Complexation equilibria and spectrophotometric determination of zinc (II) with 2-(4′-methyl-2′-thiazolylazo)-4,6-dimethylphenol

2-(4′-methyl-2′-thiazolylazo)-4,6-dimethylphenol has been synthesized and its acid—base behaviour (pK_a1=0.03 ± 0.01, pK_a2=9.70±0.09) and complexation equilibria with zinc (logβ₁₀₁=6.70±0.04, logβ₁₀₂ = 13.70±0.02) studied in a 40% (v / v) ethanol—water medium at I=0.25 M NaClO₄. A spectrophotometric method for the determination of 0.2–1.5 ppm of zinc has been developed (ε=1.83 × 10⁴ 1. mol⁻¹ cm⁻¹ at 590 nm) and applied to its determination in lubricating oils.     

Spectrophotometric determination of acidity constants of 4-(2′-thiazolylazo)-resorcinol (TAR) in water-organic mixtures

<正>The acidity constants of TAR in different water-organic solvent binary mixtures at 25℃have been determined spectrophotometrically. DATa ANalysis(DATAN) program was used for calculations of the acidity constants and pure spectra of all formed species and their concentration distribution diagram in applied pH interval.Results show that there are a fairly inverse relationship between acidity constants and the mole fraction of the organic solvent in the binary mixtures.Effects of solvent composition on the pK_as and pure spectrum of each component are also discussed.     

A Spectrophotometric Study of Complexation Between Nickel(II) and 4-(5′-Methyl-3′-Isoxazolylazo)Resorcinol

Abstract

The complexation equilibria between Ni(II) and 4-(5′-methyl-3′-isoxazolylazo)resorcinol have been spec-trophotometrically studied in a 20% (v/v) ethanol-water medium at 0.1M NaCIO₄ ionic strength and species NiHR (log β₁₁₁ = 14.83 ± 0.05), NiR (log β₁₀₁ = 9.32 ± 0.04) and NiR₂ (log β₁₀₂ = 17.84 ± 0.05) are established.     

Spectrophotometric and thermal lens determination of aluminum with 3-sulfo-5-nitro-4′-diethylamino-2,2′-dihydroxyazobenzene

The conditions of the spectrophotometric and thermal lens determination of aluminum with sulfo-5-nitro-4′-diethylamino-2,2′-dihydroxyazobenzene have been compared. The limit of spectrophotometric detection of aluminum in aqueous solutions has been found to be 8 ng/mL. On the basis of the conditions of spectrophotometric determination, the conditions for thermal lens determination have been proposed (532.0 nm, exciting radiation power of 42 mW); they provide a decrease of the detection limit down to 0.6 ng/mL and an increase of the sensitivity coefficient by an order of magnitude. It has been shown that, in the case of the thermal lens determination of aluminum in water-organic mixtures (50 vol % of dimethyl sulfoxide or 30 vol % acetonitrile), the sensitivity coefficient is respectively 9.1 and 6.3-fold higher as compared with the thermal lens determination in water. As a result, the detection limits are reduced 2.5 and 10-fold, respectively. Aluminum has been determined by thermal lens spectrophotometry in Moscow’s tap water using the standard addition method, its concentration being 0.79 ± 0.07 mg/L, which is above the threshold limit value of the aluminum content of drinking water.     

Syntheses and crystal structures of cobalt(II) and zinc(II) complexes with 4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate

Abstract Sodium 4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate (1) is synthesized by the sulfonation of 6-hydroxybiochanin A and its structure is characterized by elemental analysis, ¹H-NMR, and IR spectroscopy. It is assembled with cobalt(II) or zinc(II), hexaquacobalt(II) bis(4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate) tetrahydrate (2) and hexaquazinc(II) bis(4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate) tetrahydrate (3) are obtained and characterized by IR spectroscopy. Simultaneously, their three-dimensional structures are determined by single-crystal X-ray analysis. It turns out that 2 and 3 are isomorphous and crystallize in the triclinic crystal system, space group P-1. Hydrophilic regions are defined by O–H···O hydrogen bonds involving the coordinated water molecules, the included water molecules, and sulfonate groups. Aromatic π...π stacking interactions assemble the isoflavone skeletons into columns and these columns formed hydrophobic regions. The sulfonate group is an important bridge as a structural link between the hydrophilic regions and the hydrophobic regions. Hydrogen bonds, π...π stacking interactions and the electrostatic interactions assemble 2 and 3 into three-dimensional network structures. Graphical abstract Sodium 4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate (1) is synthesized and assembled with cobalt(II) or zinc(II). Hexaquacobalt(II) bis(4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate) tetrahydrate (2) and hexaquazinc(II) bis(4′-methoxy-5,6,7-trihydroxyisoflavone-3′-sulfonate) tetrahydrate (3) are obtained and determined by single-crystal X-ray analysis. It turns out that 2 and 3 are isomorphous and assembled into three-dimensional network structures, characterized by hydrophilic regions defined by hydrogen bonds involving the coordinated water molecules, the included water molecules, and the sulfonate groups and by hydrophobic columns, formed by the isoflavone skeletons, interacting through π...π stacking interactions.      

2,4′-Bipyridyl complexes with cobalt(II) and nickel(II)

Summary Complexes of empirical formulae [ML₂Cl₂(OH₂)₂], [CoL₂Br₂(OH₂)₂]L·4H₂O, [NiL₂Br₂(OH₂)₂]L₂·2H₂O, [ML₂(OH₂)₄]L₂(NO₃)₂ and [ML₄(OH₂)₂](ClO₄)₂·2H₂O (M = Co^II, Ni^II, L = 2,4-bipyridyl) were synthesized and characterized by elemental and spectral analyses. The thermal decomposition of the complexes was also investigated.Author to whom all correspondence should be directed.     

Complexes of N-aroyl-N′-thiobenzohydrazide with cobalt(II), nickel(II) and zinc(II)

Summary New potential tetradentate ligands, N-benzoyl-N-thiobenzohydrazide (H₂BTBH) and N-salicyl-N-thiobenzohydrazide (H₂SBTH) have been prepared and characterized. Their complexes with Co^II, Ni^II and Zn^II have been prepared and characterized on the basis of elemental analyses, magnetic susceptibility measurements, and u.v.-vis., i.r. and ¹H-n.m.r. spectral studies. The bonding and stereochemistries of the complexes are discussed. H₂BTBH, H₂SBTH and the complexes have been screened towards a number of bacteria.     

Synthesis and Crystal Structure of 4-Phenyl-5-(1′- t-butyl-5′-methyl-4′-pyrazolyl)-1,2,4-triazol-3-thione

The crystal structure of 4-phenyl-5-(1′-t-butyl-5′-methyl-4′-pyrazolyl)-1,2,4-triazol- 3-thione 5 (C16H19N5S, Mr = 313.42) has been determined by single-crystal X-ray diffraction analysis. The crystal belongs to monoclinic, space group P21/c with a = 6.680(2), b = 27.44(1), c = 9.388(4)(A。), β = 106.738(6)°, V = 1648(1)(A。)3, Z = 4, Dc = 1.263 g/cm3, μ= 0.200 mm-1, F(000) = 664, R = 0.0608 and wR = 0.1176. The results confirmed that 5 can be assigned to the thione tautomeric form.     

Complexation of the zinc(II) ion with 2,2′-bipyridine and 1,10-phenanthroline in 4-methylpyridine and solvation structure of the manganese(II), cobalt(II), nickel(II), and zinc(II) ions in 4-methylpyridine and 3-methylpyridine

Complexation of the zinc(II) ion with 2,2-bipyridine (bpy) and 1,10-phenanthroline (phen) has been calorimetrically studied in 4-methylpyridine (4Me-py) containing 0.1 mol dm^–3 (n-C₄H₉)₄NClO₄ as a constant ionic medium at 25°C. The formation of [ZnL]²⁺, [ZnL₂]²⁺, and [ZnL₃]²⁺ (L=bpy, phen), and their formation constants, reaction enthalpies and entropies were determined. Our EXAFS (extended X-ray absorption fine structure) measurements showed that the solvation structure of the manganese(II), cobalt(II), and nickel(II) ions is six-coordinate octahedral in 4Me-py and 3-methylpyridine (3Me-py), while that of the zinc(II) ion is four-coordinate tetrahedral in 4Me-py. Since [ZnL₃]²⁺ is expected to have an octahedral structure, a tetrahedral-to-octahedral structural change should take place at a certain step of complexation. The thermodynamic parameters, especially reaction entropies, indicate that the structural change occurs at the formation of [Zn(bpy)₂]²⁺ and [Zn(phen)]²⁺.     

Synthesis,characterisation and electrochemical study of 4,4′-bis(salicylideneimino) diphenylethane and its complexes with cobalt(II), copper(II) and cadmium(II)

We have prepared and characterised a new series of metal complexes obtained from 4,4-bis(salicylideneimino)diphenylethane (saldipH₂) and cobalt(II), copper(II) and cadmium(II) chlorides. In every case, the coordinating atoms are N and O. However, each compound has its own structure:[Co(saldip)]·2 H₂O is monomeric and a mononuclear species, [Cu₂(saldip)₂(H₂O)] is a binuclear complex and finally the cadmium complex is formulated as:[(CdCl₂)₂(saldipH₂)]·CdCl₂. An electrochemical study (cyclic voltammetry) indicates that the reduction, as well as the oxidation, of copper in [Cu₂(saldip)₂(H₂O)] proceeds in two steps. For the reduction of the two other complexes, two steps are indicated out: the first is attributed to the reduction of the metal and the second to the reduction of the coordinated ligands.     

Characterization and spectroscopic study of new complexes of Cd(II), Hg(II) and Pb(II) with the sodium salt of morin-5′-sulfonic acid

Solid compounds of Cd(II), Hg(II) and Pb(II) with the sodium salt of morin-5′-sulfonic acid (NaMSA) were obtained. The molecular formula of the complexes are: Cd(C₁₅H₈O₁₀SNa)₂?·?6H₂O, CdOH(C₁₅H₈O₁₀SNa)?·?4H₂O, Hg(C₁₅H₈O₁₀S)?·?4H₂O and Pb(C₁₅H₈O₁₀S)?·?3H₂O. Some of their physicochemical properties such as UV-Vis, infrared, ¹³C NMR and mass spectra, thermogravimetric analysis, and solubility were studied. On the basis of spectroscopic data NaMSA was bound to Cd²⁺ via 4C=O and 3C?–?oxygen and the Hg²⁺ and Pb²⁺ ions by 5C–OH, 4C=O and 3C–OH.     

Synthesis of N,N′-bis(isopropylaminoethyl)-1,10-phenanthroli ne- 2,9-dimethanamine and N,N′-bis(diethylaminoethyl)-1,10-phenanthroline -2,9-dimethanamine and potentiometric determination of the formation constants of their complexes with manganese(II), cobalt(II), copper(II) and zinc(II)

Two hexadentate compounds incorporating 1,10-phenanthroline and four alkylamino donors have been prepared. The protonation constants and the formation constants of dipositive ion (Mn2+, Co2+, Cu2+ and Zn2+) complexes have been determined in aqueous solution by pH titration at 25 ± 0.1 °C and I = 0.1 mol·dm–3 NaNO3.     

Synthesis,spectral and biological investigations of 5(2′-hydroxyphenyl)-3-(4-substituted-phenyl) pyrazolinates of cobalt(II) and their addition complexes with N,P donor ligands

5(2′-Hydroxyphenyl)-3-(4-substituted-phenyl)pyrazolinates of cobalt(II) of the type (C₁₅H₁₂N₂OX)₂Co [here substituted group X is–H,–Cl,–CH₃ or–OCH₃] have been synthesized by reaction of anhydrous cobalt(II)chloride with the sodium salt of the pyrazolines in 1 : 2 molar ratio. Their addition complexes with N and P donor ligands [2, 2′-bipyridine, 1, 10-phenanthroline and triphenylphosphine] were prepared in 1 : 1 molar ratio. The newly synthesized complexes were characterized by elemental analyses, molecular weight measurement, magnetic susceptibility, IR, electronic, ³¹P NMR and FAB mass spectra. All complexes are amorphous as determined by XRD. Tetrahedral geometry around cobalt(II) has been suggested, confirming the presence of two pyrazoline bidentate ligands, cobalt(II)5- (2′-hydroxyphenyl)-3-(4-substituted-phenyl)pyrazolinates. Upon ligand addition, pyrazoline changes to monodentate. The bidentate and monodentate behavior of pyrazoline ligands was confirmed by IR spectral data. The metal complexes and their adducts exhibit good antibacterial and antifungal activity, better than the pyrazolines.     

Spectrophotometric determination of uranium with 5-(2′-carboxyphenyl)azo-8-quinolinol in the non-ionic micellar medium of Triton X-100

Triton X-100, a non-ionic surfactant, has been used to sensitize the reaction of 5-(2-carboxyphenyl)azo-8-quinolinol with uranium in aqueous medium at pH 5.2–6.1 to form a wine red coloured complex. The micellar sensitization results in two and a half-times enhanced molar absorptivity enabling the determination of uranium in rock samples at ppm level, stability of the complex enhanced from 4 hours to at least 72 hours. Extraction of the complex is avoided making the procedure simple, rapid and easy in operation. The molar absorptivity and Sandell's sensitivity of the complex are 1.50·10⁴l·mol^–1·cm^–1 and 15.9 ng·cm^–2, respectively, at _max=568 nm. Beer's law is obeyed over the range 0–3.3 g·ml^–1 of uranium. An amount as low as 0.19 g·ml^–1 of uranium could be determined satisfactorily within a relative standard deviation of ±1.3%. The limits of determination and practical quantitation are 0.29 and 1.80 ppm, respectively. The method was applied to the determination of uranium in soil, stream sediment and rock samples.     

Transition metal(II) complexes of 1-(α-hydroxynaphthyl)-2-(3′-methyl-5′-mercapto-1′,2′,4′-triazole)-2-aza-ethane

Summary Binuclear metal complexes of the type [M(HMTE)-(H₂O)₂]₂, where HMTE=1-(-hydroxynaphthyl)-2-(3-methyl-5-mercapto-1,2,4-triazolc)2-aza-ethane and M-Cu^II, Co^II, Ni^II and Mn^II have been prepared and characterized. An octahedral geometry around the metals is proposed. The complexes have been screened as possible fungicides.     

Synthesis and crystal structure of new cobalt(II) and copper(II) complexes with deprotonated N -[2′-(4-methyl) pyrimidinyl]-2-nitrobenzenesulfonylurea

Cobalt(II) and copper(II) complexes with deprotonated N-[2′-(4-methyl)pyrimidinyl]-2-nitrobenzenesulfonylurea were synthesized and their structures were characterized by IR spectrum, elemental analysis and X-ray diffraction. The deprotonated sulfonylurea is a bidentate ligand to Co(II) or Cu(II) in octahedral geometry. In the packing diagrams of the complexes, C–H ··· O hydrogen bonds are observed. The UV and fluorescence spectra of the complexes are described, and the thermogravimetric analyses of the complexes were performed.     

Spectrophotometric study of the charge transfer complexes of 4′-nitrobenzo-15-crown-5 and benzo-15-crown-5 with iodine in nonaqueous solvents

The formation of charge transfer complex between iodine with 4’-nitrobenzo-15-crown-5（NB15C5） and benzo-15-crown-5 （B15C5） is investigated spectrophotometrically in chloroform and dichloromethane（DCM） solutions at 25℃.The pseudo-first-order rate constants for the transformation process were evaluated from the absorbance-time data and found to vary in the order of DCM > CHCl₃.The values of the formation constant,K_f,for each complex are evaluated from Benesi-Hilebrand equation. Stability of the resulting complex in two solvents was also found to vary in the order of DCM > CHCl₃.     

Syntheses and characterization of Zn(II), Cd(II) and Hg(II) complexes with 5-methyl-1-(2′-pyridyl)pyrazole-3-carboxamide (MP y P z CA) ligand

From the reaction between Zn(II), Cd(II) and Hg(II) with 5-methyl-1-(2′-pyridyl)pyrazole-3-carboxamide (MP _y P _z CA) in ethanol, the complexes [Zn(MP _y P _z CA)₂(NO₃)]⁺ [(NO₃)_0.60(ClO₄)_0.40]^?·H₂O, Cd(MP _y P _z CA)₂Cl₂ and Hg(MP _y P _z CA)(SCN)₂ were obtained. These compounds have been characterized by IR and CHN analyses. The structure of [Zn(MP _y P _z CA)₂NO₃]⁺[(NO₃)_0.60(ClO₄)_0.40]^?·H₂O has been solved by X-ray crystallography. The coordination environment around the Zn(II) may be described as a trigonal bipyramid in which the ligands are both bidentate, but coordinated differently. The coordination sphere is completed with the oxygen atom of a nitrate anion as a unidentate ligand.     

Potentiometric studies on the formation equilibria of binary and ternary complexes of cobalt(II) with adenosine-5′-mono-, -di-, and -triphosphate and some biologically important polybasic oxygen acids

Summary Potentiometric equilibrium measurements have been made for the interaction of adenosine-5-mono-,-di-, and -triphosphate, and Co(II) with biologically important secondary ligands (malic, maleic, succinic, tartaric, citric, and oxalic acid). The formation of various 1:1:1 mixed ligand complexes inferred from the potentiometric titration curves. Initial estimates of the formation constants of the resulting species and the acid dissociation constants ofAMP,ADP,ATP and the secondary ligand acids have been refined with a computer program. In some systems, the ternary complexes are found to be more stable than the corresponding binary ones. In some ternary systems studied, interligand interactions or some cooperativity between the coordinate ligands, possibly H bond formation, have been found to be most effective in deciding the stability of the complexes formed in solution. Stabilities of mixed ligand complexes increase in the orderAMP <ADP <ATP. With respect to the secondary ligands, the formation constants of the mixed ligand complexes decrease in the following order: succinic > maleic > tartaric > malic > citric > oxalic acid.

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Potentiometrische Untersuchung der Bildungsgleichgewichte von binären und ternären Komplexen von Kobalt(II) mit Adenosin-5-mono-, -di- und -triphosphat und einigen biologisch bedeutenden polybasischen Sauerstoffsäuren

Zusammenfassung Die Wechselwirkung vonAMP,ADP undATP mit Co(II) und einigen biologisch interessanten Sekundärliganden (Bernsteinsäure, Hydroxybernsteinsäure, Maleinsäure, Weinsäure, Zitronensäure und Oxalsäure) wurde bei 25°C und einer lonenstärke von 0.1M KNO₃ potentiometrisch untersucht. Die Titrationskurven zeigen das Vorliegen von Species der Zusammensetzung 1:1:1 an. Die geschätzten Bildungskonstanten der Komplexe und die Dissoziationskonstanten der Liganden wurden mittels eines Computerprogramms optimiert. In einigen der untersuchten Systeme sind die ternären Komplexe stabiler als die sekundären. Die Stabilität der Verbindungen hängt im wesentlichen von Interligandwechselwirkungen — möglicherweise der Ausbildung von Wasserstoffbrückenbindungen — ab. Die Stabilität der Komplexe mit gemischten Liganden steigt in der ReihenfolgeAMP <ADP <ATP und fällt entsprechend der Serie Bernsteinsäure > Maleinsäure > Weinsäure > Hydroxybernsteinsäure > Zitronensäure > Oxalsäure.