Determination of Radiochemical Yield of 186Re-Labeled Complexes Using Thin-Layer Chromatography

The reaction conditions for synthesis of three rhenium complexes ¹⁸⁶Re-methylendiphosphonate (MDP), ¹⁸⁶Re-hydroxyethylidendiphosphonate (HEDP) and ¹⁸⁶Re-citrate were investigated. Radiochemical yield of complexation was determined by thin-layer chromatography and paper chromatography. The rhenium complexation with corresponding ligand was dependent on pH values of reaction mixture, concentration of the ligand studied (MDP, HEDP and sodium citrate) and concentration of the reducing agent. Stannous chloride with ascorbic acid (as antioxidant) was used for reduction of perrhenate. The labeling yield was about 90% for ¹⁸⁶Re-MDP, more than 80% for ¹⁸⁶Re-HEDP and more than 75% for ¹⁸⁶Re-citrate under optimum conditions. The possibility of application of porphyrines as organic ligands for complexation with rhenium isotopes was also examined.     

HYDROGENATION OF A DELOCALIZED DIIMINATE SIX-MEMBERED CHELATE RING IN TETRAAZAMACROCYCLIC NICKEL(II) COMPLEXES BY SODIUM BOROHYDRIDE IN WATER—EFFECT OF PROTONATION-DEPROTONATION EQUILIBRIA AND STEREOSELECIVE REDUCTION

Abstract

Charge delocalized diiminate six-membered chelate rings in the 5,7-dimethyl-1,4,8,11-tetraazacyclotetradecane-4,6-dienatonickel(II) ion(1) and the α,α′-bis(5,7-dimethyl-1,4,8, 11-tetraazacyclotetradeca-4,6-dienato-6-yl)-xylenedinicke(II) ion(2) were hydrogenated in aqueous media by sodium borohydride. In the reduction reactions, control of the pH of the reaction mixture was essential, and the pH of the solution was kept during the reaction at 3 and at 5–6 for hydrogenations of 1 and 2, respectively. The delocalized diiminate chelate ring is in protonation-deprotonation equilibrium with the β diimine form and the pK_a of the equilibrium for 2 was determined to be 9.0 for 2a (o-xylylene bridged complex), 9.3 for 2b (m-xylylene bridged complex), and 10.0 for 2c (p-xylylene bridged complex). The appropriate pH values in the hydrogenation reactions were based on the pK_a′s. X-ray structure analyses on two reduction products of 1 show that the chirality of the two asymmetric carbons in the cyclam ring is of the meso-form in the major reduction product whereas that in the minor product is of the racemic form. In the major reduction product of 2, two chiral carbons in each cyclam ring take the meso-form.     

Chromium(II) Complexes with Hydroxyethylidenediphosphonic Acid

The complex formation of chromium(II) with hydroxyethylidenediphosphonic acid (HEDP, H₅L) in an aqueous solution is studied by spectrophotometry. The pH region is determined where the HEDP complexonates of chromium(II) are stable. The effect of pH on the complexation and the composition of the coordination sphere of the complex ions is shown. The optimum conditions for the practical application of HEDP as a stabilizing ligand are chosen. The instability constants for tetra-, tri-, di-, and monoprotonated and neutral chromium(II) hydroxyethylidenediphosphonate complexes were calculated, whose pK were found to be 1.21, 2.43, 6.87, 12.60, 19.40, respectively. A new complex of chromium(II), Na₄[Cr(H₂L)₂ · 2H₂O] · 4H₂O, was isolated from a solution and characterized using elemental, IR spectroscopic, and thermographic analyses.     

Adsorption of Me-HEDP complexes onto gamma-Al2O3

This work studies the adsorption of Me-1-hydroxiethane-(1,1-diphosphonic acid) (HEDP) complex onto alumina in the pH range from 5.0 to 9.5. The extent of HEDP adsorption is not significatively affected by the presence of Me(II), while, HEDP has an interesting effect on Me(II) adsorption. At high surface covering, Cu(II) adsorption is enhanced at low pH reaching a maximum of 57% at pH nearly 6, however, at pH>6 a decrease about 20% in the amount of Cu(II) adsorbed takes place by the presence of HEDP. The model predicts a ternary surface complex (AlLCu(-)) to justify the increase of Cu(II) adsorbed at lower pH. At the lower pH and at high Zn(II) concentration the presence of equimolar concentration of HEDP also causes a discernible increase in the amount of Zn(II) adsorbed. At pH 5, the percentage of Zn(II) complexed with HEDP increased from negligible to 40% as the HEDP concentration increased. However, in this case the HEDP does not have a suppressor effect on the Zn(II) adsorption at the higher pH. Again, the presence of anionic-type complexation is here postulated to reach a good fit with the experimental results. The effect of HEDP over Zn(II) adsorption becomes less pronounced with the excess of surface sites. Cd(II)-HEDP solution complexes are weaker than those corresponding to Cu(II) and Zn(II), so competitive effects between surface and solution are much less significant in comparison to Cu(II)-HEDP and Zn(II)-HEDP alumina systems. So, the effect of HEDP on the Cd adsorption at low concentration and low pH is more stressed than in the case of Cu(II) and Zn(II). Overall, results indicate that the presence of HEDP in the aquatic systems could have a significant impact on the mobility and distribution of Cu(II), Zn(II) and Cd(II) in the environment.     

Analytical Separation of Copper(II), Cobalt(II) and Nickel(II) Using Polymer Bound Anthrantic Acid

Abstract

The preferential complexing tendency of different nietal ions towards chelating agents anchored on a polymer has been used for separation of transition metals. the anthranilic acid group was anchored on the polymeric cellulose back-bone by successive coupling with trifunctional reagent cyanuric chloride, in diozane medium, at pH 7 and 9–10, respectively. This polymer bound chelating agent was used to separate copper(II), nickel(II) and cobalt(II) in the concentration range 1.0–0.1 mmol/L. the separation of a mixture of two components was quantitative using column chromatography.     

Capillary electrophoretic and thin-layer chromatographic characterization of rhenium complexation with 1-hydroxyethylidenediphosphonic acid

1-Hydroxyethylidenediphosphonic acid (HEDP) labeled by short-lived radionuclides with the nuclear properties suitable for the therapeutical purposes (¹⁸⁶Re, ¹⁸⁸Re, ¹⁶⁶Ho) is similar to the other phosphonates widely applied in the radiopharmaceutical field for the treatment of palliative bone metastases. One of the important steps for the preparation of compounds of radiopharmaceutical interest is the quality control comprehending the radiochemical and chemical purity determination. Chromatographic methods as TLC and HPLC are mostly used for this purpose. Our experiments were focused on the application of capillary electrophoresis with UV detection to the study of rhenium complexation with HEDP. The influence of pH, concentration of the ligand and the reaction time were determined. Taking in account our previous results, the Re:SnCl₂ molar ratio 1:500 (for 0.1 mM Re) was applied to reduce perrhenate to lower oxidation states which enables the Re–HEDP complexation. Different background electrolytes were tested. The mixture of 40 mM Na₂HPO₄ with 15 mM HEDP adjusted to pH 8 was selected as the most suitable system because it enabled the separation of different forms of Re–HEDP complexes. The results obtained in this study were compared to those obtained by thin-layer chromatography with radiometric detection.     

Coupled radiotracer and voltammetric study of the adsorption of 1-hydroxy-ethane-1,1-diphosphonic acid on polycrystalline gold

Coupled application of a version of the in-situ radiotracer ‘foil’ method and voltammetry provided information on the time-, potential-, concentration- and pH-dependent adsorption of 1-hydroxy-ethane-1,1-diphosphonic acid (HEDP) on a polycrystalline gold electrode, and on the effect of Zn²⁺ ions on the adsorption phenomena. Adsorption processes on the oxide-free surface of gold were observed to be potential-dependent in the potential range 0.05–1.00 V (versus RHE), while formation and irreversible accumulation of oxidation products of HEDP could be detected at E>1.00 V. The relative adsorption strength of HEDP (its dissociation and/or oxidation products) was found to be higher on an oxide-free gold surface than on an oxide-covered one. The surface excess of HEDP increased with increasing pH. Addition of Zn²⁺ ions to the solution exerted a substantial effect on the HEDP accumulation. Namely, significant differences in the surface coverage, as well as in the kinetics and mechanism of HEDP adsorption could be detected in the potential regions below and above E=0.2 V. Reduction of Zn(II) species at E≤0.1 V is probably coupled with the induced adsorption of HEDP on an Au electrode, leading to the formation of a polymolecular HEDP–Zn surface complex layer.     

Construction of a New Perbromate-Selective Electrode. Kinetic Study of the Iron(II)- Perbromate Reaction and Microdetermination of Iron

Abstract

A perbromate- selective membrane electrode with a liquid membrane of crystal violet-perbromate dissolved in chlorobenzene is described, The liquid membrane electrode exhibits rapid and near Nernstian response to perbromate activity from 10^?5 to 10^?2 M. The response is unaffected by pH in the range 2–10, Major interferences are periodate and perchlorate. A kinetic study of the iron(II)- perbromate reaction was carried out with the perbromate electrode, A potentiometric method is described for the determination of 50–500 μg of iron (II) with relative errors and standard deviations of 1–2%.     

The effects of 1-hydroxyethane-(1,1-diphosphonic acid) on the adsorptive partitioning of metal ions onto gamma-AlOOH

1-Hydroxyethane-(1,1-diphosphonic acid) (HEDP) is extensively used in many technical applications. This work, as a first stage, examines the adsorption of aqueous HEDP, Cu(II), and Zn(II) onto boehmite (gamma-AlOOH) as single solutes. These processes can be described by the formation of inner-sphere complexes by the surface complexation model with constant capacitance. Uncomplexed HEDP is adsorbed as a mononuclear complex over the entre pH range. Four mononuclear surface complexes with different protonation levels are required to obtain a good fit of the experimental data for the pH range studied. Cu(II)- and Zn(II)-HEDP complexes at equimolar concentrations are studied at high and low surface density. The results indicate that the presence of HEDP significantly promotes metal adsorption at low pH in defects of surface sites. However, metal adsorption exhibits the same trend in the absence and presence of HEDP when the surface sites are in excess. The constant capacitance model successfully describes the experimental data through a ligand-like adsorption complex at low pH. At high pH, the model predicts separate adsorption of divalent metal and HEDP onto different surface sites as the preferred adsorption form.     

Methylation of tin(II) by methyl iodide: influences of different environmental factors on the efficiency and reaction kinetics

The methylation reaction of Sn(II) with methyl iodide (MeI) in water has been studied using sensitive GC-QSIL-FPD technology. The pH value, amount of MeI and salinity (S) are the three important factors that influence the methylation reaction in an aquatic environment. In all experiments, monomethyltin (MMT) is the only methylation product of the tin(II) reacting with MeI observed. At the 95% confidence level, the pH, MeI and S are significant for the MMT yield. The concentration of MMT in the reactor increases with increase in pH within the selected pH range of 4–9 because four different species of Sn(II)–Sn²⁺, SnOH⁺, Sn(OH)₂⁰ and Sn(OH)₃⁻–have different reaction activities with MeI. The methylation activity of Sn(II) was found to be highest at a salinity of 0.1 M at three different pH levels: 5, 7 and 9. Higher concentration of Cl⁻ (as a relatively weak nucleophilic ion) will obstruct nucleophilic attack of Sn(II) on MeI. MMT production also increases with rising volume of MeI. Moreover, first-order reaction rates have been calculated at different pH, salinity and MeI, and found to be in the range 0.0018–0.0199 h⁻¹. The reaction rate also varies largely under different reaction conditions. One probable mechanism for the methylation reaction of Sn(II) with MeI is a S_N2 nucleophilic attack on the methyl group of MeI by Sn(II), via a process of oxidative methyl-transfer. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis and Antimicrobial Evaluation of Novel N-Substituted β-Hydroxy Benzimidazole Sulfone Fluoroquinolones by Selective Oxidation Using Ticl4-H2O2

Abstract

The synthesis of N-substituted β-hydroxy benzimidazole sulfones containing 8-methoxy fluoroquinolone has been described and they were evaluated for antimicrobial activities. The compounds of N-substituted β-hydroxy benzimidazole sulfides (4a–e) and N-substituted β-hydroxy benzimidazole sulfones (5a–e) at C-7 of fluoroquinoline exhibited superior activity in vitro. 8-Methoxy fluoroquinolone carboxylic acid (1), reaction with piperizine in acetonitrile in presence of triethylamine under reflux gives 7-piperazinyl-8-methoxyfluoroquinolone (2). The latter is reacted with epichlorohydrine in presence of NaOH in acetone yielded N-substituted epoxide (3), which on treatment with 5-substituted-2-mercaptobenzimidazoles gives N-substituted β-hydroxy benzimidazole sulfides (4). Further, 4 on treatment with TiCl₄-H₂O₂ and in DCM yielded the corresponding N-substituted β-hydroxy benzimidazole sulfone (5).     

Oxidation of azo dye Orange II with hydrogen peroxide catalyzed by 5,10,15,20-tetrakis[4-(diethylmethylammonio)phenyl]porphyrinato-cobalt(II)tetraiodide in aqueous solution

The catalytic oxidation of the azo dye Orange II by hydrogen peroxide in aqueous solution has been investigated using 5,10,15,20-tetrakis-[4-(diethylmethylammonio)phenyl]porphyrinato-cobalt(II) tetra iodide 1as catalyst. The oxidation reaction was followed by recording the UV–vis spectra of the reaction mixture with time at λ_max = 485 nm. The factors that may influence the oxidation of Orange II, such as the effect of reaction temperature, concentration of catalyst, hydrogen peroxide and orange II have been studied. The results of total organic carbon analysis showed 52% of dye mineralization under mild reaction conditions. Residual organic compounds in the reaction mixture were identified by using Gas chromatography-mass spectrometry. The decolorization rate and mineralization of the dye has been found to increase with increase of catalyst concentration and reaction temperature. The rate of dye oxidation decreased with increasing the concentration of dye, H₂O₂ and at higher pH than 9. Radical scavenging measurement indicated that decolorization of Orange II by H₂O₂/cobalt (II) porphyrin complex 1 involved the formation of hydroxyl radicals as the active species.     

Chromatographic and electromigration analysis of rhenium compounds used in radiopharmacy

A large group of radiopharmaceuticals includes complex radionuclide-ligand compounds which are very sensitive to the preparation conditions, as for example pH of reaction mixture, incubation time, temperature, molar ratio of reagents, etc. It is necessary to find the optimum condition for the formation of the radionuclide-ligand complex and to select the convenient analytical methods to determine the purity of the product. The preparation of radiopharmaceuticals labeled by rhenium-186 or rhenium-188 requires the addition of a reducing agent (commonly stannous chloride) to the reaction mixture in order to reduce perrhenate to a lower oxidation state which is capable of complex formation. For rhenium concentration up to approximately 10^-5 mol/l, the molar excess of reduction agent over perrhenate is usually higher than 800 to reach the optimum yield of reduction and complexation (between 80-95%). Because of the potentially toxic effect of SnCl₂ the reduction of perrhenate by stannous chloride was studied in detail to find the way for decreasing the concentration of reducing agent in the reaction mixture without significant lowering of the yield of perrhenate reduction. The reduction of perrhenate was determined by electromigration methods, i.e., capillary electrophoresis (CZE) and isotachophoresis (ITP), and thin-layer chromatography (TLC) with radiometric detection. The highest degree of reduction of perrhenate was obtained at pH 2 at perrhenate concentration ranging from 10^-4 to 10^-3 mol/l. The stability of reduced rhenium against a pH change from 2 to 5.5 (which corresponds to the pH close to physiological values) was tested as well. The influence of the presence of ascorbic acid as an antioxidant in the reaction mixture on the stability of the preparation against the pH change was determined. The stability of reduced rhenium against dilution of rhenium in the reaction mixture to the concentration suitable for the application in radiotherapy was also found out. The data acquired by capillary electrophoresis, isotachophoresis and thin-layer chromatography are comparable. Results obtained in these experiments were applied for the study of rhenium complexes with hydroxyethylidenediphosphonic acid (HEDP).     

Crystallographic and computational study of the structure of copper(II) 2,2′-bis(2-oxidobenzylideneamino)-4,4′-dimethyl-1,1′-biphenyl

The reaction of M(OAc)₂ with 2,2′-bis(2-hydroxybenzylideneamino)-4,4′-dimethyl-1,1′-biphenyl (H₂L1) allows the synthesis of 2,2′-bis(2-oxidobenzylideneamino)-4,4′-dimethyl-1,1′-biphenyl complexes of Cu(II) (CuL1), Co(II) (CoL1) and Ni(II) (NiL1) that were characterized by elemental analysis, FTIR spectroscopy and for CuL1 also by X-ray crystallography verifying a tetradentate binding mode of L1 via an (ONNO) motif of the two phenolic oxygen atoms and two azomethine nitrogen atoms. Recrystallization from a solvent mixture of dichloromethane and methanol promotes the formation of methanol adducts. Different binding modes of the methanol–complex were investigated using density functional theory calculations and binding energies, and thermodynamic data of the interaction are reported. The results show that the favored interaction occurs when the methanol molecule acts as a Lewis acid weakly binding via an O–H···O hydrogen bridge to a phenoxide moiety leading to an elongation of the respective M–O bond.

     

Simple and Simultaneous Method for Determination of Palladium(II) and Ruthenium(III) using Second-Order-Derivative Spectrophotometry

Abstract

A simple, sensitive, and selective second-order-derivative spectrophotometric method has been developed for the simultaneous determination of palladium(II) and ruthenium(III) using 2-hydroxy-3-methoxy benzaldehyde thiosemicarbazone (HMBATSC) as a chromophoric reagent. The reagent (HMBATSC) reacts with Pd(II) and Ru(III) at pH 3.0, forming soluble yellowish green and dark brown species, respectively. Palladium and ruthenium present in the mixture were simultaneously determined without solving the simultaneous equations by measuring the second derivative amplitudes at 445 nm and 385 nm, respectively. Further, the Beer's law was obeyed in the range 0.21–12.78 µg mL^?1 and 0.25–13.42 µg mL^?1 for Pd(II) and Ru(III), respectively. A large number of foreign ions did not interfere in the present method. The proposed method was successfully applied for the determination of palladium in hydrogenation catalysts and ruthenium in water samples.     

MULTIFUNCTIONAL HYDROPHILIC POLYMERS

ABSTRACT

Different types of multifunctional hydrophilic polymers were synthesized and characterized in view of their possible biomedical application. Several poly(amide)s and poly(ester-amide)s containing oligo(oxyethylene) segments and tartaric or succinic acid residues were prepared by activated polycondensation methods. New functional derivatives of β-cyclodextrin were obtained by reaction with glycidyl ether of protected polyols. The mechanism of β-cyclodextrin polymerization with epichlorohydrine was investigated by ¹³C-NMR spectroscopy.     

Kinetic Spectrophotometric Determination of Traces of Manganese(II) by Its Catalytic Effect on Oxidation of 4‐Hydroxycoumarin with Potassium Permanganate in River Water Samples

Abstract

A new kinetic method for determination of traces of manganese(II) based on its catalytic effect on the oxidation of 4‐hydroxycoumarine with KMnO₄ at pH=1.35 and at a temperature of 25°C was proposed. The reaction was followed spectrophotometrically by measuring the decrease in the absorbance of the dye at 525 nm. The calibration graph is linear in the range 20–200 ng/cm³. The effects of certain foreign ions upon the reaction rate were determined for assessment by the selectivity of the method. The proposed method has been applied for determination of manganese(II) in river water samples with satisfactory results.     

HYDROCHLORINATION OF 2,3-ACETYLENIC ACIDS WITH THIONYL CHLORIDE IN DIMETHYLFORMAMIDE

ABSTRACT

The reaction of 2,3-acetylenic acids (1a–d) with thionyl chloride in DMF under mild conditions gave E,Z-3-chloro-2-alkenoic acids (2a–d) or esters (3a–d) depending on treating the reaction mixture with either water or alcohols.     

A Highly Sensitive Method for Determination of Copper (II) in Water Samples for Field Screening

Abstract

A new method has been developed for field screening of copper (II) in water samples, which is based on an enzyme inhibition reaction between copper (II) and nitrate reductase. The concentration of copper (II) was acquired by indirect determination the reaction product (nitrite) with a mini optical reflection sensor. Under the optimum conditions, the calibration graph was linear in the range of 5.0–50 ng mL^?1. The limit of detection was 0.5 ng mL^?1. This method has been used for the field screening of copper (II) with satisfactory results.     

Spectrophotometric Determination of Zinc in Pharmaceutical and Biological Samples with Di‐2‐pyridyl Ketone Benzoylhydrazone: a Simple,Fast, Accurate and Sensitive Method

Abstract

A simple, fast, accurate, and sensitive spectrophotometric method was developed to determine zinc(II). This method is based on the reaction of Zn(II) with di‐2‐pyridyl ketone benzoylhydrazone (DPKBH), at pH=5.5 and 50% (v/v) ethanol. Bee?s law was obeyed in the range 0.020–1.82 µg mL^?1 with a molar apsorptivity of 3.64×10⁴ L mol^?1 cm^?1, and a detection limit (3δ) of 2.29 µg L^?1. The action of some interfering ions was verified and the developed method applied to pharmaceutical and biological samples. The results were then compared with those obtained by using a flame atomic absorption technique.