نتایج جستجو برای: 18 and 24 crown ethers

تعداد نتایج: 16918122  

Journal: :Catalysts 2023

We review crown ether-facilitated nucleophilic reactions using metal salts, presenting the studies kinetic measurements and quantum chemical methods. focus on mechanistic features, specifically contact ion-pair (CIP) mechanism of salts for processes promoted by ethers derivatives. Experimental verification CIP form salt CsF complexed with [18-Crown-6] H-NMR spectroscopy is described. The use ch...

Journal: :Topics in current chemistry 2012
Martin Kaller Sabine Laschat

In this chapter, a comprehensive review over the entire reserarch on liquid crystalline crown ethers since their discovery will be given. Monomeric and polymeric molecules containing crown ethers as well as aza crown ethers, thia crown ethers and crown ethers with several different heteroatoms will be presented. Liquid crystallinity is, in most cases, caused by the substituents attached to the ...

Journal: :The Journal of organic chemistry 2013
Sergey P Gromov Svetlana N Dmitrieva Artem I Vedernikov Nikolay A Kurchavov Lyudmila G Kuz'mina Sergey K Sazonov Yuri A Strelenko Michael V Alfimov Judith A K Howard Evgeny N Ushakov

Novel 2-benzothiazole-, 4-pyridine-, and 2- and 4-quinoline-based styryl dyes containing an N-methylbenzoaza-15(18)-crown-5(6)-ether moiety were synthesized. A detailed electronic spectroscopy study revealed high performance of these compounds as optical molecular sensors for alkali and alkaline-earth metal cations. They were shown to considerably surpass analogous chromoionophores based on N-p...

2016
Phil Liebing Ahmad Zaeni Falk Olbrich Frank T. Edelmann

The crystal and mol-ecular strutures of two solvated forms of [K(18c6)]OAc (18c6 = 18-crown-6 = 1,4,7,10,13,16-hexa-oxa-cyclo-octa-decane and OAc = acetate) were determined by single-crystal X-ray diffraction, namely (acetato-κ2O,O')(1,4,7,10,13,16-hexa-oxa-cyclo-octa-decane-κ6O)potassium dihydrate, [K(CH3COO)(C12H24O6)]·2H2O (1) and (acetato-κ2O,O')aqua-(1,4,7,10,13,16-hexa-oxa-cyclo-octa-deca...

2012
T. Platzner J. K. Thomas

Photochemistry, Fluorescence, Crown Ethers, Biology The complexing of thallous ions (T1+), with the crown ether dibenzo 18 crown-6 polyether (DB) has been studied by NMR, fluorescence, and pulse radiolysis techniques. NMR data show a strong interaction of the T1+ ions with the aromatic moieties. This is also illustrated by a static quenching of the aromatic fluorescence by Tl+. The rates of rea...

2015
Andreea Gabor Corneliu Mircea Davidescu Adina Negrea Mihaela Ciopec Lavinia Lupa

In this study two solid supports, silica and florisil, were impregnated with crown ether (dibenzo-18-crown-6) and Fe(III) ions and their efficiency was compared in the adsorption process of As(V) from aqueous solutions. The solid supports were impregnated with crown ether due to their ability to build complexes with positives ions. Fe(III) was used because of As(V) affinity for it. The impregna...

Journal: :Langmuir : the ACS journal of surfaces and colloids 2014
Tea Mihelj Vlasta Tomašić Nikola Biliškov

18-Crown-6, one of the most relevant crown ethers, and sodium cholate, a steroidal surfactant classified as a natural bile salt, are components of a novel, synthesized coordination complex: 18-crown-6-sodium cholate (18C6·NaCh). Like crown ethers, bile salts act as building blocks in supramolecular chemistry to design new functionalized materials with a desired structure and properties. In orde...

Journal: :Dalton transactions 2017
Fabian Dankert Kirsten Reuter Carsten Donsbach Carsten von Hänisch

Compounds consisting of [M(1,2-disila-[3n]crown-n)]2+ (M = Mg, Ca, Sr, Ba; n = 5, 6) and [Ba(1,2-disila-benzo[18]crown-6)]2+ cations and different anions were obtained by equimolar reaction of the hybrid disila-crown ethers 1,2-disila[15]crown-5 (1), 1,2-disila[18]crown-6 (2) and 1,2-disila-benzo[18]crown-6 (7) with alkaline earth metal salts. Even with strongly coordinating anions such as Br- ...

2017
Carsten von Hänisch

Compounds consisting of [M(1,2-disila-[3n]crown-n)] (M = Mg, Ca, Sr, Ba; n = 5, 6) and [Ba(1,2-disilabenzo[18]crown-6)] cations and different anions were obtained by equimolar reaction of the hybrid disila-crown ethers 1,2-disila[15]crown-5 (1), 1,2-disila[18]crown-6 (2) and 1,2-disila-benzo[18]crown-6 (7) with alkaline earth metal salts. Even with strongly coordinating anions such as Br or I s...

2017
Carsten von Hänisch

Compounds consisting of [M(1,2-disila-[3n]crown-n)] (M = Mg, Ca, Sr, Ba; n = 5, 6) and [Ba(1,2-disilabenzo[18]crown-6)] cations and different anions were obtained by equimolar reaction of the hybrid disila-crown ethers 1,2-disila[15]crown-5 (1), 1,2-disila[18]crown-6 (2) and 1,2-disila-benzo[18]crown-6 (7) with alkaline earth metal salts. Even with strongly coordinating anions such as Br or I s...

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