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Ekaterina Zhecheva Radostina Stoyanova Sonya Ivanova Velin Nikolov 《Solid State Sciences》2010,12(12):2010-2014
Nanosized aluminum tungstate, Al2(WO4)3, is prepared by a precipitation reaction between Na2WO4 and Al(NO3)3. The structure of the precipitated composition is determined by powder XRD analysis, IR and 27Al MAS NMR spectroscopy. The thermal properties are examined by DSC, DTA and TG analyses combined with gas evolved analysis. Particle sizes and morphology are examined by TEM analysis. Precipitation reaction leads to the formation of an amorphous composition, which consists of dimer and trimer aluminum hydroxide species and WO42? groups. Finely dispersed particles with dimensions of about 25 nm are formed. The precipitated composition is decomposed to amorphous Al2(WO4)3 immediately after H2O release. At 630 °C, amorphous Al2(WO4)3 crystallizes in an orthorhombic modification of Al2(WO4)3, the enthalpy of crystallization being 58 kJ/mol. The nanosized particles remain intact after the crystallization of amorphous Al2(WO4)3. A significant particle growth take places when nanosized Al2(WO4)3 is heated from 600 to 800 °C. 相似文献
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Stulz E Scott SM Bond AD Teat SJ Sanders JK 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(24):6039-6048
Mixed metallo-porphyrin cages were selected and amplified from dynamic combinatorial libraries (DCLs) by using appropriate templates. The cages are composed of two bisphosphine substituted zinc(II) porphyrins as ligand donors and two rhodium(III) or ruthenium(II) porphyrins as ligand acceptors, and are connected through metal-phosphorus coordination. Ru and Rh porphyrins that display a large structural diversity were employed. The templating was achieved by using 4,4'-bpy, 3,3'-dimethyl-4,4'-bipyridine and benzo[lmn]-3,8-phenanthroline, and acts through zinc-nitrogen coordination. The absolute amount of amplification from the DCLs is strongly dependent on the combination of the Ru/Rh porphyrin and the template; cages with sterically demanding porphyrins can only form with smaller templates. In the case of tert-butyl-substituted TPP (TPP=tetraphenylporphyrin), cages are not formed at all. The formation of the cages is usually complete within 24 h at an ambient temperature; in the case of the cage containing Rh(III)OEP (OEP=octaethylporphyrin) and bpy, the pseudo-first-order rate constant of cage formation was determined to be 2.1+/-0.1x10(-4) s(-1) (CDCl(3), 25 degrees C). Alternatively, heating the mixtures to 65 degrees C and cooling to room temperature yields the cages within minutes. The (1)H NMR chemical shifts of several characteristic protons show large differences upon changing the identity of the Ru/Rh porphyrin and the central metal; this is most likely to arise from variations in the geometry of the cages. The X-ray crystal structure of a cage, which contains Rh(III)OEP as a porphyrin acceptor and bpy as template, demonstrates that the cages can adopt severely distorted conformations to accommodate the relatively short templates. An extension to mixed DCLs showed that only limited selectivity is displayed by the various templates. Formation of mixed cages that contain two different rhodium porphyrins prevents effective selection, although the kinetic lability of the systems allows for some amplification. This lability, however, also prevents isolation of the individual cages. Removal of the template leads to re-equilibration, thus the templates act as scaffolds to keep the structures intact. 相似文献
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Metal-catalyzed coupling methodologies have been employed in the synthesis of the key building block 3'-formyl-2,2':5',2"-terthiophene. Wittig olefinations with this aldehyde have produced five novel beta-styryl-substituted terthiophene monomers. These materials have been fully characterized by NMR spectroscopy, microanalysis, mass spectrometry, and X-ray crystal structure analysis. The results from the UV/visible spectroscopy and cyclic voltammetric investigations are reported. 相似文献
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Xiaolei Li Frank L. Dorman Paul A. Helm Sonya Kleywegt Andr Simpson Myrna J. Simpson Karl J. Jobst 《Molecules (Basel, Switzerland)》2021,26(22)
Gas chromatography–high-resolution mass spectrometry (GC–HRMS) is a powerful nontargeted screening technique that promises to accelerate the identification of environmental pollutants. Currently, most GC–HRMS instruments are equipped with electron ionization (EI), but atmospheric pressure ionization (API) ion sources have attracted renewed interest because: (i) collisional cooling at atmospheric pressure minimizes fragmentation, resulting in an increased yield of molecular ions for elemental composition determination and improved detection limits; (ii) a wide range of sophisticated tandem (ion mobility) mass spectrometers can be easily adapted for operation with GC–API; and (iii) the conditions of an atmospheric pressure ion source can promote structure diagnostic ion–molecule reactions that are otherwise difficult to perform using conventional GC–MS instrumentation. This literature review addresses the merits of GC–API for nontargeted screening while summarizing recent applications using various GC–API techniques. One perceived drawback of GC–API is the paucity of spectral libraries that can be used to guide structure elucidation. Herein, novel data acquisition, deconvolution and spectral prediction tools will be reviewed. With continued development, it is anticipated that API may eventually supplant EI as the de facto GC–MS ion source used to identify unknowns. 相似文献
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Uttamchandani M Walsh DP Khersonsky SM Huang X Yao SQ Chang YT 《Journal of combinatorial chemistry》2004,6(6):862-868
A novel and highly diverse tagged triazine library incorporating a triethylene glycol-based linker was synthesized using an orthogonal combinatorial approach on the solid phase and covalently immobilized on a glass substrate as a small molecule microarray (SMM). The SMM was screened with a fluorophore-conjugated human IgG, and 4 novel binders from a library of 2688 compounds were identified from the fully spatially addressable array without the need for compound decoding. Using surface plasmon resonance (SPR) analysis, binding seen on the array was confirmed, and a binding constant as low as Kd = 2.02 x10(-6) M was measured. 相似文献
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Facilitated forward chemical genetics using a tagged triazine library and zebrafish embryo screening
Khersonsky SM Jung DW Kang TW Walsh DP Moon HS Jo H Jacobson EM Shetty V Neubert TA Chang YT 《Journal of the American Chemical Society》2003,125(39):11804-11805
An improved forward chemical genetics approach was successfully demonstrated using a tagged library concept. A small-molecule triazine library with linkers was used to screen for brain/eye developmental phenotypes in a zebrafish embryo system. This approach enabled the rapid isolation of the target proteins by facile affinity matrix preparation and elucidated the first small-molecule inhibitors for several ribosomal accessory proteins or their complex as the target. 相似文献