Application of HPLC to measure vanadium in environmental,biological and clinical matrices

Vanadate and vanadium compounds exist in many environmental, biological and clinical matrices, and despite the need only limited progress has been made on the analysis of vanadium compounds. The vanadium coordination chemistry of different oxidation states is known, and the result of the characterization and speciation analysis depends on the subsequent chemistry and the methods of analysis. Many studies have used a range of methods for the characterization and determination of metal ions in a variety of materials. One successful technique is high performance liquid chromatography (HPLC) that has been used mainly for measuring total vanadium level and metal speciation. Some cases have been reported where complexes of different oxidation states of vanadium have been separated by HPLC. Specifically reversed phase (RP) HPLC has frequently been used for the measurement of vanadium. Other HPLC methods such as normal phase, anion-exchange, cation-exchange, size exclusion and other RP-HPLC modes such as, ion-pair and micellar have been used to separate selected vanadium compounds. We will present a review that summarizes and critically analyzes the reported methods for analysis of vanadium salts and vanadium compounds in different sample matrices. We will compare various HPLC methods and modes including sample preparation, chelating reagents, mobile phase and detection methods. The comparison will allow us to identify the best analytical HPLC method and mode for measuring vanadium levels and what information such methods provide with regard to speciation and quantitation of the vanadium compounds.     

From Weakly Coordinating to Non‐Coordinating Anions? A Simple Preparation of the Silver Salt of the Least Coordinating Anion and Its Application To Determine the Ground State Structure of the Ag(η2‐P4)2+ Cation

The unexpected but facile preparation of the silver salt of the least coordinating [(RO)₃Al‐F‐Al(OR)₃]^? anion (R=C(CF₃)₃) by reaction of Ag[Al(OR)₄] with one equivalent of PCl₃ is described. The mechanism of the formation of Ag[(RO)₃Al‐F‐Al(OR)₃] is explained based on the available experimental data as well as on quantum chemical calculations with the inclusion of entropy and COSMO solvation enthalpies. The crystal structures of (RO)₃Al←OC₄H₈, Cs⁺[(RO)₂(Me)Al‐F‐Al(Me)(OR)₂]^?, Ag(CH₂Cl₂)₃⁺[(RO)₃Al‐F‐Al(OR)₃]^? and Ag(η²‐P₄)₂⁺[(RO)₃Al‐F‐Al(OR)₃]^? are described. From the collected data it will be shown that the [(RO)₃Al‐F‐Al(OR)₃]^? anion is the least coordinating anion currently known. With respect to the fluoride ion affinity of two parent Lewis acids Al(OR)₃ of 685 kJ mol^?1, the ligand affinity (441 kJ mol^?1), the proton and copper decomposition reactions (?983 and ?297 kJ mol^?1) as well as HOMO level and HOMO–LUMO gap and in comparison with [Sb₄F₂₁]^?, [Sb(OTeF₅)₆]^?, [Al(OR)₄]^? as well as [B(R^F)₄]^? (R^F=CF₃ or C₆F₅) the [(RO)₃Al‐F‐Al(OR)₃]^? anion is among the best weakly coordinating anions (WCAs) according to each value. In contrast to most of the other cited anions, the [(RO)₃Al‐F‐Al(OR)₃] anion is available by a simple preparation in conventional inorganic laboratories. The least coordinating character of this anion was employed to clarify the question of the ground state geometry of the Ag(η²‐P₄)₂⁺ cation (D_2h, D₂ or D_2d?). In agreement with computational data and NMR spectra it could be shown that the rotation along the Ag‐(P‐P‐centroid) vector has no barrier and that the structure adopted in the solid state depends on packing effects which lead to an almost D_2h symmetric Ag(η²‐P₄)₂⁺ cation (0 to 10.6° torsion) for the more symmetrical [Al(OR)₄]^? anion, but to a D₂ symmetric Ag(η²‐P₄)₂⁺ cation with a 44° twist angle of the two AgP₂ planes for the less symmetrical [(RO)₃Al‐F‐Al(OR)₃]^? anion. This implies that silver back bonding, suggested by quantum chemical population analyses to be of importance, is only weak.     

ESR study of free radicals formed upon UV irradiation of nitropentafluoroacetone in various solvents

The formation of CF₃C(O)CF₂N(O^.)O₂CF₂C(O)CF₃ free radicals upon the UV irradiation of nitropentafluoroacetone (1) in toluene and mesitylene is established by ESR. The most likely cause of their formation is the one-electron oxidation of the solvents by photoexcited1 followed by decay of the radical anion formed from1 with the expulsion of an NO₂ anion and attachment of the radical to a molecule of original1. The irradiation of 1 in triethylsilane results in the elimination of a fluoride ion and fixation of a CF₃COCFN(O^–)O' radical. UV irradiation of ketone1 in pentane results in the abstraction of a hydrogen atom from the solvent and the formation of a CF₃COCF₂N(OH)O ' radical.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 512–514, March, 1993.     

Bis(cyclopentadienyl)methan-verbrückte Zweikernkomplexe,V. Heteronukleare Co/Rh-, Co/Ir-, Rh/Ir- und Ti/Ir-Komplexe mit dem Bis(cyclopentadienyl)methan-Dianion als Brückenliganden

Bis(cyclopentadienyl)methane-bridged Dinuclear Complexes, V^[1]. – Heteronuclear Co/Rh-, Co/Ir-, Rh/Ir-, and Ti/Ir Complexes with the Bis(cyclopentadienyl)methane Dianion as Bridging Ligand^* The lithium and sodium salts of the [C₅H₅CH₂C₅H₄]^- anion, 1 and 2 , react with [Co(CO)₄I], [Rh(CO)₂Cl]₂, and [Ir(CO)₃Cl]n to give predominantly the mononuclear complexes [(C₅H₅-CH₂C₅H₄)M(CO)₂] ( 3, 5, 7 ) together with small amounts of the dinuclear compounds [CH₂(C₅H₄)₂][M(CO)₂]₂ ( 4, 6, 8 ). The ¹H- and ¹³C-NMR spectra of 3, 5 , and 7 prove that the CH₂C₅H₅ substituent is linked to the π-bonded ring in two isomeric forms. Metalation of 5 and 7 with nBuLi affords the lithiated derivatives 9 and 10 from which on reaction with [Co(CO)₄I], [Rh(CO)₂Cl]₂, and [C₅H₅TiCl₃] the heteronuclear complexes [CH₂(C₅H₄)₂][M(CO)₂][M′(CO)₂] ( 11–13 ) and [CH₂(C₅H₄)₂]-[Ir(CO)₂][C₅H₅TiCl₂] ( 17 ) are obtained. Photolysis of 11 and 12 leads almost quantitatively to the formation of the CO-bridged compounds [CH₂(C₅H₄)₂][M(CO)(μ-CO)M′(CO)] ( 14, 15 ). According to an X-ray crystal structure analysis the Co/Rh complex 14 is isostructural to [CH₂(C₅H₄)₂][Rh₂(CO)₂(μ-CO)] ( 16 ).     

SYNTHESIS AND CHARACTERIZATIONS OF NEAR INFRARED ABSORBING POLYMERS

A series of near infrared (NIR) absorbing dinuclear ruthenium dicarbonylhydrazine complexes (DCH-Ru),[{Ru(bpy)_2)_2μ-DCH]~(n ) (where bpy = 2,2'-bipyridinc and n = 2, 3 or 4), were prepared. The DCH-Ru complexes areelectrochromic in the NIR region with a high absorption coefficient at 1550-1600 nm typically over 10000 M~(-1)cm~(-1). DCH-Ru complex polymers with good NIR electrochromic properties were also obtained and processed to make a device foroptical attenuation at a wavelength of 1550 nm. The potential of these DCH-Ru polymers for use in a variable opticalattenuator has been demonstrated with an attenuating power at the 1550-nm telecommunication wavelength over 7.0 dB permicron of polymer film thickness. Other classes of NIR active materials are the pentacenediquinones and the correspondingpoly(ether pentacenediquinone)s. These polymers can be electrochemically reduced to the corresponding semiquinone(radical anion) having NIR absorption within a telecom window (e. g., 1310 nm).     

Study of the Properties of Electrodeposited Polypyrrole Films

Experimental and theoretical methods have been used for characterization of the properties of polypyrrole films. The AFM studies show that the morphology of polypyrrole (PPy) films on polycrystalline gold electrodes at the first stages of synthesis depends on the structure of the metal surface. It was established that mobility of anions depends remarkably on the rate of electrodeposition of the polymer film. If PPy film was deposited at relatively low current density, mobility of ClO^- ₄ anion was not high enough to guarantee electroneutrality during redox cycling and cations take part in this process especially when Li⁺ cations were replaced by more mobile ⁺ cations. Semiempirical (AM1 and PM3) quantum-chemical methods were used for theoretical studies. It was established that different size and charge of the anions together with the variation in doping levels give rise to a different optimal conformation of oligopyrrole cations which, in turn, define the resulting polymer to be either all-anti (common linear chains) or all-syn (formation of helical structures) or a combination of the two.     

Reversible anion exchanges between the layered organic-inorganic hybridized architectures: syntheses and structures of manganese(II) and copper(II) complexes containing novel tripodal ligands

Six noninterpenetrating organic-inorganic hybridized coordination complexes, [Mn(3)(2)(H(2)O)(2)](ClO(4))(2).2 H(2)O (5), [Mn(3)(2)(H(2)O)(2)](NO(3))(2) (6), [Mn(3)(2)(N(3))(2)].2 H(2)O (7), [Cu(3)(2)(H(2)O)(2)](ClO(4))(2) (8), [Mn(4)(2)(H(2)O)(SO(4))].CH(3)OH.5 H(2)O (9) and [Mn(4)(2)](ClO(4))(2) (10) were obtained through self-assembly of novel tripodal ligands, 1,3,5-tris(1-imidazolyl)benzene (3) and 1,3-bis(1-imidazolyl)-5-(imidazol-1-ylmethyl)benzene (4) with the corresponding metal salts, respectively. Their structures were determined by X-ray crystallography. The results of structural analysis of complexes 5, 6, 7, and 8 with rigid ligand 3 indicate that their structures are mainly dependant on the nature of the organic ligand and geometric need of the metal ions, but not influenced greatly by the anions and metal ions. While in complexes 9 and 10, which contain the flexible ligand 4, the counteranion plays an important role in the formation of the frameworks. Entirely different structures of complexes 5 and 10 indicate that the organic ligands greatly affect the structures of assemblies. Furthermore, in complexes 5 and 6, the counteranions located between the cationic layers can be exchanged by other anions. Reversible anion exchanges between complexes 5 and 6 without destruction of the frameworks demonstrate that 5 and 6 can act as cationic layered materials for anion exchange, as determined by IR spectroscopy, elemental analyses, and X-ray powder diffraction.     

含2,6-二甲酰胺基吡啶单元的大环合成、结构及其对四面体构型阴离子的络合性质

采用前体二胺N,N′-(3-氨基苯基)-2,6-二甲酰亚胺吡啶(1)和5,5′-亚甲基双水杨醛(2)进行缩合反应得到含酚羟基的[1+1]席夫碱大环L¹,将其中席夫碱C=N双键还原得到环状骨架更具柔性的饱和大环L²。通过¹H NMR、FABMS和元素分析等对大环组成进行了表征,并通过X射线单晶衍射解析了两个大环分子的晶体结构。采用UV-Vis光谱滴定技术对大环与系列阴离子的络合作用进行了考察,结果表明,席夫碱大环L¹对四面体构型的阴离子H₂PO^-₄、HP₂O₇^3-和H₂P₂O₇^2-有明显的选择性识别作用,进一步通过UV-Vis光谱、核磁滴定等技术获得了识别反应的配位比及平衡常数(K),L¹对3个磷酸阴离子的络合能力依H₂PO^-     

铜催化的α-氨基丙二腈的脱氰氧代反应：一种合成叔酰胺的新方法

新反应、新试剂的发展是有机合成化学的重要研究内容,基于前期在α-氨基丙二腈合成方法学方面的工作基础,我们发展了一例铜催化的α-氨基丙二腈的脱氰氧代反应.通过将甲酰胺转化为α-氨基丙二腈后,借助其亲核属性来合成α-氨基丙二腈底物,而后将底物重新转化为酰胺,从而实现形式上的氨基甲酰负离子的亲核加成(取代)反应.该工作首次完成了形式上的甲酰胺碳原子的极性反转,实现了将α-氨基丙二腈作为氨基甲酰负离子替代物的反应新模式,为叔酰胺化合物的合成提供了新的思路和方法,且具有反应条件简单,底物适用性广及适合克级规模制备等特点.     

Coordination Sites for Sodium and Potassium Ions in Nucleophilic Adeninate Contact ion-Pairs: A Molecular-Wide and Electron Density-Based (MOWED) Perspective

The adeninate anion (Ade⁻) is a useful nucleophile used in the synthesis of many prodrugs (including those for HIV AIDS treatment). It exists as a contact ion-pair (CIP) with Na⁺ and K⁺ (M⁺) but the site of coordination is not obvious from spectroscopic data. Herein, a molecular-wide and electron density-based (MOWED) computational approach implemented in the implicit solvation model showed a strong preference for bidentate ion coordination at the N3 and N9 atoms. The N3N9-CIP has (i) the strongest inter-ionic interaction, by −30 kcal mol⁻¹, with a significant (10–15%) covalent contribution, (ii) the most stabilized bonding framework for Ade⁻, and (iii) displays the largest ion-induced polarization of Ade⁻, rendering the N3 and N9 the most negative and, hence, most nucleophilic atoms. Alkylation of the adeninate anion at these two positions can therefore be readily explained when the metal coordinated complex is considered as the nucleophile. The addition of explicit DMSO solvent molecules did not change the trend in most nucleophilic N-atoms of Ade⁻ for the in-plane M-Ade complexes in M-Ade-(DMSO)₄ molecular systems. MOWED-based studies of the strength and nature of interactions between DMSO solvent molecules and counter ions and Ade⁻ revealed an interesting and unexpected chemistry of intermolecular chemical bonding.