Predictive Catalysis in Olefin Metathesis with Ru-based Catalysts with Annulated C60 Fullerenes in the N-heterocyclic Carbenes

Predictive catalysis must be the tool that does not replace experiments, but acts as a selective agent, so that synthetic strategies of maximum profitability are used in the laboratory in a surgical way. Here, nanotechnology has been used in olefin metathesis from homogeneous Ru-NHC catalysts, specifically annulating a C₆₀ fullerene to the NHC ligand. Based on results with the C₆₀ in the backbone, a sterile change with respect to the catalysis of the metal center, an attempt has been made to bring C₆₀ closer to the metal, by attaching it to one of the two C−N bonds of the imidazole group of the SIMes (1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) ligand (reference NHC ligand of the 2^nd generation Grubbs catalysts) to increase the steric pressure of C₆₀ in the first sphere of reactivity of the metal. The DFT calculated thermodynamics and the kinetics of SIMes-derived systems show that they are efficient catalysts for olefin metathesis.     

Electrocatalytic Activities of 1,2-Naphthoquinone Modified Carbon Nanotube to the Electrochemical Oxidation of β-Nicotinamide Adenine Dinucleotide

The carbon nanotube (CNT) was functionalized with the electroactive species of 1,2-naphthoquinone (Nq) by a method of adsorption to form Nq-CNT nanocomposite. The Nq-CNT was characterized by spectroscopic techniques, for example UV-Vis, FTIR, SEM, etc., and the results showed that Nq can rapidly and effectively be adsorbed on the surface of CNT with high stability. Moreover, it was shown that the dispersion ability of CNT in aqueous solution had a significant improvement after CNT functionalized with Nq. The Nq-CNT/GC electrode was fabricated by modifying Nq-CNT nanocomposite on the GC electrode surface and its electrochemical properties were investigated by voltammetry, which indicated that CNT could improve the electrochemical behavior of Nq and greatly enhance its redox peak currents. The Nq-CNT/GC electrode exhibited a pair of well-defined and nearly symmetrical redox peaks with the formal potential of –87.3 ± 4.5 mV (vs. SCE, 0.1 M PBS, pH 7.0), which was almost independent on the scan rates. The experimental results also demonstrated that Nq and CNT could synergistically catalyze the electrochemical oxidation of NADH, and Nq-CNT exhibited a high performance with lowering the overpotential by more than 510 mV. The presented method had some advantages, such as rapid and facile CNT functionalization, easy electrode fabrication, and high electrocatalytic activity, etc.     

The role of itaconic and fumaric acid in the emulsion copolymerization of methyl methacrylate and n-butyl acrylate

The effect of itaconic (IA) and fumaric (FA) acids, in the emulsion copolymerization of methyl methacrylate (MMA) with n-butyl acrylate (BA) is presented in this work. The effect of functional monomers on the overall conversion, on the colloidal properties of the latexes as well as on the distribution of the carboxylic groups (buried, particle surface and serum) was examined. The effect of the pH on the partitioning of IA and FA on the copolymerizations was also examined in order to better understand the role of these functional monomers. The carboxylic groups present in the cleaned latexes were analyzed using conductimetry and manual titration with a solution of sodium hydroxide in methanol. The results of these analyses showed that it was possible to determine the distribution profile of the carboxylic groups in the latexes (buried, particle surface and serum). It was demonstrated that IA and FA were distributed differently throughout the three phases of the emulsion, with these differences depending on the solubility of the corresponding monomer.     

On the compatibility of the IPP/PA6/EPDM blends with and without functionalized IPP I. Thermo-oxidative behaviour

Binary isotactic polypropylene (IPP)/polyamide 6 (PA6) and ternary IPP/PA6/ethylene–propylene diene terpolymer (EPDM) blends in various ratios were obtained in a Haake Rheocord mixer. Processing behaviour was changed in the presence of IPP functionalized with bismaleimide (BMI), maleic anhydride (MA) and acrylic acid (AA) as reactive compatibilizing agents. The thermal and thermo-oxidative behaviour of blends was studied by differential scanning calorimetry and thermogravimetry. The functionalized IPPs modify the crystallinity degree and the decomposition behaviour of both IPP and PA6 as a result of chemical reactions of functional groups with those of the PA6. The changes depend on the IPP/PA6 or IPP/PA6/EPDM ratio, the chemical nature and amount of the functionalized IPP. On the basis of the processing and thermal data one can conclude that the compatibilizing agent effect increases in the following order: IPP-AA 相似文献   

Simultaneous Determination of Dopamine and Ascorbic Acid at an In‐Site Functionalized Self‐Assembled Monolayer on Gold Electrode

The in‐site functionalization of 4‐aminothiophenol (4‐ATP) self‐assembled monolayer on gold electrode at physiological pH yields a redox active monolayer of 4′‐mercapto‐N‐phenylquinone diimine (MNPD). The functionalized electrode exhibits excellent electrocatalytic responses towards dopamine (DA) and ascorbic acid (AA), reducing the overpotentials by about 0.22 V and 0.34 V, respectively, with greatly enhanced current responses. Due to its different catalytic activities toward DA and AA, the modified electrode resolves the overlapping voltammetric responses of DA and AA into two well‐defined voltammetric peaks by differential pulse voltammetry (DPV), which can be used for the simultaneous determination of these species in a mixture. The catalytic peak current obtained from DPV was linearly related to DA and AA concentration in the ranges of 5.0×10^?6?1.25×10^?4 M and 8.0×10^?6?1.3×10^?4 M with correlation coefficient of 0.999 and 0.998, respectively. The detective limits (3σ) for DA and AA were found to be 1.2×10^?6 M and 2.4×10^?6 M, respectively. The modified electrode shows good sensitivity, selectivity and stability, and has been applied to the determination of DA and AA simultaneously in samples with satisfactory results.     

(R)-2,3-Cyclohexylideneglyceraldehyde, a novel template for stereoselective preparation of functionalized δ-lactones: synthesis of mosquito oviposition pheromone

(R)-2,3-Cyclohexylideneglyceraldehyde 1 has been used to prepare functionalized δ-lactones. This was exemplified by a simple and efficient synthesis of the oviposition pheromone 10 of Culex pipens fatigans.     

Preparation and Evaluation of Mono (6A-N-Ethylenediamine-6A-Deoxy)-Functionalized β-Cyclodextrin Bonded Stationary Phases for Normal and Reverse-Phase High-Performance Liquid Chromatography

The preparation, characterization and potential liquid chromatographic applications of two totally and partly functionalized -cyclodextrin-bonded stationary phases were presented. Separation of a series of organophosphorus racemic compounds was achieved under normal and reverse-phase conditions. Separation factor was up to 1.812 and resolution up to 4.072. The influence of chromatographic conditions was investigated and the possible chiral recognition mechanism was proposed.     

A versatile approach to the reproducible synthesis of functionalized polysiloxane stationary phases

Exploitation of the full potential of selector-modified polysiloxanes as chromatographic stationary phases is limited because conventional methods of silicone synthesis involve strong acids or strong nucleophiles such as water or bases; under these conditions many potentially useful selectors decompose. The general approach to polysiloxane synthesis presented herein gives access to functionalized polysiloxanes under mild conditions. The functional groups incorporated can serve as chromatographic selectors or as electrophilic sites for secondary modification or cross-linking.     

Coordination polymers of silver(I) with bis(N-heterocyclic carbene): Structural characterization and carbene transfer

Reactions of the ethylene- and methylene-bridged bis(imidazolium) salts with an equivalent amount of silver oxide in dichloromethane at room temperature produced readily the silver NHC compounds [Ag₂LBr₂]. These compounds are partially soluble in DMF. The X-ray structure determination on 3d (L = 1,1′-dibenzyl-3,3′-ethylenediimidazolin-2,2′-diylidene) reveals the formation of bromide bibridged (Ag₂LBr₂)_n chains and a unique supramolecular motif with weak Ag?Ag interactions of 3.429 Å. Similar to monomeric silver(I) NHC complexes, the silver coordination polymers can also act as carbene transfer reagents for the formation of chelating palladium NHC complexes in excellent yields.