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991.
Tomasz Pietrzak Dr. Iwona Justyniak Jiwon Victoria Park Michał Terlecki Łukasz Kapuśniak Prof. Janusz Lewiński 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(10):2503-2510
Despite decades of extensive studies on the reactivity of magnesium alkyls towards O2, the isolation and structural characterization of discrete products of these reactions still remains a challenge. Although the formation of the most frequently encountered magnesium alkoxides through unstable alkylperoxide intermediates has commonly been accepted, the latter species have been elusive for over 100 years. Probing the oxygenation of a seemingly simple well-defined neo-pentylmagnesium complex stabilized by a β-diketiminate ligand, (dippBDI)MgCH2CMe3, we report on the isolation and structure characterization of both a dimeric magnesium alkoxide [(dippBDI)Mg(μ-OCH2CMe3)]2 and the first example of monomeric magnesium alkylperoxide [(dippBDI)Mg(thf)OOCH2CMe3] (dippBDI=[(ArNCMe)2CH]− and Ar=C6H3iPr2-2,6). The formation of monomeric magnesium alkylperoxide demonstrates a crucial role of an additional Lewis base for stabilizing the most elusive oxygenation products likely due to increasing of the electron density on the metal centre. Moreover, the 1H NMR studies at −80 °C revealed that the dissociation of a coordinated Lewis base from the solvated complex (dippBDI)Mg(L)CH2CMe3 (where L=thf or 4-methylpyridine) is likely not required prior to the effective attack of an O2 molecule on the metal centre and the four-coordinate alkylmagnesium complex reacts smoothly with O2 under these conditions. The results can be expected to aid future engineering of various organomagnesium/O2-based reaction systems. 相似文献
992.
Katarzyna awiska Szymon Szufa Remigiusz Modrzewski Andrzej Obraniak Tomasz Wyk Andrzej Rostocki Tomasz P. Olejnik 《Molecules (Basel, Switzerland)》2020,25(22)
This paper presents the results of research on the granulation process of leather industry waste, i.e., tanning shavings. It is economically justified to granulate this waste together with mineral additives that are useful in the processes of their further processing. Unfortunately, the granulation of raw, unsorted shavings does not obtain desired results due to their unusual properties. In this study, the possibilities of agglomeration of this waste were examined by a new method consisting of the production and then the granulation of wet pulp. During granulation, no additional binding liquid is added to the granulated bed. As part of this work, the specific surface of granulated shavings, the granulometric composition of the obtained agglomerates, and their strength parameters were determined. The use of a vibrating disc granulator, the addition of a water glass solution (in the pulp), dolomite, and gypsum made it possible to obtain durable, mechanically stable granules. 相似文献
993.
Gaozhan Xie Miriam Hauschild Hendrik Hoffmann Lukas Ahrens Dr. Frank Rominger Michal Borkowski Dr. Tomasz Marszalek Dr. Jan Freudenberg Prof. Milan Kivala Prof. Uwe H. F. Bunz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(4):799-803
The synthesis, property evaluation, and single crystal X-ray structures of four 5,7,12,14-tetrafunctionalized diazapentacenes are presented. The synthesis of these compounds either starts from tetrabromo-N,N-dihydrodiazapentacene or from a diazapentacene tetraketone. Pd-catalyzed coupling or addition of a lithium acetylide gave the precursors that furnish, after further redox reactions, the diazapentacenes as stable crystalline materials. The performance of the tetraphenyl-substituted compound as n-channel semiconductor was evaluated in organic field effect transistors. 相似文献
994.
995.
Aequationes mathematicae - We study the alienation problem for two general linear equations i.e. we compare the solutions of the system of equations $$\begin{aligned} \left\{ \begin{array}{l}\sum... 相似文献
996.
Bogdan Boduszek Tomasz K. Olszewski Waldemar Goldeman Kamila Grzegolec Patrycja Blazejewska 《Tetrahedron》2012,68(4):1223-1229
The efficient synthesis of new imidazol-2-yl-(amino)methylphosphonic acids, phosphonates phosphinate esters and phosphine oxides is described. The synthetic methodology is based on nucleophilic addition of phosphorus species to imidazole-2 derived imines. Additionally, it was discovered that heating the imidazol-2-yl-(amino)methylphosphonates with aqueous HCl or H2SO4 leads to their decomposition resulting in a rupture of the C–P bond, elimination of the phosphorous-containing fragment and formation of the corresponding secondary imidazole-2 alkylamines. A mechanistic pathway for the cleavage is postulated. 相似文献
997.
Grzegorz Leniec Tomasz Skibiński Slawomir M. Kaczmarek Przemyslaw Iwanowski Marek Berkowski 《Central European Journal of Physics》2012,10(2):500-505
Growth conditions and electron paramagnetic resonance investigations of two well oriented KSm(WO4)2 and KEr(WO4)2 single crystals have been presented and discussed. Hyperfine structure of Sm3+ ion was detected and analyzed for angular and temperature dependences. EPR spectra of KEr(WO4)2 and its angular dependence showed the presence of 5 magnetically nonequivalent Er centers in the crystal. A change in the
type of magnetic interactions was analyzed using mixed (Gaussian and Lorentzian) fits of the EPR spectra. 相似文献
998.
Slawomir M. Kaczmarek Lucyna Macalik Hubert Fuks Grzegorz Leniec Tomasz Skibiński Jerzy Hanuza 《Central European Journal of Physics》2012,10(2):492-499
Well oriented KYb(WO4)2 and KTb0.2Yb0.8(WO4)2 single crystals have been investigated for their magnetic and optical properties using the Raman and EPR techniques. The
registered EPR signal is dominated by three lines ascribed to ytterbium ions: one main and two satellites. Tb ions, although
non-paramagnetic, distinctly modify magnetic properties of the KYb(WO4)2 single crystal. Basic parameters of the spin Hamiltonian, including Zeeman and hyperfine terms (g and A matrices) as well the spatial orientation between principal and crystallographic axes systems were determined for both crystals. 相似文献
999.
Nizio-ukaszewska Zofia Ziemlewska Aleksandra Bujak Tomasz Zagrska-Dziok Martyna Zarbska Magdalena Hordyjewicz-Baran Zofia Wasilewski Tomasz 《Molecules (Basel, Switzerland)》2020,25(22)
Kombucha, also known as the Manchurian mushroom, is a symbiotic culture of bacteria and yeast, the so-called SCOBY. This paper presents a comprehensive evaluation of the ferments obtained from green coffee beans after different fermentation times with kombucha. Results for the ferments were compared to the green coffee extract that was not fermented. In this study, the antioxidant potential of obtained ferments was analyzed by assessing the scavenging of external and intracellular free radicals and the assessment of superoxide dismutase activity. Cytotoxicity of ferments on keratinocyte and fibroblast cell lines was assessed as well as anti-aging properties by determining their ability to inhibit the activity of collagenase and elastase enzymes. In addition, the composition of the obtained ferments and the extract was determined, as well as their influence on skin hydration and transepidermal water loss (TEWL) after application of samples on the skin. It has been shown that the fermentation time has a positive effect on the content of bioactive compounds and antioxidant properties. The highest values were recorded for the tested samples after 28 days of fermentation. After 14 days of the fermentation process, it was observed that the analyzed ferments were characterized by low cytotoxicity to keratinocytes and fibroblasts. On the other hand, the short fermentation time of 7 days had a negative effect on the properties of the analyzed ferments. The obtained results indicate that both green coffee extracts and ferments can be an innovative ingredient of cosmetic products. 相似文献
1000.