Extraction and complexation studies with 2,6-bis(5-(-butyl)-1-pyrazol-3-yl)pyridine in the presence of 2-bromohexanoic acid.

To improve the understanding of the extraction chemistry of An(iii) and Ln(iii) with N-donor ligands 2,6-bis(5-(-butyl)-1-pyrazol-3-yl)pyridine (C4-BPP) in the presence of 2-bromohexanoic acid was investigated. Extraction studies showed an excellent separation factor of SF ≈ 200 and SF ≈ 60 in comparison with the structurally similar ligand 2,6-bis(5-neopentyl-1-pyrazol-3-yl)pyridine C5-BPP (SF ≈ 100), even though C5-BPP showed significantly higher stability constants. Time-resolved laser fluorescence spectroscopy (TRLFS) studies revealed the formation of the ternary 1 : 1 and 1 : 2 complexes [Eu(C4-BPP) (2-bromohexanoate) ] ( = 1-2) ( and ).

6-(6-Methyl-1,2,4,5-Tetrazine-3-yl)-2,2'-Bipyridine: A N-Donor Ligand for the Separation of Lanthanides(III) and Actinides(III).

Here, we report the synthesis of the 6-(6-methyl-1,2,4,5-tetrazine-3-yl)-2,2'-bipyridine (MTB) ligand that has been developed for lanthanide/actinide separation. A multimethod study of the complexation of MTB with trivalent actinide and lanthanide ions is presented. Single-crystal X-ray diffraction measurements reveal the formation of [Ce(MTB)(NO)], [Pr(MTB)(NO)HO], and [Ln(MTB)(NO)MeCN] (Ln = Nd, Sm, Eu, Gd).

Insights into the Complexation Mechanism of a Promising Lipophilic PyTri Ligand for Actinide Partitioning from Spent Nuclear Fuel.

The challenging issue of spent nuclear fuel (SNF) management is being tackled by developing advanced technologies that point to reduce environmental footprint, long-term radiotoxicity, volumes and residual heat of the final waste, and to increase the proliferation resistance. The advanced recycling strategy provides several promising processes for a safer reprocessing of SNF. Advanced hydrometallurgical processes can extract minor actinides directly from Plutonium and Uranium Reduction Extraction raffinate by using selective hydrophilic and lipophilic ligands.

Complexation and Extraction Studies of Trivalent Actinides and Lanthanides with Water-Soluble and CHON-Compatible Ligands for the Selective Extraction of Americium.

Novel hydrophilic ligands to selectively separate Am(III) are synthesized: 3,3'-([2,2'-bipyridine]-6,6'-diylbis(1-1,2,3-triazole-4,1-diyl))bis(propan-1-ol) (PrOH-BPTD) and 3,3'-([2,2'-bipyridine]-6,6'-diylbis(1-1,2,3-triazole-4,1-diyl))bis(ethan-1-ol) (EtOH-BPTD). The complexation of An(III) and Ln(III) with PrOH- and EtOH-BPTD is studied by time-resolved laser fluorescence spectroscopy. [ML] is found for both Cm(III) and Eu(III), while [ML] is only formed with Cm(III).

Spectroscopic investigation of the covalence of An(III) complexes with tetraethylcarboxamidopyridine.

In this work, we report a combined NMR spectroscopic and time-resolved laser fluorescence spectroscopic (TRLFS) study of the complexation of ,,','-tetraethyl-2,6-carboxamidopyridine (Et-Pic) with Ln(III) (La, Sm, Eu, and Lu), Y(III) and An(III) (Am and Cm). The focal point of this study was the metal-ligand interaction in the [M(Et-Pic)] (M = An and Ln) complexes. The NMR analyses found slight differences between the An(III)-N and Ln(III)-N interactions in contrast to the similar properties of the Am(III)-O and Ln(III)-O interactions.

Complexation of Np(V) with the Dicarboxylates, Malonate, and Succinate: Complex Stoichiometry, Thermodynamic Data, and Structural Information.

The complexation of Np(V) with malonate and succinate is studied by different spectroscopic techniques, namely, attenuated total reflection Fourier transform infrared (ATR FT-IR) and extended X-ray absorption fine-structure (EXAFS) spectroscopy, as well as by quantum chemistry to determine the speciation, thermodynamic data, and structural information of the formed complexes. For complex stoichiometries and the thermodynamic functions (log β(Θ), ΔH, ΔS), near infrared absorption spectroscopy (vis/NIR) is applied. The complexation reactions are investigated as a function of the total concentration of malonate ([Mal]) and succinate ([Succ]), ionic strength [ = 0.

Impact of Solvent Polarity on the Ligand Configuration in Tetravalent Thorium N-Donor Complexes.

A combined NMR spectroscopic and theoretical study on the complexation of diamagnetic Th(IV) with 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (Pr-BTP) was performed. Different ligand configurations were observed for [Th(Pr-BTP)] complexes depending on the solvent's ability to actively form hydrogen bonds. In polar aprotic solvents, a complex is observed, which is isostructural with [M(Pr-BTP)] (M = Am, Ln) complexes studied earlier.

Trivalent Actinide Ions Showing Tenfold Coordination in Solution.

Trivalent actinides generally exhibit ninefold coordination in solution. 2,6-Bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (nPr-BTP), a tridentate nitrogen donor ligand, is known to form ninefold coordinated 1:3 complexes, [An(nPr-BTP)] (An = U, Pu, Am, Cm) in solution. We report a Cm(III) complex with tenfold coordination in solution, [Cm(nPr-BTP)(NO)].

Spectroscopic characterisation and thermodynamics of the complexation of Np(V) with sulfate up to 200 °C.

In the present work the complexation of Np(V) with sulfate in aqueous solution is studied in a temperature range up to 200 °C by absorption spectroscopy. For this purpose, a new spectroscopic setup is implemented and tested for its suitability for Vis/NIR absorption spectroscopy at elevated temperatures. The complexation of Np(V) with sulfate is studied as a function of the total ligand concentration at various temperatures (T = 25-200 °C) and ionic strengths (I(NaClO) = 1.

Tris-{hydridotris(1-pyrazolyl)borato}actinide Complexes: Synthesis, Spectroscopy, Crystal Structure, Bonding Properties and Magnetic Behaviour.

The isostructural compounds of the trivalent actinides uranium, neptunium, plutonium, americium, and curium with the hydridotris(1-pyrazolyl)borato (Tp) ligand An[η -HB(N C H ) ] (AnTp ) have been obtained through several synthetic routes. Structural, spectroscopic (absorption, infrared, laser fluorescence) and magnetic characterisation of the compounds were performed in combination with crystal field, density functional theory (DFT) and relativistic multiconfigurational calculations. The covalent bonding interactions were analysed in terms of the natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) models.

Thermodynamics and Structure of Neptunium(V) Complexes with Formate. Spectroscopic and Theoretical Study.

The temperature and ionic strength dependences of the complex formation of NpO with formate in aqueous solution are studied by absorption spectroscopy ( = 0.5-4.0 mol kg, = 20-85 °C, [Form] = 0-0.

Activation of the Aromatic Core of 3,3'-(Pyridine-2,6-diylbis(1-1,2,3-triazole-4,1-diyl))bis(propan-1-ol)-Effects on Extraction Performance, Stability Constants, and Basicity.

The "CHON" compatible water-soluble ligand 3,3'-(pyridine-2,6-diylbis(1-1,2,3-triazole-4,1-diyl))bis(propan-1-ol) (PTD) has shown promise for selectively stripping actinide ions from an organic phase containing both actinide and lanthanide ions, by preferential complexation of the former. Aiming at improving its complexation properties, PTD-OMe was synthesized, bearing a methoxy group on the central pyridine ring, thus increasing its basicity and hence complexation strength. Unfortunately, solvent extraction experiments in the range of 0.

Exploring the Subtle Effect of Aliphatic Ring Size on Minor Actinide-Extraction Properties and Metal Ion Speciation in Bis-1,2,4-Triazine Ligands.

The synthesis and evaluation of three novel bis-1,2,4-triazine ligands containing five-membered aliphatic rings are reported. Compared to the more hydrophobic ligands 1-3 containing six-membered aliphatic rings, the distribution ratios for relevant f-block metal ions were approximately one order of magnitude lower in each case. Ligand 10 showed an efficient, selective and rapid separation of Am and Cm from nitric acid.

Interdisciplinary Round-Robin Test on Molecular Spectroscopy of the U(VI) Acetate System.

A comprehensive molecular analysis of a simple aqueous complexing system-U(VI) acetate-selected to be independently investigated by various spectroscopic (vibrational, luminescence, X-ray absorption, and nuclear magnetic resonance spectroscopy) and quantum chemical methods was achieved by an international round-robin test (RRT). Twenty laboratories from six different countries with a focus on actinide or geochemical research participated and contributed to this scientific endeavor. The outcomes of this RRT were considered on two levels of complexity: first, within each technical discipline, conformities as well as discrepancies of the results and their sources were evaluated.

Interaction of Cm(III) with human serum albumin studied by time-resolved laser fluorescence spectroscopy and NMR.

The complexation of Cm(III) with human serum albumin (HSA) was investigated using time-resolved laser fluorescence spectroscopy (TRLFS). The Cm(III) HSA species is dominating the speciation between pH 7.0 and 9.

Incorporation of transuranium elements: coordination of Cm(iii) to human serum transferrin.

The coordination environment of Cm(iii) bound at the Fe(iii) binding sites of transferrin was investigated using a combined experimental and theoretical approach. Complexation studies with two hTf/2N single point mutants, Y95F (Tyr → Phe) and H249A (His → Ala) were performed. The substitution of Tyr 95 by the non-complexing Phe prevents Cm(iii) from forming of a strong, multidentate complex with the mutant.

A spectroscopic study of the complexation reaction of trivalent lanthanides with a synthetic acrylate based PCE-superplasticizer.

The interaction between different trivalent lanthanides and a synthetic acrylate based PCE-superplasticizer (52IPEG4.5) is investigated by using a combination of laser- and synchrotron based spectroscopic techniques. Time-resolved laser fluorescence spectroscopy (TRLFS) is used to obtain thermodynamic data (stability constants (log β'(T)), reaction enthalpy (ΔH) and entropy(ΔS)) of the complexation reaction of Eu(III) and 52IPEG4.

Stoichiometry of An(iii)-DMDOHEMA complexes formed during solvent extraction.

N,N'-Dimethyl,N,N'-dioctylhexylethoxymalonamide (DMDOHEMA) is used to separate An(iii) and Ln(iii) from fission products in several liquid-liquid extraction processes that aim at recycling actinides. The stoichiometry of the extracted complexes is important for a complete understanding of the processes. The presented work focuses on the complexation of Cm(iii) with DMDOHEMA studied by TRLFS in mono- and biphasic (solvent extraction) systems.

Coordination and Thermodynamics of Trivalent Curium with Malonate at Increased Temperatures: A Spectroscopic and Quantum Chemical Study.

The complexation of Cm(III) with malonate is studied by time-resolved laser fluorescence spectroscopy (TRLFS) in the temperature range from 25 to 90 °C. Three complexes ([Cm(Mal)], n = 1, 2, 3) are identified and their molar fractions are determined as a function of the ligand concentration, the ionic strength, and the temperature. A general shift of the chemical equilibrium toward higher complexes with increasing temperature is observed, with the [CmMal] complex forming only at T > 40 °C.

4,4'-Di-tert-butyl-6-(1H-tetrazol-5-yl)-2,2'-bipyridine: modification of a highly selective N-donor ligand for the separation of trivalent actinides from lanthanides.

In the present work, the complexation and extraction behaviour of 4,4'di-tert-butyl-6-(1H-tetrazol-5-yl)-2,2'-bipyridine (HNbubipy) towards trivalent actinides (An(iii)) and lanthanides (Ln(iii)) is studied by spectroscopic methods, liquid-liquid extraction, and quantum chemical calculations. The ligand synthesis of HNbubipy as well as its application in coordination chemistry of the 4f elements is described. Reaction of HNbubipy with [Ln(NO)·6HO] (Ln = Sm, Eu) results in [HNbubipy][Ln(Nbubipy)(NO)(HO)].

Complexation of Actinide(III) and Lanthanide(III) with HTPAEN for a Separation of Americium from Curium and Lanthanides.

Previous studies have identified the TPAEN ligand as a potentially appropriate complexing agent in solvent extraction processes for the separation of americium (Am(III)) from the fission products including lanthanide (Ln(III)) and curium (Cm(III)) ions, a challenging issue for advanced nuclear fuel recycling. To get insight into the selectivity of this ligand, the complexation of selected trivalent Ln(III) and actinide (An(III)) cations with TPAEN was investigated in solution. First, the structure and stoichiometry of the TPAEN complex with Am(III) were characterized by extended X-ray absorption fine structure spectroscopy (EXAFS).

Combined EXAFS Spectroscopic and Quantum Chemical Study on the Complex Formation of Am(III) with Formate.

The complexation of Am(III) with formate in aqueous solution is studied as a function of the pH value using a combination of extended X-ray absorption fine structure (EXAFS) spectroscopy, iterative transformation factor analysis (ITFA), and quantum chemical calculations. The Am L-edge EXAFS spectra are analyzed to determine the molecular structure (coordination numbers; Am-O and Am-C distances) of the formed Am(III)-formate species and to track the shift of the Am(III) speciation with increasing pH. The experimental data are compared to predictions from density functional calculations.

A thermodynamical and structural study on the complexation of trivalent lanthanides with a polycarboxylate based concrete superplasticizer.

The complexation of trivalent lanthanides with a commercial polycarboxylate based concrete superplasticizer (Glenium® 51) is investigated using different spectroscopic techniques. Time-resolved laser fluorescence spectroscopy (TRLFS) in combination with a charge neutralization model is used to determine temperature dependent conditional stability constants (log β'(T)) for the complexation of Eu(iii) with Glenium® 51 in 0.1 mol kg NaCl solution in the temperature range of 20-90 °C.

Time-Resolved Laser Fluorescence Spectroscopy Study of the Coordination Chemistry of a Hydrophilic CHON [1,2,3-Triazol-4-yl]pyridine Ligand with Cm(III) and Eu(III).

The complexation of Cm(III) and Eu(III) with the novel i-SANEX complexing agent 2,6-bis[1-(propan-1-ol)-1,2,3-triazol-4-yl]pyridine (PTD) was studied by time-resolved laser fluorescence spectroscopy (TRLFS). The formation of 1:3, 1:2, and 1:1 metal/ligand complexes was identified upon increasing PTD concentration in 10 mol/L HClO and in 0.44 mol/L HNO solutions.