Kinetic fluorimetric determination of nanogram amounts of manganese, based on its catalysis of the oxidation of 2-hydroxybenzaldehyde thiosemicarbazone with hydrogen peroxide

A kinetic method is described for the determination of trace amounts of manganese(II), based on its catalytic effect on the oxidation of 2-hydroxybenzaldehyde thiosemicarbazone by hydrogen peroxide. The reaction is followed by measuring the rate of change of fluorescence (lambda(ex) 365 and lambda(em) 440 nm). The calibration is linear over the manganese range 2-9 ng ml with a precision of +/-1%. The proposed method suffers from few interferences.     

Simultaneous kinetic determination of copper, cobalt and nickel by means of -group interchange reactions

The kinetic determination of copper, cobalt and nickel in binary and ternary mixtures without prior separation is described. The methods are based on the difference in the reaction rate of interchange of - groups between thiosemicarbazide and 6-methylpicolinaldehyde azine in the presence of these ions at pH 4.5. Through these reactions the corresponding metal thiosemicarbazone complexes are formed. Various ratios of these ions at the 10(-5)M level can be determined photometrically by either the logarithmic extrapolation method or a combined initial-rate and fixed-time method proposed here for the first time.     

Azomethine derivatives of aluminium containing AlOSiMe3 groups

The synthesis of azomethine derivatives of aluminium containing AlOSiMe₃ groups and resistant to hydrolysis is described. These have been prepared either by the equimolar reactions of bibasic tridentate or bibasic tetradentate azomethines, viz. N-(2- mercaptoethyl) salicylaldimine, N-(2-mercaptophenyl) salicylaldimine, salicylaldehyde sulphisoxazole, salicylaldehyde azine, salicylaldehyde semicarbazone, salicylaldehyde thiosemicarbazone, o-hydroxyacetophenone azine N,N' 1,3-propylene-bis(salicylaldimine) and diacetyl bis(2-mercaptoanil), or of 1 : 2 molar reactions of monobasic bidentate imines viz. N-(2-mercaptophenyl) benzaldimine, benzaldehyde semicarbazone and benzaldehyde thiosemicarbazone with Me₃SiOAl(OPrⁱ)₂ in the medium of dry benzene. The resulting derivatives are coloured solids with sharp m.ps, non-volatile, non-electrolytes, soluble in chloroform, dimethylformamide and dimethylsulphoxide, and monomeric in nature. Their IR,¹H NMR and electronic spectral data have been presented in support of the proposed structures.     

Fused Nitrogen-Containing Heterocycles: IV. 3-Benzoyl-2-oxo-1,2-dihydroquinoxaline Hydrazones and Flavazoles Derived Therefrom

3-Benzoyl-1,2-dihydroquinoxalin-2-one reacts with hydrazine and thiosemicarbazide to give the corresponding hydrazone and thiosemicarbazone. The reaction with arylhydrazines yields 3-(-arylazobenzylidene)-1,2,3,4-tetrahydroquinoxalin-2-ones which are tautomeric to the respective arylhydrazones. On heating in boiling acetic acid, the products of both types undergo intramolecular cyclocondensation with formation of 3-phenylpyrazolo[3,4-b]quinoxalines (3-phenylflavazoles). 3-Benzoyl-1,2-dihydroquinoxalin-2-one thiosemicarbazone gives rise to flavazole structure only in the presence of methyl 3-chloro-2-oxo-3-phenylpropionate as a trap of thiocarbamoyl moiety. The cyclization of 3-(-hydrazonobenzyl)-1,2-dihydroquinoxalin-2-one is accompanied by formation of quinoxalyl ketone azine.     

Simultaneous spectrofluorimetric determination of iron and manganese by a differential kinetic catalytic method

A kinetic method is presented for the simultaneous determination of iron(III) and manganese(II) based on the different reaction rates resulting from the catalytic effect of both metal ions on the oxidation of 2-hydroxybenzaldehyde thiosemicarbazone by hydrogen peroxide in an ammoniacal medium. The reaction is monitored spectrofluorimetrically at 440 nm and with excitation at 365 nm. Two sets of reaction conditions are established to maximize the effect of manganese compared to iron, and vice versa, and the data are evaluated from simultaneous equations. Mixtures of these metal ions at ng ml^?1 levels for iron/manganese ratios from 8:1 to 1:2 can be determined with an accuracy and precition of about 3% and 1%, respectively. The methods has been applied successfully to the determination of both metals in aluminium and copper alloys, beer, cheeses and soils.     

A new approach to suppress nonlinearity-transparency trade-off through coordination chemistry: syntheses and spectroscopic study on second-order nonlinear optical properties of a series of square-pyramidal zinc(II) complexes

Five new square-pyramidal coordination compounds L x Zn(acac)(2) (1-5) (acac = acetylacetonate; L is a variety of thiosemicarbazones: p-dimethylaminobenzaldehyde thiosemicarbazone (1), p-hydroxy-o-methoxybenzaldehyde thiosemicarbazone (2), p-methoxybenzaldehyde thiosemicarbazone (3), p-hydroxybenzaldehyde thiosemicarbazone (4), o-hydroxybenzaldehyde thiosemicarbazone (5)) have been synthesized and characterized by 1H NMR, IR, and elemental analysis. All of these compounds exhibit pretty wide transparent ranges in the visible region. Their electronic absorption spectra have been studied experimentally, and theoretically by ZINDO/S calculation. The latter has also been utilized to estimate the extent of intramolecular charge transfer. The MOPAC software package has been used to evaluate their first-order molecular hyperpolarizabilities (beta). All beta values of the five coordination compounds are larger than those of the corresponding thiosemicarbazones. And complex 1 shows the largest beta(0) (39.1 x 10(-30) esu) in the series.     

Metal-catalysed oxidation processes in thiosemicarbazones: new complexes with the ligand N-{2-([4-N-ethylthiosemicarbazone]methyl)phenyl}-p-toluenesulfonamide

The coordination behaviour of a new thiosemicarbazone Schiff-base building block, N-{2-([4-N-ethylthiosemicarbazone]methyl)phenyl}-p-toluenesulfonamide, H2L1 (1), incorporating a bulky tosyl group, towards Mn II, Fe II, Co II, Ni II, Cu II, Zn II, Cd II, Ag I, Sn II, and Pb II has been investigated by means of an electrochemical preparative procedure. Most metal complexes of L1 have the general formula [M(L1)]2.nX (M=Mn, Fe, Co, Ni, Cu, Cd, Pb; n=0-4, X=H2O or CH3CN), as confirmed by the structure of [Pb(L1)]2 (15), in which the lone pair on lead is stereochemically active. This lead(II) complex shows an intense fluorescence emission with a quantum yield of 0.13. In the case of silver, the complex formed was found to possess a stoichiometry of [Ag2(L1)]2.3H2O. During reactions with manganese and copper metals, interesting catalysed processes have been found to take place, with remarkable consequences regarding the ligand skeleton structure. In synthesising the manganese complex, we obtained an unexpected dithiolate thiosemicarbazone tosyl ligand, H2L2, as a side-product, which has been fully characterised, including by X-ray diffraction analysis. In the case of copper, the solid complex has the formula [CuL1]2, but the crystallised product shows the copper atoms coordinated to a new cyclised thiosemicarbazone ligand, H2L3, as in the structures of the complexes [Cu(L3)]2.CH3CN (8) and [Cu(L3)(H2O)]2.CH3CN.H2O (9). The zinc complex [Zn(L1)]4 (12) displays a particular tetranuclear zeolite-type structure capable of hosting small molecules or ions, presumably through hydrogen bonding.     

Column preconcentration of trace manganese with the ion pair of 2-nitroso-1-naphthol-4-sulfonic acid tetradecyldimethylbenzyl-ammonium chloride supported on naphthalene and determination by derivative spectrophotometry

A column preconcentration method has been developed for the determination of trace amounts of manganese by preconcentration on 2-nitroso-1-naphthol-4-sulfonic acid (nitroso-S)-tetradecyldimethylbenzylammonium (TDBA) naphthalene as an adsorbent using a simple funnel tipped glass tube. Manganese reacts with nitroso-S to form a water soluble brown colored chelate anion. The chelate anion forms a water insoluble Mn-Nitroso-S-TDBA ion pair on naphthalene packed in a column in the pH range 9.6-10.5 at a flow rate of 1-2 ml/min. The solid mass consisting of manganese complex and naphthalene is dissolved in 5 ml of dimethylformamide (DMF) and the metal determined by second derivative spectrophotometry. The calibration curve is linear in the concentration range 0.25-35.0 micrograms of Mn in 5 ml of the final DMF solution. Eight replicate determinations of 25 micrograms of standard manganese solution give a mean peak height of 4.0 with a correlation coefficient of 0.9995 and relative standard deviation of +/- 1.1%. The sensitivity was calculated to be 0.502(d2 A/d lambda 2)/microgram ml-1 from the slope of the calibration curve. The detection limit was 0.020 microgram ml-1 for manganese at the minimum instrumental settings (signal to noise ratio = 2). Various parameters effecting the method such as the effect of pH, volume of aqueous phase and interference of a number of metal ions on the determination of manganese have been evaluated to optimize the conditions for its determination in standard alloys and biological samples.     

Analytical studies using iodine-luminol chemiluminescence

Trace amounts of substances have been related to iodine consumption monitored by chemiluminescence from the iodine-luminol system. Iodine titrations of sulphite and arsenic(III) have been carried out at levels of 1.0 x 10(-7) and 5.0 x 10(-8)M with a precision and error of better than 1% on a day-to-day basis. A calibrated standard of 1.8 ppm SO(2) in air was analysed with a precision of +/-1.2%, and an error of 0.9%. A rate method has been developed based on the reaction between iodine and penicillin G; a linear range from 10(-8) to 10(-7)M was found, the precision being +/-9%.     

Spectral studies of products of reaction between phosphorylacetaldehyde thiosemicarbazones and bromoacetal

We have obtained thiazoline hydrobromides by reacting unsubstituted thiosemicarbazones of phosphoryl-acetaldehydes with bromoacetal. These thiazoline hydrobromides have the structure of the azine of phosphorylacetaldehyde and 1,3-thiazoln-2-one in the crystal phase. Their dissolution is accompanied by thiazoline-thiazole tautomeric conversion to the hydrobromide of phosphorylacetaladehyde thiazolylhydrazone. Reaction of the 2-methyl-substituted phosphorylacetaldehyde thiosemicarbazone with bromoacetal leaas to the hydrobromide of phosphorylacetaldehyde N-methyl-N-2-(1,3-thiazolyl)hydrazone, the thiazole structure of the heterocycle of this compound is also retained when it is dissolved, due to the impossibility of tautomeric conversions due to the structural features. In all cases, salt formation occurs at the endocyclic nitrogen atom. The conversion of salt-like compounds to free bases does not lead to a change in the thiazole structure of the heterocycle.Kazan State Technological University, Kazan 420015. Chemistry Department, King's College, University of London, The Strand, London, UK. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 837–844, June, 1996. Original article submitted April 8, 1996.     

A New Kinetic-Fluorimetric Method for the Determination of Silver Based on Its Inhibitory Effect on the Oxidation of 2-Hydroxybenzaldehyde Thiosemicarbazone with Hydrogen Peroxide Catalyzed by Iron (III)

Abstract

An indirect kinetic determination of silver based on its inhibitory effect on the oxidation of 2-hydroxybenzaldehyde thiosemicarbazone with hydrogen peroxide catalyzed by iron (III) is described. The reaction is followed spectrofluorimetrically by measurement of the initial rate at the wavelengths of the oxidation product (λ_exc=365nm, λ_em=440nm.). The calibration curves are linear between 50-400 ng.ml^?1 of silver with a precision of ± 2.3%. The proposed method has few interferences.     

Spectroscopic characterization of copper(II) complexes of indoxyl N(4)-methyl thiosemicarbazone

New copper(II) complexes of indoxyl thiosemicarbazone (ITSC) of general composition CuL2X2 (where L: ITSC; X: Cl-, NO3-, ClO4-, NCS-) have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibility measurements and spectral (electronic, IR, EPR, 1H NMR, Mass) studies. Cyclic voltammetry measurements show quasi-reversible Cu2+/Cu1+ couple. Various physico-chemical techniques suggest a tetragonal structure for these copper(II) complexes.     

Synthesis and Crystal Structure of a Mn(II) Complex with Thiosemicarbazone Derivative of Pyridine-3-carbaldehyde Showing Unusual Coordination Mode of Tridentate Thiosemicarbazone

1 INTRODUCTION Heterocyclic thiosemicarbazones as well as their metal complexes have been attracting considerable interest due to their biological activities, such as antiviral, antibacterial, antimalarial, antifungal, and antitumoral activities[1～5]. This prompted us to carry out structural studies of these complexes to provide a basis for understanding their behaviors in living systems. Although quite a number of investigations on the 2-heterocyclic thiosemicarbazones have ap- peared[6…     

Neutron-activation analysis of manganese in polysulphide materials

A fast non-destructive neutron-activation analysis method has been developed for manganese in polysulphide adhesives. Samples are irradiated for 20 min at a thermal flux of 2 x 10(10) n cm(-2) sec(-1). The net activity in the 0.845-MeV gamma peak of (56)Mn produced by the (n, gamma) reaction in the sample is compared with the activity obtained from a weighed amount of pure manganese irradiated at the same time. Samples containing 2-3% of manganese have been analysed with a relative standard deviation of 2.9%.     

Effectiveness of palladium as a chemical modifier for direct silver and manganese determination in cocaine and heroin by electrothermal atomic absorption spectrometry

Methods for the direct determination of silver and manganese in cocaine and heroin by electrothermal atomic absorption spectrometry using palladium as chemical modifier have been developed. Cocaine samples, 0.5 g, were dissolved in 2 ml of 35.0% (m/v), HNO(3) diluting to 10 ml with ultrapure water. A comparative study of palladium, magnesium nitrate, palladium-magnesium nitrate and nitric acid used as chemical modifiers was carried out, and it was found that palladium alone is adequate to stabilize silver and manganese at charring temperatures of 1000 and 1300 degrees C respectively. A study was made on the insertion of a cooling step before the atomization step, and this approach was not advantageous. Limits of detection of 2.3 and 6.9 microg kg(-1) were obtained for silver and manganese respectively. The analytical recovery oscillated between 95.9 and 103.6% for silver and between 99.7 and 103.0% for manganese. Finally, a study of some interferences and a study of the precision and analytical recovery of the amount of sample were also carried out.     

Solvent extraction of N-Cyclohexyl-N-Nitrosohydroxylamine (cnha) into some organic solvents and of the Cu(II)-cnha complex into methyl isobutyl ketone

The distribution equilibria of N-cyclohexyl-N-nitrosohydroxylamine (cnha) in the water-chloroform, water-hexane, water-methyl isobutyl ketone (MIBK) and water-isopentyl alcohol systems, and of the Cu(II)-cnha complex in the water-MIBK system have been studied. From the distribution data the dissociation and distribution constants of the reagent have been calculated; their values are pK(a) = 5.55 +/- 0.10; log K(DR) = 2.46 +/- 0.05 (chloroform), 1.76 +/- 0.11 (MIBK), 1.06 +/- 0.07 (hexane) and 1.48 +/- 0.06 (isopentyl alcohol). In the same way the values of the distribution and stability constants of the Cu(II) complex have been obtained; log K(DC) = 3.51; log beta(1) = 7.23 +/- 0.10 and log beta(2) = 12.00 +/- 0.08. For the determination of cnha in the aqueous phase saturated with MIBK, a spectrophotometric method based on the coloured complex formed by the reagent with Fe(III) has been established. Finally, an analytical method for Cu(II) by atomic-absorption spectrometry after its extraction with cnha into MIBK, is proposed. Its detection limit is 4.6 mug l ., its precision +/- 2.1% and its accuracy 97.5%. This method has been applied to the determination of the copper content in the surface water of the Congest River of Catalonia (Spain).     

Synthesis and Crystal Structure of a Mn(Ⅱ) Complex with Thiosemicarbazone Derivative of Pyridine-3-carbaldehyde Showing Unusual Coordination Mode of Tridentate Thiosemicarbazone

The title complex Mn(HL)4(NCS)2(CH3CH2OH)2 has been achieved via selfassembly by incorporating manganese(Ⅱ) into pyridine-3-carbaldehyde thiosemicarbazonate ligand,and characterized by elemental analysis and single-crystal X-ray diffraction study. The crystal crystallizes in triclinic, space group P1 with a = 8.896(2), b = 9.530(2), c = 14.520(4) (A), α =87.035(4), β= 88.112(4), γ= 69.434(4)°, V= 1150.9(5) (A)3, Z = 1, Mr = 984.17, Dc = 1.420 g/cm3,μ(MoKα) = 0.612 mm-1, F(000) = 511, the final R = 0.0574 and wR = 0.1547 for 2855 observed reflections with I ＞ 2σ(I). The complex contains one six-coordinated manganese ion connected by two thiosemicarbazide ligands, in which the thiosemicarbazone ligand acts as a monodentate ligand and coordinates to the center metal atoms via the pyridyl nitrogen atoms, two ethanol molecules and two isothiocyanic anions to give rise to a mononuclear structure. The coordination of a potentially tridentate thiosemicarbazone in manganese(Ⅱ) complex without using its sulfur and imine nitrogen sites is unusual. Hydrogen bonds existing in the complex link the different components to stabilize the crystal structure.     

Simple high-performance liquid chromatography method for alpha-tocopherol measurement in Rosmarinus officinalis leaves. New data on alpha-tocopherol content.

A simple HPLC method for vitamin E (alpha-tocopherol) measurement in the leaves of Rosmarinus officinalis has been developed and validated. It has enabled new data for alpha-tocopherol content to be established. The leaves, recently harvested, were dried in a microwave oven and crushed; then, alpha-tocopherol was directly extracted from portions of ground material with acetone, by probe sonication. After centrifugation the acetonic extract was analysed by HPLC with ergocalciferol (vitamin D2) added as internal standard and a gradient elution with a Nucleosil C18 column at 35 degrees C. Validation parameters of the method can be considered adequate. For standards: linearity is r=0.999, recovery is 100+/-2%, intra-assay precision has RSD=+/-3% and inter-assay precision has RSD=+/-6%. For samples: linearity is r=0.99, recovery: 93+/-7%, intra-assay precision has RSD=+/-4% and inter-assay precision has RSD=+/-7%.     

Bonding trends of thiosemicarbazones in mononuclear and dinuclear copper(I) complexes: syntheses, structures, and theoretical aspects

Reactions of copper(I) halides with a series of thiosemicarbazone ligands (Htsc) in the presence of triphenylphosphine (Ph(3)P) in acetonitrile have yielded three types of complexes: (i) monomers, [CuX(eta1-S-Htsc)(Ph3P)2] [X, Htsc = I (1), Br (2), benzaldehyde thiosemicarbazone (Hbtsc); I (5), Br (6), Cl (7), pyridine-2-carbaldehyde thiosemicarbazone (Hpytsc)], (ii) halogen-bridged dimers, [Cu2(mu2-X)2(eta1-S-Htsc)2(Ph3P)2] [X, Htsc = Br (3), Hbtsc; I (8), furan-2-carbaldehyde thiosemicarbazone (Hftsc); I (11), thiophene-2-carbaldehyde thiosemicarbazone (Httsc)], and (iii) sulfur-bridged dimers, [Cu2X2(mu2-S-Htsc)2(Ph3P)2] [X, Htsc = Cl (4), Hbtsc; Br (9), Cl (10), pyrrole-2-carbaldehyde thiosemicarbazone (Hptsc); Br (12), Httsc]. All of these complexes have been characterized with the help of elemental analysis, IR, 1H, 13C, or 31P NMR spectroscopy, and X-ray crystallography (1-12). In all of the complexes, thiosemicarbazones are acting as neutral S-donor ligands in eta()S or mu2-S bonding modes. The Cu...Cu separations in the Cu(mu2-X)2Cu and Cu(mu2-S)2Cu cores lie in the ranges 2.981(1)-3.2247(6) and 2.813(1)-3.2329(8) Angstroms, respectively. The geometry around each Cu center in monomers and dimers may be treated as distorted tetrahedral. Ab initio density functional theory calculations on model monomeric and dimeric complexes of the simplest thiosemicarbazone [H2C=N-NH-C(S)-NH2, Htsc] have revealed that monomers and halogen-bridged dimers have similar stability and that sulfur-bridged dimers are stable only when halogen atoms are engaged in hydrogen bonding with the solvent of crystallization or H2O molecules.     

Kinetic spectrophotometric determination of nanogram levels of manganese by use of the salicylaldehyde guanylhydrazone-hydrogen peroxide system

A kinetic method is described for determining trace amounts of manganese(II), based on its catalytic effect on the oxidation of salicylaldehyde guanylhydrazone by hydrogen peroxide. The reaction is followed spectrophotometrically by measuring the rate of change of absorbance at 505 nm. The calibration graph is linear in the range 8-80 mug/l. with a relative error of +/- 1%. The method has been applied to the determination of manganese in various samples.