Ruthenium(III) and ruthenium(III)-aminopolycarboxylic acid chelate-catalyzed oxidation of ascorbic acid by molecular oxygen

The kinetics of Ru(III) ion, Ru(III)-EDTA (1:1) and Ru(III)-IMDA (1:1) catalyzed oxidation of ascorbic acid by molecular oxygen are investigated at 25°C, μ = 0.1 M KNO₃, in the pH range 1.50 to 2.75. First-order kinetics were observed with respect to the concentrations of Ru(III) ion, Ru(III)-EDTA, Ru(III)-IMDA and ascorbic acid. The rate of oxidation was found to be inversely proportional to the hydrogen ion concentration. One-half-order and zero-order dependences with respect to the concentration of molecular oxygen were found in the cases of Ru(III) ion and Ru(III)-amino-polycarboxylic acid chelate-catalyzed oxidations, respectively. An inverse relationship was found between the stability and catalytic activity of the Ru(III) chelates of aminopolycarboxylic acids. The catalytic activities of Ru(III) ion and its chelates increase in the order Ru(III)-EDTA < Ru(III)-IMDA < Ru(III). The mechanistic implications of the oxidations catalyzed by Ru(III) ion and its chelates are discussed.     

Unique crown thioether complexes of f elements: the crystal structure of U(III) and La(III) complexes of 1,4,7-trithiacyclononane

The crystal structures of the first U(III) complex of a crown thioether and of its La(III) analog have been determined; a stronger M-S interaction is observed for U(III) with respect to La(III) and Ce(III) in solution and in the solid state.     

Synthesis,characterization and cytotoxic/cytostatic activity of Sm(III) and Gd(III) complexes

New Sm(III) and Gd(III) complexes of deprotonated 4-hydroxy-3[1-(4-nitrophenyl)-3-oxobutyl]-2H-1-benzopyran-2-one (Acenocoumarol) were synthesized and characterized using FT-IR, FT-Raman, NMR spectra, and elemental analyses. The vibrational study gave evidence for the coordination of ligand to lanthanide ions. The ligand and its lanthanide(III) complexes were tested for their cytotoxic/cytostatic activity against two tumor cell lines and peritoneal mouse macrophages. The Sm(III) and Gd(III) complexes exhibit good activity against melanoma B16 and fibrosarcoma L929 and are stronger inhibitors of tumor cell proliferation than the ligand. Besides their cytotoxicity to tumor cells, Acenocoumarol and its gadolinium(III) and samarium(III) complexes modulate NO generation in activated macrophages.     

Equilibrium studies on chromium(III) complexes of salicylic acid and salicylic acid derivatives in aqueous solution

The complexes of chromium(III) ion formed by salicylic acid, SA(H(2)L), and its derivatives (H(2)L): 5-nitrosalicylic acid (5-NSA), 5-sulphosalicylic acid (5-SSA) were investigated by means of potentiometry and spectroscopy, at 25 degrees C and in ionic strength of 0.1 M KNO(3) and 0.1 M KCl, respectively. Over the acidic pH range, the coordination of Cr(III) ion to SA and its derivatives in 1 : 1 mole ratio occurs, CrL(+) type complex is formed. In the excess of ligand, the coordination of the second ligand molecule is somewhat hindered; as a result CrL(HL) type complex occurs. Their existences were verified and their formation constants were determined. At near neutral pH, CrL(OH) and CrL(HL)(OH)(-) type hydroxo complexes formed by hydrolytic equilibria and their formation constants were also defined. The stabilities of Cr(III) complexes of SA and its derivatives decrease in the following order: SA>5-SSA>5-NSA. The formation constants of Cr(III) complexes of SA and its derivatives are in comparable ranges with the corresponding complexes of the 2,x-dihydroxybenzoic acid (2,x-DHBA) of Cr(III) ion. The stabilities of SA complexes for V(IV), Cr(III) and Fe(III) ions that have similar ionic radii, increase in the order VOL相似文献   

Theoretical and Experimental Vibrational Characterization of Biologically Active Nd(III) Complex

The neodymium(III) complex of orotic acid (HOA) was synthesized and its structure determined by means of analytical and spectral analyses. Detailed vibrational analysis of HOA, sodium salt of HOA, and Nd(III)–OA systems based on both the calculated and experimental spectra confirmed the suggested metal–ligand binding mode. Significant differences in the IR and Raman spectra of the complex were observed as compared to the spectra of the ligand. The calculated vibrational wavenumbers, including IR intensities and Raman scattering activities, for the ligand and its Nd(III) complex were in good agreement with the experimental data. The vibrational analysis performed for the studied species, orotic acid, sodium salt of orotic acid, and its Nd(III) complex helped to explain the vibrational behaviour of the ligand’s vibrational modes, sensitive to interaction with Nd(III). In this paper we also report preliminary results about the cytotoxicity of the investigated compounds. The cytotoxic effects of the ligand and its Nd(III) complex were determined using the MTT method on different tumour cell lines. The screening performed revealed that the tested compounds exerted cytotoxic activity upon the evaluated cell lines.     

Synthesis of lactide from lactic acid and its esters in the presence of rare-earth compounds

A procedure is described for the synthesis of lactide by dehydration of L-lactic acid and subsequent depolymerization of its oligomer mixture in the presence of yttrium(III) and praseodymium(III) oxides, as well as of cerium(III) chloride heptahydrate. The catalytic activity of yttrium and praseodymium sesquioxides was determined at different temperatures at the oligomerization and deoligomerization stages. Ethyl lactate was prepared in the presence of Purolite C100 MB cation exchange resin and subjected to oligomerization followed by thermal decomposition of oligoester and oligolactic acid mixture in the presence of yttrium(III) and praseodymium(III) oxides and aqueous cerium(III) chloride.     

四（对—羟基）苯基卟啉配合物的傅里叶变换红外光声光谱

四（对-羟基）苯基卟啉（H2THPP）不仅能作为分析试剂，而且有一定的抗癌活性，还可作为合成卟啉类液晶材料的中间体．这种配体及其配合物由于颜色深、透光性能差和散射较强，用普通红外光谱法开展其振动光谱研究存在一定的困难．我们在用红外光声光谱（FTIR－PAS）技术[1]成功地研究了部分过渡金属、稀土金属叶琳配合物的基础上[2，3]，测试并研究了H2THPP及其Cr（III）、Mn（III）、Fe（III）、Co（II）、Ni（II）、Cu（II）、Zn（II）配合物在3700～200cm－1范围内的FTIR－PAS．对主要谱带进行了经验归属，讨论了配…     

Experimental evidence for cobalt(III)-carbene radicals: key intermediates in cobalt(II)-based metalloradical cyclopropanation

New and conclusive evidence has been obtained for the existence of cobalt(III)-carbene radicals that have been previously proposed as the key intermediates in the underlying mechanism of metalloradical cyclopropanation by cobalt(II) complexes of porphyrins. In the absence of olefin substrates, reaction of [Co(TPP)] with ethyl styryldiazoacetate was found to generate the corresponding cobalt(III)-vinylcarbene radical that subsequently dimerizes via its γ-radical allylic resonance form to afford a dinuclear cobalt(III) porphyrin complex. X-ray structural analysis reveals a highly compact dimeric structure wherein the two metalloporphyrin units are arranged in a face-to-face fashion through a tetrasubstituted 1,5-hexadiene C(6)-bridge between the two Co(III) centers. The γ-radical allylic resonance form of the cobalt(III)-vinylcarbene radical intermediate could be effectively trapped by TEMPO via C-O bond formation to give a mononuclear cobalt(III) complex instead of the dimeric product. The allylic radical nature and related reactivity profile of the cobalt(III)-carbene radical, including its inability to abstract hydrogen atoms from toluene solvent, were established by DFT calculations.     

Thermal behaviour of lanthanide complexes of 1,3-propanediamine- tetramethylenephosphonic acid

1,3-propanediaminotetramethylenephosphonic acid (PDTMP, H₈L) was prepared and its complexes with some lanthanide ions (La(III), Eu(III), Gd(III) and Sm(III)) were isolated. The IR spectra and thermal stabilities of PDTMP and its complexes were studied. All the complexes contain physically and coordinately bound water molecules, which are released from the solid samples below 370°C. On heating PDTMP decomposes to phosphorus oxides, while its anhydrous complexes decompose to lanthanide oxides, and cyclic and linear polyphosphates between 400 and 1000°C. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis,characterization, and antibacterial activities of some rare Earth metal complexes of pipemidic acid

Eight new solid complexes of pipemidic acid (PPA) with trichlorizated rare earth metals LaCl(3), CeCl(3), PrCl(3), NdCl(3), SmCl(3), TbCl(3), DyCl(3), and YCl(3) have been synthesized. The complexes were characterized by elemental analyses, IR, NMR, and molar conductance measurements. The general formulas of the complexes are [M(PPA)(4)]Cl(3) (M=Ce(III), Pr(III), Nd(III), Sm(III), Tb(III), Dy(III), Y(III)), and [La(PPA)(4)Cl]Cl(2). At the same time, the antibacterial activities of PPA and four of its complexes were tested. The results show that PPA and its complexes all have inhibitory action against bacteria of Escherichia coli, Bacillus subtilis, Streptococcus pneumoniae, and Pseudomonas aeruginosa but not Staphylococcus aureus. We compared their antibacterial activities and found that the antibacterial activity of [La(PPA)(4)Cl]Cl(2) against S. pneumoniae is much stronger than that of PPA and the other complexes.     

31P NMR assessment of the phosvitin-iron complex in mayonnaise

Lipid oxidation is the main reason for the limited shelf life of mayonnaise. One of the main catalysts of this process is iron, which is introduced in its ferric (Fe(III)) form via phosvitin, an egg yolk phosphoprotein rich in phosphoserines. The binding of Fe(III) to phosvitin and its ability to establish a redox couple with Fe(II) is believed to determine the oxidation rate of unsaturated lipids. In this work, a ³¹P NMR based method was developed to quantify loading of phosvitin with Fe(III) and its reductive release. Both features could be quantified in model phosvitin solutions by exploiting the paramagnetic broadening of ³¹P NMR signal of phosphoserine residues by Fe(III). This method was then successfully applied to quantify the phosvitin-Fe(III) loading in mayonnaise water phase by liquid NMR, whereas ³¹P NMR MAS could only provide a qualitative measure. The ³¹P NMR method showed a direct relation between loading of the Fe(III)-phosvitin complex and lipid oxidation.     

钇(III)离子印迹聚合物的制备及性能研究

以钇(III)离子作为模板, 以4-乙烯吡啶(4-VP)、乙酰丙酮(Hacac)和钇(III)形成的三元配合物为功能单体、乙二醇二甲基丙烯酸酯(EDMA)为交联剂, 采用本体聚合法合成了钇(III)离子配位分子印迹聚合物. 系统研究了印迹聚合物对钇(III)离子的吸附性和选择性. 结果表明, 印迹聚合物对钇(III)离子有很好的亲和性, 达到吸附平衡的时间为60 min, 最大吸附量为12.4 mg&#8226;g&#8722;1, 重复使用时性能稳定, 而且印迹聚合物对钇(III)离子具有较强的选择性识别能力.     

2,4-Dioxo-4-(4-hydroxy-6-methyl-2-pyrone-3-yl)butyric acid ethyl ester: Reagent for identifying and estimating metal ions in ring oven analysis

Ligand gave variously colored or fluorescent rings when reacted with several kinds of ions on a ring oven (Schleicher and Schuell filter paper 589²). With ions of Al(III), Be(II), Co(II), Cr(III), Cu(II), Fe(III), and Ni(II) the reactions were sensitive enough to enable application of ring colorimetry or fluorometry (excitation at 366 nm) for quantitation (detection limits, 0.1–2.0 μg of metal). A procedure for estimation of Al(III), Cr(III), and Fe(III) in mixtures was based on reaction with Ligand in combination with EDTA pretreatment, but omitting ion separation. Al(III) could be estimated reliably at its detection-limit-level, in the presence of up to 100 times as much of both Cr(III) and Fe(III).     

Determination of chromium by on-line preconcentration on a poly (hydroxamic acid) resin in flow-injection atomic absorption spectrometry

A series of poly(hydroxamic acid) resins were used for the preconcentration and determination of chromium(III). Conditions were optimized for the determination of chromium(III) and its separation from multi-component mixtures. A flow manifold was developed for the on-line preconcentration and determination of chromium(III) by atomic absorption spectrometry.     

Thermodynamic parameters and stability constants of some tervalent lanthanide complexes of 1-(3-aryl-5-hydroxy 4-isoxazolylazo) 4-sulphonic acids

The stability constants of some tervalent lanthanide chelates of 1-(3-aryl-5-hydroxy 4-isoxazolylazo) 4-sulphonic acid (PHI-4S) and its substituents have been carried out by potentiometric and spectrophotometric methods. The results indicated the formation of 1:1 and 1:2 complexes with an order: Yb(III) > Y(III) > Gd(III) > Dy(III) > Tb(III) > Sm(III) > Nd(III) > Pr(III) > La(III). The stabilities increase with a decrease in the ionic or crystal radii [except a small break at Gd(III)], indicates the absence of extensive covalent bonding due to the non-availability of 4f-orbitals for bond formation. Structure-reactivity relationships of complex formation have been discussed by Hammett’s and Irving-Rossotti theories. Thermodynamic parameters have been discussed in terms of iso-equilibrium relationship.     

Structural characterization of Am incorporated into calcite: a TRLFS and EXAFS study

Calcite homogeneously doped with Am(III) and Cm(III) was synthesized in a mixed-flow reactor. The mechanism of incorporation of these actinides (An) into calcite was investigated by time-resolved laser fluorescence spectroscopy. Two different An(III)/calcite species were found. One has been identified as ions bonded onto the calcite surface. The second An(III) species has lost its complete hydration sphere and is incorporated into the calcite bulk structure. Both Cm(III)/calcite and Am(III)/calcite complexes have been characterized by their fluorescence emission spectra and lifetimes. Structural parameters of the incorporated Am(III) species determined by EXAFS indicate a coordination number of 6.3+/-0.6 and distances of 2.40+/-0.01 A for the first AmO shell.     

Synthesis and Characterization of Samarium （Ⅲ） Containing Poly-（N-vinylacetamide） Complex

Poly (N-vinylacetamide) (PNVA) was synthesized by the free radical polymerization and its samarium (Ⅲ) binary complex was prepared and characterized by means of IR, UV-vis, X-ray photoelectron spectroscopy (XPS) and fluorescence spectra. The fluorescent intensity of samarium (Ⅲ) characteristic emission was increased significantly due to efficient energy transfer from polymeric ligand to Sm (Ⅲ) ion in the complex.     

Synthetic and structural carboxylate chemistry of neurotoxic aluminum in relevance to human diseases

The contact of Al(III) with biological components in human physiology has increased significantly over the years, due to a number of factors, prominent among which stands the rapid acidification of the environment and the concomitant introduction of that abundant metal ion in human biological fluids. As a result, pathophysiological aberrations in humans have arisen due to Al(III) (neuro)toxicity. Among the efforts targeting the elucidation of the factors responsible for Al(III) toxicity is the exploration of the requisite Al(III)-carboxylate chemistry in aqueous media, and its relevance to soluble, potentially bioavailable species capable of exerting toxic effects. A detailed synthetic, structural, and spectroscopic account of the Al(III)-carboxylate complexes, purported to exist as components in aqueous Al(III)-carboxylic acid speciation, is presented. The structures described are classified as mononuclear, dinuclear, trinuclear, tetranuclear, and polynuclear species, arising from various aqueous and non-aqueous Al(III)-carboxylate ligand reactions. Moreover, the solution chemistry and kinetic behavior of the so far reported complexes is given, with the specific aim of comparing their solid state and solution chemical and structural properties. In this sense, a comprehensive picture on the Al(III) speciation, in the presence of various physiological or biologically relevant carboxylate ligands, appears to emerge, which is expected to contribute to the understanding of Al(III) (neuro)toxicity and its consequence(s) in a multitude of human diseases. Carboxylate containing low and high molecular mass components stand prominent in their chemical preference to react with Al(III) in biological fluids. In this context, factors considered to influence the aqueous low molecular mass Al(III)-carboxylate chemistry, thus affecting the solubility and possibly the bioavailability of the resulting species, are discussed as potential research links to the ultimate manifestation of Al(III) toxicity at the cellular level.     

Luminescent sol–gel materials based on lanthanide aminopolycarboxylates (Ln = Nd, Eu, Tb, Yb)

Luminescent organic–inorganic hybrid materials containing immobilized lanthanide(III) complexes (Ln = Nd, Eu, Tb, Yb) with modified ethylenediaminetetraacetic and diethylenetriaminepentaacetic acid were synthesized by sol–gel method. Obtained hybrids exhibit 4f-luminescence in the visible (Eu(III) and Tb(III)) and IR-region (Nd(III) and Yb(III)). The influence of the hybrid matrix on the lanthanide luminescence was established and it was shown, that the location of resonance level of Eu(III) is optimal for efficient energy transfer from matrix, while in the case of Tb(III) energy transfer does not occur and Tb(III) is able to absorb energy only due to its own week f–f transitions. It was also established that the inorganic matrix leads to elimination of nonradiative energy losses and increase of 4f-luminescence lifetimes. Covalent binding of Ln(III) aminopolycarboxylates in the matrix allows to consider obtained materials as promising for creation of photo- and chemically-stable luminescent sensors.     

Structural features of green cobalt(III) hydroxide

Emission Mössbauer and X-ray absorption XANES/EXAFS spectroscopic techniques are applied to elucidate the structural features of green cobalt(III) hydroxide. A comparative analysis of structurally characterized cobalt(II) and cobalt(III) oxo-compounds shows that the parameters of the local environment of cobalt atoms in green cobalt(III) hydroxide differ substantially from those of its analogues.