Search results for "Chelation"
showing 10 items of 286 documents
Effects of preorganization in the chelation of UO22+ by hydroxamate ligands: cyclic PIPO– vs linear NMA–
2018
International audience; Many siderophores incorporate as bidentate chelating subunits linear and more seldomly cyclic hydroxamate groups. In this work, a comparative study of the uranyl binding properties in aqueous solution of two monohydroxamic acids, the prototypical linear N-methylacetohydroxamic acid (NMAH) and the cyclic analog 1-hydroxypiperidine-2-one (PIPOH), has been carried out. The complex [UO2(PIPO)(2)(H2O)] crystallized from slightly acidic water solutions (pH < 5), and its molecular structure was determined by X-ray diffraction. The uranyl speciation in the presence of both ligands has been thoroughly investigated in a 0.1 M KNO3 medium at 298.2 K by the combined use of four …
Synthesis and structural investigations on R2Sn(IV)-D-aldonic acid complexes (R = methyl; butyl). Their effect on a new toxicity test organism,Liza s…
2008
Eight R2Sn(IV)-D-aldonate complexes [(R = Me, Bu; D-aldonate = D-galactonate2− (Galn), D-Gluconate2− (Glun), D-Gulonate2− (Guln), D-Ribonate2− (Ribn)], five of which are new derivatives, have been synthesized and structurally characterized both in solid and solution state by IR, 119Sn Mossbauer and 1H, 13C, 119Sn NMR spectroscopies, showing that ligands act as dianonic chelating agents. In solution phase, NMR data suggest that the bidentate chelation is attained by the O1 carboxylate and the vicinal O2 alkoxide atoms, which can be dynamically extended to a third binding site (O4) competing with O2. In Me2Sn(IV)-D-gluconate complex the occurrence of a self-association process leading to a di…
Part 2. Synthesis, characterization and X-ray structure of a new enantiomerically pure bis-equatorial dirhodium(II) compound
2001
Abstract The UV irradiation of an acetone solution of Rh2(O2CCF3)4 and the chiral phosphane (1S, 2S, 5R)-(2-hydroxy-5-isopropenyl-2-methyl-cyclohexyl)diphenylphosphane, (+)PPh2(CHR*OH) leads to the formation of two diastereoisomeric bis-equatorial compounds of formula Rh2(μ-O2CCF3)2(η1-O2CCF3)2(η2-(+)PPh2(CHR*OH))2 P(+)2 and M(+)2 in a 1.5:1 ratio, respectively. Both compounds have been separated by standard column chromatography. The characterization of the enantiomer M(+)2 has been accomplished by X-ray crystallography. The molecular structure consists of an Rh2 4+ unit bridged by two trifluoroacetate ligands. The coordination of each metal center is fulfilled by one phosphine acting …
Mono- and Bidentate Phosphine Ligands in the Palladium-Catalyzed Methyl Acrylate Dimerization
2003
The influence of several phosphine ligands on the activity, selectivity and stability of the catalytic system Pd(acac)2, ligand, [HOEt2][BF4] was studied in the dimerization of methyl acrylate (MA). It was found that the catalyst's activity increased with increasing the basicity of the monodentate ligands used, whereas bulky phosphines lowered the linearity of the dimers and the reaction rates. With chelating P N-, P P-, and P As-ligands the Pd-catalyst could be efficiently stabilized during the reaction. The use of 1-dibutylphosphino-2-dimethylaminoethane as ammonium tetrafluoroborate salt allowed the highest overall activity.
Direct arylation of heterocycles: the performances of ferrocene-based polyphosphane ligands in palladium-catalyzed C-H bond activation
2010
International audience; The palladium-catalyzed direct arylation of alkylated- furan, thiophene, and thiazole and benzoxazole heterocycles with electronically and sterically deactivated bromoarenes was selectively and efficiently promoted by ferrocenyl polyphosphanes. In this C[BOND]H bond activation reaction of heteroaromatics, the performances of polydentate di-, tri-, and tetraphosphane ligands were compared, showing that the triphosphane 1,1′,2-tris(diphenylphosphino)-4-tert-butylferrocene 3 was the most effective for the coupling. The introduction of more electron-donating (iPr) or electron-withdrawing (furyl) groups on the phosphorus atoms did not improve the ligand performances. The …
Optical recognition and removal of Hg(II) using a new self-chemosensor based on a modified amino-functionalized Al-MOF
2017
Abstract We developed a simple self-chemical optical sensor for the monitoring and removal of ultra-trace levels of Hg(II) from aqueous media. The development of this sensor was based on the covalent attachment of amino-functionalized aluminum-based MOF particles with ninhydrin. The new sensor is densely coated with a chelating ligand to permit an ultra-fast, selective, pH-dependent visualization for removal of Hg(II) with detection limit (LOD∼0.494 μg L−1). Monitoring was accomplished via both a colorimetric signal visible to the naked eye as well as UV–vis absorption spectroscopy. Digital image-based colorimetric analysis has also used as a semi-quantitative analysis for determination the…
Gas-chromatographic elemental analysis via di(trifluorethyl)dithiocarbamato-chelates
1986
The capillary-gas-chromatographic conditions for the determination of trace metals after extraction from aqueous solution are optimized by coupling of capillaries and improvement of injection technique. Different detectors (FID and ECD) are tested. pH range and buffer systems for extraction of metal chelates are discussed.
Hybrid Chelator-Based PSMA Radiopharmaceuticals: Translational Approach
2021
(1) Background: Prostate-specific membrane antigen (PSMA) has been extensively studied in the last decade. It became a promising biological target in the diagnosis and therapy of PSMA-expressing cancer diseases. Although there are several radiolabeled PSMA inhibitors available, the search for new compounds with improved pharmacokinetic properties and simplified synthesis is still ongoing. In this study, we developed PSMA ligands with two different hybrid chelators and a modified linker. Both compounds have displayed a promising pharmacokinetic profile. (2) Methods: DATA5m.SA.KuE and AAZTA5.SA.KuE were synthesized. DATA5m.SA.KuE was labeled with gallium-68 and radiochemical yields of various…
EGTA treatment causes the synthesis of heat shock proteins in sea urchin embryos.
2000
Paracentrotus lividus embryos, at post-blastular stage, when subjected to a rise in temperature from physiologic (20 degrees C) to 31 degrees C, synthesize a large group of heat shock proteins (hsps), and show a severe inhibition of bulk protein synthesis. We show, by mono- and two-dimensional electrophoresis, that also EGTA (ethylene glycol-bis[beta-aminoethyl ether] tetraacetic acid) treatment induces in sea urchin embryos both marked inhibition of bulk protein synthesis and the synthesis of the entire set of hsps. Furthermore, EGTA-treated sea urchin embryos are able to survive at a temperature otherwise lethal (35 degrees C) becoming thermotolerant. Because incubation with a different c…
Behaviour of EDTA in marine microcosms
2000
Laboratory-scale microcosm tests were carried out in sea water with and without sediment to investigate the importance of ultraviolet (UV) light and microbes in the temperature-dependent degradation of metal complexes of ethylenediaminetetraacetic acid (EDTA). After 17 weeks, 44% and 48% of the original EDTA (initial concentration 385 microg/L) were converted at 10 degrees C and 22 degrees C, respectively. The degradation was more influenced by UV light than by sediment microbes, although the latter were very important. At both temperatures, absorption of EDTA to the sediment phase reached a maximum in the initial stage of the experiments (4 weeks): at 10 degrees C about 4% and at 22 degree…