A Potentiometric Study of the Association of Copper(II) and Sulfate Ions in Aqueous Solution at 25 °C

A study of the association between copper(II) and sulfate ions in aqueous solution has been made using copper ion-selective electrode potentiometry at constant ionic strengths (I) of 0.05, 0.1, 0.25, 0.5, 1.0, 3.0 and 5.0 mol·L^?1 in NaClO₄ media at 25 °C. Only one complex was detected, corresponding to the equilibrium: \( {\text{Cu}}^{ 2+ } ({\text{aq}}) + {\text{SO}}_{4}^{2 - } ({\text{aq}}) \rightleftarrows {\text{CuSO}}_{4}^{0} ({\text{aq}}). \) No higher order complexes were detected even at sulfate/copper(II) concentration ratios of up to 1,000. The present potentiometric values of log₁₀ K ₁(I) are shown to be consistently higher than those obtained by UV–Vis spectrophotometry because of the failure of the latter technique to detect all of the solvent-separated ion pairs present. Extrapolation of log₁₀ K ₁(I) to infinite dilution using an extended Guggenheim equation yielded a standard state value of log₁₀ \( K_{1} \{ {\text{CuSO}}_{4}^{0} ({\text{aq}})\} = 2.32 \pm 0.09 \) , which is in excellent agreement with a recent IUPAC-recommended value.     

Stability Constants and Fluorescence of Terbium(Ⅲ) Complexes with Polyaminopolycarboxylates in Aqueous Solution

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Theoretical Studies on the Spin Exchange Interaction in Copper(II) Complexes Coordinated with Nitronyl Nitroxide

In the recent years, a wide variety of transition metal complexes with the nitronyl radical ligands have been reported1,2. These systems display the various magnetic behaviors (ferro- or antiferro-magnetism) between the unpaired electrons on the radical ligands and on the paramagnetic metal ion center. However, few theoretical studies on the metal-radical complexes were reported and quite few are known about the nature of the exchange coupling interactions. In this work, we are interested i…     

Potentiometric Studies of Copper(II) Complexes of Some Substituted Benzylidene-2-Hydroxyanilines in Dioxane–Water Media

The formation and protonation constants of 17 Schiff bases-derived 2-hydroxyaniline with some substituted benzaldehydes, and the stability constants of Cu(II) complexes of these Schiff bases, have been determined potentiometrically in 20, 40, and 60% dioxane–water media. The data from the potentiometric titrations were evaluated with the BEST computer program. For all Schiff bases studied, it was observed that the log K_OH values related to the protonation equilibria of the phenolic oxygen are increased, and the log K_NH values related to the protonation equilibria of the azomethine nitrogen are decreased, as the dioxane content is increased. The variation of these constants is discussed on the basis of specific solute–solvent interactions and structural changes of Schiff bases from water to the dioxane–water media. Also, titrimetric-pH investigation of substituted benzilidene-2-hydroxyaniline systems has revealed the formation of stable mono-Schiff base complexes with the metal ion Cu(II).     

Thermodynamic Characteristics of the Resolvation of Glycylglycinate Ions and Their Contribution to the Change in Stability of Complexes with Cu(II) and Ni(II) in Aqueous–Organic Solvents

Russian Journal of Physical Chemistry A - Thermodynamic characteristics (∆G, ∆Н, T∆S) of the resolvation of glycylglycine and its protonated and deprotonated forms in...     

Stability Constants of Copper(II) Glycylglycinate Complexes in Water–Dimethylsulfoxide Solutions

Russian Journal of Physical Chemistry A - Stability constants of normal and copper(II) bis-glycylglycinate complexes in water–dimethylsulfoxide solutions of variable composition are...     

A Comparative Study of Stabilities and Coordination Modes of β-Alaninephosphonic Acid in Copper(II) Heteroligand Complexes with Ethylenediamine, Diethylenetriamine or N,N,N′,N′,N″-Pentamethyldiethylene Triamine in Aqueous Solution

Solution equilibrium studies on Cu²⁺?CL₁?CL₂ ternary systems have been performed by pH-potentiometry, UV?CVis spectrophotometry and EPR methods {where L₁ corresponds to a polyamine such as ethylenediamine (en), diethylenetriamine (dien), N,N,N??,N??,N??-pentamethyldiethylenetriamine (Me₅dien)} and L₂ denotes 2-aminoethylphosphonic acid (??-alaninephosphonic acid)}. The results suggest the formation of heteroligand complexes with [Cu(L₁)(??-Ala(P))] stoichiometry in all of the studied systems. Additionally, in the system with en, [Cu(en)(??-Ala(P))H_?1]^? is formed in basic solutions. Our spectroscopic results indicate tetragonal geometry for the [Cu(en)(??-Ala(P))] species, a geometry slightly deviated from square pyramidal for the [Cu(dien)(??-Ala(P))] complex, and somewhat stronger geometry distortion was present for the [Cu(Me₅dien)(??-Ala(P))] complex. The coordination modes in these heteroligand complexes are discussed.     

Aqueous Equilibrium and Solution Structural Studies of the Interaction of N,N′-bis(4-imidazolymethyl)etylenediamine with Ca(II), Cd(II), Co(II), Cu(II), Mg(II), Mn(II), Ni(II), Pb(II) and Zn(II) Metal Ions

Divalent metal complexes of N,N′-bis(4-imidazolymethyl)etylenediamine (EMI) have been studied using potentiometric and spectroscopic techniques (UV-Vis and NMR methods) in aqueous 0.1 mol⋅L⁻¹ KCl supporting electrolyte at 25 °C. Final models and overall stability constants for the complexes of Ca(II), Cd(II), Co(II), Cu(II), Mg(II), Mn(II), Ni(II), Pb(II) and Zn(II) have been established by potentiometry for all M(II)–EMI systems, except for Co(II)–EMI. The data revealed that EMI forms ML complexes with all M(II)–EMI systems, which is the dominant species over a wide range of pH except for the Ca(II)–EMI and Mg(II)–EMI systems. Formation of the MnHL complex was also found for Mn(II)–EMI solutions. In addition, the UV-Vis and ¹H NMR results allowed us establish the coordination modes for the metal complexes between EMI with Cd(II), Cu(II), Ni(II) and Zn(II).     

Synthesis,Characterization, Solution Stability Studies,Electrochemistry, and DNA‐Binding Behavior of Cu(II) Complexes of D‐Gluconic Acid

The chemistry of saccharides has emerged as a new subarea of pharmaceuticals. Condensation reactions of D‐gluconic acid with [M(en)₂]Cl₂/[M(ea)₂]Cl₂ where M=Cu, Ni, en=ethylenediamine, and ea=ethanolamine were carried out and a new series of chiral complexes have been isolated and characterized. Molar conductance measurements show that the complexes are ionic, and the spectral data are indicative of octahedral geometry of the complexes [Cu(D‐GlcCO₂H en*)₂ (H₂O)₂] · Cl₂ (1b), [Cu(D‐GlcCO₂H ea*) (H₂O)₂] · Cl₂ (3b) and [Ni(D‐GlcCO₂H ea*) (H₂O)₂] · Cl₂ (4), and the square planar geometry of complex [Ni(D‐GlcCO₂H en*)₂] · Cl₂ (2b). Polarimetric data along with CD spectra establish the chiral nature of complexes. Solution stabilities of these complexes were evaluated by cyclic voltammetric techniques as a function of pH. Electrochemical behavior of the complexes was studied in aqueous solution and showed an irreversible Cu^II/Cu^I couple. Kinetic studies of complex 1b and 3b with calf thymus DNA have been investigated spectrophotometrically under pseudo‐first order conditions, and k _obs values have been evaluated. Circular dichroism, cyclic voltammetry determinations, and viscosity measurements have also been carried out to authenticate the binding of DNA with metal complexes. Complexes 1b and 3b bind to DNA by covalent bond formation.     

Synthesis of β-Ketoiminato Copper(II) Complexes and Their Use in Copper Deposition

The template synthesis of ethylenediamine ( 1 ) with 2-acetylcyclopentanone ( 2 ) and [Cu(OAc)₂ · H₂O] ( 5 ) produced [Cu(1-(2-cC₅H₆(O))C(Me)NCH₂)₂)] ( 6 ) in 82 % yield. Reaction of 5 with bis(benzoylacetone)diethylenetriamine ( 7 , = L H)^[1] gave [Cu(μ-OAc)( L )(H₂O)]₂ ( 8 ). The solid-state structures of 6 and 8 were determined confirming that 8 possesses intra- and intermolecular hydrogen bonds resulting in a dimer formation. The thermal behavior of 6 – 8 was studied by TG and TG-MS. Under oxygen CuO was formed, whereas under Ar Cu/Cu₂O ( 6 ) or Cu ( 8 ) was obtained. Complex 6 was used as CVD precursor for Cu and Cu-oxide deposition (substrate temp., 400–500 °C, N₂, 60 mL · min^–1; O₂, 60 mL · min^–1; pressure, 0.87–1.5 mbar). The as-obtained deposits show separated particles of different appearance at the substrate surface as evidenced by SEM. Non-volatile 8 was applied as spin-coating precursor for Cu and CuO formation [conc. 0.25 mol · L^–1; volume 0.2 mL; 3000 rpm; depos. time 2 min; heating rate 50 K · min^–1; holding time 60 min (Ar), 120 min (air) at 800 °C]. The samples on silicon consist of granulated particles (Ar) or are non-dense with a grainy topography (air). EDX and XPS measurements confirmed the formation of Cu (Ar) or CuO (O₂) with up to 13 mol-% C impurity.     

Synthesis, Characterization, and Single-Crystal EPR Studies of Three Dinuclear Copper(II) Complexes and One Mixed-Valence Tetranuclear Copper(I)-Copper(II) Cluster with an Asymmetric Imidazole-Containing Tripodal Ligand with Copper(II)-Copper(II) Distances between 3.35 and 3.63 Å

The synthesis and characterization of three dinuclear copper(II) complexes and one mixed-valence tetranuclear cluster with the asymmetric imidazole-containing ligand bis(1,1'-imidazole-2-yl)(4-imidazole-4(5)-yl)-2-azabutane (biib) are described. X-ray crystallographic parameters for the copper complexes are as follows. [Cu(2)(biib)(2)(BF(4))(2)](BF(4))(2)(H(2)O)(4): triclinic, space group P&onemacr;, a = 10.178(1) ?, b = 9.4881(9) ?, c = 11.037(1) ?, alpha = 95.130(10) degrees, beta = 112.20(1) degrees, gamma = 92.142(9) degrees, and Z = 1. [Cu(2)(biib)(2)(NO(3))(2)](NO(3))(2)(H(2)O)(4): monoclinic, space group &Pmacr;2(1)/n, a = 9.207(6) ?, b = 17.0516(6) ?, c = 12.6107(7) ?, beta = 109.82(1) degrees, and Z = 2. [Cu(2)(biib)(2)(CuBr(3))(2)]: monoclinic, space group P2(1)/c, a = 11.583(2) ?, b = 11.864(2) ?, c = 16.070(2) ?, beta = 112.459(12) degrees, and Z = 2. The two Cu(II) ions in all four complexes are coordinated in a square-pyramidal geometry by three imidazole nitrogens and one amine nitrogen donor in the equatorial plane, and each copper ion is weakly coordinated at the axial position by respectively a tetrafluoroborate, a perchlorate, a nitrate, or a tribromocuprate(I) anion. By comparison of the structural data of the four complexes a relationship has been established between the donor strength of the anion and some structural features, like the Cu(II)-Cu(II) distance, of the dinuclear Cu(II)-Cu(II) unit in the four complexes. Single-crystal EPR spectra of [Cu(2)(biib)(2)(BF(4))(2)](BF(4))(2)(H(2)O)(4) were recorded at room temperature at X-band frequencies. The triplet spectra have been fit with nonparallel g and D tensors, whose principle values are as follows: g(xx)() = 2.022(8), g(yy)() = 2.060(7), g(zz)() = 2.211(8), D(x)()(')(x)()(') = -0.0182(9) cm(-)(1), D(y)()(')(y)()(') = -0.081(6) cm(-)(1), D(z)()(')(z)()(') = 0.0264(7) cm(-)(1). The compounds were further characterized and studied by ligand field and by frozen-solution and polycrystalline powder EPR spectroscopy. EPR spectra recorded at 77 K of frozen solutions of the perchlorate complex show that upon dilution in methanol the dinuclear complex reacts to form a mononuclear species.     

Syntheses, Spectral Studies and Bioanalyses of Some Triorganotin(Ⅳ) Complexes of Cephlaxine

Five novel triorganotin(Ⅳ) complexes have been synthesized by refluxing trimethyl, triethyl, tributyl, triphenyl and tribenzyltin chloride with Cephlaxine.These compounds were characterized by spectroscopic (IR,1H, 13C, 119Sn NMR) techniques and elemental analysis.The results obtained through these techniques are in full agreement with the proposed 1:1 stoichiometry.The synthesized compounds were than tested against various microorganisms and fungi.The results of new products obtained showed that the triphenyltin(IV) complex displayed promising activity against all types of bacteria and fungi used while all other compounds showed significant antibacterial and antifungal activity.     

Stability and Structure of Binary and Ternary Metal Ion Complexes of Orotidinate 5′-Monophosphate (OMP3-) in Aqueous Solution

Abstract

The stability constants of the 1:1 complexes formed between Mg^{2 +}, Ca^{2 +}, Sr^{2 +}, Ba^{2 +}, Mn^{2 +}, Co^{2 +}, Ni^{2 +}, Cu^{2 +}, Zn ²⁺ or Cd ²⁺ and orotidinate 5′-monophosphate (OMP^3-) were determined by potentio-metric pH titrations in aqueous solution (I =0.1 M, NaNO₃; 25°C). In addition to the stability constants of these M(OMP)^? complexes, for several cases also the corresponding acidity constants for the release of the proton from the H(N-3) site were calculated; i.e., the formation of M(OMP-H)^2- complexes was quantified. On the basis of recent measurements for simple phosphate monoesters [R-MP^2-; R is a noncoordinating residue; S.S. Massoud and H. Sigel, Inorg. Chem., 27, 1447-1453 (1988)], evidence is provided that the somewhat increased stability of all the mentioned M(OMP)^? complexes is mainly the result of a charge effect of the carboxylate group (in position 6 of OMP^3-) and not of a direct participation in complex formation; i.e., there are no indications for the formation of significant amounts of macrochelates involving the phosphate and the carboxylate groups. This is different for the M(OMP-H)^2- complexes of Co ²⁺ , Ni²⁺ and Cd²⁺: in these cases significant amounts of macrochelates form; i.e., the metal ion is not only coordinated to the phosphate group but also (in part) to the ionized ^?(N-3) site, which is placed in the neighbourhood of the phosphate residue in the dominating syn conformation of this nucleotide. For the metal ions Mg^{2 +}, Ca²⁺, Sr^{2 +}, Ba²⁺ and Mn^{2 +}, which have in general a rather low affinity for N binding sites, no evidence for the formation of macrochelates is detected. In addition, the stability constants of the ternary Cu(Arm)(OMP)^? complexes, where Arm = 2,2′-bipyridyl or 1,10-phenanthroline, were determined by potentiometric pH titrations. Evaluation of the stability data shows that an equilibrium betweeen an ‘open’ isomer and a Cu(Arm)(OMP)^? species with an intramolecular stack exists; the formation degree of these aromatic ring stacks reaches about 40 percent. Overall it is quite evident that OMP^3- is a versatile ligand with remarkable properties which may be utilized by nature in recognition reactions during the intricate metabolic processes in which this nucleotide is involved.     

Thermodynamic and 13C NMR Studies of the Inclusion Complexes of α- and β-Cyclodextrins with Cyano- and Nitrophenols in Aqueous Solution

Equilibrium constants for the formation of 1 : 1 inclusioncomplexes of -cyclodextrin (-CD) with neutral and anionic phenol derivatives (3- and 4-cyanophenols and 3- and 4-nitrophenols) have been evaluated at 5, 12, 25, and 35 °C by means of spectrophotometry. Similarly, the equilibrium constants have been determined for the inclusion complexes of-cyclodextrin (-CD) with the phenols. Enthalpy and entropy changes for the formationof the inclusion complexes have been estimated from the temperature dependences of theequilibrium constants. With -CD, the enthalpy andentropy changes for the anionic species have been found to be more negative than those for the neutral ones, except for 4-cyanophenol, suggesting that the inclusion complexes of the anionic species are more rigid than those of the neutral species. From analyses of chemical shift differences in ¹³C NMR spectra of 3- and 4-cyanophenolsand 3- and 4-nitrophenols in aqueous solutions with and without CDs, a nitro ora cyano group has been found to be first bound to the - and -CD cavities.     

Coordination Features of a Polyaza-Bipyridine-Macrocyclic Ligand toward Co(II) and Cd(II) in Water and Dimethylsulfoxide

The coordination features of a polyaza macrocycle, containing the diverse bipyridine unit 4,4′-(2,5,6,11,14-pentaaza[15]-[15](2,2′)-bipyridylophane (L3), with Co(II) and Cd(II) have been studied in aqueous solution and in the aprotic solvent dimethylsulfoxide (DMSO). The study was carried out at 298 K by means of potentiometric, spectrophotometric and calorimetric techniques. The formation of the dinuclear species M₂ L3 is observed for Co(II) both in water and in DMSO, whereas Cd(II) is able to form this type of dinuclear complex only in DMSO. The FT-IR spectra of the mononuclear species ML3, formed in both solvents, provide evidence that the rigid structure of the polyaminic chain prevents metal ions from being coordinated by all of the nitrogens of the macrocyclic cavity, in good agreement with the behavior suggested by the thermodynamic parameters. The results are compared with those for the complexation of Co(II) and Cd(II) with similar polyazamacrocycles containing a bipyridine unit directly inside the cavity. Semi-empirical calculations were also performed to obtain structural information.     

Synthesis and Characterization of Complexes of Copper(II), Nickel(II) and Cobalt(II) with vic-Dioximes Bearing N''-p-Aminobenzoyl Benzaldehyde Hydrazone

Six different arylhydrazone derivatives of p-aminobenzoic hydrazide of vic-dioximes were synthesized by reaction of chloroglyoxime and dichloroglyoxime with N＇-p-aminobenzoyl benzaldehyde, 4-hydroxybenzaldehyde and 4-methoxybenzaldehyde hydrazones, respectively. Metal-ligand （1 ： 2） complexes of vic-dioxime derivatives with Cu（Ⅱ）, Ni（Ⅱ） and Co（Ⅱ） were prepared from corresponding metal acetates. The ligands and their complexes were characterized on the basis of elemental analyses and spectral data. The complexing abilities of these new vic-dioximes toward transition metals of Co（Ⅱ）, Cu（Ⅱ）, Ni（Ⅱ）, Zn（Ⅱ）, Cd（Ⅱ）, Mn（Ⅱ） and Cr（Ⅲ） were determined by solid-liquid extraction studies.     

Kinetic Studies on Interaction of Platinum(II) Complexes with an ‘S’ Containing Ligand in Aqueous Medium

The kinetics of the substitution reactions of [Pt(dach)(H₂O)₂]²⁺ and [Pt(en)(H₂O)₂]²⁺ (where ‘dach’ and ‘en’ are cis-1,2-diaminocyclohexane and ethylenediamine, respectively) with excess N,N′-diethylthiourea have been studied in aqueous solution by UV–Vis spectrophotometry. The effect of different N–N spectator ligands on the reactivity of platinum(II) complexes was investigated by studying the water lability of the reactant complexes. The kinetic study has been substantiated by product isolation, IR, NMR and ESI-MS spectral analysis and DFT calculations. The reactions follow normal square-planar substitution mainly in an associative way. Rate parameters have been evaluated under different conditions. The substitution rates of the complexes studied can be tuned through the nature of the N–N chelates, which is important in the development of new active compounds for cancer therapy.     

Theoretical Studies on the Conformation of mono-6-O-p-nitrobenzoyl-β-cyclodextrin in Aqueous Solution

It is well known that a substituted cyclodextrin (CD) can often form a self-included complex, in which the substituent group is incarcerated into the CD cavity1. The phenomenon is interesting, as the self-inclusion is a nice model of protein folding2 and it has also been successfully used in the construction of various molecular devices3. Studies have showed that van der Waals force, hydrophobic effect, and electrostatic interaction are the major driving forces leading to the self-inclusion4…     

Complexation Studies of Pyridyl Sulfonamide Ligands for Sensing Zinc and Copper Ions

Ligand protonation and stepwise dissociation constants, formation constants and speciation of four pyridyl sulfonamide ligands (Congreeve et al., New J. Chem. 27:98–106, 2003) were assessed, using potentiometric and UV/Visible spectrophotometric pH titrations (in 80% MeOH − 20% H₂O). The suitability of these ligands as Cu(II) and Zn(II) sensors for physiological applications was assessed. Two ligands L¹ and L⁴ were p-toluenesulfonamide derivatives while L² and L³ were triflurosulfonamide derivatives. Additionally L³ and L⁴ were appended with α-methyl groups. The most stable complex was formed by L¹ with Cu(II) owing to the fact that this complex was square planar (log ₁₀  K ₁=12.15±0.004 and log ₁₀  β ₂=15.42±0.006). The rest of the complexes invariably formed distorted tetrahedron geometry and complexation was weaker. Speciation diagrams show the effect of ligand to metal concentration, revealing that the L² and L³ ligands are the most suitable for forming ML₂ complexes at physiological pH.     

Spectral and Mechanistic Investigation of the Osmium(VIII) Catalyzed Oxidation of Diclofenac Sodium by the Copper(III) Periodate Complex in Aqueous Alkaline Medium

The kinetics of the osmium(VIII) (Os(VIII)) catalyzed oxidation of diclofenac sodium (DFS) by diperiodatocuprate(III) (DPC) in aqueous alkaline medium has been studied spectrophotometrically at a constant ionic strength of 1.0 mol⋅dm⁻³. The reaction showed first order kinetics in [Os(VIII)] and [DPC] and less than unit order with respect to [DFS] and [alkali]. The rate decreased with increase in [periodate]. The reaction between DFS and DPC in alkaline medium exhibits 1:2 [DFS]:[DPC] stoichiometry. However, the order in [DFS] and [OH⁻] changes from first order to zero order as their concentration increases. Changes in the ionic strength and dielectric constant did not affect the rate of reaction. The oxidation products were identified by LC-ESI-MS, NMR, and IR spectroscopic studies. A possible mechanism is proposed. The reaction constants involved in the different steps of the mechanism were calculated. The catalytic constant (K _C) was also calculated for Os(VIII) catalysis at the studied temperatures. From plots of log ₁₀ K _C versus 1/T, values of activation parameters have been evaluated with respect to the catalytic reaction. The activation parameters with respect to the slow step of the mechanism were computed and discussed, and thermodynamic quantities were also determined. The active osmium(VIII) and copper(III) periodate species have been identified.