Extraction and complex formation of iron(III) thiocyanates with monooctyl anilinobenzylphosphonate

The extraction of iron (III) from aqueous hydrochloric acid solutions containing an excess of thiocyanate ions with monooctyl anilinobenzylphosphonate (MOABP) dissolved in chloroform or petroleum ether, was studied by radiometric and spectrophotometric methods. Iron forms mixed thiocyanate-MOABP complexes that are soluble in organic solvents. The composition of the iron complexes was studied by Job's method and radiometrically. In addition, several iron complexes were isolated from the organic phase and analyzed. The following complexes have been identified: Fe(SCN)R₂·HR, Fe(SCN)R₂, Fe(SCN)₂R·3HR and Fe(SCN)₂R·HR (HR = MOABP).     

Comparison of yttrium,lanthanides and actinides in respect to unit cell volumes of isostructural compounds and thermodynamic functions of complex formation

The investigations carried out till now and presented in this paper show that apart from the well known itinerant properties of yttrium in respect to free energy of complex formation, also actinides(III) change their position in the lanthanide series in respect to G. It has also been shown that yttrium and actinides exhibit itinerant behaviour in respect to unit cell volumes. Evidence has been presented that delocalization of 4f and 5f orbitals is the reason for the two types of migratory properties. Since the itinerant behaviour of yttrium and actinides(III) in respect to stability constants (free energies of complex formation) is the basis for yttrium-lanthanides and lanthanides-actinides group separations, a better qualitative understanding of the mechanism involved may contribute to the development of more efficient separation procedures.     

Excess thermodynamic functions and complex formation in binary liquid mixtures containing acetonitrile

Nagata, I. and Kawamura, Y., 1979. Excess thermodynamic functions and complex formation in binary liquid mixtures containing acetonitrile. Fluid Phase Equilibria, 3: 1–11.Molar excess enthalpy and isothermal vapor-liquid equilibrium data of acetonitrile-chloroform have been obtained at 298.15 and 328.15 K, respectively. Excess thermodynamic functions for the former system and for acetonitrile-carbon tetrachloride have been discussed in terms of a thermodynamic association theory for complex binary liquid mixtures containing self-associating species and a binary complex.     

The enthalpy of formation of IrO2 and thermodynamic functions

The Gibbs energy of formation of IrO₂(s) has been measured by means of oxygen dissociation pressure measurements, and by EMF measurements using ZrO₂ (+ CaO) as the solid electrolyte. In addition, high-temperature enthalpy increments of IrO₂ have ben measured from 416 to 940 K using a drop calorimeter. A “third law” evaluation of the experimental results and data from literature has been made. For the enthalpy of formation of IrO₂(s) the value ΔH°_f (298.15 K) - −(59.60 ± 0.03) kcal mole⁻¹ has been selected. The thermodynamic functions of IrO₂(s) have been calculated in the temperature range 298–1200 K.     

Effects of large halides on the structures of lanthanide(III) and plutonium(III) borates

Reactions of LnBr(3) or LnOI with molten boric acid result in formation of Ln[B(5)O(8)(OH)(H(2)O)(2)Br] (Ln = La-Pr), Nd(4)[B(18)O(25)(OH)(13)Br(3)], or Ln[B(5)O(8)(OH)(H(2)O)(2)I] (Ln = La-Nd). Reaction of PuOI with molten boric acid yields Pu[B(7)O(11)(OH)(H(2)O)(2)I]. The Ln(III) and Pu(III) centers in these compounds are found as nine-coordinate hula-hoop or 10-coordinate capped triangular cupola geometries where there are six approximately coplanar oxygen donors provided by triangular holes in the polyborate sheets. The borate sheets are connected into three-dimensional networks by additional BO(3) triangles and/or BO(4) tetrahedra that are roughly perpendicular to the layers. The room-temperature absorption spectrum of single crystals of Pu[B(7)O(11)(OH)(H(2)O)(2)I] shows characteristic f-f transitions for Pu(III) that are essentially indistinguishable from Pu(III) in other compounds with alternative ligands and different coordination environments.     

Structural, thermodynamic, and mesomorphic consequences of replacing nitrates with trifluoroacetate counteranions in ternary lanthanide complexes with hexacatenar tridentate ligands

The promesogenic hexacatenar tridentate ligands L3(Cn) (I shape) and L4(Cn) (V shape) react with trivalent lanthanide trifluoroacetates, Ln((CF3CO2)3, to give either monometallic [Ln(Li(Cn))(CF3CO2)3] or trifluoroacetato-bridged bimetallic [Ln(Li(Cn))(CF3CO2)3]2 complexes in the solid state, as exemplified by the crystal structures of [Lu(L4(CO))(CF3CO2)3(H2O)], [Lu(L4(CO))(CF3CO2)3]2, and [La(L3(C4))(CF3CO2)3]2. Although the dimerization process is influenced by the competiting complexation of anions or solvent molecules, the coordination of CF3CO2- instead of NO3- to Ln(III) produces a significant lengthening of the Ln-N(ligand) bond distances. This translates into a considerable decrease of the affinity of the Li(C12) (i = 3, 4) ligands for Ln(CF3CO2)3 in solution, thus leading to significant dissociation of the [Ln(Li(C12))(CF3CO2)3] complexes at millimolar concentrations. The thermal properties of these complexes also suffer from their limited thermodynamic stability, and the thermotropic liquid crystalline phases produced at high temperatures reflect mixtures of different species. However, a hexagonal columnar organization characterizes the main component in the mesophases obtained with [Ln(L3(C12))(CF3CO2)3] at high temperature. A tentative interpretation of the small-angle X-ray scattering (SAXS) profiles suggests that disklike dimers of [Ln(L3(C12))(CF3CO2)3]2 are packed along the columnar axes. For [Ln(L4(C12))(CF3CO2)3], SAXS profiles are compatible with a lamellar organization in the mesophases originating from the existence of rodlike dimers of [Ln(L4(C12))(CF3CO2)3]2 as the major component in the liquid-crystal state.     

Standard thermodynamic functions of complex formation between Cu2+ and glycine in aqueous solution

Heat effects of the interaction of copper(II) solutions with aminoacetic acid (glycine) are measured by the direct calorimetry at 298.15 K and ionic strengths of 0.5, 1.0, and 1.5 against a background of potassium nitrate. Standard enthalpy values for reactions of the formation of aminoacetic acid copper complexes in aqueous solutions are obtained using an equation with a single individual parameter by extrapolating it to zero ionic strength. The standard thermodynamic characteristics of complex formation in the Cu²⁺-glycine system are calculated. It is shown that glycine-like coordination is most likely in Cu(II) complexes with L-asparagine, L-glutamine, and L-valine.     

The position of yttrium within lanthanides with respect to unit cell volumes of isostructural compounds as an indication of covalency in lanthanide compounds

The position of yttrium in the lanthanide series with respect to unit cell volumes has been determined from literature data for 52 isostructuralM_mX_n compounds of lanthanides and yttrium. A linear correlation between the position and the electronegativity of theX atom has been demonstrated. This result has been explained in terms of covalent shortening of theMX bonds in lanthanide compounds.     

Evaluation of thermodynamic functions relative to cavity formation in aqueous solutions

The results of calculation of free Gibbs energy and enthalpy of cavity formation were described using the Scaled Particle and Sinanoglu's theories.

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Zusammenfassung Mittels der zitierten Theorien wurden die Resultate der Berechnung der freien Gibbs'schen Energien und Enthalpien für die Hohlraumbildung beschrieben.

     

Spatial structure and thermodynamic aspects of Dy(III) complex formation with some mono- and dicarboxylic acids

Spatial structures of complexes [DyAc]²⁺, [DyBz]²⁺, [DyAc₂]⁺ and [DyBz₂]⁺ in aqueous solutions (Ac^– and Bz^–, acetate and benzoate anions, respectively) are studied using the paramagnetic double refraction method. The polyhedra of [DyAc(H₂O)₆]²⁺ and [DyBz(H₂O)₆]²⁺ are dodecahedra with ligands coordinated at one of the edges. In the complexes [DyAc₂(H₂O)₄]⁺ and [DyBz₂(H₂O)₄]⁺ the ligands are coordinated at the edges of a square antiprism at an angle of 50 (55)° to the local symmetry axis of higher symmetry.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1038–1040, June, 1993.     

Mechanisms of sensitization of lanthanide(III)-based luminescence in transition metal/lanthanide and anthracene/lanthanide dyads

Four sets of dyads are discussed, in all of which near-infrared emitting lanthanide(III) ions such as Nd(III), Er(III) or Yb(III) are energy-acceptors which provide sensitized luminescence following energy-transfer from an antenna group. In three sets of dyads the antenna (energy-donor) group is a luminescent transition metal fragment; in the fourth the antenna is an anthracene group. A combination of photophysical studies and calculations has been used to understand the mechanisms by which energy-transfer to the lanthanide(III) ion occurs. Although definitive answers are not possible in every case due to the presence of several possible energy-transfer pathways, the relative contributions of Förster-type, Dexter-type and redox-mediated energy-transfer pathways have been analysed. Interesting results include (i) the demonstration of pure Dexter energy-transfer over 20 Å in a Ru(II)/Nd(III) dyad, and (ii) the demonstration of a redox-based mechanism for energy-transfer in anthracene/Ln(III) dyads in which the first step is photoinduced electron-transfer from the excited anthracene chromophore to a diimine ligand on the lanthanide(III) to generate a charge-separated state.     

The thermodynamic characteristics of step complex formation in the (5,10,15,20-tetraphenylporphyrinato)(chloro)indium(III)-pyridine-toluene system

The thermodynamic characteristics, step mechanism, and spectral manifestations of step reactions between (5,10,15,20-tetraphenylporphyrinato)(chloro)indium(III) ((Cl)InTPP) and organic base pyridine (Py) in inert toluene were studied using spectrophotometric titration and physicochemical analysis of intermediate forms. The coordination of Py molecule (K ₁ = 9.45 × 10² l/mol at 298 K) with the formation of (Cl)(Py)InTPP, the substitution of Cl^? in (Cl)(Py)InTPP with the second Py molecule (K ₂ = 2.3 × 10² l/mol), and the coordination of the third Py molecule to produce [(Py)₃ InTPP]⁺ · Cl^? (K ₃ = 8.7 l/mol) were observed at the first, second, and third steps, respectively. The fourth reaction stage most likely corresponds to π?π complex formation equilibrium between the aromatic complex and pyridine with a 1: 2 stoichiometry. The thermodynamic parameters of step reactions ΔH ^° and ΔS ^° well correspond to the stoichiometric mechanism of the reaction. Prospects for the use of the metalloporphyrin as a receptor of organic N-bases are considered.     

The position of americium within lanthanides in respect to unit cell volumes of isostructural compounds. A comparison of covalency in lanthanide and actinide compounds

The position of americium within lanthanides in respect to unit cell volumes has been determined for 25 isostructural M_mX_n compounds. A linear correlation between the position of americium and the electronegativity of X atom has been demonstrated. This result has been explained in terms of greater covalent shortening of Am-X than of Ln-X bonds.     

The thermodynamic characteristics of complex formation between calcium ions and L-leucine in aqueous solution

Complex formation of L-leucine with calcium ions in aqueous solution was studied by potentiometric titration at 298.15 K and ionic strength values I = 0.5, 1.0, and 1.5 (KNO₃). The formation of the CaL⁺ and CaHL²⁺ complex particles was established and their stability constants were determined. The enthalpies of protolytic equilibria of leucine and formation of calcium ion complexes with leucine were determined calorimetrically at 298.15 K and I = 0.5 (KNO₃). The thermodynamic characteristics of complex formation between calcium ions and L-leucine were calculated.     

Investigation of the complex formation of plutonium(VI) with 2-thenoyltrifluoroacetone by solvent extraction

The co-ordination of plutonyl ions with 2-thenoyltrifluoroacetone (HTTA) has been investigated by distribution studies of²³⁹Pu between benzene and aqueous perchlorate medium at 25°C in order to understand the nature of the extracted species and their stability. The formation constants of the first and second complexes have been evaluated by Rydberg's graphical method as well as by least squares analysis of the distribution data using a computer programme. The overall formation constant (β₂) for Pu(VI)-HTTA system has been found to be of the order of 10¹².     

Synthesis and characterization of the complexes of lanthanide(III) chlorides and nitrates with the tetradentate schiff base diethyl(ethylenebis-β-aminocrotonate)

Summary The Schiff base ligand diethyl(ethylenebis--aminocrotonate) (LH₂) reacts with lanthanide(III) chlorides and nitrates in various solvents to give solid complexes of the stoichiometriesLn(LH₂)Cl₃ (Ln=La–Yb),Ln(LH₂)₂Cl₃ (Ln=La–Sm),Ln ₂(LH₂)₃Cl₆(Ln=Eu–Yb) andLn(LH₂)(NO₃)₃ (Ln=La–Yb). Properties, conductivity measurements, X-ray powder patterns, thermal data, magnetic moments and spectroscopic (IR,¹H-NMR, electronic diffuse reflectance and solid state emission f-f spectra) are discussed in terms of the nature of the bonding and the possible structural types.

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Synthese und Charakterisierung der Komplexe von Lanthanid(III)chloriden und -nitraten mit der vierzähnigen Schiff-Base Diethyl(ethylenbis--aminocrotonat)

Zusammenfassung Der Schiffbasen-Ligand Diethyl(ethylenbis--aminocrotonat) reagiert mit Lanthanid(III)chloriden und -nitraten in verschiedenen Lösungsmitteln unter der Bildung von festen Komplexen der StöchiometrienLn(LH₂)Cl₃ (Ln = La – Yb),Ln(LH₂)₂Cl₃ (Ln = La – Sm),Ln(LH₂)₃Cl₆ (Ln = Eu – Yb) undLn(LH₂)(NO₃)₃ (Ln = La – Yb). Die allgemeinen Eigenschaften, Leitfähigkeitsmessungen, Röntgen-Pulverdiagramme, thermische Daten, magnetische Momente und spektroskopische Daten (IR,¹H-NMR, Elektronenreflexionsspektren und Festkörperemissions-f-f-Spektren) werden im Hinblick auf die Bildungsverhältnisse im Komplex und strukturelle Möglichkeiten diskutiert.