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A mechanically homogenized composite of expanded graphite and cobalt(II) perrhenate has been described. Cobalt(II) perrhenate was obtained in a reaction of perrhenic acid with cobalt(II) nitrate. A simple mortar homogenization method was used to enhance the intercalation of cobalt species within the carbon matrix. The specific capacitance of the composite was enhanced by 50% (to 78 F/g) in comparison to bare expanded graphite (52 F/g). The electrochemical characteristics were significantly improved, including better cyclability (7% capacitance loss), a lower resistance of the electrode material, and a lower iR drop, with respect to expanded graphite without cobalt(II) perrhenate active species. Expanded graphite, with its unique specific surface area and pore size diameter, was proved to be a potential and cheap carbon support. [ABSTRACT FROM AUTHOR]

In this manuscript we evaluate the X-ray structure of five new pertechnetate derivatives of general formula [M(H2O)4(TcO4)2], M=Mg, Co, Ni, Cu, Zn (compounds 1-5) and one perrhenate compound Zn(H2O)4(ReO4)2 (6). In these complexes the metal center exhibits an octahedral coordination with the pertechnetate units as axial ligands. All compounds exhibit the formation of directional Tc···O Matere bonds (MaBs) that propagate the [M(H2O)4(TcO4)2], into 1D supramolecular polymers in the solid state. Such 1D polymers are linked, generating 2D layers, by combining additional MaBs and hydrogen bonds (HBs). Such concurrent motifs have been analyzed theoretically, suggesting the noncovalent s-hole nature of the MaBs. The interaction energies range from weak (~ - 2 kcal/mol) for the MaBs to strong (~ - 30 kcal/mol) for the MaB+HB assemblies, where HB dominates. In case of M=Zn, the corresponding perrhenate Zn(H2O)4(ReO4)2 complex, has been also synthesized for comparison purposes, resulting in the formation of an isostructural Xray structure, corroborating the structure-directing role of Matere bonds. [ABSTRACT FROM AUTHOR]

Rhenium (Re) is an extremely rare element, with a crustal abundance of approximately 0.4 parts per billion (ppb) and a sea water concentration of 8.3 parts per trillion (ppt). However, Re concentrations in anoxic marine sediments range from 2 to 184 ppb, which is attributed to reduction of the highly soluble perrhenate ion (Re(VII)O4−) to insoluble Re(IV) species. Anoxic sediments typically contain Fe(II) and sulfide species, which could potentially reduce Re(VII) to Re(IV). In this study, we examined the interactions of KReO4 with magnetite (Fe3O4), siderite (FeCO3), vivianite (Fe3(PO4)2•8H2O), green rust (mixed Fe(II)/Fe(III) layered double hydroxide), mackinawite (FeS), and chemically reduced nontronite (NAu-1) using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy to determine the valence state and speciation of Re. Uptake of Re by green rust was rapid, with ~50% associated with the solids within 2 days. In contrast, there was <10% uptake by the other Fe(II) phases over 48 days. Reduction of Re(VII) to Re(IV) was only observed in the presence of green rust, producing clusters of bidentate-coordinated Re(IV)O6 octahedra.. These results suggest that except for green rust, the potential for other Fe(II)-bearing minerals to act as reductants for ReO4− in sedimentary environments requires further investigation. [ABSTRACT FROM AUTHOR]

A mechanically homogenized composite of expanded graphite and cobalt(II) perrhenate has been described. Cobalt(II) perrhenate was obtained in a reaction of perrhenic acid with cobalt(II) nitrate. A simple mortar homogenization method was used to enhance the intercalation of cobalt species within the carbon matrix. The specific capacitance of the composite was enhanced by 50% (to 78 F/g) in comparison to bare expanded graphite (52 F/g). The electrochemical characteristics were significantly improved, including better cyclability (7% capacitance loss), a lower resistance of the electrode material, and a lower iR drop, with respect to expanded graphite without cobalt(II) perrhenate active species. Expanded graphite, with its unique specific surface area and pore size diameter, was proved to be a potential and cheap carbon support.

The selective removal of the β‐emitting pertechnetate ion (99TcO4−) from nuclear waste streams is technically challenging. Herein, a practical approach is proposed for the selective removal of 99TcO4− (or its surrogate ReO4−) under extreme conditions of high acidity, alkalinity, ionic strength, and radiation field. Hollow porous N‐doped carbon capsules loaded with ruthenium clusters (Ru@HNCC) are first prepared, then modified with a cationic polymeric network (R) containing imidazolium‐N+ units (Ru@HNCC‐R) for selective 99TcO4− and ReO4− binding. The Ru@HNCC‐R capsules offer high binding affinities for 99TcO4−/ReO4− under wide‐ranging conditions. An electrochemical redox process then transforms adsorbed ReO4− to bulk ReO3, delivering record‐high removal capacities, fast kinetics, and excellent long‐term durability for removing ReO4− (as a proxy for 99TcO4−) in a 3 m HNO3, simulated nuclear waste‐Hanford melter recycle stream and an alkaline high‐level waste stream (HLW) at the U.S. Savannah River Site (SRS). In situ Raman and X‐ray absorption spectroscopy (XAS) analyses showed that adsorbed Re(VII) is electrocatalytically reduced on Ru sites to a Re(IV)O2 intermediate, which can then be re‐oxidized to insoluble Re(VI)O3 for facile collection. This approach overcomes many of the challenges associated with the selective separation and removal of 99TcO4−/ReO4− under extreme conditions, offering new vistas for nuclear waste management and environmental remediation. [ABSTRACT FROM AUTHOR]

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The preparation of ammine complexes of transition metals having oxidizing anions such as permanganate and perrhenate ions is a great challenge due to possible reactions between ammonia and oxidizing anions during the synthesis of these materials. However, it has an important role in both the development of new oxidants in organic chemistry and especially in the preparation of mixed-metal oxide catalyst precursors and metal alloys for their controlled temperature decomposition reactions. Therefore, in this paper, synthetic procedures to prepare ammonia complexes of transition metal permanganate, pertechnetate, and perrhenate (the VIIB group tetraoxometallates) salts have been comprehensively reviewed. The available data about these compounds' structures and spectroscopic properties, including the presence of hydrogen bonds that act as redox reaction centers during thermal decomposition, are given and evaluated in detail. The nature of the thermal decomposition products has also been summarized. The available information about the role of the ammine complexes of transition metal permanganate salts in organic oxidation reactions, such as the oxidation of benzyl alcohols and regeneration of oxo-compounds from oximes and phenylhydrazones, including the kinetics of these processes, has also been collected. Their physical and chemical properties, including the thermal decomposition characteristics of known diammine (Ag(I), Cd, Zn, Cu(II), Ni(II)), triammine (Ag(I)), and simple or mixed ligand tetraammine (Cu(II), Zn, Cd, Ni(II), Co(II), Pt(II), Pd(II), Co(III)), Ru(III), pentaammine (Co(III), Cr(III), Rh(III) and Ir(III)), and hexaammine (Ni(II), Co(III), Cr(III)) complexes of transition metals with tetraoxometallate(VII) anions (M = Mn, Tc and Re), have been summarized. The preparation and properties of some special mixed ligand/anion/cation-containing complexes, such as [Ru(NH3)4(NO)(H2O)](ReO4)2, [Co(NH3)5(H2O)](ReO4)2, [Co(NH3)5X](MnO4)2 (X = Cl, Br), [Co(NH3)6]Cl2(MnO4), [Co(NH3)5ReO4]X2 (X = Cl, NO3, ClO4, ReO4), and K[Co(NH3)6]Cl2(MnO4)2, are also included. [ABSTRACT FROM AUTHOR]

The extraction of pertechnetate (TcO4−) and perrhenate (ReO4−) by tributyl phosphate (TBP) has been extensively studied, but the structure of the extracted species is subject to debate. In this work, the extraction behavior of TcO4− and ReO4− from both HNO3 and HCl media by TBP in n-dodecane was studied by examining the effects of acid concentration, extractant concentration, and temperature on the extraction. The two anions displayed similar extraction behavior in both the HNO3 and HCl systems, where the distribution ratio of TcO4− was slightly higher than that of ReO4−. The measurement of water content in the organic phase and dynamic light scattering were carried out, which in combination with the extraction behavior indicated that ReO4− was extracted as [H+ReO4−(H2O)8·(TBP)4] and formed microemulsions in the organic phase. Theoretical calculations were performed on the structure of both [H+ReO4−(H2O)8·(TBP)4] and [H+TcO4−(H2O)8·(TBP)4]. The TBP molecules interacted with the [H+ReO4−(H2O)8] and [H+TcO4−(H2O)8] clusters through hydrogen bonding between H2O and the O=P groups, i.e., ReO4− and TcO4− underwent outer-sphere coordination with TBP in the organic phase. Results in this work provide valuable insights into the structures of ReO4− and TcO4− extracted into the organic phase by TBP, and also assist in the analysis of TcO4− species in the PUREX process. [ABSTRACT FROM AUTHOR]

A tripodal anion receptor has been obtained by an easy and fast single-reaction synthesis from commercial reagents. The three ligand arms-bearing aromatic groups able to form anion–π interactions define ligand clefts where large anions, such as perchlorate and perrhenate, are included. We report here the synthesis of the ligand, its acid/base properties in an aqueous solution which has been used to direct the synthesis of anion complexes, and the crystal structure of the free ligand and its anion complexes H3L(ClO4)2·H2O and H3L(ReO4)2. [ABSTRACT FROM AUTHOR]

The β− emitter, rhenium-188 (188Re), has long been recognized as an attractive candidate for targeted cancer radionuclide therapy (TRNT). This transition metal shares chemical similarities with its congener element technetium, whose nuclear isomer technetium-99m (99mTc) is the current workhorse of diagnostic nuclear medicine. The differences between these two elements have a significant impact on the radiolabelling methods and should always receive critical attention. This review aims to highlight what needs to be considered to design a successful radiopharmaceutical incorporating 118Re. Some of the most effective strategies for preparing therapeutic radiopharmaceuticals with 188Re are illustrated and rationalized using the concept of the inorganic functional group (core) and a simple ligand field theoretical model combined with a qualitative definition of frontiers orbitals. Of special interest are the Re(V) oxo and Re(V) nitrido functional groups. Suitable ligands for binding to these cores are discussed, successful clinical applications are summarized, and a prediction of viable future applications is presented. Rhenium-188 decays through the emission of a high energy beta particle (2.12 MeV max energy) and a half-life of 16.9 h. An ideal biological target would therefore be a high-capacity target site (transporters, potential gradients, tumour microenvironment) with less emphasis on saturable targets such as overexpressed receptors on smaller metastases. [ABSTRACT FROM AUTHOR]

[Display omitted] • D201 and IRA-410 resins exhibited fast adsorption kinetics and superior adsorption capacity; • Two resins demonstrated outstanding acid, thermal and irradiation stability; • Two resins could effectively capture ReO4− from simulated Hanford and SRS solutions; • Anion exchange mechanism was elucidated through characterization and DFT calculation. It is still a challenge to capture TcO 4 − from wastewater due to its nature of non-complexing and radioactive. Herein, two types of anion exchange resins (D201 and IRA-410 resin) were selected and explored the adsorption properties for perrhenate (ReO 4 −, as a surrogate for TcO 4 −). It is found that both D201 and IRA-410 resin exhibited fast adsorption kinetic (within 120 min), and superior adsorption capacities, which could reach 671.1 mg g−1 and 561.8 mg g−1 for D201 and IRA-410 resin, respectively. In addition, D201 and IRA-410 resin showed excellent adsorption selectivity for ReO 4 − in the presence of a variety of 1000-fold competing anions (NO 2 −, Cl−, SO 4 2−, and PO 4 3−). Importantly, the two resins still demonstrated outstanding performance after acid/alkaline soaking, calcination procedures as well as high doses of ionizing radiation, they also could remove ReO 4 − from simulated Hanford and SRS wastewater by automatic separation system. Finally, the anion-exchange mechanism was revealed by characterization and DFT. This work demonstrates that D201 and IRA-410 resin are efficient adsorbents for 99Tc removal from nuclear wastewater and provides a basis for designing other novel anion exchange materials for capturing ReO 4 − and TcO 4 −. [ABSTRACT FROM AUTHOR]

Sustainable photocatalysis can effectively reduce the radioactive 99 TcO 4 - to less soluble TcO 2 · n H 2 ). Here, we quantitatively investigate photocatalytic remediation conditions for Tc-contaminated water stimulated by the analogue perrhenate (ReO 3 - ). Here, we quantitatively investigate photocatalytic remediation conditions for Tc-contaminated water stimulated by the analogue perrhenate (ReO 4 - ) in the presence of NO 3 - , and we elucidate the influence mechanism of NO 3 - by in situ characterizations. The interfering NO 3 - can compete with Re(VII) for the carbonyl radical (·CO 2 - ) produced by formic acid (HCOOH) oxidation to generate nitrogen-containing products such as NH 4 + , NO 2 - , and NO x , resulting in the decrease in the Re(VII) reduction ratio. Under the conditions of 4% (volume ratio) HCOOH and pH = 3, the yield of NO x is the lowest, and the selectivity of N 2 reaches 93%, which makes the overall reaction more in line with the pollution-free concept. The X-ray absorption fine structure reveals that the redox product Re(IV) mainly exists in the form of ReO 2 · n H 2 O(s) and is accompanied by a decrease with the increase in NO 3 - concentration. Re(VII)/Tc(VII) reduction suffers from a serious interferential effect of NO 3 - , whereas the higher the concentration of NO 3 - , the more conducive to slowing down the reoxidation of the reduction products, which is advantageous for the subsequent sequestration or separation.

H2Gua(ReO4)2, HGuaReO4 and HGuaTcO4 were first obtained and structurally characterized. Two types of anionic interactions were found in the structure with the twice protonated cation. One type of the rare double‐lock interaction of perrhenate anions was found in the case of the singly protonated guanine salt. Singly charged cations are linked by hydrogen bonds into layer. π‐Stacking interactions between these layers form 3‐dimensional frame. Multiple and relatively abundant anion‐π interactions are formed in H2Gua(ReO4)2 as compared to HGuaReO4 and HGuaTcO4. Different types of crystal packing are formed in the compounds under research. Hirshfeld surface analysis has given evidence that the main contribution to intermolecular interactions for the cations is made by hydrogen bonds of the O⋅⋅⋅H/H⋅⋅⋅O type in all structures, O⋅⋅⋅C/C⋅⋅⋅O and O⋅⋅⋅N/N⋅⋅⋅O interactions in H2Gua(ReO4)2, N⋅⋅⋅H/H⋅⋅⋅N and H⋅⋅⋅H interactions in HGuaReO4 and HGuaTcO4. [ABSTRACT FROM AUTHOR]

Over the past decade, there has been a steady growth in demand for rare metals, with rhenium being one of the most highly demanded, but also one of the most expensive and difficult to obtain. The high demand for rhenium is due to its use as a key component of metallurgical alloys or as a component of catalysts used in the oil refining industry. The aggregate of facts causes profitability of processing of the rhenium-containing mineral resources, which also are the copper substandard concentrates obtained at processing of the Zhezkazgan sandstones. The study focuses on the processes of extraction of copper and sorption recovery of rhenium from solutions of ammonia leaching of copper substandard concentrates. Model solutions similar in the elemental composition to solutions of ammonia leaching solutions of copper substandard concentrates obtained during the processing of Zhezkazgan sandstones were used as an object of the study. The paper estimates extraction characteristics of copper recovery using LIX 84-I solution in kerosene, as well as sorption characteristics of the rhenium recovery process using the Purolite PPA100 anion exchanger. Based on the obtained characteristics the possibility of hydrometallurgical processing of ammonia leaching solutions of substandard copper-sulfide concentrates, and recovery of the obtained commercial products is shown.

A tripodal anion receptor has been obtained by an easy and fast single-reaction synthesis from commercial reagents. The three ligand arms-bearing aromatic groups able to form anion–π interactions define ligand clefts where large anions, such as perchlorate and perrhenate, are included. We report here the synthesis of the ligand, its acid/base properties in an aqueous solution which has been used to direct the synthesis of anion complexes, and the crystal structure of the free ligand and its anion complexes H3L(ClO4)2·H2O and H3L(ReO4)2.

A cationic pyridinium salt-based COF was synthesized and structurally characterized. PS-COF-1 showed the highest experimental BET surface area (2702.7 m2 g−1) reported to date for any cationic COF material. Endowed by unique structural features, PS-COF-1 showed outstanding performance for the selective adsorption of 99TcO 4 − (and ReO 4 −), suggesting great potential for 99TcO 4 − removal from nuclear wastes and in environmental remediation. [Display omitted] Ionic covalent organic framework (COF) materials with high specific surface areas and well-defined pore structures are desired for many applications yet seldom reported. Herein, we report a cationic pyridinium salt-based COF (PS-COF-1) with a Brunauer-Emmett-Teller (BET) surface area of 2703 m2 g−1, state-of-the-art for an ionic COF. Aided by its ordered pore structure, chemical stability, and radiation resistance, PS-COF-1 showed exceptional adsorption properties toward aqueous ReO 4 − (1262 mg g−1) and 99TcO 4 −. Its adsorption performance surpassed its corresponding amorphous analogue. Importantly, PS-COF-1 exhibited fast adsorption kinetics, high adsorption capacities, and selectivity for 99TcO 4 − and ReO 4 − at high ionic strengths, leading to the successful removal of 99TcO 4 − under conditions relevant to low-activity waste streams at US legacy Hanford nuclear sites. In addition, PS-COF-1 can rapidly decontaminate ReO 4 −/99TcO 4 − polluted potable water (∼10 ppb) to drinking water level (0 ppb, part per billion) within 10 min. Density functional theory (DFT) calculations revealed PS-COF-1 has a strong affinity for ReO 4 − and 99TcO 4 −, thereby favoring adsorption of these low charge density anions over other common anions (e.g., Cl−, NO 3 −, SO 4 2−, CO 3 2−). Our work demonstrates a novel cationic COF sorbent for selective radionuclide capture and legacy nuclear waste management. [ABSTRACT FROM AUTHOR]

The title hydrated salt, tris[hexaamminecobalt(III)] tetraoxidorhenate(VII) tetrakis[hexafluoridorhenate(IV)] hexahydrate, arose unexpectedly due to possible contamination of the K2ReF6 starting material with KReO4. It consists of octahedral [Co(NH3)6]3+ cation (Co1 site symmetry 1), tetrahedral [ReVIIO4]− anions (Re site symmetry 1) and octahedral [ReIVF6]2− anions (Re site symmetries 1and \overline{3}). The [ReF6]2− octahedral anions (mean Re—F = 1.834 Å), [Co(NH3)6]3+ octahedral cations (mean Co—N = 1.962 Å), and the [ReO4]− tetrahedral anion (mean Re—O = 1.719 Å) are slightly distorted. A network of N—H...F hydrogen bonds consolidates the structure. The crystal studied was refined as a two-component twin.

99Tc is a long-lived radionuclide present in large amounts as TcO4- anion in used nuclear fuel. Its removal from the waste stream is highly desirable because of its interference capability with actinide separation and its volatile nature during the nuclear waste vitrification process. Despite the progress achieved in the past few years, the design of anion-exchange materials with optimized Tc uptake property and improved stability under the extreme condition, is still a research goal beneficial for reducing the volume of secondary radioactive solid waste generated during the waste partitioning process. However, their design philosophy remains elusive, with challenges coming from charge repulsion, steric hindrance, and insufficient reactive sites within the materials. Herein, we present a design philosophy of cationic polymer network materials for TcO4- separation by systematic precursor screening and structure prediction. This affords an optimized material, SCU-CPN-2 (SCU=Soochow University), with extremely high positive charge density while maintaining high radiation resistance. SCU-CPN-2 exhibits a record high adsorption capacity (1,467 mg/g towards the surrogate ReO4-) compared to all anion-exchange materials reported up to date. In addition to ultrafast adsorption kinetics, SCU-CPN-2 has remarkable selectivity over nitrate and sulfate, and facile recyclability. [ABSTRACT FROM AUTHOR]

Pertechnetate ( 99 TcO 4 - ), a physiologically toxic radioactive anion, is of great concern due to its high mobility in environmental contamination remediation. Although the soluble oxyanion can be photoreduced to sparingly soluble TcO 2 · n H 2 O, its effective removal from a strongly acidic aqueous solution remains a challenge. Here, we found that low-crystalline nitrogen-doped titanium oxide (N-TiO 2 ) could effectively uptake perrhenate (ReO -1 ) could effectively uptake perrhenate (ReO 4 - , 10 mg L -1 , a nonradioactive surrogate for TcO 4 - ) with 50.8% during 360 min under simulated sunlight irradiation at pH 1.0, but P25 and anatase could not. The nitrogen active center formed by trace nitrogen doping in N-TiO 2 can promote the separation and transfer of photogenerated carriers. The positive valence band value of N-TiO 2 is slightly higher than those of P25 and anatase, which means that the photogenerated holes have a stronger oxidizability. These holes are involved in the formation of strong reducing • CO 2 - radicals from formic acid oxidation. The active radicals convert ReO 4 - to Re(VI), which is subsequently disproportionated to Re(IV) and Re(VII). Effective photocatalytic reduction/removal of Re(VII)/Tc(VII) is performed on the material, which may be considered a potential and convenient strategy for technetium decontamination and extraction in a strongly acidic aqueous solution.

Colorless single crystals of Sr[ReO4]2 were obtained from halide melts at 1123 K in open corundum crucibles. X‐ray diffraction revealed that Sr[ReO4]2 crystallizes in the monoclinic space group P21/n with the lattice parameters a = 627.31(4) pm, b = 1004.56(7) pm, c = 1271.25(9) pm and β = 97.118(3)° for Z = 4. The crystal structure contains a unique Sr2+‐cation site surrounded by eight crystallographically different oxygen atoms forming distorted bicapped trigonal prisms. All corners of these [SrO8]14– polyhedra (d(Sr–O) = 259–268 pm) are shared with tetrahedral meta‐perrhenate units [ReO4]– (d(Re–O) = 166–173 pm) formed from two crystallographically different Re7+ cations surrounded by four O2– anions each, building up the three‐dimensional mosaic‐like structure of Sr[ReO4]2. Single‐crystal Raman data confirm the presence of two different kinds of symmetry‐free meta‐perrhenate units [ReO4]– and match well with results known from literature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dicationic 1,2,4-selenodiazoles. • High solubility in water. • Precipitatation of pertechnetate or perrhenate. • Se⋯O and anion⋯anion interactions. Coupling between 2-pyridylselenyl chloride and various cyanopyridinium salts resulted in the formation of dicationic pyridinium-fused 1,2,4-selenodiazoles. Novel bicyclic heterocycles are highly soluble in water and readily precipitate pertechnetate and perrhenate anions from aqueous media. All the novel compounds were comprehensively characterized using 1H and 13C NMR techniques, ESI-MS, and X-ray diffraction analysis (for eight compounds). Theoretical calculations have shown the intricate nature of chalcogen bonding (ChBs) and anion-π interactions across a series of compounds, each exhibiting unique bonding patterns and interaction energies. Compounds [ 1 ]H(ReO 4) 2 , [ 2 ]H(ReO 4) 2 , [ 3 ](ReO 4), [ 2 ]H(TcO 4) 2 and [ 3 ](TcO 4) displayed complex assemblies, highlighting the role of ion-pair interactions, bifurcated ChBs, and directional mater bonds. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two ionic covalent organic frameworks are constructed via Zincke reaction by common solvothermal synthesis. • The stable efficient capture of ReO 4 − is achieved in acid and medium–low alkali conditions. • The iCOFs exhibit high adsorption capacity and fast exchange kinetic for ReO 4 −. • High concentration of competing ions has little effect on ReO 4 − capture efficiency. Rhenium is one of the highly scarce and important metals, and its capture is significant for resource recovery. As the latest generation ion exchange materials, ionic covalent organic frameworks (iCOFs) are desired for the acquisition of Re with large adsorption capacity, excellent selectivity, high stability and well-defined pore structures yet seldom reported. In this paper, two highly ordered iCOFs (TABD-COF and TAPB-COF) are successfully constructed via Zincke reaction by the common solvothermal synthesis. In particular, the morphology and crystallinity of iCOFs can be tuned by adjusting the reaction conditions and the structures of precursors. The analysis of PXRD, SEM, and TEM confirms that the two iCOFs exhibit highly ordered crystalline structures with multilayer stacking. TABD-COF and TAPB-COF perform relatively good thermally stability and high chemical stability in both acidic and basic conditions. Both of the two iCOFs show excellent adsorption performance for aqueous ReO 4 − (714 mg g−1 for TABD-COF , 633 mg g−1 for TAPB-COF) and fast ion exchange kinetics, in which 98 % of ReO 4 − are captured within 3 mins and 5 mins. Moreover, they also have outstanding trapping efficiency of ReO 4 − at excesses of competing anions. This work broadens the synthesis of iCOFs via Zincke reaction and provides two novel iCOFs for efficient capture of ReO 4 − in complex systems. [ABSTRACT FROM AUTHOR]

We reviewed the synthesis, structure, and properties of pyridine complexes of AgXO4 (X = Cl, Mn, and Re) compounds with various compositions ([AgPy2] XO4, [AgPy2XO4]·0.5Py, [AgPy4] XO4, and 4 [AgPy2XO4] [AgPy4] XO4). We also clarified the controversial information about the existence and composition of pyridine complexes of silver permanganate, used widely as mild and selective oxidants in organic chemistry. We discussed in detail the available structural and spectroscopic (IR, Raman, and UV) data and thermal behavior, including the existence and consequence of quasi-intramolecular reactions between the reducing ligand and anions containing oxygen.

Abstract Various types of polyoxometalates (POMs) have been synthesized since the 19th century, but their assortment has been mostly limited to Groups 5 and 6 metals. Herein, a new family of POMs composed of a carbon group element as the addenda atoms with two distinct phases, LnPbOClO4‐1 (Ln = Sm to Ho, Y) and LnPbOClO4‐2 (Ln = Er and Tm) is reported. Both structures are built from [Ln6O8] rare‐earth metal hexamers being incorporated in [Pb18O32]/[Pb12O24] polyplumbites, and unbound perchlorates as charge‐balancing anions. Impressively, YPbOClO4‐1 and ErPbOClO4‐2 exhibit exceptional uptake capacities (434.7 and 427.7 mg g−1) toward ReO4−, a chemical surrogate for the key radioactive fission product in the nuclear fuel cycle 99TcO4−, which are the highest values among all inorganic anion‐exchange materials reported until now. The sorption mechanism is clearly elucidated and visualized by single‐crystal‐to‐single‐crystal structural transformation from ErPbOClO4‐2 to a perrhenate‐containing complex ErPbOReO4, revealing a unique ReO4− uptake selectivity driven by specific interaction within Pb···O‐ReO3− bonds.

The ionic liquid 1-(2-methoxyethyl)-3-ethyl imidazolium perrhenate [C22O1IM][ReO4] was prepared in the laboratory firstly, and its structure was confirmed by 1H NMR and 13C NMR. The heat capacities were precisely measured in the temperature range from 78 to 392 K by means of a fully automated adiabatic calorimeter. For [C22O1IM][ReO4], the melting temperature, standard molar heat capacity, molar enthalpy, and molar entropy of solid–liquid phase transition were determined to be (211.826 ± 0.130) K, (142.31 ± 0.34) J K−1 mol−1, (14.382 ± 0.046) kJ mol−1, and (67.93 ± 0.22) J K−1 mol−1, respectively. And the experimental values of molar heat capacities were fitted to a polynomial equation using least square method in the appropriate temperature ranges. The thermodynamic functions (HT − H298.15) and (ST − S298.15) were also obtained from the heat capacity data in the experimental temperature range with an interval of 5 K. [ABSTRACT FROM AUTHOR]

Heat capacity for 1-hexyl-3-methyl imidazolium perrhenate ionic liquid [C6MIM][ReO4] in the temperature range from 79 to 396 K has been measured by a fully automated adiabatic calorimeter. For [C6MIM][ReO4], glass transition temperature, the melting temperature, standard molar heat capacity, enthalpy and entropy of solid–liquid phase transition were determined to be (202.164 ± 0.405) K, (226.198 ± 0.265) K, (480.702 ± 0.013) J K−1 mol−1, (15.665 ± 0.195) kJ mol−1 and (69.250 ± 0.780) J K−1 mol−1, respectively. In addition, the thermodynamic characteristics and solid–liquid phase change behavior of [C6MIM][ReO4] were compared with the ones of [C7MIM][ReO4] reported in the literature. The thermodynamic functions (HT− H298.15), (ST− S298.15) and (GT− G298.15), for the compound in the experimental temperature range were calculated. [ABSTRACT FROM AUTHOR]

The title hydrated salt, tris[hexaamminecobalt(III)] tetraoxidorhenate(VII) tetrakis[hexafluoridorhenate(IV)] hexahydrate, arose unexpectedly due to possible contamination of the K2ReF6 starting material with KReO4. It consists of octahedral [Co(NH3)6]3+ cation (Co1 site symmetry 1), tetrahedral [ReVIIO4]- anions (Re site symmetry 1) and octahedral [ReIVF6]2- anions (Re site symmetries 1and 3). The [ReF6]2- octahedral anions (mean Re--F =1.834 Å), [Co(NH3)6]3+ octahedral cations (mean Co--N = 1.962Å), and the [ReO4]- tetrahedral anion (mean Re--O = 1.719 Å) are slightly distorted. A network of N--H···F hydrogen bonds consolidates the structure. The crystal studied was refined as a two-component twin. [ABSTRACT FROM AUTHOR]

• Porous iron (pFe) had TcO 4 − removal capacity of 27.5 mg/g from groundwater. • pFe had a capacity of 23.9 mg/g for removing ReO 4 − from groundwater. • Tc species on pFe were 70–80% Tc(IV) and 20–30% TcO 4 − stabilized with Fe hydroxides. • Re species on pFe were 100% ReO 4 − stabilized with Fe hydroxides. Technetium-99 (99Tc) is a major contaminant at nuclear power plants and several US Department of Energy sites. Its most common aqueous species, pertechnetate (TcO 4 −), is very mobile in the environment, and currently there are no effective technologies for its sequestration. In this work, a porous iron (pFe) material was investigated for TcO 4 − and perrhenate (ReO 4 −) sequestration from artificial groundwater. The pFe was significantly more effective than granular iron for both TcO 4 − and ReO 4 - sequestration under oxic conditions. The Tc removal capacity was 27.5 mg Tc/g pFe at pH ˜6.8, while the Re removal capacity was 23.9 mg Re/g pFe at pH ˜10.6. Tc K-edge XANES and EXAFS analyses indicated that the removed Tc species was 70–80% Tc(IV) that was likely incorporated into Fe corrosion products (i.e., Fe(OOH), Fe 3 O 4) and 20–30% unreduced TcO 4 −. In contrast, the removed Re species was ReO 4 − only, without detectable Re(IV). In addition, the sequestered ReO 4 − was not extracted (<3%) by 0.1 M Na 2 SO 4 and 1 M KI solution, which indicated that ReO 4 − and by chemical analogy, unreduced TcO 4 −, was likely incorporated into Fe corrosion products. This inexpensive pFe material may be applied to the sequestration and stabilization of 99TcO 4 − from contaminated environments and nuclear waste streams. [ABSTRACT FROM AUTHOR]

Abstract A novel (CuII/ReVII)-heterobimetallic complex based on l -Arginine, namely trans -[Cu(l -Arg) 2 (ReO 4) 2 ] (CuLARe), was successfully synthesized and fully characterized using X-ray structure analysis as well as (IR/UV–vis) spectroscopy, molar conductivity and (TG/DTA) thermal methods. The crystal structure determination reveals that CuLARe has a non-symmetrical atomic arrangement and features striking helical chains of {[Cu(l -Arg) 2 (ReO 4) 2 ]} n , which are further assembled into a 3D-supramolecular network through multidirectional N(C, O)-H⋯O hydrogen bonding interactions. Analysis by Hirshfeld surface generation in combination with 2D-fingerprinting was also performed to elucidate the nature of the interactions and their contributions towards the crystal packing. Moreover, a comparative antioxidant screening of CuLARe with the free ligands as well as CuCl 2 has been investigated. The results emphasize that the complexation of ligands to the metal ions plays a crucial role in the improvement of the biochemical properties of CuLARe. Graphical abstract Image 1 Highlights • Synthesis, crystal structure determination and design of a novel (CuII/ReVII)-heterobimetallic complex based on l -Arginine. • Intermolecular interactions in the crystal packing were analyzed by 3D-Hirshfeld surfaces in combination with 2D-fingerprinting. • Spectroscopic properties, molar conductivity and thermal stability were studied. • Biochemical investigation exhibits a high scavenging capacity of free radicals and ferric reducing power of the complex. [ABSTRACT FROM AUTHOR]

Abstract Rhenium and molybdenum are valuable metals present in the earth's crust in very low concentration and are increasingly used in industry thanks to their multiple properties, but due to the harmful aspects of the production process, there is a need to develop systems of concentration or purification of salts of these elements. For this work a PEG/Na 2 MoO 4 aqueous two phase system (ATPS) was used for the partition of ReO 4 - anion. By using a central composite design, the effects of PEG concentration, sodium molybdate concentration, temperature, pH and their possible interaction on the partition coefficient were studied, also to estimate the optimal configuration of the factors that influence the process. At the same time, experimental density, sound velocity and isentropic compressibility were also obtained for top and bottom phases. The results showed that the optimal conditions for the partition of ReO 4 − anion using the ATPS formed by PEG and Na 2 MoO 4 were 14.7 wt% PEG 4000, 16.3 wt% Na 2 MoO 4 , 35 °C and pH 6. For these conditions, the partition coefficient (K) obtained was up to 17.8 ± 0.78. The order of factors with high significance on the partition coefficient was: Na 2 MoO 4 concentration > PEG concentration > temperature > pH > interaction between Na 2 MoO 4 and PEG concentrations; the effect of these parameters mainly is related with the speciation, salting-out effect and hydrophobicity. The influence of these factors on the density, and sound velocity of the top phase was minimal, unlike its influence on the properties of the bottom phase, not isentropic compressibility and effect of PEG and Na 2 MoO 4 concentrations on sound velocity. The evaluation of the partitioning behavior was made by experimental design, applying statistical regression analysis and analysis of variance (ANOVA). The statistical models for partition coefficient and for phase densities (and the other properties) as function of parameters with significant effects were obtained, and also a good correlation between experimental and correlated data was observed (R-Squared = 0.9379, ReO 4 − partition coefficient; 0.9882, bottom phase; and 0.9836 upper phase). This work is oriented to the possible application in stripping of a top phase provided for a co-extraction of rhenium and molybdenum by ATPS in acidic media or in solutions with high contend of Mo such as those provided by pressure oxidative leaching of molybdenite in basic media. Highlights • The Na 2 MoO 4 + PEG 4000 + H 2 O system was used for the ReO 4 − anion partitioning (K). • Central composite design was used to evaluate effects of factors on responses. • The factors considered: pH, temperature and concentrations of PEG 4000 and Na 2 MoO 4. • Salting-out effect of molybdenum anions was analyzed according to its speciation. • Best configuration: 14.7 wt% PEG 4000, 16.3 wt% Na 2 MoO 4 , 35 °C and pH 6; K = 17.8. [ABSTRACT FROM AUTHOR]

The effect of Bacillus spp. on Re(VII) and Se(IV) diffusion in compacted GMZ bentonite was investigated by a through-diffusion method. Bacillus spp. had no significance effect on the effective diffusion coefficient (De) and the accessible porosity (εacc) of Re(VII), whereas a decrease of De and an increase of distribution coefficient (Kd) were observed for Se(IV). Moreover, Archie's law and an exponential decay equation were employed to fit the De value of Re(VII) and Se(IV). [ABSTRACT FROM AUTHOR]

The biphasic catalytic epoxidation of cyclooctene using the ionic liquid (IL) 1,2‐dimethyl‐3‐octyl‐imidazolium perrhenate ([OMMIM]ReO4) as micellar catalyst and H2O2 as oxidant was investigated. Kinetic experiments were carried out in the intrinsic kinetic regime as proved by variation of stirring rate and temperature. Variation of catalyst concentration allowed for determination of the critical micellar concentration (CMC) of the catalytic IL. The effect of substrate concentrations on the reaction rate was also assessed. Based on the experiments, a kinetic model adapted from enzyme catalysis was proposed to account for the micellar reaction environment. The model takes into account the onset of micelle formation at the CMC. The application of the kinetic model illustrated the good agreement with the experimental data. The model will be applied to other micellar epoxidation reactions and for the design of an appropriate reaction setup in the future. Imidazolium perrhenate ionic liquids form micelles in aqueous H2O2 and thus act as micellar catalysts in epoxidation of cyclooctene. Key parameters such as the critical micelle concentration are determined from kinetic experiments in a batch reactor. The kinetic description is based on an adapted enzyme‐kinetic model, taking into account the micellar nature of the active species. [ABSTRACT FROM AUTHOR]

In this work, batch experiments were carried out to explore the sorption properties for perrhenate (ReO4−, a surrogate for TcO4−) by two types of commercial bifunctional anion-exchange resins (Purolite A530E and A532E). It is found that these two bifunctional anion-exchange resins could rapidly remove ReO4− from aqueous solution within 150 min and the maximum sorption capacity for ReO4− reached as high as 707 and 446 mg/g for Purolite A530E and A532E, respectively. The sorption properties were independent of pH over a wide range from 1 to 13. More importantly, both Purolite A530E and A532E exhibited excellent selectivity for the removal of ReO4− in the presence of large excess of NO3− and SO42−. Finally, the removal percentage of ReO4− by these two resins could be >90% and 80%, respectively, from the Hanford low-level waste melter off-gas scrubber simulant stream. Such high selectivity of Purolite A530E and A532E for the removal of ReO4− might be due to the presence of the long-chain group of –[N(Hexyl)3]+, which favored hydrophobic and large anions such as ReO4−/TcO4− rather than NO3−. [ABSTRACT FROM AUTHOR]

Low-temperature heat capacities of the 1-heptyl-3-methyl imidazolium perrhenate ionic liquids have been measured by a high-precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. In this report, the standard molar heat capacity was determined to be 679.438 J K−1 mol−1. The melting temperature at 207.873 ± 0.374 K has been discovered by the heat-capacity curve. The experimental values of molar heat capacities were fitted to two polynomial equations of heat capacities (Cp,m) by least square method. Meanwhile, the thermodynamic functions (HT − H298.15), (ST − S298.15), and (GT − G298.15) were also calculated in the temperature range from 298.15 to 400 K with the interval of 5 K. [ABSTRACT FROM AUTHOR]

Rhenium is a valuable metal in very low concentration and it is being increasingly used in industry due to its multiples properties, mainly in the aeronautics and oil industries. For this work, the PEG/CuSO 4 aqueous two phase system (ATPS) was used for the partition of perrhenate anion. For the partition tests the NH 4 ReO 4 salt was used. The effects of temperature, pH, salt concentration, PEG concentration and their interactions on the partition were analyzed by using experimental design 2 k . Moreover, density, kinematic viscosity and sound velocity were determined for the top and bottom phases. The optimal conditions obtained by the model for the perrhenate partition in the ATPS formed by PEG and CuSO 4 were 13.7% PEG 4000 ( w /w), 13% CuSO 4 (w/w) and 35 °C, obtaining a distribution coefficient, K ReO4- , of 7.72 ± 0.31. Also, an increase of K ReO4- with increasing PEG and CuSO 4 concentration was observed, i.e. their effects are significant on the perrhenate partition. On the other hand, the effects of temperature and pH do not have high significance on the partition. Of all the studied parameter, the pH had less significance on the partition. Thus, to simplify the statistical model the pH was not considered in the model. For both phases, only density is inversely proportional to pH. With exception of the sound velocity of bottom phase all properties for both phases are inversely proportional to temperature. Moreover, all properties are proportional with the PEG and CuSO 4 concentrations in both phases. The partitioning behavior was evaluated by an experimental design, applying statistical regression analysis and analysis of variance (ANOVA). The statistical model for distribution coefficient as function of the parameters with significant effects was obtained. A good agreement between experimental and correlated data was observed (R-Squared = 0.930). [ABSTRACT FROM AUTHOR]

In this work, batch experiments were carried out to explore the sorption properties for perrhenate (ReO4−,a surrogate for TcO4−) by two types of commercial bifunctional anion-exchange resins (Purolite A530E and A532E). It is found that these two bifunctional anion-exchange resins could rapidly remove ReO4− from aqueous solution within 150 min and the maximum sorption capacity for ReO4− reached as high as 707 and 446 mg/g for Purolite A530E and A532E, respectively. The sorption properties were independent of pH over a wide range from 1 to 13. More importantly, both Purolite A530E and A532E exhibited excellent selectivity for the removal of ReO4− in the presence of large excess of NO3− and SO42−. Finally, the removal percentage of ReO4− by these two resins could be>90 % and 80 %, respectively, from the Hanford low-level waste melter off-gas scrubber simulant stream. Such high selectivity of Purolite A530E and A532E for the removal of ReO4− might be due to the presence of the long-chaingroup of -[N(Hexyl)3]+, which favored hydrophobic and large anions such as ReO4−/TcO4− rather than NO3− [ABSTRACT FROM AUTHOR]

A series of N -alkylammonium perrhenate salts [N(R 1 ) 3 R 2 ] + [ReO 4 ] − with varying substituents R 1 and R 2 were synthesized and characterized and used as catalysts for the epoxidation of olefins. The effect of the substitution pattern on the catalytic activity was investigated. [ABSTRACT FROM AUTHOR]