NMR STUDY OF LANTHANIDE(III) NITRATE-CMPO EXTRACTION SYSTEM (I) STRUCTURE OF EXTRACTEDCHEMICAL SPECIES

ABSTRACT

Octyl(phenyl)-N,N-dtisobutylcarbamoylmethylphosphine oxide used in the TRUEX process is a new extractant for TRU elements. NMR measurements were carried out to study the coordination structure of lanthanide(III)-CMPO complexes. By analyzing Lan- thanide-Induced-Shifts(LIS) data It was found that CMPO molecule locates in the equatorial region with respect to the principal magnetic Z axis. From the NMR longitudinal relaxation time measurements for Ce(N0₃)₃· 3CMPO, the distance of Ce³⁺-P, Ce³⁺- C(bridging methylene carbon) and Ce³⁺-C(carbonyl carbon) were estimated to be 3.3, 3.1 and 3.1 Å, respectively, suggesting that CMPO coordinates to the central Ce³⁺ ion in a bidentate manner with the phosphoryl and carbonyl groups. This is consistent with the low frequency shifts of phosphoryl and carbonyl stretching frequencies observed in the IR spectrum of Ce(N0₃)₃·3CMPO. Moreover, from the dependence of ³¹P-NMR spectra for Nd(N0₃)₃·3CMPO and Er(N0₃)₃·2CMPO on temperature, lanthanide(IH) -CMPO complexes exist as several isomers in CDC1₃ and a rapid intramolecular interconversion occurs at higher temperature region.     

THERMODYNAMICS OF EXTRACTION OF Am(III) AND Eu(III) FROM NITRATE AND THIOCYANATE MEDIA WITH OCTYL(PHENYL)-N,N-DIISOBUTYLCARBAMOYLMETHYLPHOSPHINE OXIDE

ABSTRACT

The extraction of Am(III) and Eu(III) from 1.0 M NH₄NO₃ and NHS₄SCN at pH 2.60 into octyl(pheriyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in n-dodecane has been studied in the temperature range 15.0 to 45.0°C. Under all conditions, the species ML₃·CMPO is the dominant extracted complex. The extraction equilibrium constants are at least 10₃ higher in the SCN^- systems than in the NO₃ ^- systems. This difference is attributed to the relative energy associated with transfer of the anions from the aqueous to the: extractant phase. Extraction enthalpies and entropies have been calculated in each system from the temperature dependence of K_ex. Enthalpies are considerably more exothermic in the thiocyanate system for both metal ions. Comparison of ΔH_Am ^SCN with ΔH_EU ^SCN gives a possible indication of enhanced Am-SCN bond strength in the extracted complex.     

EFFECT OF ANIONS ON THERMODYNAMICS OF EXTRACTION OF Am(III) AND Eu(III) WITH OCTYL(PHENYL)-N,N-DIISOBUTYL-CARBAMOYLMETHYLPHOSPHINE OXIDE

The extraction of Am(III) and Eu(III) by octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in xylene from aqueous media containing 1.0 M NH₄NO₃, NH₄SCN, NH₄ClO₄ or a mixture of 0.3 M NH₄NO₃ + 0.7 M NH₄ClO₄ at pH 2.70 and at the temperatures of 15, 25, 35 and 45±0.1 °C has been studied. At all the temperatures, the species extracted were ML₃ · 3CMPO (M = Am(III) or Eu(III), L = NO₃ ^?, SCN^? or ClO₄ ^?) and M(NO₃)(ClO₄)₂ · 3CMPO. The thermodynamic parameters of the extraction reactions have been evaluated using the temperature coefficient method. The ?ΔG values follow the order SCN^? > NO₃ ^? + ClO₄ ^? > NO₃ ^? ≈ ClO₄ ^?, whereas the ?ΔH values an order NO₃ ^? + ClO₄ ^? > SCN^? > NO₃ ^? ≈ ClO₄ ^?. The effect of these anions on the thermodynamic parameters have been discussed employing compensation effects and also on the basis of the energy associated with the transfer of these anions from aqueous to the extractant phase.     

Thermodynamic and Spectroscopic Studies on Am(III) and Eu(III) in the Extraction System of N,N,N',N'-Tetraoctyl-3-Oxapentane-1,5-Diamide in n-Dodecane/Nitric Acid

Abstract

Thermodynamic parameters (ΔG, ΔH, and ΔS) for the extraction of trivalent f-elements, M(III) (M = Am, Eu), with N,N,N',N'-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) were determined in nitric acid/n-dodecane extraction system. The extraction of M(III) with TODGA was more exothermic than those with octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) and dihexyl-N,N-diethylcarbamoylmethyl phosphonate (DHDECMP). The difference in ΔH between the extractants was attributed to the difference in the binding mode between them, i.e. tridentate (TODGA) and bidentate (CMPO and DHDECMP). In addition, from the results of luminescence lifetime measurement, it was found that the inner-sphere of extracted Eu(III) was dehydrated completely, and occupied by TODGA and/or NO₃ ^?.     

SYNERGISTIC EXTRACTION OF Eu(III) AND Am(III) BY THENOYLTRIFLUOROACETONE AND NEUTRAL DONOR EXTRACTANTS: (CARBAMOYLMETHYL)PHOSPHINE OXIDE AND 2,6-BIS((DIPHENYLPHOSPHINO)METHYL)PYRIDINE N,P, P-TRIOXIDE

ABSTRACT

Solvent extraction of Eu(III) and Am(III) from weakly acidic solutions with octyl(phenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and 2,6-bis((diphenylphosphino)methyl)pyridine N, P, P-trioxide (NOPOPO) in 1,2-dichloroethane was studied on a comparative basis. NOPOPO was found to exhibit unusually high extractability for Eu(III) and Am(III), probably due to its trifunctional nature, sufficient steric flexibility and basicity of the functional groups. Both CMPO and NOPOPO demonstrated synergistic effects in extraction of Eu(III) and Am(III) when used in combination with thenoyltrifluoroacetone (HTTA). However, the stoichiometry of the extracted species with CMPO/HTTA and NOPOPO/HTTA was different under similar experimental conditions. The extractant dependencies of the synergistic extractions suggest that the extracted species are the adduct complexes, M(ClO₄)(TTA)₂(CMPO)₂ and M(ClO₄)₂(TTA)(NOPOPO)₂, respectively. It was also observed that CMPO and CMPO/HTTA in dichloroethane extracted Eu(III) and Am(III) equally well, with very similar extraction constants. However, NOPOPO and NOPOPO/HTTA in dichloroethane demonstrated a slight preference for Eu(III) over Am(III), with the extraction constants for Eu(III) more than one order of magnitude higher than that for Am(III).     

SYNERGISTIC EXTRACTION STUDIES OF Am(III) AND Eu(III) FROM PERCHLORIC ACID WITH 4-BENZOYL-2,4-DIHYDRO-5-METHYL-2-PHENYL-3H- PYRAZOL-3-THIONE (BMPPT) AND TRI-n-OCTYLPHOSPHINE OXIDE (TOPO) IN BENZENE

The extraction of Am(III) and Eu(III) from aqueous HCIO₄ by BMPPT and TOPO in benzene was studied. The ligand BMPPT gave no detectable extraction in the ranges studied, but when BMPPT and TOPO were combined, a synergistic extraction was observed with a selectivity for Ara(III) over Eu(III) (K_dAm = 7.5, Am/Eu = 68, pH 3.0, 0.01 M [TOPO], 0.30 M [BMPPT]). The slope of the acid dependency for Eu and Am was 1.6 ± 0.1 and 2.7 ± 0.1, respectively, over the pH range of 2 to 3.The slope of the BMPPT dependency was 2.7 ± 0.1 and 2.8 ± 0.1 over a 2- and 20-fold concentration range for Eu and Am, respectively; the slope of the TOPO dependency was 2.0 ± 0.1 and 2.2 ± 0.1 for Am and Eu, respectively, over a 20-fold concentration range.     

Synergistic Extraction Studies Using n-Octyl(Phenyl) N,N-Diisobutylcarbamoyl-Methylphosphine Oxide

Abstract

The effectiveness of n-octyl(phenyl)-N,N′-diisobutylcarbamoyl-methylphosphine oxide, CMPO, as a neutral extractant for the trivalent actinides and lanthanides from strong acid media has been well established. This investigation characterized the use of CMPO as a synergistic agent in the extraction of Am(III) and Eu(III) by thenoyltrifluoroacetone (HTTA). The distributions of the metal ions were measured using radiotracer techniques as functions of HTTA concentration, CMPO concentration and pH. The results show that the presence of CMPO enhances the extraction of Eu(III) and Am(III) by 10⁸. The synergistic adduct was M(TTA)₃·CMPO with no indication of higher complexes being formed. Unlike previous studies, the extraction of Eu(III) was more strongly enhanced than that of Am(III). The results showed little, if any, enhancement in the extraction efficiency due to the bidentate nature of the CMPO.     

Synthesis,Characterization and Fluorescence Properties of Poly(styrene-co-n-caprylamide maleic acid) and Its Europium(III) and Terbium(III) Complexes

Copolymer of poly(styrene-co-n-caprylamide maleic acid) (PSCMA, defined as HL) and its lanthanide complexes Ln(L)₃·6H₂O (Ln = Eu and Tb) had been synthesized and characterized by elemental analysis, X-ray diffraction, Fourier transform infrared spectra, UV-spectrophotometer and thermal analysis (TG–DTA). The fluorescence properties of the HL ligand and the Ln(L)₃·6H₂O complexes in the solid state were investigated. At room temperature, the HL ligand had a strong broad emission band at 410–575 nm (λmax = 458 nm) under excitation at 380 nm, while the respective characteristic emission of Eu(III) and Tb(III) ions was observed in Ln(L)₃·6H₂O complexes. This demonstrated that the HL ligand in the extra-framework channels succeeded in sensitizing Eu(III) and Tb(III) ions emission. Compared with the Eu(L)₃·6H₂O complex, the fluorescence intensity of the Tb(L)₃·6H₂O complex was much stronger. This indicated that the lowest excited triplet state energy level of HL matched well with the excited state energy level of Tb(III). With the increase of the Ln(III) ions content below 15 wt%, the fluorescence intensity increased monotonically. All the Ln(L)₃·6H₂O complexes exhibited high quantum yield, long fluorescence lifetime and good thermal stability.     

The first example of half-sandwich cobalt(III) complex with hydrotris(pyrazolyl)borate ligand

This paper presents the synthesis, crystal structure and spectroscopic properties of a novel half-sandwich mononuclear cobalt(III) complex with hydrotris(3,5-dimethylpyrazolyl)borate ligand and thiocyanate [Tp^*Co(Hpz^*)(NCS)₂]·H₂O·CH₃OH (Tp^*: hydrotris(3,5-dimethyl- pyrazolyl)borate, Hpz^*: 3,5-dimethylpyrazole). The structure was determined by X-ray diffraction. The complex crystallizes in the monoclinic system, space group C_c, a=18.591(6) Å, b=10.536(3) Å, c=17.568(5) Å, β=11.284(5)°, Z=4, R₁=0.0501, wR₂=0.1179. The cobalt(III) ion in the complex is six-coordinated with nitrogen atoms, three from Tp^*, two from pyrazole and two from two thiocyanates, to form octahedral environment. The hydrogen atoms of O(2) of water molecule are connected by hydrogen bonds with S atoms of two adjacent complex molecules to form 1-D chains. The hydrogen atom of N(8) of complex molecule is connected by hydrogen bond with methanol. The spectroscopic results are consistent with the crystallographic study.     

Monometallic and bimetallic europium(III) and terbium(III) complexes: Synthesis and luminescent properties

Eight new lanthanide complexes of the form Ln(L)₃bipy and [Ln(L)₃]₂bpm were synthesized (where L = 2,2,6,6-tetramethyl-3,5-heptanedione (tmh) and 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione (tdh), bipy = 2,2′-bipyridine, bpm = 2,2′-bipyrimidine and Ln = Tb(III) or Eu(III)). The luminescent spectra are typical of Tb(III) and Eu(III) complexes with intense transitions at 545 nm for Tb(III) and 612 nm for the Eu(III) complexes. Energy gaps between the tmh 1 orbitals and the ⁰D_J manifold of Eu(III) are too large to give efficient energy transfer therefore emission spectra for Eu(tmh)₃bipy and [Eu(tmh)₃]₂bpm were not detected. Lifetimes are greatest for the Tb(III) complexes containing tmh terminal ligands while the longest lifetimes for the Eu(III) complexes occur with the tdh terminal ligands.     

Lanthanide(III) 1,4-Phenylenediacetate Complexes: The Relation Between the Structure and Thermal Properties

The series of isostructural lanthanide coordination polymers with the empirical formula [Ln₂(PDA)₃(H₂O)]·2H₂O, where PDA = 1,4-phenylenediacetate anion = [C₈H₈(COO)₂]^2?; Ln = La-Lu(III), and Y(III) were produced in the reaction of LnCl₃·nH₂O with ammonium salt of 1,4-phenylenediacetic acid in water solution. The compounds were characterised structurally using powder X-ray diffraction, elemental and thermogravimetric analyses as well as FT-IR spectroscopy. Thermogravimetric analyses show that in the range 60–170 °C the dehydration process occurs. The thermal stability of dehydrated compounds, Ln₂(PDA)₃ increased from about 200–350 °C in the whole series of complexes. Single-crystal X-ray diffraction analysis for the Gd(III) complex revealed that the compound crystallizes in the monoclinic P2₁/c space group with a = 21.863(2) Å, b = 10.035(1) Å, c = 13.854(1) Å, β = 91.53(1)° and V = 3,038.5(4) ų. The complex contains one-dimensional gadolinium-carboxylato chains, which are connected with the –CH₂–C₆H₄–CH₂– spacers of PDA ligand to the three-dimensional metal–organic framework.     

THE EXTRACTION OF Am(III) FROM NITRIC ACID BY OCTYL(PHENYL)-N,N-DIISOBUTYLCARBAMOYLMETHYLPHOSPHINE OXIDE - TRI-n-BUTYL PHOSPHATE MIXTURES

Abstract

The extraction behavior of Am(III) from nitric acid by octy1(phenyl)-N,N-diisobutylcarbamoyl methyphosphine oxides, OØD[IB]CMPO, in the presence of tributylphosphate, TBP, has been studied using diethylbenzene, decalin, and normal aliphatic hydrocarbon diluents. Relative to ØD[IB]CMPO alone, mixtures of TBP and OØD[IB]CMPO show a slight enhancement in the extraction of Am(III) from nitric acid solution above 2 M and a moderate decrease in extraction for lower acid concentrations. The net effect of TBP addition to OØD[IB]CMPO (as well as other selected carbamoyl methylphosphoryl extractants) is a relative insensitivity of the distribution ratio of Am(III) to HNO₃ concentration in the range of 0.5 M to 6 M and facilitated stripping of Am(III) with dilute acid. Since a continuous variation study of Am(III) extraction using mixtures of ØOD[IB]CMPO and TBP at a fixed total concentration revealed no evidence of a mixed complex, the TBP appears to be behaving primarily as a phase modifier

The most significant benefit gained from addition of TBP to ØD[IB]CMPO is the increased metal ion loading capacity and extractant compatibility with alicyclic and aliphatic diluents. The use of TBP to overcome phase compatibility with other bifunctional extractants of the carbamoylmethylphosphoryl type and the use of other phase modifiers with ØD[IB]CMPO have also been investigated.     

Mechanistic studies of ruthenium(III)-catalyzed oxidation of DL-methionine by hexacyanoferrate(III) in an alkaline medium

The kinetics and mechanism of ruthenium(III) catalyzed oxidation of dl-methionine by alkaline hexacyanoferrate(III) (HCF(III)) in an alkaline medium were studied spectrophotometrically at 30±0.1°C. The reaction was first-order-dependent each on [HCF(III)] and [ruthenium(III)] and fractional-order-dependent on [alkali]. The rate of the reaction was found to be decreased with the increase in [methionine]. The main product of oxidation was methionine sulfone nitrile (3-(methylsulfonyl)propanenitrile) and it was identified and confirmed by FT-IR and mass spectral studies. Further, no effect of added reaction product was observed. A plausible mechanism was proposed involving complexation between methionine and ruthenium(III) species, [Ru(H₂O)₅OH]²⁺. Thermodynamic parameters for the reaction, E _a and Δ S ^#, were computed using linear least squares method and are found to be 65.83±1.03 kJ/mol and?249.58±3.35 J/K mol, respectively.

     

A convenient one-step synthesis of alkenyl-phosphonio complexes of ruthenium(II), rhodium(III) and iridium(III)

Alkenyl-phosphonio complexes of ruthenium(II), rhodium(III) and iridium(III) were prepared by reactions of [(p-cymene)RuCl₂(PPh₃)] or [C_p^*MCl₂(PPh₃)] (M=Rh, Ir; C_p^*=C₅Me₅) with 1-ethynylbenzene and triphenylphosphine in the presence of KPF₆.     

CHARACTERIZATION OF THE LANTHANUM(III) AND EUROPIUM(III) TRICHLOROACETATE COMPLEXES EXTRACTED WITH 18-CROWN-6

ABSTRACT

Extraction of lanthanide(III) ions with 18-crown-6 (18C6) and trichloroacetate (tea) has been studied. The composition, hydration, and structure of the La(III) and Eu(III) complexes extracted into 1,2-dichloroethane were investigated by using several methods such as the liquid-liquid distribution technique, conductimetry, Karl Fisher titration, laser luminescence spectroscopy, and ¹H NMR. The La(III) complex was found to be a monohydrate, La(tca)₃(18C6)(H₂O), while that of Eu(III) was a mixture of a monohydrate and a dihydrate, i.e., Eu(tca)₃(18C6)(H₂0) and Eu(tca)₃(18C6)(H₂0)₂- The origin of the selectivity by 18C6 which gives much higher extractability of La(III) than of Eu(III) is explained by considering the hydration and probable structure of their complexes.     

Thallium complexes of meso-tetra-(p-chlorophenyl)porphyrin: trifluoroacetato-[meso-tetra(p-chlorophenyl)porphyrinato]thallium(III) and pentafluoropropionato-[meso-tetra(p-chlorophenyl)porphyrinato]thallium(III)

The crystal structures of trifluoroacetato-[meso-tetra(p-chlorophenyl)porphyrinato]thallium(III), Tl[(p-Cl)₄tpp](O₂CCF₃) (1), and pentafluoropropionato-[meso-tetra(p-chlorophenyl)porphyrinato]thallium(III) Tl[(p-Cl)₄tpp](O₂CCF₂CF₃) (2), were determined. The coordination sphere around the Tl³⁺ ion is described as five-coordinate regular square-based pyramid (RSBP) in which the apical site is occupied by an unidentate CF₃CO₂⁻ ligand for 1 whereas the unidentate CF₃CF₂CO₂⁻ ligand occupies the axial site for 2. The plane of the four pyrrole nitrogen atoms [i.e., N(1)–N(4)] strongly bonded to Tl³⁺ is adopted as a reference plane 4N. The Tl³⁺ is moderately out of the 4N plane; its displacement of 0.58 Å (or 0.59 Å) for 1 (or 2) is in the same direction as that of the trifluoroacetate oxygen for 1 (or pentafluoropropionate oxygen for 2). The free energy of activation at the coalescence temperature T_c for the intermolecular trifluoroacetate exchange for 1 in CD₂Cl₂ is found to be ΔG^≠₁₇₈=36.6 kJ/mol whereas the intermolecular pentafluoropropionate exchange for 2 in CD₂Cl₂ is determined to be ΔG^≠₂₁₃=41.5 kJ/mol through ¹⁹F and ¹³C NMR temperature-dependent measurements.     

Mechanistic Aspects of Os(VIII)/Ru(III) Catalysed Oxidation of L-phenylalanine by Ag(III) Periodate Complex in Aqueous Alkaline Medium

The kinetics of oxidation of ruthenium(III) (Ru(III)) and osmium(VIII) (Os(VIII)) catalysed oxidation of L-phenylalanine (L-Pal) by diperiodatoargentate(III) (DPA) in aqueous alkaline medium at 27 °C and a constant ionic strength of 0.25 mol dm^?3 was studied spectrophotometrically. The involvement of free radicals was observed in the reactions. The reaction between DPA and L-Pal in alkaline medium exhibits stoichiometry as [L-Pal]:[DPA] = 1:1. The reaction is of first order in [Os(VIII)], [Ru(III)] and [DPA] and has negative fractional order in [IO₄ ^?]. It has less than unit order in [L-Pal] and [OH^?]. However, the order in [L-Pal] and [OH^?] changes from first order to zero order as their concentrations increase. The main oxidation products were identified by spot test and spectral studies. The probable mechanisms were proposed and discussed. The catalytic constant (K _c) was also calculated for Os(VIII) and Ru(III) catalysis at different temperatures. The activation parameters with respect to slow step of the mechanisms were computed and discussed and thermodynamic quantities were also calculated. It has been observed that the catalytic efficiency for the present reaction is in the order of Os(VIII) > Ru(III). The active species of catalyst and oxidant have been identified.     

Adsorption of Eu(III), Th(IV), and U(VI) by mesoporous solid materials bearing sulfonic acid and sulfamic acid functionalities

ABSTRACT

SBA-15 mesoporous materials modified by sulfonic acid and sulfamic acid functionalities, abbreviated as SBA-15/SO₃H and SBA-15/NHSO₃H, were synthesized and applied for the removal–separation of Eu(III), Th(IV), and U(VI). SBA-15/NHSO₃H showed an excellent selectivity toward U(VI), while SBA-15/SO₃H was more efficient adsorbent for Eu(III) and Th(IV). It was found that in the presence of KNO₃ (1 mol L^?1), the separation of Eu(III)/Th(IV) from their mixtures is possible. The results of the sorption behavior indicated a high adsorption capacity toward U(VI) and Th(IV) ions (140.5 and 106.7 mg g^?1, respectively) and ultrafast kinetics (15 min) in Eu(III) adsorption.     

Physicochemical Aspects on Fluoride Adsorption for Removal from Water by Synthetic Hydrous Iron(III) – Chromium(III) Mixed Oxide

Fluoride removal with varying different parameters at 303 ± 1.6 K and pH 6.5 ± 0.2 was investigated by hydrous iron(III)-chromium(III) bimetal oxide. The kinetic and equilibrium data fitted with the pseudo-second order and Langmuir isotherm equations very well (R² = 0.99?1.00), respectively. The Langmuir capacity (θ) and free energy (E_DR) of adsorption evaluated were 16.34 (±0.50) mg·g^?1 and 15.81 kJ·mol^?1, respectively. The estimated thermodynamic parameters viz. ΔH⁰, ΔG⁰, and ΔS⁰ indicated that the reaction was endothermic but spontaneous for entropy increase. The small-scale column filtration of high fluoride (C₀ = 7.37 mg·L^?1) water gave encouraging results.