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Wyszukujesz frazę "aromatic compounds" wg kryterium: Temat


Tytuł:
Anion-Based Self-assembly of Resorcin[4]arenes and Pyrogallol[4]arenes
Autorzy:
Chwastek, Monika
Cmoch, Piotr
Szumna, Agnieszka
Wydawca:
American Chemical Society
Cytata wydawnicza:
ournal of the American Chemical Society 2022, 144 (12), 5350-5358. https://doi.org/10.1021/jacs.1c11793
Opis:
Spatial sequestration of molecules is a prerequisite for the complexity of biological systems, enabling the occurrence of numerous, often non-compatible chemical reactions and processes in one cell at the same time. Inspired by this compartmentalization concept, chemists design and synthesize artificial nanocontainers (capsules and cages) and use them to mimic the biological complexity and for new applications in recognition, separation, and catalysis. Here, we report the formation of large closed-shell species by interactions of well-known polyphenolic macrocycles with anions. It has been known since many years that C-alkyl resorcin[4]arenes (R4C) and C-alkyl pyrogallol[4]arenes (P4C) narcissistically self-assemble in nonpolar solvents to form hydrogen-bonded capsules. Here, we show a new interaction model that additionally involves anions as interacting partners and leads to even larger capsular species. Diffusion-ordered spectroscopy and titration experiments indicate that the anion-sealed species have a diameter of >26 Å and suggest stoichiometry (M)6(X–)24 and tight ion pairing with cations. This self-assembly is effective in a nonpolar environment (THF and benzene but not in chloroform), however, requires initiation by mechanochemistry (dry milling) in the case of non-compatible solubility. Notably, it is common among various polyphenolic macrocycles (M) having diverse geometries and various conformational lability.
National Science Centre (grant SYMFONIA 2016/20/W/ST5/00478 and OPUS 2017/25/B/ST5/01011) Wroclaw Centre for Networking and Supercomputing (grant no. 299)
Dostawca treści:
Repozytorium Centrum Otwartej Nauki
Artykuł
Tytuł:
Pyrotechnic Countermeasures: V. Performance of Spectral Flare Compositions Based on Aromatic Compounds
Autorzy:
Koch, E. Ch.
Tematy:
spectral flare
aromatic compounds
decoy flare
pyrotechnic countermeasures
Pokaż więcej
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Powiązania:
https://bibliotekanauki.pl/articles/358551.pdf  Link otwiera się w nowym oknie
Opis:
The radiometric performance and burn rate of four spectral fare compositions (R-X) based on 1,4-dicyanobenzene (1), 3,5-dinitrobenzonitrile (2), E-stilbene (3) and 9,10-dihydroanthracene (4), potassium perchlorate and polyacrylate binder are described. The burn rates, spectral effciencies, Eλ, in both α- and β-band have been determined. The composition R-4 displays the highest effciency in both α- and β-band as well as lowest color ratio, θ B/A. R-1 yields the highest color ratio and second highest spectral effciency in β-band. For part IV see Ref. [1].
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Polarized, V-Shaped, and Conjoined Biscoumarins: From Lack of Dipole Moment Alignment to High Brightness
Autorzy:
Morawski, Olaf
Vygranenko, Kateryna V.
Gryko, Daniel T.
Kielesiński, Łukasz
Deperasińska, Irena
Ouellette, Erik T.
Wydawca:
American Chemical Society
Cytata wydawnicza:
J. Org. Chem. 2022, 87, 5961−5975 . https://doi.org/10.1021/acs.joc.2c00232
Opis:
Polish National Science Center, Poland (OPUS 2020/37/B/ST4/00017) QuantERA programme─project 2017/25/Z/ST2/03038 Foundation for Polish Science (TEAM POIR.04.04.00-00-3CF4/16-00) EU’s Horizon 2020 research and innovation programme under grant agreement no 860762 (MSC ITN CHAIR) Director, Office of Science, Office of Basic Energy Sciences, of the U.S. DOE under contract no. DE-AC02-05CH11231
Eleven conjoined coumarins possessing a chromeno[3,4-c]chromene-6,7-dione skeleton have been synthesized via the reaction of electron-rich phenols with esters of coumarin-3-carboxylic acids, catalyzed by either Lewis acids or 4-dimethylaminopyridine. Furthermore, Michael-type addition to angular benzo[f]coumarins is possible, leading to conjugated helical systems. Arrangement of the electron-donating amino groups at diverse positions on this heterocyclic skeleton makes it possible to obtain π-expanded coumarins with emission either sensitive to, or entirely independent of, solvent polarity with large Stokes shifts. Computational studies have provided a rationale for moderate solvatochromic effects unveiling the lack of collinearity of the dipole moments in the ground and excited states. Depending on the functional groups present, the obtained dyes are highly polarized with dipole moments of ∼14 D in the ground state and ∼20–25 D in the excited state. Strong emission in nonpolar solvents, in spite of the inclusion of a NO2 group, is rationalized by the fact that the intramolecular charge transfer introduced into these molecules is strong enough to suppress intersystem crossing yet weak enough to prevent the formation of dark twisted intramolecular charge transfer states. Photochemical transformation of the dye possessing a chromeno[3,4-c]pyridine-4,5-dione scaffold led to the formation of a spirocyclic benzo[g]coumarin.
Dostawca treści:
Repozytorium Centrum Otwartej Nauki
Artykuł
Tytuł:
Template driven self-assembly of the pentacene structure on the Si(553)-Pb surface
Autorzy:
Palotas, Krisztian
Dachniewicz, Marek
Jałochowski, Mieczysław
Krawiec, Mariusz
Nita, Paweł
Opis:
The self-assembly of the pentacene molecules on the Pb-ordered Si(553) surface is studied with scanning tunneling microscopy and density functional theory methods. Within the surface coverage up to a single monolayer, pentacene was found to form two different chain-like structures. They vary in molecular density, but both exhibit long-range, one-dimensional ordering with longer molecular axes aligned along step edges. The low-density phase consists of single discontinuous molecular rows and adapts the template surface periodicity, while the high-density phase features triple molecular chains with the unit cell determined by the length of the pentacene molecules. Such an arrangement of the molecules is controlled by a subtle balance between molecule–molecule and molecule–substrate interactions.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
From 2,5-Diformyl-1,4-dihydropyrrolo[3,2-b]pyrroles to Quadrupolar, Centrosymmetric Two-Photon-Absorbing A–D–A Dyes
Autorzy:
Kamada, Kenji
Tasior, Mariusz
Gryko, Daniel T.
Kowalczyk, Paweł
Ozaki, Shuhei
Wydawca:
American Chemical Society
Cytata wydawnicza:
Org. Lett. 2022, 24, 2551−2555. https://doi.org/10.1021/acs.orglett.2c00718
Opis:
An original approach has been developed for the insertion of formyl substituents at positions 2 and 5 of 1,4-dihydropyrrolo[3,2-b]pyrroles by conversion of thiazol-2-yl sub stituents. The synthetic utility of these formyl groups was investigated, and a series of centrosymmetric A−π−D−π−A frameworks were constructed. The two-photon absorption of the quadrupolar pyrrolo[3,2-b]pyrrole possessing two dicyanovinyli dene flanking groups is attributed to an S0 → (S1) → S4 transition which has a large TPA cross-section (1300 GM) for a molecule of this size.
Polish National Science Centre, Poland (HARMONIA 2018/30/M/ST5/00460) Foundation for Polish Science (TEAM POIR.04.04.00-00-3CF4/16-00) EC (MSC ITN CHAIR) JSPS KAKENHI Grant No. 21H01887
Dostawca treści:
Repozytorium Centrum Otwartej Nauki
Artykuł
Tytuł:
Areny jako proleki
Arenes as prodrugs
Autorzy:
Guzik, U.
Hupert-Kocurek, K.
Nieć, A.
Wojcieszyńska, D.
Tematy:
prolek
związki aromatyczne
aktywacja proleku
prodrug
aromatic compounds
prodrugs activation
Pokaż więcej
Wydawca:
Polskie Towarzystwo Chemiczne
Powiązania:
https://bibliotekanauki.pl/articles/171928.pdf  Link otwiera się w nowym oknie
Opis:
Nowadays, improvement of physicochemical, biopharmaceutical and pharmacokinetic properties of pharmacologically active compounds is connected with development of prodrugs. Prodrugs are defined as pharmaceutical compounds inactive in their parent form and converted either chemically or enzymatically to the active derivative in the organism. A lot of prodrugs are aromatic compounds because of benzene ring reactivity. There are two main classes of prodrugs. In the carrier-linked prodrugs, the active drug is linked to a carrier through bioreversible covalent bond removed by enzymatic or chemical reactions. The second class comprises bioprecursor prodrugs that are modified in the body to induce the functional groups. Additionally, based on the site of prodrugs conversion into their active forms, they are classified into two groups: prodrugs metabolized intracellulary and prodrugs metabolized extracellulary. Chemical or enzymatic transformation of prodrugs may occur through their reduction, decarboxylation, oxidative deamination, cyclization, phosphorylation and/or hydrolysis. These reactions enable to overcome different barriers in drug delivery through changes in aqueous solubility, chemical instability and insufficient oral adsorption. It may also cause prolonged duration of drug action. Moreover, the prodrugs strategy allows achieving brain and tumor specific targeting. Summarizing, the designing of the prodrugs seems to be one of the most promising strategies to enhance the therapeutic effect of drugs and reduction of their negative side effects.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acylation of aromatic compounds by acid anhydrides using Preysslers anion [NaP5W30O110]14- and heteropolyacids as green catalysts
Autorzy:
Gharib, A.
Jahangir, M.
Scheeren, J.(H.)W.
Tematy:
acylowanie
bezwodniki
heteropolikwasy
katalizator
związki aromatyczne
acylation
Preyssler
anhydride
heteropoly acids
catalyst
aromatic compounds
Pokaż więcej
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Powiązania:
https://bibliotekanauki.pl/articles/779170.pdf  Link otwiera się w nowym oknie
Opis:
The Preyssler, Wells-Dowson and Keggin heteropolyacids are efficient and eco-friendly solid acid catalysts for the acylation of electron-rich aromatic compounds with acid anhydrides. The performance of different forms of heteropolyacids was compared. In all the cases, the best results were obtained using the Preyssler heteropolyacid as the catalyst. In the presence of 25 mol% (with respect to H+ equivalency) Preyssler catalyst, highly para-selective acetylation of anisole occurs using two equivalents of acetic anhydride, in 15 min at room temperature. The isolated yield of the p-methoxyacetophenone product is 98%.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Badania uciążliwości zapachowej odlewni precyzyjnej
Studies of odour nuisance in investment foundry
Autorzy:
Faber, J.
Perszewska, K.
Żmudzińska, M.
Tematy:
ochrona środowiska
związki zapachowe
odlewnia precyzyjna
metoda wytapianych modeli
environmental protection
aromatic compounds
investment foundry
lost-wax casting technology
Pokaż więcej
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Odlewnictwa
Powiązania:
https://bibliotekanauki.pl/articles/391502.pdf  Link otwiera się w nowym oknie
Opis:
Emisja zapachów związana z działalnością różnego rodzaju instalacji przemysłowych czy obiektów jest traktowana jako uciążliwość, a nie szkodliwość dla ludzi i środowiska. Zapach, nawet subiektywnie odczuwany jako przyjemny, przy znacznym stężeniu i dłuższym utrzymywaniu się w powietrzu staje się dokuczliwy i może być powodem złego samopoczucia oraz negatywnych emocji u ludzi przebywających w pobliżu źródła jego emisji. W zależności od stosowanej technologii i rodzaju produkcji prowadzonej w odlewni zapachy z niej emitowane mogą być odczuwane zarówno jako przyjemne lub nieprzyjemne. W artykule przedstawiono wyniki badań składu zapachów emitowanych z odlewni precyzyjnej, w której odlewy produkowane są z zastosowaniem metody wytapianych modeli.
The emission of odours associated with the activities of various industrial plants and facilities is treated as a nuisance, and not as a factor harmful to humans and the environment. The smell, even when subjectively perceived as pleasant, with a significant concentration and longer persistence in the air becomes a nuisance and can cause discomfort and negative emotions in people living near the source of the emissions. Depending on the technology used and the type of production, odours emitted from a foundry can be felt both as pleasant or unpleasant. This paper presents the results of investigations regarding various composition of odours emitted from investment foundry where castings are produced from the lost wax patterns.
Dostawca treści:
Biblioteka Nauki
Artykuł

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