共查询到20条相似文献,搜索用时 31 毫秒
1.
The distribution of Cu 2+ ions in ZrO 2 and sulfated ZrO 2 hydrogel phases was studied by EPR spectroscopy and voltammetry. The formation of the following three types of copper structures was observed: mononuclear Cu 2+ complexes ( A), magnetic associates ( B), and Cu 2+ compounds ( C) that gave no EPR signals under the conditions used in the spectroscopic measurements. The specific catalytic activity of various Cu 2+ compounds in the liquid-phase reaction of 2,3,5-trimethyl-1,4-hydroquinone oxidation was determined. The copper complexes C were found to exhibit the highest catalytic activity. 相似文献
2.
以一水合醋酸铜为铜源,以2,6-二(4''-吡啶基)-4-甲基苯胺(L)为桥联吡啶配体、间苯二甲酸(H 2IPA)为共配体分别合成了一维链状配位聚合物{[(Cu (OAc) 2) 2(L)]·3CH 3CN} n( 1,OAc -=CH 3CO 2-)和二维网状配位聚合物{[Cu (IPA)(L)(H 2O)] 2·H 2IPA·H 2O} n( 2)。通过二者的单晶结构分析可以看出,配合物 1中的铜原子位于[CuNO 4] 2簇中的四面体配位环境中心,配合物 2中的铜原子处于[CuNO 3]变形六面体配位环境的中心,不同的配位环境导致2个配合物具有差异化的光催化降解有机物的活性。通过以亚甲基蓝为底物的类Fenton光催化降解对比实验表明,含有Cu—N、Cu—O配位环境的配合物 1的催化效果优于具有相同四面体构型配位环境的HKUST-1,且配合物 1和 2催化性能的对比也证明了开放性单核铜配位中心的光催化降解活性优于簇合物中的铜配位中心。得益于配体的稳定和框架结构的存在,与相同条件下无配体约束的醋酸铜盐的催化性能相比,2个配合物均具有更高的催化活性和可循环利用特性。通过UV-Vis光谱计算了二者的带隙,光催化降解前后的粉末X射线衍射及电感耦合等离子质谱证明了配合物的稳定性。通过添加自由基捕捉剂苯醌、叔丁醇和三乙醇胺,证实了该催化过程为羟基自由基过程的类Fenton反应机理。 相似文献
3.
An efficient protocol for C–C coupling has been developed using three iodo-bridged copper(I) complexes as catalysts. Complexes [CuI(bpy)]2 (1), [CuI(phen)]2·DMF (2), and [CuI(Mephen)]2 (3) were successfully synthesized via solvothermal method (bpy = 2,2′-dipyridyl, phen = 1,10-phenanthroline, and Mephen = 2,9-dimethylphenanthroline). The self-coupling reaction of phenylboronic acid was selected as a model reaction to evaluate the catalytic property of the complexes. Moreover, this method tolerates various substituents on the arylboronic acids such as halogens, carbonyls, and nitro groups. It shows that the iodo-bridged Cu(I) center serves as the active site to activate molecular oxygen during the catalytic process. The result illustrates that these complexes were found to be excellent catalysts for self-coupling of arylboronic acids under mild conditions. 相似文献
4.
Abstract The potential of the continuous addition of reagent (CAR) technique, developed for reactions on the millisecond time scale, in fluorimetric reaction-rate methods, is evaluated. The approach was applied to the classical fast reaction involving the oxidation of thiamine to fluorescent thiochrome effected by potassium ferricyanide in basic solutions. Practical problems associated with this system were readily avoided by using the CAR technique. Several kinetic methods have been developed for the determination of thiamine; all are very sentitive (detection limit, 2. 5x10 ?9 M) compared to other fluorimetric equilibrium and reaction-rate methods and are suitable for routine analyses (sample throughput, 100 h ?1). 相似文献
5.
The mechanism of formation of alkene stereoisomers in the catalytic olefination reaction of carbonyl compounds was studied. 4-Chlorobenzaldehyde hydrazone 1 stereoselectively reacts with a number of F-, Cl-, Br-, and I-containing polyhaloalkanes in the presence of catalytic amounts of CuCl to give -substituted styrenes 2 with the more thermodynamically stable alkene isomer being the major product. A model for the formation of the stereoisomers of alkenes 2 in the olefination reaction is proposed. Stereoselectivity of the reaction is determined by elimination of copper(ii) halides from the lowest-lying conformers of organocopper intermediates II. According to quantum-chemical calculations, the elimination should involve the staggered conformations with antiperiplanar arrangement of C—Hal and C—Cu bonds and proceed by the E2 anti-elimination mechanism. The results of quantum-chemical calculations are in good agreement with the experimental E/ Z alkene isomer ratios. 相似文献
6.
The biological dye, naphthol blue black B (NBBB) was found to produce a sensitive reaction with copper(II) at pH over 7. This
reaction was very interesting. The complexation of Cu(II) with NBBB happened at pH between 6 and 11 but the redox catalytic
reaction happened at pH over 11, where copper(II) served as a catalyst. In this study, ordinary spectrophotometry was limited
for use because of the serious interference of excess reactant. A new method, Β-correction principle, was applied because
it can eliminate the above interference. This method can give the simple determination of properties of Cu-NBBB complex solution
at pH 9.5, which involved the complex ratio, real molar absorptivity, and stability constant (K). Results showed that the
formed Cu-NBBB complex occurred as Cu(NBBB) at pH 9.5, its real rather than apparent absorptivity was equal to 7.62 x 10 3 L mol -1 cm -1 at 630 nm, and its stability constant was 1.32 x 10 6. The redox catalytic reaction between Cu(II) and NBBB at pH 13 was used to determine trace amounts of copper in water. This
reaction was very sensitive and highly selective. Most of the metals did not interfere with the direct determination of copper.
The detection limit of copper was 0.002 mg/L, and the recovery was between 90 and 104% with the relative standard deviation
of less than 11%.
This article was submitted by the author in English. 相似文献
7.
Abstract This method is based on the catalytic effect of copper(II) on the redox reaction between acid chrome dark blue and ascorbic acid in acetic acid-sodium acetate buffer solution and 1,10-phenanthroline as an activator. Acid chrome dark blue exhibits a sensitive polarographic wave at -0.375V Vs. SCE and change of acid chrome dark blue concentration is traced by a polarographic detection technique. The detection limit and the linear range of copper(II) are 2.34ng/ml and 5 to 50ng/ml respectively. This new catalytic method has been applied to the determination of copper in human hair, with satisfactory results. 相似文献
8.
The crystal structure, spectroscopic properties and catalytic property of the copper(II) complex, prepared by the reaction between copper(II) diacetate with the bidentate Schiff base, SalAHE (SalAHE = salicylaldehydeimine-1-hydroxyethane), are reported. This complex is able to oxidize 3,5-di- tert-butylcatechol to the respective o-quinone. The oxidation reaction was studied in CH 3CN with molecular oxygen at 0, 5, 15 and 25 °C. The progress of the catalytic reaction was followed by gas chromatographic analyses (GC). 相似文献
9.
Abstract A new method has been developed for field screening of copper (II) in water samples, which is based on an enzyme inhibition reaction between copper (II) and nitrate reductase. The concentration of copper (II) was acquired by indirect determination the reaction product (nitrite) with a mini optical reflection sensor. Under the optimum conditions, the calibration graph was linear in the range of 5.0–50 ng mL ?1. The limit of detection was 0.5 ng mL ?1. This method has been used for the field screening of copper (II) with satisfactory results. 相似文献
10.
ABSTRACTA novel, green and cost-effective heterogeneous nanocatalyst was synthesized by supporting copper (I) oxide nanoparticles on magnetic agar (Cu 2O/Agar@Fe 3O 4). Then, it was characterized with multiple techniques, such as scanning electron microscopy and transmission electron microscopy images, energy-dispersive X-ray analysis, Fourier-transform infrared (FT–IR) spectroscopy, thermogravimetric (TG) analysis, X-ray diffraction pattern, vibrating sample magnetometer curve, and inductively coupled plasma analysis. The catalytic activity of the newly designed catalyst was investigated in a one-pot three-component reaction of alkyl halides, sodium azide, and alkynes to obtain 1,4–disubstituted 1,2,3–triazoles in high yields in water–ethanol media. The present catalyst was simply separated from the reaction media by an external magnet and reused at least five subsequent runs without significant activity loss. 相似文献
11.
Aerobic epoxidation of olefins at a mild reaction temperature has been carried out by using nanomorphology of [Cu 3(BTC) 2] (BTC=1,3,5‐benzenetricarboxylate) as a high‐performance catalyst through a simple synthetic strategy. An aromatic carboxylate ligand was employed to furnish a heterogeneous copper catalyst and also serves as the ligand for enhanced catalytic activities in the catalytic reaction. The utilization of a copper metal–organic framework catalyst was further extended to the aerobic oxidation of aromatic alcohols. The shape and size selectivity of the catalyst in olefin epoxidation and alcohol oxidation was investigated. Furthermore, the as‐synthesized copper catalyst can be easily recovered and reused several times without leaching of active species or significant loss of activity. 相似文献
12.
An enantioselective Henry reaction was efficiently carried out under mild reaction conditions in the presence of catalytic 9- epi and natural Cinchona alkaloids and copper (II) acetate. The best catalytic performance was observed for native quinine (12 mol %) and Cu(OAc) 2 (10 mol %). Aromatic and aliphatic aldehydes with nitromethane and its α-substituted derivatives provided the corresponding β-nitroalcohols in good to reasonable yields, high syn-diastereoselectivity, and ( S)-enantioselectivity of up to 94% ee. 相似文献
13.
通过间苯二甲醛与5-氟苯基二吡咯甲烷反应合成了一种新的间位苯基桥联的双咔咯1,并利用锰盐与自由咔咯反应制备了其锰的金属配合物2。采用紫外、质谱、核磁、XPS等手段对化合物进行了表征。以苯乙烯为底物考察了锰双咔咯2的催化氧化性质,探讨了时间、溶剂、氧源、轴向配体对催化反应的影响。结果表明以亚碘酰苯和间氯过氧苯甲酸为氧源时催化的主要产物为环氧苯乙烷,而以双氧水和叔丁基过氧化氢为氧源时则主要产物为苯甲醛;在极性溶剂中的催化氧化产率较高。轴向配体对催化氧化有促进作用,不同轴向配体对催化反应产率提高的顺序是:1-甲基咪唑吡啶咪唑。 相似文献
14.
In this study, amidoxime-functionalized silica decorated with copper (AFS-Cu) was fabricated and tested for its catalytic application. Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction were employed to characterize its structure and morphology. The application of AFS-Cu as a catalyst for the catalytic reduction of methylene blue (MB) in aqueous media using NaBH 4 as reductant was evaluated. The ability to reuse as well as the effect of catalyst dose and pH of solution on the catalytic activity was investigated. The reduction of MB followed pseudo-first-order kinetics and the rate constant (k) was 0.6224 min -1. AFS-Cu was found to be a highly effective catalyst for MB reduction reaction and can be easily recovered and reused several times with no appreciable loss of catalytic activity. 相似文献
15.
A molecular approach to metal‐containing ceramics and their application as selective heterogeneous oxidation catalysts is presented. The aminopyridinato copper complex [Cu 2(Ap TMS) 2] (Ap TMSH=(4‐methylpyridin‐2‐yl)trimethylsilanylamine) reacts with poly(organosilazanes) via aminopyridine elimination, as shown for the commercially available ceramic precursor HTT 1800. The reaction was studied by 1H and 13C NMR spectroscopy. The liberation of the free, protonated ligand Ap TMSH is indicative of the copper polycarbosilazane binding. Crosslinking of the copper‐modified poly(organosilazane) and subsequent pyrolysis lead to the copper‐containing ceramics. The copper is reduced to copper metal during the pyrolysis step up to 1000 °C, as observed by solid‐state 65Cu NMR spectroscopy, SEM images, and energy‐dispersive spectroscopy (EDS). Powder diffraction experiments verified the presence of crystalline copper. All Cu@SiCN ceramics show catalytic activity towards the oxidation of cycloalkanes using air as oxidant. The selectivity of the reaction increases with increasing copper content. The catalysts are recyclable. This study proves the feasibility of this molecular approach to metal‐containing SiCN precursor ceramics by using silylaminopyridinato complexes. Furthermore, the catalytic results confirm the applicability of this new class of metal‐containing ceramics as catalysts. 相似文献
16.
The oxidative degradation of isotactic polypropylene films coated on well-defined Cu(Cu 2O), CuO 0.67, and CuO films in a temperature range of 90–120°C in a quartz-spoon-gauge-reaction vessel was studied. This catalytic reaction has been compared with the oxidation of polypropylene without copper or oxide films. The reaction vessel contained, if needed, P 2O 5 and/or KOH as “getters” for H 2O and CO 2, these substances could be menitored continuously. Cu(Cu 2O) films were transformed during oxidation of the polymer to yellow CuO 0.67 below 100°C and above this temperature to black CuO in the presence of H 2O and CO 2, whereas in the absence of these compounds CuO was formed below 100°C and CuO 0.67 at 120°C. Characteristic autoxidation curves obtained in the absence of H 2O and CO 2 showed induction periods that were shorter for copper oxide-polymer interfaces than for glass-polymer interfaces (i.e., for uncatalyzed oxidation). Abnormalities were observed for Cu(Cu 2O)-polymer interfaces because of further oxidation of Cu during the reaction. The rates of oxygen consumption were faster for CuO 0.67-polymer and CuO-polymer than for the uncatalyzed reaction; the catalytic action of CuO 0.67 was somewhat larger than that of CuO. The important observation was made that the mechanism of oxidation is not the same in the absence and presence of reaction products; that is, H 2O and CO 2. This was confirmed by ion beam scattering experiments, which also revealed that an oxidation-reduction process takes place at Cu and their oxide interfaces. A mechanism for the catalytic oxidation process, based on the ease by which copper ions are released from the metal oxides at the interface, was formulated. These ions diffuse subsequently as actions of carboxylate anions into the bulk of the polymer. Arrhenius equations of oxygen consumption are given for all cases; the energy of activation calculated for the initiation of the uncatalyzed oxidation agrees with its literature value. The energy of activation for the initiation of the catalyzed reaction was a few kilocalories lower than that for the uncatalyzed reaction. Catalytic action is mainly operative for the initiation reaction at the interface and for the decomposition of hydroperoxides by copper ions. Preventing the delivery of copper ions to the polymer would be the most efficient way of inhibiting the catalysis. 相似文献
17.
通过间苯二甲醛与5-氟苯基二吡咯甲烷反应合成了一种新的间位苯基桥联的双咔咯 1,并利用锰盐与自由咔咯反应制备了其锰的金属配合物 2。采用紫外、质谱、核磁、XPS等手段对化合物进行了表征。以苯乙烯为底物考察了锰双咔咯 2的催化氧化性质,探讨了时间、溶剂、氧源、轴向配体对催化反应的影响。结果表明以亚碘酰苯和间氯过氧苯甲酸为氧源时催化的主要产物为环氧苯乙烷,而以双氧水和叔丁基过氧化氢为氧源时则主要产物为苯甲醛;在极性溶剂中的催化氧化产率较高。轴向配体对催化氧化有促进作用,不同轴向配体对催化反应产率提高的顺序是:1-甲基咪唑 >吡啶 >咪唑。 相似文献
18.
A catalytic procedure has been developed for the synthesis of 15-pentadecanolide ( 1) from readily available 1-hydroperoxy-16-oxabicyclo[10.4.0]hexadecane ( 2). The method is based on the reaction of hydroperoxide 2 with copper acetate (0.15–5 mol.%). Ring expansion occurred as a result of generation of tertiary bicyclohexadecyloxyl radicals 4 from hydroperoxide 2 under the action of Cu 1 ions, β-scission of the radicals accompanied by regioselective cleavage of the bridge bond to form macrocyclic C-centered
radicals 5, and their oxidation by Cu 11 ions to ( E)-11- and ( E)-12-pentadecen-15-olides ( 6). The products obtained were converted into 15-pentadecanolide by subsequent catalytic hydrogenation over a Pd catalyst in
a yield of more than 90% with respect to hydroperoxide 2.
Translated from Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1197–1200, June, 1998. 相似文献
19.
AbstractA novel red copper(II) compound, bis(μ-bromo)bis(2-(benzothiazol-2-yl-hydrazono)-1,2-diphenyl-ethanone)-dicopper(II) ( 1), has been fostered by equimolar reaction of a Schiff-base ligand, 2-(benzothiazol-2-yl-hydrazono)-1,2-diphenyl-ethanone (LH), with copper(II) bromide in satisfactory yield. 1 has thoroughly been characterized by C, H and N elemental analyses, FT-IR and UV-vis (both in solid state and in solution) spectroscopies, and room-temperature magnetic susceptibility and conductivity measurements. Dimeric 1 bears symmetric rare bromo-bridges in its crystal structure. 1 retains its solid-state identity even in a protic solvent like methanol. 1 in methanol displays two-step one-electron redox response. Theoretical calculations based on DFT were executed to probe the electronic structure of 1 and to augment its color. DNA- and RNA-binding aspects of both LH and 1 have been explored. Thermodynamic binding parameters have been determined. LH is a major-groove binder to DNA, while 1 manifests itself as a minor-groove binder. This binding has been corroborated through molecular docking. Nucleic acid binding aspect of such type of rare bromo-bridged red copper(II) dimer is unprecedented. 相似文献
20.
A safe, efficient, and improved procedure for the regioselective synthesis of 1‐(2‐hydroxyethyl)‐1 H‐1,2,3‐triazole derivatives under ambient conditions is described. Terminal alkynes reacted with oxiranes and NaN 3 in the presence of a copper(I) catalyst, which is prepared by in situ reduction of the copper(II) complex 4 with ascorbic acid, in H 2O. The regioselective reactions exclusively gave the corresponding 1,4‐disubstituted 1 H‐1,2,3‐triazoles in good to excellent yields. This procedure avoids the handling of organic azides as they are generated in situ, making this already powerful click process even more user‐friendly and safe. The remarkable features of this protocol are high yields, very short reaction times, a cleaner reaction profile in an environmentally benign solvent (H 2O), its straightforwardness, and the use of nontoxic catalysts. Furthermore, the catalyst could be recovered and recycled by simple filtration of the reaction mixture and reused for ten consecutive trials without significant loss of catalytic activity. No metal‐complex leaching was observed after the consecutive catalytic reactions. 相似文献
|