Iron(II)-8-mercaptoquinoline,iron(II)-5-chloro-8-mercaptoquino-line and iron(II)-5-bromo-8-mercaptoquinoline complexing in the iron(III) hexacyanoferrate(II) gelatin-immobilized matrix systems

Novel complexing processes in the Fe^II-8-mercaptoquinoline, Fe^II-5-chloro-8-mercaptoquinoline and Fe^II-5-bromo-8-mercaptoquinoline systems, not used previously in coordination chemistry, namely complexing as an iron(III)hexacyanoferrate(II) gelatin-immobilized matrix (GIM) in contact with an aqueous solution of the corresponding ligand, have been observed and analysed. Incorporation of these ligands into the inner coordination sphere is preceded by the decomposition of the immobilized compound KFe[Fe(CN)₆] to form hydroxides or oxohydroxides of Fe^II and Fe^III under the action of OH^- ions. It has been shown that Fe^IIFeIII redox process and the formation of FeB₃ chelates (B^- is a singly deprotonated form of the corresponding ligand) take place during complexing under such conditions.     

Complexing of nickel(II) with 8-mercaptoquinoline and of its 5-derivatives in nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix systems

Complexing processes in systems containing NiII and 8-mercaptoquinoline or its derivatives (5-chloro-, 5-bromo-, 5-phenyl, 5-thiomethyl-8-mercaptoquinoline and 5,8-dimercaptoquinoline) take place in the nick- el(II)hexacyanoferrate(II) gelatin-immobilized matrix (GIM) in contact with an aqueous solution of the corresponding ligand. Under the conditions specified, in the NiII-8-mercaptoquinoline, NiII-5-chloro-8-mer captoquinoline,NiII-5-bromo-8-mercaptoquinoline, NiII-5-phenyl-8-mercaptoquinoline and NiII-5-thiomethyl-8-mercaptoquinoline systems, one water-insoluble complex of NiB2 composition (B– is a singly deprotonated ligand) is formed. In the NiII-5,8-dimercaptoquinoline system, two insoluble complexes, monomeric Ni(HB)2 and polymeric [Ni2B2(H2O)2]n (HB– is the singly, and B2– the doubly deprotonated form of the ligands) are generated. Upon complexing in solution or the solid phase, the formation of only one complex is observed in each of systems cited.     

Copper(II)–8-mercaptoquinoline,copper(II)–5,8-dimercaptoquinoline and copper(II)–5-thiomethyl-8-mercaptoquinoline complexing in a copper(II)hexacyanoferrate(II) gelatin-immobilized matrix

Novel complexing processes in the Cu^II–8-mercaptoquinoline, Cu^II–5,8-dimercaptoquinoline and Cu^II–5-thiomethyl-8-mercaptoquinoline systems proceeding in the copper(II)hexacyanoferrate(II) gelatin-immobilized matrix in contact with aqueous solutions of the ligands indicated, have been studied. Under the conditions specified for complexing in the Cu^II–8-mercaptoquinoline system, only a monomeric water-insoluble coordination compound was formed. In the Cu^II–5,8-dimercaptoquinoline system, three coordination compounds were formed and, in the Cu^II–5-thiomethyl-8-mercaptoquinoline system, two such compounds were formed. Conversely, complexing in solution or solid phase results in the formation only coordination compounds in each of the system studied.     

A study of 8-mercaptoquinoline (thiooxine) and its derivatives

The absorption spectra of 5-fluoro-8-mercaptoquinoline in aqueous solutions at various pH values have been studied. The _max values of the 5-fluoro-8-mercaptoquinolinium ion and also of the 5-fluoro-8-mercaptoquinolate ion, and the apparent molar absorption coefficient of the hydrated form have been determined. In the hydrated form, a molecule of water is connected by hydrogen bonds both with the nitrogen and with the mercapto group. The presence of the fluorine atom in positions 5 of the molecule of the 8-mercaptoquinoline increases the acidic properties of the mercapto group and decreases the basic properties of the nitrogen, in comparison with those in 8-mercaptoquinoline. The dissociation constants of 5-fluoro-8-mercaptoquinoline are pK_SH=7.49 ± 0.02 (thermodynamic) and pK_NH= 1.97 ±0.02 (concentration). The isoelectric point is at pH 4.70.For part XXXVIII, see [4].     

Cobalt(II)-8-mercaptoquinolines complexing in cobalt(II) hexacyanoferrate(II) gelatin-immobilized matrix materials

Complexing processes between Co^II and 8-mercaptoquinoline, or its various alkyl- and aryl-substituted derivatives, in contact with Co₂[Fe(CN)₆]-gelatin-immobilized matrix materials, with aqueous solutions of corresponding ligands, have been studied. When R² = Me or Ph, formation of Co^II chelates having a 1:2 metal ion/singly deprotonated ligand is observed, whereas when R² = H, formation of Co^III chelates having metal ion/singly deprotonated ligand 1:3 ratios occur.     

From novel complexing conditions to novel coordination compounds of nickel(II) with dithiooxamide and its bulky analogues

Summary Novel complexing processes in the Ni^II-dithiooxamide, Ni^II-N,N-diphenyldithiooxamide and Ni^II-quinoxaline-2,3-dithiol systems, which have not been used in coordination chemistry before, namely complexing in a nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix in contact with an aqueous solution of the corresponding ligand, have been studied. Under these specific conditions, in the Ni^II-dithiooxamide system, five different coordination compounds are formed, four of which are insoluble in H₂O. In the Ni^II-quinoxaline-2,3-dithiol system, three different complexes formed (each of them insoluble in H₂O) and, in the Ni^II-diphenyldithiooxamide system, only one insoluble complex is formed. Whereas, complexing in solution or the solid phase, formation of only one complex is observed in each of systems cited     

A comparative solvent extraction study of manganese(II) with 8-Mercaptoquinoline, 8-Quinolinol and its analogues

Equilibrium distribution coefficients were determined for the extraction of manganese(II) with 8-mercaptoquinoline, 8-quinolinol and its 2-methyl, 4-methyl, 5-chloro and 5-nitro analogues as a function of pH and reagent concentration at ambient temperature. 8-Mercaptoquinoline forms a mono self-adduct with Mn(II) whereas simple 12 chelate formation was observed in the case of 8-quinolines. The adduct formation constant and the overall formations constants in the aqueous phase have been determined. A linear relationship was observed between the equilibrium constants, formation constants and the pK values of the chelating agents.Synergic enhancement was observed in the extraction of Mn(II) with 8-mercaptoquinoline in presence of pyridine and its methyl derivatives and the adduct formation constants of the 12, chelate to nitrogen base, adducts were evaluated.     

Complex Formation of 1,5-Bis(amidomethylsulfonyl)pentane with Copper(II) and Iron(III)

The state of the new antitubercular agent 1,5-bis(amidomethylsulfonyl)pentane in aqueous micellar solution of the nonionic surfactant Bridge 35 and its complexing properties toward copper(II) and iron(III) ions have been studied by spectrophotometry, pH potentiometry (25°C, variable ionic strength), and mathematical modeling. In the concentration range from 5.00 × 10^–5 to 1.00 × 10^–3 M in the presence of Bridge 35, the title compound exists in a neutral monomeric form. It forms 1: 2 mononuclear and 2: 2 binuclear complexes with copper(II) and 1: 1 and 1: 2 mononuclear and 2: 1 binuclear complexes with iron(III). The most favorable structures of 1,5-bis(amidomethylsulfonyl)pentane and its complexes have been simulated in terms of the density functional theory.     

Electrochemical Behavior of Iron(III)/Iron(II) Couple in Dimethylformamide

The electrochemical behavior of the iron(III)/iron(II) couple was investigated in both complexing (Cl⁻) and noncomplexing (ClO⁻₄) media in dimethylformamide (DMF), and the results were compared with the results obtained in aqueous solutions. The diffusion coefficients for iron(III) and iron(II) in DMF are larger in complexing medium than in noncomplexing medium, contrary to the results obtained in aqueous solutions. The heterogeneous electron transfer rate constants for the iron(III)/iron(II) couple obtained in DMF were found to be smaller in DMF solution as a result of the specific adsorption of DMF. The formal potential of the Fe(III)/Fe(II) couple in DMF is about 0.2 V less positive in noncomplexing medium as a result of the greater stabilization of iron(III) by the strongly cation-solvating DMF. The formal potential of the same couple in complexing medium (Cl⁻) was found to be 0.5 V less positive due to a combination of solvation and complexation effects. Cyclic voltammetric investigations show a quasi-reversible electron transfer without any coupled chemical reaction.     

From novel complexing conditions to novel coordination compounds of copper(II) with dithiooxamide and its bulky analogues

Novel complexing processes in the CuII–dithiooxamide, CuIIN, N-diphenyldithiooxamide and CuII–quinoxaline-2,3-dithiol systems, which have been used in coordination chemistry before, namely complexing into a copper(II) hexacyanoferrate(II) gelatin-immobilized matrix in contact with an aqueous solution of the corresponding ligand, have been observed and analysed. Under these specific conditions, in each of the CuII–dithiooxamide and CuII–quinoxaline-2,3-dithiol systems, three different coordination compounds are formed, two of which are insoluble in water; in the CuII–diphenyldithiooxamide system, only one water-insoluble complex is formed. Conversely, complexing in solution or solid phase results in the formation of only one complex in each of the systems cited above. This revised version was published online in June 2006 with corrections to the Cover Date.     

Simultaneous determination of antimony(III) and antimony(V) by UV-vis spectroscopy and partial least squares method (PLS)

This paper describes a procedure for the speciation of antimony by UV-vis spectroscopy using pyrogallol as complexing agent. A partial least squares (PLS) regression was performed to resolve highly overlapping spectrophotometric signals obtained from mixtures of Sb(III) and Sb(V). The relative error in absolute value was less than 5% when concentrations of several mixtures were calculated. The minimum concentration determined was 3.96 × 10⁻⁵ mol dm⁻³ and 3.98 × 10⁻⁵ mol dm⁻³ for Sb(V) and Sb(III), respectively. The analysis of the possible effect of the presence of foreign ions in the solution was performed and the procedure was successfully applied to the speciation of antimony in pharmaceutical preparations and aqueous samples.     

Soft template synthesis of cobalt(III) chelates with 2,8-dithio-3, 7-diaza-5-oxa-nonandithioamide-1,9 and with 2,7-dithio-3,6-diazaoctadien-3, 5-dithioamide-1,8 into cobalt(III)hexacyanoferrate(II) gelatin-immobilized matrix materials

The complexing processes in the triple Co^III–dithiooxamide–methanal and Co^III–dithiooxamide–glyoxal systems taking place in the KCoFe(CN)₆-gelatin-immobilized matrix in contact with aqueous-alkaline solutions (pH~12) containing (dithiooxamide + methanal) and (dithiooxamide + glyoxal), have been studied. Template synthesis leading to macrocyclic Co^III coordination compounds with tetradentate N,N,S,S-donor ligands-(2,8-dithio-3,7-diaza-5-oxanonandithioamide-1,9) and (2,7-dithio-3,6-diazaoctadien-3,5-dithioamide-1,8) occurs under these specific conditions. Dithiooxamide, methanal and glyoxal are the ligand synthons in these processes.     

Simultaneous capillary electrophoretic determination of Sb(III) and Bi(III) based on the complex-formation with a W(VI)-P(V) reagent

A capillary electrophoretic method was developed for the simultaneous determination of Sb(III) and Bi(III). A 1.0 mM W(VI)-0.10 mM P(V) complexing reagent readily reacted with a mixture of trace amounts of Sb(III) and Bi(III) to form the corresponding ternary Keggin-type complexes; [P(Sb^IIIW₁₁)O₄₀]⁶⁻ and [P(Bi^IIIW₁₁)O₄₀]⁶⁻ in 0.01 M malonate buffer (pH 2.4). Since the peaks due to the migrations of the ternary complex anions were well separated in the electropherogram, the pre-column complex-formation reaction was applied to the simultaneous CE determination of Sb(III) and Bi(III) with direct UV detection at 255 nm. The calibration curves were linear in the range of 2×10⁻⁷-5×10⁻⁵ M; a detection limit of 1×10⁻⁷ M was achieved for Sb(III) or Bi(III) (the signal-to-noise ratio=3).     

A direct nitrogen-15 NMR study of praseodymium(III)-nitrate complex formation in aqueous solvent mixtures

A direct, low-temperature nitrogen-15(¹⁵N) NMR technique has been applied to the study of inner-shell complex formation between praseodymium(III) and nitrate ion in aqueous solvent mixtures. In water-acetone mixtures at –95°C, ligand exchange is slow enough to permit the observation of¹⁵N NMR signals for uncomplexed and coordinated nitrate ion, but satisfactory resolution is obtained only by the addition of Freon-12 to these systems for study at –110 to –115°C. Four coordinated nitrate signals are generally observed and a very small signal for an additional complex, or an isomer of one of the others, appears at the highest nitrate concentrations. Signals for the mono-and dinitrato complexes are unambiguously identified, but with the exception of the trinitrato complex, several possibilities exist for the remaining peaks. To overcome excessive viscosity signal broadening, measurements in methanol and ethanol are possible only with praseodymium trifluoromethanesulfonate (triflate). Coordinated nitrate signals in aqueous and anhydrous methanol are observed only for the mono-and dinitrato species, and signal areas indicate a maximum of two moles of nitrate per Pr(III) are complexed. A third signal is evident in the ethanol solution spectra, and the presence of this higher complex was confirmed by area measurement of the fraction of bound nitrate. The extent of complex formation in these solvent systems is attributed to differences in the dielectric constant. A comparison of the complexing tendencies of Pr(III) to other ions studied by this NMR method suggests the possibility of a coordination number change across the lanthanide series. Preliminary¹⁵N NMR results for metal-ion complexes with the isothiocyanate ion are presented.     

Dinuclear Fe(III) complexes with spin crossover

Abstract  A series of dinuclear Fe(III) complexes was synthesized in which the Schiff-base blocking ligand L⁵ coordinates each of the centers which are linked by a bidentate, bipyridine-type ligand. For these systems, [L⁵Fe^III{bridge}Fe^IIIL⁵](BPh₄)₂, thermally induced spin crossover is observed. The corollary of the systems is that the spin crossover interferes with the magnetic exchange interaction. The overlap of the energy bands of the LL and HH reference states (L, low-spin; H, high-spin) causes the exchange interaction to act against the spin crossover (leading to incompleteness or gradual behavior). Graphical abstract        

Complexing between copper(II) and bulky substituted 3-benzoyl thioureas in copper(II) hexacyanoferrate(II) gelatin-immobilized matrix systems

A novel route to complexes of CuII with various bulky substituted 3-benzoylthioureas: [(1-(2-hydroxy)phenyl-, 1-(4-hydroxy)phenyl-, 1,1-dibenzyl-, 1-methyl-1-phenyl-, 1-N-pentamethylene-] and 1-N-3-oxatetramethylene-3-benzoylthiourea, complexed to a CuII hexacyanoferrate- (II) gelatin-immobilized matrix in contact with aqueous alkali (pH 12.0) solutions of the ligands indicated, has been developed. Under the conditions specified, coordination of each ligand is preceded by decomposition of CuII-hexacyanoferrate(II) to give polymeric copper(II) hydroxide under the influence of OH– ions. With CuII-1-(4-hydroxy)phenyl-3-benzoylthiourea, three different water-insoluble coordination compounds are formed; in the other CuII-ligand systems, two types of complexes are formed, whereas complexing in solution or solid phase in these systems results, as a rule, in the formation of only one coordination compound. In systems such as CuII-1-naphthyl-3-benzoylthiourea, CuII-1-(4-hydroxy-3,5-di-t-butyl)benzyl-3-benzoylthiourea and CuII-1-(4-hydroxy-3,5-di-t-butyl) phenethyl-3-benzoylthiourea, complexing in CuII hexacyanoferrate(II) gelatin-immobilized matrices (GIM) is not observed.     

2,6-Bis(5-(2,2-dimethylpropyl)-1H-pyrazol-3-yl)pyridine as a ligand for efficient actinide(III)/lanthanide(III) separation

The N-donor complexing ligand 2,6-bis(5-(2,2-dimethylpropyl)-1H-pyrazol-3-yl)pyridine (C5-BPP) was synthesized and screened as an extracting agent selective for trivalent actinide cations over lanthanides. C5-BPP extracts Am(III) from up to 1 mol/L HNO(3) with a separation factor over Eu(III) of approximately 100. Due to its good performance as an extracting agent, the complexation of trivalent actinides and lanthanides with C5-BPP was studied. The solid-state compounds [Ln(C5-BPP)(NO(3))(3)(DMF)] (Ln = Sm(III), Eu(III)) were synthesized, fully characterized, and compared to the solution structure of the Am(III) 1:1 complex [Am(C5-BPP)(NO(3))(3)]. The high stability constant of log β(3) = 14.8 ± 0.4 determined for the Cm(III) 1:3 complex is in line with C5-BPP's high distribution ratios for Am(III) observed in extraction experiments.     

Novel coordination compounds of nickel(II) and copper(II) with N,Nprime-diphenylthiooxamide; formation of complexed metalhexacyanoferrate(II) gelatin-immobilized matrix systems

A novel route to complexes of NiII and CuII with N,Nprime-diphenylthiooxamide, namely complexing in a NiII or CuII hexacyanoferrate(II) gelatin-immobilized matrix in contact with an aqueous solution of the N,Nprime-diphenylthiooxamide, has been studied. Under these specific conditions, in the NiII system, four different coordination compounds are formed, three of which are insoluble in H2O; in the CuII system, only one insoluble complex is formed. When complexation is carried out in solution or the solid phase, formation of only one complex is observed in each of systems studied. This revised version was published online in June 2006 with corrections to the Cover Date.     

The formation of tris(2-methyl-8-hydroxyquinolinato)-aluminum(III)

The compound Al(C₁₀H₃ON)₃ can be precipitated from a 20 % ($\text{v}\text{v}$) acetone—water medium in the absence of auxiliary complexing agents. Precipitation from an initially acidic solution yields a product containing hydrolyzed forms of aluminum(III) but precipitation from an initially basic solution results in the pure tris compound. Under appropriate conditions, solid-phase aluminum hydroxide can be completely converted to Al(C₁₀H₃ON)₃. Stability constants for the formation of aluminum(III) complexes of 2-methyl-8-hydroxyquinoline are given.     

Polarographic studies of catalytic reduction of hydrogen in Cr(VI)−As(III) and Cr(III)—As(III) systems

In the presence of traces of Cr(VI) or Cr(III) ions in ammonia or borate buffers containing the As(III) ions a catalytic hydrogen wave arises in the dc polarogram. It was established that the complex Cr(H₂AsO₃)_n^+3?n is formed in the solution, and that its reduced form adsorbed at DME is of catalytic activity. The wave can be employed for the determination of low concentrations (2×10^?8×10^?7M) of Cr(VI) and Cr(III) ions.