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41.
Florence Mauger Jean‐Claude Tabet Ivo G. Gut 《Rapid communications in mass spectrometry : RCM》2014,28(13):1433-1443
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Thais R. Cruz Eliada A. Silva Douglas P. Oliveira Daniele M. Martins Patrik D.S. Gois Antonio E.H. Machado Pedro Ivo S. Maia Beatriz E. Goi Benedito S. Lima-Neto Valdemiro P. Carvalho-Jr 《应用有机金属化学》2020,34(5):e5602
Arene ruthenium(II) complexes bearing the cyclic amines RuCl2(η6-p-cymene)(pyrrolidine)] ( 1 ), [RuCl2(η6-p-cymene)(piperidine)] ( 2 ), and [RuCl2(η6-p-cymene)(peridroazepine)] ( 3 ) were successfully synthesized. Complexes 1 – 3 were fully characterized by means of Fourier transform infrared, UV–visible, and NMR spectroscopy, elemental analysis, cyclic voltammetry, computational methods, and one of the complexes was further studied by single crystal X-ray crystallography. These compounds were evaluated as catalytic precursors for ring-opening metathesis polymerization (ROMP) of norbornene (NBE) and atom-transfer radical polymerization (ATRP) of methyl methacrylate (MMA). NBE polymerization via ROMP was evaluated using complexes 1 – 3 as precatalysts in the presence of ethyl diazoacetate (EDA) under different [NBE]/[EDA]/[Ru] ratios, temperatures (25 and 50°C), and reaction times (5–60 min). The highest yields of polyNBE were obtained with [NBE]/[EDA]/[Ru] = 5000/28/1 for 60 min at 50°C. MMA polymerization via ATRP was conducted using 1 – 3 as catalysts in the presence of ethyl-α-bromoisobutyrate (EBiB) as initiator. The catalytic tests were evaluated as a function of the reaction time using the initial molar ratio of [MMA]/[EBiB]/[Ru] = 1000/2/1 at 95°C. The increase in molecular weight as function of time indicates that complexes 1–3 were able to mediate the MMA polymerization with an acceptable rate and some level of control. Differences in the rate of polymerization were observed in the order 3 > 2 > 1 for the ROMP and ATRP. 相似文献
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Dr. Karl Kaupmees Robert Järviste Prof. Dr. Ivo Leito 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(48):17445-17449
The basicity scale of very weak bases has been set up in 1,2‐dichloroethane to give, for the first time, reliable quantitative insights into the basic properties of weak bases in a low‐polarity solvent. The scale contains 30 compounds, including anilines; phosphanes, and carbonyl bases, such as esters and amides, linked by 53 relative basicity measurements. The scale spans more than 12 pKip units, expanding to as low pKip values as possible with our current experimental methodology. 相似文献
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Liping Liao Bing Wu Dr. Evgeniya Kovalska Dr. Vlastimil Mazánek Dr. Martin Veselý Ivo Marek Lucie Spejchalová Prof. Dr. Zdeněk Sofer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(52):13235-13241
The intercalation of cations into layered-structure electrode materials has long been studied in depth for energy storage applications. In particular, Li+-, Na+-, and K+-based cation transport in energy storage devices such as batteries and electrochemical capacitors is closely related to the capacitance behavior. We have exploited different sizes of cations from aqueous salt electrolytes intercalating into a layered Nb2CTx electrode in a supercapacitor for the first time. As a result, we have demonstrated that capacitive performance was dependent on cation intercalation behavior. The interlayer spacing expansion of the electrode material can be observed in Li2SO4, Na2SO4, and K2SO4 electrolytes with d-spacing. Additionally, our results showed that the Nb2CTx electrode exhibited higher electrochemical performance in the presence of Li2SO4 than in that of Na2SO4 and K2SO4. This is partly because the smaller-sized Li+ transports quickly and intercalates between the layers of Nb2CTx easily. Poor ion transport in the Na2SO4 electrolyte limited the electrode capacitance and presented the lowest electrochemical performance, although the cation radius follows Li+>Na+>K+. Our experimental studies provide direct evidence for the intercalation mechanism of Li+, Na+, and K+ on the 2D layered Nb2CTx electrode, which provides a new path for exploring the relationship between intercalated cations and other MXene electrodes. 相似文献
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Cleoci Beninca Tiago André Denck Colman Luiz Gustavo Lacerda Marco Aurélio da Silva Carvalho Filho Ivo Mottin Demiate Gilbert Bannach Egon Schnitzler 《Journal of Thermal Analysis and Calorimetry》2013,111(3):2217-2222
The use of chemically modified starches is widely accepted in various industries, with several applications. In this research, natural cassava starch granules were treated with standard sodium hypochlorite solution at 0.8, 2.0, and 5.0 g Cl/100 g starch. The native and modified starch samples were investigated by means of the following techniques: simultaneous thermogravimetry–differential thermal analysis, which allowed us to verify the thermal decomposition associated with endothermic or exothermic phenomena; and differential scanning calorimetry that was used to determine gelatinization enthalpy as well as the rapid viscoamylographic analysis that provided the pasting temperature and viscosity. By means of non-contact-atomic force microscopy method and X-ray powder patterns diffractometry, it was possible to observe the surface morphology, topography of starch granules, and alterations in the granules’ crystallinity. 相似文献
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Dr. Roberta Pievo Brigitta Angerstein Dr. Alistair J. Fielding Dr. Christian Koch Prof. Dr. Ivo Feussner Prof. Dr. Marina Bennati 《Chemphyschem》2013,14(18):4094-4101
Electron paramagnetic resonance (EPR) spectroscopy in combination with the rapid freeze‐quench (RFQ) technique is a well‐established method to trap and characterize intermediates in chemical or enzymatic reactions at the millisecond or even shorter time scales. The method is particularly powerful for mechanistic studies of enzymatic reactions when combined with high‐frequency EPR (ν≥90 GHz), which permits the identification of substrate or protein radical intermediates by their electronic g values. In this work, we describe a new custom‐designed micro‐mix rapid freeze‐quench apparatus, for which reagent volumes for biological samples as small as 20 μL are required. The apparatus was implemented with homemade sample collectors appropriate for 9, 34, and 94 GHz EPR capillaries (4, 2, and 0.87 mm outer diameter, respectively) and the performance was evaluated. We demonstrate the application potential of the RFQ apparatus by following the enzymatic reaction of PpoA, a fungal dioxygenase producing hydro(pero)xylated fatty acids. The larger spectral resolution at 94 GHz allows the discernment of structural changes in the EPR spectra, which are not detectable in the same samples at the standard 9 GHz frequency. 相似文献