Search results for "QD"
showing 10 items of 2226 documents
Titanocene Selenide Sulfides Revisited: Formation, Stabilities, and NMR Spectroscopic Properties
2019
[TiCp2S5] (phase A), [TiCp2Se5] (phase F), and five solid solutions of mixed titanocene selenide sulfides [TiCp2SexS5−x] (Cp = C5H5−) with the initial Se:S ranging from 1:4 to 4:1 (phases B–E) were prepared by reduction of elemental sulfur or selenium or their mixtures by lithium triethylhydridoborate in thf followed by the treatment with titanocene dichloride [TiCp2Cl2]. Their 77Se and 13C NMR spectra were recorded from the CS2 solution. The definite assignment of the 77Se NMR spectra was based on the PBE0/def2-TZVPP calculations of the 77Se chemical shifts and is supported by 13C NMR spectra of the samples. The following complexes in varying ratios were identified in the CS2 solutions of …
6-Methyluracil: a redetermination of polymorph (II)
2019
6-Methyluracil, C5H6N2O2, exists in two crystalline phases: form (I), monoclinic, space group P21/c [Reck et al. (1988). Acta Cryst. A44, 417–421] and form (II), monoclinic, space group C2/c [Leonidov et al. (1993). Russ. J. Phys. Chem. 67, 2220–2223]. The structure of polymorph (II) has been redetermined providing a significant increase in the precision of the derived geometric parameters. In the crystal, molecules form ribbons approximately running parallel to the c-axis direction through N—H...O hydrogen bonds. The radical differences observed between the crystal packing of the two polymorphs may be responsible in form (II) for an increase in the contribution of the polar canonical forms…
The Hexameric Resorcinarene Capsule as a Brønsted Acid Catalyst for the Synthesis of Bis(heteroaryl)methanes in a Nanoconfined Space
2019
Herein, we show that the hexameric resorcinarene capsule C is able to catalyze the formation of bis(heteroaryl)methanes by reaction between pyrroles or indoles and carbonyl compounds (α-ketoesters or aldehydes) in excellent yields and selectivity. Our results suggest that the capsule can play a double catalytic role as a H-bond catalyst, for the initial activation of the carbonyl substrate, and as a Bronsted acid catalyst, for the dehydration of the intermediate alcohol.
Supramolecular Organocatalysis in Water Mediated by Macrocyclic Compounds
2018
In the last decades many efforts have been devoted to design supramolecular organocatalysts able to work in water as the reaction medium. The use of water as solvent provides promising benefits with respect to environmental impact. In this context, macrocyclic compounds played a role of primary importance thanks to their ease of synthesis and their molecular recognition abilities toward the reactants. The aim of this review is to give an overview of the recent advances in the field of supramolecular organocatalysis in water, focusing the attention on calixarene and cyclodextrins derivatives. Calixarenes and cyclodextrins, thanks to their hydrophobic cavities, are able to host selectively th…
Antibacterial Activity of Positively and Negatively Charged Hematite (α-Fe2O3) Nanoparticles to Escherichia coli, Staphylococcus aureus and Vibrio fi…
2021
This research and work has been supported by the European Regional Development Fund within the Activity 1.1.1.2 “Post-doctoral Research Aid” of the Specific Aid Objective 1.1.1 (i.e., “to increase the research and innovative capacity of scientific institutions of Latvia and the ability to attract external financing, investing in human resources and infrastructure”) of the Operational Programme “Growth and Employment” (No. 1.1.1.2/VIAA/2/18/331).
The Jäntti approach to adsorption with increasing gas pressure
2002
Jäntti introduced a method of calculating equilibrium adsorption from measurements where the pressure of the gas was varied in a stepwise manner. His aim was to shorten the time necessary for a given measurement. The method was applied to gas/solid systems in which simple adsorption processes occurred and where the number of adsorption sites was infinite. The present paper discusses the case where no adsorption is possible on an already occupied site (Langmuir isotherm) while the number of positions available for adsorption is considered limited. The advantages of using a gas pressure that increases linearly with time are evident for studies with this limitation. It is shown that such meas…
A route to simple nonionic surfactants
2016
AbstractA method for the synthesis of nonionic surfactants – N-alkyl-O-(2-hydroxyethyl) carbamates is proposed by acylation of fatty amines with ethylene carbonate without any solvent or catalyst. The surface tension of the prepared surfactants was measured, toxicity and biodegradability were determined for the surfactant with n-dodecyl as a hydrophobic group and N-monosubstituted amide and hydroxyl groups for their hydrophilic part.
Reaction of polyamines with diethyloxalate: a convenient route for the synthesis of tetraazacycloalkanes
2006
International audience; The reactivity of various polyamines with diethyloxalate has been investigated. It appears that, in similar experimental conditions, primary diamines give predominantly [2+2] adducts while the use of secondary benzylated polyamines results in [1+1] condensation. Although the intermediate tetraamides formed in the first case are extremely poorly soluble and show very slow reactivity towards reducing agents, cyclam has been obtained by using ultrasounds during the reaction of the corresponding tetraoxomacrocycle with BH 3 /THF. The [1+1] cyclization reaction of diversely N-benzylated linear tetraamines, whose selective syntheses have been devised herein, gives access t…
Synthesis and selected properties of metallo and metal-free 2,3,9,10,16,17,23,24-octacarboxyphthalocyanines
2015
This review article reports methods of synthe sis and selected physicochemical properties of metallo and metal-free 2,3,9,10,16,17,23,24–octacarboxyphthalocyanines. The most frequently used methods of synthesis for this class of co mpounds are described in this article. Moreover, aggregation, catalytic and photocatalytic properties of these complexes are presented. Potential applications of metallo and metal-free 2,3,9,10,16,17,23,24–octacarboxyphthalocyanines are also given.
Water-Soluble Cuprizone Derivative: Synthesis, Characterization, and in Vitro Studies
2019
The cuprizone mouse model is one of the most accepted model systems for the investigation of oligodendrocyte degeneration, a process critically involved in the pathogenesis of diseases such as multiple sclerosis or schizophrenia. In order to substitute the in vivo experiments by in vitro approaches, the amine derivative BiMPi is introduced as a water-soluble alternative to cuprizone. Regarding superoxide dismutase activity, toxicity for oligodendrocytes, and disturbance of mitochondrial membrane potential, BiMPi shows similar in vitro effects as is observed in vivo for cuprizone. peerReviewed