First 24-Membered Macrocyclic 1,10-Phenanthroline-2,9-Diamides-An Efficient Switch from Acidic to Alkaline Extraction of f-Elements

A reaction of acyl chlorides derived from 1,10-phenanthroline-2,9-dicarboxylic acids with piperazine allows the preparation of the corresponding 24-membered macrocycles in good yield. The structural and spectral properties of these new macrocyclic ligands were thoroughly investigated, revealing promising coordination properties towards f-elements (Am, Eu). It was shown that the prepared ligands can be used for selective extraction of Am(III) from alkaline-carbonate media in presence of Eu(III) with an SF_Am/Eu up to 40. Their extraction efficiency is higher than calixarene-type extraction of the Am(III) and Eu(III) pair. Composition of macrocycle-metal complex with Eu(III) was investigated by luminescence and UV-vis spectroscopy. The possibility of such ligands to form complexes of L:Eu = 1:2 stoichiometry is revealed.

A pillar[5]arene-based covalent organic framework with pre-encoded selective host-guest recognition

It is highly desirable to maintain both permanent accessible pores and selective molecular recognition capability of macrocyclic cavitands in the solid state. Integration of well-defined discrete macrocyclic hosts into ordered porous polymeric frameworks (e.g., covalent organic frameworks, COFs) represents a promising strategy to transform many supramolecular chemistry concepts and principles well established in the solution phase into the solid state, which can enable a broad range of practical applications, such as high-efficiency molecular separation, heterogeneous catalysis, and pollution remediation. However, it is still a challenging task to construct macrocycle-embedded COFs. In this work, a novel pillar[5]arene-derived (P5) hetero-porous COF, denoted as P5-COF, was rationally designed and synthesized. Featuring the unique backbone structure, P5-COF exhibited selective adsorption of C2H2 over C2H4 and C2H6, as well as significantly enhanced host-guest binding interaction with paraquat, in comparison with the pillar[5]arene-free COF analog, Model-COF. The present work established a new strategy for developing COFs with customizable molecular recognition/separation properties through the bottom-up "pre-porous macrocycle to porous framework" design.

Endowing 2,6-bis-triazolyl-pyridine of poor extraction with superior efficiency for actinide/lanthanide separation at high acidity by anchoring to a macrocyclic scaffold

Exploring nitrogen-containing extractants for recovering hazardous minor actinides that are workable in solutions of high acidity has been a challenge in nuclear waste treatment. Herein, we report our findings that 2,6-bis-triazolyl-pyridine (PyTri), which is ineffective as a hydrophobic ligand for minor actinide separation, turns into an excellent extractant that exhibits unexpectedly high efficiency and selectivity (SF_Am/Eu = 172, 1 M HNO₃) when attaching to pillar[5]arene platform. Surprisingly, the distribution ratio of Am(III) (D_Am) is 4300 times higher than that of the acyclic PyTri ligand. The solvent extraction performance of this pillar[5]arene-achored PyTri not only far exceeds the best known pillar[5]arene ligands reported to date, but also stays comparable to other reported outstanding extractants. Slope analysis indicates that each P[5]A-PyTri can bind two metal ions, which is further corroborated by spectroscopic characterizations. Thermodynamic studies imply that the extraction process is exothermic and spontaneous in nature. Complexation investigation via EXAFS technique and DFT calculations strongly suggest that each Eu(III) ion is coordinated to three PyTri arms through a nine-coordination mode. This work provides a N-donor extractant that can operate at high acidity for minor actinide partitioning and implicates a promising approach for transforming poor extractants into superior ones.

Highly efficient plutonium scavenging by an extraction chromatography resin containing a tetraaza-12-crown-4 ligand tethered with four diglycolamide pendent arms

An efficient extraction chromatography resin, containing tetraaza-12-crown-4 functionalized with four diglycolamide moieties, was evaluated for the separation of plutonium. This chromatography resin yielded very large distribution coefficients for Pu⁴⁺ (>10⁵) in 0.5 - 6 M HNO₃ feed solutions. Various physicochemical properties such as sorption kinetics, Pu⁴⁺ sorption mechanism, and its sorption capacity were investigated. The sorption kinetics, following a pseudo-second-order model, showed that about 10 minutes of equilibration was sufficient for >99.9% sorption of Pu⁴⁺. The sorption of Pu⁴⁺ on the resin followed the Langmuir monolayer model, which was confirmed by a theoretical calculation based on the kinetic model. The Pu⁴⁺ sorption on the resin was driven by a large exothermic enthalpy change (ΔH = -31.4±2.2 kJ/mol) and a positive entropy change (ΔS = 224±15 J/mol/L). The resin could sorb a maximum of 12.1±0.8 mg of Pu per gram of resin, which is equivalent to 1:2 metal/ligand complex on the resin. The Pu⁴⁺ from the resin phase was completely stripped with 0.5 M oxalic acid. A possible application of this resin for the separation / pre-concentration of Pu⁴⁺ was successfully demonstrated in the column mode.

A review of the alpha radiolysis of extractants for actinide lanthanide separation in spent nuclear fuel reprocessing

Radiation stability is one of the key properties to enable the efficient use of extractants in spent nuclear fuel with high radioactivity. The last several decades have witnessed a rapid progress in the radiation chemistry of extractants. A variety of studies and reviews pertinent to the radiation stability of extractants have been published. However, a thorough summary for the alpha radiolysis results of extractants is not available. In this review, we survey the development of alpha radiolysis of extractants for actinide lanthanide separation and compare their radiolysis behaviors induced by alpha particles and gamma rays. The discussion of alpha radiolysis of extractants is divided into three parts according to the functional groups of extractants (i.e., phosphine oxide, amide and bis-triazinyl bipyridines). Given the importance of radiation source to carry out alpha irradiation experiment, we first give a brief introduction to three practicable alpha radiation sources including alpha emitting isotopes, helium ion beam and reactor. We hope this review will provide useful information and unleash a broad palette of opportunities for researchers interested in radiation chemistry.

Highly efficient actinide(III)/lanthanide(III) separation by novel pillar[5]arene-based picolinamide ligands: A study on synthesis, solvent extraction and complexation

Selective extraction of highly radiotoxic actinides(III) is an important and challenging task in nuclear wastewater treatment. Many proposed ligands containing S or P atoms have drawbacks including high reagent consumption and possible secondary pollution after incineration. The present work reports five novel pillar[5]arene-based extractants that are anchored with picolinamide substituents of different electronic nature by varying spacer. These ligands reveal highly efficient separation of actinides(III) over lanthanides(III). Specifically, almost all of these ligands could extract Am(III) over Eu(III) selectively at around pH 3.0 (SF_Am/Eu>11) with fast extraction kinetics. Variation of the pyridine nitrogen basicity via changing para-substitution leads to an increase in the distribution ratios by a factor of over 300 times for Am(III) with an electron-withdrawing group compared to those with an electron donating group. Investigation of complexation mechanism by slope analysis, NMR, IR, EXAFS, and DFT techniques indicates that each ligand binds two metal ions by pyridine nitrogen and amide oxygen. Finally, these ligands do not show obvious decrease in both extraction and separation ability after being exposed to 250 kGy absorbed gamma radiation. These results demonstrate the potential application of pillar[5]arene-picolinamides for actinide(III) separation.

Highly efficient uptake of neptunium from acidic feeds using two solid phase extraction resins containing diglycolamide-functionalized calix[4]arene ligands

Two solid phase extraction resins (SPER) were prepared by impregnating solutions of two diglycolamide-functionalized calix[4]arenes in 10% isodecanol in n-dodecane into Chromosorb W, as the stationary phase. While SPER-I contained n-propyl functionalized calix[4]arene, SPER-II contained the calix[4]arene with isopentyl groups at the carboxamide nitrogen atoms. The SPERs were characterized by SEM, TGA, FTIR, etc. and were used for the batch uptake of neptunium(IV) from nitric acid feed solutions. While the uptake of Np(IV) was extremely high with SPER-I (K_d: 47,544 at 3 M nitric acid, ca. 8% extractant loading), SPER-II displayed a significantly lower extraction efficiency (K_d: 13,724 under identical conditions) as indicated by the batch uptake studies. Sorption isotherm studies were carried out which indicated good fitting to the Langmuir model suggesting uptake conforming to monolayer sorption. Fitting to the D-R isotherm model conformed to a chemisorption model. Column studies were also carried out and the elution profiles, obtained with solutions of oxalic acid and nitric acid indicated very sharp peaks suggesting that the column can be used for the separation of Np(IV) from acidic radioactive feeds.

Sequestration of tetravalent neptunium from acidic feeds using diglycolamide-functionalized dendrimers in a room temperature ionic liquid: extraction, spectroscopic and electrochemical studies

Extraction of Np(iv) was studied using RTIL containing two poly(propyleneimine) based dendrimer ligands from HNO3 solutions. Studies of the extracted complexes were also carried out by Vis-NIR and cyclic voltammetry.

Highly efficient diglycolamide-functionalized dendrimers for the sequestration of tetravalent actinides: solvent extraction and theoretical studies

Two DGA-functionalized dendrimers were used for the extraction and bonding computations of tetravalent actinide ions Np⁴⁺ and Pu⁴⁺ from HNO₃ medium.

Metal-Free White Light-Emitting Fluorescent Material Based on Simple Pillar[5]arene-tripodal Amide System and Theoretical Insights on Its Assembly and Fluorescent Properties

The booming of host-guest assembly-based supramolecular chemistry provides abundant ways to construct functional systems and materials. Attracted by the important application prospect of white light emission and aggregation-induced emission (AIE) materials, herein, we report an efficient way for fabricating metal-free white light-emitting AIE materials through the supramolecular assembly of simple organic compounds: methoxyl pillar[5]arene (MP5) and tri-(pyridine-4-ylamido)benzene (TAP). By host-guest assembly, MP5 and TAP formed a supramolecular polymer (MP5-T); meanwhile, the MP5-T xerogel powder emitted white light at CIE coordinates (0.29 and 0.29). The supramolecular assembly and white light-emitting mechanisms were carefully investigated by experiments as well as quantum chemical calculations including density functional theory (DFT), reduced density gradient, electrostatic surface potential, independent gradient model, and frontier molecular orbital (highest-occupied molecular orbital-lowest-unoccupied molecular orbital) analyses. Interestingly, according to the experiments and calculations, the supramolecular assembly is critical in the white light-emitting phenomenon. Moreover, in this work, the quantum chemical calculations could not only support experimental phenomena but also provide deep understanding and visualized presentation of the assembly and emission mechanism. In addition, the obtained MP5-T solid powder could serve as a novel and easy means to make material for white light-emitting devices.

Selective Separation and Coordination of Europium(III) and Americium(III) by Bisdiglycolamide Ligands: Solvent Extraction, Spectroscopy, and DFT Calculations

Diglycolamide-based ligands have recently received increased attention due to their outstanding affinity for trivalent actinides and lanthanides. The structure optimization of the ligands, however, still remains a hot topic to achieve better extraction performance. In this work, we prepare and investigate three multidentate diglycolamide ligands for the selective separation of Eu(III) over Am(III) from a nitric acid solution to explore the effect on the extraction of alkyl groups on the nitrogen atoms in the center of the BisDGA ligands. The introduction of ethyl or isopropyl groups on the central nitrogen atoms greatly increased the distribution ratios of trivalent metal ions and enhanced the separation factor of Eu(III) over Am(III). The complexation behaviors of Eu(III) and Am(III) ions were studied by slope analyses, electrospray ionization mass spectrometry (ESI-MS), and extended X-ray absorption fine structure (EXAFS) spectroscopy. The results indicated that the trivalent metal ions were extracted as 1:2 and 1:3 complexes for all three BisDGA ligands during the extraction. Density functional theory (DFT) calculations verified the relevant experimental conclusion that the selectivity of THEE-BisDGA for Eu(III) is better than that for Am(III). The metal-DGA bonds in the ML₃(NO₃)₃ complexes seem to be stronger than those in ML₂(NO₃)₃ complexes.

Radiolytic stability of pillar[5]arene-based diglycolamides

Radiolytic stability of pillar[5]arene-based diglycolamides (P5DGAs) against gamma irradiation up to 1000 kGy adsorbed dose was studied. The results reveal the increase of radiation damage degree on P5DGAs with dose. The radiolysis products of P5DGAs including the gaseous and solid products were fully characterized by 1H NMR, HR-ESI-MS, GC, and HPLC techniques. It was found that the main radiolytic gas products of P5DGAs under argon are H2, N2, CO and gaseous hydrocarbons. The solid degradation products contain phenolic hydroxyl groups and secondary amine groups. In addition, solvent extraction toward Eu(III) was performed with P5DGAs, in which about 50% decrease on extraction efficiency was observed for irradiated P5DGAs with dose of 1000 kGy in comparison with the non-irradiated one. A radiolytic degradation pathway was also proposed based on the above results. This is the first time to investigate the radiolytic stability of neat P5DGAs and P5DGAs in molecular diluent in detail and provides useful information for further application of P5DGAs in practical applications for spent fuel reprocessing.

Light-controlled switchable complexation by a non-photoresponsive hydrogen-bonded amide macrocycle

A light controlled switchable host–guest system based on a non-photoresponsive H-bonded macrocycle and pyridinium salts was developed using a photoacid.

Effect of ionic liquid on the extraction of uranium with pillar[5]arene-based phosphine oxide from nitric acid solutions

The extraction of U(VI) from aqueous nitric acid solutions with pillar[5]arene-based phosphine oxide (L) and [C8mim][NTf2] ionic liquid dissolved in 1,2-dichloroethane was explored. A great positive impact in this system was observed. The effect of IL concentration in the organic phase and HNO3 concentration in the aqueous phase is considered. The distribution ratios of U(VI) were significantly enhanced upon adding a small amount of ionic liquid as compared with organic diluent. The extraction system was also examined for its ability towards extraction of lanthanides and Th4+. The results revealed higher separation factors towards UO2 2+ over Th4+ in the presence of ionic liquid compared with organic diluent. Other factors such as C8mim+ and NTf2 − have also been considered. This extraction system has shorter equilibrium time as compared with in IL diluent. Stripping experiments showed almost quantitative back extraction of UO2 2+ within two stages. With high selectivity towards UO2 2+ and efficient back extraction, this new POP5A-ionic liquid-organic diluent system shows promise for future application of uranium recovery.

An azine-containing bispillar[5]arene-based multi-stimuli responsive supramolecular pseudopolyrotaxane gel for effective adsorption of rhodamine B

An azine-containing bispillar[5]arene was designed and synthesized by the reaction of aldehyde functionalized-pillar[5]arene and hydrazine. Then, a novel bispillar[5]arene-based supramolecular pseudopolyrotaxane has been successfully prepared via host-guest interaction. Interestingly, by taking advantage of the host-guest interactions, π-π stacking interactions and hydrogen bonding interactions, the multi-stimuli-responsive gel-sol phase transitions of such a supramolecular pseudopolyrotaxane gel were successfully realized under different stimuli, such as acid, temperature, concentration, and competitive guests. Moreover, this supramolecular system could effectively adsorb dye molecule rhodamine B. It is worth noting that this supramolecular pseudopolyrotaxane gel prepared in cyclohexanol solution (BP5·G·C) could be used as an adsorbent material for adsorbing rhodamine B with adsorption efficiency of 98.4%. Meanwhile, the adsorption efficiency was 97.6% for supramolecular pseudopolyrotaxane gel prepared in DMSO-H2O (v : v, 8 : 2) binary solution (BP5·G·D), also indicating the superior adsorption effect of BP5·G·D toward the dye molecule rhodamine B.

Highly Efficient N-Pivot Tripodal Diglycolamide Ligands for Trivalent f-Cations: Synthesis, Extraction, Spectroscopy, and Density Functional Theory Studies

A series of four N-pivot tripodal diglycolamide (DGA) ligands, where three DGA moieties are attached to the central N atom via spacers of different lengths and with varying alkyl substituents on the amidic nitrogen of DGA (L_I-L_IV), were studied for their extraction and complexation ability toward trivalent lanthanide/actinide ions, including solvent extraction, complexation using spectrophotometric titrations, and luminescence spectroscopic studies. Introduction of a methyl group on the amidic nitrogen atom gives rise to a 400 fold increase of the Eu distribution ( D) value [L_III (NMe) vs L_II (NH)] at 1 M HNO₃. Enlargement of the spacer length between the pivotal N atom and the DGA moieties with one carbon atom results in a 14 times higher D_Eu value [L_I (C3) vs L_II (C2)]. Slope analyses showed that Eu³⁺ was extracted as a bis-solvated species with all four ligands. The compositions of the Eu³⁺/L complexes were further confirmed by spectroscopic measurements, its formation constants following the order: L_III > L_IV > L_I > L_II. Luminescence spectroscopy and electrospray ionization mass spectrometry revealed that all four ligands form [Eu(L)₂(NO₃)₃] complexes. Density functional theory and thermodynamic parameters corroborated the existence of [Eu(L)₂(NO₃)₃] complexes.

Discovery of non-classical complex models between a cationic water-soluble pillar[6]arene and naphthalenesulfonate derivatives and their self-assembling behaviors

Molecular recognition based on cationic water-soluble pillar[n]arenes shows considerable advantages in their application in biological and environmental systems, such as excellent anion-binding ability and antimicrobial properties. Unique complex models are discovered in this work where a cationic water-soluble pillar[6]arene binds with disodium 1,5-naphthalenedisulfonate and disodium 2,6-naphthalenedisulfonate at the ratio of 1 : 2, which is proven by results from nuclear magnetic resonance spectroscopy, isothermal titration calorimetry, fluorescence spectroscopy experiments and transmission electron microscopy.

Supramolecular nanotheranostics based on pillarenes

With the rapid development of supramolecular chemistry and nanomaterials, supramolecular nanotheranostics has attracted remarkable attention owing to the advantages compared with conventional medicine. Supramolecular architectures relying on non-covalent interactions possess reversible and stimuli-responsive features; endowing supramolecular nanotheranostics based on supramolecular assemblies great potentials for the fabrication of integrated novel nanomedicines and controlled drug delivery systems. In particular, pillarenes, as a relatively new class of synthetic macrocycles, are important candidates in the construction of supramolecular therapeutic systems due to their excellent features such as rigid and symmetric structures, facile substitution, and unique host-guest properties. This review summarizes the development of pillarene-based supramolecular nanotheranostics for applications in biological mimicking, virus inhibition, cancer therapy, and diagnosis, which contains the following two major parts: (a) pillarene-based hybrid supramolecular nanotheranostics upon hybridizing with porous materials such as mesoporous silica nanoparticles, metal-organic frameworks, metal nanoparticles, and other inorganic materials; (b) pillarene-based organic supramolecular therapeutic systems that include supramolecular amphiphilic systems, artificial channels, and prodrugs based on host-guest complexes. Finally, perspectives on how pillarene-based supramolecular nanotheranostics will advance the field of pharmaceuticals and therapeutics are given.

Radiation stability of phosphine oxide functionalized pillar[5]arenes

The radiation stability of three phosphine oxide functionalized pillar[5]arenes (POP5A) was studied by an electron accelerator with dose up to 5 MGy in air at room temperature. The structures of both irradiated and unirradiated pillar[5]arenes samples were comparatively characterized by Micro-FTIR, NMR, UV-vis, ESI-HRMS and HPLC techniques. The results revealed different degrees of radiation damage at different doses for POP5A, and the degradation products are mainly composed of organic species containing hydroxyl groups and carbonyl groups. The possible radiolytic degradation pathway was proposed. In addition, extraction of uranyl ion with irradiated POP5A samples was examined. The distribution ratio of uranyl ion was found to increase at low radiation dose and decrease until 3000 kGy. This is the first time that the irradiation stability of pillar[5]arenes derivative extractants has been studied in detail and it provides reliable data support for further application of pillar[5]arenes extractants in practical applications.

Insights into the synthesis of pillar[5]arene and its conversion into pillar[6]arene

The synthesis of pillar[5]arenes from p-dialkoxybenzene and formaldehyde in the presence of iron(iii) chloride and tetramethylammonium chloride under mild reaction conditions was investigated in detail.

Pillararenes as macrocyclic hosts: a rising star in metal ion separation

Pillararenes are macrocyclic oligomers of alkoxybenzene akin to calixarenes but tethered at the 2,5-positions via methylene bridges. Benefiting from their unique pillar-shaped architecture favorable for diverse functionalization and versatile host-guest properties, pillararenes decorated with chelating groups worked excellently as supporting platforms to construct extractants or adsorbents for metal ion separation. This feature article provides a detailed summary of pillararenes in Ln/An separation by liquid-liquid extraction and heavy metal separation by solid-liquid extraction. The preorganization effect of the rigid pillararene framework has a profound impact on the extraction of metal ions, and a unique extraction mechanism is observed when employing ionic liquids as solvents. The rich host-guest chemistry of pillararenes enables construction of a wide variety of supramolecular materials as metal ion adsorbents. We also discuss the differences between pillararenes and several well-known macrocycles, with a focus on the metal-ligand coordination and its influencing factors. We hope this review will provide useful information and unleash new opportunities in this field.

Evaluation of two aza-crown ether-based multiple diglycolamide-containing ligands for complexation with the tetravalent actinide ions Np4+ and Pu4+: extraction and DFT studies

Two multiple diglycolamide (DGA)-containing extractants where the DGA arms are tethered to the nitrogen atoms of two aza-crown ether scaffolds, a 9-membered aza-crown ether containing three ‘N’ atoms (L_I) and a 12-membered aza-crown ether containing four ‘N’ atoms (L_II), were evaluated for the extraction of the tetravalent actinide ions Np⁴⁺ and Pu⁴⁺. The tripodal ligand with three DGA arms (L_I) was relatively inferior in its metal ion extraction properties as compared to the tetrapodal ligand with four DGA arms (L_II) and Pu⁴⁺ ion was better extracted than Np⁴⁺ ion with both the ligands. A solvation extraction mechanism, where species of the type ML(NO₃)₄ are extracted, was found to be operative for both the ligands involving both the tetravalent actinide ions. While the extraction of the metal ions increased with the feed nitric acid concentration up to 4 M, a sharp decline in the extraction was seen after that. Quantitative extraction (>99%) of the actinide ions was observed with L_II from 4 M HNO₃, suggesting the possible application of the ligands for actinide partitioning of high-level waste. The structure and the composition of the complexes were optimized by DFT computations.

Two multiple diglycolamide (DGA)-containing aza-crown ether ether-based extractants were evaluated for the extraction of the tetravalent actinide ions Np⁴⁺ and Pu⁴⁺.

Supramolecular ligands for the extraction of lanthanide and actinide ions

A selection of supramolecular ligands designed to extract f-elements.

Effect of an alkyl substituent and spacer length in benzene-centered tripodal diglycolamides on the sequestration of minor actinides

Three benzene-centered tripodal diglycolamide (Bz-T-DGA) ligands, where diglycolamide (DGA) moieties are tethered to the central benzene ring through a methylene spacer and having either a hydrogen atom (LI) or an isopentyl group (LII) attached to the N-atom, and DGA moieties attached via an ethylene spacer and having an isopentyl group attached to the N-atom (LIII), were studied for their complexation and extraction abilities towards trivalent actinides and lanthanides. The distribution ratio of Am(iii) and Eu(iii) with 1 mmol L-1 ligand in 5% iso-decanol/n-dodecane followed the order: LII > LIII > LI. The substitution of the H atom with the isopentyl group on the N-atom of the DGA moieties resulted in two orders of magnitude enhancement in the extraction ability of the ligand. On the other hand, increase in the spacer length between the benzene ring and the DGA moieties resulted in several fold reduction in the extraction ability of the ligand. Spectroscopic studies with Eu3+ ions in acetonitrile also confirmed the metal/ligand complex formation constant in the order: LII > LIII > LI. Luminescence decay lifetimes of Eu3+/ligand complexes confirmed the absence of water molecules and that all the primary coordination sites of the metal ion are occupied by the ligands.

Liquid-liquid extraction and facilitated transport of f-elements using an N-pivot tripodal ligand

Diglycolamide (DGA)-functionalized tripodal ligands offer the required nine-coordinated complex for effective binding to a trivalent lanthanide/actinide ion. A N-pivot tripodal ligand (TREN-DGA) containing three DGA pendant arms was evaluated for the extraction and supported liquid membrane transport studies using PTFE flat sheets. Solvent extraction studies indicated preferential extraction of 1:1 (M:L) species, while the metal ion extraction increased with increasing HNO₃ concentration conforming to a solvated species extraction. Flat sheet-supported liquid membrane studies, carried out using 4.0 × 10^-3 M TREN-DGA in 95% n-dodecane + 5% iso-decanol indicated faster mass transport for Eu³⁺ ion as compared to Am³⁺ ion. The determined transport parameters indicated slow diffusion of the M-TREN-DGA (M = Am or Eu) complex being the rate-determining step. The transport of lanthanides and actinides followed the trend: Eu³⁺ > Am^3+∼ Pu⁴⁺ >> UO₂²⁺ and Am can be selectively separated from a mixture of U and Pu by oxidizing the latter to its +6 oxidation state. The liquid membrane stability was not encouraging and was deteriorating the transport efficiency with time, which was attributed to carrier loss into the aqueous phases.

Unusual binding selectivity with non-selective homoditopic pillar[5]arene oxime: serendipitous discovery of a unique approach to heterobinuclear metalation in solution

A heterobinuclear complexation strategy on homoditopic pillar[5]arene was developed by using a pillar[5]arene with two rims decorated with benzaldehyde oximes. The unique selective recognition process was found to result from vesicular formation based on a controllable self-assembly, leading to binding of thorium(iv) only onto one rim, with the other rim being unoccupied for subsequent complexation of a second different metal ion.

A diglycolamide-functionalized TREN-based dendrimer with a ‘crab-like’ grip for the complexation of actinides and lanthanides

TREN-G1-DGA, a multiple DGA ligand, was synthesized and evaluated for the extraction of actinides and fission product ions.