The polarography of azo dyes and their metal complexes

Summary Studies are reported of the polarography of iron and nickel in the presence of solochrome violet RS. It is shown that complexes with iron are formed at pH values in the region of 4.5 and 6.5. The former has a dye-iron combining ratio of 21, while that at pH 6.5 is 41. Simultaneous polarography of iron and aluminium in solochrome violet RS solution showed that at pH 3.5 distinct steps for both elements may be obtained, but they are not sufficiently separated for quantitative purposes.The polarographic behaviour of nickel is shown to be different from the other species studied. No dye complex is formed at pH 4.5 in acetate buffer while that at pH 6.5 has a dye-nickel combining ratio of 21. In borate buffer, however, complexes at pH 4.5 and pH 6.5 are obtained, which yield step heights proportional to nickel concentration. Reproducible values for the combining ratios of these two species were not obtained.The reactions of these elements are discussed and reference to certain theoretical aspects is made.

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Zusammenfassung Es wird über Untersuchungen zur polarographischen Bestimmung von Eisen und Nickel in Gegenwart von Solochromviolett RS berichtet. Komplexe mit Eisen werden bei pH 4,5 bzw. 6,5 mit dem Verhältnis Farbstoff- Fe=21 bzw. 41 gebildet. Bei der gleichzeitigen Polarographie von Eisen und Aluminium in einer Lösung von Solochromviolett RS werden bei pH 3,5 deutliche Stufen für beide Elemente erhalten, jedoch ist für quantitative Zwecke die Trennung nicht ausreichend. Nickel weist ein abweichendes polarographisches Verhalten auf: In Acetatpuffer wird bei pH 4,5 kein Komplex mit dem Farbstoff gebildet, bei pH 6,5 wird ein Komplex mit dem Verhältnis Farbstoff:Ni=21 gebildet; in Boratpuffer jedoch erhält man Komplexe bei beiden pH-Werten, die der Ni-Konzentration proportionale Stufenhöhen ergeben. Reproduzierbare Werte für die Verbindungsverhältnisse dieser beiden Arten konnten jedoch nicht erhalten werden. Die Reaktionen der genannten Elemente werden diskutiert und einige theoretische Hinweise gegeben.

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Dedication. This paper is dedicated to Prof. Dr. M. von Stackelberg with grateful appreciation of his friendly interest, inspiration and encouragement, and with thanks for his many acts of kindness.

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Dedicated to Prof. Dr. M. von Stackelberg on his 70th birthday.     

Unsaturated polycarbonyl compounds and their metal complexes

A new series of unsaturated polycarbonyl compounds in which the keto group attached to olefinic linkage has been synthesized by the reaction of acetoacetanilide and aromatic aldehydes under specified conditions. The existence of these compounds predominantly in the intramolecularly hydrogen bonded enol form has been well demonstrated from their IR, ¹H NMR and mass spectral data. Details on the formation of their complexes with Ni(II), Cu(II), and Zn(II) and their nature of bonding are discussed on the basis of analytical, IR, ¹H NMR and mass spectral data.     

Synthesis and spectral characterization of some new azo dyes and their metal complexes

A series of azo-metal chelate dyes have been synthesized by coupling substituted o-nitroaniline and p-t-/s-butylphenol. The spectral characterization of the azo dyes containing o-hydroxy group and azo-metal(II) chelate [metal(II): Cu, Ni, Co] dyes by IR spectra, UV–VIS spectra, NMR spectra, elemental analysis and magnetic susceptibility techniques are reported. The stoichiometry of the azo-metal chelates was determined by the spectroscopic titration method to be 1:2 (ML₂).     

Thermal studies of some purine compounds and their metal complexes

The mechanism of the decomposition of the entitled compounds and their complexes is studied. Adenine, its Schiff base of salicylaldehyde, and its azo resorcinol derivatives are ended with carbon. However, oxalonitrile compound is appeared as a final product for adenine acetylacetone and an intermediate for adenine. The thermodynamic parameters of the decomposition reaction were evaluated and discussed. The change of entropy values, ΔS ^#, showed that the transition states are more ordered than the reacting complexes. The thermal processes proceed in complicated mechanisms where the bond between the central metal ion and the ligands dissociates after losing small molecules such as H₂O, NH₃, or HCl. In most cases, the free radical species of the ligands are assigned to exist through decomposition mechanisms. The copper adenine and nickel salicylaldehyde complexes are ended with the metal as a final product. However, the cobalt adenine, its acetylacetone, its salicylaldehyde, cadmium and mercury guanine complexes are ended with metal oxides.     

Spectroscopic studies on some azo compounds and their cobalt, copper and nickel complexes

Synthesis and characterization of [o-carboxy phenylazo] moiety of barbituric acid, thiobarbituric acid, thiouracil, citrazinic acid, and disodium chromotropate and their complexes derived from cobalt (II), nickel (II), and copper (II) salts were done. The stereochemistry and the mode of bonding of the complexes were achieved based on elemental analysis, NMR, UV-Vis, IR and ESR. The dissociation constants of the free azo ligands are evaluated by spectrophotometric methods.     

Reaction of 3,4-diaminofurazan with carbonyl compounds and their metal complexes

It is shown that when 3,4-diaminofuranzan reacts with formic acid under various conditions there is, along with the mono- and diformylation, an intermolecular reaction leading to a polymeric compound. The diamine under consideration forms a monoazomethine with salicylaldehyde but a bis (azomethine) complex with the salicylaldehydate of divalent nickel.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 666–669, May, 1986.     

Synthesis, characterization and thermal studies on metal complexes of new azo compounds derived from sulfa drugs

Four new azo ligands, L1 and HL2-4, of sulfa drugs have been prepared and characterized. [MX(2)(L1)(H(2)O)(m)].nH(2)O; [(MX(2))(2)(HL2 or HL3)(H(2)O)(m)].nH(2)O and [M(2)X(3)(L4)(H(2)O)].nH(2)O; M=Co(II), Ni(II) and Cu(II) (X=Cl) and Zn(II) (X=AcO); m=0-4 and n=0-3, complexes were prepared. Elemental and thermal analyses (TGA and DTA), IR, solid reflectance spectra, magnetic moment and molar conductance measurements have accomplished characterization of the complexes. The IR data reveal that HL1 and HL2-3 ligands behave as a bidentate neutral ligands while HL4 ligand behaves as a bidentate monoionic ligand. They coordinated to the metal ions via the carbonyl O, enolic sulfonamide S(O)OH, pyrazole or thiazole N and azo N groups. The molar conductance data reveal that the chelates are non-electrolytes. From the solid reflectance spectra and magnetic moment data, the complexes were found to have octahedral, tetrahedral and square planar geometrical structures. The thermal behaviour of these chelates shows that the water molecules (hydrated and coordinated) and the anions are removed in a successive two steps followed immediately by decomposition of the ligand in the subsequent steps. The activation thermodynamic parameters, such as, E*, DeltaH*, DeltaS* and DeltaG* are calculated from the TG curves applying Coats-Redfern method.     

Supramolecular compounds of azo dyes derived from 1-phenylazo-2-naphthol and their nickel and copper complexes

In this study, experimental techniques including Raman, infrared and X-ray crystal diffraction, as well as quantum chemistry calculations, are used to investigate two new azo dyes supramolecular complexes: 1-phenylazo-2-naphthol (Sudan I) with nickel(II) ion and 1-(2,4-xylylazo)-2-naphthol (Sudan II) with copper(II) ion. The crystallographic structures have been solved for bis-1-(pheny-l-azo)-2-naphtholatenickel(II) and bis-1-(2,4-xylylazo)-2-naphtholatecopper(II) complexes, revealing the presence of supramolecular interactions, such as the centroid–centroid π-stacking interactions and CH…π hydrogen interactions. These weak intermolecular interactions appear to play an important role on the crystal structure stability for both compounds. Density functional theory calculations at B3LYP/6-311++G(d,p) level were performed in order to help understanding such molecular interactions and to assign the vibrational spectra. The experimental and theoretical data have allowed the analysis of the packing forces, revealing charge accumulation at key molecular regions.     

New azo derivative and their divalent metal ion complexes: Synthesis,characterization, and evaluation of their antibacterial activity

A new azo derivative 3-((4-H1benzo[d]imidazole-2-yl)-4-hydroxy benzaldehyde was prepared by reaction of benzimidazole derivative with 4-hydroxy benzaldehyde. The all-final compounds were diagnosis and determined the structure of these compounds using a variety of spectroscopic methods, including 1H-NMR, FT-IR, UV-Vis, mass spectrometry magnetic susceptibility and atomic absorption spectroscopy. The results showed that all metal ion complexes have an octahedral shape. Antimicrobial activity of the ligand and its metal ion complex had been tested against some selected microorganism such Streptococcus pyogenes a species of Gram-positive and Pseudomonas aeruginosa is a common bacterium gram-negative, all prepared compounds displayed a strong antibacterial activity. Taken together, the results of the current study indicated that the new Azo derivative and their divalent metal ion complexes could be used as a future strategy for other biomedical applications.     

Direct electrochemical and chemical syntheses, structures, and properties of metal complexes of azo compounds with an additional azo group in the amine fragment

New complexes of Cu(II), Co(II), and Ni(II) with 1-phenyl-3-methyl-4-[(4-phenylazophenyl)hydrazono]-5H-pyrazol-5-one and 1-phenyl-3-methyl-4-[4-methyl-2-(4-methylphenylazophenyl)hydrazono]-5H-pyrazol-5-one are synthesized by the chemical and electrochemical methods and characterized by IR, ¹H NMR, and EXAFS spectroscopy and X-ray diffraction analysis. Depending on the complexing metal and position of the additional azo group, the latter is involved or not in coordination with the metal to form heterounit five- and six-membered metallocycles.     

Silver and palladium complexes of some aromatic azo and azoxy compounds

The complexing ability of derivatives of azobenzene (I) is well known (I) and responsible for the production of a wide variety of dyestuffs and analytical chemicals. While the azo group generally participates in the coordination, the determination of the degree of its interaction is complicated by other functional groups which are also coordinated with the transition metal. In a previous publication (2), we reported the preparation of the silver and palladium complexes of benzo[c]cinnoline (II) and proposed that these results might be used to explain the electron donor properties of azobenzene. We are now reporting the preparation of some additional complexes with ligands containing the azo group.     

X-ray diffraction study of benzothiacrown compounds and their complexes with heavy metal cations

The structures of a series of substituted benzothiacrown compounds containing the dithia-15-crown-5, dithia-18-crown-6, or monothia-15-crown-5 fragment and their complexes with Ag⁺ and Pb2⁺ ions were studied by X-ray diffraction. In free benzothiacrown compounds, the sulfur atoms are preferably located outside the macrocyclic cavity, and their lone electron pairs (LEPs) point away from the center of the macrocycle, which is unfavorable for the formation of inclusion complexes. Flexible macrocyclic fragments can change their conformations in accord with the coordination requirements of heavy metal cations. As a result, benzothiacrown compounds involved in complexes adopt a crown conformation, in which LEPs of all hetero-atoms point toward the cation. The sulfur atoms are involved in coordination of Ag⁺ to a greater degree than the oxygen atoms due to high affinity of soft sulfur atoms for silver cations. On the contrary, the sulfur and oxygen atoms are involved to approximately the same degree in coordination of Pb2⁺ ions. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 967–976, May, 2007.     

Voltammetric and potentiometric studies of some sulpha drug-Schiff base compounds and their metal complexes

The electrochemical behavior of some sulpha drug-Schiff bases at a mercury electrode was examined in the Britton-Robinson universal buffer of various pH values (2.5–11.7) containing 20% v/v) of ethanol using DC-polarography, cyclic voltammetry and controlled-potential electrolysis. The DC-polarograms and cyclic voltammograms of the examined compounds exhibited a single, 2-electron, irreversible, diffusion-controlled cathodic step within the entire pH range which is attributed to the reduction of the azomethine group-CH=N- to -CH₂-NH-. The symmetry transfer coefficient (α) of the electrode reaction and the diffusion coefficient (D ₀) of the reactant species were determined. The electrode reaction pathway of the compounds at the mercury electrode was suggested to follow the sequence: H⁺, e⁻, e⁻, H⁺. The dissociation constant of the sulpha drug-Schiff bases, the stability constant and stoichiometry of their complexes with various divalent transition metal ions (Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) were determined potentiometrically at room temperature.      

Polarography of metal-gallic complexes

The polarographic behavior of metal ions in perchlorate media containing gallic acid is described. Tungsten(VI) forms a complex with gallic acid which yields a single wave in these media, useful in the polarographic determination of tungsten. Evidence for complexation of chromium(III), copper(II), iron(III), molybdenum(VI), uranium(VI), vanadium(V), tungsten(VI), praseodymium(III), samarium(III), neodymium(III) and gadolinium(III) is obtained and the behavior of these metal ions is summarized.     

Organic azo complexes of molybdenum and their reactions with electrophiles

Organic azo(1) and N,N-disubstituted hydrazido-N'(2) complexes of molybdenum have been prepared by the reactions of certain molybdenum-oxo complexes with hydrazines.     

Polarography of alicyclic compounds

A review of the polarography of alicyclic compounds is presented.     

Polarography of aliphatic compounds

A review of the polarography of aliphatic compounds is presented.     

Polarography of heterocyclic compounds

The literature data on the principles of the electrochemical reduction of heteroethylene and heteroparaffin compounds (pyrazoline, diazepine, diaziridine, pyran, pyridazone, aziridine, oxaziridine, and other derivatives), cyclic anhydrides, imides, and hydrazides of acids on a dropping mercury electrode are correlated. In addition, the effect of substituents attached to the heterocyclic ring on the polarographic behavior of heterocycles is analyzed.