Heterocyclic Azo Dyes Research Articles

Thorium(IV) and uranium(VI) complexes with some heterocyclic azo dyes in absolute ethanol

Thorium(IV) and uranium(VI) chelate complexes with PAN, PAR, TAN and TAR have been studied in absolute ethanol. The uranyl ion forms complexes with PAN, PAR, TAN and TAR in the metal to ligand molar ratio of 1:1. Thorium(IV) forms complexes with PAR, TAR and TAN in the molar ratio of 1:2. In case of Th(IV)-PAN complexes the molar ratio is 1:2.4. The stability constants for all the above complexes have been worked out using the mole ratio method. The kinetics of aquation of Th(IV)-PAN complexes indicate that PAN acts as a tridentate ligand.

The use of 2-(2-hydroxyphenylazo)-7-oxo-5,5-dimethyl-4,5,6,7-tetrahydrobenzothiazole as an extractant for Cu(II), Ni(II), Co(II), Pb(II) and Cd(II)

The heterocyclic azo dye, 2-(2-hydroxy-5-ethylphenylazo)-7-oxo-5,5-dimethyl-4,5,6,7-tetrahydrobenzothiazole (I), was prepared. The acid-base and optical parameters of the azo dye were found spectrophotometrically and the molar absorption coefficients and concentration dissociation constants were determined. The formation of the chelates of compound (I) with Cu(II), Ni(II), Pb(II) and Cd(II) was studied. The molar absorption coefficients and stability constants of the chelates were determined by calculations, graphical and logarithmic analysis, based on data from the A = f(pH) curves. The region of optimal extraction and the extraction constants were found for the chelates of I with Cu(II), Ni(II), Co(II) and Pb(II).

Heterocyclic Azo Dyes as the Chromogenic Reagents for the Extraction-Photometric Determination of Silver(l)

Heterocyclic Azo Dyes as the Chromogenic Reagents for the Extraction-Photometric Determination of Silver(l)

The reactions of gallium, indium and thallium with 2-(2-pyridylazo)-1-naphthol-4-sulphonic acid and their spectrophotometric determination

The complex equilibria of gallium, indium and thallium(III) with analytically important 2-(2-pyridylazo)-1-naphthol-4-sulphonate were studied spectrophotometrically using graphical analysis of the absorbance curves and minimization procedures for the absorbance data using the SPEKTFOT program on the Tesla 200 computer. The study yielded a complete picture of the reaction mechanism of these elements with heterocyclic azodyes. Optimum conditions for the spectrophotometric determination of gallium, indium and thallium using this reagent were found.

Spectrophotometric determination of cyanide ions through ligand exchange reaction in solution

A simple spectrophotometric method for the determination of trace amounts of cyanide ions in aqueous medium, using a heterocyclic azo dye complexed with mercury(II) for the first time, is described. The visual comparative method has been used in which a stronger complexing anion displaces a coloured reagent from the metal-ligand complex. Ammonium (2′-amino-3′-hydroxy-pyridyl-4′ azo)benzene-4-arsonate (AHP-4A) complexed with mercury(II) has been used for the determination of 0.13–1.46μg/ml of cyanide ions with fair accuracy. The anion has also been determined, when cyanide ion reacts with mercury(II)-(AHP-4A) complex, probably forming a bridged complex. The increase in absorbance is proportional to the cyanide ion concentration in the range of 0.04–0.37μg/ml, but this method is not very precise. The effect of foreign ions has also been studied. The sensitivities of other mercury(II) complexes in the determination of cyanide ions have been compared.

The use of chelates of copper, nickel, cobalt, cadmium and zinc with heterocyclic azodyes in the AAS determination of these elements

Of the group of seven pyridyl, thiazolyl and quinolyl azodyes, 2-(2-pyridylazo)-1-naphthol was found to be the most useful for the extraction concentration of traces of copper, nickel, cobalt, cadmium and zinc in methyl isobutyl ketone and for their final determination by atomic absorption spectrophotometry with an acetylene-air flame or using a graphite atomizer. Atomic absorption spectrophotometry was also found to be useful in the study of extraction equilibria and for finding the optimum extraction conditions for these elements with heterocyclic azodyes.

Reactions of palladium with some heterocyclic azodyes

Reactions of palladium with some heterocyclic azodyes

Polarography of heterocyclic azo compounds and their metal complexes

Summary The polarographic behaviour of a wide range of pyridylazo and thiazolylazo dyes has been studied and several differences observed between the electrode reactions of these heterocyclic compounds and their benzene or naphthalene counterparts. The hydrazo derivatives of the heterocyclic dyes are more stable with respect to disproportionation, which is attributed to the strongly electron-attracting properties of the pyridyl and thiazolyl groups. In addition their disproportionation is base-catalyzed, whereas earlier studies showed that aromatic azo dyes undergo an acid-catalyzed reaction. Hammett substituent constants were calculated for a variety of heterocyclic groups. Half wave potential shifts were observed for several heterocyclic azo dyes in the presence of nickel and iron(III) ions, and the height of the metal-dye complex wave was proportional to metal concentration. Aluminium did not produce a shift with any of the dyes studied, which enables nickel or iron to be determined in the presence of an excess of aluminium.

A contribution to the determination of some anions via titration with a lead(II) nitrate solution using heterocyclic azo dyes as indicators

The determination of molybdate, phosphate, tungstate, and sulfate via titration with lead(II) nitrate. using 3-(2-pyridylazo)resorcinol, 4- (2- thiazolylazo) resorcinol, 2-(2-thiazolylazo)-4-methoxyphenol, and 2-(2- pyridylazo)-1-naphthol-4-sulphonic acid as indicators, was studied and the precision, accuracy, and applicability of the individual methods were evaluated. (auth)

Heterocyclic azo-dyes derived from 1-naphthol-4-sulfonic acid as metallochromic indicators

Analytical reactions and acid-base equilibria of three N-heterocyclic az o-dyes, derived from 1-naphthol-4-sulfonic acid, were studied in various media. The dyes proved to be good indicators of the equivalence point for EDTA titrations and for the photometric microtitration of copper with EDTA. The course of model titrations as well as the accuracy and correctness of the evaluation of the end point were followed visually, spectrophotometrically, and potentiometrically. (auth)

O-Amino heterocyclic azo-dyes as analytical reagents—II Spectrophotometric determination of cobalt with 3-[(5-chloro-2-pyridyl)azo]-2,6-diaminopyridine

Cobalt(II) and 3-[(5-chloro-2-pyridyl)azo]-2,6-diaminopyridine (5-Cl-PADAPy) in slightly acid, neutral or alkaline media form a blue complex which is very stable even in the presence of mineral acids. The complex has two absorption maxima, at 575 and 620 nm. in 1.2 M hydrochlororic acid. The system conforms to Beer's law; the optimal range for a 1-cm cell is 0·2–1·2 ppm cobalt. Milligram amounts of common anions and cations do not interfere. The molar absorptivity is 3·69 × 10 4 1.mole −1.cm −1 at 620 nm.

Heterocyclic Azo Dyes in Complex Chemistry and in Analytical Chemistry

Heterocyclic Azo Dyes in Complex Chemistry and in Analytical Chemistry

Heterocyclic Azo Dyes by Oxidative Coupling

AbstractNew findings in the field of oxidative coupling reactions are reported. These involve: extension of this type of reaction to amidrazone system displaying (vinylogous) tautomerism and to unsymmetrical diarylhydrazines; elucidation of the coupling mechanism for these arylhydrazines and for the amidrazone systems previously described; the properties of some dyes, complexed with heavy metals, and the synthesis of tetraazapentamethine and penta‐azapentamethine dyes.