Synthesis and Crystal Structure of catena-Poly[[[2,4-dibromo-6-[（3-dimethylaminopropylimino）-methyl]phenolato]copper（II）]-μ-azido]

A novel end-to-end azido-bridged polynuclear Schiff-base copper（II） complex, [Cu（C12H15Br2N2O）（N3）]n, was prepared and characterized by elemental analysis, IR spectra, and single-crystal X-ray diffraction. The crystal belongs to the orthorhombic system, space group Pbcn with a = 24.588（5）, b = 10.377（2）, c = 13.022（3） A, V= 3322.6（12） A^3, Z = 8, Dc = 1.874 g/cm^3, Mr = 468.65, λ（MoKa） = 0.71073 A,μ = 6.130 mm^-1, F（000） = 1832, R = 0.0637 and wR = 0.1176. The Cu atom in the complex is five-coordinated in a square pyramidal geometry by three donor atoms of the Schiff-base ligand, and two N atoms from two bridging azide ligands. The [2,4-dibromo-6-[（3-dimethylaminopropylimino）methyl]phenolato]copper（II） units are linked by the bridging azide ligands, giving zigzag polymeric chains with backbones of the [--Cu-N-N-N--Cu]n type running along the b axis.     

Formation of dinuclear copper(II) complex with N,N,N',N'-tetrakis(2-pyridylmethyl)-1,2-ethanediamine in aqueous solution

The polynuclear complexation of divalent 3d transition metal cations with N,N,N',N'-tetrakis(2-pyridylmethyl)-1,2-ethanediamine (tpen) in aqueous solution was investigated. It was found that copper(II) forms a dinuclear complex with tpen in an aqueous solution containing chloride. The composition of the complex was determined as Cu(2)Cl(2)(tpen)(2+). Furthermore, the stability constant of the complex was determined and its structure was postulated to be (mu-Cl)(2).     

Anion binding to a tetracopper resorcinarene-based complex

UV–vis and electron paramagnetic resonance (EPR) spectroscopic studies have been carried out on the multinuclear copper(II) complex Cu₄BpaRes. The copper atoms are in a tetragonal distorted geometry with nitrogens from bispicolylamine (Bpa) coordinating in the equatorial plane and water molecules or anions completing four coordination sites. The interaction of anions with this polynuclear copper complex in aqueous solution supports the formation of different complex species, which depend on the type and the concentration of the anions. In the presence of excess anions, frozen solution EPR parameters show the formation of species in which the in-plane coordination is characterised by the presence of three nitrogen atoms coming from the ligand and a donor atom from the specific anion. For the bidentate anion ligands and especially for malonate, UV–vis titrations indicate the formation of a 1:4 (Cu₄BpaRes:anion) species. EPR experiments support the formation of such a species and indicate that the four copper centres are equivalent and reach penta-coordination via the coordination of both oxygens from the bidentate ligand.     

Model selection for complex systems involving polynuclear species

1-hydroxyethylidene-1,1-bisphosphonic acid (HEDP) is a phosphonate chelate with several diagnostic and therapeutic applications. Previous studies have indicated that calcium complex aggregation occurs in the basic range of pH; results from this study indicate that complex aggregation occurs throughout the physiological range of pH as well. Calcium complex formation data were used for PQ analyses and plots of the derivative of Z with respect to total diphosphonate at constant free calcium ion concentration were shown to provide valuable information with regard to model selection. A link-addition stepwise complex formation model was shown to be most appropriate; a robust feature of all aggregate formation models examined is a strong pH dependence of polynuclear complex formation in the pH range 5.5–7.0.     

Copper(II) complexes based on <Emphasis Type="Italic">N</Emphasis>-(2-carboxyethyl)alkanolamines

A comparative study of the copper metallocenter coordination sphere is carried out for a series of N-substituted β-alaninate ligands in condensed phase. For the elucidation of the effect of regular changes in dentate properties of a ligand on the complex structure, N-(bis(hydroxymethyl)methyl)-β-alanine and its copper(II) complex are specially synthesized and the complex structure is studied by the method of X-ray structural analysis. For determination of structure of the complexes in aqueous solution is applied electron spin resonance spectroscopy. Structural characteristics of β-alaninate and glycinate complexes are compared. The factors promoting formation of polynuclear complexes are considered.     

Copper(II) complexation by (pyridinyl)aminomethane-1,1-diphosphonic acid derivatives; spectroscopic and potentiometric studies

The complex formation between copper(II) and (pyridinyl)aminomethane-1,1-diphosphonic acid derivatives was studied by means of pH-potentiometry, spectroscopic methods (UV-Vis, EPR) and mass spectrometry (MS). The bisphosphonate ligands form polynuclear Cu₃H_xL₃ (x = 4 ,3, 2, 1, 0, −1) species besides the mononuclear 1:1 and 1:2 metal-to-ligand molar ratio complexes. Two phosphonate groups are basic binding sites for the metal ion. It is suggested that in the polynuclear complexes the ligands adopt chelating and bridging modes via the four oxygen atoms of the two phosphonate groups.     

Complex Formation by Galacturonic Acid with Copper(II) and Neodymium(III) Ions in Water Solution

Complex formation by galacturonic acid with copper(II) ion in water solution is studied by themethods of EPR spectroscopy. At the pH > 3 the EPR signal (g 2.174) confirms the complex formation at theligand carboxylic group. The following complex formation parameters are measured: equilibrium constant'g factor, hyperfine coupling constant, average complex lifetime. From the data of electron spectra invisible region the complex composition and stability constant is defined for copper(II) and neodymium(III).     

Room-temperature phosphorescence of acenaphthene in aerated solutions in the presence of bromoalcohols and γ-cyclodextrin

The inclusional complexation between γ-cyclodextrin and acenaphthene in aqueous solution was investigated by spectroscopic techniques. A 1:1 complex was detected and its formation constant was determined. After adding bromoalcohols such as 2,3-dibromopropane-1-ol or 2-bromoethanol both a decrease of the fluorescence and an enhancement of the room-temperature phosphorescence (RTP) of acenaphthene were observed. The RTP signals from acenaphthene included in γ-cyclodextrin were optimized. The apparent formation constant of the ternary γ-cyclodextrin-acenaphthene-2,3-dibromopropane-1-ol complex was determined from RTP data. On the other hand, the inclusion complex formed between γ-cyclodextrin, acenaphthene and 2-bromoethanol was found to be very labile and its equilibrium constant could not be determined with accuracy. Large RTP signals were obtained in both ternary systems, even in the absence of sodium sulfite as deoxygenant agent. This fact would indicate that in these complexes the acenaphthene is protected from the action of quenchers such oxygen.     

Azido derivatives of dinuclear copper(II) and 1D polynuclear nickel(II) complexes containing an unsymmetrical bidentate amine: synthesis,crystalline architecture,and magnetic behavior

Transition Metal Chemistry - Dinuclear copper(II) complex [Cu2(L)2(μ2-1,1-N3)2(N3)2] (1) with double μ1,1-azido bridges and polynuclear nickel(II) complex...     

The role of the solvent in equilibrium and kinetic aspects of metal chelate extractions

Equilibria and kinetics for the extraction of nickel(II) and copper(II) by 2-hydroxy-5-nonylbenzophenone oxime (LIX 65N) in seven organic solvent systems were studied in order to test the validity of several hypotheses related to the role of the solvent in equilibrium and kinetic aspects of metal chelate extraction. For the nickel—LIX 65N system, the extraction constant is essentially independent of the solvent system, whereas for the copper—LIX 65N system, the extraction constant is not independent of solvent; this indicates that while the stoichiometry of the nickel chelate remains the same in all solvents, that of copper does not. The observed rate constant for the nickel—LIX 65N extraction was found to vary inversely with the LIX 65N distribution constant as predicted from a mechanism involving slow formation of the 1:1 complex. The observed reaction rate constant for the copper—LIX 65N varied inversely with the square of the distribution constant, also in accordance with the previously postulated mechanism of the slow formation of the 2:1 copper complex. This study, therefore, unequivocally eliminates the interfacial mechanism in favor of the homogeneous chemical reaction mechanism for the extraction of metal ions by LIX 65N, as well as by other similar high-molecular-weight extractants.     

Heptanuclear hydroxo-bridged copper cluster of the dicubane-like type: structural and magnetic characterizations of [Cu7(OH)6Cl2(pn)6(H2O)2](C(CN)3)4Cl2 (pn = 1,3-diaminopropane)

A new polynuclear copper(II) complex [Cu7(OH)6Cl2(pn)6(H2O)2](C(CN)3)4Cl2 with hydroxo-bridging ligands has been prepared; the centrosymmetric cluster cation can be described as two Cu4O3Cl distorted cubane units sharing one copper cation.     

Expressions for Enthalpies of Concurrent Polynuclear Complex Formation Reactions in Two-Phase Aqueous Systems

The paper presents a new thermodynamic approach to studying polynuclear complex formation reactions in multicomponent two-phase systems, solid phase plus saturated aqueous solution, under real conditions. The quintessence of this developed approach consists in the thermodynamic analysis of concurrent reactions on the basis of the introduced notion of a generalized reaction equation. The formation of complex polynuclear species is characterized by certain peculiarities in the behavior of studied two-phase heterogeneous systems. The formation of polynuclear complexes of the metal ion with a complexing agent leads to expressions for the enthalpy ?H and heat capacity ?C_p as certain concentration functions, which are normative multipliers, referring these thermochemical quantities to one mole of the metal ion. It is shown that one of these functions, Φ, characterizes the degree of formation of polynuclear complexes. In the case of concurrent formation of mono- and polynuclear complexes, the derived expressions are useful in distinguishing separate contributions of individual complex formation reactions to the ?H and ?C_p of the overall process.     

Mechanism of catalytic oxidation of water-lipid substrate

The processes of ethyl oleate water-emulsion oxidation in the presence of copper (II) complexes with α-alanine as a catalyst were investigated spectroscopically. UV spectra of the samples revealed the competitive nature of the formation and decomposition of hydroperoxides in the course of oxidation. Vis spectra of the aqueous phase revealed the constant presence of copper (II) complex with α-alanine and the formation of a similar complex with copper (I) in organic phase. The involvement of these complexes in the reactions of chain nucleation and decay of hydroperoxides is suggested.     

稀土元素及其显色效应的研究 VI:镧-偶氮氯膦III——-钇混合多核配合物的生成

The interference of lanthanum in the spectrophotometric determination of yttrium in the form of β-type complex with chlorophosphonazo III (CPA III) is proved to be a cocoloration effect. It is due to the formation of a mixed polynuclear complex between CPA III and lanthahum-yttrium with a cyclic structure. The composition of the complex has been established to be La:CPA III:Y = 1:2:1 by the method of molar ratio. The optimal conditions for the formation of polynuclear complex and influence factors have also been studied. A "replacement type" reaction is proposed to account for the cocoloration effect.     

A new graphic method for differentiating mononuclear and polynuclear complexes and for determining their stability constants

A new graphical method is proposed for differentiating mononuclear and polynuclear complexes as well as for determining the stability constant of any complex A(m)B(n). The method is based on the effect of dilution on the degree of dissociation of the complex. The resultant mathematical equation provides a simple graphical calculation which leads to the determination of the stability constant and also the molar absorptivity of the complex.     

Complex formation of 5-hydroxyorotic acid with copper(II) ions in water solutions

Complex formation of 5-hydroxyorotic acid with copper(II) chloride in water solution is studied by electron spectroscopy. The composition of the complex was established spectrophotometrically by molar ratio method and confirmed by elemental analysis. The constant of complex formation was calculated. By the IR spectroscopy the electron-donating centers of 5-hydroxyorotic acid taking part in coordination with metal ion were established. The structure of the obtained complex was suggested.     

Spectrophotometric determination of copper in alloys using naphthazarin

Naphthazarin (5,8-dihydroxy-1,4-naphthoquinone; Naph) is proposed as a chromogenic reagent for the spectrophotometric determination of copper(II). The polynuclear complex has a mole ratio of Cu:Naph=4:6 in a 50% v/v ethanol/water medium containing 0.1 M ammonium acetate and 1.5% (w/v) sodium dodecyl sulfate. The copper-naphthazarin complex shows an absorption maximum at 330 nm with a molar absorptivity of 1.84x10(4) l mol(-1) cm(-1). Beer's law is obeyed up to 4.5 ppm of copper(II). The method was applied for copper determination in alloy samples with satisfactory results.     

用线性回归与单纯形优化法研究配合物的组成

本文讨论了用线性回归和单纯形最优化法确定配合物实际组成的两种方法。这两种方法简单方便,既适用于水溶液也适用于非水溶液。     

Speciation and structure of copper(II) complexes with histidine-containing peptides in aqueous medium: a combined potentiometric and spectroscopic study

The complex formation between copper(II) and some histidine-containing peptides has been investigated by means of potentiometric and spectroscopic measurements. Due to the interesting co-ordination mode towards copper(II), peptides with histidyl residue located in second position from the N-terminal amino group have been chosen. The stability constants evaluation has been performed by both pH-metric and ESR (room temperature) measurements; in this context a suitable computer program for the calculation of both stability constant values and the ESR spectrum for each complex has been written. Visible spectrophotometric and circular dichroism spectra, together with the isotropic ESR parameters, were used in order to propose a structure for each complex having a significant percentage of formation in solution.     

Syntheses,crystal structures,and urease inhibitory properties of copper(II) and zinc(II) complexes with 2-bromo-4-chloro-6-[(2-dimethylaminoethylimino)methyl]phenol

A new copper(II) complex, [CuL(μ _1,1-N₃)] _n (1), and a new zinc(II) complex, [ZnL(μ ₂-acetato-O, O′)₂] _n (2) (HL = 2-bromo-4-chloro-6-[(2-dimethylaminoethylimino)methyl]phenol), were prepared and characterized by elemental analyses, infrared spectroscopy, and single-crystal X-ray diffraction. Complex 1 is an end-on azide-bridged polynuclear copper(II) complex and 2 is a syn–anti bidentate acetate-bridged polynuclear zinc(II) complex. Each metal in the complex is five-coordinate with square-pyramidal geometry. Complex 1 shows good urease inhibitory properties, while 2 does not.