Complexation of Dioxovanadium(V) with D-(-)-Quinic Acid at Different Ionic Strengths Using Different Models Based on the Debye-Hückel Theory

The complex formation reaction between the dioxovanadium(V) cation $\mathrm{VO}_{2}^{+}$ and D-(-)-quinic acid {(1R,3R,4S,5R)-(-)-1,3,4,5-tetrahydroxycyclohexane-1-carboxylic acid} has been studied in aqueous solutions. The UV data and the values of the derived conditional stability constants are presented and discussed in the light of one stoichiometric model for the reaction at T=298?K and different ionic strengths (0.10 to 1.00)?mol?dm^?3 of sodium chloride. Speciation diagrams and dissociation constants were obtained on the basis of UV spectroscopic measurements and potentiometric titrations, respectively. Our results show that one complex species, VO₂L, exists in solution in the pH range of about 1.00 to 3.00. The parabolic, Specific Ion Interaction Theory (SIT), and extended Debye-Hückel type (EDH) models successfully describe the ionic strength dependence of the stability constants. A comparison with literature data is also reported.     

Acid–Base Properties, Solubility, Activity Coefficients and Na+ Ion Pair Formation of Complexons in NaCl(aq) at Different Ionic Strengths

The protonation constants and solubilities of three complexons [ethylenediamine-N,N′-disuccinic acid (EDDS), ethylene glycol bis(2-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA) and 1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid (CDTA)] are reported in aqueous solutions of NaCl with different ionic strength values (0 ≤ I ≤ 4.8 mol·L^?1) and, in the case of CDTA, in (CH₃)₄NCl (0.1 ≤ I ≤ 2.7 mol·L^?1). The dependence on ionic strength of the protonation constants of these three complexons and four other complexons that were previously reported (NTA, EDTA, DTPA and TTHA), is analyzed in NaCl solution; the ionic strength influences quite strongly the protonation constants (as an example for CDTA, log₁₀ K ₁ = 10.54 and 9.25 at I = 0.1 and 1 mol·L^?1, respectively), while the effect of (CH₃)₄NCl concentration is lower. Based on the total solubility S ^T and the protonation constant data at different salt concentrations, the solubility of the neutral species S ⁰ and the solubility products K _S0 are obtained. The Setschenow coefficients k _m and the solubility values S ₀ ⁰ in pure water are also reported (S ₀ ⁰  = 0.55, 0.21 and 0.75 mmol·kg^?1 for EDDS, EGTA and CDTA, respectively). The dependence of the protonation constants on ionic strength is also interpreted in terms of ion pair formation, and the formation constants of Na⁺ species are reported.     

Direct TLC Resolution of the Enantiomers of Three β-Blockers by Ligand Exchange with Cu(II)–l-Amino Acid Complex, Using Four Different Approaches

TLC experiments have been performed to resolve the enantiomers of three β-blockers by complexation chiral TLC with Cu(II) cation and five l amino acids. Loading was carried out by using the Cu(II)–l amino acid complex as chiral mobile phase additive with untreated silica gel plates; by mixing the Cu complex with silica gel before preparing the TLC plates; by ascending development of untreated plates with solutions of the Cu complex; and by using a solution of Cu(II) acetate as mobile phase additive for plates prepared by mixing the l amino acid with silica gel. Spots were located by use of iodine vapour.     

The Interaction of Arsenazo III with Nd(III)—A Chemometric and Metrological Analysis

Interactions of Arsenazo III with Nd(III) in aqueous solutions (pH range 3 to 4) were studied using a spectrophotometric method. Some discrepancies are present in literature concerning the concentrations of the prevailing species and their composition. Threshold bootstrap computer-assisted target factor analysis (TB CAT) was applied to the evaluation of UV-VIS spectra of Arsenazo III in aqueous solutions containing varying amounts of neodymium(III) ions. The thus obtained experimental data are interpreted with consideration of the measurement uncertainties affecting this system. Within the limits of resolution of the experimental method, two complexes NdAazo and Nd(Aazo)₂ were indicated in the studied pH range. The values of formation constants for log ₁₀ β ₁₁ fall in the range 4.9 to 6.3 and for log ₁₀ β ₁₂ fall between 10.5 and 12.1.     

Thermodynamics (Solubility and Protonation Constants) of Risedronic Acid in Different Media and Temperatures (283.15–318.15 K)

Potentiometric measurements were carried out to study the protonation constants of risedronic acid (RA) in NaCl_(aq), (CH₃)₄NCl_(aq) and (C₂H₅)₄NI_(aq) at different ionic strengths and temperatures (283.15 ≤ T/K ≤ 318.15). In the same conditions, solubility measurements were also performed. Calorimetric measurements were done in NaCl to determine the protonation enthalpy values at I = 0.15 mol·dm^?3 and 298.15 K. Generally, the proton binding process was endothermic and the driving force was entropic in nature. The values of the protonation constants determined in NaCl_(aq) are lower than those obtained in the two tetraalkylammonium salts. The medium effect was interpreted using different thermodynamic models in terms of variation of the activity coefficients with ionic strength (Debye–Hückel type and SIT), or formation of weak complexes between risedronate (Ris^4?) and the ions of the supporting electrolytes. Specific interaction coefficients (ε) and the stability of five (CH₃)₄N⁺/Ris^4? (at different temperatures and ionic strengths) species are reported. The total solubility of risedronic acid is higher in NaCl_(aq) than in the other two ionic media and, in all cases, increases with increasing temperature. Setschenow and activity coefficients of the neutral species were also computed in all ionic media.     

Study of Aqueous Biomolecules with Magnetic Flux Using Density,Viscosity, and Surface Tension Probe at 304.15 K

Doses of 0.0150 weber m^?2 magnetic flux for 30 minutes are given to four series of biomolecules in aqueous medium, densities (ρ), viscosities (η), and surface tension (γ) were measured at 304.15 K. The vitamins and carbohydrates decrease densities and viscosities and the difference of density from magnet to aqueous solution in order of dextrose (? 0.00025 kg m^?3) > fructose (? 0.00021 kg m^?3) = B6 (? 0.00021 kg m^?3) > starch (? 0.00018 kg m^?3) > B1 (? 0.0018 kg m^?3), while viscosity in order of starch (? 0.0044 kg m^?1s^?1) > fructose (? 0.0037 kg m^?1s^?1) > B1(? 0.0018 kg m^?1s^?1) > dextrose (? 0.0016 kg m^?1s^?1) > B6 (? 0.0012 kg m^?1s^?1). The surface tension also decreases in vitamin and carbohydrate. The proteins show increase in ρ, η, and γ value hence casein decrease the density and viscosity. The glutamine show increase in density and surface tension while decrease in viscosity and vice versa to alanine. These orders of the data indicate the intermolecular force between water and bimolecules in magnetic flux.     

Cystine as Ligand of Calcium(II) and Magnesium(II) in Two Ionic Media and at Two Different Temperatures (25 and 37 °C)

Cystine plays an important role in human physiology, it is the precursor of cysteine. Cystine is the molecular form preferred by the immunity cellules system, included macrophages. Although slightly soluble, it can be a ligand towards cations because it is a sulfur-containing amino acid. Because of the physiological importance of calcium(II) and magnesium(II), complex formation between these cations and cystine was studied potentiometrically by employing electrochemical cells involving glass electrodes. The investigation was performed at two temperatures (25 and 37) °C and in two ionic media (1.00 and 0.15 mol·dm^?3 NaCl). In both ionic media, the adoption of a constant ionic medium allows extension of the investigation to a large range of reagent concentration. As the formation of weak complexes was foreseen, the low solubility of cystine is an advantage. Experimental data can be explained in any case by assuming the formation of mononuclear complexes in the presence of both calcium(II) and magnesium(II). The relative stability constants were determined.     

Optical Resolution ofα-Bromo-2-Chlorophenacetic Acid by Way of Coordination with Copper(II) and O,O’-Dibenzoyltartaric Acid

Optically active molecules play important roles in medicinal chemistry and materials science in both industrial and academic sectors. Resolution is one of the most efficient ways to obtain enantiopure substances. For a long period, racemic carboxylic acids are generally resolved by optically active bases, however, these bases are often extremely toxic and expensive.[1] Recently, A. Mravik Group applied optically active O, O’-dibenzoyltartaric acid (DBTA), which is usually used for the res…     

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.     

Kinetics and Mechanism of the Interaction of Di-μ-hydroxobis(1,10-phenanthroline)dipalladium(II) Perchlorate with Thioglycolic Acid and Glutathione in Aqueous Solution

The kinetics of interaction between di-μ-hydroxobis(1,10-phenanthroline)dipalladium(II) perchlorate and thioglycolic acid and with glutathione has been studied spectrophotometrically in aqueous medium as a function of the complex concentration as well as the ligand concentrations, pH, and temperature at constant ionic strength. The observed pseudo-first-order rate constants k _obs (s^?1) obeyed the equation k _obs = k ₁[Nu] (Nu = nucleophile). At pH = 6.5, the interaction with thioglycolic acid shows two distinct consecutive steps and both steps are dependent on the concentration of thioglycolic acid. The rate constants for the process are: k ₁ ≈ 10^?5 s^?1 and k ₂ ≈ 10^?3 dm³ · mol^?1 · s^?1. The association equilibrium constant (K _E) for the outer sphere complex formation has been evaluated together with the rate constants for the two subsequent steps. The other bio-active ligand, glutathione, showed a single step reaction depending on [ligand] with a second-order anation rate constant: the 10² (k ₂) values are (61.72, 79.20, 109.24 and 154.33) dm³ · mol^?1 · s^?1 at 20, 25, 30 and 35 °C, respectively. On the basis of the kinetic observations and evaluated activation parameters, plausible associative mechanisms are proposed for both interaction processes.     

Polymerization of Methyl Methacrylate by the System Ribonucleic Acid–Water in the Presence of Carbon Tetrachloride and Copper(11) Ion

Polymerization of methyl methacrylate (MMA) was carried out in the presence of ribonucleic acid (RNA), water, carbon tetrachloride, and copper(II) ion. The overall activation energy for the polymerization is proportional to the square root of the amount of RNA. The rate increased at first with the amount of MMA, but then became independent of the amount of MMA.

Polymerization was inhibited by the presence of air. Carbon tetrachloride and copper(II) ion are able to give RNA the ability to initiate polymerization. Conversion of MMA is accelerated by the addition of tertiary amine derivatives instead of carbon tetrachloride.     

Synthesis,thermal and spectral studies of oxoperoxo and dioxo complexes of vanadium(V), molybdenum(VI) and tungsten(VI) with 2-(α-hydroxyalkyl/aryl)benzimidazole

Reaction of 2-(-hydroxymethyl)benzimidazole or 2-(-hydroxyethyl)benzimidazole (LH) with the peroxovanadium(V) species, generated in situ by stirring V₂O₅, KOH and 30% aqueous H₂O₂, gives the corresponding complexes of formula K[VO(O₂)L₂]. Similar peroxo species of molybdenum and tungsten generated by stirring MoO₃ or WO₃·H₂O with an excess of 30% aqueous H₂O₂ readily react with 2-(-hydroxyethyl) benzimidazole in aqueous EtOH to give the peroxo complexes [MO(O₂)L₂] (M=Mo or W). The dioxo complexes of general formula [MO₂L₂] have also been isolated by the reaction of [MoO₂(acac)₂] or [WO₂- (acac)₂] (acacH=acetylacetone) with the above ligands and with 2-(-hydroxybenzyl)benzimidazole. The dioxo complexes are white, whereas peroxo complexes are light yellow to orange. The peroxo complexes generally decompose in two steps: (i) the decomposition of the peroxo group and (ii) the decomposition of the alkyl/aryl group followed by decomposition of the complete ligand. On the other hand, decomposition of the dioxo complexes follows only in a later step. All the peroxo complexes exhibit three i.r. active vibrational modes at ca. 860cm^–1, 760cm^–1 and 600cm^–1, characteristic of the ²-coordinated peroxo group. The dioxo complexes are dominated by the presence of two sharp bands in the 900cm^–1 region due to _sym(O=M=O) and _asym(O=M=O) modes. The (C=N) (ring) and (OH) shifts have also been measured in order to locate the coordination sites of the ligands. A broad band at ca. 400nm in the peroxovanadium(V) complexes, while the absorption at ca. 350nm in the peroxomolybdenum(VI) and tungsten(VI) complexes is assigned to the peroxo-metal charge transfer band.     

Synthesis, Crystal Structure and DNA-binding Property of Bismuth(Ⅲ) Complex with p-Hydroxy-phenylacetic Acid

A bismuth(Ⅲ) complex 1 (H2-4,4'-bipy)Bi(HPPA)5(H2PPA)·4H2O (H2PPA = p-hydroxy-phenylacetic acid, 4,4'-bipy = 4,4 -bipyridyl) was hydrothermally synthesized from p-hydroxy-phenylacetic acid (H 2 PPA), Bi(NO 3) 3 ·6H 2 O and 4,4 -bipyridyl, and characterized by elemental analysis, IR, molar conductivity and TG. The single-crystal X-ray diffraction studies demonstrated that the complex is of monoclinic system, space group P21 with a = 10.928(7), b = 22.558(7), c = 11.313(7), β = 91.864(4)°, V = 2787.7(4)3 , Z = 2, C58H61BiN2O22 , Mr = 1347.07, F(000) = 1364, Dc = 1.605 g/cm-3 , μ(MoKα) = 3.247 mm-1 , the final R = 0.0269 and wR = 0.0540 for 9776 observed reflections with Ⅰ > 2σ(Ⅰ). The bismuth(Ⅲ) is seven-coordinated with O atoms, forming a monocapped octahedral geometry. Complex 1 further forms a 3D supramolecular architecture by hydrogen bonds and π-π stacking interactions. Moreover, the interaction between the complex and DNA was studied by EtBr fluoescent probe.     

Complex Formation Equilibria Between Zinc(II), Nitrilo-tris(Methyl Phosphonic Acid) and Some Bio-relevant Ligands. The Kinetics and Mechanism for Zinc(II) Ion Promoted Hydrolysis of Glycine Methyl Ester

Binary and ternary complexes of zinc(II) involving nitrilo-tris(methyl phosphonic acid (H₆A) and amino acids, peptides (HL), or DNA constituents have been investigated. The stoichiometry and stability constants for the complexes formed are reported. The results show that ternary complexes are formed in a stepwise manner whereby nitrilo-tris(methylphosphonic acid) binds to zinc(II), which is then followed by coordination of an amino acid, peptide or DNA. Zinc(II) was found to form ZnA and ZnAH _n complex species where n=3, 2 or 1. The stabilities of the ternary complexes are compared with the stabilities of their corresponding binary complexes. The concentration distributions of the various complex species have been evaluated. The kinetics of the base hydrolysis of glycine methyl ester in the presence of Zn(II)-NTP complexes was studied in aqueous solution using a pH-stat technique. The pK _a for ionization of the coordinated water molecule is 9.14 as determined from the kinetic results, while direct potentiometric titration of the complex [Zn(NTP)(H₂O)] gave 9.98 (±0.02). The rate constant for the intramolecular attack of coordinated hydroxide on the ester is k=(2.65×10⁻⁴±0.003) dm³⋅mol⁻¹⋅s⁻¹.     

Synthesis, Structure and Characterization of Manganese(Ⅱ) Coordination Polymer with Camphoric Acid and 1,10-Phenanthroline

A novel coordination polymer, Mn(H2O)(CA)(Phen)·H2O(CA=camphoric acid, Phen=1,10-phenanthroline), was synthesized and its crystal structure was determined by single crystal X-ray diffraction. Six-coordinated Mn(Ⅱ) atoms are linked with carboxyl groups from camphoric acid ligands to form infinite one-dimensional chains. These chains are packed by means of hydrogen bonding and π-π stacking, forming a three-dimensional structure. IR, thermogravimetric analysis and magnetic susceptibility data for Mn(H2O)(CA)(Phen)·H2O are given.     

Complexes of Zn(II) and Сu(II) with the Amino Derivatives of Deoxycholic Acid: Syntheses,Structures, and Properties

Russian Journal of Coordination Chemistry - Complexes [Zn(L)Cl2] (I), Cu(L)Cl2 ? H2O (II), Zn(L1)Cl2 ? 0.5H2O (III), and Cu(L1)Cl2 ? 0.5H2O (IV) (where L and L1 are the...     

Effect of Phosphonium Ionic Liquids on the Extraction of Rare-Earth Elements(III) with 2,2′-Oxybis(N,N-dioctylacetamide) from Nitric Acid Solutions

Russian Journal of General Chemistry - New phosphonium ionic liquids, alkyldiphenylethylphosphonium bis[(trifluoromethyl)sulfonyl]imides (Alk = C4H9, C8H17, and C12H25) have been synthesized. The...