铝(Ⅲ)与脱铁伴清蛋白结合的紫外差光谱研究

在 pH7.4、 0.1mol· L~(－1)N-2-羟乙基哌嗪- N′-2-乙磺酸（ Hepes）及室温条件下,使用紫外吸收差光谱进行了铝(Ⅲ)对脱铁伴清蛋白的滴定。结果表明铝(Ⅲ)与脱铁伴清蛋白结合后其紫外差光谱在 238nm和 291nm处出现吸收峰。在 238nm处铝(Ⅲ)-脱铁伴清蛋白配合物的摩尔吸光系数是 (1.52± 0.04)× 10~4cm~(－1)· mol~(－1)· L。铝(Ⅲ)可占据脱铁伴清蛋白的两个金属离子结合部位,条件稳定常数是 lgK_N=11.21± 0.12,lgKC=9.53± 0.24。 N-端单铁伴清蛋白的紫外差光谱滴定表明,铝 ?优先占据脱铁伴清蛋白的 N端结合部位。     

A Bis(p-tert-butyloctahomotetraoxacalix[8]arene) Capsule with [(UO2)2(OH)2] Links and a Disordered [Rb4(H2O)4] Inner Core

p-tert-Butyloctahomotetraoxacalix[8]arene (LH⁸) reacts with uranyl nitrate hexahydrate in the presence of rubidium hydroxide to give a mixed complex that can be viewed as a tetrauranate dimer [(UO²)⁴(LH⁴)²(OH)⁴] containing four disordered rubidium ions and water molecules. Two uranyl ions are complexed in an “external” fashion by each macrocycle, each of them bound to two phenoxide groups and one ether group, as well as to two bridging hydroxide ions. The latter ensure the formation of a dimeric capsule that contains the disordered set of alkali metal ions. Apart from water molecules, the Rb⁺ ions are bound to the uranyl oxo groups directed towards the inner cavity, and to phenol and ether oxygen atoms from the macrocycle. The resulting octanuclear complex presents an unprecedented geometry evidencing the assembling potential of uranyl ions.

p-tert-Butyloctahomotetraoxacalix[8]arene (LH₈) reacts with uranyl nitrate hexahydrate in the presence of rubidium hydroxide to give a mixed complex that can be viewed as a tetrauranate dimer [(UO₂)₄(LH₄)₂(OH)₄] containing four disordered rubidium ions and water molecules. Two uranyl ions are complexed in an “external” fashion by each macrocycle, each of them bound to two phenoxide groups and one ether group, as well as to two bridging hydroxide ions. The latter ensure the formation of a dimeric capsule that contains the disordered set of alkali metal ions. Apart from water molecules, the Rb^+| ions are bound to the uranyl oxo groups directed towards the inner cavity, and to phenol and ether oxygen atoms from the macrocycle. The resulting octanuclear complex presents an unprecedented geometry evidencing the assembling potential of uranyl ions.     

Etude des complexes sulfosalicylate de cuivre(III), nickel(II), cobalt(II) et uranyle(II) a l'aide d'une resine echangeuse de cations: Study of the sulphosalicylate complexes ofcopper(II), nickel(II), cobalt(II) and uranyl(II) by means of cation-exchange resins.

Study of the sulphosalicylate complexes of copper(II), nickel(II), cobalt(II) and uranyl(II) by means of cation-exchange resins.The conditional stability constants of the 1:1 complexes of the sulphosalicylate ions (L^3-) with copper(II), nickel(II), cobalt(II) and uranyl ions have been determined in a sodium perchlorate solution (0.1 M) and at various pH values by a cation-exchange method based on Schubert's procedure. The limits of application of the method are discussed. The variation with pH of the conditional stability constants can be explained by the existence of the complexes: CuH₂L, CuHL, CuL^-; NiH₂L⁺, NiHL, NiL^-; CoHL, CoL^-; UO₂H₂L⁺, UO₂HL, UO₂L^-, UO₂LOH^2-. The stability constants of these complexes are reported. Distribution diagrams of the various complexes of each element with pH and total concentration of sulphosalicylate parameters are given.     

Complex formation of uranyl ions with polyaminopolycarboxylic acids

The complex formation of uranyl ions with ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid and triethylenetetraminehexaacetic acid has been studied by pH titrations, with computer evaluation of the titration data. For each ligand, the formation constants of a series of mono- and di-nuclear complexes were determined in 0.1 M KNO₃ at 25.0°C. The hydrolysis constants for uranyl ions and the dissociation constants of the ligands were also calculated. A novel approach was used to obtain realistic estimates of the uncertainties in the respective constants. Certain likely structures of the complexes are suggested.     

Factors affecting the complexation of polyacrylic acid with uranyl ions in aqueous solutions: A luminescence study

A study was carried out in aqueous solutions using luminescence technique to investigate the effects of pH, salt concentration, and temperature on the polyacrylic acid/uranyl ion (PAA/UO) complex formation as well as competitive phenomena of enhancement and quenching effects on photoexcited state of uranyl ions. It was found that excess of H⁺ and OH^? is not favorable for complexation between uranyl ions and polymer. Added nitrate salts of Na⁺ and K⁺ had significant enhancement effect on emission spectra of PAA/UO complex. These results indicated that the metal ion/polymer chain complex collapsed by addition of salts and then complex became more compact with consequent phase separation. No significant effect of temperature on the PAA/UO complex stability has been observed between 25–50 °C. The quenching rate constants obtained from Stern–Volmer plots were found to be in the order of k_q(H⁺) >> k_q(K⁺) > k_q(Na⁺). © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2737–2744, 2005     

配位体SO2-4对激发态铀(VI)去活化的影响

The dependence of the luminescence decay of electronically excited uranyl ions on the concentrations of uranium and sulphate in aqueous solution has been investigated with a pulsed nitrogen laser as a light source and a programmable transient recorder for lifetime measurements. Single exponential decay of the Luminescence is observed. The deactivation process of the excited uranyl ions should include radiative, nonradiative, water quenching and uranium self quenching and the measured lumine-scenec lifetime inidcates the result of all these processes. The Luminescence lifetime of uranyl ions increases with increasing concentration of sulphate and becomes constant when the equilibrium concentration of sulphate reaches 3.0 mol·L~(-1). The dependence of the Luminesence lifetime is similar to that of the UO_2(SO_4)_3~(4-) formation. This phenomenon can be interpreted in terms of the fact that in aqueous solution uranyl ions exist as aquo-uranyl ions. As the concentration of sulphte increaes the water molecule of hydrated uranyl ions will be replaced by sulphate ions via complex formation, and the quenching of excited uranyl ions by water is reduced. The self quenccing and the water quenching rate constants of UO_2(H_2O)_6~(2+) and UO_2(SO_4)_3~(4-) are estimated. Based on the experimental results a model for the deactivation mechanism of excited uranyl ions in sulphate solution is proposed.     

Complexation of poly(acrylic acid)s with uranyl ion

The complexation of uranyl ion (UO₂²⁺) in aqueous solution with polymers containing carboxylic acid groups was studied potentiometrically. Overall formation constants of the uranyl complexes with poly(methacrylic acid) and crosslinked poly(acrylic acid) were much larger than those with the corresponding low molecular carboxylic acids. Decrease in the viscosity of the polymer solution on adding uranyl ion indicated that poly(acrylic acid) forms intra-polymer chelates with uranyl ion. The crosslinked poly(acrylic acid) adsorbed uranyl ions at higher efficiency than transition metal ions.     

The Unusual Thermodynamic Stability Order of the First-series Transition Metal Complexes with N,N,N′-tri(2-pyridylmethyl)glycinamide and the Crystal Structure of the Nickel(II) Complex

A new pentadentate tripodal peptide ligand N,N,N′-tri(2-pyridylmethyl)glycinamide (L) has been synthesized. The crystal structure of its nickel(II) complex, [NiL(H₂O)] · 1.17ClO₄ · 0.17H₃O · 0.03H₂O (1), has been determined by X-ray diffraction. In the complex, the deprotonated ligand L acts in a pentadentate fashion and coordinates to the nickel(II) ion through five nitrogen atoms, while the sixth position is occupied by a water molecule. The units of the complex are connected as a 3D honeycomb network by intermolecular hydrogen bonds. The thermodynamic properties of the ligand L with the first-series transition metal ions Co(II), Ni(II), Cu(II) and Zn(II) have been investigated by potentiometric titration and the results show that the order of their stability constants does not conform to the Irving–Williams serial. The reason why the stability constants of the Cu(II) complex are unconventionally small is proposed.     

Reaction of uranyl nitrate with carboxylic diacids under hydrothermal conditions. Crystal structure of complexes with l(+)-tartaric and oxalic acids

l(+)-tartaric acid reacts with uranyl nitrate in the presence of KOH, under mild hydrothermal conditions, to give the complex [UO₂(C₄H₄O₆)(H₂O)] (1), the first uranyl tartrate to be crystallographically characterized. Each tartrate ligand bridges three uranyl ions, one of them in chelating fashion through proximal carboxylate and hydroxyl groups. The resulting assemblage is two-dimensional, with the uranyl pentagonal bipyramidal coordination polyhedra separated from one another. Prolonged heating of an uranyl tartrate solution resulted in oxidative cleavage of the acid and formation of the oxalate complex [(UO₂)₂(C₂O₄)₂(OH)Na(H₂O)₂] (2). The bis-bidentate oxalate and bridging hydroxide groups ensure the formation of sheets with corner-sharing uranyl pentagonal bipyramidal coordination polyhedra, in which six-membered metallacycles encompass the sodium ions. These sheets are assembled into a three-dimensional framework through further oxo-bonding of the sodium ions.     

The determination of the stability constants of uranyl and thorium with aminopolycarboxylic acids

The stability of uranyl and thorium ions with ligands N-(2′-carboxy phenyl) iminodiacetic acid (ADA), iminodiacetic acid (IDA) and [(ethylenedioxy)diethylenedinitrilo]tetraacetic acid (EGRA) have been studied using the potentiometric technique in 0.1M, KNO₃ solution at 25°C. The complexes of thorium (IV) ions with IDA and ADA are shown to be more stable than those for uranyl ions, while EGTA forms more stable complexes with uranyl ion.     

Nitrate ion transport across TBP-kerosene oil supported liquid membranes coupled with uranyl ions

The role of nitrate ions in uranyl ions transport across TBP-kerosene oil supported liquid membranes (SLM) at varied concentrations of HNO₃ and NaNO₃ has been studied. It has been found that nitrate ions move faster compared to uranyl ions at the uranium feed solution concentrations studied. The nitrate to uranyl ions flux ratio vary from 355 to 2636 under different chemical conditions. At low uranium concentration the nitrate ions transport as HNO₃ · TBP, in addition to as UO₂(NO₃)₂ · 2TBP type complex species. The flux of nitrate ions is of the order of 12.10 · 10^–3 mol · m^–2 · s^–1 compared to that of uranium ions (4.56 · 10^–6 mol · m^–2 · s^–1). The permeability coefficient of the membrane for nitrate ions varies with chemical composition of the feed solution and is in the order of 2.5 · 10^–10 m^–2 · s^–1. The data is useful to estimate the nitrate ions required to move a given amount of uranyl ions across such an SLM and in simple solvent extraction.     

Mixed complexes of alkaline earth uranyl carbonates: a laser-induced time-resolved fluorescence spectroscopic study

The interaction of the alkaline earth ions Mg(2+), Sr(2+) and Ba(2+) with the uranyl tricarbonato complex has been studied by time-resolved laser-induced fluorescence spectroscopy. In contrast to the non-luminescent uranyl tricarbonato complex at ambient temperature the formed products show luminescence properties. These have been used to determine the stoichiometry and complex stabilities of the formed compounds. As the alkaline earth elements are located in an outer shell of the complex the influence of the type of the alkaline earth element on the stability constant is not very drastic. The stability constants range from logbeta(113) degrees =26.07+/-0.13 to logbeta(113) degrees =26.93+/-0.25 for the first reaction step and from logbeta(213) degrees =29.73+/-0.47 to logbeta(213) degrees =30.79+/-0.29 for the overall complex formation with two alkaline earth ions.     

Complexes of organolead and organotin ions with 1-(2-pyridylazo)-2-naphthol

The stability constants of the complexes of 1-(2-pyridylazo)-2-naphthol with several organotin and lead ions were determined spectrophotometrically in aqueous 20% (v/v) dioxane and were shown to have very high values. The extraction of the complex of (C₂H₅)₂Pb²⁺ from water into chloroform was studied, and the formation of an extractable (C₂H₅)₂Pb(PAN)(OH) complex is postulated.     

A Method for the polarographic determination of the stability constants of mixed complexes

A new method for determining the stability constants of mixed complexes is proposed which is especially appropriate when only the mixed complex 1:1:1 is formed. In order to verify this method, the coordinate system Pb(II)-SCN^?-NO^?₃ has been studied polarographically in aqueous medium of a constant ionic strength of μ = 1.0 M. Using our knowledge of the stability constants of simple complexes and applying this method we obtain β₁₁ = 8 for the mixed complex.     

Thermodynamic studies of sitting-atop (SAT) complexation of uranyl and free base meso -tetraarylporphyrins

The interaction of uranyl with meso-tetraphenylporphyrin and its para-substituted derivatives (H₂t(4-X)pp, X : H, Br, Cl, CH(CH₃)₂, OCH₃, CH₃) in chloroform produced 1 : 1 sitting-atop (SAT) complexes ((uranyl)H₂t(4-X)pp). Formation constants were calculated by computer fitting of complex absorbance versus mole ratio data to appropriate equations and found to decrease with temperature increase. Thermodynamic parameters, ΔG ⁰, ΔH ⁰ and ΔS ⁰ were obtained. The formation constants vary with changing of the substituent on the aryl rings of H₂t(4-X)pp in the following order: (uranyl)H₂t(4-OCH₃)pp?>?(uranyl)H₂t(4-CH₃)pp?>?(uranyl)H₂t(4-CH(CH₃)₂)pp?>?(uranyl)H₂tpp?>?(uranyl)H₂t(4-Br)pp?>?(uranyl)H₂t(4-Cl)pp.     

Crystal structures of the dicyclohexyl-(18-crown-6) uranyl perchlorate complex and of its hydrolysis product

The structures of dicyclohexyl-(18-crown-6) uranyl perchlorate, [(C₂₀H₃₆O₆)UO₂] (ClO₄)₂ (complex I) and of dicyclohexyl-(18-crown-6) uranyl hydroxyperchlorate [C₂₀H₃₆O₆]₃ [(UO₂)₂(H₂O)₆] · (ClO₄)₂, CH₃CN, (complex II) have been determined from three dimension X-ray diffraction data.The uranyl group is directly coordinated to the oxygen atoms of the polyether ring in complex I; its hydrolysis (complex II) leads to a dimerization of the uranyl ions by sharing two OH groups with an U-U distance of only 3.827(8) Å. The polyether molecules are connected by hydrogen bonds with the dimeric ion [(UO₂)₂ (OH)₂ (H₂O)₆]²⁺.     

Dihydro[2.2.2]cryptand di‐μ‐hydroxo‐bis[bis(nitrato‐κ2O,O′)dioxouranium(VI)] monohydrate

In the title dinuclear uranyl complex, (C₁₈H₃₈N₂O₆)[(UO₂)₂(NO₃)₄(OH)₂]·H₂O, each pair of uranyl ions in the two independent centrosymmetric dianionic dimers is bridged by the two hydroxide ions, with the nitrate ions ensuring equatorial hexagonal coordination. The di­hydro[2.2.2]­cryptand (4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]­hexa­cosane) dication presents an `in–in' conformation (endo protonation) and it is hydrogen bonded to the hydroxide ions, either directly or via a water mol­ecule, resulting in the formation of linear hydrogen‐bonded polymers.     

Donnan Exclusion Chromatography Application to Complex Formation Studies

Abstract

A new method for the evaluation of stability constants of complex species has been proposed, based on the principle of Donnan exclusion chromatography. The stability constants for trimetaphosphate complexes of magnesium and calcium ions have been evaluated to be log β₁ = 1.50 and 1.64 (I=1.00, 25° ± 2°C), respectively.     

The thermodynamic characteristics of formation of nickel(II) complexes with L-tyrosine in aqueous-ethanolic solvents

Acid dissociation constants of L-tyrosine (H₂Tyr) and the constants of complex formation between L-tyrosine and nickel(II) ions in water-ethanol mixtures were determined potentiometrically. The Gibbs energies of transfer of tyrosine, HTyr⁻ tyrosinate anion, and [NiHTyr]⁺ complex from water into binary solvents were calculated. An increase in the stability constants of the [NiHTyr]⁺ and [Ni(HTyr)₂] complexes in solvents with a high content of ethanol was caused by weakening of the solvation of amino ligand donor groups.     

Quinalizarin anchored on Amberlite XAD-2. A new matrix for solid-phase extraction of metal ions for flame atomic absorption spectrometric determination

Amberlite XAD-2 has been functionalized by coupling it to quinalizarin [1,2,5,8-tetrahydroxyanthraquinone] by means of an -N = N- spacer. Elemental analysis, thermogravimetric analysis, and infrared spectra were used to characterize the resulting new polymer matrix. The matrix has been used to preconcentrate Cu(II), Cd(II), Co(II), Pb(II), Zn(II), and Mn(II) before their determination by flame atomic absorption spectrometry (FAAS). UO₂(II) has been preconcentrated for fluorimetric determination. The optimum pH values for maximum adsorption of the metals are between 5.0 and 7.0. All these metal ions are desorbed (recovery 91–99%) with 4 mol L^–1 HNO₃. The adsorptive capacity of the resin was found to be in the range 0.94–5.28 mg metal g^–1 resin and loading half-life (t_1/2) between 5.3 and 15.0 min. The effects of NaF, NaCl, NaNO₃, Na₂SO₄, Na₃PO₄, Ca(II), and Mg(II) on the adsorption of these metal ions (0.2 μg mL^–1) are reported. The lower limits of detection for these metal ions are between 1 and 15.0 μg L^–1. After enrichment on this matrix flame AAS has been used to determine these metal ions (except the uranyl ion) in river water samples (RSD ≤ 6.5%); fluorimetry was used to determine uranyl ion in well water samples (RSD ≤ 6.3%). Cobalt from pharmaceutical vitamin tablets was preconcentrated by use of this chelating resin and estimated by FAAS (RSD ～ 4%).