Formation of Hydroxide Complexes in the Fe3 +-Cd2 +-NO3 --H2O System

Hydrolysis in the Fe^{3 +}-Cd^{2 +}-NO₃ ^--H₂O system was studied by spectrophotometry, pH-metric titration, dialysis, and sorption techniques. Mutual influence of cations in their hydrolytic and sorption behavior was discussed from the viewpoint of the heteronuclear complex formation.     

Sorption of Cations of the Zn2+-Hg2+-NO3--H2O System by Biomass of Ostreatus Agaricaceae Basidiomycete and KB-4(H+) Cation Exchanger

Sorption of cations of the Zn²⁺-Hg²⁺-NO₃ ^--H₂O system by the biomass of basidiomycete (line 21 Pl. ostreatus f. florida) and by KB-4(H⁺) cation exchanger at pH 1.00 was studied. The results are discussed with regard to the state of cations in the solution before contact with the sorbent, sorbent properties, and sorption behavior of cations.     

Oligomers Intermediates in Between Two New Distinct Homonuclear Uranium(IV) DOTP Complexes**

Two new aqueous U^IV complexes were synthesized by the interaction between the tetravalent uranium cation and the (1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetra(methylene phosphonic acid) (DOTP) macrocyclic ligand. Two distinct homonuclear complexes were identified; the first was characterized by X-ray crystallography as a unique “out-of-cage”, [U(DOTPH₆)₂] complex, in which the U^IV cation is octa-coordinated to 4 phosphonic arms from each ligand in a square anti-prism geometry, with a C₄ symmetry. The second is the “in-cage” [U(DOTPH₄)] complex, in which the tetravalent cation is located between the macrocycle O₄ and N₄ planes. With the help of UV-Vis absorption, ¹H/³¹P NMR, ATR-IR, and MALDI-TOFMS analytical techniques, the chemical interchange between both species is presented. It is shown that the one-way transition is governed by the formation of a multiple number of soluble oligomeric species consisting of varied stoichiometric ratios of both characterized homonuclear complexes.     

Study of the process of the hydroxo complexes formation in the Al3+-Hg2+-NO 3 − -H2O and Al3+-Cd2+-NO 3 − -H2O systems

Russian Journal of Applied Chemistry - The process of hydrolysis in the Al3+-Cd2+-NO 3 ? -H2O and Al3+-Hg2+-NO 3 ? -H2O systems is studie by the methods of pH-metric titration and...     

DOTP versus DOTA as Ligands for Lanthanide Cations: Novel Structurally Characterized CeIV and CeIII Cyclen-Based Complexes and Clusters in Aqueous Solutions

The coordination and redox chemistry of aqueous Ce^IV/III macrocyclic compounds were studied by using the ligands DOTA and DOTP (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra(methylene phosphonic acid), respectively). The hydrolysis tendency of the tetravalent cation in the presence of DOTA is shown to result in the formation of a highly ordered, fluorite-like [Ce^IV₆(O)₄(OH)₄(H₂O)₈(DOTAH)₄] oxo-hydroxo structure both in solution and in the solid state. The lifetime of the analogous species formed in the presence of DOTP was found to be much shorter. Spectroscopic measurements of the latter suggest its similarity to the former. Its gradual decomposition in solution leads to the accumulation of the in-cage complexes [Ce^IVDOTP] and [Ce^IIIDOTP(H₂O)], which were crystallographically characterized in this study. The redox energetics and spectroscopic characteristics for the transition between these two in-cage complexes in aqueous solutions were studied as well. Together with the crystallographic structures of the above-mentioned species, the in-cage [Ce^IVDOTA(H₂O)] complex structure is presented herein for the first time. An elaborative analysis of the X-ray crystallographic structural data obtained for the in-cage complexes studied herein and similar structures published previously suggests that hard-bonding cyclen-derived ligands are, counter-intuitively, better suited for encapsulating, and perhaps kinetically stabilize softer cations than harder ones with DOTP, marked as a possible adequate chelator for the study of the aqueous properties of Ln^II and Ac^III cations.     

Hydroxo Complex Formation in the Fe3+-Hg2+-NO3 --H2O System

Hydrolysis of the Fe³⁺-Hg²⁺-NO₃ ^--H₂O system was studied by spectrophotometry, pH-metric titration, and sorption methods. The mutual influence of the cations on the hydrolytic and sorption behavior was discussed in terms of heteronuclear complex formation.     

On the Aqueous Chemistry of the UIV–DOTA Complex

The 1,4,7,10-tetrazacyclodecane-1,4,7,10-tetraacetic acid (DOTA) aqueous complex of U^IV with H₂O, OH⁻, and F⁻ as axial ligands was studied by using UV/Vis spectrophotometry, ESI-MS, NMR spectroscopy, X-ray crystallography, and electrochemistry. The U^IV–DOTA complex with either water or fluoride as axial ligands was found to be inert to oxidation by molecular oxygen, whereas the complex with hydroxide as an axial ligand slowly hydrolyzed and was oxidized by dioxygen to a diuranate precipitate. The combined data set acquired shows that, although axial substitution of fluoride and hydroxide ligands instead of water does not seem to significantly change the aqueous DOTA complex structure, it has an important effect on the electronic configuration of the complex. The U^IV/U^III redox couple was found to be quasi-reversible for the complex with both axially bonded H₂O and hydroxide, but irreversible for the complex with axially bonded fluoride. Intriguingly, binding of the axial fluoride renders the irreversible one-electron U^V/U^IV oxidation of the [U^IV(DOTA)(H₂O)] complex quasi-reversible, which suggests the formation of the short-lived pentavalent form of the complex, an aqueous non-uranyl chelated U^V cation.     

Conditions for the Chemical Precipitation of the Starting Substances from Solutions for the Synthesis of Aluminospinels

The precipitation of hydroxides from the Mg^{2 +}-Al^{3 +}-An^--H₂O system (An = NO₃ ^-, Cl^-, SO₄ ^{2 -}) at the initial spinel molar ratio Mg^{2 +} : Al^{3 +} = 1 : 2 was studied. The optimal conditions were found for obtaining the precipitates exhibiting the best properties in the manufacturing sense; their subsequent heat treatment yields a single phase of aluminomagnesium spinel.