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101.
Staiger CL Loy DA Jamison GM Schneider DA Cornelius CJ 《Journal of the American Chemical Society》2003,125(33):9920-9921
A spectrophotometric based, parallel approach to screen heterogeneous catalysts for hydrodesulfurization has been developed. The method utilizes optical changes resulting from the hydrodesulfurization of 1,1'-binaphthothiophene to 1,1'-binaphthyl to determine catalyst activity. Hydrodesulfurization of 1,1'-binaphthothiophene to 1,1'-binaphthyl results in a loss of conjugation in the binaphthyl ring system. This results in a blue shift of more than 60 nm in the UV-vis spectrum. Since only small amounts of the HDS catalyst and 1,1'-binaphthothiophene are required, a large number of catalysts may be screened simultaneously. The synthesis of the 1,1'-binaphthothiophene and conditions for HDS catalyst screening are described. 相似文献
102.
P. Duane Walker Gustavo A. Arteca Paul G. Mezey 《Journal of computational chemistry》1993,14(10):1172-1183
An algorithm for a detailed 3-D characterization of the shapes of molecular charge distributions is implemented in the form of a comprehensive package of computer programs, GSHAPE, and applied to a series of 10-electron hydrides to critically evaluate the methodology. Attention is paid to the effects of nuclear geometry and the size of basis on the molecular shape. The characterization is performed by computing a number of topological invariants (“shape groups”) associated with a continuum of molecular surfaces: the complete family of all electronic isodensity contours for the given molecules. These shape groups (the homology groups of truncated surfaces derived from isodensity contours) depend on two continuous parameters: a density value defining the density contour and a reference curvature value, to which the local curvatures of the isodensity contours are compared. The electronic charge distribution is calculated at the ab initio level using basis sets ranging from STO-3G to 6-31G**. No visual inspection is required for the characterization and comparison of shapes of molecular charge densities, as these are done algorithmically by the computer. However, visualization of the results is one option of our program using Application Visualization Software (AVS). For a given molecule, in a given nuclear geometry, the technique provides a 2-D shape map, displaying the distribution of the shape gruops as a function of the local curvature and the level set value (the value of the charge density at the contour). The computer program GSHAPE performs the analysis automatically. This feature makes it potentially useful in the context of computer-aided drug design, where unbiased, automated shape characterization methods are valuable tools. As examples, a variety of 2-D shape maps are discussed. © John Wiley & Sons, Inc. 相似文献
103.
Striplin DR Reece SY McCafferty DG Wall CG Friesen DA Erickson BW Meyer TJ 《Journal of the American Chemical Society》2004,126(16):5282-5291
The helical oligoproline assembly CH3-CO-Pro-Pro-Pro-Pra(Ptzpn)-Pro-Pro-Pra(RuIIb2m2+ -Pro-Pro-Pra(Anq)-Pro-Pro-Pro-NH2, having a spatially ordered array of functional sites protruding from the proline backbone, has been prepared. The 13-residue assembly formed a linear array containing a phenothiazine electron donor, a tris(bipyridine)ruthenium(II) chromophore, and an anthraquinone electron acceptor with the proline II secondary structure as shown by circular dichroism measurements. Following RuII --> b2m metal-to-ligand charge-transfer (MLCT) excitation at 457 nm, electron-transfer quenching occurs, ultimately to give a redox-separated (RS) state containing a phenothiazine (PTZ) radical cation at the Pra(Ptzpn) site and an anthraquinone (ANQ) radical anion at the Pra(Anq) site. The redox-separated state was formed with 33-96% efficiency depending on the solvent, and the transient stored energy varied from -1.46 to -1.71 eV at 22 +/- 2 degrees C. The dominant quenching mechanism is PTZ reductive quenching of the initial RuIII(b2m*-) MLCT excited state which is followed by m*- --> ANQ electron transfer to give the RS state. Back electron transfer is highly exergonic and occurs in the inverted region. The rate constant for back electron transfer is solvent dependent and varies from 5.2 x 10(6) to 7.7 x 10(6) s-1 at 22 +/- 2 degrees C. It is concluded that back electron transfer occurs by direct ANQ*- --> PTZ*+ electron transfer. Based on independently evaluated kinetic parameters, the electron-transfer matrix element is HDA approximately 0.13 cm-1. 相似文献
104.
Two numerical codes, a complex face vector F and a real face vector D are developed for the characterization of square-cell configurations (lattice animals), used for representing the shapes of molecular monolayers and cross sections of molecular surfaces. The real face vector D represents all the intrinsic properties, size, and shape of the lattice animal. The complex face vector F contains complete information about the size, the shape, and also the placement of the particular lattice animal with respect to the lattice. Based on the properties of the face vectors, a method is developed for the classification of similar animals into equivalence classes. The face vector method is proposed for an algorithmic, nonvisual computer analysis of similarity of shapes of molecular monolayers and planar domains of cross sections of molecular surfaces, approximated by lattice animals. 相似文献
105.
Alfonso Castieiras Duane Choquesillo‐Lazarte Josefa María Gonzlez‐Prez Rosa Carballo Juan Nicls‐Gutirrez 《无机化学与普通化学杂志》2006,632(5):845-850
The compounds [Cu(pmda)(crea)]·H2O ( 1 ), [Zn(pmda)(crea)]·H2O ( 2 ) and [Co(pmda)(crea)(H2O)]·H2O ( 3 ) were prepared and characterized by thermal, spectral and X‐ray diffraction methods. In compounds 1 and 2 the MII coordination is of type 4+1 and approaches to a trigonal bipyramid (71.85 and 86.18 %, respectively) with rather linear N(pmda)‐MII‐N(crea) trans‐apical angles, but with different longest coordination bond (Cu‐O(pmda) or Zn‐N(apliphatic, pmda), respectively). Both compounds are isotypic and one intra‐molecular interligand N‐H···O interaction reinforces the molecular recogniton crea‐MII(pmda) chelate. In contrast, the compound 3 exhibits an octahedral coordination, imposed by the 3d7 electronic configuration of the cobalt(II) atom, and the crea‐chelate recognition involves the Co‐N(crea) coordination bond and one intramolecular ‘bifurcated’ H‐bonding interaction between one N‐H(crea) bond and one O(pmda) plus the O(aqua) atoms as ‘acceptors’. 相似文献
106.
Regina Fernández‐Piñar Celia Sánchez de Medina‐Revilla Alicia Domínguez‐Martín María Pilar Brandi‐Blanco Duane Choquesillo‐Lazarte Josefa María González‐Pérez Juan Niclós‐Gutiérrez Prof. 《无机化学与普通化学杂志》2007,633(15):2658-2666
N,N‐bis(carboxymethyl)‐1‐adamantylamine acid (H2BCAA) or N‐(1‐adamantyl)‐iminodiacetic acid forms zwitterions that are intra‐stabilized by a ‘bifurcated’ N+‐H···O(carboxyl)2 interaction. In the crystal, both half‐protonated carboxyl groups of H2BCAA± are involved in linear O‐H···O inter‐molecular bridges of 2.46Å. In the studied BCAA‐CuII derivatives, the iminodiacetate‐moiety of the BCAA chelating ligand exhibits a mer‐NO2 conformation in [Cu(BCAA)(H2O)2] ( 1 ) and [Cu(BCAA)(Him)]2 ( 2 ), but a fac‐O2+N(apical) conformation in [Cu(BCAA)(bpy)(H2O)]·3.5H2O ( 3 ) [Him = imidazole, bpy =2,2′‐bipyridine]. In clear contrast, dipyridylamine (dpya), as auxiliary ligand, seems to be unable to promote the fac‐O2+N(apical) conformation in BCAA, as reveal the structures of two new salts with the trinuclear cation [(dpya)2Cu‐μ2‐Cu(BCAA)2‐Cu(dpya)2]2+ and the anions [Cu(BCAA)2]2? ( 4 ) or NO3? ( 5 ), respectively. 相似文献
107.
Elizabeth A. Babaian Laura M. Barden Duane C. Hrncir William E. Hunter Jerry L. Atwood 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(5):605-610
The synthesis of the first liquid clathrate derived from an indium precursor is described. The aromatic/anion ratio of the inclusion complex prepared using benzene is 12.4. The use of toluene results in the inclusion of 10.3 guest toluene molecules/anion. The crystal structure of the parent complex, [K·18-Crown-6]2[InClI2(CH3)][InClI(CH3)2] was carried out. The compound belongs to the monoclinic space groupP21/c, witha=19.508(9),b=8.503(5), andc=29.437(9) Å, =96.55(3)°, andD
calc=1.83 g cm–3 forZ=4. Least-squares refinement based on 3449 observed reflections led to a finalR=0.099. The structure displays two different environments for the two K+ cations in the asymmetric unit. One adopts the near-planar [K·18-crown-6]+ configuration while the other K+ resides 0.81 Å above the second 18-crown-6 plane. The latter K+ is apparently pulled out of the crown by a strong interaction with a Cl– ion.
Supplementary Data related to this article are deposited with the British Library as Supplementary Publication No. SUP 82046 (25 pages). 相似文献
108.
Graves Duane A. Lang Craig A. Leavitt Maureen E. 《Applied biochemistry and biotechnology》1991,(1):813-826
Client-funded bench-scale investigations concerning the likelihood of successfully applying biological remediation to hazardous
wastes must be cost-effective, and they usually need only determine if biodegradation is likely to occur on site. To assess
the potential for stimulating biodegradation, biochemical oxygen demand (BOD) was used to continuously monitor bacterial respiration
during growth on mixed organic wastes from contaminated water and soil. Continuously collected oxygen-consumption data provided
information on the overall metabolic activity of the resident bacterial population and permitted direct observation of the
cessation of microbial respiratory activity and, thus, the termination of aerobic degradation. The correlation of biological
oxygen utilization with biodegradation was confirmed using independent analytical methods. Continuous, long-term BOD analysis
was applied to bench-scale studies to assess the biodegradation of mixed organic wastes from contaminated sites and industrial
waste effluents. This information was used to make an initial determination regarding the need to further explore bioremediation
as a potential remedial-action technology using on-site, pilot-scale testing. 相似文献
109.
Brewer Christopher M. Bujalski Duane R. Parent Virginia E. Su Kai Zank Gregg A. 《Journal of Sol-Gel Science and Technology》1999,14(1):49-68
We have undertaken a systematic study of the oxidation chemistry for a range of SiOC ceramics derived from silsesquioxane polymeric precursors. This study examines the oxidation for 500 hours at 600, 800, 1000 and 1200°C for four SiOC powders. The material changes upon oxidation were characterized qualitatively by color change and optical microscopy and quantitatively by weight and composition change. In this study we employ a very easy method that uses the weight change upon oxidation and a carbon analysis after oxidation to arrive at the composition of the oxidized SiOC. Combined these qualitative and quantitative techniques have shown that on oxidation at 800 and 600°C the SiOC composition is more rapidly changed to that of silica than oxidation over the same time frame at 1000 or 1200°C. The data indicates that this difference is due to the relative rates of oxidation of the excess carbon versus the Si—C bonds in the SiOC. At lower temperatures initially the carbon oxidation predominates which leads to higher porosity throughout the material and an increase in the surface area with eventually complete oxidation to silica. At higher temperatures the Si—C bond oxidation rate is comparable to the rate of oxidation of carbon. This allows a silica-like surface to build up on the SiOC, which slows all subsequent reactions due to the necessity to diffuse O2 in and COx out of the bulk. Under these oxidation conditions materials that originally contain high amounts of excess carbon are more quickly oxidized to silica than those that contain minimal amounts of excess carbon, as confirmed by elemental analysis and optical microscopy. Regardless of the time or temperature of the oxidation conditions no materials were found to be completely stable to oxidation. SiOC materials with low levels of excess carbon showed the best resistance to change upon oxidation. 相似文献
110.
Herrera JM Colacio E Mathonière C Choquesillo-Lazarte D Ward MD 《Chemical communications (Cambridge, England)》2008,(37):4460-4462
Reaction of the anionic cyanometallate chromophore [{Ru(CN)4}3(micro3-HAT)]6- with [MII(tren)]2+ complexes (M=ZnII, CuII) provides discrete tetradecanuclear clusters of formula [{MII(tren)(micro-CN)}11{Ru3(HAT)(CN)}]16+; the weak luminescence of the Ru3 chromophore is substantially enhanced in the presence of ZnII ions, whereas it is completely quenched when CuII centers are present. 相似文献