Investigation on structure and thermal behavior of 4,4′-dihydroxyazobenzene functionalized with epoxy groups

A new symmetric compound with azobenzene chromophore and epoxide groups, namely diglycidyl ether of 4,4′-dihydroxyazobenzene (DGEAB) was obtained and characterized. Its thermal behavior was monitored taking into account that many reactions of epoxides are carried out under heating. DGEAB was found to be stable up to 200 °C, but at higher temperature, its decomposition involves three step of degradation with the formation of an appreciable quantity of the char.     

Spectrophotometric study of the complexation equilibria of cobalt(II) with 4-(5′-methyl-3′-isoxazolylazo)-resorcinol and determination of cobalt(II)

The reaction of cobalt(II) with 4-(5′-methyl-3′-isoxazolylazo)-resorcinol (MIAR) in 4% v/v ethanol-water medium at I = 0.1 M (NaClO₄) was investigated spectrophotometrically. Graphical and numerical calculation methods were used to establish the equilibria in solution and to evaluate the stability constant of the complexes formed (log β₁₀₁ = 7.48±0.06, log β₁₁₁ = 12.77 max 12.99, log β₁₀₂ = 16.41±0.07). The optimum conditions for the spectrophotometric determination of Co(II) with MIAR were established and the method applied to its determination in some low alloy steels and hydrofining catalysts.     

Structural and thermal properties of rare earth complexes with 2,2′-biphenyldicarboxylic acid

Rare earth complexes with 2,2′-biphenyldicarboxylic acid (diphenic acid = H₂dpa) were obtained as hydrated precipitates of the general formula Ln₂(C₁₄H₈O₄)₃∙nH₂O, where n = 3 for the of Y(III) and Ce(III)–Er(III) and n = 6 for La(III), Tm(III), Yb(III) and Lu(III) complexes. On heating in air atmosphere complexes lose all water molecules in the temperature range 30–210 °C in one step and form anhydrous compounds, which are stable up to 315–370 °C. During further heating they decompose to oxides. The trihydrated compounds are crystalline powders whereas the hexahydrated are amorphous solids. The trihydrated complexes crystallize in the monoclinic (Pr(III) and Ce(III) complexes) and triclinic (Y(III) and Nd(III)–Er(III) complexes) crystal systems.     

Preconcentration of uranium(VI) on a chelating adsorbent followed by photometric determination with 2,3,4-trihydroxy-3′-nitro-4′-sulfoazobenzene

The complexation of uranium(VI) with 2,3,4-trihydroxy-3′-nitro-4′-sulfoazobenzene was studied. A complex was formed with the molar ratio of the components 1: 2, the maximum of light absorption at 435 nm, and the molar absorption coefficient 1.00 × 10⁴. A new adsorbent bearing carboxyl groups was synthesized. The batch adsorption capacity of the adsorbent with respect to K⁺ ions was found, and the ionization constants of the ionogenic groups were determined by potentiometric titration. An adsorption isotherm of uranium was measured and the optimal conditions for preconcentration were found. Under the optimal conditions, the recovery of U(VI) ions was more than 95%. The detection limit was 14.2 ng/mL (3σ, n = 20). A procedure was developed for the adsorption-photometric determination of uranium(VI) in water.     

Synthesis and thermal decomposition kinetics of two lanthanide complexes with cinnamic acid and 2,2′-Bipyridine

The two complexes of [Ln(CA)₃bipy]₂ (Ln = Tb and Dy; CA = cinnamate; bipy = 2,2′-bipyridine) were prepared and characterized by elemental analysis, infrared spectra, ultraviolet spectra, thermogravimetry and differential thermogravimetry techniques. The thermal decomposition behaviors of the two complexes under a static air atmosphere can be discussed by thermogravimetry and differential thermogravimetry and infrared spectra techniques. The non-isothermal kinetics was investigated by using a double equal-double steps method, the nonlinear integral isoconversional method and the Starink method. The mechanism functions of the first decomposition step of the two complexes were determined. The thermodynamic parameters (ΔH ^≠ , ΔG ^≠ and ΔS ^≠ ) and kinetic parameters (activation energy E and the pre-exponential factor A) of the two complexes were also calculated.     

Spectrophotometric determination of gold with phenyl-α-pyridyl ketoxime

A method is described for the spectrophotometric determination of gold in the concentration range of 2 to 16 p.p.m. using phenyl-α-pyridyl ketoxime as the reagent. The reagent permits to detect Iμ of gold in I ml of a solution. The method is particularly free from interference by the ions with which gold is frequently associated.     

Synthesis and characterization of complexes of the first transition series cations with 2,2′-biimidazole and 2,2′-biimidazolate

Mononuclear [M(hfacac)₂(H₂biim)] complexes, where M = Mn^II, Fe^II, Co^II, Ni^II, Cu^II or Zn^II, hfacac = hexafluoroacetylacetonate, H₂biim = 2,2-biimidazole; dinuclear K₂[M₂(acac)₄(-biim)] (M = Cu^II or Zn^II) and tetranuclear K₂[M₄(acac)₈( ₄-biim)] (M = Co^II or Ni^II) complexes have been prepared and characterized by chemical analysis, conductance measurements, i.r., electronic and e.p.r. spectroscopies and by magnetic susceptibility measurements (in the 2–300 K range). Mn^II, Fe^II and Co^II are in a high spin state. The e.p.r. spectra of Cu^II and Mn^II compounds have been recorded.     

Complexation of titanium(IV) with a new reagent, 2,3,4-trihydroxy-3′-nitro-4′-sulfoazobenzene

A new reagent, 2,3,4-trihydroxy-3′-nitro-4′-sulfoazobenzene (H ₃ L) is synthesized and studied. The dissociation constants of the reagent are determined by potentiometric titration: $ pK_{a_1 } $ = 4.52 ± 0.02; $ pK_{a_2 } $ = 6.29 ± 0.05, and $ pK_{a_3 } $ = 6.60 ± 0.21. The reaction of Ti(IV) with H₃L in the presence and absence of Triton X-114 (Tr) gives monoand mixed-ligand complexes, with λ_max = 445 nm and λ_max = 435 nm, respectively, at pH 4.5; the stability constants of the complexes Ti(OH)₂(H₂L)₂ and Ti(H₂L)₂(Tr) are logβ₁₂ = 8.51 ± 0.04 and logβ₁₂ = 10.72 ± 0.05, respectively. The mono(1: 2) and mixed-ligand (1: 2: 2) complexes obey the Beer law in the Ti(IV) concentration ranges 0.10–3.10 and 0.10–1.34 μg/mL, respectively. The effects of foreign ions and masking agents on the determination of Ti(IV) with the new reagent are studied. A procedure is developed for the photometric determination of Ti(IV) in soil samples selected at the Surakhany production field.     

Spectrophotometric Determination of Palladium (11) With 2,2′-pyridilmonoxime

Abstract

A visible spectrophotometric method is described for the determination of palladium with 2,2′-pyridilmonoxime. The effects due to pH, time, solvents, reagent concentration and diverse ions are reported. Reasonable structures for the reagent and palladium chelate based on analysis and infrared evidence are proposed.     

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 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.     

Synthesis and properties of 2,2′-dipyridyl and 4,4′-dipyridyl complexes with thulium salts

Summary New complexes of 2,2-dipyridyl and 4,4-dipyridyl with thulium salts TmX ₃ (whereX=Cl^–, Br^–, NO ₃ ^– , NCS^–, and ClO ₄ ^– ) have been prepared and their solubilities in water at 21 °C were determined. The IR spectra of these compounds are discussed. The conditions of thermal decomposition of the complexes were also studied.

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Synthese und Eigenschaften von 2,2-Dipyridyl- und 4,4-Dipyridylkomplexen mit Thuliumsalzen

Zusammenfassung Es wurden neue 2,2-Dipyridyl- und 4,4-Dipyridyl-Komplexen mit Thuliumsalzen TmX ₃ (X=Cl^–, Br^– No ₃ ^– , NCS^–, ClO ₄ ^– ) dargestellt und ihre Wasserlöslihkeit bei 21 °C bestimmt. Die IR-Spektren werden diskutiert. Das thermische Verhalten der erhaltenen Komplexe wurde untersucht.

     

Crystal structure of palladium(II) complex with 2,2′-dipyridylamine and 4-toluenesulfonyl-L-serine

The [Pd(dpa)(tsser)] complex (1) is prepared from the reaction of PdCl₂ and 2,2′-dipyridylamine (dpa) with 4-toluenesulfonyl-L-serine (tsserH₂). This complex is characterized by spectral methods (IR, UV-Vis, ¹H NMR, and luminescence), elemental analysis, thermal analysis (TG, DTA), and single crystal X-ray diffraction. X-ray structure determinations show that in this complex, Pd^II atoms are four-coordinated in a distorted square-planar configuration by two N atoms from a bidentate 2,2′-dipyridylamine ligand and one N atom and one O atom from a bidentate tsser^2– ligand.