Determination of Fluoride by Fluorescence Quenching

Abstract

A fluorescence quenching method for the determination of fluoride ion over the concentration range from 10^?9 to 10^?6M is presented. The fluoride ion is added to the fluorescent chelate of aluminum(III) and PAN [1- (2-pyridylazo)-2-naphthol]: the fluoride preferentially complexes the aluminum (III), displacing nonfluorescent PAN. Of the anions tested as possible interferences at equimolar levels, phosphate interferred seriously and iodide interferred somewhat.     

Spectrofluorimetric Determination of Nitrite with Pyridoxal-5-Phosphate-2-Pyridylhydrazone

Abstract

The nitrite ion oxidizes pyridoxal-5-phosphate-2-pyridyl-hydrazone in acid medium giving a fluorescent product (λ_ex 325 nm, λ_em 420 nm). This redox reaction is used to developed a spectrofluorimetric method for the determination of nitrite. The calibration graph is liner in the 0.1 ? 1.0 μg mL^?1 range. The interference levels, stoichiometry and nature of the reaction have been studied. The method is applied to determine nitrite in water and soil samples     

Synthesis,spectroscopic studies,and preliminary antibacterial assays of a palladium(II) complex with 2-mercaptothiazoline

In this article, synthesis of a palladium(II) complex with 2-mercaptothiazoline in aqueous solution is presented. Composition of the complex was defined as 1?:?2 (metal?:?ligand). Infrared and solid-state nuclear magnetic resonance indicate ligand coordination to Pd(II) through nitrogen of thiazole ring and sulfur of thiol. ESI–QTOF–mass spectrometric analysis shows primarily the dimeric form in solution. An antibiogram assay of the complex was performed by the disc diffusion method. The compound did not show antibacterial activity against the considered bacterial cells in the tested concentrations.     

Metal complexes derived from hydrazoneoxime ligands: II. Synthesis,electrospray mass spectra and magnetochemical studies of some copper(II) complexes derived from p-substituted aroylhydrazoneoximes

Mono- and binuclear copper(II) complexes derived from substituted aroylhydrazoneoximes of the general formulae [Cu(H₂LR)Cl₂]·nH₂O, [Cu(HLR)Cl], [{Cu(HLR)}₂]·2NO₃·nH₂O and [{Cu(LR)}₂]·nH₂O have been prepared and characterized, where H₂LR, HLR and LR refer, respectively, to the neutral, monoanionic and dianionic ONN tridentate aroylhydrazoneoxime ligands. Electrospray ionization (ESI) mass spectra revealed the formation of tri- and tetranuclear copper(II) complexes in dimethylformamide (DMF) or dimethysulphoxide (DMSO) solutions. The effect of substitution in the aroylhydrazone residue on the degree of deprotonation of the ligand and the energies of d–d transitions of the copper(II) complexes have been studied. Tuning of the antiferromagnetic exchange coupling by different substituents in [{Cu(HLR)}₂]·2NO₃·nH₂O and [{Cu(LR)}₂]·nH₂O complexes have been discussed.     

Synthesis and characterization of a Cu(II) complex of 2-benzylmercapto-5-methyl-1,3,4-thiadiazole (C10H10N2S2)

A Cu(II) complex of 2-benzylmercapto-5-methyl-1,3,4-thiadiazole was synthesized and characterized. The crystal structure of the copper complex and the free ligand were determined by single-crystal X-ray diffraction at room temperature: {[Cu(C₁₀H₁₀N₂S₂)₂(Cl)₂], P 1 triclinic, a = 8.1450(2) Å, b = 8.1690(2) Å, c = 10.8180(3) Å, α = 97.4040(12)°, β = 101.6270(11)°, γ = 116.1431(14)°; C₁₀H₁₀N₂S₂ ligand, Pbca orthorhombic, a = 8.7938(7) Å, b = 9.6491(7) Å, c = 25.3552(18) Å}. The metal complex framework consists of discrete units that provide crystalline stability through a network of van der Waals contacts. The Cu(II) is coordinated by two chloride ions and two 2-benzylmercapto-5-methyl-1,3,4-thiadiazole monodentate ligands showing a distorted square planar configuration. Both thiadiazole ligands coordinate through the N atom bonded to the benzylthio substituted C atom.

The FTIR spectroscopic data are consistent with this structural model. Analysis of the magnetic susceptibility from 5 K to room temperature indicates the presence of paramagnetic Cu(II), confirmed by the EPR spectrum.     

Metal derivatives of thiosemicarbazones: crystal structure of [chloro bis(triphenylphosphino) (thiophene-2-carbaldehyde thiosemicarbazone) copper(I)] complex

Reactions of copper(I) halides (X = Cl, Br, I) with thiophene-2-carbaldehyde thiosemicarbazone and triphenylphosphine in 1 : 1 : 2 molar ratio yield tetrahedral mononuclear complexes, [CuX(η¹-S-Httsc)(Ph₃P)₂] (X = Cl, 1; Br, 2; I, 3), characterized by elemental analysis, IR, NMR (¹H, ¹³C, ³¹P), and single crystal X-ray crystallography (1). The unit cell of 1 has two independent distorted tetrahedral molecules (1a and 1b) with different bond parameters. One acetonitrile is entrapped between them. Crystal data: C₈₆H₇₇Cl₂Cu₂N₇P₄S₄ 1: triclinic, P-1, a = 12.8810(9), b = 18.5049(13), c = 18.7430(13) Å, α = 63.7130(10), β = 89.0960(10), γ = 85.5010(10)°, V = 3992.4(5) ų, Z = 2, R _(int) = 0.0314. Bond parameters: 1a, Cu(1A)–Cl(1A), 2.3803(5); Cu(1A)–S(1A), 2.3822(5); Cu(1A)–P(1A), 2.2498(5) Å; P(1A)–Cu(1A)–P(2A), 124.294(19)°; 1b, Cu(1B)–Cl(1B), 2.3975(5); Cu(1B)–S(1B), 2.3756(5); Cu(1B)–P(1B), 2.2777(5) Å; P(1B)–Cu(1B)–P(2B), 127.156(19)°.     

Synthesis,spectral, thermal,and structural studies of copper(II)-squarate coordination polymer with 2-hydroxyethylpyridine, {[Cu(μ-sq)(etpy)2] · H2O} n

Polynuclear Cu(II)-squarate complex with 2-hydroxyethylpyridine, {[Cu(μ-sq)(etpy)₂] · H₂O} _n has been prepared and characterized by elemental analysis, magnetic susceptibility, thermal analysis, IR, and UV-Vis spectroscopic studies (H₂sq = squaric acid and etpy = 2-hydroxyethylpyridine). The structure of the complex was determined by single crystal X-ray diffraction. Density functional theory (DFT) and Hartree–Fock (HF) calculations were performed using the GAUSSIAN 03 program. The complex crystallizes in the monoclinic system, space group P2₁/c. The structure contains chains of squarato-O ¹,O ³-bridged polynuclear copper(II) units held together by intermolecular hydrogen bonds, weak π–π and van der Waals interactions. The distorted octahedral geometry of Cu(II) is completed by two neutral bidentate etpy ligands through the nitrogen of pyridine and hydroxyl O atom. Thermal decomposition of the complex is studied from 30 to 500°C in a static air atmosphere.     

钴(Ⅱ)与2-[2-(6-甲基苯并噻唑偶氮)]-5-二乙氨基苯甲酸体系盐酸羟胺催化吸附波的研究

Co2 +_2_[2_(6_甲基苯并噻唑偶氮 )]_5_二乙氨基苯甲酸在硼砂 -NH2OH·HCl体系中有一灵敏的极谱波 ,其峰电位Vp 为 -594mV(vs.SCE) ,钴质量浓度在0.7～1000μg/L范围内与峰电流Ip′有良好的线性关系 ,检出限为0.16μg/L。经多种电化学方法证明该波为络合催化吸附波 ,其电极过程为不可逆过程 ,电子转移数为2 ,此外还试验了多种离子对峰电流Ip′的影响。所拟方法已用于维生素B12 中钴的测定 ,结果令人满意。