.
四核钴羰基簇合物Co4(CO)8(μ-CO)2(μ4-PSR)2的合成和晶体结构 总被引:1,自引:0,他引:1
The title compounds Co4(CO)8(μ-CO)2 (μ4-PSR) [R=-CH3, -C2H5, -C(CH3)3,-(CHa)4CH3] were synthesized by the reaction of Co2(CO)8 with RSPCl2. They were characterized by IR, 1HNMR, elemental analysis. The crystal and molecular structure of Co4(Co)8(μ-CO)2 (μ4-PSC2H5) has been determined by single crystal diffraction method. Crystal data: monoclinic, space group P21 /c, with a=8-445(3), 6=8.562(3), c= 17.125(6)Å, β=104.26 (3)' 9 V=1200.1Å3, Z=2, Dc=1.937gcm-3. Its molecular structure contains an octahedral Co4P2 skeleton which consists of a rectangular four cobalt atoms core and the Co4 core is capped above and below by two quadruply bridging PSR ligands. 相似文献
999.
1000.
Molecular dynamics simulations show that gold clusters with about 600-3000 atoms crystallize into a Mackay icosahedron upon cooling from the liquid. A detailed surface analysis shows that the facets on the surface of the Mackay icosahedral gold clusters soften but do not premelt below the bulk melting temperature. This softening is found to be due to the increasing mobility of vertex and edge atoms with temperature, which leads to inter-layer and intra-layer diffusion, and a shrinkage of the average facet size, so that the average shape of the cluster is nearly spherical at melting. 相似文献