Complexation of Sc(III), Ga(III), In(III) and Ln(III) with Eriochrome Red B

Cyclic linear-sweep voltammetry was used to study the complexation of Sc(III), Ga(III), In(III) and Ln(III) with eriochrome red B (ERB). It was established that all metal ions investigated form complex compounds with azodye having a mole ratio, M(III):ERB = 1:2. The hydroxo forms of M(III) ions, which take part in interaction with ERB, were determined by the Nazarenko method. The stability constants for the formation of these chelates are nearly the same. It was shown that the reduction of the ligand in the complex does not only depend on the peculiarities of complexation, but the processes occurring in pre-electrode layer also influence it.     

Interaction of Chromium(III) with Chrome Azurol S in Water–Glycerol Media

The interaction of Cr(III) with Chrome azurol S (CAS) in water–glycerol binary mixtures has been investigated by spectrophotometry. The absorption electronic spectra of Chrome azurol S and its complex with Cr(III) in water–glycerol media with glycerol contents from 10 to 50% by vol. have been measured. The stability constant of the complex in water–glycerol binary mixtures has been determined. It has been shown that the rate of reaction increases as the organic solvent content increases.     

Complexation of Eu(III), Am(III) and Cm(III) with Dicarboxylates: Thermodynamics and Structural Aspects of the Binary and Ternary Complexes

The complexation of Eu(III), Am(III) and Cm(III) with dicarboxylate anions with O, N or S donor groups was measured in I=6.60 mol⋅kg⁻¹ (NaClO₄) at temperatures of 0–60 °C by potentiometry and solvent extraction. The complexation thermodynamics of these complexes show that their stability is due to highly favorable complexation entropies because the complexation enthalpies are endothermic. Luminescence studies with Eu(III) and Cm(III) were used to measure the hydration numbers of the complexes. NMR spectra of ¹H and ¹³C were used to determine the binding modes of La(III) with the ligands. The formation of 1:1:1 ternary complexes of M(EDTA)⁻ with the dicarboxylate ligands was studied to determine changes in coordination of the metal cation with formation of the ternary species. The complexation of ternary complexes changes from bidentate to monodentate as the chain length between the binding sites of the dicarboxylates increases from 1 (malonate) to 4 (adipate). DFT computations were used to confirm the structural aspects of the interaction of these complexes.     

Crystal Structure and Spectroscopic Analysis of Polypyridyl Quinoxaline with Ce(Ⅲ) and Nd(Ⅲ)

Two high coordination crystals were obtained by the interaction of Ce~(3+) and Nd~(3+) with polypyridyl quinoxaline ligand 2,3,6,7,10,11-hexakis(2-pyridyl)dipyrazino[2,3-f:20,30-h]quinoxaline(HPDQ), and they were characterized. Complex 1 exhibits a 0 dimensional three-nuclear structure, with the three Ce(Ⅲ) atoms being ten-, eleven- and twelve-coordinated. Complex 2 is a 0 dimensional dual-core structure and the Nd(Ⅲ) atom is ten-coordinated. Complex 1 is of monoclinic system, space group P2/c with a = 16.850(3), b = 16.617(3), c = 24.017(5) ?, β = 100.94(3)o, V = 6602(2) ?~3, Z = 4, S = 1.062, F(000) = 3372, R = 0.0504 and wR = 0.1463(I 2σ(I)). Complex 2 adopts a monoclinic system, space group C2/c with a = 25.795(5), b = 20.166(4), c = 13.059(3) ?, β = 112.29(3)°, V = 6286(2) ?~3, Z = 4, S = 1.004, F(000) = 2664, R = 0.0663 and wR = 0.1821(I 2σ(I)). Furthermore, the behaviors of HPDQ with Ce~(3+) and Nd~(3+) in the solution are also investigated. After the Ce~(3+) is added, the ultraviolet absorption of the solution is enhanced with a red shift compared with that of the HPDQ ligand. While after adding Nd~(3+), the ultraviolet absorption of the solution is weakened, and it has a red shift which is the same as Ce~(3+). However, after the respective addition of metal ions, the emission of all solutions is quenched and has a red shift compared with that of the HPDQ ligand.     

The Study on the Stability Constant and Species Distribution of Eu (III) and Tb (III) Complexes with BDBPH

Biomimetic hydrolysis of DNA or RNA is of increasing importance in biotechnology and medicine. The ability to cleave nucleic acids efficiently, in a non-degradative manner, and with high levels of selectivity for site or structure will be required by many applications for the manipulation of genes, the design of structural probes and the development of novel therapeutics1. There has been much interest in the development of lanthanide complexes as nucleic acid cleavage agents. It has been fou…     

Thermodynamic Features of the Complexation of Neodymium(III) and Americium(III) by Lactate in Trifluoromethanesulfonate Media

The protonation of lactate has been studied in a variety of electrolyte solutions using microcalorimetry to reveal a distinct medium influence imposed on the thermochemistry of the equilibrium. The thermochemistry of lactate protonation, when studied directly in 1.0 mol⋅L⁻¹ sodium lactate, agreed well with the studies performed in trifluoromethanesulfonate (triflate). This thermodynamic agreement suggests that the physical chemistry of lactate in the solutions applicable to the TALSPEAK process—a solvent extraction method for separating trivalent actinides from trivalent lanthanides within the scope of used nuclear fuel processing efforts—may be simulated in triflate solutions. Potentiometry, spectrophotometry and microcalorimetry have been subsequently used to study the thermodynamic features of neodymium and americium complexation by lactate using triflate as a strong background electrolyte. Three successive mononuclear lactate complexes were identified for Nd(III) and Am(III). The stability constants for neodymium, β ₁₀₁=2.60±0.01, β ₁₀₂=4.66±0.02 and β ₁₀₃=5.6±0.1, and for americium, β ₁₀₁=2.60±0.06, β ₁₀₂=4.7±0.1 and β ₁₀₃=6.2±0.2, were found to closely agree with the thermodynamic studies reported in sodium perchlorate solutions. Consequently, the thermodynamic medium effect, imposed on the TALSPEAK-related solution equilibria by the presence of strong background electrolytes such as NaClO₄ and NaNO₃, does not significantly impact the speciation in solution.     

Extraction chromatographic study of aluminium(III) and mutual separation of aluminium(III), gallium(III), indium(III) and thallium(III) with N-n-octylaniline

A selective method has been developed for extraction chromatographic studies of aluminium(III) and its separation from several metal ions with a chromatographic column containing N-n-octylaniline (liquid anion exchanger) coated on silanized silica gel as a stationary phase. The aluminium(III) was quantitatively extracted with the 0.065 mol/L N-n-octylaninine from 0.013 to 0.05 mol/L sodium succinate at a flow rate of 1.0 mL/min. The extracted metal ion has been recovered by eluting with 25.0 mL of 0.05 mol/L hydrochloric acid and estimated spectrophotometrically with aurintricarboxylic acid. The effects of the acid concentration, the reagent concentration, the flow rate and the eluting agents have been investigated. The log-log plots of distribution coefficient (KdAl(III)) versus N-n-octylaniline concentrationin 0.005 and 0.007 mol/L sodium succinate gave theslopes 0.5 and 0.7 respectively and showed theprobable composition of theextracted species was 1:1 (metal to amine ratio) and the nature of extracted species is [RR''NH2+ Al succinate2-] org. .The extraction of aluminium(III) was carried out in the presence of various ions to ascertain the tolerance limit of individual ions. Aluminium(III) has been separated from multicomponent mixtures, pharmaceutical samples and synthetic mixtures corresponding to alloys. A scheme for mutual separation of aluminium(III), indium(III), gallium(III) and thallium(III) has been developed by using suitable masking agents. The method is fast, accurate and precise.     

The Molecular Basis of the Interaction of Cyclophilin A with α-Synuclein

Peptidylprolyl isomerases (PPIases) catalyze cis/trans isomerization of prolines. The PPIase CypA colocalizes with the Parkinson's disease (PD)-associated protein α-synuclein in cells and interacts with α-synuclein oligomers. Herein, we describe atomic insights into the molecular details of the α-synuclein/CypA interaction. NMR spectroscopy shows that CypA catalyzes isomerization of proline 128 in the C-terminal domain of α-synuclein. Strikingly, we reveal a second CypA-binding site formed by the hydrophobic sequence ⁴⁷GVVHGVATVA⁵⁶, termed PreNAC. The 1.38 Å crystal structure of the CypA/PreNAC complex displays a contact between alanine 53 of α-synuclein and glutamine 111 in the catalytic pocket of CypA. Mutation of alanine 53 to glutamate, as found in patients with early-onset PD, weakens the interaction of α-synuclein with CypA. Our study provides high-resolution insights into the structure of the PD-associated protein α-synuclein in complex with the most abundant cellular cyclophilin.     

The reactions of phosphorus(III) halides with β-diketiminato ligands

Reactions of the lithium or sodium salt, [HC(CMeNDipp)₂]M (Dipp = 2,6-diisopropylbenzene, M = Li or Na), with PBr₃ or PCl₃ affords a series of phosphenium cations that were characterized in the solid state by X-ray crystallography. Solid-state analysis reveals that for compounds 1 and 2, C–H activation of the ligand occurs and the phosphorus is bound to a nitrogen and carbon atom of the ligand. Compound 3 exhibits the more traditional nitrogen chelation of the ligand to the phosphorus atom.     

Synthesis and Magnetic Properties of Fe(II) and Nd(III) Complexes of Poly(N-2-thiazolylacrylamide)

In recent years,the organic ferromagnets have drawn growing attention due to their characteristics of structural diversities,low density,and readily processing1-3.Design and synthesis of magnetic polymers are one of great challenges in today′s magnetic material research,and some significant achievements have been made in this field4,5.In this article,we describe the synthesis of acrylamide-type polymer with pendent thiazolyl groups(Scheme1).The as-prepared polymer exhibited better solubility …     

Stability Constants and Spectroscopic Properties of Thorium(IV)–Arsenazo III Complexes in Aqueous Hydrochloric Medium

The complexation characteristics of thorium–arsenazo III in the range of 1–6 mol·L^?1 hydrochloric acid media were investigated by UV–Vis absorption spectroscopy and computational analysis. The chemical equilibrium model of thorium–arsenazo III complexation was established including the species distribution of arsenazo III, the formation of thorium chloride species, and the release of protons from thorium–arsenazo III complexes. In the spectra of thorium–arsenazo III complexes, two characteristic absorption peaks were observed at 610 and 660 nm, and the latter peak showed a tendency to shift about 4 nm to higher wavelength as the acidity of the hydrochloric acid media increased from 1 to 6 mol·L^?1. Analysis of the experimental data indicates that the molar absorptivities of both 1:1 and 1:2 complexes (thorium to arsenazo III) steadily increase as the acidity of medium increases. The determined stability constants of 1:1 and 1:2 complexes at various concentrations of hydrochloric acid were extrapolated to zero ionic strength, based on the specific ion interaction theory (SIT) approach. The limiting stability constants were determined to be \( { \log }_{10} \beta_{11}^{\text{o}} \) = 8.56 ± 0.13 and \( {\log}_{10} \beta_{12}^{\text{o}} \) = 15.17 ± 0.18 with ion interaction coefficients of Δε ₁₁ = –0.57 ± 0.02 kg·mol^?1 and Δε ₁₂ = –0.60 ± 0.04 kg·mol^?1, respectively.     

The infrared spectra of complexes with planar dithiooxamides—III. The Ni(II) polymeric complexes

Thermal analysis, u.v. spectra and i.r. spectra are given for some nickel complexes and their isotopes of planar dithiooxamides, the results are explained by assuming planar and octahedral S,N conformations about the nickel atoms in a polymeric structure.     

Solvatochromism and piezochromism of pentacyanoferrates(II) and of mixed valence iron(II)—iron(III) and ruthenium(II)—ruthenium(III) species

Pressure effects on the MLCT bands of the pyrazine- and 4-cyanopyridine-pentacyanoferrate(II) anions have been established. The relation of these piezochromic effects to the solvatochromism of each complex is put into the correlation between these parameters developed for other d⁶ ternary complexes. The conformance of piezochromic and solvatochromic efrects on MMCT bands for diiron and diruthenium mixed valence complexes to this correlation is examined.     

Densities and Viscosities of Tris(acetylacetonato)cobalt(III) Complex Solutions in Various Solvents

The densities and the viscosities of tris(acetylacetonato)cobalt(III) solutions in acetonitrile, dichloromethane, chloroform, tetrachloromethane, benzene, toluene, ethylbenzene, and p-xylene were measured in the dilute concentration regions at several temperatures ranging from 278 to 313 K under ambient pressure. The partial molar volumes of the solvents and solute were calculated. They are independent of concentration and increase slightly as the temperature increases. The viscosity A- and B-coefficients of the Jones-Dole equation were obtained. The A-coefficients were found to be zero within experimental error. The B-coefficients are positive and decrease as the temperature increases. Thermodynamic quantities of activation for viscous flow were calculated on the basis of Eyring’s viscosity equation. From the quantities obtained in this study, along with some information from the literature, it is suggested that structure-making interactions occur between the segments of the complex and the solvent molecules. These interactions include electrostatic interactions between the local charge on the complex and the dipole moment of the solvent in solutions of acetonitrile and dichloromethane, interlocking packing interactions along C ₃-axis of the complex with solvent in solutions of chloroform and tetrachloromethane, and π-electron interactions between the chelate ring of the complex and the solvent in solutions of benzene, toluene, ethylbenzene, and p-xylene.     

Exploring the reactions of β-amyloid (Aβ) peptide 1-28 with Al(III) and Fe(III) ions

The reactions of human β-amyloid peptide 1-28 (Aβ28) with Al(III) and Fe(III) ions were investigated by (1)H NMR and electrospray ionization mass spectrometry (ESI-MS) under pH conditions close to physiological ones. (1)H NMR titrations, performed in the 5.3-8.0 pH range, revealed that no measurable amounts of Aβ28-Al(III) or Aβ28-Fe(III) adducts are formed; such metal adducts could not be obtained even by changing a number of experimental conditions, e.g., temperature, buffer, nature of the salt, etc. These observations were later confirmed by ESI-MS. It is thus demonstrated that Aβ28, at physiological pH, is not able to form binary complexes with Al(III) and Fe(III) ions of sufficient stability to compete with metal hydroxide precipitation. The biological implications of these findings are discussed in the frame of current literature.     

Interaction of Fe(III) with herbicide-carboxylato ligands – Di-, tri- and tetra-nuclear compounds: Structure and magnetic behavior

The iron complexes with the phenoxyalkanoic acids 3,4-D, 2,3-D and 2,4,5-T in the presence or not of a nitrogen donor heterocyclic ligand, phen, were prepared and characterized. Interaction of Fe(III) with phenoxyalkanoic acids and phen leads to dinuclear neutral complexes while the absence of phen favours trinuclear cationic or tetranuclear neutral forms. The crystal structure of hexakis(2,3-dichlorophenoxyacetato)tris(methanol)oxotri-iron(III) chloride–methanol(1/3), [Fe₃O(2,3-D)₆(MeOH)₃]Cl · 3MeOH (2), and tetrakis(dimethyl-sulfoxide)octakis(2,4,5-trichlorophenoxyacetato)dioxotetra-iron(III) methanol(1/2)–water(1/1)–dimethylsulfoxide(1/0.8), {[Fe₄O₂(2,4,5-T)₈(dmso)₄] · 2MeOH · H₂O · 0.8dmso} (3), have been determined and refined by least-squares methods using three-dimensional Mo Kα data.     

Interaction of Poly(vinyl alcohol) with Poly(acrylic acid) and with Sodium Polyacrylate in Aqueous Solutions: A Volumetric Study at 25 °C

The infinite dilution partial molar volumes $\bar{V}^{\infty}$ of poly(acrylic acid), at different degrees of neutralization α _N with sodium hydroxide, have been experimentally determined in aqueous solutions. Analysis of the data indicates that, to a good approximation, the observed decrease of $\bar{V}^{\infty}$ with α _N can be interpreted in terms of the electrostriction of the water molecules involved in the hydration cospheres of the –RCOO^? groups. The presence of PVA does not significantly affect the value of $\bar{V}^{\infty}$ for the undissociated acid, but causes a large decrease for the sodium salt. This aspect has been discussed in terms of direct interaction between the two polymers.     

Synthesis,crystal structure and other properties of the complexes of Er(III), Yb(III) and Lu(III) with 4,4′-bipyridine and dichloroacetates

A novel mixed-ligand complexes of Er(III), Yb(III) and Lu(III) with title ligands were prepared and characterized by chemical and elemental analysis and IR spectroscopy, conductivity (in methanol, dimethyloformamide and dimethylsulphoxide). The thermal properties of complexes in the solid state were studied. The mode of metal–ligand coordination was discussed. The title compounds are isomorphic and isostructural in solid state. All atoms in studied compounds lie in general positions but occurrence of inversion on the midpoint of the bond linking two pyridine rings leads to existence in asymmetric unit one complex molecule and half of outer coordination sphere 4-bpy molecule. All chelating carboxylate groups are symmetrically bonded to the metal cations. The molecules of studied compounds are connected to the three dimensional network via O–H···O and O–H···N intermolecular hydrogen bonds. In the structures also exist C–H···O, C–H···Cl weak hydrogen bonds and π····π stacking interactions.     

Speciation of the Vanadium(III) Complexes with 1,10-Phenanthroline, 2,2′-Bipyridine,and 8-Hydroxyquinoline

The complex species formed between vanadium(III) and 1,10-phenanthroline (phen), 2,2′-bipyridine (bipy), and 8-hydroxyquinoline (8hq) were studied in aqueous solution by means of electromotive forces measurements, emf(H), at 25 °C with 3.0 mol⋅dm⁻³ KCl as the ionic medium. The potentiometric data were analyzed using the least-squares computational program LETAGROP, taking into account the hydrolytic vanadium(III) species formed in solution. Analysis of the vanadium(III)–phen system data shows the formation of [VHL]⁴⁺, [V(OH)L]²⁺, [V₂OL₂]⁴⁺ and [V₂OL₄]⁴⁺ complexes. In the vanadium(III)–bipy system the [VHL]⁴⁺, [V(OH)L]²⁺, [V₂OL₂]⁴⁺ and [V₂OL₄]⁴⁺ complexes were observed, and in the vanadium(III)–8hq system the complexes [V(OH)L]⁺, [V(OH)₂L], [VL₂]⁺ and [VL₃] were detected.