Anion Binding Research Articles

Inorganic‐Rich Interphase Induced by Boric Oxide Solid Acid toward Long Cyclic Solid‐State Lithium‐Metal Batteries

AbstractSolid‐state electrolytes paired with lithium‐metal anodes is considered a next‐generation energy storage technology. However, the slow ionic transportation of the solid‐state electrolyte and the instability against the lithium‐metal anode impede their practical application. Here a cellulose separator modified with highly uniform boric oxide solid acid, contributing to a high transference number (0.75) and good ionic conductivity of 0.52 mS cm−1 due to the strengthened binding of the salt anions with this solid acid, is reported. Moreover, the boron ions with occupied interstitial sites can release free electrons to regulate the electrochemical dynamics of the electrolyte, in situ inducing the formation of Li2CO3/LiF‐rich heterostructured solid electrolyte interphase layer. The cellulose/B2O3‐based composite electrolyte paired with LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode and Li‐metal anode displays a specific capacity of 155 mAh g−1 with a capacity retention of 92% in 200 cycles. Additionally, this electrolyte paired with high‐mass‐loading NCM622 cathode (10 mg cm−2) in a pouch cell can be stably operated for 50 cycles with a capacity retention of over 90%.

Design and function of lignin/silk fibroin-based multilayer water purification membranes for dye adsorption

The treatment of dye wastewater poses a significant challenge to the sewage recycling industries. However, the reduction of secondary pollution resulting from the membrane residues, to maintain high performance, remains a considerable obstacle. A novel approach for the fabrication of multilayer nanofiber structures using a layer-by-layer electrostatic spinning technique with biological materials was reported in this study. Incorporating the chemical adsorption advantages of lignin nanofiber and the physical adsorption advantages of silk fibroin (SF) nanofiber enabled the full realization of excellent dye interception performance. A comparative analysis was conducted on the lignin derived from eucalyptus, pine, and straw to determine the most suitable option. Notably, eucalyptus lignin exhibited superior antimicrobial properties. The adsorption of crystal violet by eucalyptus lignin/SF membrane was consistent with the Freundlich isotherm model and the pseudo-second-order kinetic model, revealing a chemisorption mechanism involving Π-Π conjugation, hydrogen bonding, and the binding of anions and cations. The lignin/SF membrane exhibited a retention rate exceeding 99.5 % for crystal violet, methylene blue, and brilliant green dyes. Furthermore, it demonstrated efficacy in retaining heavy metal ions, including cadmium and copper. The original biomass material imparts the property of rapid degradation to a multilayer membrane that can be used as an effective and eco-friendly water purification material.

Towards Incorporation in Larger Architectures: A Polymeric Halogen Bond‐Based Iridium Sensor

AbstractThis study reports the synthesis and characterization of a "click‐able" iridium(III) complex as halogen bond‐based anion sensor. The functionalization is exemplarily demonstrated by the attachment of poly(ethylene glycol) azide via a "copper‐click"‐reaction. Subsequently, the polymeric XB donor complex is characterized in depth with 1H NMR spectroscopy, size exclusion chromatography, and MALDI‐ToF‐MS. Moreover, the anion binding capabilities are demonstrated with emission titrations revealing strong anion complexation. These findings emphasize the great potential of this approach to tune the complex's properties or include other functions such as cation complexation sites to exploit cooperative effects by using polymeric substituents on the iridium complex.

Binding, Sensing, And Transporting Anions with Pnictogen Bonds: The Case of Organoantimony Lewis Acids.

Motivated by the discovery of main group Lewis acids that could compete or possibly outperform the ubiquitous organoboranes, several groups, including ours, have engaged in the chemistry of Lewis acidic organoantimony compounds as new platforms for anion capture, sensing, and transport. Principal to this approach are the intrinsically elevated Lewis acidic properties of antimony, which greatly favor the addition of halide anions to this group 15 element. The introduction of organic substituents to the antimony center and its oxidation from the + III to the + V state provide for tunable Lewis acidity and a breadth of applications in supramolecular chemistry and catalysis. The performances of these antimony-based Lewis acids in the domain of anion sensing in aqueous media illustrate the favorable attributes of antimony as a central element. At the same time, recent advances in anion binding catalysis and anion transport across phospholipid membranes speak to the numerous opportunities that lie ahead in the chemistry of these unique main group compounds.

Synthesis of Cu (II) and Zn (II) Complexes of a Quinoline Based Flexible Amide Receptor as Fluorescent Probe for Dihydrogen Phosphate and Hydrogen Sulphate and Their Antibacterial Activity.

A novel 8-hydroxy quinoline-derived amide receptor, in conjunction with its Cu (II) and Zn (II) complexes, has been strategically developed to function as remarkably efficient fluorescent receptors with a distinct capability for anion sensing. The comprehensive characterization of the synthesized compounds were achieved through UV-Vis, IR, NMR, and HRMS spectroscopic techniques. Among the Cu (II) and Zn (II) complexes, the latter exhibits superior selectivity for anions, specifically dihydrogen phosphate and hydrogen sulfate, as their tetrabutylammonium salts in a 9:1 acetonitrile-water (v/v) mixture. The Cu (II) complex demonstrates enhanced anion binding compared to the amide ligand, albeit with reduced selectivity. Furthermore, the affinity was evaluated using the Benesi-Hildebrand plot. The binding constants and Limit of Detection (LOD) for both complexes were precisely quantified. The Job plot illustrates a clear 1:1 binding interaction between the metal complexes and the guest anions. Significantly, both metal-complex receptors display a broad spectrum of antibacterial activity, against both gram-positive and gram-negative bacteria. It is worth highlighting that the Zn (II) complexed receptor outperforms the Cu (II) complexed receptor, as evidenced by its considerably lower Minimum Inhibitory Concentration (MIC) value against both bacterial strains.

Anion Binding Poly (p-Aryltriazole) with High Affinity to Fluorine

Anion-binding polymer system based on click synthesized para (aryl-1,2,3-triazole) (PAT) functionality is described. The sensitivity and binding ability of the PAT system to halide ions such as F-, Cl-, Fand Br- which involve re-organisation of the aryl-triazole bonds, is explored using NMR and fluorescence spectroscopy. F-ion which induces the highest shift of the triazole C-H proton signal also shows the highest dynamic quenching of the PTA’s fluorescent intensity compared to Br- and Cl- ions.

Topological Design of Unprecedented Metal-Organic Frameworks Featuring Multiple Anion Functionalities and Hierarchical Porosity for Benchmark Acetylene Separation.

Separation of acetylene (C2 H2 ) from carbon dioxide (CO2 ) or ethylene (C2 H4 ) is industrially important but still challenging so far. Herein, we developed two novel robust metal organic frameworks AlFSIX-Cu-TPBDA (ZNU-8) with znv topology and SIFSIX-Cu-TPBDA (ZNU-9) with wly topology for efficient capture of C2 H2 from CO2 and C2 H4 . Both ZNU-8 and ZNU-9 feature multiple anion functionalities and hierarchical porosity. Notably, ZNU-9 with more anionic binding sites and three distinct cages displays both an extremely large C2 H2 capacity (7.94 mmol/g) and a high C2 H2 /CO2 (10.3) or C2 H2 /C2 H4 (11.6) selectivity. The calculated capacity of C2 H2 per anion (4.94 mol/mol at 1 bar) is the highest among all the anion pillared metal organic frameworks. Theoretical calculation indicated that the strong cooperative hydrogen bonds exist between acetylene and the pillared SiF6 2- anions in the confined cavity, which is further confirmed by in situ IR spectra. The practical separation performance was explicitly demonstrated by dynamic breakthrough experiments with equimolar C2 H2 /CO2 mixtures and 1/99 C2 H2 /C2 H4 mixtures under various conditions with excellent recyclability and benchmark productivity of pure C2 H2 (5.13 mmol/g) or C2 H4 (48.57 mmol/g).

Topological Design of Unprecedented Metal‐Organic Frameworks Featuring Multiple Anion Functionalities and Hierarchical Porosity for Benchmark Acetylene Separation

AbstractSeparation of acetylene (C2H2) from carbon dioxide (CO2) or ethylene (C2H4) is industrially important but still challenging so far. Herein, we developed two novel robust metal organic frameworks AlFSIX‐Cu‐TPBDA (ZNU‐8) with znv topology and SIFSIX‐Cu‐TPBDA (ZNU‐9) with wly topology for efficient capture of C2H2 from CO2 and C2H4. Both ZNU‐8 and ZNU‐9 feature multiple anion functionalities and hierarchical porosity. Notably, ZNU‐9 with more anionic binding sites and three distinct cages displays both an extremely large C2H2 capacity (7.94 mmol/g) and a high C2H2/CO2 (10.3) or C2H2/C2H4 (11.6) selectivity. The calculated capacity of C2H2 per anion (4.94 mol/mol at 1 bar) is the highest among all the anion pillared metal organic frameworks. Theoretical calculation indicated that the strong cooperative hydrogen bonds exist between acetylene and the pillared SiF62− anions in the confined cavity, which is further confirmed by in situ IR spectra. The practical separation performance was explicitly demonstrated by dynamic breakthrough experiments with equimolar C2H2/CO2 mixtures and 1/99 C2H2/C2H4 mixtures under various conditions with excellent recyclability and benchmark productivity of pure C2H2 (5.13 mmol/g) or C2H4 (48.57 mmol/g).

Chiral Molecular Cage with Tunable Stereoinversion Barriers.

The manipulation of chirality in molecular entities that rapidly interconvert between enantiomeric forms is challenging, particularly at the supramolecular level. Advances in controlling such dynamic stereochemical systems offer opportunities to understand chiral symmetry breaking and homochirality. Herein, we report the synthesis of a face-rotating tetrahedron (FRT), an organic molecular cage composed of tridurylborane facial units that undergo stereomutations between enantiomeric trefoil propeller-like conformations. After resolution, we show that the racemization barrier of the enantiopure FRT can be regulated in situ through the reversible binding of fluoride anions onto the tridurylborane moieties. Furthermore, the addition of an enantiopure phenylethanol to the FRT can effectively induce chirality of the molecular cage by preferentially binding to one of its enantiomeric conformers. This study presents a new paradigm for controlling dynamic chirality in supramolecular systems, which may have implications for asymmetric synthesis and dynamic stereochemistry.

Fatty Acid-Activated Proton Transport by Bisaryl Anion Transporters Depolarises Mitochondria and Reduces the Viability of MDA-MB-231 Breast Cancer Cells.

In respiring mitochondria, the proton gradient across the inner mitochondrial membrane is used to drive ATP production. Mitochondrial uncouplers, which are typically weak acid protonophores, can disrupt this process to induce mitochondrial dysfunction and apoptosis in cancer cells. We have shown that bisaryl urea-based anion transporters can also mediate mitochondrial uncoupling through a novel fatty acid-activated proton transport mechanism, where the bisaryl urea promotes the transbilayer movement of deprotonated fatty acids and proton transport. In this paper, we investigated the impact of replacing the urea group with squaramide, amide and diurea anion binding motifs. Bisaryl squaramides were found to depolarise mitochondria and reduce MDA-MB-231 breast cancer cell viability to similar extents as their urea counterpart. Bisaryl amides and diureas were less active and required higher concentrations to produce these effects. For all scaffolds, the substitution of the bisaryl rings with lipophilic electron-withdrawing groups was required for activity. An investigation of the proton transport mechanism in vesicles showed that active compounds participate in fatty acid-activated proton transport, except for a squaramide analogue, which was sufficiently acidic to act as a classical protonophore and transport protons in the absence of free fatty acids.

Solution Studies of a Water-Stable, Trivalent Antimony Pnictogen Bonding Anion Receptor with High Binding Affinities for CN-, OCN-, and OAc.

The solution phase anion binding behavior of a water-stable bidentate pnictogen bond donor was studied. A modest change in the visible absorption spectrum allowed for the determination of the binding constants. High binding constants were observed with cyanide, cyanate, and acetate, and these were corroborated with density functional theory (DFT) calculations. The receptor could be recovered free from the anion following treatment with methyl triflate, confirming that it remains intact. The tight binding of cyanide and water stability were exploited to use this system as a supramolecular catalyst in a phase-transfer Strecker reaction, further demonstrating the utility of pnictogen bonding as a tool in noncovalent catalysis.

High Density Poly(ionic liquid)s with Spatial Structure Regulation for Efficient Carbon Dioxide Cycloaddition

AbstractThe synthesis of cyclic carbonate from CO2 and epoxide is one of the valid routes in line with atomic economy to achieve CO2 conversion. Combining the advantages of high activity and easy separation for heterogeneous catalytic reaction system, a series of heterogeneous catalysts poly(ionic liquid)s with high ionic density (HDPILs) were designed and synthesized. Looser structures and high ionic density were obtained by using muti‐center ionic liquids with different number of substituents as cross‐linking agents. Ply[PhSVIM]Br, the copolymerized HDPILs with six substituents on the benzene ring was optimal. The catalyst exhibited excellent catalytic performance for CO2 cycloaddition with 98 % conversion and 99 % selectivity under optimal conditions. These HDPILs have comparable catalytic activity to homogeneous catalysts and convenient product separability. Particularly, combining XPS and DFT, a structural performance relationship was revealed, the multi‐center ionic liquids used instead of the traditional crosslinking agent as the polymeric backbone can contribute to the reduction of the anion and cation binding energy (BE) and freeing of Br−, which leads to efficient catalytic activity. This study provides a novel strategy for developing a highly efficient catalysts for CO2 conversion to high value products.

Strong halide anion binding within the cavity of a conformation-adaptive phenazine-based Pd2L4 cage

Strong halide anion binding within the cavity of a conformation-adaptive phenazine-based Pd2L4 cage

Carbazole diester strapped calix[4]pyrrole: Synthesis, anion binding and self-assembly based on ion pair recognition

A new carbazole strapped calix[4]pyrrole 1 has been synthesized and ion binding properties was investigated using 1H NMR, isothermal titration calorimetry and single crystal X-ray diffraction analyses. Compared to the parent octamethyl calix[4]pyrrole 2, receptor 1 showed enhanced binding towards halide anions. Solid state structural analysis revealed that receptor 1 is capable of binding various halide salts showing different binding modes depending on the bound ion pairs. Interestingly, complexes of tetrabutyammonium (TBA+), tetraethylammonium (TEA+) and tetramethylammonium (TMA+) salts of chloride anion displayed three distinctly different binding geometries in the solid state. As a result, the linear supramolecular polymers seen in the crystal lattices are also dramatically different for these three chloride complexes of 1. Combination of 1H NMR and solid state studies revealed that binding of anion in one condition do not translates to another completely. Receptor 1 also found to form 1/1 complexes with CsCl, CsBr and CsI salts and 1D coordination polymer chains are stabilized in the solid state. Overall, construction of four different 1D linear chains are described for chloride anion based on ion pair recognition. In addition, the solid state structure of ion pair complex with CsI salt is unprecedented in the calix[4]pyrrole chemistry. Moreover, under solid-to-liquid extraction condition, receptor 1 is able to solubilise CsF and CsCl ion pairs in chloroform in which these salts are otherwise insoluble.

Carbazole Integrated Tetrakis-(1H-pyrrole-2-carbaldehyde): A Highly Selective Fluorescent Probe for HP2O73.

A new carbazole-coupled tetrakis-(1H-pyrrole-2-carbaldehyde) anion receptor 1 has been designed and synthesized. Anion binding studies in organic media using fluorescence and UV-vis spectroscopy revealed that receptor 1 is capable of sensing HP2O73- with high selectivity. Addition of HP2O73- to THF solution of 1 resulted in the emergence of a new broad band at longer wavelength along with quenching of the original emission band forming a ratiometric response. Based on dynamic light scattering (DLS) experiment and fluorescence lifetime measurement, we propose that the emergence of new emission band in the presence of HP2O73- ion is due to the aggregation-induced excimer formation.

An Amphiphilic Peptide Carrier for HCl Transport.

Single molecules that co-transport cations as well as anions across lipid membranes are few despite their high biological utility. The elegant yet simple lipidomimetic peptide design herein enables efficient HCl transport without the use of any external additives for proton transport. The carboxylic acids in the dipeptide scaffold provide a handle to append two long hydrophobic tails and also provides a polar hydrophilic carboxylate group. The peptide central unit also provides NH sites for anion-binding. Protonation of the carboxylate group coupled with the weak halide binding of the terminal NH group results in HCl transport with transport rates of H+ > Cl‾. The lipid-like structure also facilitates seamless membrane integration and flipping of the molecule. The biocompatibility, design simplicity and potential pH regulation of these molecules open up several avenues for their therapeutic use.

Dynamic allostery in thrombin-a review.

Thrombin is a serine protease that catalyzes a large number of different reactions including proteolytic cleave of fibrinogen to make the fibrin clot (procoagulant activity), of the protease activated receptors (for cell signaling) and of protein C generating activated protein C (anticoagulant activity). Thrombin has an effector binding site called the anion binding exosite 1 that is allosterically coupled to the active site. In this review, we survey results from thermodynamic characterization of the allosteric coupling as well as hydrogen-deuterium exchange mass spectrometry to reveal which parts of the thrombin structure are changed upon effector binding and/or mutagenesis, and finally NMR spectroscopy to characterize the different timescales of motions elicited by the effectors. We also relate the experimental work to computational network analysis of the thrombin-thrombomodulin complex.

Agarose‐based hydrogels with tunable, charge‐selective permeability properties

AbstractPhysiologically, a hallmark of biological hydrogels is their ability to selectively trap diffusing molecules and particles. And indeed, there is now increasing interest in using selective hydrogel barriers for applications in biomedicine and medical engineering. However, when employing synthetic polymers to create hydrogels with selective permeabilities, controlling the type and strength of the ensuing filtration process is difficult. Here, we generate hybrid gels with adjustable selectivity profiles by mixing a series of (bio‐)macromolecules with agarose. Depending on the type and concentration of the incorporated macromolecules, those hybrid gels achieve a selective retardation of the diffusive translocation of either positively or negatively charged dextrans at both, acidic and neutral pH. Furthermore, we demonstrate three strategies that provide hydrogels with sequestered patches of both, cationic and anionic binding sites, thus creating symmetric charge (i.e., electrostatic bandpass) filters which still allow neutral molecules to pass. Moreover, such agarose matrices offer a high level of versatility as their permeability profiles can be tailored at will by integrating macromolecules with desired physico‐chemical properties. Thus, those agarose‐based hybrid gels may serve as a powerful platform to engineer adjustable and versatile materials for a broad range of future applications in the field of biomedical engineering.

Hybrid zipper-like chitosan-carboxymethyl cellulose-ferric adsorbents for tunable anion adsorption

Composite materials (CCFe and CGCFe) were prepared from carboxymethyl cellulose, chitosan, glutaraldehyde, and iron III species. The composite materials were characterized by FTIR, TGA, ICP-OES and SEM studies that provided evidence of cross-linking between chitosan and glutaraldehyde, along with variable iron doping and morphology of the composites. The equilibrium uptake study indicates that CGCFe surpassed the adsorption capacity of CCFe, where greater uptake was noted at lower versus higher temperatures (283 – 303 K). The monolayer adsorption capacity (Qm; mg g−1) of CGCFe for 2-naphthoxy acetic acid (S6) was 263 mg/g and 484 mg/g at alkaline and acidic pH conditions, according to the Sips and Langmuir isotherm models. The composite materials show limited discrimination of OSPW naphthenate components. Regeneration studies revealed that CGCFe retained 95% of its adsorption capacity after 5 cycles via a “zippering effect” in the presence of saline water. The enhanced regeneration and zipper-like structural transition of CGCFe represents a unique application of saline responsive supramolecular function driven by changes in ionic strength. This study advances the design of modular polysaccharide adsorbents according to the insight on the role of Fe (III) species, cross-linking effects, and biopolymer structure that relate to anion binding properties in aqueous solution.

Alkali Metal Halide Ion-Pair Binding in Conformationally Dynamic Halogen Bonding Heteroditopic [2]Rotaxanes.

A series of heteroditopic halogen bonding (XB) [2]rotaxanes were prepared via a combination of passive and active metal template-directed strategies. The ability of the [2]rotaxanes to bind alkali metal halide ion-pairs was investigated by extensive 1H NMR titration studies, wherein detailed analysis of cation, anion and ion-pair affinity measurements indicate dramatic positive cooperative enhancements in halide anion association upon either Na+ or K+ pre-complexation. We demonstrate that careful consideration of multiple, parallel and competing binding equilibria is essential when interpreting observed 1H NMR spectral changes in ion-pair receptor systems, especially those which exhibit dynamic behaviour. Importantly, in comparison to XB [2]catenane analogues, these neutral XB heteroditopic [2]rotaxane host systems demonstrated that despite their relatively weaker cation and anion binding abilities, they exhibit a notably higher level of positive cooperativity for alkali metal halide ion-pair binding, highlighting the role of greater co-conformational adaptive behaviour in mechanically-bonded hosts for the purposes of charged species recognition.