Kinetics of ligand exchange reaction of Cu(II)-ammine complex with poly(vinyl alcohol) in aqueous solution

The kinetics of the ligand exchange reaction of the Cu(II)-ammine complex with poly(vinyl alcohol) (PVA) has been studied by a stopped-flow method at pH 9–10, at μ=0.1 (NH₄Cl) and at 25°C. The reaction is initiated by the formation of unstable [Cu(NH₃)₃]²⁺ by the attack of H⁺ on Cu(II)-ammine complex, and proceeds through the mixed complex {[Cu(NH₃)₃(O?PVA)]²⁺}. This step may be rate-determining, followed by a rapid reaction. Finally, the Cu(II) ion is taken up by PVA. The rate is given by d[Cu(II)?PVA]/dt=k[H⁺]{[Cu(NH₃)₄]²⁺}[PVA]/[NH₄Cl], where k=k₁ + k′₂[H⁺], k₁=4.25× 10s^?1 and k′₂=5.20× 10¹¹l mol^?1s^?1.     

Nanostructured catalysts for oxygen electroreduction based on bimetallic monoethanolamine complexes of Co(III) and Ni(II)

Oxygen reduction electrocatalysts based on the monoethanolmine complexes {[CoEtm]₂(μ-Etm)₄Ni(NO₃)₂} and {[CoEtm]₂(μ-Etm)₄Ni(NO₃)₂} + activated carbon AG-3 have been obtained by high-temperature synthesis. The nature of active centers on the synthesized electrocatalysts was described. Using potentiostatic and cyclic potentiodynamic voltammetry, the kinetic characteristics of catalysts in the oxygen electroreduction reaction were determined. Thermal decomposition of the thermally unstable complexes was described and character of the active centers formed was discussed. The optimal synthesis temperature of electrocatalysts is 600 °C in an inert atmosphere. The calculated exchange current densities for the oxygen electroreduction reaction at the catalysts in 1 M KOH at 20 °C was j ₀  = 1.01 × 10^?3 A g^?1–3.3 × 10^?3 A g^?1. The Tafel slopes of stationary polarization curves are 0.054–0.063 V for b ₁ and 0.106–0.125 V for b ₂ . The prepared electrocatalysts can be recommended only for electrochemical systems with alkaline electrolyte.     

Voltammetric study of complexing sodium cation with dibenzo-18-crown-6 in nitrobenzene phase of two-phase water-nitrobenzene extraction system

The facilitated transfer of the Na⁺ cation through the water (w)/nitrobenzene (nb) interface affected by dibenzo-18-crown-6 dissolved in the organic phase was studied by the cyclic voltammetry in the temperature range of 5–65°C. The transfer was found to be a very fast process at each studied temperature (5, 20, 35, 50, and 65°C); the process is controlled by diffusion of the electroneutral crown ionophore from the volume of the nitrobenzene phase to the interface. Changes of thermodynamic functions characterising the studied equilibrium reaction Na⁺ (nb) + L(nb) ? NaL⁺ (nb), where L = dibenzo-18-crown-6, were determined for a temperature of 25°C: ΔG = ?36.0 kJ mol^?1, ΔH = 38.9 kJ mol^?1, and ΔS = ?9.7 J mol^?1 K^?1. Further, the change of the standard Gibbs energy of the transfer of the NaL⁺ complex from the aqueous phase into the nitrobenzene one, ΔG^{0,w → nb}_{tr, NaL⁺} = ?20.1 kJ mol^?1, was calculated together with the value of the standard Galvani potential difference of the NaL⁺ cation between the nitrobenzene and the aqueous phases, Δ^nb_wφ⁰_NaL⁺ = 0.208 V, and the value of Briggs' logarithm of individual extraction constant, log Kⁱ_Nal⁺ = 3.5 (L = dibenzo-18-crown-6), for the two-phase water-nitrobenzene system.     

Ionic association equilibria of copper(II) trifluoroacetate in dimethyl sulphoxide

The molar conductivity curve and changes in the visible spectrum induced by changing concentrations have been determined for Cu(CF₃COO)₂ in dimethyl sulphoxide (DMSO) solution, at 25°C. Coupled with the spectra of the Cu(ClO₄)₂ + Bu₄N CF₃COO mixed solutions the results indicate occurence of the CuCF₃COO⁺ complex as the predominant copper(II) species in the solutions of Cu(CF₃COO)₂. The next higher complex, Cu(CF₃COO)⁰₂, is only formed at high concentrations of Cu(CF₃COO)₂ or under excess concentration of the CF₃COO^? anion. Formation of the first complex has also been studied callorimetrically, its derived thermodynamic characteristics being: K⁰₁ = 697 ± 12, ΔH⁰ = (7.85 ± 0.2) kJ/mol, and ΔS° = (80.6 ± 1.6) J/K mol, at 25°. On the other hand, K⁰₂ is only estimated as 13 ± 5. The results are compared with those previously obtained for the other divalent transition metal trifluoroacetates and the nature of the CuCF₃COO⁺ complex is discussed.     

Comportement electrochimique et reactivite du systeme Ag(II)-Ag(I)-bipyridine dans le carbonate de propylene

The electrochemical behaviour of silver(I)- and silver(II)-bipyridyl complexes has been investigated using voltammetry, cyclic voltammetry and coulometry in propylene carbonate. In unbuffered non-acidic medium, when the stoichiometry of the solutions is C_L/C_Ag = 2, the Ag^I(bipy)⁺ concentration is low; the preponderant species is Ag^I(bipy)₂⁺. Under such conditions, the Ag^II(bipy)₂²⁺/Ag^I(bipy)₂⁺ couple hs a reversible behaviour and is one of the must powerful oxidants used in the solvent (E^′° = 0.790 V vsE_Fc^′° + _Fc). As a function of the acidity level of the solutions, one observes the oxidation of either Ag^I(bipy)⁺ or Ag⁺ in the presence of the protonated ligand to complexed Ag(II). The silver(II) species produced oxidizes water and the excess of ligand (C_L/C_Ag > 2).     

Stepwise Stability Constants of Trivalent La,Ce, Pr,and Sm Complexes of Isopropylmercaptan

The complexation of La³⁺, Ce³⁺, Pr³⁺ and Sm³⁺ ions with isopropylmercaptan has been studied by potentiometric and conductometric titration techniques in aqueous – 10% ethanolic (V/V) medium . Title metal ions form 1:1, 1:2 and 1:3 complexes in the pH range 6.0–8.0 with considerable overlapping. Their log K_stab. values are determined at 15°, 25° and 35°C at ionic strength μ = 0.1 M (NaClO₄) by applying Calvin and Melchior's extension of Bjerrum method. The values of thermodynamic parameters ΔG, ΔH and ΔS have been calculated at 25°C with the help of an isobar and Gibb's Helmholtz equation. The trend in the stability constant values of the metal-complexes has been found to be .     

Formation of double-surface-silvered polyimide films via a direct ion-exchange self-metallization technique: The case of BPADA/ODA and [Ag(NH3)2]+

Double-surface-silvered polyimide (PI) films have been successfully fabricated via a direct ion-exchange self-metallization method using silver ammonia complex cation ([Ag(NH₃)₂]⁺) as silver resource and bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride/4,4′-oxydianiline (BPADA/ODA)-based poly(amic acid) (PAA) as the PI precursor. The alkaline characteristic of the silver precursor dramatically improves the efficiency of the ion exchange and film metallization process. By using an aqueous [Ag(NH₃)₂]⁺ solution with a concentration of only 0.01M and an ion-exchange time of only 5 min, metallized films with desirable performance could be easily obtained by simply heating the silver(I)-doped PAA films to 300°C. The strong hydrolysis effect of the basic [Ag(NH₃)₂]⁺ cations on the flexible and acidic BPADA/ODA PAA chains was observed during the ion exchange process by the quantitative evaluation of the mass loss of PAA matrix. Nevertheless, under the present experimental conditions, the final metallized film essentially retained the basic structural, thermal, and mechanical properties of the pristine PI, which make it a truly applicable material. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Ionization equilibria in solutions of cobalt(II) bromide in N,N-dimethylformamide

Visible absorption spectra and the molar conductance curve of CoBr₂ dissolved in N,N-dimethylformamide (DMF) have been determined at 25°C. Absorption spectra of ternary systems Co(ClO₄)₂ + Et₄NBr + DMF and CoBr₂ + chlorobenzene + DMF have also been determined at 25°C. The results indicate the formation of the CoBr(DMF)⁺₅. CoBr₃DMF⁻ complex electrolyte controlling the electrolytic properties of the solution. The stability constants of the individual bromo-complexes of cobalt(II) have been calculated.     

Potential of the Pb,PbSO4/H2SO4 electrode at temperatures up to 240°C

Standard lead—lead sulphate electrode potential was determined over the temperature range 20–240°C from emf measurements of the Pb, PbSO₄H₂SO₄ (0.05M)K₂SO₄KClHCl(0.1M)/AgCl, Ag and Pb, PbSO₄H₂SO₄(m)K₂SO₄H₂SO₄(0.05M)PbSO₄, Pb cells where m = 0.005, 0.01, 0.1 and 0.5 M. To this effect lead—lead sulphate electrode potential was calculated using the temperature relationship of the standard silver—silver chloride electrode potential and activity coefficients of hydrochloric acid determined by Greeley et al. at temperatures up to 260°C. Diffusion potentials occurring at the phase boundaries in the cells under investigation were calculated using the Henderson's equation. Values of the standard lead—lead sulphate electrode potential were determined by extrapolation of the E°′ function to the zero ionic strength which was calculated using the second sulphuric acid dissociation constant determined by Lietzke et al. at temperatures up to 300°C. The standard electrode potential was described in the temperature range 20–240°C by the following relationship: E°_{Pb, PbSO4/SO^2?4}(V) = 0.040-0.00126T. A change in entropy ΔS° of the electrode reaction Pb + SO^2?₄ = PbSO₄ + 2e^? is constant in this temperature range and is ?243 JK^?1 mol^?1 (?1018 cal K^?1 mol^?1).     

Thermodynamics of lithium,potassium and thallium electrode in propyléne carbonate

Standard potentials (E°) of Li, K and Tl electrodes in propylene carbonate (PC) have been determined, at 25°, on the basis of the “solvent-independent” half-reaction: Ferricinium⁺ +e ?Ferrocene. In addition, estimates of ΔG°, ΔH°, and ΔS° for the formation of Li⁺, K⁺, and Tl⁺ in PC have been obtained from temperature-dependence studies. The observed values of E° are in the order Tl > Li > K as compared to the order Tl > K > Li in water. The decrease in entropy, which would serve as a measure of the order-promoting ability of an ion, follows the sequence Li > K > Tl. From a consideration of the crystallographic radii of the cations involved this trend would suggest that such ordering is primarily a result of electrostatic solvation in the immediate vicinity of the ions. The somewhat large decrease in entropy observed in the case of Li⁺ reflects very extensive solvation of this particular cation. The free energies of transfer for the three cations from water (D = 78·54) to PC (D = 64·4) are calculated to be +1·81 (Li⁺), ?2·42 (K⁺), and ?2·88 (Tl⁺) kcal/mole. Although an approximately linear relationship exists between these free energies of transfer and the reciprocals of crystallographic radii of the ions, both the magnitudes and the signs of these free energies are not readily understood in terms of the Born equation. The relatively large free energy decrease associated with the transfer of Tl⁺ might be attributed to a fairly strong solvation encountered by this cation due to its empty 5f orbital, aided by the possibility that the solvating carbonyl oxygen of PC is more accessible to the cations in general.     

Solvent effect on the dissociation of o-nitroanilinium ion in methanol-propylene glycol media at 25°C

The dissociation constants (K_s) of o-nitroanilinium ion have been determined at 25° in methanol, propylene glycol and mixtures of the two components containing 10, 30, 50, 70 and 90 wt. % propylene glycol by spectrophotometric measurements. Standard free energies of transfer, ΔG°_t(B) of o-nitroaniline from methanol to the other solvents have been evaluated from the measurement of solubilities at 25°C. The solvent effect on the proton transfer process of this acid: ΔG°_t[BH⁺?B]_sys = 2.303RT[p(K_s?p(K_m)] has been discussed in terms of the free energies of transfer ΔG°_t from methanol to other solvents, of the uncharged based B, of the hydrochloride of the base (BHCl) computed from the corresponding values for HCl and also of the individual ions assessed from the previous knowledge of ΔG°_t(Cl^?). The corresponding data for the protonated tris(hydroxymethyl)methyl amine [TrisH⁺] and p-nitroanilinium ion in the same solvent system obtained from the literature are also compared. ΔG°_t[BH⁺?B]_sys values for the dissociation of o-nitroanilinium ion have been found to increase less readily with wt.% propylene glycol compared to p-nitroanilinium ion and are in contrast with the decreasing nature of the corresponding values for the TrisH⁺ ion of different chemical nature. Electrostatic effect being negligible in this solvent system, the overall behaviour of these acids is found to be dictated by specific chemical nature of solute-solvent interactions besides the effect of relative solvent basicities.     

Removal of Copper(II) and Zinc(II) from Aqueous Solutions Using a Lignocellulosic-Based Polymeric Adsorbent Containing Amidoxime Chelating Functional Groups

In this study, the adsorption of Cu(II) and Zn(II) ions from aqueous solutions onto amidoximated polymerized banana stem (APBS) has been investigated. Infrared spectroscopy was used to confirm graft copolymer formation and amidoxime functionalization. The different variables affecting the sorption capacity such as pH of the solution, adsorption time, initial metal ion concentration, and temperature have been investigated. The optimum pH for maximum adsorption was 10.5 (99.99%) for Zn²⁺ and 6.0 (99.0%) for Cu²⁺ at an initial concentration of 10 mg L^?1. Equilibrium was achieved approximately within 3 h. The experimental kinetic data were analyzed using pseudo-first-order and pseudo-second-order kinetic models and are well fitted with pseudo- second-order kinetics. The thermodynamic activation parameters such as ΔG^o, ΔH^o, and ΔS^o were determined to predict the nature of adsorption. The temperature dependence indicates an exothermic process. The experimental isotherm data were well fitted to the Langmuir model with maximum adsorption capacities of 42.32 and 85.89 mg g^?1 for Cu(II) and Zn(II), respectively, at 20°C. The adsorption efficiency was tested using industrial effluents. Repeated adsorption/regeneration cycles show the feasibility of the APBS for the removal of Cu(II) and Zn(II) ions from water and industrial effluents.     

Ion—solvent interactions in acetonitrile + water mixtures

Standard Gibbs energies of transfer, ΔG°_t of alkali metal chlorides (M = Li, Na, K, Rb and Cs) and potassium bromide and iodide from water to the aqueous mixtures of 20, 40, 60 and 80 mass per cents of acetonitrile (ACN) have been determined at 25°C from emf measurements performed on the double cell comprising AgAg X and M (Hg) electrodes. The individual ionic contributions to ΔG°_t have also been evaluated using the reference electrolyte (RE = Ph₄AsBPh₄) method, the required ΔG°_t's of the RE being obtained from the measured solubilities of salts viz. Ph₄AsPic, KBPh₄ and KPic (Pic = picrate and Ph = phenyl). The observed increasing ΔG°_t values of the halide ions X^? and their order Cl^? ? Br^? ? I^? furnish the thermodynamic evvidence for the effect of the well known decreased H-bonding and the anion destabilizing propensities of dipolar aprotic cosolvent ACN. But the observed shallow minima in ΔG°_t-composition profiles for M⁺ and H⁺ are indicative of the result of the oppositg effects of water structure breaking propensities and the protophobic character of ACN and their relative order is the combined effects of acid—base, Born-type and soft—soft interactions. Moreover, while the distinctly pronounced stabilization of large tetraphenyl ionshas been ascribed as the combined effects of dispersion and cavity-forming interactions, the less pronounced solvation of Pic^? has been attributed to the combined effects of increased dispersion interactions of benzene nucleus and of decreased H-bonding interactions of O-atoms of the substituents. These contentions have been further substantiated by comparing ΔG°_t(i) values of some selected ions in ethylene glycol—water mixtures.     

Ionization equilibria of copper(II) chloride in dimethyl sulphoxide

Visible absorption spectra of the CuCl⁺ and CuCl⁰₂ complexes in dimethyl sulphoxide (DMSO) are derived from an auxiliary study of the Cu(ClO₄)₂ + Et₄NCl mixed solutions of variable chloride concentration. The second step association equilibrium CuCl⁺ + Cl^? ? CuCl⁰₂ is then shown, from the visible absorption spectra, to predominate over a broad concentration range in the solutions of CuCl₂ in DMSO. Accordingly, the second step association constant is derived from the molar conductivity curve of CuCl₂ using the Shedlovsky's method, while the first step association constant is estimated from the conductometric data of the most dilute solutions: K⁰₁ = (16.5 ± 1.5)10⁴, K⁰₂ = (8 ± 0.2)10² at 25°C. The results are compared with those earlier obtained for NiCl₂ and CoCl₂ in DMSO solution, non-conformation of the association constants to the Irving-Williams series being pointed out.     

Expanding the chemistry of single‐ion conducting poly(ionic liquid)s with polyhedral boron anions

The synthesis of a new family of single‐ion conducting random copolymers bearing polyhedral boron anions is reported. For this purpose two novel ionic monomers, namely [B₁₂H₁₁(OCH₂CH₂)₂OC(?O)C(CH₃)?CH₂]^2?[(C₄H₉)₄N⁺]₂ and [8‐(OCH₂CH₂)₂OC(?O)C(CH₃)?CH₂‐3,3′‐Co(1,2‐C₂B₉H₁₀)(1′,2′‐C₂B₉H₁₁)]^?K⁺, having methacrylate function, diethylene glycol bridge and closo‐dodecaborate or cobalt bis(1,2‐dicarbollide) anions were designed. Such monomers differ from previously reported ones by (i) chemically attached highly delocalized boron anions, by (ii) valency of the anion (divalent anion and monovalent one) and by (iii) the presence of oxyethylene flexible spacer between the methacrylate group and bonded anion. Their free radical copolymerization with poly(ethylene glycol) methyl ether methacrylate and subsequent ion exchange provided lithium‐ion conducting polyelectrolytes showing low glass transition temperature (?53 to ?49 °C), ionic conductivity up to 9.1 × 10^?7 S cm^?1, lithium transference number up to 0.61 (70 °C) and electrochemical stability up to 4.1 V versus Li⁺/Li (70 °C). The incorporation of propylene carbonate (20–40 wt%) into the copolymers resulted in the enhancement of their ionic conductivity by one order of magnitude and significantly increased their electrochemical stability up to 4.7 V versus Li⁺/Li (70 °C). © 2019 Society of Chemical Industry     

Mercury-mercurous propionate electrode: standard potentials at different temperatures and related thermodynamic quantities in dioxan-water media

The standard molal potentials (E°_m/V) of the Hg/Hg₂(OPr)₂, OPr^? electrode at 15, 20, 25, 30 and 35°C have been determined in dioxan-water media. The values of E°_m as a function of the Celsius temperature, t, in different solvent composition may be represented by the following equations:

The related thermodynamic quantities have been calculated. The dependence of the standard potentials at 25°C on the dielectric constant of the media (in the light of the Born equation), the volume fraction (Φ_w) and the mole fraction (N_w) of water (based on Feakins-French relationship) have been examined. The variation of the thermodynamic quantities ΔG°, ΔS° and ΔH° with various parameters associated with solvent media have also been examined. The observations are similar to those reported in our previous work on mercury-mercurous acetate electrode in the same media. ΔC°_p for the cell reaction has been calculated.     

NMR STUDY OF LANTHANIDE(III) NITRATE-CMPO EXTRACTION SYSTEM (II)MOLECULAR MOVEMENT OF CMPO AND La(III)(NO3) 3-CMPO COMPLEX AND LIGAND-EXCHANGE REACTION FOR Eu(III)-CMPO AND Gd(III)-CMPO SYSTEMS

ABSTRACT

NMR( Nuclear Magnetic Resonance ) measurements were car ried out to study the molecular movement of CMPO and La(III)(NO₃) _3? CMPO complex and the ligand-exchange reaction for Eu(III) and Gd(III)-CMPO systems. From the ¹³C relaxation time measurement of La(NO₃) ₃ 3CMPO it was found that the T₁ value for the isobutyl CH and CH₂ carbons and the carbonyl carbon became considerably shorter on complexation, indicating that the carbonyl group participates in the bonding between CMPO and La³⁺ ion as well as the phosphoryl group. The numbers of CMPO molecules coordinated to Eu³⁺ and Gd³⁺ ions in CDCl₃ solution were estimated to be 3 and 2, respectively, in the presence of excess CMPO. The activation parameters for the ligand-exchange reaction were evaluated to be ΔH^* = 37.8±1.9[kJ/mol],ΔS^* = -59.9±6.5[J/molk? K] and ΔH^* = 41.3±1.6[kJ/mol], ΔS^* = -44.1±5.3[J/mol-K] for Eu(III)-CMPO and Gd(III)-CMPO systems, respectively. The independence of the exchange rate constants on the concentration of CMPO indicates that these ligand-exchange reactions seem to proceed through either a dissociative ( D ) mechanism or an interchange dissociative ( Id ) mechanism characterized by a stability constant of outer-sphere complex( KQ ) ≥ 100.     

Solutions of benzoic acid in formamide—II. thermodynamic properties from electromotive force measurements

The emf of the cell Pt, H₂, HBz(m), Hg₂Bz₂, Hg in formamide has been measured at 5°C intervals over the temperature range 5–45°C. The values of the standard potentials of the mercury—mercurous benzoate electrode can be fitted in the form of equation, obtained by using the least squares method:

The standard thermodynamic quantities (ΔG°, ΔH°, and ΔS°) for the cell reaction have been evaluated for different temperatures.     

One-pot template synthesis and crystal structure of two new polyaza copper(II) complexes

A new 14-membered hexazamacrocyclic copper(II) complex [Cu(H₂L¹)](ClO₄)₄(L¹=1,8-bis(2-aminoethyl)-1,3,6,8,10,13-hexaazacyclotetradecane) has been prepared by the one-pot reaction of ethylenediamine and formaldehyde in the presence of the Cu(II) ion. The crystal structure of [Cu(H₂L¹)](ClO₄)₄ was determined by X-ray diffraction. It crystallizes in the triclinic space group P−1 with a=12.118(2) Å, b=12.438(2) Å, c=12.466(2) Å, α=102.26(1)°, β=112.82(1)°, γ=111.51(1)°, and Z=2. The coordination geometry around the copper(II) ions is axially elongated octahedral with four nitrogen atoms of the macrocycle [Cu–N 2.012(7) Å for Cu(1) and 2.013(6) Å for Cu(2), average value] and two oxygen atoms of two ClO₄⁻ anions [Cu–O=2.550 Å for Cu(1) and 2.601(6) Å for Cu(2)]. [CuL²](ClO₄)₂(L²=3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo[3,3,2]decane) with a novel tetraazabicyclic ligand was obtained from the same reaction system as an additional product. Crystal structure of [CuL²](ClO₄)₂: monoclinic space group Cc, a=16.393(3) Å, b=8.8640(18) Å, c= 13.085(3) Å, β=105.01(3)°, and Z=4.     

Ionization equilibria in solutions of nickel(II) chloride in dimethyl-sulphoxide

Visible absorption spectra and the molar conductance curve of NiCl₂ dissolved in dimethyl-sulphoxide (DMSO) have been determined at 25°C. The results indicate the formation of the [NiCl(DMSO)₅]⁺ inner-sphere complex followed by the formation of the {NiCl(DMSO)₅]⁺Cl^?} outersphere ion-pair as the concentration of NiCl₂ increases. The [NiCl₂(DMSO)₄] inner-sphere complex in pure dimethyl sulphoxide at 25°C is formed to but a small extent, but its relative content increases upon addition of the non-coordinating diluent, chlorobenzene. Dilutions with chlorobenzene also enhance coordination disproportionation producing the [NiCl₃ DMSO]^? tetrahedral complex. The stability constant of the monochloro complex derived from the conductometric data has the value of 297 (^±10)M^?2 at 25°C, and the estimated value of the association constant of the [NiCl (DMSO)₅]⁺Cl^? complex electrolyte, dominating in moderately concentrated solutions at room temperature, is 7(±3)M^?1.