Utility of Interchangeable Coordination Modes of ,'-Dialkyl-2,6-pyridinediamide Tridentate Pincer Ligands for Solvent Extraction of Pd(II) and Zr(IV) from High-Level Radioactive Liquid Waste.

A new class of ligands, ,'-dialkyl-2,6-pyridinediamide (DRPDA), has been designed with the specific intention of exhibiting interchangeable diversity in coordination modes, including organometallic interactions, for the purpose of solvent extraction of elements relevant to the proper treatment of high-level radioactive liquid waste (HLLW) generated after nuclear fuel reprocessing. Consequently, DRPDA has been observed to extract Pd(II) and Zr(IV) from HNO(aq) to 1-octanol in nearly quantitative yields when the selected ligand is sufficiently hydrophobic. However, concomitance of some of other HLLW components were also found.

Controlling mixed-valence states of pyridyldiimino-bis(-phenolato) ligand radical in uranyl(VI) complexes.

Combination of a uranyl(VI) ion (UO) with a redox-active ligand results in characteristic electronic structures that cannot be achieved by either component alone. In this study, three UO complexes that bear symmetric or asymmetric 2,6-diiminopyridine-based ligands were synthesized and found to exhibit a first redox couple between -1.17 V and -1.

Gallium recovery from red mud: Integration of solvent extraction and siderophore assisted technologies.

Gallium (Ga) recovery from the red mud, though important has never been successful due to several technical and economic reasons such as contaminant interference and the high cost of membranes due to their faster saturation resulting in the clogging of membranes with contaminants. This study demonstrated the recovery of Ga by a combination of HCl-based leaching, Fe/Al/Ti separation, and recovery of Ga using Cyphos IL 104-based solvent extraction and complexation of Ga with desferrioxamine B as a proof-of-principle of the GaLIophore technology. The main leaching parameters such as concentrations of acids, time and temperature of the reaction, and solid-to-liquid ratio have been systematically investigated.

Efficient density functional theory directed identification of siderophores with increased selectivity towards indium and germanium.

Siderophores are promising ligands for application in novel recycling and bioremediation technologies, as they can selectively complex a variety of metals. However, with over 250 known siderophores, the selection of suiting complexants in the wet lab is impractical. Thus, this study established a density functional theory (DFT) based approach to efficiently identify siderophores with increased selectivity towards target metals on the example of germanium and indium.

Towards tailoring hydrophobic interaction with uranyl(VI) oxygen for C-H activation.

Bovine serum albumin (BSA) has a uranyl(VI) binding hotspot where uranium is tightly bound by three carboxylates. Uranyl oxygen is "soaked" into the hydrophobic core of BSA. Isopropyl hydrogen of Val is trapped near UO and upon photoexcitation, C-H bond cleavage is initiated.

Fate of Oxidation States at Actinide Centers in Redox-Active Ligand Systems Governed by Energy Levels of 5 f Orbitals.

We report the formation of a Np complex from the complexation of Np O with the redox-active ligand tBu-pdiop =2,6-bis[N-(3,5-di-tert-butyl-2-hydroxyphenyl)iminomethyl]pyridine. To the best of our knowledge, this is the first example of the direct complexation-induced chemical reduction of Np O to Np . In contrast, the complexation of U O with tBu-pdiop did not induce the reduction of U O , not even after the two-electron electrochemical reduction of [U O (tBu-pdiop)].

Interaction Between the Transferrin Protein and Plutonium (and Thorium), What's New?

Transferrin (Tf) is a glycoprotein that transports iron from the serum to the various organs. Several studies have highlighted that Tf can interact with metals other than Fe(III), including actinides that are chemical and radiological toxics. We propose here to report on the behavior of Th(IV) and Pu(IV) in comparison with Fe(III) upon Tf complexation.

Eu(III) and Cm(III) Complexation by the Aminocarboxylates NTA, EDTA, and EGTA Studied with NMR, TRLFS, and ITC-An Improved Approach to More Robust Thermodynamics.

The complex formation of Eu(III) and Cm(III) was studied via tetradentate, hexadentate, and octadentate coordinating ligands of the aminopolycarboxylate family, viz., nitrilotriacetate (NTA), ethylenediaminetetraacetate (EDTA), and ethylene glycol-bis(2-aminoethyl ether)-,,','-tetraacetate (EGTA), respectively. Based on the complexones' p values obtained from H nuclear magnetic resonance (NMR) spectroscopic pH titration, complex formation constants were determined by means of the parallel-factor-analysis-assisted evaluation of Eu(III) and Cm(III) time-resolved laser-induced fluorescence spectroscopy (TRLFS).

Europium(III) Meets Etidronic Acid (HEDP): A Coordination Study Combining Spectroscopic, Spectrometric, and Quantum Chemical Methods.

Etidronic acid (1-Hydroxyethylidene-1,1-diphosphonic acid, HEDP, HL) is a proposed decorporation agent for U(VI). This paper studied its complex formation with Eu(III), an inactive analog of trivalent actinides, over a wide pH range, at varying metal-to-ligand ratios (M:L) and total concentrations. Combining spectroscopic, spectrometric, and quantum chemical methods, five distinct Eu(III)-HEDP complexes were found, four of which were characterized.

Crystal Structures of Ce(IV) Nitrates with Bis(2-pyrrolidone) Linker Molecules Deposited from Aqueous Solutions with Different HNO Concentrations.

We investigated the molecular and crystal structures of Ce(IV) compounds deposited under different [HNO] with bis(2-pyrrolidone) linker molecules having a -1,4-cyclohexyl bridging moiety (L). As a result, we found that, after loading L, Ce(IV) in HNO(aq) exclusively provides one of different crystalline phases, (HL)[Ce(NO)] or [Ce(μ-O)-(NO)(L)] 2D MOF, depending on [HNO]. The former has been obtained at [HNO] = 4.

Lanmodulin peptides - unravelling the binding of the EF-Hand loop sequences stripped from the structural corset.

Lanmodulin (LanM), a naturally lanthanide (Ln)-binding protein with a remarkable selectivity for Lns over Ca(ii) and affinities in the picomolar range, is an attractive target to address challenges in Ln separation. Why LanM has such a high selectivity is currently not entirely understood; both specific amino acid sequences of the EF-Hand loops and cooperativity effects have been suggested. Here, we removed the effect of cooperativity and synthesised all four 12-amino acid EF-Hand loop peptides, and investigated their affinity for two Lns (Eu(iii) and Tb(iii)), the actinide Cm(iii) and Ca(ii).

2-Phosphonobutane-1,2,4,-Tricarboxylic Acid (PBTC): pH-Dependent Behavior Studied by Means of Multinuclear NMR Spectroscopy.

Although 2-phosphonobutane-1,2,4,-tricarboxylic acid, PBTC, has manifold industrial applications, relevant and reliable data on the protonation of PBTC are poor. However, these data are critical parameters for ascertaining PBTC speciation, especially with regard to a sound structural and thermodynamic characterization of its metal ion complexes. A rigorous evaluation of pH-dependent H, C, and P chemical shifts along with accessible scalar spin-spin coupling constants () was performed in order to determine the p values of PBTC in 0.

Anion-specific structure and stability of guanidinium-bound DNA origami.

While the folding of DNA into rationally designed DNA origami nanostructures has been studied extensively with the aim of increasing structural diversity and introducing functionality, the fundamental physical and chemical properties of these nanostructures remain largely elusive. Here, we investigate the correlation between atomistic, molecular, nanoscopic, and thermodynamic properties of DNA origami triangles. Using guanidinium (Gdm) as a DNA-stabilizing but potentially also denaturing cation, we explore the dependence of DNA origami stability on the identity of the accompanying anions.

Synthesis and characterization of a uranyl(VI) complex with 2,6-pyridine-bis(methylaminophenolato) and its ligand-centred aerobic oxidation mechanism to a diimino derivative.

A uranyl(VI) complex with 2,6-bis(3,5-di--butyl--phenolateaminomethyl)pyridine (UO(Bu-pdaop), 1) was synthesized and thoroughly characterized by H NMR, IR, elemental analysis, and single-crystal XRD. Right after the dissolution of complex 1 in pyridine or DMSO, the solution was pale red, whereas it gradually turned to dark purple under an ambient atmosphere. H NMR spectra at the initial and final states suggested that both of the two aminomethyl groups in 1 were converted to azomethine ones through aerobic oxidation.

Fully Chelating NO-Pentadentate Planar Ligands Designed for the Strongest and Selective Capture of Uranium from Seawater.

Based on the unique fivefold equatorial coordination of UO, water-compatible pentadentate planar ligands, Hsaldian and its derivatives, were designed for the strong and selective capture of UO in seawater. In the simulated seawater condition (0.5 M NaCl + 2.

Hydrophobic core formation and secondary structure elements in uranyl(VI)-binding peptides.

Cyclic peptides as well as a modified EF-hand motif of calmodulin have been newly designed to achieve high affinity towards uranyl(VI). Cyclic peptides may be engineered to bind uranyl(VI) to its backbone under acidic conditions, which may enhance its selectivity. For the modified EF-hand motif of calmodulin, strong electrostatic interactions between uranyl(VI) and negatively charged side chains play an important role in achieving high affinity; however, it is also essential to have a secondary structure element and formation of hydrophobic cores in the metal-bound state of the peptide.

Interaction of Th(IV), Pu(IV) and Fe(III) with ferritin protein: how similar?

Ferritin is the main protein of Fe storage in eukaryote and prokaryote cells. It is a large multifunctional, multi-subunit protein consisting of heavy H and light L subunits. In the field of nuclear toxicology, it has been suggested that some actinide elements, such as thorium and plutonium at oxidation state +IV, have a comparable `biochemistry' to iron at oxidation state +III owing to their very high tendency for hydrolysis and somewhat comparable ionic radii.

Effects of Substituents on the Molecular Structure and Redox Behavior of Uranyl(V/VI) Complexes with NO-Donating Schiff Base Ligands.

Uranyl(VI) complexes with pentadentate NO-donating Schiff base ligands having various substituents at the (R) and/or (R) positions on phenolate moieties, R,R-saldien, were synthesized and thoroughly characterized by H nuclear magnetic resonance, infrared, elemental analysis, and single-crystal X-ray diffraction. Molecular structures of UO(R,R-saldien) are more or less affected by the electron-donating or -withdrawing nature of the substituents. The redox behavior of all UO(R,R-saldien) complexes was investigated to understand how substituents introduced onto the ligand affect the redox behavior of these uranyl(VI) complexes.

Impact of the Microbial Origin and Active Microenvironment on the Shape of Biogenic Elemental Selenium Nanomaterials.

The shape of nanomaterials affects their colloidal properties, cellular uptake, and fate in the environment. The microbial origin and microenvironment can play a role in altering the shape of the nanomaterial. However, such studies have never been conducted.

Dimeric and Trimeric Uranyl(VI)-Citrate Complexes in Aqueous Solution.

This research addresses a subject discussed controversially for almost 70 years. The interactions between the uranyl(VI) ion, U(VI), and citric acid, HCit, were examined using a multi-method approach comprising nuclear magnetic resonance (NMR), ultraviolet-visible (UV-vis), attenuated total reflectance Fourier-transform infrared (ATR FT-IR), and extended X-ray absorption fine-structure (EXAFS) spectroscopies as well as density functional theory (DFT) calculations. Combining O NMR spectroscopy and DFT calculation provided an unambiguous decision on complex configurations, evidencing for the first time that the dimeric complex, (UO)(HCit), exists as two diastereomers with the -isomer in aqueous solution strongly favored over the -isomer.

Quenching Mechanism of Uranyl(VI) by Chloride and Bromide in Aqueous and Non-Aqueous Solutions.

A major hindrance in utilizing uranyl(VI) luminescence as a standard analytical tool, for example, in environmental monitoring or nuclear industries, is quenching by other ions such as halide ions, which are present in many relevant matrices of uranyl(VI) speciation. Here, we demonstrate through a combination of time-resolved laser-induced fluorescence spectroscopy, transient absorption spectroscopy, and quantum chemistry that coordinating solvent molecules play a crucial role in U(VI) halide luminescence quenching. We show that our previously suggested quenching mechanism based on an internal redox reaction of the 1:2-uranyl-halide-complex holds also true for bromide-induced quenching of uranyl(VI).

DNA-Mediated Stack Formation of Nanodiscs.

Membrane-scaffolding proteins (MSPs) derived from apolipoprotein A-1 have become a versatile tool in generating nano-sized discoidal membrane mimetics (nanodiscs) for membrane protein research. Recent efforts have aimed at exploiting their controlled lipid protein ratio and size distribution to arrange membrane proteins in regular supramolecular structures for diffraction studies. Thereby, direct membrane protein crystallization, which has remained the limiting factor in structure determination of membrane proteins, would be circumvented.

Trimeric uranyl(vi)-citrate forms Na, Ca, and La sandwich complexes in aqueous solution.

M. Basile, et al., Chem.

How Does Iron Storage Protein Ferritin Interact with Plutonium (and Thorium)?

The impact of the contamination of living organisms by actinide elements has been a constant subject of attention since the 1950s. But to date still little is understood. Ferritin is the major storage and regulation protein of iron in many organisms, it consists of a protein ring and a ferrihydric core at the center.

Crystallization of colourless hexanitratoneptunate(iv) with anhydrous H countercations trapped in a hydrogen bonded polymer with diamide linkers.

Colourless crystalline compounds of centrosymmetric [Np(NO)] were yielded from 3 M HNO aq in the presence of double-headed 2-pyrrolidone derivatives (L). In the obtained crystal structures, H was also involved as a countercation to compensate for the negative charge of [Np(NO)], where the initial hydration around H was fully removed during crystallization despite it having the strongest hydration enthalpy. Instead, this anhydrous H was captured by L to form a [H⋯L] hydrogen bonded polymer.