Search results for "Protonation"
showing 10 items of 583 documents
[CuII{(LISQ)˙−}2] (H2L: thioether-appended o-aminophenol ligand) monocation triggers change in donor site from N2O2 to N2O(2)S and valence-tautomerism
2019
Using a potentially tridentate o-aminophenol-based redox-active ligand H2L1 (2-[2-(benzylthio)phenylamino]-4,6-di-tert-butylphenol) in its deprotonated form, [Cu(L1)2] has been synthesized and crystallized as [CuII(L1)2]·CH2Cl2 (1·CH2Cl2). A cyclic voltammetry experiment (in CH2Cl2; V vs. SCE (saturated calomel electrode)) on 1·CH2Cl2 exhibits two oxidative (E = 0.20 V (peak-to-peak separation, ΔEp = 100 mV) and E = 0.90 V (ΔEp = 140 mV)) and two reductive (E = -0.52 V (ΔEp = 110 mV) and E = -0.92 V (ΔEp = 120 mV)) responses. Upon oxidation using a stoichiometric amount of [FeIII(η5-C5H5)2](PF6), 1·CH2Cl2 yielded [Cu(L1)2](PF6) (2). Structural analysis (100 K) reveals that 1·CH2Cl2 is a fou…
Absolute acidity of clay edge sites from ab-initio simulations
2012
International audience; We provide a microscopic understanding of the solvation structure and reactivity of the edges of neutral clays. In particular we address the tendency to deprotonation of the different reactive groups on the (0 1 0) face of pyrophyllite. Such information cannot be inferred directly from titration experiments, which do not discriminate between different sites and whose interpretation resorts to macroscopic models. The determination of the corresponding pKa then usually relies on bond valence models, sometimes improved by incorporating some structural information from ab-initio simulations. Here we use density functional theory based molecular dynamics simulations, comb…
Iso-valence Co(II) and mixed-valence Co(II/III) tetranuclear complexes: Synthesis, structure, magnetic properties and DFT study
2013
Abstract The reaction of Co(ClO4)2·6H2O with symmetrical N4O3 coordinating heptadentate ligand (H3L) in presence of triethylamine yielded cobalt(II) tetranuclear complexes [Co4(L)2](ClO4)2, 1. When the same reaction is carried out with sodium azide instead of triethylamine afforded tetranuclear mixed-valence Co(II/III) species, [Co4(L)2(μ1,3–N3)2](ClO4)2, 2. Here L3− is the deprotonated form of 2,6-bis[{{(1-hydroxy-2-methylpropan-2-yl)(pyridine-2-ylmethyl)}amino}methyl]-4-methylphenol. Complex 1 crystallizes in the cubic system, space group Fd-3c, with unit-cell parameters a = b = c = 43.320(5) A, Z = 48, whereas complex 2 crystallizes in the space group I41/a in the tetragonal crystal syst…
Combined effect of solvent content, temperature and pH on the chromatographic behaviour of ionisable compounds.
2008
The organic solvent content and the pH in the mobile phase are the usual main factors in reversed-phase liquid chromatographic separations, owing to their strong effects on retention and/or selectivity. Temperature is often neglected. However, even in cases where the impact of this factor on selectivity is minor, the reduction in analysis time is still an interesting reason to consider it. In addition, ionisable compounds may exhibit selectivity changes, owing to the interaction of organic solvent and/or temperature with pH. The separation of ionisable compounds (nine diuretics: bendroflumethiazide, benzthiazide, bumetanide, chlorthalidone, furosemide, piretanide, probenecid, trichloromethi…
Preparation and XAFS studies of organotin(IV) complexes with adenosine and related compounds and calf thymus DNA
2007
Complexes of adenosine and related compounds (adenosine-5’-monophosphate, adenosine-5’-triphosphate and pyridoxal-5-phosphate) with Bu2SnO and/or BuSnCl2 were prepared in the solid state. The compositions of the complexes were determined by standard analytical methods. It was found that the complexes contain the organotin(IV) moiety and the ligand in a ratio of 1:1. The FT-IR spectra demonstrated that Bu2SnO reacts with the D-ribose moiety of the ligands, while Bu2SnCl2 is coordinated to the deprotonated phosphate group. The basic part of the ligands does not participate directly in complex formation. Comparison of the experimental Mossbauer Δ (quadrupole splitting) values with those calcul…
Y:BaZrO3 Perovskite Compounds I: DFT Study on the Unprotonated and Protonated Local Structures
2011
Y-doped BaZrO(3) derivatives were studied by density functional theory (DFT) to investigate the local arrangements of the octahedral sites in Pm3m cubic frameworks. Single- and double substitution of zirconium by yttrium were considered, including in the presence of a nearby oxygen vacancy. Although the structural symmetry of undoped barium zirconate was not modified after yttrium doping, the presence of yttrium induced several differences in the oxygen sites around it, according to the local geometrical arrangement of yttrium in the host matrix. As an example, the differences between such oxygen sites were shown in the presence of a proton. In this case, different stabilization energies ch…
“Two-Story” Calix[6]arene-Based Zinc and Copper Complexes: Structure, Properties, and O 2 Binding
2017
International audience; A new “two-story” calix[6]arene-based ligand was synthesized, and its coordination chemistry was explored. It presents a tren cap connected to the calixarene small rim through three amido spacers. X-ray diffraction studies of its metal complexes revealed a six-coordinate ZnII complex with all of the carbonyl groups of the amido arms bound and a five-coordinate CuII complex with only one amido arm bound. These dicationic complexes were poorly responsive toward exogenous neutral donors, but the amido arms were readily displaced by small anions or deprotonated with a base to give the corresponding monocationic complexes. Cyclic voltammetry in various solvents showed a r…
Acid−Base Properties of Synthetic and Natural Polyelectrolytes: Experimental Results and Models for the Dependence on Different Aqueous Media
2008
Protonation constants of several natural and synthetic humates and fulvates were determined by ISE-H+ potentiometry in different ionic media (alkali metal halides and tetraethylammonium iodide) at different ionic strengths and T ) 298.15 K. Experimental data obtained in previous studies of different synthetic (polyacrylates, polymethacrylates, polyacrylate-co-maleate) and naturally occurring (alginate, humic substances) polycarboxylates were also taken into account in the general analysis of acid-base properties of polyelectrolytes. Protonation constants were expressed as a function of the dissociation degree (R) using three models, namely, a simple linear model, the Ho¨gfeldt three-paramet…
Speciation Studies of Bifunctional 3-Hydroxy-4-Pyridinone Ligands in the Presence of Zn2+ at Different Ionic Strengths and Temperatures
2019
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Thermodynamics and kinetics of ion permeation in wild-type and mutated open active conformation of the human α7 nicotinic receptor
2020
Molecular studies of human pentameric ligand-gated ion channels (LGICs) expressed in neurons and at neuromuscular junctions are of utmost importance in the development of therapeutic strategies for neurological disorders. We focus here on the nicotinic acetylcholine receptor nAChR-α7, a homopentameric channel widely expressed in the human brain, with a proven role in a wide spectrum of disorders including schizophrenia and Alzheimer's disease. By exploiting an all-atom structural model of the full (transmembrane and extracellular) protein in the open, agonist-bound conformation we recently developed, we evaluate the free energy and the mean first passage time of single-ion permeation using …