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101.
Natalia Tiessen Dr. Nico Schwarze Mira Keßler Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Berthold Hoge 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(43):11041-11044
While alkyl-substituted siloxanes are widely known, virtually nothing is known about perfluoroalkyl siloxanes and their congener species, the silanols and silanolates. We recently reported on the tris(pentafluoroethyl)silanide ion, [Si(C2F5)3]−, which features Lewis amphoteric character deriving from the pentafluoroethyl substituents and their strong electron-withdrawing properties. Transferring this knowledge, we investigated the Lewis amphoteric behavior of the tris(pentafluoroethyl)silanolate, [Si(C2F5)3O]−. In order to examine such Lewis amphoteric behavior, we first developed a strategy for the synthesis of the corresponding silanol Si(C2F5)3OH, which readily condenses at room temperature to the hexakis(pentafluoroethyl)disiloxane, (C2F5)3SiOSi(C2F5)3. Deprotonation of Si(C2F5)3OH employing a sterically demanding phosphazene base allows the characterization of the first example of a dimeric triorganosilanolate: the dianionic hexakis(pentafluoroethyl)disilanolate, [{Si(C2F5)3O}2]2−, implies Lewis amphoteric character of the monomeric [Si(C2F5)3O]− anion. 相似文献
102.
103.
Egor A. Kapitonov Natalia N. Petrova Vasilii V. Mukhin Leonid A. Nikiforov Vladimir D. Gogolev Ee Le Shim Aitalina A. Okhlopkova Jin-Ho Cho 《Molecules (Basel, Switzerland)》2021,26(4)
The physical and mechanical properties of nitrile–butadiene rubber (NBR) composites with N-cetylpyridinium bromide-carbon black (CPB-CB) were investigated. Addition of 5 parts per hundred rubber (phr) of CPB-CB into NBR improved the tensile strength by 124%, vulcanization rate by 41%, shore hardness by 15%, and decreased the volumetric wear by 7% compared to those of the base rubber-CB composite. 相似文献
104.
Natalia A. Danilkina Ekaterina V. Andrievskaya Anna V. Vasileva Anna G. Lyapunova Andrey M. Rumyantsev Andrey A. Kuzmin Elena A. Bessonova Irina A. Balova 《Molecules (Basel, Switzerland)》2021,26(24)
A new type of fluorogenic and fluorochromic probe based on the reduction of weakly fluorescent 4-azido-6-(4-cyanophenyl)cinnoline to the corresponding fluorescent cinnoline-4-amine was developed. We found that the fluorescence of 6-(4-cyanophenyl)cinnoline-4-amine is strongly affected by the nature of the solvent. The fluorogenic effect for the amine was detected in polar solvents with the strongest fluorescence increase in water. The environment-sensitive fluorogenic properties of cinnoline-4-amine in water were explained as a combination of two types of fluorescence mechanisms: aggregation-induced emission (AIE) and excited state intermolecular proton transfer (ESPT). The suitability of an azide–amine pair as a fluorogenic probe was tested using a HepG2 hepatic cancer cell line with detection by fluorescent microscopy, flow cytometry, and HPLC analysis of cells lysates. The results obtained confirm the possibility of the transformation of the azide to amine in cells and the potential applicability of the discovered fluorogenic and fluorochromic probe for different analytical and biological applications in aqueous medium. 相似文献
105.
Elena S. Osipova Ekaterina S. Gulyaeva Evgenii I. Gutsul Vladislava A. Kirkina Alexander A. Pavlov Yulia V. Nelyubina Andrea Rossin Maurizio Peruzzini Lina M. Epstein Natalia V. Belkova Oleg A. Filippov Elena S. Shubina 《Chemical science》2021,12(10):3682
The reaction between basic [(PCP)Pd(H)] (PCP = 2,6-(CH2P(t-C4H9)2)2C6H4) and acidic [LWH(CO)3] (L = Cp (1a), Tp (1b); Cp = η5-cyclopentadienyl, Tp = κ3-hydridotris(pyrazolyl)borate) leads to the formation of bimolecular complexes [LW(CO)2(μ-CO)⋯Pd(PCP)] (4a, 4b), which catalyze amine-borane (Me2NHBH3, tBuNH2BH3) dehydrogenation. The combination of variable-temperature (1H, 31P{1H}, 11B NMR and IR) spectroscopies and computational (ωB97XD/def2-TZVP) studies reveal the formation of an η1-borane complex [(PCP)Pd(Me2NHBH3)]+[LW(CO3)]− (5) in the first step, where a BH bond strongly binds palladium and an amine group is hydrogen-bonded to tungsten. The subsequent intracomplex proton transfer is the rate-determining step, followed by an almost barrierless hydride transfer. Bimetallic species 4 are easily regenerated through hydrogen evolution in the reaction between two hydrides.Bimetallic complexes [LW(CO)2(μ-CO)⋯Pd(PCP)] cooperatively activate amine-boranes for their dehydrogenation via N–H proton tunneling at RDS and H2 evolution from two neutral hydrides. 相似文献
106.
Type III dicopper centres are the heart of the reactive sites of enzymes that catalyze the oxidation of catechols. Numerous synthetic model complexes have been prepared to uncover the fundamental chemistry involved in these processes, but progress is still lagging much behind that for heme enzymes. One reason is that the latter gain very much from the informative spectroscopic features of their porphyrin-based metal-chelating ligand. We now introduce sapphyrin-chelated dicopper complexes and show that they may be isolated in different oxidation states and coordination geometries, with distinctive colors and electronic spectra due to the heme-like ligands. The dicopper(i) complex 1-Cu2 was characterized by 1H and 19F NMR spectroscopy of the metal-chelating sapphyrin, the oxygenated dicopper(ii) complex 1-Cu2O2 by EPR, and crystallographic data was obtained for the tetracopper(ii)-bis-sapphyrin complex [1-Cu2O2]2. This uncovered a non-heme [Cu4(OH)4]4− cluster, held together with the aid of two sapphyrin ligands, with structural features reminiscent of those of catechol oxidase. Biomimetic activity was demonstrated by the 1-Cu2O2 catalyzed aerobic oxidation of catechol to quinone; the sapphyrin ligand aided very much in gaining information about reactive intermediates and the rate-limiting step of the reaction.Di-copper chelation by sapphyrin facilitates reaction mechanism investigations and characterization of reactive intermediates regarding biomimetic catechol oxidation. 相似文献
107.
Victor U. Weiss Natalia Denderz Günter Allmaier Martina Marchetti-Deschmann 《Electrophoresis》2021,42(11):1202-1208
Gas-phase electrophoresis yields size distributions of polydisperse, aerosolized analytes based on electrophoretic principles. Nanometer-sized, surface-dry, single-charged particles are separated in a high laminar sheath flow of particle-free air and an orthogonal tunable electric field. Additionally, nano Electrospray Gas-Phase Electrophoretic Mobility Molecular Analyzer (nES GEMMA) data are particle-number based. Therefore, small particles can be detected next to larger ones without a bias, for example, native proteins next to their aggregates. Analyte transition from the liquid to the gas phase is a method inherent prerequisite. In this context, nonvolatile sample buffers influence results. In the worst case, the (bio-)nanoparticle signal is lost due to an increased baseline and unspecific clustering of nonvolatile components. We present a novel online hyphenation of liquid chromatography and gas-phase electrophoresis, coupling a size-exclusion chromatography (SEC) column to an advanced nES GEMMA. Via this novel approach, it is possible to (i) separate analyte multimers already present in liquid phase from aggregates formed during the nES process, (ii) differentiate liquid phase and spray-induced multimers, and (iii) to remove nonvolatile buffer components online before SEC–nES GEMMA analysis. Due to these findings, SEC–nES GEMMA has the high potential to help to understand aggregation processes in biological buffers adding the benefit of actual size determination for noncovalent assemblies formed in solution. As detection and characterization of protein aggregation in large-scale pharmaceutical production or sizing of noncovalently bound proteins are findings directly related to technologically and biologically relevant situations, we proposed the presented method to be a valuable addition to LC-MS approaches. 相似文献
108.
Dr. Pritam Ghosh Dr. Natalia Fridman Prof. Dr. Galia Maayan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(2):634-640
The construction of synthetic protein mimics is a central goal in chemistry. A known approach for achieving this goal is the self-assembly of synthetic biomimetic sequences into supramolecular structures. Obtaining different 3D structures via a simple sequence modification, however, is still challenging. Herein we present the design and synthesis of biomimetic architectures, via the self-assembly of distinct copper-peptoid duplexes. We demonstrate that changing only one non-coordinating side-chain within the peptoids—sequence-specific N-substituted glycine oligomers—leads to different supramolecular structures. Four peptoid trimers incorporating 2,2’-bipyridine and pyridine ligands, and a non-coordinating but rather a structure-directed bulky group were synthesized, and their solutions were treated with Cu2+ in a 1:1 ratio. Single-crystal X-ray analysis of the products revealed the self-assembly of each peptoid into a metallopeptoid duplex, followed by the self-assembly of multiple duplexes and their packing into a three-dimensional supramolecular architecture via hydrogen bonding and π–π interactions. Tuning the non-coordinating side-chain enables to regulate both the final structure being either a tightly packed helical rod or a nano-channel, and the pore width of the nano-channels. Importantly, all the metallopeptoids structures are stable in aqueous solution as verified by cryo-TEM measurements and supported by UV/Vis and EPR spectroscopies and by ESI-MS analysis. Thus, we could also demonstrate the selective recognition abilities of the nano-channels towards glycerol. 相似文献
109.
Dr. Lina M. Aguirre-Díaz Marcelo Echeverri Dr. Katherine Paredes-Gil Dr. Natalia Snejko Dr. Berta Gómez-Lor Prof. Dr. Enrique Gutiérrez-Puebla Prof. Dr. M. Ángeles Monge 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5298-5306
Three new cadmium-based coordination polymers, denoted [Cd(hfipbb)(4,4’-bipy)] ( CdPF-1 ), [Cd(hfipbb)(2,2’-bipy)] ( CdPF-2 ), and [Cd(hfipbb)(1,10-phen)] ( CdPF-3 ), have been hydrothermally synthesized by using the well-known V-shaped organic linker 4,4’-(hexafluoroisopropylidene)bis(benzoic acid) (H2hfipbb), together with different nitrogenated auxiliary linkers. Considering the d10 configuration of the transition metal selected, the luminescent properties for these CdPF-n materials were explored, finding that materials CdPF-2 and CdPF-3 act as excellent sensors in the detection of explosive nitro aromatic compounds. The photoluminescence properties of CdPF-2 and CdPF-3 revealed that significant and sensitive fluorescence quenching was observed toward NP (nitrophenol) for CdPF-2 and PA (picric acid) for CdPF-3 in MeOH suspensions. 相似文献
110.
Katarzyna Godlewska Pawe&#x; Pacyga Izabela Michalak Anita Biesiada Antoni Szumny Natalia Pachura Urszula Piszcz 《Molecules (Basel, Switzerland)》2021,26(7)
Nutraceuticals and functional foods are gaining more attention amongst consumers interested in nutritious food. The consumption of foodstuffs with a high content of phytochemicals has been proven to provide various health benefits. The application of biostimulants is a potential strategy to fortify cultivated plants with beneficial bioactive compounds. Nevertheless, it has not yet been established whether the proposed higher plants (St. John’s wort, giant goldenrod, common dandelion, red clover, nettle, and valerian) are appropriate for the production of potential bio-products enhancing the nutritional value of white cabbage. Therefore, this research examines the impact of botanical extracts on the growth and nutritional quality of cabbage grown under field conditions. Two extraction methods were used for the production of water-based bio-products, namely: ultrasound-assisted extraction and mechanical homogenisation. Bio-products were applied as foliar sprays to evaluate their impact on total yield, dry weight, photosynthetic pigments, polyphenols, antioxidant activity, vitamin C, nitrates, micro- and macroelements, volatile compounds, fatty acids, sterols, and sugars. Botanical extracts showed different effects on the examined parameters. The best results in terms of physiological and biochemical properties of cabbage were obtained for extracts from common dandelion, valerian, nettle, and giant goldenrod. When enriched with nutrients, vegetables can constitute a valuable component of functional food. 相似文献