Mixed-ligand cyanide cobalt(III) complexes with 1,2-cyclohexanediaminetetraacetic acid: Synthesis and photochemical properties

[Co(CN)₂(H₃Cdta)] · 2H₂O (I) and Na₂[Co(CN)(Cdta)] · 3H₂O (II) (Cdta⁴⁻ is the 1,2-cyclohexanediaminetetraacetate) were synthesized. In I, the two cyanide ions and the Cdta nitrogen atoms are located in the equatorial plane, the carboxyl groups connected to different N atoms are in axial positions; in addition one of them, like two other uncoordinated carboxyl groups, is protonated. In II, Cdta is a pentadentate ligand coordinated in the cis-equatorial mode. UV excitation of the dicyano complexes at the ligand-to-metal charge transfer band gives organic derivatives of cobalt(III) stable enough for chromatographic isolation. Photolysis of II in neutral medium gives aqua(cyclohexanediaminetriacetato)cobalt (III) complexes as the final products.     

Inclusion complexes of Fe(III) tetrakis(4-sulfonatophenyl)porphyrin with cyclodextrins in aqueous solutions

In aqueous solutions, inclusion complexation of Fe(III) tetrakis(4-sulfonatophenyl)porphyrin (FeTSPP) with alpha-cyclodextrin (alpha-CD), beta-CD, gamma-CD, and heptakis(2,3,6-tri-O-methyl)-beta-CD (TM-beta-CD) has been examined by means of absorption and induced circular dichroism spectroscopy. FeTSPP has been found to form inclusion complexes with beta-CD, gamma-CD, and TM-beta-CD in pH 3.2 buffers. At pH 10.1, where FeTSPP self-associates to form an oxo-bridged dimer, FeTSPP also forms inclusion complexes with alpha-CD, beta-CD, gamma-CD, and TM-beta-CD. The stoichiometries of the CD-FeTSPP inclusion complexes are 1:1, except for TM-beta-CD in pH 10.1 buffers where its 1:1 inclusion complex associates with TM-beta-CD to form a 2:1 inclusion complex at high TM-beta-CD concentrations. Equilibrium constants of FeTSPP for the formation of the 1:1 inclusion complexes have been evaluated for beta-CD, gamma-CD, and TM-beta-CD. Induced circular dichroism spectra of FeTSPP in alpha-CD and beta-CD solutions exhibit a signal pattern (a negative sign) that is different from those in acidic and basic solutions containing gamma-CD and that in basic solution containing TM-beta-CD, suggesting different inclusion modes towards FeTSPP.     

Fe(III)-pyruvate and Fe(III)-citrate induced photodegradation of glyphosate in aqueous solutions

The photolysis of Fe(III)-pyruvate and Fe(III)-citrate complexes in water produces hydroxyl radicals in the presence of dissolved oxygen, and can promote the oxidation of organic compounds. The photodegradation of glyphosate with Fe(III)-pyruvate and Fe(III)-citrate complexes was investigated under irradiation at λ?≥?365?nm. The effect of initial concentration of glyphosate, the initial pH value, and the Fe(III)/carboxylate ratio were examined. Upon irradiation of glyphosate aqueous solution with the complexes in the acidic range of natural waters, the bioavailable orthophosphate could be released from degradation of glyphosate. The amount of orthophosphate increased with increasing Fe(III)/carboxylate ratio.     

Gold(III) amine complexes in aqueous alkali solutions

The gold(III) 1,3-diaminopropane complex [Au(1,3-pn)(1,3-pn-H)]Cl₂ has been synthesized. Its dissociation constant has been determined: Au(1,3-pn)₂³⁺ = Au(1,3-pn-H)²⁺ + H⁺, logK _a1 = −7.03 ± 0.05 (I = 0.1 mol/L NaClO₄). Considerable spectral changes are observed for strong alkali solutions (pH 11–14) containing the monoamido forms of the gold(III) ethylenediamine, 1,3-diaminopropane, and diethylenetriamine complexes (Au(en)(en-H)²⁺, Au(1,3-pn)(1,3-pn-H)²⁺, Au(dien-H)OH⁺). These changes are attributed to the formation of the diamido species Au(en-H)₂⁺, Au(1,3-pn-H)₂⁺, and Au(dien-2H)OH⁰. The dissociation constants of the monoamido complexes have been determined: Au(en)(en-H)²⁺ (logK _a2 = −10.9 ± 0.1 at I = 0.001–0.01 mol/L NaCl); Au(1,3-pn)(1,3-pn-H)²⁺ (logK _a2 = −11.3 ± 0.1 at I = 0.1 mol/L NaCl); Au(dien-H)OH⁺ (logK _a2 = −12.4 ± 0.1 at I = 0.1 mol/L NaCl).     

Ion-pair interactions of lanthanide(III) complexes in aqueous solutions

The formation of ion-pair adducts between the cationic complex La(THP)3+ (THP = 1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane) and the anionic complexes Tm(DOTA)- (DOTA = 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetate), Tm(DTPA)2- (DTPA = diethylenetriamine-N,N,N',N",N"-pentaacetate), Tm(TTHA)3- (TTHA = triethylenetetraamine-N,N,N',N",N"',N"'-hexaacetate), and Tm(DOTP)5- (DOTP = 1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetrakis(methylenephosphonate)) is examined by 13C NMR spectroscopy. The induced 13C shifts of the La(THP)3+ complex are followed by titration of the Tm(III) complexes of DOTA, DTPA, and TTHA at pH 7. From these data, the stability constants are calculated to be beta 1 = 64 M-1 (1:1), beta 1 = 296 M-1 (1:1), and beta 2 = 26,000 M-2 (2:1) for the ion pairs of La(THP)3+, with Tm(DOTA)-, Tm(DTPA)2-, and Tm(TTHA)3-, respectively. The La(THP)3+,Tm(DOTP)5- system elicits chiral resolution of the rapidly interconverting Tm(DOTP)5- isomers.     

Kinetics of formation of Fe(III) complexes in aqueous DMSO

Spectrophotometric observations have been used to study equilibria and temperature jump relaxation associated with formation of Fe(III) complexes in aqueous DMSO in the presence of SCN⁻. The [SCN⁻] dependent relaxation observed at 315 nm could be assigned to the formation of Fe DMSO³⁺, Fe DMSO OH²⁺, Fe DMSO SCN²⁺ and Fe DMSO SCN OH⁺ from Fe²⁺ and Fe OH²⁺. The relaxation observed at 450 nm could be assigned to the formation of Fe SCN²⁺ by paths similar to that in aqueous solutions and a pH dependent path in which the rate determining step is the displacement of DMSO from Fe DMSO SCN OH⁺ by H₂O. The rate constants suggest that coordination by a DMSO instead of a H₂O has the effect of labilising the other H₂O coordinated to Fe OH²⁺. The observed decrease in relaxation rates with increase in [DMSO] have been explained as dominantly due to the reduction in the acid dissociation constant K_H associated with the aquocomplex of Fe(III).     

Redox reactions of V(III) and Cr(III)picolinate complexes in aqueous solutions

Reactions of e_aq⁻, H-atoms, OH, (CH₃)₂COH, and CO₂⁻ radicals with V(III)picolinate and Cr(III)picolinate have been studied by the pulse radiolysis technique. The spectra of V(II)picolinate, V(IV)picolinate, Cr(II)picolinate, OH adduct of Cr(III)picolinate and Cr(IV)picolinate have been obtained and the rate constants of the reactions of various radicals with V(III) and Cr(III)picolinate have been determined. The implications of these results to the chemical decontamination of nuclear reactor systems are discussed.     

Solubility of gallium(III) oxyhydroxide in aqueous NaCl solutions at 100°C

The hydrolysis-precipitation equilibrium reaction of aqueous gallium(III) solution was investigated in 0–3 mol-kg^-1 NaCl media at low pH at 100°C using a pressure-tight glass vessel. All precipitates were identified as GaOOH. The results were analyzed with a nonlinear least-squares computer program to obtain the solubility product K_so for gallium(III) oxyhydroxide using a single-parameter type of Debye-Hückel equation. The value of log K_so for GaOOH(s) + 3H⁺ ⇆ Ga³⁺ + 2H₂O was -0.60 at 100°C. The solubility product calculated from thermodynamic data was compared with the experimental result.     

Fluorescence of lanthanide(III) complexes with aminopolyacetic acids in aqueous solutions

The fluorescence of Eu(III), Gd(III), Tb(III) and Dy(III) ions complexed with aminopolyacetic acids was investigated. The influence of temperature and the dimensions of the ligand molecules and of their electric charge on the intensity of the emission bands is discussed as well as the ratio of the hypersensitive (forbidden) band to the allowed band intensity. On the basis of the fluorescence measurements a simple theoretical model is discussed and certain generalizations concerning the fluorescence of the lanthanides group are derived.

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Fluoreszenz von Lanthaniden(III)-Komplexen mit Aminopolyessigsäuren in wäßrigen Lösungen

Zusammenfassung Die Fluoreszenz von mit Aminopolyessigsäuren komplexierten Eu(III), Gd(III), Tb(III) und Dy(III) Ionen wurde untersucht. Der Einfluß von Temperatur und Größe der Ligandenmoleküle und von deren elektrischer Ladung auf die Intensität der Emissionsbanden wird diskutiert, ebenso das Verhältnis der Intensitäten der hyperempfindlichen und erlaubten Banden. Auf der Basis von Fluoreszenzmessungen wird ein einfaches theoretisches Modell diskutiert und Verallgemeinerungen betreffend der Fluoreszenz der Lanthanidengruppe getroffen.

     

Formation of bismuth(III) N-methylthiourea complexes in aqueous solutions

The formation constants of bismuth(III) methylthiourea complexes in aqueous solution were determined at 298 K and an acidity of 2 M HClO₄ using the “ligand-oxidized ligand species” potentiometric method and the methylthiourea (mtu)-symmetric dimethylformamidine disulfide (mFDS) redox pair. The formation function was obtained, and the conditional (β _n ^*) and true (β _n ) formation constants of Bi(mtu) _n ³⁺ (1 ≤ n ≤ 8) were calculated. The value of β₁ and the formation of complexes with coordination numbers higher than six was confirmed by spectrophotometry.     

Influence ofpH and concentration of complexing agents on fluorescence of europium (III) ethylenediaminetetraacetic acid and europium (III) nitrilotriacetic acid complexes in aqueous solutions

The fluorescence of aqueous solutions of Eu(III) complexes withEDTA andNTA has been investigated. Intensities of the fluorescence bands have been measured as a function of complexone concentrations in the solutions and thepH. The results are interpreted in terms of the different forms of Eu(III) complexes and their relative stabilities.

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Einfluß vonpH und Konzentration der Komplexbildner auf die Fluoreszenz der Komplexe des Europium (III) mit Ethylendiamintetraessigsäure und Nitrilotriessigsäure in wäßrigen Lösungen

Zusammenfassung Die Fluoreszenz von wäßrigen Lösungen der Komplexe des Europium(III) mit Ethylendiamintetraessigsäure und Nitrilotriessigsäure wurde untersucht. Die Intensitäten der Fluoreszenzbanden in Abhängigkeit vonpH und Konzentration der Komplexbildner wurden auf der Basis vorkommender Komplexgeometrien und deren Stabilitäten interpretiert.

     

Multinuclear NMR study of lanthanide(III) complexes of 1,2-PDTA in aqueous solution

The complexation of lanthanide(III) cations with 1,2-propanediaminetetraacetate (1,2-PDTA) in aqueous solution has been investigated by ¹⁰Na, ³⁵Cl, ²H and ¹¹O NMR shift measurements. It has been shown that the contact shifts are dominant for ¹⁷O, ¹⁶Cl and ²H (only for the heavier lanthanide series) and the pseudocontact shifts are dominant for ²⁵Na. It is suggested that the 1,2-PDTA ligand is bound pentadentately via the two nitrogens and the three carboxylates for the lighter lanthanide complexes, hexdentately via the two nitrogens and the four carboxylates for the heavier ones. The numbers of the water coordinated were determined. The small amount of chloride anion in inner coordination sphere was observed.     

Photochemistry of Fe(III) complex with glyoxalic acid in aqueous solution

Nanosecond laser flash photolysis technique was used to study photochemistry of Fe(III) complex with glioxalic acid. The primary photochemical process was found to be inner-sphere electron transfer in the excited complex leading to formation of the long-lived radical complex [Fe^II … ^·OOC-C(O)H]²⁺. A number of important spectral-kinetic parameters of this species were determined and mechanism of photolysis of Fe(III)-glioxalate complex was proposed. 1 The article was translated by the authors.     

Photochemistry of the iron(III) complex with pyruvic acid in aqueous solutions

Photochemistry of the 1: 1 Fe^pIII complex with pyruvic acid (PyrH) in aqueous solutions was studied by stationary photolysis and nanosecond laser flash photolysis with the excitation by the 3rd harmonics of an Nd:YAG laser. The quantum yield of [FeIIIPyr]2+ under the excitation at 355 nm is 1.0±0.1 and 0.46±0.05 in the absence and in the presence of dissolved oxygen, respectively. In experiments on laser flash photolysis, a weak intermediate absorption in the region 580–720 nm was found. The absorption was ascribed to the [FeII…MeC(O)COO•]^p2+ radical complex. Laser flash photolysis of [FePyr]^p2+ in the presence of methyl viologen dications (MV^p2+) resulted in the formation of the MV•+ radical cations. The proposed reaction mechanism includes the inner-sphere electron transfer in the light-excited complex accompanied by the formation of the [Fe^pII…MeC(O)COO•]^p2+ radical complex followed by its transformation into the reaction products.     

Investigation of complexes tannic acid and myricetin with Fe(III)

The pH dependence of the complexes was determined by both potentiometric and spectrophotometric studies. Stability constants and stoichiometries of the formed complexes were determined using slope ratio method. Fe(III) was formed complexes with tannic acid of various stoichiometries, which in the 1:1 molar ratio at pH<3, in the 2:1 molar ratio at pH 3-7 and in the 4:1 molar ratio at pH>7. Fe(III) was formed complexes with myricetin in the 1:2 molar ratio at pH 4 and 5 and in the 1:1 molar ratio at pH 6. Stability constant values were found to be 10(5) to 10(17) and 10(5) to 10(9) for Fe(III)-tannic acid complexes and Fe(III)-myricetin complexes. Both tannic acid and myricetin were possessed minimum affinities to Cu(II) and Zn(II). They had less affinity for Al(III) than for Fe(III).     

Fluorescence of lanthanide(III) complexes in aqueous solutions the influence ofpH and solution composition

The fluorescence of lanthanide ions and of their complexes withEDTA,NTA andAA in aqueous solutions was investigated. It has been shown that the fluorescence band intensities of Sm(III), Eu(III), Gd(III), Tb(III) and Dy(III) complexes depend on thepH and the complexing agent concentration. Fluorescence measurements were used to characterise the lanthanide complexes formed and an attempt was made to interpret the results theoretically.

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Untersuchung der Fluoreszenz von Lösungen einiger Lanthaniden(III)-Komplex in Abhängigkeit vonpH und Zusammenhang der Lösung

Zusammenfassung Die Fluoreszenz von wäßrigen Lösungen der Ionen und Komplexe einiger Lanthaniden mit Ethylendiamintetraessigsäure, Nitrilotriessigsäure und Essigsäure wurde untersucht. Der Einfluß vonpH und Konzentration der Komplexbildner auf die Intensität der Fluoreszenzbanden von Sm(III), Eu(III), Gd(III), Tb(III) und Dy(III) wurde bewiesen. Die Fluoreszenzmessungen wurden für die Charakterisierung von Lösungen der Lanthanidenkomplexe genützt und ein Versuch der theoretischen Interpretation der beobachteten Änderungen im Spektrum wurde unternommen.