2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol as a reagent for the spectrophotometric determination of La(III), Y(III), and Ce(III)

The complexes of the reagent 5-Br-PADAP with the metal ions La(III), Ce(III), and Y(III) have been studied.The composition and stability of these complexes have been determined. A sensitive spectrophotometric procedure for the determination of the metal ions La(III), Ce(III), and Y(III) has been proposed. The limitations of this procedure and the effect of other ions have been studied.     

Chemistry of substituted sulphuric acids—XVII. Complexes of V(III), Cr(III), Mn(II) and Fe(II) methylsulphates

V(III), Cr(III), Mn(II) and Fe(II) methylsulphates form stable donor-acceptor complexes with nitrogen donors. 1:1 and 1:2 complexes with bipyridyl have been prepared in respect of trivalent salts and 1:2 and 1:4 metal:base complexes have been obtained in respect of divalent metal salts with bipyridyl and pyridine respectively. Electronic spectra suggest an octahedral geometry around metal ions. IR spectra of the anhydrous metal methylsulphates have been studied and assigned. The changes in the IR spectra of the methylsulphate group in different stereochemical situations have been observed.     

Complete assignments of NMR data of salens and their cobalt (III) complexes

Salens, derived from 1,2‐ethylenediamine and salicylaldehydes, have been widely used as ligands for metal complexes which have been showing enormous potential in chemical properties of asymmetric catalysts as well as biological properties such as anticancer agents. Almost all of the salen–metal complexes with their corresponding metal (II)‐complexes show the evidences of chelation of two oxygens in salens. However, several metal (II) complexes, especially cobalt (II) complexes, could not show NMR spectra due to their paramagnetism. Recently, it has been reported that one of the cobalt (III) complexes was used for NMR spectroscopy to evaluate its stereoselectivity as a catalyst. Even though many salen ligands are known, their NMR data are not assigned completely. It was possible that modification in northern part of salen with 2‐hydroxyphenyl group afforded another oxygen chelation site in salen ligand. Here we report that synthesis and full NMR assignment of new salen ligands, which form meso 1,2‐bis(2‐hydroxyphenyl)ethylenediamine) and their cobalt (III) complexes. The assignments of ¹H and ¹³C NMR data obtained in this experiment can help us to predict the NMR data of other salen ligands. Copyright © 2008 John Wiley & Sons, Ltd.     

The solvent extraction of iron from steel solutions with 2-hexylpyridine prior to the determination of trace elements

The distribution of iron(III) between aqueous hydrochloric acid and 0.1M 2-hexylpyridine in benzene was examined as a function of acid concentration in the aqueous solution, the metal concentration being kept constant, and as a function of increasing ferric chloride concentration at a constant acidity of hydrochloric acid. The distribution coefficient of Fe(III) (tracer) is dependent on the square of the 2-hexylpyridine concentration in the benzene phase. Negatively charged complexes of the type FeCl(2-)(5) may be the species extracted. The formation of a mixture of 1:1 and 1:2 complexes with 2-hexylpyridine is indicated. Salting-out effects of a number of salts have been investigated. Separation factors of several metal ions relative to iron(III) in 7M hydrochloric acid are also reported. The results indicate that iron(III) can be selectively separated from a large number of elements, and the method has been utilized for the preconcentration of non-ferrous metal ions in mild steels by selective separation of iron, before their subsequent determination by emission spectrometry.     

Spectrophotometric determination of cobalt, nickel, palladium, copper, ruthenium and molybdenum after extraction of their isoamyl xanthate complexes into molten naphthalene

A method has been developed for the spectrophotometric determination of microamounts of Co(II), Ni(II), Cu(II), Pd(II), Ru(III) and Mo(VI) after extraction of their isoamyl xanthate complexes into molten naphthalene. The method has been applied to the determination of these metal ions in various alloys and in environmental samples (fly ash).     

Liquid-liquid extraction of iron(III) and gallium(III) with macrocyclic Schiff bases containing bisphenol A subunits

The quantitative extraction of iron(III) and gallium(III) was investigated with the recently synthesized macrocyclic Schiff base containing bisphenol A subunits. The phenol groups in the Schiff base moiety led to a large increase in the percent extraction of trivalent metal ions. The substitution of methoxy groups for phenolic OH ligands resulted in a marked decrease in the extractability of metal ions, and no iron(III) was extracted. The corresponding acyclic Schiff base was found to have a reasonable reactivity toward metal ions and a better solubility in organic solvents. The iron(III) and gallium(III) complexes with macrocyclic and acyclic Schiff bases were quantitatively extracted into nitrobenzene without the presence of bulky counter anions. A single extraction gave a good separation of iron(III) from iron(II) in the mole ratios 4:1 to 1:3. The red iron(III) complexes can be used for the extraction-spectrophotometric determination of iron(III). The apparent molar absorptivity at 518 nm is 5.43 × 10³lmol⁻¹ cm⁻¹.     

Synthesis and characterization of Rhodium(III) dichloro complexes with unsymmetrically bound salen-type ligands

We have synthesized a series of novel octahedral Rh(III) salen-type complexes where the salen ligand is unsymmetrically bound to the Rh(III) dichloride center. This mode of bonding left one intact phenol group coordinating to the rhodium center and has never before been observed in salen-metal chemistry. These remarkably stable complexes possess unique coordination geometry and represent the first time that Rh(III) salen complexes have been successfully isolated from the direct combination of RhCl(3).3H2O and the salen ligand in the absence of a nucleophilic base. The (salen)Rh(III) dichloride complex can be converted to the analogous monochloride complex by reaction with metal carbonate salts.     

Structures and luminescent properties of two heterotrimetallic Ln(III)–Sr(II)–K(I) complexes

Eu(III)–Sr(II)–K(I) and Tb(III)–Sr(II)–K(I) heterotrimetallic metal-organic frameworks with 2,4,6-pyridinetricarboxylic acid have been synthesized under hydrothermal conditions. The complexes are isomorphic and both in triclinic space group P-1. The ligands bond with three metal ions with two coordination modes. One connects seven metal ions and the other connects eight metal ions. IR spectra, thermal analysis, and photoluminescent properties have been studied. The results display strong characteristic emissions of Eu(III) or Tb(III) ions with excitation of ultraviolet radiation.     

Separation and determination of aluminium by single-column ion-chromatography

A quick, reliable method for the determination of Al(III) in the presence of other metal ions is presented. A Chromatographic system consisting of a low-capacity cation-exchange column, an eluent of diprotonated p-phenylenediamine, and a conductivity detector was used to measure the retention times for various cations. During the course of this work, it was found that Al(III) was eluted later than most bivalent metal ions but earlier than other tervalent metal ions. Therefore the concentration of eluent was adjusted so that an early sharp peak was obtained for Al(III) and the bivalent metal ions were eluted as a group. Through analysis of an NBS standard, as well as of solutions containing Al(III) and other metal ions, the method was shown to be precise, accurate and rapid for determination of Al(III) without interference from common bivalent metal ions.     

Chelometric Titration of Trace Amounts of Metal Ions Employing Instrumentally Measured Fluorometric Endpoints

Abstract

Trace amounts of metal ions which form stable complexes with EDTA at pH 4.0 have been titrated using morin as a fluorometric indicator. Back ticration of excess EDTA with Ga(III) and instrumental endpoint detection were employed for the determination of ions which are not normally determined by fluorometric methods. The continuous monitoring of the change in the fluorescence intensity throughout a deration also allowed mixtures of Ga(III) and In(III) to be determined when TTHA and EDTA were employed as double titrants.     

Use of ion exchange for the determination of stability constants of metal-humic substance complexes

Humic substances (HSs) occur throughout the ecosphere in soils, waters and underground systems. The strong complexation of HSs is of importance in the migration of radionuclies in geological media. Renewed interest in stability constants of complexes of radioelements and radionuclides with humic and fulvic acids has been generated by problems associated with the nuclide migration in the environment. Use of the ion exchange method for the determination of conditional stability constants of metal-HS complexes was examined and reviewed. The complexation of HS to metal ions cannot be described in rigorous mathematical terms because of the ill-defined nature of HSs in contrast with the complexation of single ligands. Furthermore, the advantages and disadvantages of Schubert's and, Ardakani-Stevenson's, curve fitting methods were discussed. The great stabilities of HS complexes to rare earths (Yb(III), Tb(III), Eu(III), Gd(III)), americium(III), cobalt(II), uranyl(VI) and thorium(IV) were revealed.     

Complexation and Thermal Studies of Uric Acid with Some Divalent and Trivalent Metal Ions of Biological Interest in the Solid State

Nine new [metal uric acid] complexes [M(Ua) n ]°·XH 2 O have been synthesized. These complexes have been characterized by elemental analysis, X-ray diffraction (XRD), magnetic susceptibility ( w eff. ), FTIR spectra, thermal analysis (TG & DTA), and electronic spectra (UV/visible). Uric acid (HUa) coordinates as a bidentate ligand to Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Al(III), Cr(III) and Fe(III) through the protonated N-7 within the imidazole ring and O-6 within the pyrimidine ring. Uric acid forms neutral metal urate complexes with all the above metal ions. The quantitative compositions were determined as [M(Ua) 2 ·(H 2 O) 2 ]°·XH 2 O where M(II)=Mn, Fe, Co, Ni, Cu, Zn and X=2, 4, 2, 4, 2, 2, respectively. The M(II) complexes exhibit an isostructural octahedral coordination with N-7, O-6 of two uric acid ligand molecules, and O of two water molecules. Compositions were also determined as [M(Ua) 3 ]°·YH 2 O where M(III)=Al, Cr, Fe and Y=6, 3, 3 respectively. All the M(III) complexes form an isostructural octahedral coordination with N-7 and O-6 of three uric acid ligand molecules. Iron(III) complexes prepared with N 1 , N 3 and N 9 -methyl uric acid yielded brown complexes with a metal ligand ratio of 1 3, while N 7 -methyl uric acid did not yield a complex due to blockage of N-7 with a methyl group.     

Synthesis, characterization, and fluorescence behavior of four novel macrocyclic emissive ligands containing a flexible 8-hydroxyquinoline unit

Four emissive macrocyclic ligands mono-substituted with an 8-hydroxyquinoline pendant arm are presented. The new compounds have been used for metal-ion detection, which results from the competition between PET (photo-induced electron transfer) and PPT (photo-induced proton transfer) mechanisms. Solid metal complexes with divalent Cu(II), Zn(II), and Cd(II), and trivalent metal ions Al(III) and Cr(III) have been also synthesized and characterized. The compounds have been isolated as mononuclear or dinuclear (Cu(II)) complexes, confirming the stoichiometry observed in solution.     

Synthesis and characterization of cerium and yttrium alkoxide complexes supported by ferrocene-based chelating ligands

Two series of Schiff base metal complexes were investigated, where each series was supported by an ancillary ligand incorporating a ferrocene backbone and different N=X functionalities. One ligand is based on an imine, while the other is based on an iminophosphorane group. Cerium(IV), cerium(III), and yttrium(III) alkoxide complexes supported by the two ligands were synthesized. All metal complexes were characterized by cyclic voltammetry. Additionally, NMR, Mo?ssbauer, X-ray absorption near-edge structure (XANES), and absorption spectroscopies were used. The experimental data indicate that iron remains in the +2 oxidation state and that cerium(IV) does not engage in a redox behavior with the ancillary ligand.     

Speciation studies by capillary electrophoresis- Simultaneous determination of chromium(III) and chromium(VI)

A method for the simultaneous determination of chromium(III) and chromium(VI) by capillary electrophoresis (CE) has been developed. The chromium(III) has been chelated with 1,2-cyclohexanediaminetetraacetic acid (CDTA) in order to impart a negative charge and similar mobility to both the chromium(III) and the chromium(VI) species. The effects of the amount of the reagent, pH and heating time required to complete the complexation have been studied. Factors affecting the CE behaviour such as the polarity of electrodes and the pH of electrophoretic buffer have been investigated. The separated species have been monitored by direct UV measurements at 214 nm. The detection limits achieved are 10 microg/l for Cr(VI) and 5 microg/l for Cr(III) and linear detector response is observed up to 100 mg/l. The procedure has been applied to the determination of both chromium species in industrial electroplating samples and its accuracy was checked by comparing the results (as total chromium) with those of atomic absorption spectrometry. No interference occurred from transition metal impurities under optimized separation conditions. The method is also shown to be feasible for determining Cr(III) as well as other metal ions capable to form complexes with CDTA (like iron(III), copper(II), zinc(II) and manganese(II)) in pharmaceutical preparations of essential trace elements.     

Determination of metals at trace levels via pre-column derivatization and nonpolar stationary-phase high-performance liquid chromatography with n-butyl-2-naphthylmethyldithiocarbamate complexes

A new, very stable dithiocarbamate, bis(n-butyl-2-naphthylmethyldithiocarbamate) zinc(II), has been synthesized and its use in trace metal determination by high-performance liquid chromatography (h.p.l.c.) has been investigated. Metal complexes of this ligand are thermodynamically stable and kinetically inert at the 1 × 10^-8 M level. Various metal complexes including nickel(II), iron(III), copper(II), mercury(II), and cobalt(II) have been “baseline” separated by nonpolar stationary-phase h.p.l.c. The detection limits are about 1–2 ng with a variable-wavelength absorbance detector.     

Simultaneous determination of iron(III) and vanadium(V) with N-phenylcinnamohydroxamic acid and thiocyanate by extraction-spectrophotometry

N-Phenylcinnarnohydroxamic acid (PCHA) reacts with iron(III) and vanadium(V) in the presence of thiocyanate to form water-insoluble orange and green complexes, respectively. The iron(III)-PCHA and vanadium(V)-PCHA-thiocyanate complexes can be quantitatively extracted into toluene and other common organic solvents at pH 1.5–2.0. The absorption spectra and composition of both complexes are described. The effects of foreign ions and of experimental variables on the extraction and determination of the two metal ions are studied. A simple, selective method is described for the simultaneous determination of iron(III) and vanadium(V) by extraction-spectrophotometry; absorbances are measured at 440 and 580 nm. Mixtures can be determined over the range 10^?4–10^?5 M in each metal. The method was applied successfully to the analysis of standard steels for iron and vanadium.     

Promising anticancer mono- and dinuclear ruthenium(III) dithiocarbamato complexes: systematic solution studies

During the last decade, our research group has prepared a number of metal dithiocarbamato derivatives of Pt, Pd and Au that were expected to resemble the main features of cisplatin together with higher activity, improved selectivity and bioavailability, and lower side-effects. Furthermore, we have already published the synthesis, characterization and in vitro cytotoxicity studies of novel ruthenium(III) dithiocarbamato complexes such as [RuL(3)] monomers (11) and α-[Ru(2)L(5)]Cl dimers (12) with five different dithiocarbamate ligands. As both the monomer and the dinuclear complexes have shown significant antitumor activity in different human tumor cell lines, we decided to widen the characterization studies and to analyse thoroughly their behavior in physiological-like medium by UV-visible and CD spectroscopy. In the present paper we report on the crystal structure of [Ru(DMDT)(3)], [Ru(PDT)(3)] and [Ru(ESDT)(3)] complexes and we determine the spin state of the paramagnetic Ru(III) by means of Evans' method. Then, we discuss in detail the UV-visible spectral data of the complexes in different medium. All the studied complexes are stable in dimethyl sulfoxide, and show low solubility in phosphate buffered saline solution, particularly the monomer species, even at low concentration, while increased solubility for both types of complexes have been found in the presence of bovine serum albumin (BSA). Moreover, no changes on the coordination sphere of the metal, as well as no direct interaction between the BSA protein and the complex have been identified by UV-visible spectroscopy. However, some conformational changes on the BSA structure, induced by the ruthenium(III) complexes have been confirmed by CD spectroscopy, indicating a probable secondary electrostatic interaction between the metal complex and the peptide. In addition, no significant interaction has been demonstrated with the components of Dulbecco's Modified Eagle's Medium, used for the in vitro assays.     

Simultaneous Spectrophotometric Determination of Aluminum and Iron in Micellar Media by Using the H‐Point Standard Addition Method

A very simple spectrophotometric method for simultaneous determination of aluminum(III) and iron(III) based on formation of their complexes with pyrocatechol violet (PCV) in micellar media, using the H‐point standard addition method (HPSAM), is described. In micellar media, the metal complexes of Al‐PCV and Fe‐PCV are formed very fast. Formation of both of the complexes was complete within 5 min at pH 8.5. The linear ranges for aluminum and iron were 0.05‐2.50 and 0.10‐4.00 μg mL^?1, respectively. The relative standard deviation (R.S.D.) for the simultaneous determination 0.40 μg mL^?1 of Al(III) and 0.20 μg mL^?1 of Fe(III) were 3.24% and 4.22%, respectively. Interference effects of common anions and cations were studied. The method was applied to simultaneous determination of Al(III) and Fe(III) in standard reference material and alloy samples.