Cu(Ⅱ)脱乙酰壳聚精配位聚合物的配位数

IR,ESR和XPS的测试结果表明,脱乙酰壳聚糖(简记CS)膜在铜氨水溶液浸渍过程中Cu(Ⅱ)既与CS发生配位反应形成Cu(Ⅱ)-CS配位聚合物,也产生吸附作用.ESR谱示出CuCl_2·2H_2O与Cu(Ⅱ)-CS膜中的Cu(Ⅱ)均含有一个单电子,可以利用XPS的Shake-up效应研究Cu(Ⅱ)-CS配位聚合物的配位数,所得结果为4.又以同样的方法研究Cu(Ⅱ)-聚乙烯醇(简记PVA)配位聚合物的配位数,发现Cu(Ⅱ)是以低自旋状态的dsp~2杂化空轨道与PVA的羟基氧配位,其配位数也是4,这与资料所报道的一致,从而间接地验证了此方法研究Cu(Ⅱ)-CS配位聚合物配位数的可靠性.     

Coordination properties of Cu(II) and Ni(II) ions towards the C-terminal peptide fragment -TYTEHA- of histone H4

In order to reveal more information about the toxicity caused by metals and furthermore their influence to the physiological metabolism of the cell, the hexapeptide model Ac-ThrTyrThrGluHisAla-am representing the C-terminal 71-76 fragment of histone H4 which lies into the nucleosome core, was synthesized. A combined pH-metric and spectroscopic UV-VIS, EPR, CD and NMR study of Ni(II) and Cu(II) binding to the blocked hexapeptide, revealed the formation of octahedral complexes involving imidazole nitrogen of histidine, at pH 5 and pH 7 for Cu(II) and Ni(II) ions respectively. In basic solutions a major square-planar 4 N Ni(II)-complex, adopting a {N(Im), 3N(-)} coordination mode, was formed. In the case of Cu(II) ions, a 3 N complex, involving the imidazole nitrogen of histidine and two deprotonated amide nitrogens of the backbone of the peptide, at pH 7 and a series of 4 N complexes starting at pH 6.5, were suggested. In addition Ni(II)-mediated hydrolysis of the peptide bond-Tyr-Thr was evident following our experimental data.     

Coordination compounds of Co(II), Ni(II) and Cu(II) with capric acid hydrazide

The reaction of aquo-ethanolic solutions of Co(II), Ni(II) and Cu(II) salts and ethanolic solution of capric acid hydrazide (L) yielded paramagnetic, high-spin bis- and tris(ligand) chelate complexes. The tris(ligand) complexes, [ML ₃]X ₂·nH₂O [M=Co(II), Ni(II);X=NO ₃ ^– , ClO ₄ ^– , 1/2SO ₄ ^2– ], have an octahedral structure formed on account of the bidentate (NO) coordination of three neutral hydrazide molecules. In the bis(ligand) complexes,ML ₂(NCS)₂ [M=Co(II), Ni(II)] and CuL ₂ X ₂·nH₂O (X=NO ₃ ^– , ClO ₄ ^– and 1/2SO ₄ ^2– ), the oxoanions and NCS^– take also part in coordination. The complexes have been characterized by elemental analysis, IR spectra, magnetic measurements, molar conductivity and TG analysis.

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Caprinsäurehydrazid-Komplexe von Co(II), Ni(II) und Cu(II)

Zusammenfassung Durch die Reaktion von wäßrig-ethanolischen Lösungen von Co(II)-, Ni(II)-und Cu(II)-Salzen mit einer ethanolischen Lösung von Caprinsäurehydrazid (L) wurden paramagnetische high-spin Bis- und Tris-Ligand-Chelatkomplexe erhalten. Tris-Ligand-Komplexe des Typs [ML ₃ X ₂·nH₂O [M=Co(II), Ni(II);X=NO ₃ ^– , ClO ₄ ^– , 1/2SO ₄ ^2– ], die eine oktaedrische Struktur besitzen, entstehen durch die Koordination von drei neutralen zweizähnigen (NO)-Hydrazidmolekülen. Bei den Bis-Ligand-KomplexenML ₂(NCS)₂ [M=Co(II), Ni(II)], sowie bei den Bis-Ligand-Komplexen CuL ₂ X ₂·nH₂O (X=NO ₃ ^– , ClO ₄ ^– , 1/2SO ₄ ^2– ) nehmen bei der Koordination außer Hydrazid auch die Säurereste teil. Die Komplexe wurden durch Elementaranalyse, IR-Spektren, magnetische Messungen, molare Leitfähigkeit und TG-Analysen charakterisiert.

     

Complexing properties of methyl and phenyl glycine derivatives in their compounds with H+, Ni(II), Cu(II), and Zn(II)

The influence of the solvent and the substituents on the complexing properties of methyl and phenyl glycine derivatives is discussed. On the basis of a computer analysis of potentiometric titration results, the composition and the stability constants of the complexes ofN-methylglycine,N,N-dimethylglycine,N-phenylglycine and phenylglycine with H⁺ and with Ni(II), Cu(II), Zn(II) were determined. The ligand-metal coordination mode as well as the zwitterion level in percent in ligand/proton systems were determined by spectral analyses and equilibria studies.

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Komplexbildung der Methyl- und Phenylglycin-Derivate in ihren Verbindungen mit dem Proton und Ni(II), Cu(II) und Zn(II)

Zusammenfassung Der Einfluß des Lösungsmittels und der Substituenten auf die komplexbildenden Eigenschaften der Methyl- und Phenylglycin-Derivate wird diskutiert. Anhand einer Computer-Analyse von potentiometrischen Daten wurden die Zusammensetzung und die Beständigkeitskonstanten der Komplexe vonN-Methylglycin,N,N-Dimethylglycin,N-Phenylglycin und Phenylglycin mit H⁺, Ni(II), Cu(II) und Zn(II) festgestellt. Mittels spektroskopischer Methoden und Gleichgewichtstudien wurde der Koordinationstyp des Liganden mit dem Metall festgestellt sowie der Prozentanteil des Zwitterions im Ligand/Proton-System.

     

Coordination polymer incorporating cobalt(II) and glycine acid: structure and magnetism

We report the structure and magnetism of a cobalt(II) compound with glycine acid, Co(C₂H₄NO₂)₂ · H₂O (1). It crystallizes in the orthorhombic system, space group P2(1)2(1)2(1) with a = 5.2301(10) Å, b = 10.837(2) Å, c = 13.542(3) Å, R ₁ = 0.0448, wR ₂ = 0.1151. In 1, Co(II) has a slightly distorted square-pyramidal geometry defined by two O atoms and two N atoms from two glycine ligands, and by one O atom from an aqua ligand in the apical position. The molecules form a three-dimensional supramolecular network through O–H ··· O and N–H ··· O hydrogen bonds. Magnetic characterization shows 1 exhibits a negative Curie–Weiss constant and dominant spin-orbit coupling for Co(II).     

Site-specific polymer attachment to a CCL-5 (RANTES) analogue by oxime exchange

A synthetic strategy that allows for the site-specific attachment of polymers such as poly(ethylene glycol) (PEG) to protein pharmaceuticals is described. PEG was attached to a 67-amino acid fully synthetic CCL-5 (RANTES) analogue at its GAG binding site both to reduce aggregation and to increase the circulating lifetime. Effective protection of an Aoaa chemoselective linker during peptide assembly, total chemical protein synthesis, and protein folding was achieved with an isopropylidene group. Mild deprotection of the resulting folded synthetic protein and subsequent polymer attachment occur without interference with the native folded structure and activity.     

Spectroscopic and theoretical study of Cu(II), Zn(II), Ni(II), Co(II) and Cd(II) complexes of glyoxilic acid oxime

The paper presents a detailed experimental and theoretical study of five metal complexes of glyoxilic acid oxime (gaoH2), Cu(gaoH)2(H2O)2 (1), Zn(gaoH)2(H2O)2 (2), Co(gaoH)2(H2O)2 (3), Ni(gaoH)2(H2O)2 (4) and [Cd(gaoH)2(H2O)2].H2O (5). The electronic and vibrational spectra were measured and discussed as to the most sensitive to the M-L binding bands. Two different types of coordination were considered for gaoH- ligand: bidentate through the carboxylic oxygen and oxime nitrogen in 1-4 and mixed bidentate and bridging through the COO group in 5. It is shown that the spectral behavior of the nu(COO) modes can be used to predict bridging ligand coordination. DFT(B3LYP/6-31++G(d,p)) calculations on model compounds: neutral, anionic and radical forms of gao and Cu(gaoH)2, have been carried out to correlate geometries, electronic and vibrational structures. The results obtained were used to assist the electronic and vibrational analysis of the complexes studied. The effect of the metal-ligand interactions (electrostatic and covalent) on the geometry structure of the ligand was investigated.     

O and N NMR studies of the Co(II), Cu(II) and Mn(II) complexes of glycine in aqueous solution

The ¹⁷O and ¹⁴N paramagnetic relaxation rates and chemical shifts of glycine as well as of water, in aqueous solutions of Co(II), Cu(II), and Mn(II) were measured as a function of pH, temperature and metal ion concentration; the relaxation results were fitted to a theoretical equation linking the Swift-Connick equation to the stability constants of all major complexes in equilibrium. As a result, the stability constants of all major complexes were determined, and from the temperature-dependent measurements the thermodynamic parameters for some of these complexes were also calculated. In addition to the bidentate complexes ML⁺, ML₂ and ML₃⁻, monodentate complexes of the type MHL²⁺ and M(HL)₂²⁺, mixed complexes of the type MHL₂⁺ and MHL₃ were also considered. In the case of the Cu(II)-glycine system at pH> 12 two additional species were considered, namely ML₂(OH)⁻ and ML₂(OH)₂²⁻, suggested by the drastic reduction of the paramagnetic broadening in that pH range.     

钴(Ⅱ)和铜(Ⅱ)膦酸配位聚合物的热、磁性能

3-氨基-1-羟基丙叉-1,1-二膦酸与钴或铜离子的水热反应得到新的配聚物Co2(NH3CH2CH2C(OH)(PO3)(PO3H))2·2H2O (1) 和Cu3{[NH3CH2CH2C(OH)(PO3)2](H2O)2} (2).研究了两个配合物的热稳定性,采用变温磁化率研究了在5-300 K范围内的磁性能. 结果表明:在配合物1中,钴离子间存在着弱的反铁磁偶合作用,理论拟合值为J=-2.1 cm-1,g=2.18;配合物2中,铜离子间的磁作用较复杂.     

Studies of Electrode Reactions and Coordination Geometries of Cu(I) and Cu(II) Complexes with Bicinchoninic Acid

Bicinchoninic acid (BCA) is widely used for determining the valence state of copper in biological systems and quantification of the total protein concentration (BCA assay). Despite its well‐known high selectivity of Cu(I) over Cu(II), the exact formation constants for Cu(I)(BCA)₂³⁻ and Cu(II)(BCA)₂²⁻ complexes remain uncertain. These uncertainties, affect the correct interpretations of the roles of copper in biological processes and the BCA assay data. By studying the voltammetric behaviors of Cu(I)(BCA)₂³⁻ and Cu(II)(BCA)₂²⁻, we demonstrate that the apparent lack of redox reaction reversibility is caused by an adsorption wave of Cu(II)(BCA)₂²⁻. With the adsorption wave identified, we found that the Cu(I)/Cu(II) selectivity of BCA is essentially identical to another popular ligand, bathocuproinedisulfonic acid (BCS). Density functional theory calculation on the geometries of Cu(I)(BCA)₂³⁻ and Cu(II)(BCA)₂²⁻ rationalizes the preferential Cu(I) binding by BCA and the strong adsorption of the Cu(II)(BCA)₂²⁻ complex at the glassy carbon electrode. Based on the shift in the standard reduction potential of free Cu(II)/Cu(I) upon binding to BCA, we affirm that the formation constants for Cu(I)(BCA)₂³⁻ and Cu(II)(BCA)₂²⁻ are 10^17.2 and 10^8.9, respectively. Therefore, BCA can be chosen among various ligands for effective and reliable studies of the copper binding affinities of different biomolecules.     

Coordination compounds of Co(II), Ni(II), and Cu(II) valerates and benzoates with semicarbazide

Complexes of Co(II), Ni(II), and Cu(II) valerates and benzoates with semicarbazide were prepared. The compounds were characterized by chemical analysis, X-ray phase analysis, IR spectroscopy, diffuse reflection spectroscopy, and thermal gravimetric analysis.     

Coordination properties of tridentate (N,O,O) heterocyclic alcohol (PDC) with Cu(II). Mixed ligand complex formation reactions of Cu(II) with PDC and some bio-relevant ligands

The formation equilibria of copper(II) complexes and the ternary complexes Cu(PDC)L (PDC=2,6-bis-(hydroxymethyl)-pyridine, HL=amino acid, amides or DNA constituents) have been investigated. Ternary complexes are formed by a simultaneous mechanism. The results showed the formation of Cu(PDC)L, Cu(PDC, H(-1))(L) and Cu(PDC, H(-2))(L) complexes. The concentration distribution of the complexes in solution is evaluated as a function of pH. The effect of dioxane as a solvent on the protonation constant of PDC and the formation constants of Cu(II) complexes are discussed. The thermodynamic parameters DeltaH degrees and DeltaS degrees calculated from the temperature dependence of the equilibrium constants are investigated.     

A trinucleating ligand based on 1,8-naphthalenediol: synthesis, structural and magnetic properties of a linear Cu(II)Cu(II)Cu(II) complex

The extension of Robson-type ligands from dinucleating based on 2,6-diformylphenol to trinucleating based on 2,7-diformyl-1,8-naphthalenediol is demonstrated by the synthesis, structural and magnetic characterization of the first trinuclear Cu(II) complex using a 1,8-naphthalenediol derived ligand.     

Coordination chemistry of some new Cu(II), Ni(II) and Co(II) macroacyclic (N2O4) Schiff base complexes: X-ray crystal structure of Cu(II) complex

Six new Cu(II), Ni(II) and Co(II) macroacyclic Schiff base complexes [M^II(H₂L)](ClO₄)₂ (L = L¹ and L²) (I–VI) were prepared by the reaction of two new N₂O₄ Schiff base ligands in equemolar ratios. The ligands H₂L¹ and H₂L² were synthesized by reaction of 2-[2-(2-formyl phenoxy)ethoxy]benzaldehyde (A¹) and/or 2-[2-(3-formylphenoxy)propoxy]benzaldehyde (A²) and ethanol amine and characterized with IR and ¹H, ¹³C NMR spectroscopy. All complexes were characterized by microanalysis, IR and mass spectrometry, whereas complex I was also characterized by single crystal X-ray (CIF file CCDC no. 1020055). The X-ray structure of complex I revealed that all nitrogen and oxygen atoms of ligand (N₂O₄) have coordinated to the metal ion. However, Cu²⁺ ion is in six coordination environment that can bedescribed as a distorted octahedral geometry.     

Coordination enhancement of single-molecule magnet behavior of Tb(III)–Cu(II) dinuclear systems

Tb(III)–Cu(II) based single-molecule magnets (SMMs) were synthesized to investigate the relationship between magnetic anisotropy and the symmetry of the ligand field, by the reaction of [TbCu(o-vanilate)₂(NO₃)₃] with 2,2-dimethyl-1,3-propanediamine (3), followed by the reaction of one another equivalent of o-vaniline (4). Both complexes behave as SMM in the temperature range of 2.8–4.0 K (3) and 2.8–5.2 K (4), showing semi-circle shapes of Cole–Cole plots with α parameters in the ranges of 0.27–0.41 and 0.11–0.32. The energy barriers Δ/k_B for the spin flippings were estimated from the Arrhenius plots to be 29(2) K for 3 and 32.2(6) K for 4, respectively.