Complex formation and the coordination of zirconium with acetic acid were investigated with Zr K-edge extended X-ray absorption fine structure spectroscopy (EXAFS) and single-crystal diffraction. Zr K-edge EXAFS spectra show that a stepwise increase of acetic acid in aqueous solution with 0.1 M Zr(IV) leads to a structural rearrangement from initial tetranuclear hydrolysis species [Zr(OH)(OH)] to a hexanuclear acetate species Zr(O)(OH)(CHCOO). The solution species Zr(O)(OH)(CHCOO) was preserved in crystals by slow evaporation of the aqueous solution. Single-crystal diffraction reveals an uncharged hexanuclear cluster in solid Zr(μ-O)(μ-OH)(CHCOO)·8.5HO. EXAFS measurements show that the structures of the hexanuclear zirconium acetate cluster in solution and the solid state are identical.
In the presence of polyborates (detected by (11)B-NMR) the formation of a weak Eu(III) borate complex (lg β11 ~ 2, estimated) was observed by time-resolved laser-induced fluorescence spectroscopy (TRLFS). This complex is a precursor for the formation of a solid Eu(III) borate species. The formation of this solid in solution was investigated by TRLFS as a function of the total boron concentration: the lower the total boron concentration, the slower is the solid formation. The solid Eu(III) borate was characterized by IR spectroscopy, powder XRD and solid-state TRLFS. The determination of the europium to boron ratio portends the existence of pentaborate units in the amorphous solid.
Thermodynamic parameters for the complex formation of Am(iii) and Eu(iii) with lactate were determined with UV-vis and time-resolved laser-induced fluorescence spectroscopy (TRLFS) in a temperature range between 25 and 70 °C. The reaction enthalpy decreased with increasing ionic strength. ATR FT-IR and NMR spectroscopy in combination with density functional theory (DFT) calculations revealed structural details of the Eu(iii) lactate 1 : 1 complex: a chelating coordination mode of the lactate with a monodentate binding carboxylate group and the hydroxyl group being deprotonated.
Basile et al. (Chem. Commun., 2015, 51, 5306–5309) showed that a sodium ion is sandwiched by the uranyl(VI) oxygen atoms of two 3:3 uranyl(VI)–citrate complex molecules in single-crystals. By means...
The aqueous speciation of selenium(iv) was elucidated by a combined approach applying quantum chemical calculations, infrared (IR), Raman, and (77)Se NMR spectroscopy. The dimerization of hydrogen selenite (HSeO3(-)) was confirmed at concentrations above 10 mmol L(-1) by both IR and NMR spectroscopy. Quantum chemical calculations provided the assignment of vibrational bands observed to specific molecular modes of the (HSeO3)2(2-) ion. The results presented will provide a better understanding of the chemistry of aqueous Se(iv) which is of particular interest for processes occurring at mineral/water interfaces.
The interaction between Eu(III) ion and different pH buffers, popular in biology and biochemistry, viz. HEPES, PIPES, MES, MOPS, and TRIS, has been studied by solution nuclear magnetic resonance spectroscopy (NMR) and time-resolved laser-induced fluorescence spectroscopy (TRLFS) techniques. The Good’s buffers reveal non-negligible interaction with Eu(III) as determined from their complex stability constants, where the sites of interaction are the morpholine and piperazine nitrogen atoms, respectively. In contrast, TRIS buffer shows practically no affinity towards Eu(III). Therefore, when investigating lanthanides, TRIS buffer should be preferred over Good’s buffers.
Graphical abstract
The formation equilibria of salicylatoborate, lactatoborate and 3-hydroxybutyratoborate were studied by means of (11)B NMR spectroscopy. The smaller the pKa of the respective organic acid, the higher is the formation constant of the organoborate. The complexation of Eu(III) with salicylatoborate and lactatoborate was investigated by means of TRLFS (time-resolved laser-induced fluorescence spectroscopy) and (11)B NMR spectroscopy, yielding complexation constants lg β₁₁⁰ = 2.6-3.2. A Eu(III)-3-hydroxybutyrate complex was characterized by TRLFS and (1)H NMR spectroscopy (lg β₁₁⁰ = 2.89). DFT calculations of the investigated Eu(III)-organoborates and inorganic Eu(III)-(poly)borates provided information about the Eu(III) coordination (most likely chelate). They support the hypothesis that the complexation of Eu(III) with organic as well as inorganic borate structures containing the binding site "B(OR)4(-)" (R = H, threefold coordinated boron center(s), organic moiety) is comparable.
Glutathione (GSH), a ubiquitous intracellular reducing tripeptide, is able to reduce hexavalent uranium, U(vi), to its tetravalent form, U(iv), in aqueous media in vitro, inducing the formation of nanocrystalline mixed-valence uranium oxide particles. After the initial reduction to U(v) and subsequent dismutation, the yielded U(iv) rapidly hydrolyses under near-neutral conditions forming 2-5 nm sized nanoparticles. The latter further aggregate to 20-40 nm chain-like building blocks that finally arrange as network-like structures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.