Stability of 2-Carboxyphenylhydrazoethylacetoacetate Complexes of Rare-Earth Elements in Dioxan-Water Solution

The results of pH-metric titration have been used to determine the acid dissociation constants of 2-carboxy-pheylhydrazo-ethylacetoacetate abbrivated (2-CPHEA) and the overall stability constant (log β=K_ML, K_ML2) of twelve rare earth element complexes in 75% dioxan were calculated.     

Optical and Chromaticity Characteristics of Arsenazo III Complexes of Rare-Earth Elements

Optimal conditions for the complexation of La, Nd, Sm, Tb, Dy, Gd, Ho, Er, and Yb ions with Arsenazo III were found, and molar absorptivities of the complexes were calculated. Chromaticity characteristics of the complexes were determined. The coefficients of calibration plot equations and molar coefficients of chromaticity functions were calculated for the concentration range 10–50 g of rare-earth element per 25 mL of solution. It was demonstrated that the use of the most sensitive chromaticity functions increases the sensitivity of the reaction by 1.5–2 orders of magnitude compared to the photometric method.     

Stability Constants of Some Macrocyclic Complexes of Ag(I) and Cu(II) in Mixed Solvents by Potentiometry

Stability constants of complexes of Ag(I) and Cu(II) perchlorates and nitrates with some macrocyclic compounds in 90 and 75% (v/v) DMSO+water and 75% (v/v) DMF+water media have been determined by potentiometry. Silver and copper wires, and Coated Wire Ion Selective Electrodes (CWISE) were used as indicator electrodes. It was observed that complexation is stronger when the salt is present as a perchlorate than when it is as a nitrate. For both cations the stability constant values in 75% (v/v) DMF+water were somewhat higher than in 75% (v/v) DMSO. The macrocyclic effect due to cyclization of linear amine tosylates has been observed. Competitive potentiometry has been utilized to compare some of the results.     

Kinetics and Mechanisms of Dissociation of Mn Complexes with Porphyrins in Mixed Protolytic Solvents

Review of kinetic data on dissociation of the Mn porphyrin complexes in mixed proton-donor solvents depending on the structure of coordination core and porphyrin macrocycle is made. The mechanisms of the processes and the relationship between the stability of complexes, their structures, and composition of mixed solvents containing an acid are considered.     

混合配合物稳定常数的计算

本文研究了混合配合物的稳定性规律,得出了混合配合物稳定常数的各种计算方法.     

The Solubility and Solvation of Salts in Mixed Nonaqueous Solvents. 2. Potassium Halides in Mixed Protic Solvents

The solubilities of potassium fluoride, chloride, and bromide in ethanol, formamide, and N-methylformamide and in binary mixtures of these solvents were determined at 25°C. The standard molar Gibbs energies of solution, Δ_soln G ^o, in the neat solvents were related to their hydrogen bonding abilities. The values of Δ_soln G ^o in the mixtures were fitted with expressions of the quasilattice quasichemical theory, and the preferential solvation of the ions was thereby established.     

A Polarographic Study of Tl + , Pb 2 and Cd 2+ Complexes with Dicyclohexano-18-Crown-6 in Some Binary Mixed Solvents

The complexes of Tl⁺, Pb²⁺ and Cd²⁺ cations with the macrocyclic ligand, dicyclohexano-18-crown-6\linebreak(DC18C6) were studied in water/methanol (H₂₊O/MeOH), water/1-propanol (H₂₊O/1-PrOH), water/acetonitrile (H₂₊O/AN), water/dimethylformamide (H₂₊O/DMF), dimethylformamide/acetonitrile (DMF/AN), dimethylformamide/methanol (DMF/MeOH), dimethylformamide/1-propanol (DMF/1-PrOH) and dimethylformamide/nitromethane (DMF/NM) mixed solvents at 22 °C using differential pulse polarography (DPP), square wave polarography and conductometry. In general, the stability of the complexes was found to decrease with increasing concentration of water in aqueous/non-aqueous mixed solvents with an inverse relationship between the stability constants of the complexes and the concentration of DMF in non-aqueous mixed solvents. The results show that the change in stability of DC18C6.Tl⁺, vs the composition of solvent in DMF/AN and DMF/NM mixed solvents is apparently different from that in DMF/MeOH and DMF/1-PrOH mixed solvents. While the variation of stability constants of the DC18C6.Tl⁺ and DC18C6.Pb²⁺ complexes vs the composition of H₂₊O/AN mixed solvents is monotonic, an anomalous behavior was observed for variations of log K_f vs the composition of H₂₊O/1-PrOH and H₂₊O/MeOH mixed solvents. The selectivity order of the DC18C6 ligand for the cations was found to be Pb²⁺ > Tl⁺ > Cd²⁺.     

Synthesis And Characterization Of Complexes Of Rare Earth Elements With 1,1-Cyclobutanedicarboxylic Acid

The complexes of yttrium and lanthanide with 1,1-cyclobutanedicarboxylic acid of the formula: Ln₂(C₆H₆O₄)₃⋅nH₂O, where n=4 for Y, Pr–Tm, n=5 for Yb,Lu, n=7 for La, Ce have been studied. The solid complexes have colours typical of Ln³⁺ ions. During heating in air they lose water molecules and then decompose to the oxides, directly (Y, Ce, Tm, Yb) or with intermediate formation. The thermal decomposition is connected with released water (313–353 K), carbon dioxide, hydrocarbons(538–598 K) and carbon oxide for Ho and Lu. When heated in nitrogen they dehydrate to form anhydrous salt and next decompose to the mixture of carbon and oxides of respective metals. IR spectra of the prepared complexes suggest that the carboxylate groups are bidentate chelating. This revised version was published online in August 2006 with corrections to the Cover Date.     

氨基酸在氯乙醇水溶液中的体积性质

利用精密数字密度计测定了甘氨酸、L-丙氨酸和L-丝氨酸在不同质量分数的氯乙醇水溶液中的密度，计算了这些氨基酸在氯乙醇水溶液中的表观摩尔体积、极限偏摩尔体积、迁移偏摩尔体积、理论水化数和体积作用系数，讨论了迁移偏摩尔体积和理论水化数的变化规律. 结果表明，三种氨基酸在氯乙醇水溶液中的迁移偏摩尔体积均为正值, 且随氯乙醇浓度的增大而增大. 氨基酸侧链对迁移偏摩尔体积的贡献与侧链性质密切相关. 三种氨基酸在氯乙醇水溶液中的理论水化数均随溶液中氯乙醇浓度的增加而减小. 甘氨酸与氯乙醇分子间的相互作用主要以1 : 1和1 : 2形式为主， L-丙氨酸和L-丝氨酸与氯乙醇分子间的相互作用主要以1 : 1形式为主.     

Manganese Complexes with Octaphenyltetraazaporphine: Acid–Base Interactions and Kinetic Stability in Proton-Donor Solvents

Complexes of manganese(III) and manganese(V) with octaphenyltetraazaporphine (H₂OPTAP) were synthesized. Acid–base interactions of these complexes in the CH₂Cl₂–CF₃COOH system and kinetics of their dissociation in concentrated sulfuric acid, as well as kinetics of octaphenyltetraazaporphine destruction in sulfuric acid solutions were studied by spectrophotometric methods. Acid–base interactions in CH₂Cl₂–CF₃COOH were shown to involve two macrocyclic meso-nitrogen atoms in succession. Concentration stability constants of the acid forms obtained pK ₁ = 0.29 ± 0.01 and pK ₂ = –0.62 ± 0.08 for (chlorine)manganese(III)octaphenyltetraazaporphine ((Cl)MnOPTAP); pK ₁ = 0.99 ± 0.02 and pK ₂ = – 0.70 ± 0.03 for (nitrido)manganese(V)octaphenyltetraazaporphine ((N)MnOPTAP). The rate of dissociation of the complexes in 94–98% H₂SO₄ does not depend on the acid concentration. The manganese(V) complex is three times as stable as the manganese(III) complex.     

Complexation in Mixed Nonaqueous Solvents

It is shown, using the formation of silver(I) pyridine (Py) and piperidine (Ppd) complexes in a di-methyl sulfoxide–acetonitrile (DMSO–AN) mixture with different compositions, that an increase in the stability of the complexes with an increase in the acetonitrile content is apparent and caused by the dilution factor. This follows from the more detailed specification of the chemical forms in a mixture of solvents, according to which the complexation is considered as the replacement of the DMSO molecules in the Ag(DMSO)⁺ ₂ solvate ion by the ligands (Py or Ppd molecules). The Ag(DMSO)⁺ ₂ form is more preferential than Ag(AN)⁺ ₂ due to the stronger donor properties of DMSO.     

Preferential Solvation in Mixed Solvents

The Kirkwood–Buff integrals and the volume-corrected preferential solvation parameters for the first solvation shell of binary mixtures of tetrahydrofuran with many organic solvents, calculated from reported thermodynamic data at the temperatures for which these data were available, are reported. The co-solvents include c-hexane, methyl-c-hexane, n-heptane, i-octane, benzene, toluene, ethylbenzene, 1-chlorobutane, dichloromethane, 1,2-dichloroethane, chloroform, 1,1,1-trichloroethane, tetrachlorom-ethane, tetrachloroethene, hexafluoro benzene, ethanol, 1-propanol, 2-propanol, dibutyl ether, acetic acid, acetone, dimethyl sulfoxide, tetramethylene sulfone (sulfolane), acetonitrile, pyrrolidine, and triethylamine. The preferential solvation parameters of these mixtures are discussed in terms of the interactions that occur.     

Cation Exchange Separation of Thallium (I) From Other Elements In Mixed Solvents

Abstract

The cation exchange chromatographic behaviour of thallium (I) on Dowex 50W-X8 was carried out in mixed solvents. Nitric, sulphuric, perchloric acid and their salts, as well as in mixtures of 2 M nitric acid with methanol, ethanol, acetone, dioxane and titrahydrofuran, were studied as the eluants. In comparison with other elements, since thallium was weakly sorbed, it was first eluted, while strongly bound elements like manganese, magnesium, cobalt, indium, gallium, zinc, iron, scandium, yttrium, aluminium, calcium, strontium, and barium were subsequently eluted. The best separations were possible from nitric acid in the presence of non-aqueous solvents such as methanol and ethanol.     

A Series of Rare-Earth Mesoionic Carbene Complexes

We report the synthesis and characterisation of a series of rare-earth mesoionic carbene complexes, [RE{N(SiMe₃)₂}₃{CN(Me)C(Me)N(Me)CH}] ( 3RE , RE=Sc, Ce, Pr, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), greatly expanding the limited library of f-block mesoionic carbene complexes. These complexes were prepared by treatment of the parent RE-triamides with an N-heterocyclic olefin (NHO), where an NHO backbone proton undergoes a formal 1,4-proton migration to the NHO-methylene group. For all RE(III) metals, as expected, quantum chemical calculations suggest only a σ-component to the metal−carbene bonding, in contrast to a previously reported uranium(III) congener where the 5f³ metal engages in a weak π-back-bond to the MIC. All complexes were characterised by static variable-temperature magnetic measurements, and dynamic magnetic measurements reveal that 3Dy and 3Er are field-induced single-molecule magnets (SMMs), with U_eff energy barriers of 35 and 128 K, respectively. Complex 3Dy is, as expected, a poorly performing SMM, but conversely 3Er performs unexpectedly well.     

果糖-水混合溶液中多组分电解质热力学

恒定混合溶液总离子强度I=1.0000 mol•kg－1,改变果糖-水混合溶液中果糖的质量分数w=2.5％、5.0％和7.5％的条件下,应用电动势方法测定下列无液体接界电池(A)和(B)在278.15、283.15、288.15、293.15、298.15、303.15、308.15、313.15、318.15 K等9个温度下的电动势: Pt, H2 (105 Pa)│HCl(m), C6H12O6(w), H2O(1－w)│AgCl-Ag (A) Pt, H2 (105 Pa)│HCl(mA), NaCl(mB), C6H12O6(w), H2O(1－w)│AgCl-Ag (B) 根据测得电池的电动势,计算出混合溶剂中AgCl-Ag电极的标准电极电势和HCl的标准迁移吉布斯自由能、迁移熵和迁移焓; 求出四元混合溶液中HCl的活度系数γA.结果表明在溶液中总离子强度I保持恒定,HCl的活度系数服从Harned规则,进一步讨论了混合物中HCl的介质效应.     

乙二醇和水混合溶剂多组分电解质热力学

在乙二醇和水混合溶剂中恒定乙二醇质量分数w=0.1的条件下，应用经典的电动势方法测定无液体接界电池的电动势: Pt，H2 (105 Pa )│HCl (质量摩尔浓度m)， C2H6O2 (w), H2O (1－w)│AgCl-Ag (A) Pt，H2 (105 Pa )│HCl (mA), NaCl(mB), C2H6O2 (w), H2O (1－w)│AgCl-Ag (B) 根据测得电池(A)的电动势，确定混合溶剂中AgCl-Ag电极的标准电极电势，讨论了HCl的迁移性质.利用电池（B）的电动势，计算出HCl的活度系数γA.结果表明，在溶液中总离子强度保持恒定， HCl的活度系数服从Harned规则.在溶液组成恒定时， lgγA是温度倒数1/T的线性函数. 进一步讨论了混合物中HCl的相对偏摩尔焓和介质效应.     

稀土发光配合物在水溶液中的组装及生物成像研究

稀土配合物具有较窄的f-f跃迁光谱带、较长的荧光寿命及较大的Stokes位移等独特的发光性质,同时其优异的顺磁性,赋予其在生物检测、疾病诊断及生物学活动研究中的重要应用价值.然而,稀土配合物大多水溶解性差,且荧光容易被环境中水分子O-H键的热振动淬灭等,极大地限制了其在水溶液及生物体系中的应用.近年来有研究表明,将稀土...     

The Rise of Phosphaethynolate Chemistry in Early Transition Metals,Actinides, and Rare-Earth Complexes

In the last seven years, chemistry of the phosphaethynolate reagent, Na(OCP)(1,4-dioxane)_2.5, has seen a surge in organic and inorganic chemistry—A renaissance to cyanate chemistry in a new guise. Whereas there have been many reports of main group reactivity with [OCP]⁻, largely from group 14, in more recent times the use of electropositive metals has garnered significant interest given their ability to disguise in various oxidation states. Herein, we report and discuss advances in such studies of [OCP]⁻ with early transition metal and f-block metal scaffolds.     

Ternary Cu2+ Complexes: Stability,Structure, and Reactivity

The driving forces leading to the formation of ternary Cu²⁺ complexes are outlined; they are (i) statistical reasons, (ii) neutralization of charge in the mixed-ligand complexes, (iii) steric factors (bulky groups, ring size of chelates), and (iv) formation of π bonds. The last point is important for achieving a large stability, as well as for the observation of discriminating qualities. An additional stability increase may possibly be achieved through a direct interaction between the two ligands bound to the same metal ion, i.e. Schiff base formation, hydrogen bonding or a charge-transfer relation. The latter leads to distinct structures, i.e. metal ion-bridged charge-transfer complexes. The relation between stability and structure on the reactivity of mixed-ligand complexes is emphasized. The relevance of the results for mixed-ligand complexes containing metal ions other than Cu²⁺ is briefly outlined.     

Volumetric Properties of Tetraphenylporphyrin, Octaethylporphyrin, and Their Metallo Complexes in Organic Solvents

Densities, apparent molar volumes, and partial molar volumes were determined for (a) tetraphenylporphyrin, H₂TPP, and ZnTPP in several organic solvents and (b) H₂TPP, octaethylporphyrin, H₂OEP, and the metallo complexes MTPP and MOEP (where M = Zn, Cu, Ni, Pd, Cd, Ag) in benzene and chloroform solutions at 25°C. The effect of solute–solvent interactions on molecular packing was followed by examining changes in the ratios of van der Waals volumes to the partial molar volumes of solute and solvent. Using this method, the volumetric properties of H₂TPP were compared with those of the macromolecules 18-crown-6-ether, cryptand-222, and C60. For benzene solutions of MOEP metallo complexes, the linear dependence between the partial molar volumes and the half-wave oxidation potentials was determined. It was found that the partial molar volumes of MTPP in the chloroform solution correlate linearly with the distance between the metal atom and the nitrogen atom of the pyrrole moiety of the metallo complex.