Determination of lead in solution by solid phase extraction, elution, and spectrophotometric detection using 4-(2-pyridylazo)-resorcinol

Lead (+2) was selectively adsorbed on a solid phase extraction (SPE) gel (molecular recognition technology, MRT), quantitatively extracted, and spectrophotometrically determined as the Pb(II)-PAR (4-(2-pyridylazo)-resorcinol) complex. The linear range was 0.01 to 0.75 mg L^?1 and the detection limit was 6.4 µg L^?1. The MRT-SPE allows selective Pb(II) extraction from complex ion-rich matrices, which is difficult with other techniques. Interference from common matrix ions such as Fe²⁺, Ni²⁺, Cu²⁺ or Co²⁺ is minimized.      

A highly selective colorimetric sensor to Fe3+ and Co2+ in aqueous solutions

Five aromatic azo dyes with hydroxyl groups (1–5) were designed and synthesized by coupling reactions. The relationships between structures of the compounds and the spectroscopic properties were investigated. The absorption spectra of these compounds upon titration with K⁺, Ca²⁺, Al³⁺, Mg²⁺, Ni²⁺, Mn²⁺, Cd²⁺, Cr³⁺, Fe³⁺, Cu²⁺, Zn²⁺, Co²⁺, Hg²⁺, and Pb²⁺ ions in neutral aqueous solutions were reported. The results are coincident with the calculation results using the density functional theory method. The high selectivity, excellent water solubility and simple synthetic process make 1-[(2-Hydroxyl)phenylazo]-2-naphthol (5) a potential sensor for sensing Fe³⁺ and Mn²⁺ with the naked eye. 1-[(2-hydroxyl)phenylazo]-2-naphthol-6-sulfonic acid (3) shows high selectivity for the colorimetric detection of Fe³⁺ and Co²⁺ among the tested metal ions. The detection limitations of 3 for determining Co²⁺ and Fe³⁺ were calculated to be 2.8 × 10^?7 and 5.6 × 10^?7 mol/L, respectively.     

Complexation of 3-hydroxy-2,2′-iminodisuccinic acid (HIDS) with Mg2+, Ca2+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+ ions in aqueous solution

In a search for environmental-friendly metal chelating ligands for industrial applications, the protonation and complex formation equilibria of 3-hydroxy-2,2′-iminodisuccinic acid with Mg²⁺, Ca²⁺, Mn²⁺, Fe³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ ions in aqueous 0.1 mol L^?1 NaCl solution were studied at 25°C by potentiometric titration. The model for complexation and the stability constants of the different complexes were determined for each metal ion using the computer program SUPERQUAD. In all cases, complex formation was dominated by stable ML ^{n ?4} complexes.     

Kationenaustausch an komplexbildender Cellulose mit α (β)-Alanin-N,N-diessigsäure-Ankergruppen

The efficiency of a complex forming cellulose ion-exchanger with α(β)-alanin-N,N-diacetic acid anchor groups, containing still weakly acid carboxylic groups, is compared with that of a modified carboxyethylcellulose with the same type of the anchoring carboxylic functional groups and its specific behaviour in column chromatography was followed by binary mixtures of the cations CrO ₄ ^2? , Fe³⁺, Cu²⁺, Ni²⁺, Pb²⁺, Co²⁺, Cd²⁺, Mn²⁺, Ca²⁺, Mg²⁺.     

A convenient synthesis of new thiaazacrown ethers and study of their complexation reactions with some transition metal cations in binary acetonitrile–chloroform mixture using the conductometric method

Three novel thiaazacrown ethers 1, 2 and 3 were synthesized in a simple way and in high yield. The complex formation between Ag⁺, Cu²⁺, Zn²⁺, Pb²⁺, Hg²⁺ and Cd²⁺ metal cations with thiaazacrown ethers 1, 2 and 3 have been studied in acetonitrile:chloroform (1:1) binary solvent system using conductometric technique. The conductance data show that the stochiometry of the complexes with Ag⁺, Cu²⁺ and Zn²⁺ cations is 1:1 (L:M), but in the case of Pb²⁺ and Hg²⁺ cations, a 1:2 (L:M) complex is formed in solutions. The formation constants of the resulting 1:1 complexes were determined from the molar conductance-mole ratio data at 25 °C. It was found that the stability constants of 1-Ag²⁺, 2-Ag⁺ and 3-Ag⁺ complexes are higher than those of their corresponding Zn²⁺ and Cu²⁺ complexes and found to vary in order 3 > 1 > 2 for Ag⁺.     

Syntheses, spectroscopic characterization and metal ion binding properties of benzo-15-crown-5 derivatives and their sodium and nickel(II) complexes

New benzo-15-crown-5 derivatives containing nitro, amine and imine groups were prepared. Nitro compound (1) was prepared after the reaction?4′,5′-bis(bromethyl)benzo-15-crown-5 and o-nitrophenol in the presence of NaOH. After reduction process by using hydrazine hydrate and Pd/C amine compound (2) was formed. New crown ether imine compounds (3–5) were synthesized by the condensation of corresponding crown ether diamine (2) with salicylaldehyde derivatives. Sodium complexes of the crown compounds (1a–5a) form crystalline 1:1 (Na⁺: ligand) complexes with sodium perchlorate. Nickel(II) complexes (3b–5b) with 1:1 (Ni²⁺:ligand) stoichiometries were also been synthesized from the Schiff bases (3–5). The results indicated that the Schiff base ligands coordinated through the azomethine nitrogen and phenolic oxygen. The extraction ability of compounds (1, 3, 4 and 5) were also evaluated in chloroform by using several alkali and transition metal picrates such as Li⁺, Na⁺, K⁺, Cr³⁺, Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Pb²⁺.     

Synthesis and characterization of some octahedral transition metal complexes with phenyl-2-picolylketone thiosemicarbazone

Summary A series of transition metal complexes with phenyl-2-picolylketone-thiosemicarbazone, LH, of the general formula [ML₂]Cl_nmH₂O, (M=Cr³⁺, Mn²⁺, Fe²⁺, Rh³⁺, Ir³⁺ or Ru³⁺; n=0 or 1 and m=1,2 or 3) have been prepared and characterized. Magnetic and spectral (electronic and vibrational) data are commensurate with an octahedral ligand field for all complexes. The variable temperature magnetic moment shows that the iron(II) complex exists in a temperature-dependent high-spinlow-spin equilibrium. The far i.r. spectra show that the strength of the M–S bond follows the order: Mn²⁺ 2+3+3+3+3+. The various ligand field parameters, Dq, B' and are calculated.     

Determination and comparison of the stability constants of some bivalent ion complexes of 5,7-dichloro-, 5,7-dibromo-, and 5,7-dinitro-8-Hydroxyquinoline and their N-oxides

The stability constants of complexes of Mn⁺⁺, Fe⁺⁺, Co⁺⁺, Ni⁺⁺, Cu⁺⁺, Zn⁺⁺, Cd⁺⁺ and UO with 5,7-dichloro-, 5,7-dibromo- and 5,7-dinitro-8-hydroxyquinoline and their corresponding N-oxides have been determined in 75 + 25 v/v dioxan + water medium at 35°C in presence of 0.20 M sodium perchlorate by pH-titration technique as given by IRVING and Rossotti. A possible explanation for the observed orders of the stability constants of the metal complex with the different ligands, and of the complexes of a particular ligand with different metal ions is also proposed.     

A novel rhodamine-based thiacalix[4]arene fluorescent sensor for Fe3+ and Cr3+

The novel fluorescent sensor 1, which is comprised of two rhodamine B lactams as fluorophores that are 1,3-alternately linked to a thiacalix[4]arene, behaves as a highly sensitive ion-induced fluorescent sensor for Fe³⁺ and Cr³⁺. This compound was synthesized, and its recognition of metal ions was evaluated by fluorescence and absorption spectroscopy. The possible mechanism of Fe³⁺- and Cr³⁺-induced spirocycle opening of 1 leads to fluorescent and colorimetric enhancement, and these properties were investigated by spectroscopy, ¹H NMR and IR. The stoichiometric ratios and association constants of the complexes between 1 and these ions have been measured and calculated, and showed that the presence of Fe³⁺ or Cr³⁺ induced sensor 1 to form a stable 1:1 complex.     

Preparation,electrochemical behavior and variable temperature magnetic properties of transition metal complexes containing 2-phenyl-4,5-di-(2-pyridyl)imidazole

We report the synthesis of three new complexes featuring first row transition metal ions (Mn²⁺, Fe²⁺, or V³⁺) and a 2-pyridyl-substituted imidazole ligand. We investigate the electronic and magnetic properties of the complexes via electronic spectroscopy, cyclic voltammetry, superconducting quantum interference device magnetometry and density functional theory calculations. Complexes with Fe²⁺ or V³⁺ are redox active, and we observe spin crossover from the variable temperature magnetic susceptibility data for the complex with Fe²⁺. We intend to use these complexes as precursors to bimetallic mixed-valent materials.     

Hydrothermal synthesis, crystal structure of three novel complexes based on thiabendazole and 1,4-benzenedicarboxylate ligands

Three novel metal-organic complexes [Co(BDC)(TBZ)₂] (I), [Cd₂(BDC)₂(TBZ)₂(H₂O)₂] · 2(H₂O) (II), [Mn₂(BDC)(TBZ)₄(SO4)] (III) (BDC = 1,4-benzenedicarboxylate, TBZ = thiabendazole) have been prepared and characterized by IR spectrum, elemental analysis, thermogravimetric analysis, and single-crystal X-ray diffraction. X-ray structure analysis reveals that both three complexes are one-dimensional chain polymers. The 1D chain architecture of I is constructed from terephthalic acid and cobalt atoms. A simultaneous presence of chelating and monodentate coordination modes of BDC ligands is observed in complex II. In complex III, the coordinated BDC ligands adopt monodentate mode and with SO ₄ ^2? anions alternately bridge the Mn²⁺ ions into 1D chains. The 3D structures of the three complexes are stabilized by π-π stacking interactions and hydrogen-bonds.     

Spectrophotometric and voltammetric characterization of a novel selective electroactive chemosensor for Mg2+

A novel azocalix[4]arene derivative, 5,11,17,23-tetrakis[(acetophenone)azo]-25,26,27,28-tetrahydroxycalix[4]arene (APC4), containing acetophenone azo groups at the upper rim was synthesized as a chemosensor. Its binding and sensing properties with alkali and alkaline earth metal ions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺) were investigated by UV-vis spectrophotometric and voltammetric techniques. The stoichiometric ratio and the association constant were determined spectrophotometrically as 1:1 and (1.94±0.31)×10⁵ L mol^?1 for the complex between Mg²⁺ and the chemosensor, respectively. Moreover, it was shown that the interaction between Mg²⁺ and the APC4 occurred by means of the phenol groups at the lower rim by voltammetric methods. The results of spectrophotometric and voltammetric experiments showed that the chromogenic chemosensor has high selectivity towards Mg²⁺ among the other used metal ions, especially the interfering Ca²⁺ ion.      

The synthesis, structure and physical properties of lanthanide(III) complexes with nicotinic acid

This article reports the synthesis of novel, rare-earth coordination complexes with nicotinic acid. Three compounds with the general formula Ln₂[(C₅H₄NCOO)₆(H₂O)₄] (Ln = Yb, 1; Ln = Gd, 2; Ln = Nd, 3) were prepared from relatively cheap and readily available reactants. Their compositions and structure were characterized by IR spectroscopy and single-crystal X-ray diffraction. The magnetic and thermogravimetric properties were also studied. The complexes consist of centrosymetric, dimeric molecules having all six nicotinato ligands coordinated with the central atom in the bidentate mode. The coordination environment of the Ln³⁺ for all three compounds is 8. Here we describe the crystal structure of Yb and Gd complexes with nicotinic acid.      

Copper complexes formed by 3,5-bis(2,2′-bipyridin-4-ylethynyl)benzoic acid and its methyl and ethyl esters as studied by electrospray ionization mass spectrometry

Electrospray ionization mass spectrometry was used to study the complexes of ligands containing two bipyridine units, namely 3,5-bis(2,2-bipyridin-4-ylethynyl)benzoic acid (1) and its methyl and ethyl esters (2, 3), with copper cation, with CuCl₂ as a source of copper. It was found that the type of complexes formed strongly depends on CuCl₂ concentration. At lower CuCl₂ concentration, the detected complexes were rather simple and some of them were formed upon electrospray ionization conditions e.g. ions [2₂+Cu₂]²⁺ and [3₂+Cu₂]²⁺ (complexes ligand-Cu(I) of stoichiometry 2:2) which are analogical to the well known, for quaterpyridine, helical complexes. At higher CuCl₂ concentration, the detected complexes were more complicated, and most of them contained copper cations bridged by chlorides. The largest ions were [L₂+Cu₄Cl₆]²⁺. The CID MS/MS spectra of these ions allowed determination of their mass spectrometric fragmentation pathways and as a consequence their structure elucidation.      

Complexes of hydroxamic acid of carboxyethyl dextran with ions of some <Emphasis Type="Italic">d</Emphasis>-elements

Complexing capacity of carboxyethyldextranhydroxamic acid with respect to the metal cations Fe³⁺, Cu²⁺, Ni²⁺, Co²⁺, and Mn²⁺ was studied. A procedure for synthesis of the complexes being formed was suggested and the compounds obtained were analyzed by IR and electronic absorption spectroscopies.     

ADDUCTS OF THEOBROMINE WITH 3d METAL PERCHLORATES

Abstract

Adducts of theobromine (tbH) with 3d metal perchlorates (Mⁿ⁺ = Cr^3-. Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn^2- I here prepared by refluxing mixtures of the Iigand and a metal salt in ethyl acetate-triethyl orthoformate. The new complexes invariably involve 2: 1 molar ratios of tbH to metal ion and are apparently monomeric with terminal tbH ligands binding riaa ring nitrogen (N9 or Nl). The Mn²⁺, Cu²⁺ and Zn^2- complexes are distorted tetrahedral, involving tuo tbH and two unidentate perchlorato ligands in the first coordination sphere of the metal ion. The remaining metal(II) complexes (Fe, Co, Ni) were obtained as monohydrates. These compounds are pentacoordinated of the [M(tbH)₂(OClO₃)₂(OH₂)] type, containing one aqua ligand in addition to the tbH and perchlorato ligands. The Cr³⁺ and Fe³⁺ complexes are low-symmetry hexacoordinated, with two tbH ligands. two unidentate and one bidentate chelating perchlorate Iigands.     

Individual extraction constants of some divalent metal cations in the two-phase water–nitrobenzene system

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M²⁺(aq) + Sr²⁺(nb) ? M²⁺(nb) + Sr²⁺(aq) taking part in the two-phase water–nitrobenzene system (M²⁺ = Mg²⁺, Ca²⁺, Ba²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, ${\text{UO}}_{2}^{2 +} $ , Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the individual extraction constants of the M²⁺ cations in the mentioned two-phase system were calculated; they were found to increase in the following cation order: ${\text{UO}}_{2}^{2 + } $  < Zn²⁺, Ni²⁺ < Cu²⁺, Cd²⁺ < Co²⁺ < Mg²⁺ < Ca²⁺ < Mn²⁺, Fe²⁺ < Sr²⁺ < Pb²⁺ < Ba²⁺.     

Complexation in the heparin-metal ion system

The reaction of high-molecular weight heparin with Mn²⁺, Ni²⁺, Fe³⁺, and Co²⁺ in aqueous solution at 37°C with 0.154 M NaCl as the supporting electrolyte was studied by pH-metry and mathematical modeling. The formation of complex species of different compositions and stabilities was detected. The stability constants of the complexes were determined.     

Synergistic extraction of some divalent metal cations into nitrobenzene by using strontium dicarbollylcobaltate and electroneutral macrocyclic lactam receptor

From extraction experiments and $ \gamma $ -activity measurements, the exchange extraction constants corresponding to the general equilibrium M²⁺(aq) + 1·Sr²⁺(nb) $ \Leftrightarrow $ 1·M²⁺(nb) + Sr²⁺(aq) taking place in the two-phase water–nitrobenzene system (M²⁺ = Mg²⁺, Ca²⁺, Ba²⁺, Pb²⁺, Cu²⁺, Zn²⁺, Cd²⁺, $ {\hbox{UO}}_{2}^{2 + } $ , Mn²⁺, Co²⁺, Ni²⁺; 1 = macrocyclic lactam receptor–see Scheme 1; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Moreover, the stability constants of the 1·M²⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following cation order: Mg²⁺ < Co²⁺ < Cu²⁺, Mn²⁺, Ni²⁺ < Cd²⁺ < Ca²⁺ < Ba²⁺, Zn²⁺ < Pb²⁺ <  $ {\hbox{UO}}_{2}^{2 + } $ .

Photometric determination of aqueous cobalt (II), nickel (II), copper (II) and iron (III) with 1-nitroso-2-naphthol-3,6-disulfonic acid disodium salt in gelatin films

Photometric determination of aqueous Co(II), Cu(II), Ni(II) and Fe(III) was performed using indicator films prepared by immobilization of 1-nitroso-2-naphthol-3,6-disulfonic acid disodium salt (NRS) into hardened photographic film. Immobilization was based on electrostatic interaction of reagent and metal complexes with the gelatin. The isoelectric point pH of hardened gelatin (4.46±0.04) was evaluated by viscometry. Co(II), Fe(III), Ni(II) form 1:3 complexes with NRS in gelatin at pH 2 and Cu(II) forms 1:2 complexes. Their log β′ values were: Co-6.7, Fe-8.6, Cu-8.0, and Ni-6.4. The absorption maxima were: 370nm for NRS, and 430nm, 470nm, 495nm and 720nm for complexes of Co(II), Ni(II), Cu(II) and Fe(III). An algorithm for their simultaneous determination using the indicator films was developed. The detection limits were: c_lim(Co²⁺) = 0.45×10⁻⁵ M, c_lim(Fe³⁺) = 0.50×10⁻⁵ M, c_lim(Cu²⁺) = 0.67×10⁻⁵ M, c_lim(Ni²⁺) = 0.75×10⁻⁵ M,; and their sum c_lim(ΣMn⁺) = 0.82×10⁻⁵ M.