Search results for "Anion"
showing 10 items of 488 documents
Pd-Cu catalysts supported on anion exchange resin for the simultaneous catalytic reduction of nitrate ions and reductive dehalogenation of organochlo…
2019
International audience; The present work proposes the simultaneous removal of these classes of pollutants by a catalytic hydrotreatment processes. For this purpose, bimetallic Pd-Cu catalysts (with mass ratio Pd:Cu of 4:1) supported on macroporous strong base anion resin were prepared by different methods. The catalysts were characterized (by XRD, SEMEDX, XPS, AAS and H-2 chemisorption) and tested in a continuous flow system. The selected catalyst preparation protocol consists in a two-step method, which implies the deposition of palladium by ion exchange and the subsequent deposition of copper by controlled reaction on the surface of the pre-reduced palladium. The effectiveness of the cata…
NHC-Stabilized Au10 Nanoclusters and Their Conversion to Au25 Nanoclusters
2022
Herein, we describe the synthesis of a toroidal Au10 cluster stabilized by N-heterocyclic carbene and halide ligands via reduction of the corresponding NHC−Au−X complexes (X = Cl, Br, I). The significant effect of the halide ligands on the formation, stability, and further conversions of these clusters is presented. While solutions of the chloride derivatives of Au10 show no change even upon heating, the bromide derivative readily undergoes conversion to form a biicosahedral Au25 cluster at room temperature. For the iodide derivative, the formation of a significant amount of Au25 was observed even upon the reduction of NHC−Au−I. The isolated bromide derivative of the Au25 cluster displays a…
Chiral hemicucurbit[8]uril as an anion receptor: selectivity to size, shape and charge distribution
2017
A novel eight-membered macrocycle of the hemicucurbit[n]uril family, chiral (all-R)-cyclohexanohemicucurbit[8]uril (cycHC[8]) binds anions in a purely protic solvent with remarkable selectivity. The cycHC[8] portals open and close to fully encapsulate anions in a 1 : 1 ratio, resembling a molecular Pac-Man™. Comprehensive gas, solution and solid phase studies prove that the binding is governed by the size, shape and charge distribution of the bound anion. Gas phase studies show an order of SbF6− ≈ PF6− > ReO4− > ClO4− > SCN− > BF4− > HSO4− > CF3SO3− for anion complexation strength. An extensive crystallographic study reveals the preferred orientations of the anions within the octahedral cav…
Computational investigations of 18-electron triatomic sulfur–nitrogen anions
2018
MRCI-SD/def2-QZVP and PBE0/def2-QZVP calculations have been employed for the analysis of geometries, stabilities, and bonding of isomers of the 18-electron anions N2S2−, NS2−, and NSO−. Isomers of the isoelectronic neutral molecules SO2, S2O, S3, and O3 are included for comparison. The sulfur-centered acyclic NSN2−, NSS−, and NSO− anions are the most stable isomers of their respective molecular compositions. However, the nitrogen-centered isomers SNS− and SNO− lie close enough in energy to their more stable counterparts to allow their occurrence. The experimental structural information, where available, is in good agreement with the optimized bond parameters. The bonding in all investigate…
Foldameerien isäntä-vieraskemia
2017
Tutkielman kirjallisessa osassa tarkastellaan foldameerejä isäntä-vieraskemian näkökulmasta. Foldameerit voivat sitoa rakenteeseensa erilaisia vierasmolekyylejä, jolloin muodostuu isäntä-vieraskomplekseja. Kirjallisuudesta valittiin tarkasteluun mielenkiintoisimpia anioneja, kationeja ja neutraaleja vierasmolekyylejä sitovia foldameereja ja perehdyttiin niiden vuorovaikutuksiin. Lisäksi tarkasteltiin vierasmolekyylin sitoutumisen aikaansaamia muutoksia foldameerien konformaatiossa. Kokeellisen osan tarkoituksena oli syntetisoida pitkä, 11 aromaattista rengasta sisältävä aryyliamidifoldameeri käyttäen hyväksi pääasiassa peptidikytkentäreaktioita. Koska synteesi osoittautui erittäin haasteell…
Oligoamide Foldamers as Helical Chloride Receptors-the Influence of Electron-Withdrawing Substituents on Anion-Binding Interactions.
2019
The anion-binding properties of three closely related oligoamide foldamers were studied using NMR spectroscopy, isothermal titration calorimetry and mass spectrometry, as well as DFT calculations. The 1 H NMR spectra of the foldamers in [D6 ]acetone solution revealed partial preorganization by intramolecular hydrogen bonding, which creates a suitable cavity for anion binding. The limited size of the cavity, however, enabled efficient binding by the inner amide protons only for the chloride anion resulting in the formation of a thermodynamically stable 1:1 complex. All 1:1 chloride complexes displayed a significant favourable contribution of the entropy term. Most likely, this is due to the …
Role of Alkyl Substituent and Solvent on the Structural, Thermal, and Magnetic Properties of Binary Radical Salts of 1,2,3,5-Dithia- or Diselenadiazo…
2022
The synthesis, structural, thermal, and magnetic properties of a series of simple binary organic salts based on the radical anion of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 4-(N-alkylpyridinium-3-yl)-1,2,3,5-dithiadiazolyl (DTDA), 1R (R = Et, Pr, Bu), radical cations and their heavier selenium analogues (DSDA), 2R, are described. Single-crystal X-ray structural analyses reveal that short alkyl substituents on the pyridinium moiety of DTDA/DSDA cations lead to crystallization of isostructural acetonitrile (MeCN) solvates 1Et·MeCN, 1Pr·MeCN, 2Et·MeCN, and 2Pr·MeCN with trans-cofacial DTDA radical cation and eclipsed-cofacial TCNQ radical anion dimers. A slight increase in the substituent …
Oligoamide Foldamers as Helical Chloride Receptors : the Influence of Electron-Withdrawing Substituents on Anion-Binding Interactions
2019
The anion‐binding properties of three closely related oligoamide foldamers were studied using NMR spectroscopy, isothermal titration calorimetry and mass spectrometry, as well as DFT calculations. The 1H NMR spectra of the foldamers in [D6]acetone solution revealed partial preorganization by intramolecular hydrogen bonding, which creates a suitable cavity for anion binding. The limited size of the cavity, however, enabled efficient binding by the inner amide protons only for the chloride anion resulting in the formation of a thermodynamically stable 1:1 complex. All 1:1 chloride complexes displayed a significant favourable contribution of the entropy term. Most likely, this is due to the re…
Solution and solid-state studies on the halide binding affinity of perfluorophenyl-armed uranyl–salophen receptors enhanced by anion–π Interactions
2016
The enhancement of the binding between halide anions and a Lewis acidic uranyl-salophen receptor has been achieved by the introduction of pendant electron- deficient arene units into the receptor skeleton. The association and the occurrence of the elusive anion-p interaction with halide anions (as tetrabutylammonium salts) have been demonstrated in solution and in the solid state, providing unambiguous evidence on the interplay of the concerted interactions responsible for the anion binding.
Influence of bacterial physiology on processing of selenite, biogenesis of nanomaterials and their thermodynamic stability
2019
We explored how Ochrobactrum sp. MPV1 can convert up to 2.5 mM selenite within 120 h, surviving the challenge posed by high oxyanion concentrations. The data show that thiol-based biotic chemical reaction(s) occur upon bacterial exposure to low selenite concentrations, whereas enzymatic systems account for oxyanion removal when 2 mM oxyanion is exceeded. The selenite bioprocessing produces selenium nanomaterials, whose size and morphology depend on the bacterial physiology. Selenium nanoparticles were always produced by MPV1 cells, featuring an average diameter ranging between 90 and 140 nm, which we conclude constitutes the thermodynamic stability range for these nanostructures. Alternativ…