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.

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)].

Solid-State Schikorr Reaction from Ferrous Chloride to Magnetite with Hydrogen Evolution as the Kinetic Bottleneck.

The selective formation of meta-stable FeO from ferrous sources by suppressing its oxidative conversion to the most stable hematite (α-FeO) is challenging under oxidative conditions for solid-state synthesis. In this work, we investigated the conversion of iron(II) chloride (FeCl) to magnetite (FeO) under inert atmosphere in the presence of steam, and the obtained oxides were analyzed by atomic-resolution TEM, Fe Mössbauer spectroscopy, and the Verwey transition temperature (). The reaction proceeded in two steps, with HO as the oxide source in the initial step and as an oxidant in the second step.

How does chemistry contribute to circular economy in nuclear energy systems to make them more sustainable and ecological?

While one should be aware that its zero CO emission is actually achievable only when electric power is generated, nuclear power is one of the most viable and proven "carbon-free" energy sources to provide baseload electricity to the current energy-demanding society. Even after the power generation, the major part of spent nuclear fuels still consists of recyclable nuclear fuel materials such as U and Pu, promising circular economy of nuclear energy systems in principle. However, actual situations are not very simple due to the following issues: (1) resource security of nuclear fuel materials, (2) issues of depleted uranium, and (3) treatment and disposal of high-level radioactive wastes.

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.

Non-aqueous bonding of leuprorelin to ochratoxin A for peptide-based solid-phase extraction.

The anticancer therapeutic leuprorelin was found to have excellent affinity to the carcinogen ochratoxin A (OTA), with an equilibrium constant of 2.2 × 10 M at 273 K (dissociation constant = 4.5 nM) when functionalized into a mesoporous polymer.

Effects of coordinating heteroatoms on molecular structure, thermodynamic stability and redox behavior of uranyl(vi) complexes with pentadentate Schiff-base ligands.

Uranyl(vi) complexes with pentadentate NO-, NO- and NOS-donating Schiff base ligands, Bu,MeO-saldien-X (X = NH, O and S), were synthesized and thoroughly characterized by H NMR, IR, elemental analysis, and single crystal X-ray diffraction. The crystal structures of UO(Bu,MeO-saldien-X) showed that the U-X bond strength follows U-O ≈ U-NH > U-S. Conditional stability constants ( ) of UO(Bu,MeO-saldien-X) in ethanol were investigated to understand the effect of X on thermodynamic stability.

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.

Complexation-Distribution Separated Solvent Extraction Process Designed for Rapid and Efficient Recovery of Inert Platinum Group Metals.

Previously, we have demonstrated that thermal-assisted techniques can accelerate the extraction of inert platinum group metals (PGMs), while they still have several concerns about difficulty of temperature control in actual extraction contactors and safety risks arising from heating organic solvents. In this study, we report a complexation-distribution separated extraction process for the accelerated extraction of inert PGMs. This extraction method includes two steps: (1) complexation of PGMs with extractants in aqueous solution and (2) distribution of the formed complex from the aqueous phase to organic one.

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.

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.

Crystal Structure of Regularly T -Symmetric [U(NO ) ] Salts with Hydrogen Bond Polymers of Diamide Building Blocks.

Hexanitratouranate(IV), [U(NO ) ] , has been crystallized with anhydrous H -involving hydrogen bond polymers connected by selected diamide building blocks. Thanks to the significant moderation of electrostatic interactions between the anions and cations, the molecular structure of [U(NO ) ] in these compounds is regularly T -symmetric. The f-f transitions stemming from 5f configuration of U are strictly forbidden by the Laporte selection rule in such a centrosymmetric system, so that the obtained compounds are nearly colourless in contrast to other U species usually coloured in green.

Wet chemical processing for nuclear waste glass to retrieve radionuclides.

Here, we show unexpected and significant elution behavior of various elements from simulated nuclear waste glass (NWG) in ∼10° mol dm acidic solutions below 100 °C, where a borosilicate-based glass matrix has been believed to be chemically durable. Most elements like glass main components (Li, B, Na, Ca, Al, and Zn, but except for Si) and simulated radionuclides (Rb, Cs, Sr, Ba, Se, Te, Mn, Pd, Mo, rare earths, Cr, Fe, and Ni) were remarkably eluted from the simulated NWG in ∼10° M HNO aq with Cl at 90 °C. Especially, the elution of Pd is governed by its coordination chemistry including a redox reaction, because Pd(0) present in the simulated NWG has to be oxidized to Pd which forms [PdCl] for its dissolution.

Controlling the lability of uranyl(vi) through intramolecular π-π stacking.

A reaction of UO with cyclohexyldiphenylphosphine oxide (OPCyPh) in ethanol resulted in a perchlorate salt of the 4-fold homoleptic complex, [UO(OPCyPh)](ClO)·EtOH. X-ray structure determination revealed that [UO(OPCyPh)] shows a highly symmetric molecular structure supported by the intramolecular π-π stacking interactions between the phenyl groups of the neighbouring OPCyPh in the equatorial plane of UO. To clarify whether the reactivity of UO is affected by such a unique coordination structure, the ligand exchange kinetics of [UO(OPCyPh)] in non-coordinating solvents has been studied using an NMR line-broadening method.

The oxidation of borohydrides by photoexcited [UO(CO)] .

The carbonate ion is an effective quencher of uranyl(vi) luminescence and makes uranyl(vi) tricarbonate barely luminescent and photochemically inactive. We demonstrate here that photoexcited uranyl(vi) tricarbonate, *[UVIO2(CO3)3]4-, can however oxidize borohydrides (BH3X-, X = H, CN) to give boric acid and H2 gas, reducing itself to [UVO2(CO3)3]5-. This hypothesis was supported by UV-vis and NMR spectroscopy as well as quantum chemical calculations.

Molecular and Crystal Structures of Uranyl Nitrate Coordination Polymers with Double-Headed 2-Pyrrolidone Derivatives.

Double-headed 2-pyrrolidone derivatives (DHNRPs) were designed and synthesized as bridging ligands for the efficient and selective separation of UO from a HNO solution by precipitation. The building blocks, UO(NO) and DHNRPs, were successfully connected to form an infinite 1D coordination polymer. The solubility of [UO(NO)(DHNRP)] is no longer correlated to the hydrophobicity of the ligand but is exclusively governed by the ligand symmetry and packing efficiency.

An aqueous electrolyte of the widest potential window and its superior capability for capacitors.

A saturated aqueous solution of sodium perchlorate (SSPAS) was found to be electrochemically superior, because the potential window is remarkably wide to be approximately 3.2 V in terms of a cyclic voltammetry. Such a wide potential window has never been reported in any aqueous solutions, and this finding would be of historical significance for aqueous electrolyte to overcome its weak point that the potential window is narrow.

Emission properties and Cu(i)-Cu(i) interaction in 2-coordinate dicopper(i)-bis(N-heterocyclic)carbene complexes.

The synthesis, characterization, and emission properties of 2-coordinate dicopper(i) complexes bearing two trimethylene-bridged bis-NHC ligands, [Cu2(L3Me)2](PF6)2 (1), [Cu2(L3Et)2](PF6)2 (2), [Cu2(L3Bu)2](PF6)2 (3), [Cu2(L3MeOPh)2](PF6)2 (4) and [Cu2(L3Mes)2](PF6)2 (5), where L3R denotes trimethylene-bridged bis(N-heterocyclic)carbene (NHC) ligand substituted by two R groups at the nitrogen atoms of NHC, have been investigated. The quantum yield, Φ, and the lifetime, τ, of the emission of 2, are 0.21 and 25 μs, respectively in methanol, which is a well-known solvent for quenching the luminescence of many copper(i) complexes.

Highly emissive copper(I) complexes bearing diimine and bis(diphenylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane.

A highly emissive copper(I) complex bearing (4R,5R)-(-)-4,5-bis(diphenylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane (diop) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (dmpp), [Cu(dmpp)(diop)]PF6 (1·PF6), was newly synthesized. The quantum yield of the luminescence of 1·PF6 in degassed dichloromethane is 0.38, which is one of the highest values among all copper(I) complexes bearing two bidentate ligands, diimine and diphosphine, under the same conditions.

Experimental and theoretical approaches to redox innocence of ligands in uranyl complexes: what is formal oxidation state of uranium in reductant of uranyl(VI)?

Redox behavior of [UO2(gha)DMSO](-)/UO2(gha)DMSO couple (gha = glyoxal bis(2-hydroxanil)ate, DMSO = dimethyl sulfoxide) in DMSO solution was investigated by cyclic voltammetry and UV-vis-NIR spectroelectrochemical technique, as well as density functional theory (DFT) calculations. [UO2(gha)DMSO](-) was found to be formed via one-electron reduction of UO2(gha)DMSO without any successive reactions. The observed absorption spectrum of [UO2(gha)DMSO](-), however, has clearly different characteristics from those of uranyl(V) complexes reported so far.

Extraction of Pd(II), Rh(III) and Ru(III) from HNO(3) aqueous solution to betainium bis(trifluoromethanesulfonyl)imide ionic liquid.

Extraction efficiencies of Pd(ii), Rh(iii), and Ru(iii) from HNO3(aq) to [Hbet][Tf2N] were demonstrated, i.e., Pd(ii) is the most extractable, Rh(iii) is medium extractable, and Ru(iii) is the least extractable.