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In recent years, European Union member states have hastened energy policy deliberations to address supply and sustainability concerns, placing a significant emphasis on nuclear energy as a means to achieve decarbonization goals. However, despite its significant role in power generation, nuclear energy faces significant challenges linked to fuel reprocessing and waste disposal, that hinder its broader expansion. In this context, the separation of technetium represents a concerning issue. Indeed, technetium's catalytic activity can impede the extraction of uranium, neptunium, and plutonium, affecting waste reprocessing efficiency. Additionally, the stable form of technetium in aerobic conditions, pertechnetate (TcO4−), poses risks of groundwater contamination due to its mobility and solubility. Hence, sensing and separation of TcO4− is imperative for both nuclear fuel processing and minimising radioactive contamination in the environment. However, the binding of TcO4− and its separation from contaminated solutions present challenges due to the acidic (or basic) waste components and the high ionic strength in real matrices. Supramolecular chemists have addressed these issues by designing receptors inspired by molecular recognition principles. This article explores recent advancements and future directions in TcO4− sensing and separation (using extraction and sorption) with a focus on molecular hosts. Metal‐organic receptors will also be discussed. [ABSTRACT FROM AUTHOR]

In recent years, European Union member states have hastened energy policy deliberations to address supply and sustainability concerns, placing a significant emphasis on nuclear energy as a means to achieve decarbonization goals. However, despite its significant role in power generation, nuclear energy faces significant challenges linked to fuel reprocessing and waste disposal, that hinder its broader expansion. In this context, the separation of technetium represents a concerning issue. Indeed, technetium's catalytic activity can impede the extraction of uranium, neptunium, and plutonium, affecting waste reprocessing efficiency. Additionally, the stable form of technetium in aerobic conditions, pertechnetate (TcO4−), poses risks of groundwater contamination due to its mobility and solubility. Hence, sensing and separation of TcO4− is imperative for both nuclear fuel processing and minimising radioactive contamination in the environment. However, the binding of TcO4− and its separation from contaminated solutions present challenges due to the acidic (or basic) waste components and the high ionic strength in real matrices. Supramolecular chemists have addressed these issues by designing receptors inspired by molecular recognition principles. This article explores recent advancements and future directions in TcO4− sensing and separation (using extraction and sorption) with a focus on molecular hosts. Metal‐organic receptors will also be discussed. [ABSTRACT FROM AUTHOR]

Organic cages are three-dimensional polycyclic compounds of great interest in the scientific community due to their unique features, which generally include simple synthesis based on the dynamic covalent chemistry strategies, structural tunability and high selectivity. In this feature article, we present the advances over the last ten years in the application of organic cages as chemosensors or components in chemosensing devices for the determination of analytes (pollutants, analytes of biological interest) in complex aqueous media including wine, fruit juice, urine. Details on the recent applications of organic cages as selective (back-)extractants or masking agents for potential applications in relevant separation processes, such as the plutonium and uranium recovery by extraction, are also provided. Over the last ten years, organic cages with permanent porosity in the liquid and solid states have been highly appreciated as porous materials able to discriminate molecules of different sizes. These features, combined with good solvent processability and film-forming tendency, have proved useful in the fabrication of membranes for gas separation, solvent nanofiltration and water remediation processes. An overview of the recent applications of organic cages in membrane separation technologies is given. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a novel film‐forming organic cage and of its smaller analogue are here described. While the small cage produced single crystals suitable for X‐ray diffraction studies, the large one was isolated as a dense film. Due to its remarkable film‐forming properties, this latter cage could be solution processed into transparent thin‐layer films and mechanically stable dense self‐standing membranes of controllable thickness. Thanks to these peculiar features, the membranes were also successfully tested for gas permeation, reporting a behavior similar to that found with stiff glassy polymers such as polymers of intrinsic microporosity or polyimides. Given the growing interest in the development of molecular‐based membranes, for example for separation technologies and functional coatings, the properties of this organic cage were investigated by thorough analysis of their structural, thermal, mechanical and gas transport properties, and by detailed atomistic simulations. [ABSTRACT FROM AUTHOR]

Correction for 'Recent applications of organic cages in sensing and separation processes in solution' by Sonia La Cognata et al., Chem. Commun., 2023, 59, 13668–13678, https://doi.org/10.1039/D3CC04522F. [ABSTRACT FROM AUTHOR]

Two novel imide/imine‐based organic cages have been prepared and studied as materials for the selective separation of CO2 from N2 and CH4 under vacuum swing adsorption conditions. Gas adsorption on the new compounds showed selectivity for CO2 over N2 and CH4. The cages were also tested as fillers in mixed‐matrix membranes for gas separation. Dense and robust membranes were obtained by loading the cages in either Matrimid® or PEEK‐WC polymers. Improved gas‐transport properties and selectivity for CO2 were achieved compared to the neat polymer membranes. [ABSTRACT FROM AUTHOR]

Considering the wide interest in (benz)imidazolium-based drugs, we here report our study on a benzimidazolium-based organic cage as potential antimicrobial and antifungal agent. Cytotoxicity studies on a human derived cell line, SH-SY5Y, showed that the cage is not cytotoxic at all at the investigated concentrations. Anion binding studies demonstrated that the cage can bind anions (chloride and nitrate, in particular) both in organic solvent and 20%v D2O/CD3CN mixture. The cage was also tested as anionophore, showing a weak but measurable transport of chloride and nitrate across LUVs vesicles. Nonetheless, the compounds have antimicrobial activity towards Staphylococcus aureus (Gram-positive bacteria). This is probably the first organic cage studied as anionophore and antimicrobial agent. [ABSTRACT FROM AUTHOR]

A chiral cage is proposed as an effective chiroptical sensor for perrhenate (surrogate for 99TcO4−) in water, fruit juice and artificial urine media. The key mechanism for the chiroptical sensing resides in the change of dihedral angle of the binaphthyl unit and H-bonds with the guest, resulting in ample changes of the CD signal as a consequence of the binding event. [ABSTRACT FROM AUTHOR]

The extraction of technetium, present in nitric acid medium as pertechnetate anion, is an issue in solvent extraction processes used to recover uranium and plutonium. In the present study, a complexing agent is added in the aqueous nitric acid solution to bind selectively the pertechnetate anion and prevent its extraction into the organic phase or to back extract it in the aqueous phase. Several azacryptands with the addition of hydrophilic groups were synthesized to improve the solubility of the previously studied cage molecule in nitric acid medium. Solvent extraction tests reveal that all the synthesized ligands have a similar complexation strength towards pertechnetate and are able to maintain this anion in the aqueous phase (0.5 M HNO3). These ligands are able to overcome the Hofmeister bias and selectively bind technetium in nitric acid solution. The azacryptand concentration can be increased by a factor of three in the liquid–liquid extraction conditions compared to our previous work. Coordination studies using microcalorimetry, Single Crystal X-Ray Diffraction (SC-XRD), infrared and Raman spectroscopies show the formation of an inclusion complex with hydrogen bonds stabilizing the oxo-anion within the cavity. This solubility improvement is promising for the introduction of this kind of macrocyclic azacryptands in a solvent extraction process. [ABSTRACT FROM AUTHOR]

The research on systems able to perform controllable motions under external stimuli arises great interest in the scientific community. Over the years, a library of innovative devices has been produced, classified in different categories according to the molecular or supramolecular level of motion. This minireview aims to highlight some representative studies, in which organic cages are used as building blocks for mechanically interlocked molecules, and in which intramolecular motions are triggered by external input. However, the application of organic cages in the construction of molecular machines is hardly achieved. A good compromise must actually be reached, between flexibility and rigidity of the cage's framework for an effective control of the intra‐ and/or intermolecular motion in the final mechanical device. Our final goal is to stimulate researchers′ curiosity towards cage‐like molecules, so that they take on the challenge of converting a cage into a molecular machine. [ABSTRACT FROM AUTHOR]

Cover Feature: Gas Permeation through Mechanically Resistant Self-Standing Membranes of a Neat Amorphous Organic Cage (Chem. Eur. J. 56/2023) Keywords: gas transport; membranes; molecular materials; organic cages; thin films EN gas transport membranes molecular materials organic cages thin films 1 1 1 10/12/23 20231009 NES 231009 B Gas separation b : A novel organic cage with excellent film-forming tendencies was processed into transparent, mechanically robust, self-standing membranes of controllable thickness. Gas transport, membranes, molecular materials, organic cages, thin films. [Extracted from the article]

In this work, we combined smartphone sensing with the indicator displacement approach for the determination of trans,trans-muconic acid (i.e.tt-MA), a benzene biomarker, in urine. Dicopper(ii) azacryptate was employed as the receptor. The good match of tt-MA with the receptor cavity was suggested by DFT calculations, and confirmed experimentally by UV-vis titrations in buffered aqueous solutions. The binding constant was determined through fluorimetric titrations using the indicator displacement approach. This method also confirmed the high affinity of the azacryptate for tt-MA in artificial and spiked urine samples. A portable device was then obtained by adsorption of the chemosensing ensemble on silica gel using ELISA-like plastic wells as the support. Indicator displacement was detected and quantified by exposing the microplate to a UV-lamp (366 nm) and recording the RGB values with a smartphone. A good correlation was found between the R index values and urinary tt-MA in the occupational concentration range. [ABSTRACT FROM AUTHOR]

Membrane-based processes are taking a more and more prominent position in the search for sustainable and energy-efficient gas separation applications. It is known that the separation performance of pure polymers may significantly be improved by the dispersion of suitable filler materials in the polymer matrix, to produce so-called mixed matrix membranes. In the present work, four different organic cages were dispersed in the poly(ether ether ketone) with cardo group, PEEK-WC. The m-xylyl imine and furanyl imine-based fillers yielded mechanically robust and selective films after silicone coating. Instead, poor dispersion of p-xylyl imine and diphenyl imine cages did not allow the formation of selective films. The H2, He, O2, N2, CH4, and CO2 pure gas permeability of the neat polymer and the MMMs were measured, and the effect of filler was compared with the maximum limits expected for infinitely permeable and impermeable fillers, according to the Maxwell model. Time lag measurements allowed the calculation of the diffusion coefficient and demonstrated that 20 wt % of furanyl imine cage strongly increased the diffusion coefficient of the bulkier gases and decreased the diffusion selectivity, whereas the m-xylyl imine cage slightly increased the diffusion coefficient and improved the size-selectivity. The performance and properties of the membranes were discussed in relation to their composition and morphology. [ABSTRACT FROM AUTHOR]

In this work, we report the synthesis of a new bis(tris(2-aminoethyl)amine) azacryptand L with triphenyl spacers. The binding properties of its dicopper complex for aromatic dicarboxylate anions (as TBA salts) were investigated, with the aim to obtain potential building blocks for supramolecular structures like rotaxanes and pseudo-rotaxanes. As expected, UV-Vis and emission studies of [Cu2L]4+ in water/acetonitrile mixture (pH = 7) showed a high affinity for biphenyl-4,4′-dicarboxylate (dfc2−), with a binding constant of 5.46 log units, due to the best match of the anion bite with the Cu(II)-Cu(II) distance in the cage's cavity. Compared to other similar bistren cages, the difference of the affinity of [Cu2L]4+ for the tested anions was not so pronounced: conformational changes of L seem to promote a good interaction with both long (e.g., dfc2−) and short anions (e.g., terephthalate). The good affinity of [Cu2L]4+ for these dicarboxylates, together with hydrophobic interactions within the cage's cavity, may promote the self-assembly of a stable 1:1 complex in water mixture. These results represent a good starting point for the application of these molecular systems as building units for the design of new supramolecular architectures based on non-covalent interactions, which could be of interest in all fields related to supramolecular devices. [ABSTRACT FROM AUTHOR]

In recent years, European Union member states have hastened energy policy deliberations to address supply and sustainability concerns, placing a significant emphasis on nuclear energy as a means to achieve decarbonization goals. However, despite its significant role in power generation, nuclear energy faces significant challenges linked to fuel reprocessing and waste disposal, that hinder its broader expansion. In this context, the separation of technetium represents a concerning issue. Indeed, technetium's catalytic activity can impede the extraction of uranium, neptunium, and plutonium, affecting waste reprocessing efficiency. Additionally, the stable form of technetium in aerobic conditions, pertechnetate (TcO 4 - ), poses risks of groundwater contamination due to its mobility and solubility. Hence, sensing and separation of TcO 4 - is imperative for both nuclear fuel processing and minimising radioactive contamination in the environment. However, the binding of TcO 4 - and its separation from contaminated solutions present challenges due to the acidic (or basic) waste components and the high ionic strength in real matrices. Supramolecular chemists have addressed these issues by designing receptors inspired by molecular recognition principles. This article explores recent advancements and future directions in TcO 4 - sensing and separation (using extraction and sorption) with a focus on molecular hosts. Metal-organic receptors will also be discussed., (© 2024 Wiley-VCH GmbH.)

Two novel imide/imine-based organic cages have been prepared and studied as materials for the selective separation of CO 2 from N 2 and CH 4 under vacuum swing adsorption conditions. Gas adsorption on the new compounds showed selectivity for CO 2 over N 2 and CH 4 . The cages were also tested as fillers in mixed-matrix membranes for gas separation. Dense and robust membranes were obtained by loading the cages in either Matrimid® or PEEK-WC polymers. Improved gas-transport properties and selectivity for CO 2 were achieved compared to the neat polymer membranes., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The extraction of technetium, present in nitric acid medium as pertechnetate anion, is an issue in solvent extraction processes used to recover uranium and plutonium. In the present study, a complexing agent is added in the aqueous nitric acid solution to bind selectively the pertechnetate anion and prevent its extraction into the organic phase or to back extract it in the aqueous phase. Several azacryptands with the addition of hydrophilic groups were synthesized to improve the solubility of the previously studied cage molecule in nitric acid medium. Solvent extraction tests reveal that all the synthesized ligands have a similar complexation strength towards pertechnetate and are able to maintain this anion in the aqueous phase (0.5 M HNO3). These ligands are able to overcome the Hofmeister bias and selectively bind technetium in nitric acid solution. The azacryptand concentration can be increased by a factor of three in the liquid-liquid extraction conditions compared to our previous work. Coordination studies using microcalorimetry, Single Crystal X-Ray Diffraction (SC-XRD), infrared and Raman spectroscopies show the formation of an inclusion complex with hydrogen bonds stabilizing the oxo-anion within the cavity. This solubility improvement is promising for the introduction of this kind of macrocyclic azacryptands in a solvent extraction process.

We report the investigation of dicopper(II) bistren cryptate, containing naphthyl spacers between the tren subunits, as a receptor for polycarboxylates in neutral aqueous solution. An indicator displacement assay for dicarboxylates was also developed by mixing the azacryptate with the fluorescent indicator 5-carboxyfluorescein in a 50:1 molar ratio. Fluorimetric studies showed a significant restoration of fluorophore emission upon addition of fumarate anions followed by succinate and isophthalate. The introduction of hexyl chains on the naphthalene groups created a novel hydrophobic cage; the corresponding dicopper complex was investigated as an extractant for dicarboxylates from neutral water into dichloromethane. The liquid-liquid extraction of succinate-as a model anion-was successfully achieved by exploiting the high affinity of this anionic guest for the azacryptate cavity. Extraction was monitored through the changes in the UV-visible spectrum of the dicopper complex in dichloromethane and by measuring the residual concentration of succinate in the aqueous phase by HPLC-UV. The successful extraction was also confirmed by 1 H-NMR spectroscopy. Considering the relevance of polycarboxylates in biochemistry and in the environmental field, e.g., as waste products of industrial processes, our results open new perspectives for research in all contexts where recognition, sensing, or extraction of polycarboxylates is required., Competing Interests: The authors declare no competing financial interest.