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Photochromic properties of methylacrylate monomers and polymers containing azobenzene groups with heterocyclic sulfonamide
functionalities viz sulfisomidyne (4-amino-N-[2,6-dimethylpyrimidyn-4-yl]benzenesulfonamide) and sulfamethoxazole (4-amino-N-[5-methylisoxazol-3-yl]benzenesulfonamide)
substituents were investigated. On illumination with light the azobenzene group underwent trans-cis isomerisation, which was manifested by a drop in the absorbance of the maximum absorption peak at ca. 450 nm and by decrease in refractive index.
Quantum chemical calculations showed significant differences in UV-VIS spectra, dipole moments, polarizability and refractive
index between both cis and trans form of the chromophoric monomers.
The illumination of spin-coated polymer films during ellipsometry measurements resulted in a change in refractive index within
the range of 0.014 to 0.025. The dynamics of growth and decay of refractive index changes, was described by biexponential
functions approach. 相似文献
74.
Essential plants, due to their long presence in human history, their status in culinary arts, their use in medicine and perfume manufacture, belong to frequently examined stock materials in scientific and industrial laboratories. Because of a large number of freshly cut, dried or frozen plant samples requiring the determination of essential oil amount and composition, a fast, safe, simple, efficient and highly automatic sample preparation method is needed.Five sample preparation methods (steam distillation, extraction in the Soxhlet apparatus, supercritical fluid extraction, solid phase microextraction and pressurized liquid extraction) used for the isolation of aroma-active components from Thymus vulgaris L. are compared in the paper. The methods are mainly discussed with regard to the recovery of components which typically exist in essential oil isolated by steam distillation.According to the obtained data, PLE is the most efficient sample preparation method in determining the essential oil from the thyme herb. Although co-extraction of non-volatile ingredients is the main drawback of this method, it is characterized by the highest yield of essential oil components and the shortest extraction time required. Moreover, the relative peak amounts of essential components revealed by PLE are comparable with those obtained by steam distillation, which is recognized as standard sample preparation method for the analysis of essential oils in aromatic plants. 相似文献
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Ewelina Stefaniak Elena Atrian-Blasco Wojciech Goch Laurent Sabater Christelle Hureau Wojciech Bal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(8):2798-2809
Alzheimer's disease (AD) is one of the most common of the multifactorial diseases and is characterized by a range of abnormal molecular processes, such as the accumulation of extracellular plaques containing the amyloid-β (Aβ) peptides and dyshomeostasis of copper in the brain. In this study, we have investigated the effect of CuII on the aggregation of Aβ1–40 and Aβ4–40, representing the two most prevalent families of Aβ peptides, that is, the full length and N-truncated peptides. Both families are similarly abundant in healthy and AD brains. For either of the studied peptides, substoichiometric CuII concentrations accelerated aggregation, whereas superstoichiometric CuII inhibited fibril formation, likely by stabilizing the oligomers. The addition of either Aβ4–40 or substoichiometric CuII affected the aggregation profile of Aβ1–40, by yielding shorter and thicker fibrils; amorphous aggregates were formed in the presence of a molar excess of CuII. The similarity of these two effects can be attributed to the increase in the positive charge on the Aβ N terminus, caused both by CuII complexation and N truncation at position 4. Our findings provide a better understanding of the biological Aβ aggregation process as these two Aβ species and CuII coexist and interact under physiological conditions. 相似文献
76.
Ewelina Klem-Marciniak Marta Huculak-Mczka Kinga Marecka Krystyna Hoffmann Jzef Hoffmann 《Molecules (Basel, Switzerland)》2021,26(7)
In application conditions, the influence of environmental parameters on used fertilizer chelates and their distribution over time is important. For this purpose, the changes in the content of micronutrient ions and Fe-EDDHA and Fe-EDDHSA chelates in an aqueous medium at different pH values were studied. In the assumed time, changes in the ions content were analyzed using the voltammetry method at pH 3, 5 and 7. The content of isomers and chelate forms was analyzed by ion pair chromatography at pH 3, 5 and 7. These studies allowed us to determine the effect of pH on the stability of iron chelates over time. 相似文献
77.
Michał Rachwalski Stanisław Leśniak Ewelina Sznajder Piotr Kiełbasiński 《Tetrahedron: Asymmetry》2009,20(13):1547-1549
New tridentate enantiomerically pure heteroatom catalysts, containing hydroxyl, sulfinyl and amino groups, proved to be highly efficient in the enantioselective nitroaldol (Henry) reaction to give the desired adducts in very high yields (up to 90%) and with ees up to 98%. The influence of the stereogenic centres located on the sulfinyl sulfur atom and in the amine moiety is also discussed. 相似文献
78.
Stanisław Leśniak Michał Rachwalski Ewelina Sznajder Piotr Kiełbasiński 《Tetrahedron: Asymmetry》2009,20(20):2311-2314
New tridentate enantiomerically pure heteroorganic catalysts, containing hydroxyl, sulfinyl, and aziridine moieties, have proven to be highly efficient in the enantioselective diethylzinc addition to aryl and alkyl aldehydes to give the desired products in very high yields (up to 99%) and with ee’s up to 97%. The influence of the stereogenic centers located on the sulfinyl sulfur atom and in the aziridine moiety on the stereochemical course of the reaction are discussed. 相似文献
79.
Sodium and potassium thiocyanate complex compounds of formulae [Na(hmta)(H2O)4]22+·2SCN− (1) and [K2(hmta)(SCN)2]
n
(2) have been synthesized and characterised by IR spectroscopy, thermogravimetry coupled with differential thermal analysis,
elemental analysis and X-ray crystallography. Each sodium and potassium cation is six co-ordinated, the sodium by one monofunctional
hmta molecule, three terminal water molecules and two bridging water molecules, and the potassium by two bridging tetrafunctional
hmta molecules and four bridging tetrafunctional thiocyanate ions. The coordination polyhedra of the central atoms can be
described as distorted tetragonal bipyramids. The complex cations and anions of (1) are interconnected by multiple intramolecular
O(water)—H···N(hmta/NCS) and O(water)—H···S hydrogen bonds to the three dimensional net. In each complex cation the intramolecular
O–H···O hydrogen bonds link two terminal water molecules bonded to two metal cations. The compound (2) forms the three dimensional
hybrid network in which the classical two-dimensional coordination polymers are linked by inorganic SCN− spacers to the third-dimension. Thermal analyses show that the compounds decompose gradually in three (for 1) and two (for
2) steps with formation of Na2SO4 and K2S as the final products, respectively, for 1 and 2. 相似文献
80.
JPC – Journal of Planar Chromatography – Modern TLC - Lipophilicity is often estimated by thin-layer chromatography (TLC) as a fundamental property related to biological and... 相似文献