Search results for "complexe"
showing 10 items of 920 documents
Polyfunctional recognition of pyridinedicarboxylate anions with macrocyclic polyamine receptors containing heteroaromatic groups.
2008
The interaction of the biologically relevant anions deriving from the six pyridinedicarboxylic acids (H2PDC) with two macrocyclic receptors containing a pentamine chain and a bipyridine (1) or a phenanthroline (2) moiety, as well as with the aliphatic analogue [21]aneN7 (3), was studied by means of spectroscopic methods (UV-vis, NMR) and potentiometric titrations affording the stability constants of the adducts formed. All three receptors form stable complexes with the substrates thanks to the formation of several salt bridges and hydrogen bond contacts, as observed in the crystal structure of the H8[3(2,6-PDC)4] x H2O x 0.5 EtOH solid compound. Additional pi-stacking interactions between t…
Influence of the anions on the structure and magnetic properties of a series of bis(µ-diphexono)-bridged linear trinuclear copper(II) complexes: an e…
2011
The reaction of H(2)L (N,N'-dimethyl-N,N'-bis(2-hydroxy-3-methoxy-5-methylbenzyl)-ethylenediamine) with different copper salts, in methanol and using a H(2)L/Cu = 2 : 3 molar ratio, led to four new bis(μ-diphenoxo)-bridged Cu(3) complexes of general formula [{Cu(S)(μ-L)}(2)Cu(H(2)O)(2n)]X(2) (S = CH(3)OH, n = 1 and X = BF(4)(-) for (1) or ClO(4)(-) for (2); S = Br(3)(-) anion and n = 1 without any X species for (3); S = H(2)O, n = 0 and X = NO(3)(-) for (4)). The use in the same reaction conditions of 4,4'-bipyridine (4,4'-bipy) as connector led to the chain complex [{Cu(μ-4,4'-bipy)(0.5)(μ-L)}(2)Cu(H(2)O)(2n)](ClO(4))(2)·17H(2)O (5). The structure of the centrosymmetric trinuclear unit in …
Ag+ Complexes as Potential Therapeutic Agents in Medicine and Pharmacy
2019
Silver is a non-essential element with promising antimicrobial and anticancer properties. This work is a detailed summary of the newest findings on the bioinorganic chemistry of silver, with a special focus on the applications of Ag+ complexes and nanoparticles. The coordination chemistry of silver is given a reasonable amount of attention, summarizing the most common silver binding sites and giving examples of such binding motifs in biologically important proteins. Possible applications of this metal and its complexes in medicine, particularly as antibacterial and antifungal agents and in cancer therapy, are discussed in detail. The most recent data on silver nanoparticles are also summari…
Oxidative stress protection by manganese complexes of tail-tied aza-scorpiand ligands.
2015
The Mn2+ coordination chemistry of double scorpiand ligands in which two polyazacyclophane macrocycles have been connected by pyridine, phenanthroline and bipyridine spacers has been studied by potentiometry, paramagnetic NMR and electrochemistry. All ligands show high stability with Mn2+ and the complexes were formed in a wide pH range. DFT calculations support the structures and coordination geometries derived from the study. A remarkable antioxidant activity was evidenced for these systems by the McCord-Fridovich assay and in Escherichiacoli sodAsodB deficient bacterial cells. The three systems were tested as anti-inflammatory drugs in human macrophages measuring the accumulation of cyto…
Sustainable bioactive pectin-based films to improve fruit safety via a circular economy approach.
2023
This work reports on the valorisation of persimmon (Diospyros kaki Thunb.) for the development of food-grade antiviral coatings against major viral foodborne pathogens, human noroviruses (NoVs) and hepatitis A virus (HAV). Initially, the antiviral activity of polyphenol-rich pectin extracts with abundant non-covalent interactions (PPN), pectin extracts enriched with intact pectin-polyphenol ester and O-glycosyl bonds (PPC) and hydro-ethanolic polyphenol-rich extracts (EPE) was compared. Higher viral reductions were found for the pectin extracts rich in polyphenols, mainly in those containing covalent pectin-polyphenol interactions. This specific extract was mixed with commercial citrus pect…
Apolipoprotein E Regulates Amyloid Formation within Endosomes of Pigment Cells.
2015
International audience; Accumulation of toxic amyloid oligomers is a key feature in the pathogenesis of amyloid-related diseases. Formation of mature amyloid fibrils is one defense mechanism to neutralize toxic prefibrillar oligomers. This mechanism is notably influenced by apolipoprotein E variants. Cells that produce mature amyloid fibrils to serve physiological functions must exploit specific mechanisms to avoid potential accumulation of toxic species. Pigment cells have tuned their endosomes to maximize the formation of functional amyloid from the protein PMEL. Here, we show that ApoE is associated with intraluminal vesicles (ILV) within endosomes and remain associated with ILVs when th…
Polychromatic femtosecond fluorescence studies of metal–polypyridine complexes in solution
2011
Femtosecond-resolved broadband fluorescence studies are reported for[ M(bpy)(3)](2+) (M = Fe, Ru), RuN3 and RuN719 complexes in solution. We investigated the pump wavelength dependence of the fluorescence of aqueous [ Fe(bpy)(3)](2+) and the solvent and ligand dependence of the fluorescence of Ru-complexes excited at 400 nm. For all complexes, the (MLCT)-M-1 fluorescence appears at zero time delay with a mirror-like image with respect to the absorption. It decays in <= 30-45 fs due to intersystem crossing to the (MLCT)-M-3 states, but a longer lived component of similar to 190 fs additionally shows up in RuN719 and RuN3. No solvent effects are detected. The very early dynamics are character…
The interaction of amino acids with the major constituents of natural waters at different ionic strengths
2000
Abstract The interaction of amino acids with the major constituents of natural waters has been studied potentiometrically by determining protonation constants at different ionic strengths (e.g., I ≤5.6 mol (kg H 2 O) −1 (NaCl)) and in artificial seawater (containing Na + , K + , Ca 2+ , Mg 2+ , Cl − and SO 4 2− ) at different salinities. For glycine determinations in mixed NaCl–MgCl 2 , electrolyte solutions were also performed. The data included in this work, together with some already published, make it possible to calculate parameters for dependence on ionic strength using different models, i.e. an extended Debye–Huckel type equation and Pitzer equations. The results can be interpreted b…
Complexation of the potassium ion by diaza crown compounds in aqueous solutions
1988
The conductance behavior of potassium nitrate in water with and without 1,7,10,16-tetraoxa-4,13-diazacyclooctandecane[2.2] and 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo-8.8.8-exacosane[2.2.2] macrocyclic ligands have been studied in order to analyze the complexation behavior of potassium cations in water. The absence of the complexation found in the [2.2] system is discussed in terms of the ligand structural features (presence of hydrogen bond donor and acceptor sites). The ion pair association constant of potassium cryptate as obtained from conductance measurements is also reported and discussed.
Violurato complexes of nickel(II). Formation equilibria. Deprotonation equilibria of the coordinated ligands and related stereochemical changes
1986
The formation equilibria of nickel(II) violurato-complexes in water and dimethylsulphoxide-water (80∶20) as well as deprotonation of the coordinated ligands and related stereochemical changes are reported. The stability constants of the Ni2+-H2V− complexes logβ1=5.06, Iogβ2=9.38, logβ3=12.98 as well as the acidity constants of the [Ni(H2V)3]− complex, logβj1= 8.37, logβj2=15.76, logβj3=22.37 are determined at 25 °C and 0.1M NaClO4. A new violurato-complex of Ni2+, Na4[Ni(HV)3]5H2O, is isolated and characterized.