Fluorescence quenching of anthropogenic fulvic acids by Cu(II), Fe(III) and UO(2)(2+)

The quenching of the fluorescence of three anthropogenic fulvic acids (FA) provoked by Cu(II) (pH 6.0), Fe(III) (pH 4.0) and UO₂²⁺ (pH 3.5), was analyzed by a non-linear method and by Stern-Volmer plots. The FA samples were extracted from composted sewage sludges (csFA), composted municipal wastes (mwFA) and composted livestock wastes (lsFA). Synchronous-scan fluorescence (SyF) spectra were collected as a function of metal ion concentration. Spectral data were treated by a self-modeling mixture analysis method (SIMPLISMA) to detect the SyF spectral band with the strongest quenching and to calculate the corresponding quenching profile. The analysis of these profiles by a non-linear method allowed the estimation of conditional stability constants (K) and of the percentage of non-complexing fluorophores. The same quantitative information was obtained by the modified Stern-Volmer equation taking into account the existence of fluorophores that do not participate in the complexation. Good agreement was found between the results of the two procedures. The log K calculated by the non-linear method were (standard deviation in parenthesis): csFA, Cu(II), 4.22 (5); Fe(III), 5.0 (1); UO₂²⁺, 5.2 (2); mwFA, Cu(II), 4.21 (3); Fe(III), 5.6 (2); UO₂²⁺, 4.7 (3); lsFA, Cu(II), 4.51 (8); Fe(III), 5.5 (2); UO₂²⁺, 3.6 (2).     

Dioxouranium(VI) complexes of 3-benzamidorhodanine and its substituted derivatives

The synthesis and characterization of some dioxoyranyl(VI) complexes containing-3-benzamidorhodanine and its substituted derivatives as ligands are reported. The structure of complexes is discussed on the basis of spectral (UV, IR and NMR), elemental analyses, conductivities, molecular weights and thermal analysis (DSC, DTA, TGA and TG) results. IR spectra show that the ligands are bidentate coordinating via the amide nitrogen (NH) and the carbonyl oxygen of rhodanine in the enol form with displacement of a proton from the latter group. Also, NMR studies suggest that the enolization and coordination occurs via the carbonyl oxygen of rhodanine and not through the carbonyl of the amide moiety. Finally, the thermal studies suggest the existence of a cis-form for the isolated uranyl complexes.     

Stability constants of phthalate complexes of copper (II), nickel (II), zinc (II), cobalt (II), uranyl (II) and throium (IV) by paper electrophoresis

Summary Stoichiometric stability constants of Cu(II), Ni(II), Zn(II), Co(II), UO₂(II) and Th(VI) phthalate have been determined by paper electrophoresis. Phthalic acid (0.005 mol dm⁻³) was added to the background electrolyte: 0.1 mol dm⁻³ HClO₄. The proportions of C₆H₅C₂O ₄ ⁻ and C₆H₄C₂O ₄ ⁼ were varied by changing the pH of the electrolyte. These anions yielded the complexes, Cu C₆H₅C₂O ₄ ⁺ , Cu C₆H₄C₂O₄, Zn C₆H₅C₂O ₄ ⁺ , Co C₆H₅C₂O ₄ ⁺ , Ni C₆H₅C₂O ₄ ⁺ , UO₂ C₆H₅C₂O ₄ ⁺ , UO₂ (C₆H₄C₂O₄) ₂ ⁼ and Th (C₆H₄C₂O₄)₂ whose stability constants are found to be 10^3.0, 10^4.7, 10^2.6, 10^2.5, 10^2.3, 10^3.5, 10^12.6 and 10^13.4 respectively (μ=0.1, temp 40°C).     

Formation of ferrocyanides-IV Th(IV), Nd(III), UO(2)(II) and Hg(II)

The stoichiometry of the reaction between ferrocyanide and thorium, neodymium, uranyl ion and mercury(II) has been investigated. The first three give single products irrespective of the order of addition of the reagents, but the last does not. If mercury(II) is added to ferrocyanide Hg(2)Fe(CN)(6) is obtained, but if ferrocyanide is added to mercury(II) various cyanide complexes of mercury are formed. The K(sp) values for the precipitates are reported.     

Determination of UO2(II), Th(IV) and Ce(III) Complexes Formed with Halogen and Nitro Derivatives of 8-Hydroxyquinoline

Proton-ligand stability constants for some iodo and nitro derivatives of 8-hydroxyquinoline were determined by Calvin Bjerrum potantiometric method. The stability constants of the corresponding chelates with UO₂ (II), Th(IV) and Co(III) were studied potentiometrically at 25 °C by applying Irving-Rossotti computing method. The complexes of the nitro-substituted ligands were less stable than the corresponding complexes of the unsubstituted ligands. The stability constants of metal-ligands depend on the ionic radii and ionic charge of metals and also they decrease with steric repulsions of the nitro groups.     

Heterobinuclear and Heterotrinuclear complexes of Oxorhenium(V) with Cu(II), Ni(II), Fe(III), UO2(VI) and Th(IV) in the solid state

New heteronuclear complexes containing oxorhenium(V), Cu(II), Ni(II), Fe(III), UO₂(VI) and Th(IV) ions were prepared by the reaction of the complex ligand, [ReO(H₄L)Cl]Cl₂, where H₄L = 8,17-dimethyl-6,15-dioxo-5,7,14,16-tetrahydrodibenzo[a,h][14]annulene-2,11-dicarboxylic acid, with the previous transition and actinide salts. Three heteronuclear Cu(II) complexes were isolated depending on the ratio of [ReO(H₄L)Cl]Cl₂?:?Cu(II) ion. When the ratios were 1?:?0.5, 1?:?1 and 1?:?2, the heteronuclear complexes {[ReO(H₃L)Cl]₂CuCl₂(OH₂)₂}SO₄ · H₂O (I), [ReO(H₃L)Cl₂Cu(OH₂)₂(SO₄)] (II) and {ReO(H₂L)Cl[Cu(OH₂)₃ SO₄]₂} (III) were obtained, respectively. Heteronuclear complexes of the other metal cations were obtained by mixing [ReO(H₄L)Cl]Cl₂ with the metal salt in the ratio 1?:?1 to obtain the heteronuclear complexes [ReO(H₃L)Cl₂Ni(OH₂)₂](NO₃)₂ (IV), [ReO(H₃L)Cl₃Fe(OH₂)₃](NO₃)₂ (V), [ReO(H₃L)ClUO₂(NO₃)₂ (OH₂)]Cl (VI) and [ReO(H₃L)Cl₃Th(NO₃)₂(OH₂)]NO₃ · 2H₂O (VII). The complex ligand coordinates with the heterometal ion via the carboxylate group, and the infrared bands ν_as COO and ν_s COO indicate that the carboxylate acts as a unidentate ligand to the heterometal cations. Cu(II) and Fe(III) cations in the heteronuclear complexes have octahedral geometry, while Ni(II) is square planar. Thermal studies explored the possibility of obtaining new heteronuclear complexes pyrolytically in the solid state from the corresponding mother complexes. The structures of the complexes were elucidated by conductance, IR and electronic spectra, magnetic moments, ¹H NMR and TG-DSC measurements as well as by mass spectroscopy.     

Spectrophotometric Study of Mithramycin Complexes with Cu(II), Fe(III) and Tb(III)

Abstract

The coordination of the anticancer drug mithramycin to Tb(III), Fe(III) and Cu(II) was studied in aqueous solution using absorption measurements. The stability constants were calculated from equilibrium competition experiments by means of the SQUAD program. For both first ions, the competitor was oxalic acid and for the latter the competitor was the Cu(II) ions. Cu(II) at pH 7.5, Fe(III) at pH 3.5 and Tb(III) at pH 5.5 formed respectively 1:2, 1:3 and 1:4 metal-to-ligand species.     

Rh(III), Pd(II), Pt(IV) and Au(III) complexes of 2-thiopyrimidine derivatives

Some news thiopyrimidine derivatives and complexes [4-amino-5-nitroso-6-oxo-1,2,3,6-tetrahydro-2-thio-pyrimidine (TANH), its 2-methylthio derivative (MTH), the ammonium salt ofTANH (sTANH) and six new complexes of formulas: Rh(MT)₂Cl · 2H₂O, Pd(MTH)₂Cl₂, Pt(MTH)₂Cl₄, Au(MTH)Cl₃ Pd(TANH)₂Cl₂ and Au(TAN ^–)Cl] have been synthesized and characterized by elemental analysis, IR and¹H-NMR spectroscopy techniques. The thermal behaviour of all compounds has also been studied.

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Rh(III), Pd(II), Pt(IV) und Au(III) Komplexe von 2-Thiopyrimidin Derivaten

Zusammenfassung Es wurden einige neue Thiopyrimidinderivate und deren Komplexe synthetisiert und mittels Elementaranalyse, IR und¹H-NMR charakterisiert: 4-Amino-5-nitroso-6-oxo-1,2,3,6-tetrahydro-2-thio-pyrimidin (TANH), dessen 2-Methylthio-Derivat (MTH), das Ammoniumsalz vonTANH (sTANH) und sechs neue Komplexe der Formeln Rh(MT)₂Cl · 2H₂O, Pd(MTH)₂Cl₂, Pt(MTH)₂Cl₄, Au(MTH)Cl₃, Pd(TANH)₂Cl₂ und Au(TAN ^–)Cl. Das thermische Verhalten der Verbindungen wurde ebenfalls untersucht.

     

Assignment of complex species by affinity capillary electrophoresis: The case of Th(IV)-desferrioxamine B

The electrophoretic mobility change of desferrioxamine B (DFO) was monitored by UV absorption spectrophotometry upon increasing the thorium(IV) concentration in the background electrolyte at two acidities ([HClO₄]_Tot = 0.0316 and 0.0100 M). These data enabled to assess the speciation model and to determine the equilibrium constant of [Th(DFO)H₂]³⁺ at fixed ionic strength (I = 0.1 M (H,Na)ClO₄). Affinity capillary electrophoresis (ACE) turned out to be most helpful in identifying the complexed species by ascertaining its charge and protonation state. The assignment of the correct stoichiometry relied on the reliable estimation of the electrophoretic mobility by assuming similar hydrodynamic radii for (DFO)H₄⁺ and the chelate. The value of the apparent equilibrium constant (log β₁₁₂ = 38.7 ± 0.4) obtained by ACE compares favorably well with those reported in the literature for thorium and a range of other metal ions, according to a linear free-energy relationship. This method is useful for studying metal-ligand binding equilibria and provides valuable information for further modelling the behavior of tetravalent actinides under environmental conditions. Structural information about the prevalent solution species in acidic conditions was gained by DFT calculations, confirming the bishydroxamato coordination mode of Th⁴⁺ by the diprotonated ligand.     

Co(II), Ce(III) and UO2VI) bis-salicylatothiosemicarbazide complexes: binary and ternary complexes, thermal studies and antimicrobial activity

A series of new metal complexes of Co(II), Ce(III) and UO(2)(VI), with the Schiff base ligand, H2L, bis-salicylatothiosemicarbazide have been prepared in presence of different molar ratios of LiOH.H2O as a deprotonating agent. Also, the ternary complexes were prepared by using 2-aminopyridine (2-Ampy) or oxalic acid (Ox) as a secondary ligand. All synthesized compounds were identified and confirmed by elemental analyses, molar conductivities, spectral (UV-Vis, IR, 1H NMR, mass) and magnetic moment measurements as well as TG-DSC technique. The changes in the selected vibrational absorption bands in IR and NMR spectra of the Schiff base ligand upon coordination indicate that, the ligand behaves as a neutral, monoanionic and/or dianionic tetradentate manner with ONNO donor sites. Conductance measurements suggest the non-electrolytic and 1:1 electrolytic nature of the metal complexes. Thermal studies suggest a mechanism for degradation of the metal complexes as function of temperature supporting the chelation modes, moreover, show the possibility of obtaining new complexes pyrolytically in the solid state which cannot be synthesized from solution. Antimicrobial screening of the free ligand and its binary complexes showed that, the free ligand and some metal complexes possess antimicrobial activities towards four type of bacteria and five types of fungi and these results were compared with eleven type of known antibiotics.     

Interaction of uranyl with Se(IV) and Se(VI) in aqueous acid solutions by means of capillary electrophoresis

The uranyl–selenium(IV) and uranyl–selenium(VI) interactions were studied by CE in aqueous acid solutions, containing U(VI) and Se(IV) or Se(VI) at different concentrations, at pH 1.5, 2.0 and 2.5. The method proposed in this paper allows one with the use of CE data on metal ion mobilities at different pHs to establish the ligand species interacting with metal ion and complex species formed. In the case of Se(VI) a selenate, as demonstrated, interacts with uranyl ions, in the case of Se(IV) this is a hydroselenite. It was also shown that the equilibria for the U(VI)–Se(VI) and U(VI)–Se(IV) systems can be established from CE data. The formation of UO₂SeO₄, UO₂(SeO₄), UO₂HSeO and UO₂(HSeO₃)₂ species is demonstrated. The stability constant values were measured at different ionic strengths (from 0.02 to 0.2 mol/L). The logarithms of the stability constant values (β°) extrapolated to ionic strength 0 by the specific ion interaction theory (SIT) are found to be log β°₁=2.93±0.06 for UO₂SeO₄ formation, log β°₂=4.030.18 for UO₂(SeO₄) formation, log β°₁=3.270.15 for UO₂HSeO formation and log β°₂=5.510.11 for UO₂(HSeO₃)₂ at 25°C. The results for the first constant values for each of systems are consistent with the published values. For UO₂(SeO₄) formation, a new constant stability value is given. The existence of UO₂(HSeO₃)₂ complex species is demonstrated and its constant stability value is given for the first time.     

Synthesis and characterization of UO2(II) and Th(IV) binuclear complexes with o-vanillylidene anthranilic acid

Two new solid binuclear complexes of the compositions [(UO₂)₂(HL)₃]NO₃, and [Th₂(HL)₃(NO₃)₂](NO₃)₃ (H₂L=o-vanillylidene anthranilic acid) have been synthesized and characterized by elemental analyses, DTA-TG, IR spectra, UV spectra and molar conductance. Possible structures of the two complexes have been proposed.     

Stability constants of thorium(IV) complexes with aryl-bis-(5-hydroxy-3-methyl-1-phenyl-4-pyrazolyl) methane ligands

Summary Stability constants of complexes of aryl-bis-(5-hydroxy-3-methyl-1-phenyl-4-pyrazolyl) methane [ArBPyM] derivatives with thorium(IV) ions were determined by the potentiometric method at 30°C and an ionic strength of 0.1 mol·dm^–3 (KNO₃) in 75% (v/v) dioxane-water. The evaluation of the titration data indicated that four kinds of complexes ([ThL]²⁺, [ThLOH]⁺, [ThL ₂], and [ThL(OH)₂]^2–) were formed. The formation constants for all [ThL]²⁺ and [ThL ₂] complexes have been calculated to compare these values with those previously reported [1, 2] with Ln³⁺ and UO ₂ ²⁺ metal ions [2, 3]. The probable ligand-bonding sites of the complexes are proposed. In addition, the applicability of theHammett equation for the correlation of the stability constants of [Th(IV)-ArBPyM] complexes are discussed.

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Stabilitätskonstanten von Thorium(IV)-Komplexen mit Aryl-bis-(5-hydroxy-3-methyl-1-phenyl-4-pyrazolyl)-methan-Liganden

Zusammenfassung Stabilitätskonstanten von Komplexen von Aryl-bis-(5-hydroxy-3-methyl-1-phenyl-4-pyrazolyl)-methan — Derivaten [ArBPyM] mit Thorium(IV) — Ionen wurden bei 30°C und einer Ionenstärke von 0.1 mol-dm^–3 (KNO₃) in 75% (v/v) Dioxan-Wasser potentiometrisch bestimmt. Die Auswertung der Titrationskurven zeigte, daß vier verschiedene Komplexe vorlagen ([ThL]²⁺, [ThLOH]⁺, [ThL ₂] und [ThL(OH)₂]²⁺). Die Bildungskonstanten aller [ThL]²⁺- und [ThL ₂]-Komplexe wurden berechnet, um sie mit den früher für Ln³⁺- und UO ₂ ²⁺ -Ionen publizierten zu vergleichen. Potentielle Bindungsstellen der Komplexe für Liganden werden vorgeschlagen. Zusätzlich wird die Anwendbarkeit derHammet-Beziehung auf die Korrelation der Stabilitätskonstanten von [Th(IV)-ArBPyM] — Komplexen diskutiert.

     

Palladium(II) complexes of oligopeptides containing aspartyl and glutamyl residues

Potentiometric and ¹H NMR spectroscopic measurements have been performed on palladium(II) complexes of di-, tri- and tetra-peptides containing aspartyl and glutamyl residues including AspAla, AlaAsp, AspAsp, AspAspAsp, GluGluGlu, GlyAspGly, AspAspAspAsp and GlyGlyAspGly. In the case of dipeptides the coordination modes are basically determined by the peptide backbone. The presence of the extra β-carboxylate residues does not result in new binding modes but these functions may slightly affect the thermodynamic stability of several species. For tripeptides the most important findings are connected to the governing role of the β-carboxylate group of internal aspartyl residues but similar effects were not observed for the peptides containing glutamic acid. Aspartic acid in the second position of a tripeptide (Xaa-Asp-Yaa sequence) promotes the binding of the preceding and prevents deprotonation and coordination of subsequent amide functions. In the case of tetrapeptides, the aspartyl residues present in the third position from the N-terminus (Xaa-Yaa-Asp-Zaa sequence) have the most pronounced effect on complex formation. In this case, the (NH₂, N⁻, N⁻, β-COO⁻)-coordination is the major binding mode and the species [PdH₋₂L] can exist in a wide pH range. The enhanced stability of these complexes was explained by the conformational changes of the coordinated ligands.     

Iron(III), cobalt(II,III), copper(II) and zinc(II) complexes of 2-pyridineformamide 3-piperidylthiosemicarbazone

Reduction of 2-cyanopyridine by sodium in the presence of 3-piperidylthiosemicarbazide produces 2-pyridineformamide 3-piperidylthiosemicarbazone, HAmpip. Complexes with iron(III), cobalt(II,III) copper(II) and zinc(II) have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. In addition, the crystal structures of HAmpip, [Fe(Ampip)₂]ClO₄, [Cu(HAmpip)Cl₂]·CH₃OH and [Zn(HAmpip)Br₂]·C₂H₆SO have been determined. Coordination is via the pyridyl nitrogen, imine nitrogen and thiolato or thione sulfur when coordinating as the anionic or neutral ligand, respectively.     

A study of polyamine complex formation with H+, Cu(II), Zn(II), Pb(II), and Mg(II) in aqueous solution

Summary The composition and stability of the following biogenic amine complexes have been investigated: 1,4-diaminobutane(Put), 4-azaoctane-1,8-diamine(Spd), 4,9-diazadodecan-1, 12-diamine(Spm) as well as homologues such as 1,3-diaminopropane(Put3), 4-azaheptane-1, 7-diamine(Spd3,3) and 4,8-diazaundecan-1,11-diamine(Spm3,3,3) with H⁺, Cu(II), Zn(II), Pb(II) and Mg(II). A potentiometric method was used. The VIS technique enabled the determination of coordination mode in copper/amine systems. It was found that Mg(II) does not form coordination compounds with any of the studied polyamines in solution. An increase in the concentration of ligand and metal was found to result in a stronger tendency towards the formation of protonated compounds accompanied by a decrease in the concentration of hydroxocomplexes. At physiologicalpH (7.4) an increase in the concentration of protonated compounds by approximately 15% was observed within the ligand concentration range from 0.001 mol dm^–3 to 0.0001 mol dm^–3 at a Cu(II) concentration of 0.000177 mol dm^–3.

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Untersuchungen zur Komplexbildung von Polyaminen mit H⁺, Cu(II), Zn(II), Pb(II) und Mg(II) in wäßriger Lösung

Zusammenfassung Anhand einer Analyse von potentiometrischen Daten wurden Zusammensetzung und Beständigkeit folgender biogener Aminkomplexe untersucht: 1,4-Diaminobutan(Put), 4-Azaoktan-1,8-diamin(Spd), 4,9-Diazadodekan-1,12-diamin(Spm), sowie auch deren Homologen 1,3-Diaminopropan(Put3), 4-Azaheptan-1,7-diamin(Spd3,3) und 4,8-Diazaundekan-1,11-diamin(Spm3,3,3) mit H⁺, Cu(II), Zn(II), Pb(II) und Mg(II). Mit Hilfe der VIS-Technik wurde die Koordinationsweise in Kupfer/Amin-Systemen bestimmt. Es wurde festgestellt, daß Mg(II) keine Koordinationsverbindungen mit den untersuchten Polyaminen bildet. Eine höhere Konzentration von Ligand und Metall führte zu stärkerer Tendenz der Bildung protonierter Verbindungen, wobei die Konzentration von Hydroxokomplexen kleiner wurde. Bei physiologischempH (7.4) wurde im Bereich der Ligand-Konzentration von 0.001 mol dm^–3 bis 0.0001 mol dm^–3 bei einer Cu(II)-Konzentration von 0.000177 mol dm^–3 ein Anstieg der Konzentration protonierter Verbindungen um etwa 15% beobachtet.

     

Acetohydroxamatoiron(III) Complexes: Thermodynamics of Formation and Temperature Dependent Speciation

Studies of the thermodynamics of formation of the acetohydroxamatoiron(III) complexes were carried out in acidic media at temperatures ranging from 293 to 323 K. Through the isolation of the unique UV–visible spectra of all three complexes, it was possible to determine their formation constants and deduce enthalpies and entropies of formation as well as their molar absorptivities. The enthalpies of formation of the mono-, bis- and trisacetohydroxamatoiron(III) complexes were found to be −56.4, −17.09 and +19.74 kJ⋅mol⁻¹, respectively. Following the determination of the enthalpy and entropy of formation of these complexes, speciation diagrams were calculated for the complexes at temperatures ranging from 293 to 323 K.     

Coordination of Y(III), Ce(III), La(III) and Zr(IV) with Some Salicylidene Aromatic Schiff Bases

Coordination compounds formed by the interaction of some salicylidene aromatic Schiff bases with Y(III), Ce(III), La(III), and Zr(IV) are prepared and characterized by elemental analysis, electronic and i.r. spectra as well as conductometric methods. The i.r. spectra indicate that coordination takes place through the azomethine nitrogen atoms and OH groups. The structure of such products depend mainly on the type of Schiff base used. Also, the formation constant of the complexes are evaluated.