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801.
802.
4,4′‐Bipyridyl N,N′‐dioxide crystallizes with 3‐hydr­oxy‐2‐naphthoic acid to give a centrosymmetric three‐component adduct, C10H8N2O2·2C11H8O3, which is engineered into a two‐dimensional layer structure by two kinds of π–π inter­actions. Weak C—H⋯O inter­actions further link the two‐dimensional structure into a three‐dimensional structure.  相似文献   
803.
804.
The continuous photoreduction of methyl viologen by 5,5″-bis(aminomethyl)-2,2′:5′,2″-terthiophene (AT) and 2,2′:5′,2″-terthiophene-5,5″-dicarboxylic acid (CT), using EDTA as a sacrificial electron donor, has been investigated in aqueous solution at various pH. Apparent rates and efficiencies of production of the methyl viologen radical cation (MV+) were found to be dependent on the pH, the concentrations of all three components and the intensity of the incident light. The highest conversion efficiency (77%) was shown by the bis(aminoniethyI (-substituted terthiophene AT at pH 7.7. The quantum yield for the formation of MV+ under these conditions was 0.24, which is comparable with other common systems  相似文献   
805.
Jong-Ho Kim 《Tetrahedron letters》2004,45(30):5827-5831
A poly(imidazoliummethyl styrene)-surface grafted-polystyrene resin was prepared by suspension polymerization. This was used as the polymer-supported carbene precursor for the palladium complex, which efficiently catalyzed the Suzuki cross-coupling of aryl halides and phenylboronic acid.  相似文献   
806.
Calculation methods based on hybrid Density Functional Theory (DFT) with the basis sets of the B3LYP/6‐31+G(d)//B3LYP/4‐31G(d) method and the differential overlap (INDO) program were used to derive reasonable decomposition mechanisms of 1,4,5,8‐tetranitro‐1,4,5,8‐tetraazadecalin (TNAD) and 1,3,3‐trinitroazetidine (TNAZ) explosives. All possible decomposition species and transition states, including intermediates and products, were identified and their corresponding enthalpy of formation and Gibbs free energy of formation were obtained using polyparametric modification equations. INDO bond energy calculation results reveal the weakest bonding site for reference and determine where cleavage can occur easily. This work is concerned mainly with eliminating HONO (cis or trans form). The activation energy for trans‐form HONO elimination is lower than that of cis‐form HONO elimination in the initial steps of both TNAD and TNAZ decomposition, being 18.5 kJ/mol and 33.3 kJ/mol, respectively. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005  相似文献   
807.
The cerium‐containing MCM‐41 (Ce‐MCM‐41) has been synthesized by direct hydrothermal method. The low‐angle XRD patterns revealed the typical five major peaks of MCM‐41 type hexagonal structures. The interplanar spacing d100 = 38.4 Å was obtained that can be indexed on a hexagonal unit cell parameter with ao = 44.3 Å which was larger than that of pure siliceous MCM‐41 (Si‐MCM‐41). Transmission electron micrograph shows the regular hexagonal array of uniform channel characteristics of MCM‐41. The BET surface area of Ce‐MCM‐41 was 840 m2/g, which is much reduced as compared to that of Si‐MCM‐41, with the pore size of 26.9 Å and mesopore volume of 0.78 cm3/g were measured by nitrogen adsorption‐desorption isotherm at 77 K. Along with the results, the synthesized Ce‐MCM‐41 exhibited a well‐ordered MCM‐41‐type mesoporous structure with the incorporation of cerium. Using Ce‐MCM‐41 as a support, the Rh (0.5 wt%) catalyst exhibited very high activity for the NO/CO reactions.  相似文献   
808.
Three new phenyl glycosides, scrophenoside A ( 1 ), B ( 2 ), and C ( 3 ), and two new phenylethyl glycosides, scroside D ( 4 ) and scroside E ( 5 ), were isolated from the stem of Picrorhiza scrophulariiflora Pennell (Scrophularlaceae), besides five known compounds. On the basis of spectroscopic evidence, the structures of the new compounds were elucidated as 4‐acetyl‐2‐methoxyphenyl 6‐O‐[4‐(β‐D ‐glucopyranosyloxy)vanilloyl]‐β‐D ‐glucopyranoside ( 1 ), 4‐acetylphenyl 6‐O‐[(E)‐p‐coumaroyl]‐β‐D ‐glucopyranoside ( 2 ), 4‐[(1R)‐ and (1S)‐1‐hydroxyethyl]‐2‐methoxyphenyl β‐D ‐glucopyranoside ( 3a and 3b , resp.), 2‐(3,4‐dihydroxyphenyl)ethyl Oβ‐D ‐glucopyranosyl‐(1→3)‐4‐O‐[(E)‐feruloyl]‐β‐D ‐glucopyranoside ( 4 ), and 2‐(3,4‐dihydroxyphenyl)ethyl Oβ‐D ‐glucopyranosyl‐(1→3)‐6‐O‐[(E)‐feruloyl]‐β‐D ‐glucopyranoside ( 5 ).  相似文献   
809.
Five new polycyclic Daphniphyllum alkaloids, macropodumines F ( 1 ) and G ( 2 ), 17‐oxoyuzurimine ( 3 ), and macropodumines H ( 4 ) and I ( 5 ), were isolated from the leaves of D. macropodum Miq ., collected in Sichuan Province, China. The structures and relative configurations of the new compounds – as well as of four known, related alkaloids – were elucidated on the basis of in‐depth spectroscopic and mass‐spectrometric analyses, by chemical derivatization, and by comparison of spectroscopic data with those of known compounds.  相似文献   
810.
刘耀虎  刘鸣华 《中国化学》2002,20(6):601-605
IntroductionReversiblecolorchangesuponexternalorinternalstimulationshavebeenattractingmuchattentionduetotheirutilityasfunctionalmaterials .Forexample ,pho tochromismdescribesthecolorchangesinducedbypho toirradiationandcanbeusedasphoto recordingmateri als…  相似文献   
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