Counterions Research Articles

Long-Range Proton Channels Constructed via Hierarchical Peptide Self-Assembly.

The quest to understand and mimic proton translocation mechanisms in natural channels has driven the development of peptide-based artificial channels facilitating efficient proton transport across nanometric membranes. It is demonstrated here that hierarchical peptide self-assembly can form micrometers-long proton nanochannels. The fourfold symmetrical peptide design leverages intermolecular aromatic interactions to align self-assembled cyclic peptide nanotubes, creating hydrophilic nanochannels between them. Titratable amino acid sidechains are positioned adjacent to each other within the channels, enabling the formation of hydrogen-bonded chains upon hydration, and facilitating efficient proton transport. Moreover, these chains are enriched with protons and water molecules by interacting with immobile counter ions introduced into the channels, increasing proton flow density and rate. This system maintains proton transfer rates closely resembling those in natural protein channels over micrometer distances. The functional behavior of these inherently recyclable and biocompatible systems opens the door for their exploitation in diverse applications in energy storage and conversion, biomedicine, and bioelectronics.

Conformational Changes and Coordination Stability of Flexible Tripeptides During Ni(II)-mediated Self-assembly.

The rational design of artificial supramolecular structures with specific properties and functions hinges the comprehensive understanding of the coordination and noncovalent interactions driving self-assembly. Herein, the self-assembly of supramolecular systems through octahedral coordination between Ni(II) ions and a flexible tripeptide was theoretically investigated using quantum chemical calculations. These calculations utilized the B3LYP functional with the polarizable continuum model. Our results indicate that tridentate sites have a greater propensity for coordination, and that the presence of chloride anions and conformational shifts enhance bidentate and monodentate coordination. Insights into the effect of counter anions on the stability of octahedral coordination and the prerequisites for self-assembly were gained by determining the stable conformation and potential reaction pathways of the tripeptide before and after adding chloride anions through an efficient automated conformational search. The formation of intramolecular hydrogen bonding interactions during the conformational changes was also studied using model calculations. Possible processes for initial self-assembly of tripeptide were proposed. This study enhances the fundamental understanding of the conformational behavior of building blocks during supramolecular formation and advance the potential for constructing future bioinspired complexes.

Synthesis and Structural Characterization of Carbazole‐Tailored Luminescent Triarylmethyl Radical and its Stable Cation

AbstractThe development of novel luminescent radicals, characterized by their unique doublet emission, endows a significant challenge. In this study, we reported the synthesis of a luminescent neutral radical, BCzAnM‐R, tailored by two carbazolyl groups and an anthryl group to achieve a nonalternant structure. It exhibited near‐infrared emission with a peak at 1020 nm in toluene. Interestingly, its corresponding cation, BCzAnM‐C, was synthesized through an unconventional SnCl2‐mediated reduction‐aromatization‐oxidation reaction in one‐pot and gram‐scale. The cation demonstrated remarkable stability for up to weeks in ambient conditions and facilitated the silica‐gel chromatography isolation as an organic salt with SnCl3− as the counter ion. The carbazolyl groups effectively modulate molecular structures, photophysical properties, and stabilities. Notably, BCzAnM‐R represents the first luminescent triarylmethyl radical with two carbazolyl groups directly attached to the central carbon.

Solar light driven photochromic membranes with viologen additives in PVDF/PVP matrix

This study explores the synthesis and characterization of photochromic Polyvinylidenefluoride/Polyvinylpyrrolidone (PVDF/PVP)-based membranes, prepared through an in situ thiol-ene click reaction by incorporating viologen derivatives with different counter ions. Viologens are well-known for their light-sensitive properties and ability to change color, making them useful in various optoelectronic applications. The membranes developed in this study exhibit significant improvements in their interactions with light as a result of improved morphology and enhanced ionic conductivity (≈4 × 10−4 S cm–1) with higher porosity (Ra: 11.26–33.76 nm) compared to conventionally prepared membranes. These membranes show the ability to block almost all ultraviolet (UV) and a 90% of visible light after irradiation. Thanks to these properties, the membranes undergo visible color changes when exposed to sunlight, making them suitable for photochromic and thermochromic applications. The findings of this study could contribute to the development of innovative coating materials that enhance energy efficiency, potentially being applied to buildings, automotive windows, and other surfaces.

Single organic electrode for multi-system dual-ion symmetric batteries

The large void space of organic electrodes endows themselves with the capability to store different counter ions without size concern. In this work, a small-molecule organic bipolar electrode called diquinoxalino[2,3-a:2’,3’-c]phenazine-2,6,10-tris(phenoxazine) (DQPZ-3PXZ) is designed. Based on its robust solid structure by the π conjugation of diquinoxalino[2,3-a:2’,3’-c]phenazine (DQPZ) and phenoxazine (PXZ), DQPZ-3PXZ can indiscriminately and stably host 5 counter ions with different charge and size (Li+, Na+, K+, PF6− and FSI−). In Li/Na/K-based half cells, DQPZ-3PXZ can deliver the peak discharge capacities of 257/243/253 mAh g−1cathode and peak energy densities of 609/530/572 Wh kg−1cathode, respectively. The Li/Na/K-based dual-ion symmetric batteries can be constructed, which can be activated through the 1st charge process and show the stable discharge capacities of 85/66/72 mAh g−1cathode and energy densities of 59/50/52 Wh kg−1total mass, all running for more than 15000 cycles with nearly 100% capacity retention.

Coordination Modes of Ortho-Substituted Benzoates Towards Divalent Copper Centres in the Presence of Diimines

The coordination modes of several ortho-substituted benzoates towards the copper(II) centre are investigated. The coordination environment of the metal ion includes nitrogen atoms from 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) and occasionally oxygen atoms from coordinated water, ethanol molecules, or nitrate ions. The compounds are investigated by a variety of spectroscopic methods and by single-crystal X-ray diffraction. Although the reaction scheme involved equimolar amounts of the reactants, cationic dinuclear compounds with a metal/benzoate/diimine ratio of 2:3:2 have been realized, cationic in nature regardless of the counter anion used. Furthermore, the carboxylate moieties display a range of twisting relative to the orientation of the benzene ring to which they are attached.

Guanidinium‐Based Covalent Organic Framework Membranes for Superior Mono‐ and Divalent Cations Separation

Biological membranes exhibit extraordinary efficiency in processing ion permeability and selectivity. However, creating artificial membranes for an ideal ion separation is still challenging due to the subtle distinctions in valence and size among different ions. In the realm of biological recognition, the ultimate selectivity of ion channels is considered to stem from the specific binding interactions and appropriate charge density. Designing artificial membranes to achieve similar performance not only helps the understanding of complex ion transport in bioprocesses but also facilitates critical industrial separations. Inspiring by the remarkable performance in biological systems, a guanidinium‐based covalent organic framework membrane is designed, which exhibits an excellent capability to recognize mono‐/divalent cations, achieving K+/Mg2+ selectivity up to 202 in a mixed salt solution. Furthermore, the membrane displays rapid ion transport owing to the uniform sub‐2 nm channels. The experimental results and molecular dynamics simulations illustrate that the charge‐assisted hydrogen bonding sites and the Cl− counter ions within 1D channels play critical roles in cations sieving. Specifically, divalent ions passing through the positively charged channels need to overcome higher energy barriers than monovalent ions. These findings offer promising avenues for the development of advanced multifunctional membranes for efficient ion separation and sustainable water‐related separations.

A d10-Cd Cluster Containing Sandwich-Type Arsenotungstate Exhibiting Fluorescent Recognition of Carcinogenic Dye in Methanol.

A d10-Cd cluster containing sandwich-type arsenotungstate [C3H12N2]6[Cd4Cl2(B-α-AsW9O34)2] was synthesized and its structure characterized through elemental analyses, X-ray powder diffraction (XRPD), IR spectroscopy, X-ray photoelectron spectroscopy (XPS), and single-crystal X-ray diffraction. The X-ray analysis revealed that the molecular unit of the compound consists of a captivating tetra-Cd-substituted sandwich-type polyoxoanion, accompanied by six elegantly protonated 1,2-diaminopropane as counter ions. The further novelty of the tetranuclear cadmium cluster lies in its occupied chlorine atom sites. This makes it highly susceptible to coordinate reactions with nitrogen on polycyclic aromatic hydrocarbons, thereby exhibiting different fluorescent signals that facilitate the identification and detection of these carcinogenic substances in methanol.

The effects of counter ion on CO2 capture performance of amino acid salt solutions for direct air capture applications

Direct CO2 capture from the atmosphere has received growing attention driven by the imperative of achieving global net-zero emission targets. Amino acid salt solutions are promising candidates for liquid-based direct air capture processes. Utilised as a neutralized salt by reacting initially with hydroxides, it has been speculated that their performance may vary with the type of counter ion present in the solution. This work investigates the influence of counter ions, potassium, sodium, and lithium, of amino acid salt solutions on the physical properties, the CO2 absorption capacities, and the CO2 absorption kinetics under atmospheric CO2 concentration levels. The potassium-containing amino acid solutions exhibited significantly lower viscosities and mildly elevated densities compared to sodium- and lithium-containing ones. At 25 °C, the potassium-prolinate solution demonstrated the highest viscosity (8.5 mPa⋅s), whereas K-glycinate exhibited the lowest viscosity (2.5 mPa⋅s). Additionally, potassium-based solutions consistently displayed the highest CO2 mass transfer coefficients, followed by sodium- and lithium-containing ones. The CO2 mass transfer coefficient was highest for potassium-prolinate (2.99 mmol m−2⋅s−1⋅kPa−1) with the lowest rate observed for potassium-β-alaninate (1.68 mmol m−2⋅s−1⋅kPa−1). Interestingly, the type of counter ion had minimal impact on the CO2 absorption capacity, with potassium-based solutions exhibiting only a slightly elevated capacity compared to sodium- and lithium-based solutions. Specifically, potassium-lysinate displayed the highest CO2 absorption capacity (0.7 mol CO2 /mol amine), while potassium-β-alaninate showed the lowest (0.65 mol CO2/mol amine). It should be noted that all lithium-based solutions of all amino acids formed precipitates during CO2 absorption. From a practical and operational perspective, these findings suggest that the potassium salt solution of amino acids would be the optimal choice for direct air capture applications due to their enhanced solubility and CO2 mass transfer rates compared to the corresponding sodium and lithium counter ion salt solutions.

Organohalogenochromism: Toward Colorimetric Detection of Volatile Organic Halogen Compounds

A significant hypsochromic or bathochromic shift of photoabsorption bands of dyes may be observed only in halogenated solvents. Such specific solvatochromism is termed organohalogenochromism (OHC), which has been recently recognized as a photophysical phenomenon. However, few studies have been carried out on the elucidation of OHC and thus there is a limited insight into the mechanism for expression of OHC, although the phenomenon not only is of a great scientific interest in photochemistry, photophysics, analytical chemistry, and synthetic organic chemistry but also has great potential for development of colorimetric detection technique for organohalogen compounds; this technique is expected to be facile operation and simple analysis with sufficient accuracy, high sensitivity, and fast response, and thus allows visualization and real‐time monitoring for toxic volatile organohalogen compounds (VOHCs). In this Concept, we first review OHC of dyes which have been reported so far. Second, the elucidation of OHC based on the interactions between dye and organohalogen molecules are discussed. In particular, we propose the explanation for a pronounced OHC of donor‐π‐acceptor‐type cationic dye from the viewpoint of halogen bond (XB) between halogenated solvents and counter anion of cationic dye. Moreover, an application of organohalogenochromic dyes to colorimetric sensors for VOHCs is presented.

Weak solvation effects and molecular-rich layers induced water-poor Helmholtz layers boost highly stable Zn anode

The advancement of aqueous Zn-based energy storage systems encounters major challenges due to the occurrence of side reactions and the growth of dendrites caused by the highly active nature of water in the aqueous electrolyte. Herein, a zwitterion additive named sulfonated amphoteric betaine (referred to as DMAPS) regulates the Zn2+ electrolyte environment through a weak solvation effect to promote highly stable Zn anodes. The inherently occurring anionic (-SO3-) and cationic (-NR4+) counterions in the DMAPS chain can be effectively separated under an external electric field to enable the creation of distinct ion migration pathways, thereby significantly enhancing the transportation of electrolyte ions. Moreover, DMAPS can be adsorbed onto the surface of Zn anode to form a H2O-poor Helmholtz layer, which can serve as a protective barrier to suppress corrosion of the Zn anode by free H2O and inhibits the formation of differential electric field to facilitate the directional deposition of Zn2+. In addition, density functional theory (DFT) and molecular dynamics (MD) further assisted in demonstrating the intrinsic mechanism of the reconstruction of the solvated sheath structure of Zn2+ by DMAPS. As a result, the Zn//Zn symmetric cell in ZnSO4+DMAPS solution can be cycled steadily for 2100 h at a current density of 1 mA cm-2 and 1 mAh cm-2. The assembled Zn ion hybrid capacitor with ZnSO4+DMAPS electrolyte was stably cycled for 20,000 cycles with 90% capacity retention at 5 A g-1.

A novel copper(II) complex with a salicylidene carbohydrazide ligand that promotes oxidative stress and apoptosis in triple negative breast cancer cells.

We report the synthesis, characterization, anti-cancer activity and mechanism of action of a novel water-soluble Cu(II) complex with salicylidene carbohydrazide as the ligand and o-phenanthroline as the co-ligand. The synthesized complex (1) was characterized by FT-IR, EPR, and electronic spectroscopy, as well as single crystal X-ray diffraction. This compound was found to be paramagnetic from EPR spectra and X-ray crystallography revealed that the molecule crystallized in an orthorhombic crystal system. The crystal lattice was asymmetric containing two distinct binuclear copper complexes containing the Schiff base as the major ligand, o-phenanthroline as a co-ligand, two nitrate anions, and two water molecules. The Cu(II) in the first site coordinated with the enolised ligand comprising enolate O-, phenolate O-, and the imine N and N,N from o-phen. The major part of this complex exists as Cu(II) coordinated with two H2O molecules at the second site with nitrate acting as the counter anion. However, a smaller portion of the complex exists where Cu(II) is coordinated with NO3- and H2O, and the remaining water molecule acts as lattice water. It was tested for DNA binding and cleavage properties which revealed that it binds in an intercalative mode to CT-DNA with Kb value of 1.25 × 104 M-1. Furthermore, cleavage studies reveal that the complex has potential for efficient DNA cleavage under both oxidative and hydrolytic conditions. It was able to enhance the rate of cleavage by 2.8 × 108 times. The complex shows good cytotoxicity to breast cancer monolayer (2D) as well as spheroid (3D) systems. The IC50 values for MDA-MB-231 and MCF-7 monolayer culture was calculated as 1.86 ± 0.17 μM and 2.22 ± 0.08 μM, respectively, and in (3D) spheroids of MDA-MB-231 cells, the IC50 value was calculated to be 1.51 ± 0.29 μM. It was observed that the complex outperformed cisplatin in both breast cancer cell lines. The cells treated with complex 1 underwent severe DNA damage, increased oxidative stress and cell cycle arrest which finally led to programmed cell death or apoptosis in triple negative breast cancer cells through an intrinsic pathway.

Enhancing performance and sustainability of lithium manganese oxide cathodes with a poly(ionic liquid) binder and ionic liquid electrolyte

Current battery production involves various energy intensive processes and the use of volatile, flammable and/or toxic chemicals. This study explores the potential for using a water-soluble and functional binder, poly(diallyldimethylammonium) (PDADMA) with diethyl phosphate (DEP) as a counter anion, for lithium manganese oxide (LMO) cathodes. By replacing the traditional polyvinylidene fluoride (PVDF) binder and its associated toxic N-methyl-2-pyrrolidone (NMP) solvent, PDADMA-DEP offers a more sustainable and cost-effective solution. Notably, PDADMA-DEP electrodes do not require high-temperature calendaring to achieve high performance unlike PVDF electrodes. X-ray Photoelectron Spectroscopy (XPS) indicated significant interactions between the binder and LMO that enhance stability and ion conduction. The PDADMA-DEP binder demonstrated excellent electrochemical rate capability up to 10C with the conventional organic liquid electrolyte (LP30), outperforming PVDF electrodes. The performance of both binders using a safer and non-volatile ionic liquid electrolyte, specifically 50 mol% LiFSI in N-trimethyl-N-propylammonium bis(fluorosulfonyl)imide, was also investigated to enhance the overall safety and environmental impact of the battery system. IL-based cells utilizing a PDADMA-DEP cathode binder demonstrated a 58 % capacity retention over 500 cycles at 0.5C when cycled at room temperature.

A Multielectron and High-Potential Spirobifluorene-Based Posolyte for Aqueous Redox Flow Batteries.

The rising energy demand driven by human activity has posed pressing challenges in embracing renewable energy, necessitating advances in energy storage technologies to maximize their utilization efficiency. Recent studies in aqueous organic redox flow batteries have focused primarily on the development of organic negative electrolytes, while the progress in organic positive electrolytes remains constrained by limitations in their redox potentials and effective electron concentrations. Herein, we report a spatially twisted chlorinated spirobifluorene ammonium salts (CSFAs), created through an unexpected green chlorination-protection pathway during the initial cycling in the flow battery cell, utilizing chloride ions from counterions in aqueous solution. The chlorinated, nonplanar spiral structure of CSFAs possesses a one-step four-electron transfer electrochemical property and offers exceptional resistance to nucleophilic attacks, exhibiting an unprecedented redox potential as high as 1.05 V (vs. SHE). A full redox flow battery based on CSFA-Cl (chloride ions as the counter ions) with 1.4 M electron concentration achieved an average coulombic efficiency exceeding 99.4 % and a capacity utilization reaching 95 % of the four-electron capacity for a stable cycling over 250 cycles (~22 days). The present work exemplifies the use of side reactions to develop new redox species, which can be extended to create more structurally versatile energy storage materials.

Synthesis and Structural Characterization of Carbazole-Tailored Luminescent Triarylmethyl Radical and its Stable Cation.

The development of novel luminescent radicals, characterized by their unique doublet emission, endows a significant challenge. In this study, we reported the synthesis of a luminescent neutral radical, BCzAnM-R, tailored by two carbazolyl groups and an anthryl group to achieve a nonalternant structure. It exhibited near-infrared emission with a peak at 1020 nm in toluene. Interestingly, its corresponding cation, BCzAnM-C, was synthesized through an unconventional SnCl2-mediated reduction-aromatization-oxidation reaction in one-pot and gram-scale. The cation demonstrated remarkable stability for up to weeks in ambient conditions and facilitated the silica-gel chromatography isolation as an organic salt with SnCl3-as the counter ion. The carbazolyl groups effectively modulate molecular structures, photophysical properties, and stabilities. Notably, BCzAnM-R represents the first luminescent triarylmethyl radical with two carbazolyl groups directly attached to the central carbon.

Adsorption behaviors and mechanisms of gold recovery from thiosulfate solution by ion exchange resin

The adsorption behaviors and mechanisms of gold from thiosulfate solution on strong-base anion exchange resin were systematically investigated. The comparison experiment of adsorption ability and selectivity for gold showed that gel Amberlite IRA-400 resin with Type I quaternary ammonium functional group had better adsorption performance. The increases of resin dosage, ammonia concentration and solution pH were favorable to gold adsorption, whereas the rises of cupric and thiosulfate concentrations were disadvantageous to gold loading. Microscopic characterization results indicated that gold was adsorbed in the form of [Au(S2O3)2]3– complex anion by exchanging with the counter ion Cl– in the functional group of the resin. Density functional theory calculation result manifested that gold adsorption was mainly depended on the hydrogen bond and van der Waals force generated between O atom in [Au(S2O3)2]3– and H atom in the quaternary ammonium functional group of the resin.

Encapsulating Azolates Within Cationic Metal-Organic Frameworks for High-Energy-Density Materials.

Despite the synthesis of numerous cationic metal-organic frameworks (CMOFs), their counter anions have been primarily limited to inorganic Cl-, NO3 -, ClO4 -, BF4 -, and Cr2O7 2-, which have weak coordination abilities. In this study, a series of new CMOFs is synthesized using azolates with strong coordination abilities as counter anions, which are exclusively employed as ligands for coordinating with metals. Owing to the unique nitrogen-rich composition of azolates, the CMOFs demonstrate significant potential as high-energy-density materials. Notably, CMOF(CuTNPO) has an exceptionally high heat of detonation of 7375kJ kg-1, surpassing even that of the state-of-art CL-20 (6536kJ kg-1). To further validate the advantages of employing azolates as counter anions, analogues with azolates serving as ligands are also synthesized. The comparison study indicates that encapsulating azolates within the cationic frameworks confers both high energy and safety properties. X-ray data and quantum calculations indicate that their enhanced performance stems from stronger H─bonds and π-π interactions. This study introduces new roles for azolates in MOFs and expands possibilities for structural diversity and potential applications of framework materials.

Mononuclear high-spin iron(III) phthalocyanines

2,9(or 10),16(or 17), 23(or 24)-Tetradecyloxycarbonylphthalocyaninatoiron, FeTDPc, and 2,3,9,10,16,17,23,24-octadecyloxycarbonylphthalocyaninatoiron, FeODPc, were synthesized and characterized. These compounds seem to be in trivalent iron high-spin state in solvents such as chloroform, dichloromethane, benzene, and chlorobenzene, although their counter anion could not be detected by elemental analyses. They react with strong bases such as pyridine and imidazoles to form their mono- and subsequently their di-base complexes with formation constant of >106 and < 200 dm3 mol−1, respectively, in dichloromethane at 20 °C. The resultant mono-adducts appear to be trivalent iron low-spin while the di-base adducts are bivalent iron low-spin state complexes. The addition of ca. 10–30 equivalent of tetrabutylammonium-chloride or -bromide (electrolyte) to the solution containing FeTDPc or FeODPc, causes their spin-state change from iron(III) high to low-spin state. In a solid power state, however, both FeTDPc and FeODPc exist as a mixture of high-spin iron(III)- and intermediate-spin iron(II) species. Strangely, when these compounds are dissolved in polystyrene, i.e. each molecules are isolated from each other, the signals originated from the iron(II) component disappear.

Asymmetric tridentate Schiff base ligand based mononuclear Zn(II) and Hg(II) complexes: Synthesis, structure, spectroscopic studies, thermal studies, and DFT calculation

Two novel mononuclear metal(II) complexes with an asymmetric tridentate Schiff base ligand, and azide/chloride anions, namely [ZnL(N3)2] (1) and [HgL(Cl)2] (2) (L = (pyridin-2yl)methylimino)-2-ethylpyridine), have been synthesized and structurally characterized by elemental analysis, single crystal X-ray crystallography, FT-IR, NMR, UV–vis electronic absorption spectroscopic analysis. The metal in both the complexes displays a pentacoordination environment realized by the tridentate Schiff base and counter anions. The coordination geometry of Zn in complex 1 is in between a trigonal bipyramidal and square pyramidal, whereas Hg in complex 2 shows a distorted square pyramidal. Theoretical DFT/TD-DFT calculation data performed using B3LYP functional with LanL2MB basis set, compared with values of experimental measurements, have shown a reasonable accord. The thermal stability of both complexes has been studied.

Preparation and Characterization of Antibacterial Polycarbonate (PC) Using Quaternary Fluoroalkyl Phosphonium Salts with Various Counter Anions

In order to find an optimal antibacterial agent for Polycarbonate (PC), five quaternary fluoroalkyl phosphonium salts (FAPS) with iodine anions (PPICF-13), tetrafluoroborate (FB-PPCF-13), trifluoromethanesulfonate (TFMS-PPCF-13), methanesulfonate (MS-PPCF-13), and p-toluenesulfonate (pTS-PPCF-13), each with a side chain of 13 fluorine atoms, were incorporated were incorporated into PC with a mass ratio of 2.5 wt.%. The influence of the counter anions on the rheological properties, mechanical properties, appearance and light transmittance, antibacterial activity and cytotoxicity of the antibacterial PCs were investigated. The results showed that all the FAPS could impart PC with above 90% of antibacterial degree. The melt flow rate of the PC was increased due to the plasticizing effect of FAPS. The incorporation of up to 2.5 wt.% FAPS had no negative influence on the flexural strength, flexural modulus and tensile strength of the PC, but reduced the impact strength of the PC to varying degrees, depending on the counter anion. All five of the FAPS influenced the appearance and light transmittance of PC, and the TFMS-PPCF-13, MS-PPCF-13 and pTS-PPCF-13 samples appeared to have less impact on these properties than PPICF-13 and FB-PPCF-13. All antibacterial PCs; except for the antibacterial PC containing PPICF-13, exhibited no cytotoxicity. Considering all the properties, the antibacterial PC containing TFMS-PPCF-13 showed the optimal comprehensive properties based on this research.