Search results for "SOLVENT"
showing 10 items of 1395 documents
The first catalytic method for Heck alkynylation of unactivated aryl bromides (copper-free Sonogashira) in an ionic liquid: 1 mol-percent palladium/t…
2007
Herein we report the studies of Heck alkynylation (copper-free Sonogashira) with aryl halides (I, Br, Cl) employing various metallic precursors, tertiary phosphanes and bases in [BMIM][BF4] as the solvent. As a result, we provide the first method that allows the coupling of a large array of substrates, either activated or deactivated bromides in an ionic liquid. Furthermore, the system of highest efficiency is unexpectedly the simplest and cheaper combination that employs [Pd(η3-C3H5)Cl]2/PPh3 at only a 1 mol-% loading with pyrrolidine as the base and in the absence of a copper salt. The coupling of sterically and electronically deactivated bromides bearing different functional groups to ar…
Polymorphism and versatile solvate formation of thiophanate-methyl
2009
The polymorphism of a fungicide, thiophanate-methyl (TM), was investigated with conventional solvent screening methods. Two polymorphs, the thermodynamically most stable form I and the less stable form II, were found. TM was also found to crystallize as a plethora of different solvates which produced mostly form II upon desolvation. The structures of form I and form II and the fourteen discovered solvates were solved by single crystal X-ray diffraction. The most stable forms were further characterized by powder diffraction, thermoanalytical (TG/DTA, DSC and thermomicroscopy) and spectroscopic (IR, Raman, ¹³C CP/MAS NMR) methods. peerReviewed
Host-guest complexes of C-propyl-2-bromoresorcinarene with aromatic N-oxides*
2018
The host-guest complexes of C-propyl-2-bromoresorcinarene with pyridine N-oxide, 3-methylpyridine N-oxide, quinoline N-oxide and isoquinoline N-oxide are studied using single crystal X-ray crystallography and 1H NMR spectroscopy. The C-propyl-2-bromoresorcinarene forms endo-complexes with the aromatic N-oxides in the solid-state when crystallised from either methanol or acetone. In solution, the endo-complexes were observed only in methanol-d4. In DMSO the solvent itself is a good guest, and crystallisation provides only solvate endo-complexes. The C-propyl-2-bromoresorcinarene shows remarkable flexibility when crystallised from either methanol or acetone, and packs into one-dimensional sel…
Unexpected behaviour of copper(I) towards a tridentate Schiff base: Synthesis, structure and properties of new Cu(I)-Cu(II) and Cu(II) complexes
2001
cited By 17; International audience; The reaction of CuBr with 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine L afforded a new Cu(I)-Cu(II) derivative [CuBrL]2[Cu2Br4] (1), while the reaction of [Cu(CH3CN)4]PF6 with L in THF yielded the new Cu(I) compound CuL(THF)(CH3CN)PF6 (2). Derivative 2 further reacted with halogenated solvents to yield halogeno-Cu(II) salts, [CuClL]PF6 (3) using CHCl3 and [CuBrL]Br3 (4) using CHBr3. Compounds 1, 3 and 4 have been fully characterised by X-ray crystallography; they contain essentially similar [CuXL]+ cations with a square planar copper(II) co-ordination. However, the structure of compound 1 must be viewed as built of tetranuclear units since two […
Augstskolas absolventu darba kvalitātes saistība ar sociālo kapitālu un cilvēkkapitālu
2017
Maģistra darba mērķis ir noteikt strādājošo augstskolas absolventu darba kvalitāti un tās saistību ar sociālo kapitālu un cilvēkkapitālu. Pētījumā aptaujāts 151 absolvents, kurš anketas pildīšanas brīdī strādāja un bija absolvējis augstskolu no 2014. līdz 2016. gadam, un raksturoja savas darbavietas kvalitāti, iegūto izglītību, darba pieredzi un ego-tīklu. Secināts, ka izlasē augsta darba satura kvalitāte ir grupā, kurai ir iepriekšēja darba pieredze nozarē. Rezultāti apstiprina, ka vīrieši tiek biežāk novērtēti kā starpnieki informācijas apmaiņā, lai gūtu labākas darbavietas. Sociālo zinātņu absolventu vidū augsta darba kvalitāte ir saistīta ar iespēju uzzināt informāciju no cilvēkiem, kas…
Liquid structure of a choline chloride-water natural deep eutectic solvent: A molecular dynamics characterization
2021
The liquid structure of a representative of the first water-in-salt (WiS) Natural Deep Eutectic Solvents (NADES), hereinafter indicated as aquoline, a mixture of choline chloride (ChCl) and water with molar ratio 1:3.33, is ex- plored at ambient conditions. Using Molecular Dynamics (MD) simulation tools, we extract structural informa- tion at atomistic level on the nature of inter-correlations between the different moieties. Despite being a very fluid liquid, with much lower viscosity than other common ChCl-based DES, aquoline turns out to be very struc- tured. Computed X-ray and neutron weighted scattering patterns (the latter also on selectively deuterated mix- tures) highlight the existe…
Structural Features of β-Cyclodextrin Solvation in the Deep Eutectic Solvent, Reline
2020
The inherently amphiphilic nature of native cyclodextrins (CDs) determines their peculiar molecular encapsulation features, enabling applications such as targeted drug nanodelivery, aroma protection, etc. On the contrary, it may also lead to poor solubility in water and other organic solvents and to potentially detrimental flocking in these media, thus posing limitations to more extensive usage. Here we use small angle X-ray scattering to show that deep eutectic solvent reline (1:2 choline chloride:urea) succeeds in dissolving large amounts of beta-CD (at least 800 mg/mL, compared with the solubility in water of 18 mg/mL), without aggregation phenomena occurring. At the microscopic level, m…
Real-time observation of the charge transfer to solvent dynamics
2013
Intermolecular electron-transfer reactions have a crucial role in biology, solution chemistry and electrochemistry. The first step of such reactions is the expulsion of the electron to the solvent, whose mechanism is determined by the structure and dynamical response of the latter. Here we visualize the electron transfer to water using ultrafast fluorescence spectroscopy with polychromatic detection from the ultraviolet to the visible region, upon photo-excitation of the so-called charge transfer to solvent states of aqueous iodide. The initial emission is short lived (similar to 60 fs) and it relaxes to a broad distribution of lower-energy charge transfer to solvent states upon rearrangeme…
Electrocatalytic rate constants from DFT simulations and theoretical models: Learning from each other
2022
Electrochemical interfaces present an extraordinarily complex reaction environment and several, often counter-acting, interactions contribute to rate constants of electrocatalytic reactions. We compile a short review on how electrode potential, solvent, electrolyte, and pH effects on electrocatalytic rates can be understood and modelled using computational and theoretical methods. We address the connections between computational models based on DFT and (semi)analytical model Hamiltonians to extract physical or chemical insights, identify some omissions in present DFT simulation approaches and analytic models, and discuss what and how simulations and models could learn from each other. peerR…
Control of Morphology and Corona Composition in Aggregates of Mixtures of PS-b-PAA and PS-b-P4VP Diblock Copolymers: Effects of Solvent, Water Conten…
2014
The morphologies and corona compositions in aggregates of mixtures of PS-b-PAA and PS-b-P4VP diblock copolymers are influenced by controllable assembly parameters such as water content, block copolymer molar ratios, and solvent effects as well as the hydrophilic block lengths and block length ratios. All these factors can affect the morphology of the aggregates as well as their corona composition, the latter especially in vesicles, where two interfaces are involved. The morphologies and corona compositions of the aggregates were investigated by transmission electron microscopy and electrophoretic mobility, respectively. They depend, to a large extent, on the solubility of P4VP and PAA in th…